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App 2A of Rancho Seco PSAR, Smud Meteorological Investigation, Final Rept.Prepared for Bechtel Corp
	ML19329E002
Person / Time
Site:	Rancho Seco
Issue date:	09/01/1967
From:	Beesmer K, Tanya Smith; METEROLOGY RESEARCH, INC., SACRAMENTO MUNICIPAL UTILITY DISTRICT
To:	;
Shared Package
ML19329E003	List: ML19329E002; ML19329E004;
References
	MRI-67-FR-638, NUDOCS 8004090547
	Download: ML19329E002 (70)
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FINAL REPORT SACRAMENTO MUNICIPAL UTILITY ' DISTRICT (SMUD) METEOROLOGICAL INVESTIGATION i Prepared for Bechtel Corporation 4620 Seville Avenue Vernon, California l By T. B. Smith K. M. Beesmer Meteorology Research, Inc. 464 West Woodbury Road Altadena, California 91001 071 1 September 1967 O l MRI67 FR-638 ,,~w, a, ,---,-,,r,a-n.,,,,--,--,,,r-sn,-m.--,,,-.- ,,, +. -. -- - - -. - - -,,g-,n--mm, m.-.nw cw.

SUMMARY

~ 1 The Sacramento Municipal Utilities District (SMUD) has pro-posed construction of a nuclear power plant near Clay, California about 23 miles southeast of Sacramento and 27 miles north-northeast of Stockton. This report is a study of the meteorology and climatology of the proposed site, Rancho Seco, based upon lonh-term data available primarily from Stockton, Sacramento and Mather AFB. In order to determine the applicability of these data to Rancho Seco, meteorological measurements were made at Rancho Seco for a six-weeks period and compared with the other sites for the same period. The six-weeks study at Rancho Seco included the measurement of wind speed and horizontal and vertical wind direction a: 53 feet above the ground, the temperature at 6 feet and the temper-ature difference between 6 and 53 feet, and the humidity at the 6-foot level. In addition to continuous records of these param-eters during the period, two field trials were held to define I ( ) the wind trajectory and associated meteorological conditions throughout the Stockton, Sacramento, Rancho Seco area. These trials included pibals (balloon wind measurements) within 2000-3000 feet of the ground at several sites within 10-15 miles of Rancho Seco for midday and nighttime conditions. The climate of Rancho Seco is generally that of the Great Central Valley of California. Summers are hot and cloudless while winters are mild. The rainy season occ'urs between October and May and heavy radiational fog often exists in December and January. Tornadoes and thunderstorms are infrequent. Tornadoes occurred only 22 times in California between 1953 and 1962. Thunderstorms occurred an average of three times each year at Stockton and five times at Sacramento. Similar occurrences would be expected at Rancho Seco. The winds at Pancho Seco have two major dynamic controls - the thermally-driven " marine" flow in the summer and the synoptic pressure gradient systems of mid-winter. Spring and fall are .33 largely controlled by thermal gradients. 012 i

The Central Valley warms greatly during the day resulting in a marked thermal contrast between the Valley and the air over the Pacific. The Coast Range separates the mariae air from warm valley air except for a gap through the range formed by Sacramento-San Joaquin Rivers. The heavy marine air flows through this gap and splits into a northerly flow into the San Joaquin Valley and a southerly flow into the Sacramento Valley. The divergence zone between the two flows usually lies between Stockton and Sacramento near Rancho Seco. The diver-gence zone is usually north of Rancho Seco during the day re-sulting in west to northwest winds. The cool marine air usually arrives around 1800 PST. As the air in the Valley cools, the flow decreases and calms may set in. If the drainage from the Sierra Nevada is sufficient, the winds may shift to south-easterly and again increase in speed at Rancho Seco. During the hottest mid-summer months, the light westerly winds may persist all night. During the winter, the synoptic gradients prevail much of the time and the wind trajectories over the Sacramento-Stockton-Rancho Seco area are reasonably uniform. Sacramento and Stockton extreme wind speeds have been in good agreement for the periods of record. The maximum observed at Sacramento (longest period of record) has been 70 mph. Since these winds are associated with synoptic gradients, Rancho Seco can be expected to be similar. No precipitation data are available for the Rancho Seco site. Since the precipitation is associated with synoptic scale gradi-ents, Stockton, Sacramento and Rancho Seco should have similar characteristics. The yearly normal rainfall for Sacramento is 16.29 inches and 13.37 inches for Stockton with maximum 24-hour amounts of 5.59 and 3.01 inches respectively. At Sacramento precipitation occurs with south to southeasterly winds 65 per cent of the time. Frozen precipitation is extremely rare and of very small quantities. 073 % ~ ii

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The surface temperatures at Rancho Seco were found to agree

\\ on the average with Stockton and Sacramento. Temperature in-versions at the ground can be expected every night during the summer, usually modified by the marine airflow in the evening which results in the top of the inversion being at several hundreds of feet. During the winter, shallow (a few hundred feet) but intense surface inversions can be expected at night during light wind conditions. When they are associated with fog, they may persist throughout the day, occasionally for several days at a time. On an average, relative humidities at Stockton, Sacramento and Rancho Seco were found to agree well with each other. From an analysis of long-term climatological statistics from Sacramento and Stockton, an F condition with a wind speed of 2.4 m/sec is recommended for use in the zero to two-hour dosage model. ' L)/ I Turbulence measurements made at the site were used to calculate cloud widths (cy) for comparison with existing diffu-sion classification systems. The Fuquay method of using (o u) e to estimate cloud widths was used to calculate expected values of oy for releases of 10 minutes and one-hour duration. It was found that the cloud widths calculated from on-site obser-vations agreed well with the Pasquill system for categories A through E. For categories F and G the observed cloud widths for one-hour releases were considerably larger due to the mean-dering of the wind under these stable conditions. It is recommended that the Pasquill system be used for the Rancho Seco site but with new F and G curves to provide more realistic cloud widths under stable conditions. A slight modification in the oz curves is also recommended to adapt the calculations to the occurrence of an average nocturnal inversion base height of 200 m as determined from Oakland data. 074 ' h(-] m iii 1

TABLE OF CONTENTS Page '}

SUMMARY

i I. INTRODUCTION 1 II. SCOPE 2 III. DATA SOURCES 3 A. Off-Site 3 B. On-Site 4 IV. SITE CHARACTERISTICS 8 A. Terrain 8 B. Reservoirs 8 V. SITE CLIMATOLOGY 9 A. General 9 B. Winds 10 1. Wind Roses and Trajectories 10 2. Extremes 18 3. Direction with Precipitation 25 4. Persistence 26 C. Temperature 29 1. Surface 29 2. Inversions 32 D. Precipitation 35 E. Humidity 38 VI. DIFFUSION MODELS 42 A. General 42 B. Estimation of Diffusion Parameters 42 1. Pasquill Method 42 2. Markee Method 43 C. Turbulence Measurements 43 D. D,evelopment of Climatological Statistics 45 E. Rancho Seco Site Study 54 VII. CONCLUSIONS 61 e) VIII. REFERENCES 63 iv 075 ?. :

(("} LIST OF ILLUSTRATIONS \\-/ Page Fig. 1. PROPOSED SITE AREA MAP 5 2. METEOROLOGICAL INSTRUMENTATION 6 3. METEOROLOGICAL ELECTRONICS AND RECORDERS 6 4. WIND ROSES 11 5. YEARLY WIND ROSES 13 6. MOST FREQUENT WIND DIRECTIONS - 0300, 0600 PST 14 7. MOST FREQUENT WIND DIRECTIONS - 1500, 1800 PST 15 8. WIND TRAJECTORY - Afternoon 13 June 1967 16 9. WIND TRAJECTORY - Afternoon 14 June 1967 17 10. WIND TRAJECTORY - Night 13-14 June 1967 19 11. WIND ROSES, May 1967 - 0000, 0300, 0600 PST 20 12. WIND ROSES, May 1967 - 0900, 1200, 1500 PST 21 13. WIND ROSES, May 1967 - 1800, 2100 PST, Month 22 14. WIND ROSES, 1 June-10 July, 0000, 0300, 0600, 23 0900 PST, Rancho Seco 15. WIND ROSES, 1 June-10 July, 1200, 1500, 1800, 24 2100 PST, Rancho Seco 16. STOCKTON WIND PERSISTENCE - Winter 27 17. STOCKTON WIND PERSISTENCE - Summer 28 1 18. PERSISTENCE WIND ROSE 30 19 ANNUAL VARIATION IN INVERSION BASE HEIGHT 33 20. PERSISTENCE OF PRECIPITATION - Sacramento 37 21. PASQUILL o CURVES MODIFIED FOR HOURLY RELEASE 57 y 22. PASQUILL o CURVES MODIFIED FOR 200 m INVERSION 59 z V

LIST OF TABLES Table I. MEAN NUMBER OF DAYS OF THUNDERSTORMS 10 (Stockton and Sacramento) II. HIGHEST ONE-MINUTE AVERAGE WIND SPEEDS 25 (Sacramento) ~ III. OCCURRENCE OF RAIN VERSUS DIRECTION (%) 26 (Sacramento) IV. STOCKTON TMPERATURE NORMALS AND EXTREMES 29 SACRAMENTO TEMPERATURE NORMALS AND EXTREMES 31 V. AVERAGE TEMPERATURE EXTREMES AND MEANS (1967) 31 VI. 0AKLAND, CALIFORNIA INVERSIONS 34 VII. PRECIPITATION 35 VIII. PRECIPITATION INTENSITY 36 ) IX. TEMPERATURE AND WIND SPEED - RELATIVE HUMIDITY 39 OCCURRENCES X. AVERAGE RELATIVE HUMIDITY 40 XI. DIFFUSION CLASSIFICATION SYSTEM FOR 46 RANCHO SECO SITE XII. PERCEN".. AGE FREQUENCIES OF DIFFUSION CATEGORIES 47 XIII. SACRAMENTO STABILITY DATA 48 XIV. STOCKTON STABILITY DATA 51 XV. COMPARISON OF FREQUENCY OF OCCURRENCE OF 54 DIFFUSION CATEGORIES XVI. COMPARISON OF DIFFUSION CALCULATION SYSTEMS 55. XVII. RANCHO SECO AVERAGE CONDITIONS 56 Vi 077

I. INTRODUCTION The Sacramento Municipal Utilities District (SMUD) has proposed construction of a nuclear power plant at a site about two miles east of Clay. The proposed site (Rancho Seco) is about 23 miles southeast of Sacramento and 27 miles north-northeast of Stockton in the lower Sacramento Valley of Cali-fornia. This report includes the results of a six-weeks meteorological study at the proposed site and a comparison of the meteorology of that site with available meteorological data from nearby loca-tions. Having established this comparison, the long-term data for the nearby locations have been processed and utilized in developing climatological descriptions of the site. These descriptions have included the dispersion and wind trajectory characteristics of the site. 078 1

II. SCOPE s O' The six-weeks on-site study included the provision and installation by MRI and operation by SMUD personnel of wind and temperature measuring equipment at the site. The recorded meas-urements included the horizontal and vertical wind direction and wind speed at the 53-foot level and the temperature at the 6-foot level with the temperature difference between the 6 and 53-foot levels. In addition, a hygrothermograph recording temperature and humidity was operated within a thermoscreen at the bottom level. All data were removed from the recorders and returned to MRI weekly for reduction and analysis. In addition, two field programs were carried out to obtain information on the air-flow trajectories within 10-15 miles of the proposed site. These consisted primarily of a series of pibal (pilot balloon) observations of the winds within the lower 2000-3000 feet taken at about a dozen locations around the site (see Site Climatology). A set of these observations was taken for midday and nighttime conditions on each of two days for each h) of the field programs. Surface temperature and wet-bulb temper-ature were measured concurrently at each location. Aircraft tem-perature soundings were made occasionally over the Rancho Seco site during the pibal observation period. The first of the two field programs (20-23 April) occurred during a period of thunder-storm and rain shower activity associated with a large-scale synoptic flow pattern. The second field program (12 14 June) was held during a more typical spring through fall mesoscale flow pattern to be described in the section on Site Climatology. Meteorological data from nearby locations were obtained during the on-site program for comparison with the Rancho Seco site data. Long-term meteorological data from the nearby loca-tions were obtained and processed to develop the climatology of the site utilizing comparative results of the six-weeks study. The availability of these and long-term climatological data are listed in more detail in the following section. 079 1 1 l 2 1 l l

l III. DATA SOURCES Os A. Off-Site -l Meteorological data are available for past years from government weather observation stations. These data gener-ally include hourly observations of wind direction and speed, temperature, dew point, cloud conditions, precipitation, and weather. Various climatological summaries are also avail-able for some sites. Data utilized in this report include: Sacramento (USWB at Municipal Airport) 1. Hourly Observations, 1963, 1965 15 April-15 June 1967 (microfilm or copy) 2. Hourly Observations, January 1949-December 1955 (magnetic tape) 3. Summary of Hourly Observations,1951-1960 (printed material) 4 Local Climatological Data,1965, 1966 (printed material) including normals, means and extremes for the period of record. Stockton 1. Hourly Observations, 1963, 1965 15 April-15 June 1967 (microfilm or copy) 2. Hourly Observations, January 1949-December 1954 (magnetic tape) 3 Local Climatological Data, 1965, 1966 (printed material) including normals, means and extremes for the period of record. Mather AFB 1. Hourly Observations, 1963, 1965 l 15 April-15 June 1967 (microfilm or copy) l 2. Uniform Summary of Surface Weather Observations - l (g Part C (Flying Weather Wind Roses) 1952-1961, '\\J Part E (Psychrometric Summary) 1952-1961. 080 3 i

N In addition to the standard weather observation stations, wind data have been collected at several sites between Sacramento and Stockton for various periods in conjunction with agricultural studies being made by H. B. Schultz of the University of California at Davis. These include: 1. Terminous - April through September for 1958 through ~ 1963 2. "Galt" (several miles from the town) - April through present 1967 3. Walnut Creek - TV Tower i The "Galt" data appear to be inconsistent and were not utilized. Unfortunately, the Walnut Creek data are not yet available. It is hoped that data from these sites will be available for later usage. All data sites are shown on Fig. 1. It should be noted that no data cources have been found east of the proposed } site. B. On-Site The primary source of data from the proposed site is the meteorological instrumentation operated on site from 22 April through 15 June 1967 with a more limited system oper-ating through the present time. The initial meteorological measurements included: 1. MRI VectorVane measuring and recording continuously (analog) the horizontal and vertical wind direction and speed at the top of a teleph6ne pole (53 feet). 2. Fast response (thermistor) temperature measuring system with a cycled (5 minutes each) recording of the temperature at the 6-foot level and the differ-ence in temperature between the 6 and 53-foot lavels. 3. Hygrothermograph recording temperature and humidity 4 i hl near the base of the pole (in thermoscreen) - see Figs. 2 and 3. 08,i u l

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i l I About 15 June, the wind and temperature systems were s/ replaced with a unit at the top of the pole measuring wind l direction and speed. The period from 15 June to 10 July has been reduced and is utilized in the report. The hygrothermo-graph remains at the surface location. During the field programs the instrumentation system above was supplemented with pibal observations at the site and within 10-15 miles of the site to determine the wind trajectories in the area. These data were reduced at MRI to wind directions and speeds at given levels based upon the standard ascent rate of the balloons. At the time of the balloon release, temperature and dew point readings were taken. In addition, temperature soundings were taken by a light aircraft over Rancho Seco to define the stability con-ditions. 5 C A 084 7 \\

d IV. SITE CHARACTERISTICS h A. Terrain The San Joaquin-Sacramento Valleys are oriented in a northwest-southeast direction between the Sierra Nevada to the east and the Coast Range along the Pacific Ocean to the west. Sacramento and Stockton are east of the gap in the Coast Range associated with the Sacramento and San Joaquin Rivers. The Sacramento and Stockton Airports are at 17 and 22 feet MSL, respectively. The terrain rises steadily to 200 feet at the proposed Rancho Seco site. East of the site the land becomes more rolling, rising to an elevation of 606 feet at 7 miles and increasing in ele-vation thereafter as one approaches the foothills of the Sierra Nevada which rise to over 10,000 feet 65 miles east of Rancho Seco. The Rancho Seco site is located in an area of flat to lightly rolling terrain. The land is used primarily for agriculture and generally lacks tree cover except in isolated ) patches along the streams. B. Reservoirs The closest reservoir at present is the Camanche Reservoir about 10 miles southeast of Ranch Seco. Two additional reservoirs have been recommended in the " Southeast Area Plan" by the Sacramento County Planning Department and adopted by the Sacramento County Board of Supervisors. One of these is about 4 miles southeast of the site and the other 8 miles to the northwest. Both new dams would be used for irrigation and flood control. Ob ~ 8

V. SITE CLIMATOLOGY A. General The climatology of the Rancho Seco site is cimilar to other locations in the Great Central Valley of California. Cloudless skies prevail during the summer and much of the spring and fall. The rainy season is in the winter (December through March) when more than two-thirds of the annual rainfall can be expected. Heavy radiational fogs occur in mid-winter, primarily in December and January and may last for several days. The most important controlling geographical influence on the climate results from the mountains which surround the Valley to the west, north and east. During the winter, storms which pass through the area are moderated by the mountains which collect much of the precipitation. The rains that occur in the Valley are usually accompanied by south to southeast winds. The cold north and northwest winds pass Os over mountains to the north where the air is warmed dynami-cally by descent into the Valley resulting in comparatively warm, dry winds. A similar condition occurs infrequently in the summer when a steep northerly pressure gradient develops, producing a pronounced heat wave. In the summer, the synoptic pressure patterns weaken and j a thermal gradient develops between the heated Valley and cool marine air along the Pacific Ocean.- The Coast Range i blocks the marine air except at the break in the range asso-J ciated with the San Joaquin-Sacramento River. The resulting westerly flow of marine air enters the Valley and splits into a southerly flow into the Sacramento Valley and a northerly flow into the San Joaquin Valley. The resulting divergence zone is usually located between Stockton and Sacramento. The effect of this divergence zone upon the climate at Rancho Seco is discussed in detail in the following sections. 1 O{~% 08h ~ + - - - - in 1 u, ~ .,. -.. _ - ~

The possibility of severe storms in the area can be I limited to tornadoes and thunderstorms. According to the U. S. Weather Bureau, 22 tornadoes occurred in California during the 1953-1962 period. Using the methods described by Thom (1963), the probability of occurrence of a tornado ~ in the state of California can be calculated to be 4 x 10 per year. The mean recurrent interval of a tornado would be 23,200 years. Thunderstorms occur infrequently in the area. The mean number of days during which thunderstorms occurred over an 18-year inturval for Sacramento and a 19-year interval for Stockton are listed in the following table. The + indicates less than one-half day. TABLE I MEAN NUMBER OF DAYS OF THUNDERSTORMS Stockton Sacramento Stockton Sacramento Jan + + July + + s 1 Feb + + Aug + + Mar + 1 Sept 1 1 Apr + 1 Oct + + May + 1 Nov + + June + + Dec + + Year 3 5 B. Winds 1. Wind Roses and Trajectories The wind roses for January, April, July and October for Mather AFB, Sacramento and Stockton are included in Fig. 4 .The January roses show a general similarity between the three sites with a slightly larger occurrence gg of westerly winds at Stockton. For the other three months, Stockton shows a dominant west to northwest flow with the other two sites showing south to southwest. O> 10 087

O Mather AFB Sacramento Stockton 1952-1961 1951-1960 1949-1954 Jan 37 17 50 April O n July 7 30 \\ ?' P????? ? "F' 9-12 19-24 4-7 13-18 25-33 mph % Frequency of occurrence of wind 5,3 mph in circle Fig. 4. WIND ROSES O80 11

q The dominance of the synoptic scale pressure pattern in winter results in a general agreement between the three sites during this season. Heating at midday may result in some thermal gradient between the ocean air and the Valley but the average maximum of 53*F at Sacra-mento in January is not much more than the ocean tem-perature, allowing the stronger winter synoptic pressure gradients to prevail. In summer, the synoptic scale pressure gradients weaken and the thermal gradient increases. The resulting flow of air through the break in the Coast Range at the Sacramento-San Joaquin River pours into the Valley from the west, diverging into a northwest flow into the San Joaquin Valley and a southeast flow into the Sacramento Valley. The southwest flow at Sacramento and west to north-west flow at Stockton are the dominant features on the T} yearly wind roses presented in Fig. 5. The southeast flow seen in January at both sites is also discernible. The Rancho Seco site lies near the divergence zone which is usually centered to the north of the site in mid-afternoon and to the south during the nighttime hours. The resulting wind trajectories can be clearly seen in Figs. 6 and 7 which are streamlines of the most frequent wind directions for 0300 and 0600 PST and for 1500 and 1800 PST, respectively, for the month of May 1967. These trajectories will vary from day to day. The wind direction for the lowest level (0-480 foot average direction) of the pibals taken during the June on-site study, along with some surface winds, were plotted as arrows in Figs. 8 and 9. The wind streamlines based on those arrows were then drawn and are presented in the figures. These trajectories illustrate some of the variations possible due to the movement of the location ) 12 08)

l i l i 4 i l i Stockton i j (6 years) { i 1 i i 16 4 1 4 ' O Sacramento (7 years) i 4 i o 10 20 30 40 50 60 70 so 90 100# I I I I I I I I I I I 1 % frequency of winds <0.5 mph in circle 090 ] Fig. 5. YEARLY WIND ROSES !O 1 13

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Afternoon 13 June 1967 Average wind 0-480 ft i Surface wind Time mph 'E" _q N Mather AFB t 4 1247, y Sacrampn 3 1223 Airp&rt 7 6 1312 s 12m 6 1347 1147 60,6' 9 Q ancho Seco N7x C1 is I409 \\8 1 1540 C che Res. 9 8A.\\ 1428 11 M 7 i 0 1 2 3 4 5 St. Miles x Pibal Site Stockton Road Fig. 8. WIND TRAJECTORY i I 16 .,n 1

fC Afternoon 14 June 1967 Average wind 0-48C ft 'l Surface wind Time - mph 1600 -t- - + 6 Mather AFB .,_ L*, Sacramento 1253 Airport e i 5 1647 1313 14 I 1330 ( 1740 o f-m' Seco 1610 \\ 1352 ia che Res. s b 1 l412 q 3, 1518 1442 Is ~ I 0 1 2 3 4 5 St. Miles Pibal Si.te 094 Stockton l x Road Fig. 9. WIND TRAJECTORY 17 l

of the divergence zone. The trajectory in Fig. 10 for the night of 13-14 June 1967 is almost a duplicate of Fig. 6. The diurnal variations of the wind directions at Rancho Seco and their rel'ationship with Stockton, Sacra-mento and Mather AFB during May 1967 can be seen in the wind roses in Figs. 11, 12 and 13. During the daytime hours (0900-1800), Stockton and Rancho Seco are similar but Rancho Seco is more nearly represented by Sacramento at night, particularly at 0000 and 0300. The westerly flow persisted at Stockton during the entire day for this particular month which was warmer than normal. Mather appears to have more southeasterly flow at night and more calms during the day. Wind data were reduced for Rancho Seco through 10 July to determine if the sequence of the variation of the wind direction observed during May persisted into .\\ the hot summer months. The three-hourly wind roses for j 1 June through 10 July are shown in Figs. 14 and 15. Two features stand out. First, the west-northwest afternoon flow became dominant during the first 10 days of July. Indeed, the westerly flow appears to have become evident during some of the nights. The second feature is the lack of calms during the daytime hours from 0900-1800 but their increase at night. The data suggest that during the summer heating months, the westerly flow is strong enough and consistent enough to generate substan-tial airflow each day. 2. Extremes The fastest one-minute average wind (mph) for Sacra-mento for 18 years is presented in Table II. The data are from the " Annual Summary of Comparative Data, 1966" of the " Local Climatological Data" for Sacramento. The Stockton data are not available for a comparatively long period. 28 ~ 095 l

Night 13-14 June 1967 Average wind 0 1480 ft Surface wind _ Time i, 4 \\i2300 4 4 i M ther '3 2348 9 Sacramento 1 de 3 gg35 Airport 7 2328 6 5 co3e ) 2x 7 0I05 2308 6 \\ 1929 M'd ho S co Clay 'O 7 12 0133 se \\ C anche Res. s1 No i ~ / t i N 3 n s O I 2 3 4 5 St. Miles Stockton x Pibal Site ^ Road Fig. 10. WIND TRAJECTORY 19 i

Rancho Seco Stockton Sacramento Mather A.F.B. 0000 PST 26 16 - 55 37 0300 17 23 55 55 N 0600 34 19 45 68 s d io do $o do 50 do 'lo do do 15 0 %. 't frequency of Winds 5 3 moh in Circle flay 1967 CD Pir. 11 WI!!D ROSES NI 9 9

.m 0 O O' Rancho Seco Stockton Sacramento Mather A.F.B. 0900 PST 18 22 42 4 i I j 1200 9 7 13 32 / U i 1500 0 10 32 i { O 10 20 30 40 50 60 70 00 90 100 % % Frequency of Winds 5 3 mph. in Circle g 1 Co May 1967 F i p.. 12 WIND ROSES e

Rancho Seco Stockton Sacramento Mather A.F.B. A 1800 PST 6 23 2100 21 3 6 45 N y Month 9 26 41 / o 40 20 30 40 50 60 m 80 90 100 % % Freauencv of Winds $ 3 mph. in circle May 1967 ca Pip. 13 WIND ROSES eW 9 9

1 Rancho Seco i l-15 June 15-30 June 1-10 July 0000 PST 29 36 0300 34 40 i i 44 0600 39 0 0900 100 o 10 20 30 40 50 60 70 eo 90 10 0 % f % Frecuency of Winds < 3 mph. in Circle Fig. 14. WIND ROSES 23

Pancho Seco 1-15 June 15-30 June 1-10 July ~ 1200 PST 7 0 N 1500 0 0 G) 1800 14 ,o O 24 2100 b ido% 101 20 lo 2o b 20 b b 7o e' o % Frequency of Winds 5 3 mph. in Circle Fi g.15 WIND ROSES 24

b'V TABLE II HIGHEST ONE-MINUTE AVERAGE WIND SPEEDS Month Direction Speed Year Jan SE 60 mph 1954 Feb SE 51 1959 Mar S 66 1952 Apr SW 45 1955 May S 35 1957 June SW 47 1950 July SW 36 1956 Aug SW 38 1954 Sept NW 42 1965 Oct SE 68 1950 Nov SE 70 1953 Dec SE 70 1952 ( In 1965, the highest speed at Stockton was 44 mph from SSE and 42 mph from NW for Sacramento. In 1966 the high for Stockton was 39 mph from the N and Sacra-mento was 36 mph from the SW. While these highs occurred on different days at the two sites, overall speed agree-ment is good but directions may differ somewhat. Similar speeds would be expected for Rancho Seco. 3. Direction with Precipitation J The direction of the wind which may be expected dur-i ing precipitation is of interest for the problem of particle washout. The frequency of occurrence (per cent) of rain versus wind direction at Sacramento for 1963 is presented in Table III. A + indicates less than one-half of one per cent. l 102 25

TABLE III k) OCCURRENCE OF RAIN VERSUS DIRECTION (%) Direction N NNE NE ENE E ESE SE SSE Per Cent 3 1 + + 1 1 15 31 Direction S SSW SW WSW W WNW NW NNW Calm Per Cent 19 7 7 2 W l 1 0 9 Note that the rain occurs with a wind direction be-tween south and southeast 65 per cent of the time. A similar result would be expected at Rancho Seco. 4 Persistence Wind persistences for Stockton for the winter (Janu-ary-March) and summer (July-September) are presented in Figs. 16 and 17. The persistence has been determined for a one-sector (20*) and three-sector (60*) range of direc-tion fluctuation by direction quadrants. The data in Figs. 16 and 17 show the probability of the wind contin-uing in the same sector for a successive number of hours ) after the initial establishment of the sector direction. Wind speeds of less than 3 mph were considered a discon-tinuity and counted as calm. Since calms are considered to have no direction, calm was not broken into quadrants and is plotted on the one-sector graph. Lines were drawn to observed points only. The meaning of the curves can be best explained by an example. During the summer, once a wind has been ob-served from a W to NNW direction inclusive, it will per-sist within a 20 sector for about 7 hours and within a 60* sector for about 25 hours for two per cent of the expected cases. An average probability of wind direction persistence, applicable to a two-hour model and weighted according to frequency of winds from the four quadrants, was found to be 47 per cent for one sector (20*) and 69 per cent for three sectors (60 ). ) A wind rose showing the maximum duration of wind per-sistence recorded at Stockton from various directions. 26

-7 s g' (] 8 u ,E-SSE 3 S / W-NNW ^ f a 2 $ k / O O .c M / w o / S,WSW 2 c e f M / / / O / / / /N-ENE H s' I /'/ / y i / / u z o ' / / ,5 U j // / m / / m ~ f /./ / E ~ a. n / [ f c ,/ z e I H 3 g, ./ a l i ( 1 vo z sk o e< e 8 mz ex 8 O c o e e m m 3 8 e o ed m m in /_- E-SSE_. b '3 ac4 L no k O f.a O x v m. oe o-M S-WSW O m / e

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['[1, is shown in Fig. 18, together with corresponding sta-s bility categories. The period of data record used for Stockton was 1949-1954 C. Temperature 1. Surface The normals, means and extremes of temperature for Sacramento and Stockton are presented in Table IV. All temperatures are in degrees Fahrenheit. The normals are based upon data for the 1931-1960 period with the extremes based upon six years of data at Sacramento and seven years at Stockton. The data are from the " Annual Summary with Comparative Data, 1966 of Local Climatolog-ical Data" published by ESSA for each location. TABLE IV STOCKTON TEMPERATURE NORMALS AND EXTREMES N Normals Extreme Daily Daily Month Maximum Minimum Monthly Highest Lowest Jan 52.4 37.0 44.7 65 19 Feb 58.2 39.7 49.0 73 26 Mar 65.0 42.3 53.7 87 29 Apr 72.8 46.5 59.7 93 32 May 80.6 51.7 66.2 100 38 June 88.6 56.9 72.8 111 45 July 95.4 60.9 78.2 113 52 Aug 93.1 59.3 76.2 107 52 Sept 88.6 56.7 72.7 101 45 Oct 77.7 50.2 64.0 98 36 Nov 64.6 41.3 53.0 84 26 Dec 53.9 37.9 45.9 71 21 Year 74.2 48.4 61.3 113 19 29

\\

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M G S s S NJ % 'a,k [ #e ' [ c, ,, N b8 q 0, 6e 3 Dlsisng y) Y,, 3s h 9,' x ( f 10 gg, } S 843 \\ (g)(g)gn 30%,(l) 3c-o, 2lc, sr / ( b).% \\ T 9,30. er O s @' 4 g) ,,p. ?- 3,. *" ' @ 3+% 4 p 9 P g Q 4 8 g8' 5 O ~ Gj o 9 04m I ms (l) IS-9. 218, 120, 12r, 42G Fig. 18. PERSISTENCE WIND ROSE 107

SACRAMENTO TEMPERATURE NORMALS AND EXTREMES Sg) Normals Extremes Daily D'aily Month Maximum Minimum Monthly Highest Lowest Jan 53.2 37.2 45.2 67 23 Feb 58.6 39.8 49.2 76 28 Mar 64.8 42.0 53.4 86 28 Apr 71.4 45.3 58.4 91 34 May 78.2 49.7 64.0 99 37 June 86.5 54.4 70.5 115 43 July 93.4 57.4 75.4 113 50 Aug 91.9 56.3 74.1 107 49 Sept 88.2 55.0 71.6 104 43 Oct 77.6 49.4 63.5 99 38 Nov 64.2 41.6 52.9 87 26 Dec 54.6 38.1 46.4 66 24 Year 73.6 47.2 60.4 115 23 [ Maximum and minimum temperatures were compiled for Stockton, Sacramento and Rancho Seco for the six-weeks field period. The average maximum, minimum and mean for each month or portion available are included in Table V. TABLE V AVERAGE TEMPERATURE EXTREMES AND MEANS (1967) 21-30 Apr May 1-11 June All Stockton-Maximum 60.4 F 81.0 75.3 75.8 Minimum 41.8 51.4 51.4 49.5 Mean 51.1 66.2 63.3 62.7 Sacramento-Maximum 60.5 80.9 74.3 75.6 Minimum 41.4 49.5 50.6 48.2 Mean 51.0 65,2 62.5 61.9 Rancho Seco-Maximum 58.3 79.9 73.5 74.4 Minimum 40.9 49.9 48.4 47.9 Mean 49.6 64.9 60.9 61.1 Ih3 31

The above data indicate general agreement in temperature h for the three sites with a tendency for Rancho Seco to be slightly cooler than the others. Differences in thermometer exposure and calibration could account for most of the small variations observed. 2. Inversions Inversions occur in the Great Central Valley as a result = of cold air advection near the ground or radiational cooling of the earth causing a cooling of the air near the ground. Radiational cooling will occur at night when there are no low clouds. Both types will occur at Rancho Seco with the advection type usually associated with the westerly flow bringing in cool air which originated over the Pacific Ocean. The frequency of occurrence (per cent) of the height of the inversion base at Oakland within various altitude cate-gories is listed in Table VI. The percentage is that por-3 tion of the soundings taken within the five-year interval l I) which fall within the indicated categories. As an example, at 0400 PST in April, 41 per cent of the soundings had an inversion at the surface, none between 1 and 500 feet, two between 501 and 1000 feet and 18 per cent had no inversions under 10,000 feet. The annual variation in inversion base height for the nighttime hours is shown in Fig. 18. During the six-weeks study, a surface inversion between 6 and 53 feet occurred every night having usable data (47 nights between 21 April and 15 June). The period of tran-sition between the normal lapse rate of daytime to the nighttime inversion was around 0600 and 1800. The average temperature difference for the inversion period was: 109 2100 PST 2.0 F 0000 2.9 0300 3.1 On 14 June during the on-site study, several aircraft hj soundings were made in the afternoon and early evening. N'ormal lapse to 3000 feet was observed at 1730, with an 32 u

O ~ t f 1900 PST --- 0400 PST 0700 PST 2000 ~ \\ / \\. /N. / /A \\, / \\, A c 1500 .2 .f / s g, \\, f s \\ a jj t b--, \\ ,I ~\\ 'I ( 1000 \\ j s. ee 'S _ _p _ _ Annual Average Height /f .N 800 ft. above Oakland \\s %. 500 \\, \\K 600 ft. above Site f e pf E /,/ \\, ' s ' / o/ / s y ~~. J F M M J S O N D Months (Oakland - nighttime hours) Fig.19. ANNUAL VARIATION IN INVERSION BASE HEIGHT 0 33 - - - - -, - - - -, - -. _ _ _ - _ _ _ _+ -a -a m

TABLE VI OAKLAND, CALIFORNIA INVERSIONS Height of Inversion Base 501-None under Month Time 0 (Sfc) 1-500 ft, 1000 ft 10,000 ft Jan 0400 76 1 1 14 % ~ 1600 7 6 5 32 Feb 0400 50 1 1 29 1600 1 0 3 60 Mar 0400 45 5 0 22 1600 0 3 4 48 Apr 0400 41 0 2 18 1600 0 17 7 28 May 0400 26 2 2 10 1600 0 10 10 23 ] June 0400 26 27 8 1 1600 0 29 19 9 July 0400 18 3 10 0 1600 3 36 25 3 Aug 0400 21 5 12 0 1600 2 30 31 5 Sept 0400 35 5 8 7 1600 2 27 17 14 Oct 0400 52 5 5 10 1600 5 17 11 24 Nov 0400 64 3 4 8 1600 5 5 10 34 Dec 0400 66 18 2 5 1600 11 7 10 17 111 34

'( inversion appearing based at 600 feet on the 1900 sounding and on the surface at 2030. On-site reports indicate a noticeable decrease in visibility and temperature about 1800, probably associated with the arrival of the sea air in the westerly flow and probably accounting for the 600-foot inversion at 1900. The top of the inversion on the 14th was about 1000 feet. If this persisted, the maximum temperature inversion between the surface and 1000 feet would have been 22*F. D. Precipitation The Great Central Valley of California has a dry season in the summer and a wet season beginning in October or November, lasting until April or May. The following table shows the nor-mal amount and the maximum 24-hour amount of precipitation (inches) and the mean number of days having 0.01 inch or more ~ for each month and the year for Sacramento and Stockton. (( TABLE VII PRECIPITATION Stockton Sacramento Mean Days Mean Days Maximum 0.01 or Maximum 0.01 or Month Normal 24 Hours More Normal 24 Hours More Jan 2.55 2.82 9 3.18 2.67 10 Feb 2.46 2.28 8 2.99 2.51 9 Mar 2.05 1.58 8 2.3G 2.07 8 Apr 1.14 1.54 6 1.40 2.22 6 May 0.44 1.22 3 0.59 0.78 3 June 0.07 0.53 1 0.10 0.63 1 1 July 0.01 0.14 0 T 0.09 0 Aug T 0.35 0 0.02 0.65 0 i , Sept 0.19 2.64 1 0.19 1,56 1 l ' Oct 0.63 1.59 3 0.77 5.59 3 l Nov 1.17 2.23 6 1.45 2.09 6 () Dec 2.66 3.01 4 3.24 3.64 9 Year 13.37 3.01 48 16.29 5.59 35 35

T indicates a trace, an amount too small to measure. The normals for both sites are for the period 1931-1960. The 24-hour maximums for Stockton are for a 25-year period and for an 18-year period for Sacramento. The mean number of days having 0.01 inch or more for Stockton is for a 24-year period and Sacramento is for 27 years. The data were taken from the ESSA " Local Climatological Data" annual summary for 1966 for each site. No data are available from Rancho Seco to relate to either Stockton or Sacramento. However, one would expect the range of variation between Rancho Seco and Stockton and Sacramento to be within the range of variation between Sacramento and Stockton. The frequency of occurrence of a given precipitation inten-sity is given in the following table for a 5-year period for Sacramento (in per cent). TABLE VIII PRECIPITATION INTENSITY (inches / hour) Year 0.01-0.09 0.10-0.24 0.25-0.49 0.50-0.99 1961 79.5% 17.7% 2.3% 0.5% 1962 81.8 17.0 0.8 0.4 1963 80.0 17.8 2.2 0.0 1964 86.2 11.3 2.2 0.3 1965 89.0 10.0 1.0 0.0 1961-65 83.5 14.6 1.7 0.2 As an example of the meaning of the table only 14.6 per cent i l of the total number of hours having measurable precipitation had intensities within the 0.10-0.24 inches per hour range for the 5-year period. The persistence of given precipitation intensities is pre- 'l sented in Fig. 19. The curves are based upon the 1961-65 113 36

rh v Sacramento, Calif. 1961-1965 100 g \\NN \\ \\N \\ \\ \\ SU \\ \\N \\ _, \\ \\ # N y \\ w w h o I, n v 10

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r V s U N 't \\1 c N T N ^ \\ \\ I \\ 4 O b I 3 \\ \\ a .) 2 9 9 n L U y i >\\ i \\ .5 x s N' .2 I 2 3 4 5 10 20 30 40 50 100 Duration (hours) Intensities >0.5 inches / hour occurred for 1 hour or less Fig. 20. PERSISTENCE OF PRECIPITATION I'a 37 114

precipitation data from Sacramento. As an illustration of the use of this graph, once a precipitation intensity 1 0.10 inches / hour had occurred for one hour, that rate would be maintained ten per cent of the time for a total of about 4.4 hours. It should be noted that the curve for intensities 1 0.25 inches / hour does not follow the smooth pattern of the others. This is due to the small number of occurrences of precipitation intensities of this magnitude (see Table VIII). Intensities 10.50 never occurred over a longer period than an hour in the 5-year period. Snow and sleet are very rare in the area with Sacramento having reported a trace as its maximum monthly total within the last 18 years. Stockton recorded none in the last 12 years. E. Humidity Table IX presents the occurrences of each 10 per cent division of relative humidity for given ranges of temperature and wind speed. The data are for January, April, July, and October for Sacramento from 1951-1960 as presented in the "Climatography of the United States No. 82-4, Summary of Hourly Observations for Sacramento, California". The average relative humidity for four different hours of the day at Sacramento, Stockton and Mather AFB is presented in Table X. Stockton data are for a 7-year period, Sacramento for 6 and Mather AFB for 10 years. Note that Mather AFB is summar-ised for 3-hour periods. A hygrothermograph was operated at the Rancho Seco site during the six-weeks study. Humidities from this instrument were compared with the corresponding humidities at Sacramento for the available data of record. In general, the sites show good agreement with 90 per cent of the pair of values being within 10 per cent relative humidity of each other. There is 115 38

TABLE IX m@ERATURE AND WIND SPEED-REI.AUVE HUMDTTY OCCURRENCES [/- ,3 SAC.RAuElrTO, CALIF. 1951-1960 g h 1cipal Airport ,\\ JMAEI m,. m m,. ....,m m, a,e o 8 8lI l. 8 l 8 i I l. I i 8 I I. I i 8 I l. 8 1 8 "~ i Ae/ 89 2 3 1 2 10 64/ 60 1 9l 2 1 1 1 th % I4 1 7 6 11 I! E l %j 1 112 99/ Si M 14 21 21 17 2 ai 7 41 6 64i 41 18 33 2 IW 64 I! 2 e 12 7 S9 94/ SC 1 11 9 19 70 6A 15 173 11 19% 251 19 9 21 49 72 162 E Il le 17 401442 69/ 41 2M S 70 83 ti 110 1 60l 121l IS ??ai 981 1 01 43 40l 109 led 3 14 $ 13 4E 412210 7 224 St. 2 32! 14 74 71 1 Il 1 8 2516S3 66/ 40 lu 2 17 99 107 1 2 ag a*N 3e tem 139 a a 1 IN q la il 5 l 1001 Se/ 19 2 4 29 sq 2nq 34/ 39 7 29 f ai 102 21 SW 64 94 1* 1 1 Si i 1 173 79/ 21 to a' la e 1 SO ?a?.L 94 lee 219 60080ae

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N. TABLE X AVERAGE RELATIVE HUMIDITY (in per cent) Stockton Sacramento Hour Hour Month 0400 1000 1600 2200 0400 1000 1600 2200 PST ~ Jan 90 87 69 86 91 88 72 8 'l Feb 88 79 59 80 86 79 59 80 Mar 85 68 50 76 85 70 53 78 Apr 81 55 40 71 85 61 45 76 May 77 47 34 64 84 54 39 73 June 70 42 28 56 78 48 32 66 July 65 41 24 49 77 48 28 62 Aug 66 44 27 51 77 51 29 64 Sept 67 47 30 55 77 52 32 65 Oct 74 56 38 64 78 58 41 69 Nov 86 78 61 80 87 78 63 81 S Dec 93 90 80 90 92 89 78 90 / Year 79 61 45 69 83 65 47 74 Mather AFB Hour Month 03-05 09-11 15-17 21-23 Jan 90 82 72 87 Feb 85 72 59 80 Mar 82 63 49 74 Apr 81 57 43 72 j May 79 51 37 67 June 72 46 30 58 July 65 43 26 51 Aug 68 46 32 55 Sept 68 47 28 57 jj/ Oct 72 51 36 61 Nov 81 65 52 73 Dec 87 79 69 83 / 40

. r( ) a tendency for Sacramento to have higher relative humidities than Rancho Seco for the values above 40 per cent. Study of Table X indicates a similar relationship between Stockton and Sacramento, at least during the same time of year. The average minimum relative humidity for the six-weeks period was found to be 40.6 per cent for Rancho Seco compared to 41.9 per cent for Sacramento. Considering the 3-5 per cent relative humidity accuracy to be expected with the hygrothermo-graph, the difference in the average minimum relative humidity between the two sites cannot be considered significant. O 118 a k 41

l VI. DIFFUSION MODELS '1 A. General The most commonly used equation for diffusion from a con-tinuous point source is: exp [- f ( d + M }3 O x(x, y, 0) = 2 2 Hueyo a z oy z where X is the concentration at ground level at a downwind distance of x from the source and a crosswind distance of y. Q represents source strength, u the mean wind speed and h the height of the source above ground. o and o are the standard y z deviations of the cloud width and height, respectively, at the distance, x, from the release. Although most diffusion prediction systems utilize the above equation as a basic model, a variety of methods has been suggested for evaluation of the oy, az parameters required in I the equation. B. Estimation of Diffusion Parameters 1. Pasquill Method A technique for estimating c and o was formulated by y g Pasquill (1961) and subsequently extended by Hilsmeier and Gifford (1962). Nomograms were developed for estimating o and oz, based on experimental data extended by theor-y etical expectations. Meteorological parameters which served as inputs into the estimating technique were gross in nature and related to but not fundamental to the diffusion process. The technique, in effect, describes an empirical relation between the commonly measured weather rarameters and the associated diffusion characteristics under average terrain conditions. In smooth or changing terrain situations, for example, there is no adjustment available within the model to account for the non-average conditions. t =2 119

r 2. Markee Method O Markee (1966) has recently adapted the Pasquill system for the local conditions characteristic of the NRTS site in Idaho. The adaptation consisted first of defining the i Pasquill meteorological categories distinctly by times of 1 I day and cloud cover which applied to the NRTS site. This definitization is necessary for computer processing of large quantities of climatological data into frequencies of occurrence of the various categories. A second modification in the Pasquill system was the attention called to length of release. Analysis of long duration releases generally showed broader plumes for stable conditions than predicted by the Pasquill system. This feature has been attributed to the slow meandering character of the wind under stable conditions. In terms of long release times, this meandering may serve to decrease the total exposure at any specific location by -s a significant amount. The Markee curves take into account s a reasonable amount of this meandering and are thus in-tended to be applied to release durations of 15-60 minutes. C. Turbulence Measurements The Pasquill and Markee techniques are not able to take into account the effects of local site characteristics on the diffusion conditions. Direct measurements of turbulence have been suggested by various workers as a means of incor-porating these local effects. Diffusion models based on ~ turbulence observations have been developed by Hay and Pas-quill (1959), Cramer (1959) and Fuquay, Simpson and Hinds (1964) among others. The technique suggested by Fuquay et al. has been compared to other models and to experimental data (Fuquay and Simpson, 1964) and has been shown to give results comparable to the Pasquill system. The Fuquay technique has the further advantage that experimental data (taken at Han-() ford) from large distances (to about 20 miles) have been ~ 120

used in developing the model and such data have not been in-corporated into the previous techniques. The Fuquay system consists of an empirical equation for the calculation of o from observed data of and E where y e og is the standard deviation of the horizontal wind fluctu-ations and u is the mean wind speed. The input parameters into the model are the product (Eoe) and the time of travel ~ to the exposure location. The following equation is given as a predictor of oy: oy : At - Aa + Aae-t/a where A = 13 + 232.5 o E e A a= Ee) 2( t= time of travel. The equation is also given in nomogram form in the quoted j reference (Fuquay, Simpson and Hinds, 1964). Vertical growth characteristics of the diffusing cloud are treated in the Fuquay technique by incorporation of the Richardson number: Ri = g (BT/az + r) T (au/az)2 where g = 32.2 ft/sec T = air temperature r = 5.4 F/1000 ft u = wind velocity i21 z = height above ground. The Richardson number, in this usage, expresses a relation between the heights of 7 and 50 feet above ground. Exposures at specific locations are given in nomogram form in terms of travel time, c u and the Ri-hardson number. e O'

D. Development of Climatological Statistics 7() The development of an annual diffusion climatology for the Rancho Seco site requires the use of the Pasquill or Markee system since no wind fluctuation data ( e) exist for the site over any extended period of time. Standard weather observations can, however, be used to estimate the diffusion climatology for the Pasquill or Markee techniques. For this purpose, Sacramento and Stockton weather data were available as the closest locations to the Rancho Seco site with long periods of record. In order to process the large amount of data required for the climatology, a computer program (WBANDA) was used to categorize the data into the various diffusion categories for each three-hour interval of record. In order to avoid ambiguity in the categorization, a definitive classification system was set up to describe the categories in terms of the available weather data. This classification system follows the Pasquill-( Markee methods closely wherever possible but, where minor questions developed, the latitude, radiational characteristics and solar angles of the Rancho Seco site were used for the final adjustment of the system. The details of the system used for the Rancho Seco site are given in Table XI. The classification system shown in Table XI was used on seven years of data from the Sacramento airport and six years of data from the Stockton airport. The data were summarized at'three-hour intervals and grouped for the entire day. Fre-quencies of occurrence for each diffusion type are shown in Table XII. Additional details on the frequencies of occur-rence as a function of wind direction for Stockton and Sacra-mento are given in Tables XIII and XIV. The most striking feature of Table XII is the difference in the G category for Sacramento and Stockton. It is appar-ent that the-nocturnal drainage flow from the Sierra Nevada Range has a more pronounced effect at Sacramento and keeps j() many of the nighttime hours from fallingvinto Nhe G category. I A longer period of record from the site will be needed to ( ]22 45

TABLE XI DIFFUSION CLASSIFICATION SYSTEM FOR RANCHO SECO SITE Time of Day by Month Mar Nov Apr Dec May June Cloud Cover Jan Sept July Wind Speed 0/10-6/10-Over-Feb Oct Aug (knots) 5/10 9/10 cast Insolation 09 09 <4.0 B C D Slight 15 4.0-5.9 C C D 6.0-9.8 C D D >9.8 D D D 12 12 09 <4.0 A-B B C Moderate 15 15 4.0-5.9 B B-C D 6.0-9.8 B-C C-D D 9.9-11.7 C-D D D s >11.7 D D D i 12 <4.0 A B C Strong 4.0-5.9 A-B B C 6.0-9.8 B C D 9.9-11.7 C C D >11.7 C D D 18-06 18-06 18-06 <4.0 G F D Night 4.0-5.9 F E D 6.0-9.8 E D D >9.8 D D D The cloud cover categories include: 0/10-5/10 is scattered, thin broken, or thin overcast. 6/10-9/10 is broken. Overcast is 10/10, opaque. e) 46 '^~ ld)

TABLE XII t U PERCENTAGE FREQUENCIES OF DIFFUSION CATEGORIES Sacramento Stockton Mean Wind Mean Wind Category Occurrence Speed (knots) Occurrence Speed (knots) A 0.58 2.5 0.61 2.8 A-B 5.31 2.9 4.77 2.9 B 8.49 4.1 9.45 4.3 B-C 4.51 8.4 7.12 8.3 C 5.31 6.3 5.94 5.6 C-D 1.58 10.8 1.42 10.2 D 33.57 11.0 21.50 6.8 E 17.32 8.h 10.83 8.1 F 12.73 4.9 12.81 4.6 G 10.59 2.4 25.56 1.8 DIFFUSION STABILITY CATEGORIES A. Extremely unstable B. Moderately unstable l C. Slightly unstable D. Neutral E. Slightly stable F. Moderately stable G. Extremely stable a g 124

NONOMONO@4 0000000000 K O@NOnomDom 1 e e e o e e e e e < "N 4 COCOCOOOOm 4 .) J e e e e o e o e e e J OCOCCQQOC ^ U U M 4 NmWNemht&w O m & W r.4 C A 4 N O ONON40@@@2 e e e e e e e e e mmmm'o emoe4N Z e e o e e o e o e e Z g COCCCO-CCC m-W M4&NOO4NC@ CN4545tm&C 3 OmtmWNONN 4 1 e e e e e o e o e e Z e e o e e e e e o e Z mmemeONm4N g Z OCOCOON300 Z mm v MmmtN&dD4M &W 4NNDemer g 3 MNOWNmMppe 3 e e *

e o e e e e

= g Z e o e o e e o e o e Z NmemeCOC4N COM COONOCO mm g O v e&CmO-NENs &44m-O@rx> 3 OmmmNO4MNm 3 e o e e o e o e e e Z e * * * *

e e e e Z

N9 tNmmWW4N 1 OCCCCCOC30 9 3 m 6 O @NN4nme~Ng s mWO@@NMC44 GNmmNODNe@ m e e e e e e o e o e E e e e e e e e e e e 3 NmdN4MDt4N OCOCOOOOOO O m 4 W W 3 4&@N@mN&mo CN4 OMMEm&N 4 3 OmemM O24mm Z 1 e e o e e e o e o e 4 m e e e e e o e e o e m m NmmmcOOg4N 3 -m b C 3 OCCcOCOOOc Z a 2 W e m4CNONMmmm O 44444 GCN-2 4 8 3 GhNNWmmO4@ m 3 e e e o e e e e e e B 4 m e e e e e o e e e e O NmmzzMPgmN H g ,e OcmmOOpmmO O mm H Q 'm W m G H J 4 'o N&memOqhme m Omeer@C@es e g g 3 ONDN4mDQm4 C 3 e e e e e e e e e e H O J m e e e e e e e e e e O mmmDxONL4N X 4 m ODOOOOMM OO Q m Mm B e Z e O 4 W g MetmeN&mst I e 5 ca4 n-nmec / a A 9 m m 4 - &l& D s l M e e e e e e e e e g m e o e e e e 4 e e e W W mm4mcoemfy O i el ,0 2 OCOCOCWNmc l Q Z mm 4 6 z o 6 2 N O of 5 m i i m m y Cl Z W O N O & S N mle M M CcC4mSmm-r y W UW OCNON ONONm W Ow e e e o e e o e e e 4 h U Wm e e e e e o e e e o > Wm M N 4 A m mm t s N O E Em qCOOOO4 nmo m am mm l J m Q IW = 4 O lE O = 3 e: i 2 N@ MON @ tth e CNNNS ON-O,T g hl '2 OW C -mCMCO OmO 4 Qw e e e o e e o e o e m ZW e o e e e e a e o e Zm C N m % g, & c t f. N 2 3 i m = M QCOCOOmimNm 4' 3 Q 4 r { = ON@mOOMOmm W O m m Om O & OO N 5 W OOOOM O Nam W 4 4 W e # + e o e e o e e O 3 m e e e o e e e o e o W V. O N m a Vi O 4 E 4 N .m W 7000000000 W Q 'm T W E O M l> ONCamomeNo w OEN ON D> m t h 4 m O O m o m CNem m m e e e e e e e e e e g im W e e e e o e e e e e Q W ONNNmotN4N w O oOOOCOO Doc W W X 1 W W O t t C N O& Nm W m CDNODOMNDk d O W OGOCOO-DM-U e e e e e e e o e e 4 Z Z e e o e e o e e e e 3 Z CNmO4 -4N4N g m W CO00000000 Z W = W m 3 4 5 OCCNECNmed O m m oc ON c c m M W OmNOOOMONO W W e * *

e e o e e e J

J Z e e o e o e e o e o O Z RNmNmomW4N 4 m COCOOOOOOC 4 3 m E Z 4 W 2 N Om%mN~O4mm Ommc4 O t t, m r e e o e e o e e o e 4 m W CC-CCOmomN 4 w Z e e e o e e e e e e Z MNmze&th4h e Z COGCOOOOCO e 4 0 M M rl. W 3 0 3 W E U 3 C 4 tm80 8OWkC C 4 0@ CO 8OW Z 4 m u z 4 m u / m m s 9 125 u

q p ( O TABLE XIII (continued)

- - ANNUAL AVEHAGE (BASED ON 7 YEAB_0f. Q11AL_St!

SACRAMENTO AREA

e*

~

- WIND ROSE FOR EACH STABILIrv INDEx IN PERCENT OF EACH tilde X TOTAL) **

W1HD DIRECTION INDEX NNE NE ENE E ESE SE SSC S SSW SW WSW W WNW NW NNW N CALM A 6.85 0.85 0.00 0.00 0.00 0.00 0.85 2.54 4.24 14.41 7.63 14.41 13.56 19.49 5.93 3.39 11.86 A8 1.01 1.84 0.74 1.38 0.46 2.21 1.29 6.62 5.44 14.01 7.28 14.56 7.28 13.73 6.45 4.24 11.24 8 1.38 2.31 0.52 2.07 1.04 4.50 2.36 0.34 7.67 14.18 8.07 9.39 9.88 12.16 8.07 5.53 8.53 8-C o.76 0.43 0,00 0.22 0.22 c m7 6__1._9 5 6,u4_17.40 27.14 8.25 3.91 3.37 12.38 11.51 4.78 0.00 C 1,29 1.47 0.46 2.03 1.84 5.71 5.25 9.02 9.12 13.9c 3.50 4.97 3.7R 13.54 13.76 8.38 2.49 C-0 0,93 0.00 0.31 0.00 0.00 1.24 1.24 7.45 1H.94 36.02 5.28 1.24 0.93 10.25 12.73 1.42 0.00 D n.89 0.96 0.55 2.17 2.14 11.79 12.59 11.69 11.32 18.84 2.59 1,82 1 25 6.38 8.45 4.84 1.71 E 0.37 0.31 0.14 0.93 2.23 17.54 12.06 16.78 11.36 20.48 2.82 1.16 1.02 5.56 4.44 2.80 0.00 F 1.00 2.04 1.04 4.08 4.58 16.83 9.50 14.88 6.81 11.65 2.77 3.46 2.11 7.38 6.00 5.42 0.50 G 2.17 S.08 1.57 7.53 3.83 10 07 4.99 _?.20.*.67 8.96 2.96 6.05 1.71 7.67 4.67 7.62 12 66 c Q

- GRCSS w!ND ROSE (IN PERCENT OF TOTAL 08S.) **

WINn DIRECTIor. INDEX f1NE NE ENF E ESE SE SSE S SSW SW WSW W whw NW NNV N CALM l.01 1.57 0.62 2.57 2.31 11 06 8.72.11.3d 9.66 16.87 3.77 4.01 2.38 8.17 7.35 5.04 3.50 I

- STABILITY INnEx DIST4!HUTION FOR EACH WIND DIHECTION (14 PEHCloff 0F DIRECTION TOTAL 1 **

WINO DIHECTION INDEX t!NL NE ENE E ESE SE SSE S SSW SW W5W w WNW Na hNW ft CALM i ,A 0.48 0.31 0.00 0.00 f. 0 0 0.00 0.06 0.13 0.25 0.49 1.17 2.08 3.29 1.38 0.47 0.39 1.96 A-B 5,31 6.23 6.30 2.85 1.06 1 06 0.79 3.10 2.99 4.41 10.25 19.29 16.76 8.92 4.66 4.47 17.06 B 11.59 12.46 7.09 6.84 3.81 3.45 2.3n 4.73 6.73 7.14 18.16 19.90 20.99 12.63 9.32 9.33 20 70 B-C 3.38 1.25 0.00 0.39 0.42 0.31 1.01 2.71 0.15 7.25 9.06 4.40 6.38 6.83 7.06 4.28 0.00 C 6.76 4.98 3.94 4.18 4.23 2 74 3.20 6.21 5.01 4 38 4.93 6.59 8.46 8.Au 9.59 8.u4 3.78 FN) C-D 1.45 0.00 0.79 0.00 0.00 0.18 0.22 1.03 3.09 3.37 2.20 0.49 0.67 1.98 2.73 1.07 0.00 C7s D 29.*7 20.56 29.92 28.33 31.08 35.8n 48.51 34.48 39.34 37.51 23.09 15.26 17.70 26.23 36.62 32.26 16.36 E 6,2a 3.43 3.94 6.27 16.70 27.40 23.9H 25.54 29.35 21.03 12.97 5.01 7.41 11.80 10.45 9.62 0.00 F 12.56 16.51 21.26 20.15 25.16 19.34 13.87 16.e4 E.96 8.79 9.34 16.99 11.32 11.50 10.30 13.70 1.82 G 22.71 34.27 26.77 30.99 17.55 9.65 6.c6 7.35 5.11 5.63 8.04 16.00 7.61 9.94 6.72 16.01 18.12 l E

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o @ceOOocm oe e =e me N we se ,= se e

=

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e C

6

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e k

b 4 ID N N N O O O se N

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e h e

e .A e 3 3 a O e et r.,o e O O O N & 3 .m== N O O c e N O fs e e-pamOOOMO o =

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r a

= m 889 N O o e m e =.e :P e O c c e N O C e-1) 6

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== 0 at 6 C

=

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= *= @ m & e d me

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== N e af. m m m f% w

= =

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m Zu C4CoccCO w Zu DOomeNOC 20 mo = Zu a 4J O 7 b -== == w C e m e L 0 o 3CO*-Nmco 2 OOcto-Oc P- -O m O O ** C O OP= N #"t C O C

== O O n== P= 4 O O 3

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== Jv e e e e e e e e Z .J u o e =e .a u V at e-O O C N== e C O >== OOON& COO

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== 0 .IJ 1 e 40 e /' H me

== > V >=. A H b M 2 se OOC ***@CO 2 m O O O C &== O C

== V

== O V d Z a= U O O O Len =e c O u oGOeNmo= O u +c I O e N O p g e e o e o e e e e e e e e o e o e e e o e u a E X 7

== == CD C O C O me N O O

== G1 O O O @ Ne= 0 O w (D 4 O g CD O G C = * ~ sa =w of O M O X 8' 2 2 4 w 2 W C O O O P= N O O if C O O fr. f*14 OC

==

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= A w a = c o m C ef CO O O c c d fr a oC 4 C N A J c e e o e e o e e I m e e e e e e o e 3 e e 2 e atf. el 3

== 0OOmNNOO OOOe=*OOO 4O =* O

% N ft

== w b .8 .a., a e=

== A gg C me 23Cft&99 = O O O *1 1. C O

- C O

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h

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== g e e e o e o e e

== c e e o e o e o e e o e f.,, e N at c.J 2 e n.3 gC 4 4 N **

== K

=

3 <a 3 e + 1 z sOOOtpOOO O2OON335 e 2O a .,3 ODOOf900 OCDOeODO

== fC C .g .J .J e o e e e e e e e J 4 e e e e e e e e 2 as e e 4 at A p q 2 oOO00 COO g Oc004O3C g = 3 2 z a= 3 3 aJ 2 C O O e as a= r r o e e e e o e e e e e E OOCOOODO e E OOOOOC OO e g >= e Q e 3 OOccoOO 3 OOOODC3 3 >Z w

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3 f*t a @ N ft S== 0 e3 48 Z

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== ** -e N g O== EL Z W J l l l m7 50 ) t' / -

m em TABLE XIV STOCKTON STABILITY DATA alm < 0.5 knots)

- - ANNUAL AVERAGE (8ASED ON

6. YEAR.0F DALA) ??*

STUCKTON AREA

ee

~

- STABILITY INDEX DISTRIBUTION IN PERCENT OF TOTAL 085. **

WIND DIRECTION INDEX NNE NE ENE E ESE SE SSE S SSW SW hSW W wNW NW NNV N CALM A 0.01 0.01 0.00 0.00 0.00 0.01 0. M] _0.41 0.01 0.06 0.Q5 0.14 0.07 0.17 0.02 0.02 0.03 4-8 0.07 0.11 0.05 n.09 0.03 0 11 0.07 1.16 0.07 0.24 n.19 0.90 0.57 0.90 0.21 0.27 0.70 8 0.13 0.15 0.05 (.15 0.10 0.33 0.16 ). 29 0.10 0.23 0.41 1.59 1.51 2.11 0.58 0.49 1.08 l l B-c c.oS 0.03 0.02 0.02 0.01 0 09 0.09 0.03 0.93 1.05 a.45 1.14 1.8% 2.44 0.63 0.22 0.00 C 0.06 0.13 0.02 0.17 o.10 0 44 0.27 3.19 0.06 0.16 0.24 0.80 0.84 1.3? 0443 0.29 0.40 C-D c.01 0.01 0.00 0.00 0.00 0.03 0.04 0.02 0.00 0.05 0.21 0.16 0.29 0.45 0.14 0.03 0.00 i 0 0.18 0.44 0.20 0.77 0.74 3.85 2 23 1,09 0.25 0.52 0.92 1.77 1 54 1.99 1.22 n.91 2.89 t E 0.11 0.06 0.01 0.01 0.03 0.33 0.11 0.04 0.01 1.1H 1.08 3.52 2.53 1.72 0.62 0.45 0.00 F 0.34 0.34 0 07 0.27 o.18 0.50 0 21 9.25 0.08 J.35 0.99 3.29 1 91 1.66 0.54 1 07 0.74 G 0.58 0.84 0.19 0.78, 'c.29 0.65 e.*1 0.59 0.22 0.96 1.00 3.53 1 59 1.96 0.80 1 27 9.69 AVEHAGE W1HD SPEED FOR EACH STABILITY INDEX ANO DIRECTION (IN MNOTS) ** i WIND DIHECTION INDEX NNE NE ENE E ESE SE SSE S SSW SW WSW W WNW Na NNW N CALM i l A 3.0 3.0 n.0 00 0.0 3.0 0.0 3.0 3.0 3.0 3.0 2.9 3.0 30 2.8 30 0.0 j A-8 3.2 3.0 3.0 3.0 3.2 3.1 3.0 3.0 2.8 3.2 3.4 3.6 3.6 3.4 3.8 3.5 0.0 8 3.7 3.*

.4 3.3 3.3 3.4 3.6 3.6 3.4 3.4 5.2 5.1 5.7 5.2 4.8 4.5 0.0 i

B-C 7.9 5.2 8.0 7.3 40 7.9 8.2 7.2 8.4 9.0 80 8.2 8.4 84 8.4 81 0.0 j C 4.1 3.4

.8 4.o 4.7 5.0 5.5 4.0 4.0 4.8 6.5 5.9 6.6 71 7.5 5.s 0.0 i;

C-0 9.0 8.0 0.0 0.0 0.0 8.8 3.6 8.3 0.0 9.6 10.1 9.4 10.6 10.7 10.7 10.2 0.0 ~ D 5.0 4.7 4.3 4.6 57 7.7 8.* 4.9 4.4 5.5 8.3 8.0 8.4 10.o 12.7 7.6 0.0 I\\3 E 6.9 7.o 4.0 6.4 7.3 6.8 7.3 6.1 9.0 8.2 8.3 8.2 8.2 S.3 8.0 77 0.0 CX) F 4.8 4.6 4.6 43 4.7 4.5 42 41 36 4.5 4.9 4.9 5.1 50 4.9 5.n 00 G Z.9 29 2.8 29 29 2.9 29 29 28 29 2.9 30 3.0 29 3.0 30 0.0 i j e

7 TABLE XIV (continued) l j

- - ANNUAL AVERAGE (BASED ON 6 YEAR.0F DALAl._tt' STOCKTON AREA
- WINO ROSE FOR EACH STABILITY INDEX (IN HERCENT OF E4CH TNDEX TOTAL) **

WIND. DIRECTION INDEX NNE NE ENE E ESE SE SSE S SSW SW WSW W WNW NW NNW N CALH A o.94 0.94 0 00 0.00 0.00 1 89 0."0 0.94 1.89 9.43 8.49 23.58 12.?6 27.36 3.77 2.83 5.66 A-8 1.56 2.40 0.96 1,80 o.72 2.40 1.56 3.35 1.56 5.03 4.07 18.80 11.98 18.92 4.43 5.75 14.73 0 1.33 1,63 0.48 1.63 1.09 3.50 1.69 3.n2 1.03 2.49 4.29 16.80 15.95 22.30 6.10 5.20 11.48 8-C o.64 g.40 0.24 0.24 g.08,1.28._1.30 0.40_.0.40 0.64 6.33 15.95 25.96 34.21 8.89 3.13 0.00 C o.96 2.12 0.38 2.88 1.73 7.40 4.62 3.17 1.06 2.69 4.04 13.56 14.23 22.31 7.31 4.81 6.73 C-D C.40 0.40 0 00 0.00 0.00 2.41 2.81 1.20 0.00 3.21 14.86 11.24 20.48 31.33 9.64 2.01 0.00 0 0.82 2.04 0.93 3.50 3.45 17.92 10.35 5.07 1.14 2.42 4.30 8.23 7 17 9.24 5.65 4.25 13.43 E 1.05 0.53 0.11 0.26 o.32 3.no 1.00 0.37 0.11 1.63 10.01 32.51 23.39 15.86 5.69 4.16 0.00 F 2.63 2.67 0.58 2.09 1.43 3 92 1.65 1.96 0.62 2.76 7.75 25.67 14.88 13.10 4 19 8.33 5.75 G 2.26 3.31 1.52 3.06 1.14 2.52_.1.61.2.30 0.87 3.75 3.93 13.83 6 19 7.68 3 15 4.96 37.93

- GROSS WIND ROSE (IN PERCENT OF TOTAL OBS.) **

WIND DIRECTION INuEX NNE NE ENE E ESE SE SSE S SSW SW WSW W WNW NW NNW N CALN l 1.52 2.12 0.80 2.28 1.50 6.35 3.59 2.65 0.83 2.79 5.56 16.84 12.70 14.73 5 19 5.02 15.54

- STABILITY INDEX DISTRIBUTION F R E4CH w!ND DIRECTION (IN PERCENT OF UIRECTION TOTAL ) **

O WINO DIRECTION INDEX NNE NE ENE E ESE SE SSE S SSW SW WSW W WNW NW NNW N CALM 4 A o.3R 0.27 0.n0 4.00 o.00 n.18 0.00 u.22 1.37 2.04 0.92 0.85 0.58 1.12 0.44 0.34 0.22 ~AH 4,89 5.39 5.67 3.76 2.29 1.80 2.n7 6.e2 8.90 8.50 3.49 5.32 4.49 6.12 4.07 5.46 4.52 8 8.27 7.28 5.67 6.77 6.87 5 22 4.*5 10.75 11.64 8.3R 7.29 9.*2 11 87 14.30 11 11 9 78 6.98 B-C 3.01 1.35 2.13 ,.75 ' 38 1 44 2.38 1.08 3.*2 1.64 8.11 6.75 14.56 16.55 12.21 4.44 0 00 C 3.76 5.93 2.84 7.52 6.87 6.92 7.63 T.10 7.53 5.73 4.31 4.78 6.65 0.99 6.36 5.69 2.57 C-U o.38 0.27 o.on 0.00 0.00 0.54 1.11 0.65 0.00 1.64 3.80 0.95 2.29 3.02 2.64 0.57 0 00 0 11.65 20.75 24.82 J3.83 49.62 60.70 62.00 41.oM 29.45 14.61 16.63 1o.51 12 13 13.49 23.43 18.20 18.59 ~-' E 7.52 2.70 1.42 1.25 2.29 5.13 3.02 1.51 1.37 6.34 19.51 20.92 19.96 11.67 11.88 8.99 a.00 IN3 22.18 16.17 9.22 II.7H 12.21 7.91 5.88 9.4 59 12.6R 17.86 19.53 15 01 11.40 10 34 ?l.27 4 '4) 31.97 39.89 4h.23 34.34 19.47 10 16 11 45 22 1 .71 34 36 18 07 20 98 12 45 13.31 15 51 25 26 8 i s \\_/ %/

(~. l \\ 4 _Y ~ .e MNeocado @meceCem c@ e e -oekooom, NmmCCC4-e cm o e o e e o e e o e e e O e o e * * * *

e C

e e e a ewcomoNe e emmecome em e

m4 NM

= N e e o e m 4 m mmmoooNe m n3@CCCMo e o= 4 W @MmocoNN e emocooNN O ce e E e w e e e * *

e
O 4

h b 4 4 g NNNoooNn memocobw J om O Nmm em 4 e Z J e O J l 5 0 e m g ocoooces 3 >=mCoomN cm g motoCOMO O mMMoooom og e O c w e e s e e e e e Z W e o e o e o e e L W e e m W e O mwmooceN mem97amo o oc e b a a MN = O M k o 0 C 2 w mwh=mona mm4peco* w oo e M MO M m mm m. 2 W N >'4 m N @ 4 U Nm 2 Z O e m e e e o e w= o e e e o e e e e g O e e O ^ e w NNNMmNNN O o-MEMMMe w em V g of u l g mNNNmNNm 4 e' C I anJ G t w } a Z W D A w coomomoc w coom>>eo = x NC w W N N 4 WQ Oooomeno 2 WO coomWOOo = wQ wo o WO Z O s e m e o e o e e- = O g

e e e o e o e oe e e 2

O e O

d 4

= TU ocoOneco 20 o C C' O M e c o 2U mo = 20 p Q W = 2 = m m m O C tr a e = > r Q O Z > O OC oe c o o Z > CCCemmoo k > 40 = > 4 (\\ O = c o'o n.e m o o, G = @ CCmoCoc 3 = mo J = U E' m m Ju e es e e e e e ee = Ju e e e e e e e e e JU e e = JU M 4 > = o p o m m = O O. k.= oco@mNoe

mo e = W 3 m D e 'N = g e e e b e 4 e 4 4 4 E = > = > m > m > H Co** ooo a m cocemmoo o pcoN" moo = m No V M 2 e U U ocoo@Noo O V mc r U e X O e 0 e me o e e o e e e e e o e e e e e e e e U e e Z m = m oco-NMoo = a ocomhaco X e No e e Q O O O en m W 4 O M Q M M Z E g w E w ocoomeoo w Cocke@oo = mo a m a W O ocomemoc O Coommeco do k 4 4 m 2 e o e e e e e e e = e e e e e e e e e e e o e 4 6 e e = ocommWoo = cOC~meoo e o mN= = mo O ~ w J w k = W Q = o c o ok oc o m occhmdoc e h e a m O J e o o S me oC o J G onommoco 4 e No e 4 K = 0 e e e o e e e o = s e o e e e e o e g e e O e N g W e ( ooooNaoo e 4 CooMNeoC m 4 to 2 4 W e 4 4 N = Z 4 3 m W Z Z occomoco ocoodooo O me w e J occo@oco ocoCecco = @c C g J J ( e e e e e eo e J e e o e e e o e 2 4 e e 4 ( N 3 4 E coCococo a o0004000 0 00 E Z 3 3 W 2 O O' O 4 4 I Z O 4 e e e e e e e e e E occocono e C 0o000000 e r k e O e 3 ooooooo 3 000000o 3 >Z w O M@mNeem O MWmNeem O MO W Z mm-N I

===N I O= 2 7' su 1 ' k% 't 53 _+m,,,-,-.m

determine whether the Rancho Seco conditions are more similar to those at Sacramento or at Stockton. In general, for both locations, the G category is rela-tively large. This situation results from the predominance of the thermally-driven wind circulation which dies out during the night and contributes to the frequent occurrence of light winds and stable temperature conditions. From Table XII an average condition for the zero to two-hour dosage model of F with a wind speed of 4.6 knots ( 2.4 m/sec) can be assumed. E. Rancho Seco Site Study A six-weeks observing program was set up at Rancho Seco during May and June 1967 in order to obtain a brief compar-ison with Sacramento and Stockton conditions. Results of the six-weeks program are shown'in the following table: TABLE XV T COMPARISON OF FREQUENCY OF OCCURRENCE OF DIFFUSION CATEGORIES ~) (May-June 1967) Rancho Seco Sacramento Stockton e* u u u c (knots) (avg) AT** (knots) (knots) A-B 4.8 3.1 21.8 -1.3 C 2.5 3.4 B 10.5 4.7 19.3 -1.2 8.5 3.9 5.0 4.9 B-C 7.1 7.8 13.1 -1.2 6.2 8.2 5.0 6.1 C 6.2 4.9 18.6 -0.7 5.9 4.6 5.3 5.8 C-D 2.8 9.1 10.3 -0.9 3.1 9.0 4.7 8.3 D 26.4 9.1 5.0 0.2 35.9 9.5 46.9 10.0 E 15.0 7.2 6.4 0.7 14.4 6.9 16.8 6.1 F 10.2 4.3 5.4 1.1 12.2 4.1 11.5 4.8 G 17.0 2.8 7.5 1.3 11.3 1.7 4.7 0.6

10-minute standard deviation
- Avg temperature difference from 53 to 6 f t at Rancho Seco.

l )l n

1 ( (~ S The data from the different sites in Table XV are in j '\\s) reasonable agreement, with Sacramento having the best agree- ') ment with Rancho Seco. It should be emphasized that enough variance exists between the sites, especially in the G cat-egory, that more data are required in order to completely define the relationship between the sites over a long period of time. A comparison was made between the Pasquill, Markee and Fuquay systems for calculating diffusion using the six-weeks period of record (May-June 1967) from the Rancho Seco site. Calculations of oy at a distance of 1.5 miles were made as a means of comparing the three syctems. Pasquill and Markee nomograms were used to obtain oy while the average o and u s values shown in Table XV were used for the Fuquay system. Results of the comparison are shown in the following table TABLE XVI ,n(j } COMPARISON OF DIFFUSION CALCULATION SYSTEMS (c in feet) y Fuquay Fuquay Category Pasquill Markee (10 min) (1 hour) A-B 410 510 290 380 B 370 390 270 330 B-C 310 350 200 220 C 280 310 280 300 C-D 230 210 170 220 D 180 140 95 190 q E 130 250 110 140 F 90 370 95 200 G 70 140 250 The Pasquill system relates to short releases of the order of 10-15 minutes. The Markee system should apply to releases of 15 minutes to one hour. Results of this dif-ference are shown in the larger cloud widths for the Markee (Q ID system, particularly for E and F categories. A comparison p. 55 132

of the Fuquay system used for a 10-minute release and a one-hour release shows slightly larger values of oy (hour) for all categories from A-B through E. For F and G, however, the differences in o due to the meandering wind over a y one-hour period are readily apparent. Comparison of the Fuquay one-hour values with Pasquill's data shows good agreement for all categories except F and G. It is seen in Table XVI that the Markee system overestimates ey on the basis of on-site measured values and should not be used. Accordingly, it is recommended that the Pasquill curves be used for the Rancho Seco site for categories A-B through E. For categories F and G it is recommended that the Fuquay one-hour values be used. These have been plotted in Fig. 21 where the original Pasquill A, B, C, D, E curves appear but new F and G curves have been drawn to correspond to values calculated by the Fuquay system for a one-hour duration release. The average conditions used for the calculation of the one-hour release values are as follows: TABLE XVII RANCHO SECO AVERAGE CONDITIONS Category u (knots) ce(o)* A-B 3.1 35.0 B 4.7 26.6 B-C 7.8 16.4 C 4.9 23.1 C-D 9.1 15.6 D 9.1 10.8 E 7.2 10.0 F 4.3 13.3 i G 2.8 16.4

Hourly standard deviation

) 56 l33

f 10" : i A [B ~ 10 / f D, s's ' ss ss ,G 2 / O 10 y [ ~ s G) / E s p 's' o s' 1 10 er 0 10 2 3 5 10 10 10 10 Distance Downwind (meters) Fig. 21. PASOUILL 0 CURVES MODIFIED FOR HOURLY RELEASE I 13 <1 57

Allowance should be made in the o values for the fre-z quent presence of inversions in the area. Figure 19 shows the annual variation in average height of the inversion base for all inversions occurring during the night below 5001 feet. An annual average has been plotted in the figure representing a height of 800 feet above Oakland or 600 feet (200 m) above the site. This average value has been used for the purpose of including the typical effects of the inversion on downwind exposures. as modified Figure 22 shows the Pasquill nomogram for oz for adaptation to a 200 m inversion base height. The modi-fication was made as recommended by Smith and Singer (1966). This consists of limiting the vertical growth of the cloud to a o value determined by the following relation: z 1.25 oz=H where H is the inversion base height (200 m in this case). As shown in Fig. 22, small changes are indicated in the D '} and E curves as a result of this modification but it is assumed that the A, B and C classifications do not apply to the nighttime conditions when the low-level inversion is present. Hence, those curves remain unchanged from the original Pasquill system. Use of Fig. 22 is recommended to represent average, stable, nocturnal conditions. Variations in inversion base height from day to day or month to month could be included by modifying Fig. 22 in the appropriate fashion. Data shown in Table VI indicate a comparatively high frequency of surface inversions at Oakland during the night. The Rancho Seco site is expected to be similar with condi-tions at least as favorable for the development of low-level inversions. These radiation inversions are typically 100-200 feet deep. The proposed stack height of 200 feet will deliver material above or near the top of the inversion and will minimize the problem of high exposures in the vicinity m 8

10' j 10 /. s. 7 200 m Inv,e r_sio_n Ba s. e =_ u i i .dGV P g 10 A B D E V F g e 1 10 10 3 5 10 10s 10' 10 Distance Downwind (mete rs) Fig. 22. PASQUILL a CURVES MODIFIED FOR 200 m INVERSION z 59 136'

of the site due to the low-level nocturnal stability. Addi- ) tional on-site data on the vertical temperature structure in the lowest 200 feet will permit a better definition of the downwind exposures under these nocturnal conditions, i 137 i es 60 ~ j

[Q VII. CONCLUSIONS 1. The climate of the Rancho Seco site is generally that of the Great Central Valley of California including hot, cloudless summers and mild winters when the rainy season

occurs, Radiational fogs may persist for several days at a time, particularly during winter.

2. Tornadoes occurred 22 times in California between 1953 and 1962. The probability of an occurrence at any one site in the state is 4 x 10-5 per year and the mean recurrent inter-val is 23,200 years. 3. Thunderstorms are infrequent, occurring about three times each year at Stockton and five times at Sacramento. The frequency of occurrence at Rancho Seco should be similar. 4. The wind flow in the Rancho Seco area is primarily associated with a thermally-driven circulation in the summer and to a somewhat lesser extent in the spring and fall. The site is [) situated near a divergent flow zone caused by the deflection v of air into the northern and:houthern sections of the Central Valley. The resulting flow at Rancho Seco is west to north-northwest at midday becoming light at night. It may remain westerly at night, become calm or if drainage from the Sierra Nevada is sufficient, it may turn southeasterly with speeds equal to the daytime flow. Strange synoptic pressure gradi-ents prevail during the winter resulting in similar wind trajectories in the Sacramento, Stockton and Rancho Seco areas. -5. Extreme wind speeds at Sacramento and Stockton are similar and would probably be representative of the Rancho Seco site. Sacramento's extreme wind speed of record has been 70 mph. 6. Precipitation occurs at Sacramento with southeast to south winds 65 per cent of the time. Since these winds are associated with the synoptic gradient, a similar relation- ' / ship can be expected at Rancho Seco. (1_-) I% 61

7. Temperatures at Stockton, Sacramento, and Rancho Seco are, on the average, in agreement with each other. 8. Temperature inversions at Rancho Seco may be expected fre-quently at night at the surface as a result of radiation. During the summer an inversion depth of several hundreds of feet occurs as the result of the flow of cool marine ~ air into the area during the late afternoon and evening hours. Radiational fogs occur in the winter occasionally persisting for several days. 9. The yearly rainfall occurs mostly between October and May. The yearly normal for Sacramento is 16.29 inches and 13.37 inches for Stockton with maximum 24-hour amounts of 5.59 inches for Sacramento and 3.01 inches for Stockton. Rancho Seco should be similar. 10. During a six-weeks comparative' study the relative humidity at Stockton, Sacramento and Rancho Seco were, on the aver-age, in agreement with each other, within the accuracies l' of measuring equipment. 11. An average condition for the zero to two-hour dosage model of F with a wind of 2.4 m/sec is recommended for the Rancho Seco site. 12. Existing information available for the Rancho Seco site suggests the use of a slightly modified form of Pesquill's diffusion calculation system to provide estimates of downwind exposures. The Pasquill A through E curves have been re-tained but new F and G curves have been drawn by use of the Fuquay technique to take into account the effect of mean-dering winds on hourly dosages under stable conditions. A slight modification is recommended in the o ' curves due to z the frequent presence of low-level inversions in the area. The annual average height of the inversion base is about 200 m above the site. ) 139 62 \\

f(v] VIII. REFERENCES 1. Cramer, H. E., 1959: A Brief Survey of the Meteorological Aspects of Atmospheric Pollution, Bull. Amer. Meteor. Soc., 40, 4, 165-171. 2. Fuquay, J. J. and C. L. Simpson, 1964: Atmospheric Diffu-sion Experiments and Prediction Models, Nuclear Safety, 5, 4, 403-409. 3. Fuquay, J. J., C. L. Simpson, and W. T. Hinds, 1964: Pre-diction of Environmental Exposures from Sources Near the Ground Based on Hanford Experimental Data, J. Appl. Meteor., 3, 761-770. 4 Hay, J. S. and F. Pasquill, 1959: Diffusion from a Con-tinuous Source in Relation to the Spectrum and Scale of Turbulence, Adv. in Geophys., 6, Acad. Press, Inc., New York, 345-365. ('/) 5. Hilsmeier, W. F., and J. A. Gifford, Jr., 1962: Graphs for Estimating Atmospheric Dispersions, U. S. Weather Bureau, Oak Ridge, Tenn., USAEC Rept., ORO-545. 6.

Pasquill, F., 1961:

The Estimation of the Dispersion of Windborne Material, The Meteorological Magazine, 90, 33-49. 7. Smith, M. E. and I. A. Singer, 1966: An.-Improved Method of Estimating Concentrations and Related Phenomena from a Point Source Emission, J. Appl. Meteor., 5, 631-639. 8. Thom, H. S. C., 1963: Tornado Probabilities, Mo. Wea. Rev., 1 91, 10-12, 730-736. 9. Yanskey, G. R., E. H. Markee, Jr., and A. P. Richter, 1966: ~ Climatography of the National Reactor Testing Statior., 1 Idaho Falls, Idaho, ARFR0 Rept., IDO-12048, 140 , <-ss %,) 63 ~ /}}

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