Meteorol. Atmos. Phys. 38, 185-194 (1988) Meteorology,and Atmospheric

Physicscg by Springer-Verlag 1988

551.588.7: 551.515.1

Department of Meteorology, San Jose State University, San Jose, California, U.S.A.

Case Study of Urban Interactions with a Synoptic Scale Cold Front

D. Gaffen* and R. D. Bornstein

With 7 Figures

Received January 20, 1987

Summary

A two-day test period (10-11 March 1966) during which aslow moving synoptic cold front passed over New York Cityhas been analyzed. As the front passed over the city it wasdestroyed near the surface by the urban roughness effect. The.upper segment of the front passed over the city and rejoinedthe rest of the front downwind of the city. Evidence for theabove phenomenon was seen in both the pibal wind andhelicopter (temperature and SOz) soundings.

Distortion of the front forced polluted surface urban airupwards, as within the warm sector of an occluding synopticfrontal system. The outward spreading of this air aloft pro-duced increasing concentrations over the city at heights above200m.

1. Introduction

The research of Helmut Landsberg provides majorcontributions in many areas of climatology; oneof the most important is in the field of urbanclimate. Most of the urban climate studies dis-cussed in his comprehensive book The Urban Cli-mate (Landsberg, 1981) were comparisons of con-current climatic elements at sites within a city withthose at locations in its surrounding environs.

The problem with such comparisons is that itis hard to estimate the magnitude of the micro-climatic differences that would exist between thetwo sites in the absence of the urban area. Prof.Landsberg was able to avoid this problem in his

* Current Affiliation: National Oceanic and AtmosphericAdministration, Rockville, MD 20852, U.S.A.

unique study of the climate effects of urbanizationresulting from construction (from scratch) of theplanned community of Columbia, Maryland(Landsberg, 1979).

The work reported in this paper discusses theretarding effects on the movement of a synopticscale cold front caused by the increased surfaceroughness of New York City (NYC). When it wassuggested to Prof. Landsberg that this was thefirst time that such an effect had been observed,he thought for a very short time before remem-bering a Ph.D. Thesis written some 50 years be-fore, when he was a student in Germany. Thatstudy had used data from a precipitation networkto plot isochrones of precipitation initiation dur-ing a synoptic frontal passage over an urban area.When the results showed a later starting time overthe city center, the student concluded that the in-creased urban surface roughness had retarded thefrontal movement over the city. The conclusionfrom this is that, at least when dealing with Prof.Landsberg, there are very few new and originalresearch ideas.

2. Background

Surface urban heat islands induce updrafts overa city, which in otherwise calm conditions produceconvergent country winds. Observations of com-plete circulation cells (including diverging winds

186 D. Gaffen and R. D. Bornstein

aloft and downward motion outside the city) arerare, because such a circulation may resemble "themotions of an amorphous, slowly-pulsating jel-lyfish" (Munn, 1970).

With higher general wind speeds, heat islandformation is inhibited, and heat island inducedflows less likely to be observed (Bornstein andJohnson, 1977). However, cities can also modifymesoscale and synoptic scale flow patterns, e.g.,Bornstein and Johnson showed surface winds de-celerated during non-heat island periods in NYCdue (to the large urban surface roughness) andaccelerated during low speed heat island periods.

Sea breeze fronts have also been observed todecelerate at the surface as they move over urbanareas, e.g., in Boston (Barbato, 1978) and NYC(Bornstein etaI., 1988). The NYC decelerationproduced a steepening of frontal slopes over thecity.

Likewise, Loose and Bornstein (1977) foundsurface synoptic frontal movement over NYC re-tarded due to friction during non-heat island pe-riods. However, during heat island periods frontalmovement was retarded over the upwind half ofthe city and accelerated by the heat island over itsdownwind half.

Lower pollutant concentrations generally ac-company onshore sea breeze winds (Harrison andMcCartney, 1980), but sea breezes can increaseconcentrations when they return pollutants car-ried offshore by the previous nocturnal land breeze(Shair et aI., 1982). The NYC sea breeze bringsdecreasing surface sulfur dioxide concentrationsto coastal stations in NYC and increasing con-centrations to those further inland (Bornstein andThompson, 1981). The decreasing concentrationsresult from initial onshore advection by the seabreeze. When the front stalls over the city due toits increased surface friction, the marine air be-comes polluted. Its eventual advection inlandcauses increasing concentrations. These changeswere found to extend several hundred meters into

the urban boundary layer by Gaffen and Bornstein(1988).

Synoptic frontal passages also influence urbanpollutant concentration patterns, e.g., low windspeeds and shallow mixing depths associated witha quasi-stationary front caused high pollutantconcentrations in NYC in January 1971 (Nudel-man and Frizzola, 1974). Concentrations rapidlydecreased when the front finally passed through

the area. In general, cold frontal passages throughNYC are associated with decreases in surface con-centrations in Manhattan and increases to the eastand west (Bornstein and Thompson, 1981). How-ever, the one highly distorted front in the studycaused increased surface concentrations in Man-hattan, suggesting that it never truly passedthrough the city at the surface.

Previous studies have either investigated sur-face sea breeze or synoptic frontal movement overNYC, or have analyzed the response of the pol-luted PBL over NYC to sea breeze frontal passage.The current study will analyze the response of thepolluted PBL over NYC to a slowmoving synopticcold front passage.

3. Data Base and Analysis

The New York University (NYU) Urban Air Pol-lution Dynamics Project of 1964-68 (Davidson,1967; Bomstein et aI., 1977a, b) collected surfaceand boundary layer wind, temperature, and SO2concentration data in the NYC area. The datahave been used in previous observational andmodeling studies of various aspects of the pollutedurban coastal boundary layer over NYC, e.g., heatislands (Bomstein, 1968), a two-dimensional plan-etary boundary layer (PBL) model (Bprnstein,1975), surface winds (Bornstein and Johnson,1977), surface synoptic fronts (Loose and Bom-stein, 1977), surface SO2 concentrations (Bom-stein and Thompson, 1981), atmospheric moisture(Clark et aI., 1985), three-dimensional pollutedboundary layer model (Bomstein et aI., 1985a, b;Pechinger et aI., 1985), sea breeze frontal move-ment (Bornstein et aI., 1988), and vertical structureof a polluted PBL during a sea breeze frontalpassage (Gaffen and Bomstein, 1988).The currentstudy uses the data set to investigate effects of theheat island and a synoptic cold front on the struc-ture of the polluted coastal urban boundary layerover NYC during 10-11 March 1966.

The period was selected for analysis because ofits interesting meteorological conditions and highdata density. Mesoscale streamline analysis wereconstructed for the area around NYC using hourlyaverage wind data from a 97-site anemometer net-work. The synoptic cold front, observed on the11th, was identified as a wind shift area in theanalyses; frontal zones were depicted by lines rep-resenting the best estimate of their leading edge.

74° 15'

Case Study of Urban Interactions with a Synoptic Scale Cold Front

73°45'

41°00'

40°45 '

40° 30'

Fig. 1. New York City area and datacollection sites 74°15'

Frontal advance speeds were computed from mea-sured distances travelled by the front at variouslocations during consecutive hourly periods. De-tails of the data and analysis can be found in Looseand Bornstein (1977).

About 80 single theodolite piballaunches weremade during 10 and 11 March at two sites, i.e.,Research Building 4 (RB 4) and NYC (Fig. 1).Wind speed and direction values were obtained at37.5 m intervals in the lowest 1000 m of the at-mosphere (assuming a constant rate of balloonrise of 150 ill min ~ 1). Values were smoothed usinga 3-point equally weighted running mean.

Speed and direction height-time sections wereconstructed for both days at both pibal launchsites. Unreasonably high wind speed values(> 25 m s ~ I) were assumed associated with erro-neous observations. Isopleth smoothing removedhigh frequency disturbances, i.e., those with time

187

74°00'

NEW JERSEY

40°45 'QUEENS

. Helicopter Soundings. Pibal Launch Sites

0 NWS Sites

79th Street

74°00 ' 73°45 '

scales less than 2 hr and height scales less than200 m. Fronts were identified as regions of max-imum directional shear and minimum windspeeds. Details of this analysis can be found inGaffen (1984).

Temperature and SO2concentrations from nearthe surface to about 1000m were obtained fromabout 50 urban helicopter soundings during lO-II March (Fig. 1 and Table 1). Climbing traversesand spiral descents (at approximately 35m s- I)

were made at sunrise, sunset, and/or midday. Thesemiconductor temperature sensor had a 0.2°Crelative accuracy, 0.5°C absolute accuracy, and0.2 s time constant. The pressure-height unit, twoaneroid cells driving a potentiometer, had a timeconstant less than 0.05 ms and an accuracy ofabout 10m. The electro conductivity SO2unit, cal-ibrated to negate interference from abient CO2,had a 30 s time constant and probable accuracy

188 D. Gaffen and R. D. Bornstein

Table 1. Data Sites Shown in Fig. 1

Name Indicator

National Weather Service SitesAmbrose LightshipCentral Park

Pibal Launch SitesNYU Tech.Research Building 4

Helicopter Sounding SitesBattery ParkCypress Hills ReservoirCloistersEastchester BayEllis IslandEast River Park

Fort Washington ParkGovernor's IslandGravesend BayNarrowsNarrows BridgeNewton CreekOrchard BeachStatue of LibertyVan Cortlandt Park

Williams berg Bridge40th Street and New Jersey40th Street155th Street

ALCP

NYURB4

BATCHRCLOECBElLERP*FWPGmGVBNAWNBGNCKOBCSOLVCPWBB*40NJ40th155

* Almost coincident.

of 10-30%. Criteria for smoothing sounding dataare described in Bornstein et al. (1977 a).

Surface SO2 concentration were measured byelectro conductivity and wet chemistry devices atfixed sites and mobile laboratories. Effects offron-

tal passage on PBL concentration profiles weredetermined bvy computing concentration differ-ence profiles, L1S( z), using pre- and post-frontalhelicopter soundings at the same sites. Frontalpassage time at an individual sounding site wasdetermined from sea breeze surface frontal posi-tions.

Vertically averaged concentration changes wereobtained by height averaging each L1S(z) curve.Spatial distributions of these vertically averagedvalues were then compared to similar distributionsof surface values for approximately the same lo-cations and time periods obtained by Bornsteinand Thompson (1981).

Frontal slopes over NYC were calculated (usinghelicopter temperature soundings, pibal winds,

and/or previously analyzed surface frontal posi-tions) by three techniques. In the two techniquesinvolving helicopter sounding data, fronts weredefined by an elevated inversion base and/or asharp change in SO2concentration. The SO2 sen-sor has a greater time constant than the temper-ature sensor, so temperature took precedencewhen the two positions did not coincide.

The first of the two helicopter-sounding basedtechniques for determining frontal slope usedfrontal height aloft values versus perpendiculardistance from the helicopter sounding site to theinterpolated surface frontal position. The slope ofthe best fit (linear regression) line through all theheight aloft data points was taken as the frontalslope. Thus this first technique produces onespace-averaged frontal slope value from a seriesof single frontal height values at various sites.Withtwo inversions at a single site, an average valuewas used.

The second of the two methods for computingfrontal slope using helicopter sounding data in-volves two concurrent frontal positions, one aloftand one at the surface (an interpolated positionfrom the frontal isochrone analyses). The slopewas then defined as the ratio of the frontal heightaloft to the perpendicular horizontal distance be-tween the site and the surface frontal position.Thus this technique yields one slope estimate persite at a given sounding time.

The third (and final) technique determinedfrontal slope at each of the two sites for whichpibal wind time sections were constructed. Frontalposition at various times (and therefore at differ-ent heights at the same site) were assumed to cor-respond to areas of wind speed minima and di-rectional shear maxima. Slopes (dz/ds) were com-puted by dividing the slope of the line connectingthe frontal positions at the site (dz/dt) at differenttimes by the average wind speed at the front (ds/dt), assuming equality of the frontal advance andatmospheric wind speeds. Because of this as-sumption, frontal slope estimates obtained at thetwo pibal sites by this technique are the least ac-curate.

4. Results

Following three days of fair weather, a weak coldfront entered the test area on 11 March 1966

(Fig. 2). Mesoscale surface frontal positions

"'

~

os/

00- -

CALM JI

II

'!"

I00

"-

os

-l ," on--."

Fig. 2. Anemometer network (dots), and surface streamline and isotach analysis (mph) for 0800 EST on II March 1966 (from Loose and Bornstein, 1977)

"",.", ~

'"

",.:j'"'",:.n -

ON

(JP'IZ>(1)IZJ8"p..'<0 ,c...,crpo::;-::;.-+(1)...,po(').-+o'::;IZ>;5..-+::rP'IZJ'<::;0~o'IZJ(')po(D(J0p:'TI...,0::;.-+

...-00\D

190 D. Gaffen and R. D. Bornstein

0'100

0500

1100

1100

'~OO

Fig. 3. Synoptic surface frontal isochrones (EST) on 11 March 1966 (from Loose and Bornstein, 1977)

(Fig. 3) from Loose and Bornstein (1977) show afrontal movement of 100km in 11hr, yielding anaverage frontal advance speed of only 2.5m s- 1.This slow frontal movement, and the light andvariable post-frontal surface winds, allowed thelarge urban surface roughness to retard the move-ment of the surface front over the most built-uparea of the city, i.e., Manhattan. Thus by 0800EST the surface frontal shape was greatly dis-torted, as its speed of movement over NYC wasnearly zero.

Urban surface roughness also affected verticalfrontal structure; analyses of the pibal wind andhelicopter soundings suggest that the surface frontnever passed Manhattan. The upper segment ofthe front over the city was "torn off' from itssurface section. The upper segment then "rodeover" the city, subsequently (by 0900 EST) re-joining the surface front segments that had con-tinued moving southward in the area both eastand west of Manhattan. The surface frontal frag-

ment which remained stagnated and loopedaround Manhattan eventually dissipated. A sim-ilar effect at mountain ranges was first describedby Bjerknes and Solberg (1921).

Evidence for the above phenomenon is seen inboth the pibal wind and helicopter soundings. Pi-bal wind patterns on the non-frontal day are con-siderably less complicated than on the frontal dayand illustrate general PBL flow characteristics(Gaffen, 1984). On the non-frontal day winds atboth pibal sites veered with height in accordancewith Ekman theory. Nocturnal jets formed at bothsites within the hours of midnight at an averageheight of 500m on each test day (Figs. 4 and 5).Maximum speedsvaried between6 and 16m s- I,and averaged II m S-I.

Frontal passage on 11 March complicated thispattern. At NYU (Fig. 4), frontal passage causedwinds to veer from westerly to northerly between0900 EST (at 350m) and 1100 EST (at 750m).Thus frontal passage at these levels occurred 2.5

cwo

0800

0900

1000

1100

11.D0

NYU DIRECTION

Case Study of Urban Interactions with a Synoptic Scale Cold Front

11 MARCH 196611 MARCH 19661000

750

27

:Jen::?;~Q)

-:;;500.5~co"ijj:J:

250

{34

191

1000NYU SPEED

142 8 6 4

1 10'\ , ,, I I. I ,I I II I ,I I II I I, I ,I I ,, I ,I , ,I ,I ,

/ 'II

16

2

2:Jen::?;

:2 2

:.€Q)

-:;;500.s2

~co"ijj:I:

n2

2

12 18 24 00 06 12 18 24

Time (LST) Time (LST)

Fig. 4. Wind speed (m S-l) and direction (tens of degrees) time sections at NYU for 11 March 1966. Pibal soundings (solidarrowheads) and surface frontal passage (open arrowhead) are shown

and 4.5 hr, respectively, after the 0630 EST surfacefrontal passage in this area (Fig. 3).

At RB 4, near surface (pibal) wind speeds wereless than 2 m s- 1 as the surface front passed at0800 EST (Fig. 5). Passage at the 350m level oc-curred only about an hour later, indicating asteeper slope at RB 4 than at the more upwindNYU site.

Upper level progression of the frontal towardsthe urban center, in conjunction with its surfacestagnation, first produced a totally vertical slopeand then a negative one. In such a situation coldair overlays warm air, resulting in vertical mixing.

Singular points, with 1800 direction shifts inassociation with zero wind speeds, have been as-sociated with vertical mixing (Ackerman, 1974).Such points do appear in the post-frontal isogonanalysis at RB 4 (Fig. 5) due to increased convec-tion associated with the frontal "tear". The eighthour post-frontal pibal data gap due to precipi-tation at RB 4 makes this interpretation somewhattenuous; nevertheless, rain fell earlier and for a

longer period at RB 4 than at NYU, suggestinggreater convective activity at the former site.

Helicopter SO2 soundings provide further evi-dence for this near surface frontal "tear" and ref-ormation. Frontal passage brought either de-creasing or slightly increasing SO2concentrationsbelow 200 m (Fig. 6) at all helicopter soundingsites, except GID where they increased, dependingon the degree of urbanization under the surfacetrajectory advecting post-frontal air to a particularsite (Fig. 2). This pattern is consistent with theconcurrent surface SO2 analysis of Bornstein andThompson (1981). They found surface concentra-tion decreases over most of the area, and increasesonly in a small area centered at GID and parallelto (and within) the looped segment of 0800 ESTsurface frontal position (Figs.2 and 3). The airwithin this loop was not replaced by post-frontalair as the surface front never passed through thatarea.

This analysis also explains the concentrationincreases above 200 m at all sounding sites (Fig. 4).

~

192 D. Gaffen and R. D. Bornstein

SPEED1000

RS 4 DIRECTION11 MARCH 1966

:J(f):::;:

30 27

~Q)

Q; 500S.s::'"'0;I

250

06

03

RS 4 11 MARCH 19661000

:Jen:::;:

4 4

~Q)Q; 500S.s::'"'0;I

12

09

6

12 18 24 00 06 12 18 24

Time (LST) Time (LST)

Fig.S. Wind speed (m-I) and direction (tens of degrees) time sections at RB4 for 11 March 1966. Pibal soundings (solidarrowheads) and surface frontal passage (open arrowhead) are shown

800

600

-ElL---FWP-GID--155E

~ 400N

200

0-0.2 -0 I 0 0.4

~s (ppm)Fig. 6. Change with time in SO2 concentration through PBLdue to frontal passage on 11 March 1966

As the surface frontal loop was closing inward,polluted surface urban air was forced upwards, aswithin the warm sector of an occluding synopticfrontal system. The outward spreading of this airaloft produced increasing concentrations aloft atall sites (within and outside of the loop).

Frontal slope estimates provide yet further evi-dence for the steepening and destruction of the

near surface front. Surface frontal positions andfrontal heights aloft (second technique describedin Part 3) combined to yield slope estimates be-tween - 1 : 1and 1: 110(Table 2). Extremely steepslopes of l: 7 and l: 2 were computed for theearliest soundings (about 0700 EST), when frontalheight above these stations was low. By 0752 EST(at NCK), the cold air had overrun the warm air,producing a negative slope. After 0905 EST, thefrontal slope had an average value of 1 :73. Thusthe re-formed near surface front was significantlyless steep than before its tear.

Linear regression, using helicopter soundingdata at about 1000 EST (first technique in Part2), yielded a slope of 1 :60 in the layer between250 and 700m, with a correlation coefficient of- 0.90 (Fig.7). Pibal wind data (third technique)yielded frontal slopes of 1 : 53 and 1:60 at RB 4and NYU, respectively in the 350 to 700m layer,in good agreement with both the linear regressionresult and the near surface slopes of the re-formedfront. The nearly uniform slope of the re-formed

.,... ,'«

Case Study of Urban Interactions with a Synoptic Scale Cold Front

800

0155

0 Single

l> Multiple

0 Average

600

-5

l-I 400(!)

WI

l>

l>

200

00 10 20 30

DISTANCE (km)

Fig. 7. Frontal inversion heights versus horizontal distanceat about 1000 EST on 11 March 1966. Regression line isthrough single inversions heights (circles) and average(squares) of twin inversions (triangles)

front near the surface and aloft indicates that fric-tional effects are less important in the downwindnon-urban area.

5. Conclusion

A weak, slow moving synoptic scale cold frontwas highly distorted in three-dimensions as itpassed through the PBL over NYC. Urban surfacefriction greatly distorted the surface frontal shapeby reducing its speed of movement over Manhat-tan to a nearly zero value. The roughness effect

193

steepened the frontal slope until a negative sloperesulted when the cold air over-rode the warm air.Then the upper segment of the front over the citywas "torn off" from its surface section and "rodeover the city". This section finally rejoined thesurface frontal segments that had continued mov-ing southward in the areas both east and west ofManhattan.

Evidence for the above phenomenon was seenin both pibal wind and helicopter (temperatureand SO2)soundings. The helicopter SO2soundingsshowed either decreasing or slightly increasing SO2concentrations below 200 m at all sites, except theone within the looped segment of the front re-maining around the southern half of Manhattan.Surface concentrations within the loop did notdecrease, as the surface front never passed throughthat area and this air was not replaced by post-frontal air. In addition, as the surface frontal loopwas closing inward, polluted surface urban air wasforced upwards, as within the warm sector of anoccluding synoptic frontal system. The outwardspreading of this air aloft produced increasing con-centrations at heights above 200 m at all sites.

Acknowledgements

The authors would like to thank John Chamberlain and NickPowell for their analyses of wind time sections, Ms. DonnaHurth for typing the manuscript, and Lynn Baxter-Poh1 fordrafting the figures.

40

References

Ackerman, B., 1974: Wind fields over the St. Louis Metro-politan Area. J. Air Poll. Control Assoc., 24, 232-236.

Barbato, J. P., 1978: Areal parameters of the sea breeze andits vertical structure in the Boston Basin. Bull. Amer.Meteor. Soc., 59, 1420-1431.

Bjerknes, J., Solberg, H., 1921:Meteorological conditions forthe formation of rain. Geofys. Publ., 2, 60 pp.

Bornstein, R. D., 1968: Observations of the urban heat islandeffect in New York City. J. Appl. Meteor., 7, 575-582.

Bornstein, R. D., 1975:The two-dimensional URBMET ur-ban boundary layer model. J. Appl. Meteor., 14, 1459-1477.

Bornstein, R. D., Johnson, D. S., 1977: Urban-rural windvelocity differences. Atmos. Env., 11, 597-604.

Bornstein, R. D., Morgan, T., Tam, Y., Loose, T., Leap, K.,Sigafoose, 1., Berkowitz, c., 1977a: New York air pol-lution project of 1964--1969: Description of data. EPAReport No. 600/4-77-035A, 134pp. .

Bornstein, R. D., Morgan, T., Tama, Y., Loose, T., Leap";K., Sigafoose, J., Berkowitz, c., 1977b: New York airpollution project of 1964--1969:The data. EPA. ReportNo. 600/4-77-035 B, 213 pp.

Table 2. Frontal Slopes on 11 March 1966

Site Time Height Distance Frontal(EST) (km) (km) Slope

155 0707 0.19 1.2 I: 7FWP 0711 0.20 0.5 1: 2NCK 0752 0.40 -0.5 -1: 1155 0905 0.50 29.8 I: 60FWP 0910 0.47 31.5 1:6740th 0917 0.43 23.8 1: 55ElL 0930 0.27 19.5 1: 72GID 0935 0.34 18.3 I: 54CHR 0953 0.24 26.5 1: 110CHR 0959 0.32 27.8 1: 88FWP 1053 0.61 48.3 1: 79

194 D. Gaffen and R. D. Bornstein: Case Study of Urban Interactions

Bornstein, R. D., Thompson, W. T., 1981: Effects of fric-tionally retarded sea breeze and synoptic frontal passageson sulfur dioxide concentrations in New York City. J.Appl. Meteor., 20, 843-858.

Bornstein, R. D., Klotz, S., Pechinger, U., Street, R., Miller,R., 1985a: Modeling the polluted coastal urban environ-ment. Vol. I: The PBL model. Final Report EPRI Project1630-13.

Bornstein, R. D., Klotz, S., Pechinger, U., Salvador, R.,Street, R., Shieh, L. J., Ludwig, F., Miller, R., 1985b:Application of linked three-dimensional PBL and disper-sion models to New York City. Preprint Vol. 15th NATOICCMS Conference on Air Pollution Modeling, St. Louis,MO., 22pp.

Bornstein, R. D., Fontana, P. H., Anderson, S. F., 1988:Observations of urban effects on sea breeze frontal pas-sage over New York City; submitted to J. Appl. Meteor.

Clarke, E. C., Bornstein, R. D., Tam, Y. T., 1985: Currentand potential anthropogenic moisture effects on NewYork City PBL. J. Air Pollut. Control Assoc., 35, 831-835.

Davidson, B., 1967:A summary of the New York Urban AirPollution Dynamics Research Program. J. Air. Poll. Cant.Assoc., 17, 154-158.

Gaffen, D. J., 1984: Three-dimensional meteorological andsulfur dioxide patterns in an urban environment duringsea breeze and synoptic frontal passages. M.S. Thesis,Dept. of Meteor., San Jose State Univ., 72pp.

Gaffen, D. J., Bornstein, R. D., 1988: Observation of a seabreeze frontal passage through a polluted urban boundarylayer. Submitted to J. Appl. Meteor.

Harrison, R. M., McCartney, H. A., 1980:Ambient air qual-ity at a coastal site in rural north-west England. Atmos.Env., 14, 233-244.,

Landsberg, H. E., 1981: The Urban Climate. New York: Ac-ademic Press, 275pp.

Landsberg, H. E., 1979: Atmospheric changes in a growingcommunity (the Columbia, Maryland experience). UrbanEcology, 4, 53-81.

Loose, T., Bornstein, R. D., 1977:Observations of mesoscaleeffects on frontal movement through an urban area. Mon.Wea. Rev., 105, 563-571.

Munn, R. E., 1970: Airflow in urban ares. Urban Climates.WMO Tech. Note 198, WMO No. 254, T. P. 141, 15-39.

Nudelman, H. I., Frizzola, J. A., 1974: An air pollutionincident due to a stationary front. J. Air Poll. Cant. Assoc.,24, 140-144.

Pechinger, U., Salvador, R., Bornstein, R., Shieh, L. J., Lud-wig, F., 1985: Modeling the polluted coastal urban en-vironment. Vol. II: The dispersion model. Final Report,EPRI Project 1630-13.

Shair, F. H., Sasaki, E. J., Carlan, D. E., Cass, G. R:, Goodin,W., R., Edinger, J. G., Schacher, G. E., 1982: Transportand dispersion of airborne pollutants associated with theland breeze - sea breeze system. Atmos. Env. 9, 2043-2053.

Authors' addresses: Ms. Dian Gaffen, National Oceanic andAtmospheric Admini~tration, R/PDC, 6010 Executive Blud.,Rockville, MD 20857, U.S.A., and Prof. Robert D. Bornstein,Department of Meteorology, School of Science, San JoseState University, San Jose, California, U.S.A.

t.

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