DECBKBER. 1973 ANDREWjOHNSON. JR.. A NO AMES J O'BRIEN 1267 ContributionNo.-!?3 ~~ GeophysicalFluid DynamicsInstitute t-ioridaState University A Study of an Oregon Sea Breeze Event1
ANDREW JOHNSON, JR.., AND JAMES J. O'BRIEN D.jJl. of M--doD, FloridIJ SIGMUm-sily, TallIJhass. JZJ06 (Manuscript received 30 Apri11913, in reviaed form 4 September 1973)
ABSTRACT A series of meteorological observations including aircraft, pilot bal1oon (pibal), rawinaonde, surface buoy, and specialland-based surface observations was taken on 23-24August 1912,on the central~ coast, to investigate the mesoscalethennal and kinematic ~nsesof the lowest 4 km of the atmosphere during a sea breeze event. A desaiption of those field observations is given. Vertical crag sections of the wind field on a line per- pendicular to the coast, extending 00 km inland from data obtained at three pibal stations, are presentedand discussed.Time sections of the wind field and temperature fields at the coast are discussed.Mesoscale fea- tures are presentedand related to prevailing synoptic-scale changesoccurring aloft during the observational period. The seabreeze event on 23 August exhibited the following important characteristics: 1) a sea breezefront, distinguishable in the zonal wind field, which penetrated more than 00 km inland; 2) a distinct wind maxi- mum which followed the front inland; 3) the surface onshore ftow at the coast which took place below the main inversion, deepeningthe marine layer at the onset; and 4) a return ftow above the inversion which ap- peared in quasi-periodic surgesin responseto surgesin the sea breezeftow.
1. Introduction daytime heating which producesa large-scalegradient The land-sea breeze circulation is one of the most wind flow from the north along the coast.This persistent interesting mesoscale atmospheric phenomena observed northerly componentin the local surfacewinds accounts in coastal regions during periods of fair weather. As a for the coastal upwelling phenomenonwhich acts to simple exampleof one of the most fundamental atmo- reducenearshore sea surface temperatures. This unique spheric processes(i.e., the generation of motion by combination of intense heating inland and the cold sea differential heating), the sea breeze occurs in many surface produces very high coastal thermal gradients areas with extraordinary strength and persistence.It which leads to the developmentof a strong sea breeze may differ considerablyin character from one area to circulation. another, varying in direction, intensity and time The importance of the sea breezein central Oregon accordingto local conditions (Flohn, 1969).Interaction cannot be over-emphasizedas it representsthe meso- with other local wind systems may complicate the scale vehicle through which marine air routinely diurnal wind pattern of a particular area making it penetrates the interior valleys. Knowledge of the difficult to extract those atmosphericresponses related quantity of marine air entering the valleys on any given directly to a seabreeze event. The prevailing large-scale summer day is vital to forestry operations and to air synoptic flow alsohas a direct effecton the strength and pollution interests. This quantity is a function of the landward penetration of sea breezes. Koschmieder strength and depth of the seabreeze and the speedwith (1935), Haurwitz (1947), Estoque (1962), and Frizzola which the sea breeze front moves inland. A rapid and Fisher (1963) have presented many examples increasein marine air and associatedmoisture in the illustrating this interdependence. valleys leads to a sudden decreasein heating and Along the Pacific coastof the United States,a unique subsequentlya decreasein coastal pressuregradients. combination of physiographic and oceanographic This diminishes the thermal forcing necessaryto main- characteristics strongly influence the local meteoro- tain a seabreeze as well as the northerly gradient flow. logical conditions during summer. The presenceof the It may even lead to a relaxation of coastal upwelling large sea level Pacific anticyclone dominatesthe large- which would further reduce coastal thermal gradients scaleair flow near the surface.Along the easternfringe and seabreeze forcing. At present, we have no data to of the high, the immediate inland areasreceive intense support these contentions but the ~ breezein an up- welling regimemay representa very important feedback 1 Contribution No. 89 of the GeophysicalFluid Dynamics mechanismbetween major oceanogra;phicand meteoro- Institute, F1orida State University. logical processeson a lafKer scale. 1268 JOURNAL OF APPLIED METEOROLOGY VOLUME 12 ~ ~w~.,!.," I ~ ., la~ i'l~.oo' f 114!1o' ~. I ..w.n . ..~..." ., ~o- I',.~ ..::. + ..-oO'+- r-m-- ., 1UTD .-r-:-~ ...? , o~ ,-, ~ -.1' . D~STA~ ~ ::~",;--- ~ C"W,T,lt,? ~PR£SSuRE SAI.IM . ..- 1 '. ~~ . TTEMPEh~ '- ' . ,,",\ 0 " tAI.IOIn I I 31AY. ,. ,.8AL _R8I~ -44"45 L---~l + + 44~+- ~~ ~~~~~' --- Iw.J'I (Wi' IWi' cp,W,T;Jtn.aw1 N- . .om -- -10 C . moMETER8 ~ ~ 5 10 , ~ . ~ D } 5. III. CORWWS ~TUTE MUS -44830'.- + . I . 4..w+-
84-
FIG.1. Map of caltlal ~ a.stal us showingme~ O~ ltaticms.
Most seabreeze studies made previously in this area the results of this study to those of previous investiga- have been in terms of the horizontal distributions of tions. The summary and conclusions are presented temperature and humidity at the surface emphA-~zing in Section 5. only the surfacewind field (Lowry, 1962,1966; Cramer and Lynott, 1961,1970). 2.The fteld observations It is the purposeof this study to attempt to evaluate The purposeof this sectionis to provide a description the character of the wnal wind var:iability on the of the special meteorologicalfield observationprogram central Oregon coast based on observations of a sea during a 42-hr period from 0500, 23 August 1972, breezeevent on 23 August 1972,at Newport, Ore. The through (XMX),25 August 1972 (all times PDT). These observationswere taken during the summer of 1972as observationsform the basis for the description of the part of the Coastal Upwelling Experiment (CUE I; seabreeze occurrence. see O'Brien, 1972), a project of the International Fig. 1 is a map of the CUE I area showing the land Decade of Ocean Exploration of the National Science stations and buoys at which meteorologicalobservations Foundation. The experiment represented an intense were taken during the summer of 1972. effort to explore the phenomenonof coastal upwelling. Although the major observationaleffort wasprimarily 4. Swface obsenlatioftS oceanographic,an important, though limited, meteoro- logical observation program was undertaken. These As a part of the overall CUE I meteorologicalob- observationsconcentrated on surfacewinds in order to servationprogram, five portable recordinganemometers determine the temporal and spatial wind stress pat- were installed along the coast to the north and south tern-the forcing function for the observed intense of Newport during August. Surface winds were also observed at the south jetty at Newport, and at five upwelling. The following sections of this paper will provide a surfacebuoys moored within 30 n mi of the coast. Air completedescription of a seriesof specialfield observa- temperature records were also available from these tions documenting a sea breeze event. Included are buoys and from Newport. Specialsurface temperature interpolations of the observedmesoscale changes in the and rdative humidity observationswere made during vertical structure of the lowest 4 km of the atmosphere 23 August at Ellmaker State Park and Corvallis to during the event. assistin the documentation of a seabreeze event. The field observations are described in Section 2. A complete analysis of the data obtained from the b. Aircraftobs~ field observationswith main emphasison a discussion The NCAR (National Center for Atmospheric Re- of the 23 August sea breeze event is contained in search, Boulder, Colo.) Queen Air aircraft, based in Section 3. Section 4 is devoted entirely to comparing Corvallis during the period 4-31 August, played an D~~BER 1973 ANDREW JOHNSON, R., AND JAMES J O'BRIEN 1269 important role in CUE I observations.In addition to 25 rNEWPORT AUG. 1972 V-COMPONENT measuring sea surface temperatureswith an infrared . . . . radiometer, the aircraft recordedBight level winds, air to . . . . temperature, and dew point temperature. Generally, ...... fiights were made at 500 ft along radial tracks from . . 15 . . Newport, extending 35 n mi seaward,and at 5(XX)ft ...... between Newport and Corvallis. In addition, the air- . . 10 . . craft made vertical soundingsof temperature and dew...... point via spiral ascentsand descentsover Corvallis, . . . . Newport, and at a point approximately 35 n mi WNW &: . . . . of Newport. . . . . ~ ~ Weather permitting, the low-level fJight tracks over ... ~ the ocean were flown during each aircraft flight. On xio 23 August, however, dense fog immediately offshore (which was later advected onshore) prohibited such -~ operations. Neverthel~, two short flights were made during 23 August in addition to two full flights on -10 24 August to supplement the documentation of atmo- . spheric structure during the observational period. -15 These flights produced valuable vertical soundingsof ~r ~ . - temperature and humidity but compassfailure within . - -20 - -{ . . the Doppler radar system preventedany useablewind . - observations. -25 :.. ~- ...... c. Pibal and rawinsondeobs~imtS .. 14. . 10a 14Ie 1810 I Through the cooperationof Dr. William Elliott and 10rNEWPORT Aue. 1972 the assistanceof Mr. Richard Egami, both of the School U-COMPONENT. . . . , . . TABLZ 1. Data summary 5 . ,.
W) A.. H -lI1 -I1U:e .,... ~ ~o .. Newport (SouthJetty) z b. FiYeIUrface buoys ~ 1. NH-I0 ~10 n mi wat of N~) I .:: . 2. NH-15 15 n mi west of Newport) -5 3. NB-20 20 n mi west of N~) . . . 4. DB-13 (13 n mi northwest of ~ Bay) , . . , ,J, ,/, . . . ~ . ~ ...... 5. Totem (25 n mi northwest of Depoe Bay) -~.. .4 .. . 10 II 84 H U 10 . B. A.irG'Gf' ~ .. Vertical 8O1mdiDgsto sooo ft FIG. 2. Time series of zooa1and meridiooal winds for Newport 1. Newport during 12-31 August 1972.The obecrvational period for this study a.. Aug. 23: 0045, 1'15 lies within the dotted lin5. b. Aug. ~,: 1015, 1615 2 . Corvallis .. Aug. 23: <»25, 1005, 1350, 1440 of Oceanographyat Oregon State University, limited b. Auc. 2': (1)55, 1630 use of a portable rawinsondestation (Weathenneaaure 3. OVa' ocean (35 n mi WNW of Newport) a. Aug. 2'; 1120, 1520 Corp., RD-6S) and two optical theodolites was made b. LeYeJ-8ight data (wind, temperature, dew point) possible.Since resources were limited, a 42-hr observa- 1. Corvallis-Newport (5000 ft only) &. Aug. 23: W29-(1)39, W52-1(xx), 1357-1406, 1426- tional program wasplanned. Someflexibility in plSLnning 1438 was possible, and 23-24 August was chosen as the b. Aug. 24: WS9-1 FIG. 3. SOO-mb contour analysis 101'the Pacific coast area 8Dalyzed at W m intervals. on 23 August prevented pibal observationsthere from 3. The 23 AUgust sea breeze event noon until 2(XX).Winds were available during this time, This seabreeze event was characterizedby a sequence however, from the 4-hr rawinsonde observations of severaldistinct occurrences.Although no character- describednext. istic cloud patterns were observed, a sea breezefront On 23 August, rawinsondeobservations were taken was distinguishable in the vertical structure of the every 4 hr at Newport, beginning at 0500 and ending zonal wind. The front moved rapidly inland to the after 0500 on 24 August. The rawinsondesensors were crest of the coast range of mountains after which it tracked semi-automaticallyby manual control of StTVo- slowed but eventually penetrated more than ro km motors controlling the orientation of a parabolic inland by 2 FIG. 4. Synoptic«ale _level presme anal'" for the Pacific ~t (after O'Brien, 1972). mately halfway into the observationalperiod. The low gradient flow, but it is only in the early stagesof thermal centeredin western Wyoming is a remnant of a major trough development through the interior that it sup- trough which was located some 300 km west of the ports the primary axis (O'Brien, 1972). coastlinefor more than 10 daysprevious to our observa- By 1700, the intense heating inland provides good tional period. During this time the surfacepattern for support for thermal trough development and the the Pacific coastwas dominatedby generallyvery weak primary trough axis becomes oriented north-south pressuregradients and weak westerly or southerly flow I through the interior valleys while the original axis near intemlpted briefly by occasional weak lows moving the south coast becomessecondary and is difficult to through the area. detect. The upper trough finally moved inland on 22 August while subsequentridging aloft behind the trough in- c. Crosssec;tions of 1M wiM field duced a rapid northeastward extension of the Pacific Primary evidenceof the seabreeze circulation on the High at the surface (Fig. 4). This extensionof the ridge central Oregon coast is expected to be found in the restoreda northerly flowI producing a suddenonset of diurnal variation of the zonal wind componentsince the upwelling along the coast. coast is orimted north-south. Vertical crosssections of the zonal wind field between b. Mesoscalesea le1'el pressure pattern Newport and Corvallis for 23 August are shown in The large..«;a1esubsidence due to ridging aloft during Figs. 6-9. Easterlies are given by dashed isotaclls, this event led to intense heating inland and develop- westerliesby solid lines, and the zero line is represented ment of a thermal low. This is seen at the surface by a dotted line. The vertical lines above eachstation (Fig. 4) as a northward extension of the California indicate the heights to which data were availablefor the thermal trough. This reduction of pressure inland analysis.V erticailines are dashedwhere no observation further increases the coastal pressure gradient and was made but the analysiswas computed on the basis subsequentnortherly flow along the ~n coast. of continuity from the time section for that station. The mesoscalepressure patterns dearly showthermal These cross sectionsshow that a sea breezefront is trough development in cen~ Oregon on 23 August distinguishable in the wind field and penetratesmore (Fig. 5). At 0800 the primary trough axis is positioned than 60 kIn inland while a distinct maximum in the closeto the coast. One reasonfor this occurrenceis a westerly flow behind the front increasesin magnitude decreasein relative vorticity of the northerly flow as it follows the front inland. The only indication of a ascending the Siskiyou Moun~ range near the related return flow in the circulation appearsto be some southern coast of Oregon (Capell, 1953). This effect increasein the depth of the easterliesabove the level of maintains a persistent trough axis near the south- maximum low level westerlies. westerncoast of ~n under the influenceof northerly The zonal wind component at approximately 0630 1272 'f! SURFACE L 1700POT ~.,' I "I 23 AUG72 ... ~:;. \ oj. '1- II' ... ., oi.~.. dO ... FIG. 5. Mesoscale sea level preaure analyses for the Oregon coast analyzed at I-mb intervals (after O!Brien, 1912). (Fig. 6, top) is easterly at all levels up through 3500m while the upper maximum is maintained at the same with two distinct maxima separated by a minimum height and intensity. at 2 kIn. At 0800 (Fig. 6, bottom), the lower easterly At 100) (Fig. 7, top), marked changesin the easterlies maximum has risen to 800 m and increasedto 15 kt have taken place, where for the first time, lo'91-level 1274 JOURNAL OF APPLIED METEOROLOGY VOLUME 12 I . ~ 4 2 .000 . of- _1 -t 4 t 3500 Wi 2 c w to- 2 ' .. ...0 !3000 -2- oJ i E --2 w ... -- > -2""- ~ 2500 . :;..-~ -4 c -~ --0- w WI -2 -e w -4- ~ 2000 -6- . C -8 to- I (-8 % -8 \ """"""" ., .. W 1500 % -6 ~- -4 ~ -4 :- -::::- 0 ":":'"~ ~-o20 1000 .0 -2- ... .. ... --.~.o'- -2 500 ... 0..' ... .. ;0" .2 2- .. '- ~ 4 .. .2 .. 6- ""'c':::;:::::::::::::::::~:~.~:~::~:::~::::::::::::::::::::::::::::::::~:::::::::::::::::~::::c.:.,.,. o""'c":"',c E cvo . POT 18)5 POT 1205 POT 10 20 30 40 ~ eo DISTANCE I"LAND (KMI FIG. 7. As in Fig. 6 except for late morning. 276 OURNAL OF APPLIED METEOROLOGY V w 8c .8 4000 I . .4 13500 t- - i ..f -""'--, -' :::=1 ..02 "".. .. I !,3000 4 y /" --- """""'--2 E-' 2 '/ _~4 . . ( . . . --' 2 . . ...~ 2' 1000 I- :... '00 2~ I --ELM cvo- *0 ~DT I~ ~T 1800 ~T DECEMBER. 1973 AN DREW JOHNSON, JR.., AND JAMES J O'BRIEN 1271 westerliesemerge. The easterlymaximum aloft has d. Time sectionsof thewind field rapidly decreasedin intensity and has split into a T. . . double maxima; one over Newport at 3200 m, and one . lIne sections for all stations were analyzed for each over Corvallis which has lowered to 2300m. The lower WInd component.These analysesmainly reiterated our easterly maximum is still rising in altitude and is now res~tS from the space sections except that distinct near 1200m and has decreasedto 9 kt. The upper and :n&:ximawere ~b~~ed ~ the easterlies between 1 e 0 rv mcreasem ow- ev no e lesIS observeddurin gust . deed typ . related to th b d th . . g 23-24 Au were m 1 cal e.sea reez.e~ to e.mcreasmgeast-west eventsunder similar synoptic conditions. pressuregradient. A bnef mcreasem the nor~erly fio,!! The casesused here were selected on the basis of 18observed near the surface at all three stations; this synopticsimilari close! . .d .th th ty of the large-scale surf ace pressure very y coma es Wl e onset of low-level pattern to that of 23-24 August A t tal f . westerliesbehind the seabreeze front Uohnson,1973). werechosen for dayswhen the P~cifi.coanti~cl~ec: DBCBKBER 1973 AN"DREW JOHNSON, JR., AND AMES j. O'BRIEN 1279 close to the Oregon coast with an established thermal N~""..g"T ~um '."7~ trough immediately inland. The morning soundings M£~N Z=N~L- IoIIN~ were an taken between 0930-1030 and the afternoon soundings between 1530-1650. Since the sample is small, the variances are frequently ~ oJ large for many levels. Emphasis in the discussion is MCANING E PACF"IL.E: therefore placed on differences between the morning K and afternoon soundings for each component. Fig. 11 shows that in the mean, the zonal wind participates in both the direct sea breeze low-level flow -"1 and a return flow. Also evident here is the fact that the ¥x transition betweenwesterlies and easterliesin the afternoon occws at the mean height of the inversion base (i.e., 900 m). , i 7 . f. Vertical and horisontal thermal structure u-ea...~aN£N" of_"." Although the level of the marine inversion (in the mean) restricts the depth of onshore flow of the sea breeze circulation, smaller scale variations in vertical thermal structure, including changesin the inversion itself, are influenced considerably during a sea breeze NEW~~~-r ~um ..ora event. ME~N ZaN~L "'IN~ Time sectionsof the vertical temperaturedistribution observedat Newport are discussedhere in addition to the horizontal surface temperature variations between NH-15 and Corvallis during 23-24 August 1972. ..,.TEA!'ICCN Fig. 12 contains the time sectionsof temperatureand PACF"IL potential temperature obtained from the Newport soundings.Stable layers are indicated where the struc- ture is vertically at least isothermaland laterally nearly isentropic. Of particular interest is that the onshoreflow (Fig. 10) takes place almost entirely below the baseof the inver- sion. These results differ considerably from' those of Edinger's (1959) Santa Monica study. These differ- u-C~M~aNCNT .~T.. ences,however, are accountedfor by the fact that the mountains in southern California extend above the FIG. 11. Vertical profiles of mean zonal wind at Newport for inversion. The sea breezeevent observedin this study selected mornings (0930-1030) and selected afternoons (1530- behaves more like that found by Williams and 1630) in August 1972. De Mandel (1966)in the San FranciscoBay area. Early in the day on 23 August, the structure is very forms between 200 and 700 m, the baseof which rises complex with the lowest 2 km containing four weak to a maximum height when the low-level westerliesare stable layers. A rapid increasein height of the upper at a maximum depth and low-level northerlies are at three layers occurs immediately following the onset of maximum strength (seeFig. 10). During this time the the sea breezeat ~. A single strong inversion layer inversion intensifiesin terms of the temperatureincrease TABLE 2. Inversion structure. Height of base Thickness aT/as MIas au/as (m) (m) [OC (100 m)-l] [DC (100m)-l] [% (100m)-l] ObI"'"August- 900 0.7 1.8 9.6 23 August ~ 200 500 0.5 0.2 8 1600 200 500 0.4 2.0 12 2200 700 200 1.7 3.3 15 24 August 0300 500 200 2.4 2.3 20 0800 ~ 300 1.0 2.3 17 1400 400 200 1.6 2.9 20 1280 JOURNAL Of AFPLIED METEOROtOGY VOLmlE 12 (S~3 .l3N) 13A31 ~3S 3AOa~ .lH913H S~3.L3W) '3A31 V'3S 3AO8V' .LH913H 0 0 0 0 0 0 0000000 0 0 0 0 0 In Oln 00 0 0 g .9) g g 0 g V If) 1f)C\I C\I!!!: - Qin- If>N N ~ 2~ 1: -r- [ , ""'C ~ t I ,.,. N .. .I I. ~ t- "1 :Jf I . , o- - ~ ) \ ~ I.j \ , !" ~ I i , ~ :J: i ~ "- o~ Off) M ~ ~i{({7 N '" t! 0 t) t; ~ ~ ~ Z 0 :) ~ ~ ~ ",01(- i~ ) ~ .8 u .- - - ... ~ '1 '8 ,:{ ~k,', , -~, .9 ... \ 0 C ), 1\ 6 , j - G ""-, /, .- C:\- " / O 8 j Q. OJ .., ... ~ ~ 1 I&J ; -2 ~C:\- O'- .9 ~ 0 ~ 11 ',of: 'f, g E . ] .. ~ ~ 0 ~: C:\- J\ - . , : 0 ~ '" ~ .g . I .1 v .- ~ U) OJ :) 8 " .~ .f "'~- ]"- '. . >OJ -N ci rZ 1\': .u 1,,\, ~ ~~ ...~. .. DECEMBER1973 ANDREW JOHNSON J- AND AMES J O'BRIEN 1281 124.5 124.0 '- I Ii I) Ii. 24 ~~T 1'7l. I 4: t (. ~- 1110p)"f J I : 1 ~.,. If . j \ . I k. r ~ "~ 14.(' ~ 45.0 II w ...S' . . //":;,1 . "A ! '" 'wi I" w K K "II " ~\ V I ~'" l48i 44.5 ~ 44.5 ~ , ..- ,~~ ~ ~.I- '-' .\ -" ? ~ I~ :- k /J CA 124.~ 124.0 FIG. 13. Sea surface temperature map for cstral Oregon ~t for morning of 24 AUIUSt 1972 (after O'Brim, 1972). with the height through it, to -3.3C (100 m)-l. From as the vertical gradients of both temperature and this point the inversion layer undergoes a change, relative hwnidity suddenly become approximately splitting and becoming more complex; but the main twice that of the mean. layer of high stability descendsto 500 m as low-level A vertical time section analysisof relative humidity westerlies subside and a brief land breeze begins for this period showsthat the top of the marine layer (Fig. 10). At ~ on 24 August, the inversion again extends above the base of the lowest inversion layer briefly risesat the onset of the seabreeze. Uohnson, 1973). However, later in the period as the Table 2 summarizesthe structural changesobserved inversion layer intensifLes,the top of the moist layer at Newport in comparison with the mean structure coincidesalmost exactly with the inversion base. In a (NelDurger et al., 1961) of the marine inversion for similar study in southern California, Edinger (1963) August. Although the height of the inversion varies observed that the top of the marine layer generally considerably during 23-24 August 1972, it is con- extendsabove the inversion base. sistently lower than the mean. Before 2200 on A definite pattern of diurnal variability of the marine 23 August, the thickness, intensity and vertical inversion cannot be distinguishedhere, but it is noted humidity gradients are all very close to the mean. At that there appearsto be an increasein height in response 2200, the thickness decreasesto half that. of the mean to the sea breeze onset. This is physically reasonable ~ 1282 JOURNAL OF APrL(ED METEOROLOGY VOLUIIE12 oe NH-15 NH-IO NPT -'-'-- NH-IO NPT ELM ... '" CVO . . . ~I ~ 0'" r ..r) .1\, , ~~. \ \ 10 , ELM . cw-x~ t . .'. , --J. ~ ."'/ Q " i \ I :" ". ~ _i ""'., bJ 16 \ ' ".j !:", I t-N .- -- 12 -- 15 .:-ELM. ~NPT. CYO I - /"'" I ...' .- 08 "I' . -- I --' , ~ .x ", C\'O 041.i i NPT J4 16 18 20 22 24 a TEMPERATURE(ec) - FIG. 14. Time seriesof surface air temperatures oblerved on a line perpendicular to the coast, 23-24 August 1972. and perhaps expecteddue to low-level convergenceat 4. Summary and conclusions the seabreeze front. A sea surface temperature map (from the NCAR Although detailed observations were made during Queen Air radiometer data) for the morning of 24 only a singlesea breeze event, there are a few important August 1972 (Fig. 13) shows a representativesurface characteristicsof the 23 August event: seawater temperaturedistribution during the seabreeze 1) The low-level onshore flow of the land-sea breeze observational period (O'Brien, 01972).Of particular circulation at the coast is contained entirely within interest is the fact that the coldest water lies within the marine layer. 10 n mi of the coast. 2) The return flow above the inversion appearsto be Fig. 14 contains a time seriesof surfaceair tempera- in the form of impulses or surges.These appear to tures observedat the three land stations as well as two be in responseto the surges observed in the sea buoys. The temperature curves indicate the possible breeze. existenceof two scalesof thermal forcing. On one scale 3) A distinct wind maximum follows the sea breeze (between NH-15 and Corvallis) the temperature front inland. difference ranges between approximately 2C and 11C 4) At the coast, the marine layer appearsto deepenat with a mean near 7C. On a smaller scale (between the onset of the seabreeze. NH-10 and Newport) the temperaturedifference ranges between approximately -2C and +5C with a mean Any influence of the coast range of mountains is not near 1C. Thus, the larger scaleof thermal forcing exist$ evident. The role of the slope winds would be in phase betweenthe open oceanand the interior valley with a with the sea breeze on the western-slopes but out of temperature gradient of 7C (100 kmr1 and a smaller phaseto the east. This effect may have beenmanifest, scaleforcing exists due to diurnal surface heating and in ~, in the observed rapid movement of the sea coolingof the land mass,causing an intensetemperature breeze front between Newport and F.lIm:LKer.The gradient near the coast [as high as 5C (20 km)-l]. expected influence is small since the average terrain DECEMBER 1973 ANDREW OHNSON, JR.. AND JAM~S O'BRIEN 1283 height is only 2000 ft and the crestline is oriented A. Johnson submitted to Florida State University, north-south. Department of Meteorology. The contribution of the Conolis effect on this event is not immediately evident either. No typical clockwise REFERENCES elliptical rotation of the surfacewind vector (Haurwitz, Blackadar, A. K., 1957: Boundary layer wind maxima and their 1947) could be detected in our hodographs. Some significance for the growth of noctuma.l inversions. Bull. consistentveering of the surfacewind was observedat Amer. Meteor. Soc., 38, 283-200. Newport but a Coriolis contribution could not be Capell, J. C., 1953: Mechanics of the Califomia.oregon heat low. Paper presented at Fire Weather Coni., U. S. Forest Service, distinguished from a very strong acceleration of the Portland, Ore. northerly gradient flow throughout the observational Cramer, D. P., and R. E. Lynott, 1961: Cross-sectionanalysis in period. the study of wind flow over mountainous terrain. Bull. Amer. From this study, some insight is gained into the Jldeor. Soc., 42, 693-702. understanding of mesosCalevertical structure of the -, and -, 1970: Mesoscaleanalysis of a heat wave in western Oregon. J. Appl. Meteor., 9, 740-759. atmospherein an upwelling regimeduring a seabreeze Defant, F., 1951: Local winds. ComjlmdJillm of Mdeorology, event. The obvious limitations of such a small sample Boston, Amer. Meteor. Soc., 655-672. and the inadequate understanding of the mesoscale Edinger, J. G., 1959: Wmd structure in the lowest 5 kIn over Santa mechanismof the seabreeze on the Oregoncoast serve Monica, Calif. Final Rept., Part L, Dept. of Meteorology, University of California at Los Angeles. to emphasizethe need for further investigationsof this -, 1963: Modifications of the marine layer over coastal southern nature. California. J. Ajlpl. Meteor., 2, 706-712. Estoque, M. A., 1962: The sea breeze as a function of the pre- Acknuwledgmenis.This is a contribution to the vailing synoptic situation. J. Amos. Sci., 19, 244-250. Coastal Upwelling Ecosystems Analysis Program Flohn, H., 1969: Local wind systems. World Swwy of Clim(IJIJogy, (CUEA), National Science Foundation Grant Vol. 2, New York, Elsevier, Chap. 4- GX-33SO2.Support for this work has beenprovided by FrizoIla, J. A., and E. L. Fisher, 1963: A series of sea breeze ob- servations in the New York City area. J. Ajlpl. Meteor., 2, the Office of Naval Research, the Oceanography 722-739. Section of the National ScienceFoundation (Grarit Haurwitz, B., 1947: Comments on the sea breeze circulation. GA29734), and the International Decade of Ocean J. Meteor., 4, 1-8. Exploration of NSF (Grant GX-28746). This is a Johnson, A., 1973: An investigation of a sea breezeevent on the central Oregon coast in August 1972. M.S. thesis, F1orida contn"butionto CUE (Coastal Upwelling Experiment). State University, 61 pp. Sincerest appreciation is extended to Drs. D. W. Koschmieder, H., 1935: Der Seewindevon Danzig. Meteor. Z., 52, Stuart, C. L. Jordan, R. C. Staley, R. Smith and 491-495. W. Elliott for their recommendationsand consultation. Lowry, W. P., 1962: The sea breeze of northwest Oregon and its Many thanks are also offered to Richard Egami, influence on forestry operations. Ph.D. thesis, Oregon State University, 162 pp. Jerry Burdwell, Clay Creech, Richard McNider, -,1966: The sea breeze: An important factor in the air pollu- Dennis Elliott, Cleveland Holladay and Monty Peffley tion meteorology of the Pacific northwest. Paper presentedat for their assistancein collecting and processingthe data. Annual Meeting, Air Pollution Control Assoc.,Pacific North- The portable rawinsonde station and two optical west International Section, Seattle, 10 pp. Neiburger, M., D. Johnson and C. Chien, 1961: The inversion theodolites were borrowed from Dr. William Elliott of over the eastern north Pacific Ocean. Part I, Studies of the Oregon State University (NSF Grant GA31141). structure of the atmosphere over the eastern Pacific Ocean Another optical theodolite as well as a part of the in summer. U";v. Calif. Publ. Jldeor., 1,94 pp. expendables used in the pibal observations were O'Brien, J. J., Ed., 1972: CUE I MeteorologicDlAIlas, VoL 1. contributed by Mr. Jerry Burdwell (Advisory Seattle, University of Washington, 310 pp. Williams, W. A., and R. E. DeMandel, 1966: Land-eeaboundary Meteorologist, NOAA, National Weather Service). eft'ectson smal1scale circulation. Prog. Rept. No.2, Dept. of This research is derived from a M.S. thesis by Meteorology, San Jose State College, 97 pp.