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Lake Breezes in SW Ontario and Their Influence During BAQS-Met 2007. David Sills 1 , Jeff Brook 2 and Peter Taylor 3 1 Cloud Physics and Severe Weather Research Section, Environment Canada, Toronto, Canada 2 Air Quality Research Division, Environment Canada, Toronto, Canada
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Lake Breezes in SW Ontario and Their Influence During BAQS-Met 2007 David Sills1, Jeff Brook2 and Peter Taylor3 1Cloud Physics and Severe Weather Research Section, Environment Canada, Toronto, Canada 2Air Quality Research Division, Environment Canada, Toronto, Canada 3Department of Earth and Space Science and Engineering, York University, Toronto, Canada 2008 AGU Fall Meeting 15-19 December, San Francisco, CA
Updrafts Weak Subsidence Weak Subsidence Lake breezes Assume midday heating over land between two lakes 2000 Return Flow Return Flow Height (m) 1000 Lake Breeze Inflow Lake Breeze Inflow 0 0 40 Distance (km)
F r e e A t m o s p h e r e CAPPING INVERSION ENTRAINMENT ZONE CAPPING INVERSION Residual Layer Residual Layer Convective Mixed Layer CAPPING INVERSION TIBL TIBL CAPPING INVERSION SURFACE LAYER Lake breezes Eight different air regimes crossing from lake to lake 2000 Height (m) 1000 Lake Breeze Front Lake Breeze Front Lake Breeze Inflow Lake Breeze Inflow 0 0 40 Distance (km)
F r e e A t m o s p h e r e CAPPING INVERSION ENTRAINMENT ZONE CAPPING INVERSION Residual Layer Residual Layer Convective Mixed Layer CAPPING INVERSION TIBL TIBL CAPPING INVERSION SURFACE LAYER Lake breezes 2000 LCL Height (m) 1000 LCL LCL Lake Breeze Inflow Lake Breeze Inflow 0 0 40 Distance (km)
‘High deformation’ lake breeze circulations Moderate synoptic wind regime (SW) Classic vs. High Deformation ‘Classic’ lake breeze circulations Weak synoptic wind regime
Why are lake breezes important? • Affect the climate of the region around the lake • Affect air quality: • 3-D transport of pollutants / precursors in lake breeze circulations • Increased insolation for photochemistry • Decreased mixing heights reduce pollutant dispersion • Affect summer severe weather: • Lake air suppresses thunderstorms • The lake breeze front provides a lifting mechanism for the initiation of thunderstorms • In SW Ontario, surrounded by large and small lakes
Past Lake Breeze Research • Lots of work done on sea breezes and their effects on air quality in coastal regions: Canada, US, UK, Greece, Japan • A number of studies of Great Lakes lake breezes have been conducted: Biggs and Graves 1962, Moroz 1967, Lyons 1972, Estoque et al. 1976, Comer and McKendry 1993, Sills et al. 2002 • Lake breezes and air quality in the Great Lakes region studied by: Lyons and Olsson 1973 (Lake Michigan), Mukammal et al. 1982 (Lake Erie), Sills 1998 (SW Ontario), Hastie et al. 1999 (Lake Ontario)
Outstanding Questions • Are most ozone exceedances that occur in the absence of long-range transport associated with lake breeze circulations and their effects? • Why do pollutant concentrations often peak with the passage of the lake breeze front then fall off? • How important are vertical motions (upward and downward) associated with lake breeze circulations in transporting pollutants/precursors? • How well do current NWP models handle: • changes in boundary-layer depth due to lake breeze circulations? • the intensity of upward and downward vertical motions? • the initiation of thunderstorms at lake breeze fronts?
Lake Huron Lake Huron Lake Huron 0 30 km BAQS-Met 2007 A multi-agency field program combining both high resolution AQ and met measurements N Sarnia Sarnia London London London Detroit Detroit Detroit Bear Creek Lake St. Clair Lake St. Clair Ridgetown Lake Erie Lake Erie Windsor Windsor Windsor Harrow Lake Erie Lake Erie Toledo Toledo Toledo
Lake Huron Lake Huron Lake Huron 0 30 km BAQS-Met 2007 Mesonet N • Mobile: • Twin Otter aircraft • CRUISER AQ lab • AMMOS met vehicle YXU Sarnia Sarnia London London London FTGM4 YZR FNT PHN ALV 16015 LAR SOM MTC PTK AMM CRO VLL LSC LSCM4 Detroit Detroit Detroit BEA 13001 45132 PAL DET 45147 XRG Lake Erie Lake Erie PAI Windsor Windsor Windsor YQG LIG WAJ 12016 DTW MER WOO LEGEND YIP 12059 ARB STA PAQ COT WHE Existing operational met stn Existing OME AQ + met stn EC AQ supersite + met stn Univ AQ supersite + met stn + profiles EC ATMOS met stn + AQ YorkU ATMOS met stn EC buoy met EC buoy AQ + met EC AMMOS mobile met KONZ LEA XHA IADN XPT TTF 85135 WNB THLO1 Toledo Toledo Toledo DUH THR01 45005
Lake Breeze Detection Each of these can also be ambiguous at times...
Wind Direction Ozone PM2.5 Wind Speed Temperature Dew Point Lake Breeze Detection 1 min data Merlin Station
Lake Breeze Stats (Preliminary) For entire June – August 2007 period: • 30% were Classic, 70% were HD lake breezes • 100% of high ozone* days had active lake breezes • 86% of days with thunderstorms had active lake breezes • 100% of severe thunderstorm days had active lake breezes * 1-hr avg O3 >= 80 ppb at more than one station
Lake Breeze Stats (Preliminary) During the 20-day intensive period: • Lake breezes somewhere within study region every day of intensive! • 3 Classic lake breeze days (Jun 23rd, 25th, Jul 2nd), the rest HD • 9 high ozone days, 3 thunderstorm days, 2 severe thunderstorm days – all with lake breezes • Wide variety of synoptic regimes – wind speed light to moderate, direction S through NNE
25 Jun 07 Cross-section Convective Mixed Layer Depth ~ 1500 m Lake St. Clair lake breeze depth ~ 300 m 2000 F r e e A t m o s p h e r e CAPPING INVERSION ENTRAINMENT ZONE CAPPING INVERSION Residual Layer Residual Layer Height (m) 1000 Convective Mixed Layer CAPPING INVERSION CAPPING INVERSION TIBL TIBL Lake Breeze Inflow Lake Breeze Inflow SURFACE LAYER 0 Southwestern Ontario Lake Erie Lake St. Clair 0 40 Distance (km)
25 Jun 07 Cross-section Updraft at front ~ 2 m s-1 Downdraft behind front ~ 3 m s-1 2000 F r e e A t m o s p h e r e CAPPING INVERSION ENTRAINMENT ZONE CAPPING INVERSION Residual Layer Residual Layer Height (m) 1000 Convective Mixed Layer CAPPING INVERSION CAPPING INVERSION TIBL TIBL Lake Breeze Inflow Lake Breeze Inflow SURFACE LAYER 0 Southwestern Ontario Lake Erie Lake St. Clair 0 40 Distance (km)
Summary and Future Work • Lake breezes very frequently affected SW Ontario in the summer months of 2007 • The circulations can strongly influence air quality over all of SW Ontario due to 3-D motions, reduced mixing heights, and increased insolation • They also frequently help to initiate thunderstorms, including severe weather • Mesonet, aircraft and other BAQS-Met data will be used to further address the ‘outstanding questions’ related to lake breezes
Acknowledgements • Norbert Driedger, Emma Bradbury and Lesley Hill for their hard work on the mesoanalysis database and products • Kathy Hayden for discussions (her talk is next!)
References Biggs, W. G. and M. E. Graves, 1962: A Lake Breeze Index. J. Appl. Meteorol., 1, 474- 480. Comer, N. T. and I. G. McKendry, 1993: Observations and Numerical Modelling of Lake Ontario Breezes. Atmos-Ocean, 31, 481-499. Estoque, M. A.; J. Gross and H. W. Lai, 1976: A Lake Breeze over Southern Lake Ontario. Mon. Wea. Rev., 104, 386-396. Hastie, D. R., J. Narayan, C. Schiller, H. Niki, P. B. Shepson, D. M. L. Sills, P. A. Taylor, Wm. J. Moroz, J. W. Drummond, N. Reid, R. Taylor, P. B. Roussel and O. T. Melo, 1999: Observational evidence for the impact of lake breeze circulation on ozone concentrations in southern Ontario. Atmospheric Environment, 33, 323-335. Lyons, W. A., 1972: The Climatology and Prediction of the Chicago Lake-breeze. J. Appl. Meteorol., 11, 1259-1270. Lyons, W. A. and L. E. Olsson, 1973: Detailed Mesometeorological Studies of Air Pollution Dispersion in the Chicago Lake Breeze. Mon. Wea. Rev., 101, 387-403. Moroz, W. J., 1967: A Lake Breeze on the Eastern Shore of Lake Michigan: Observation and Model. J. Atmos. Sci., 24, 337-355. Mukammal, E. I., H. H. Neumann, and T. J. Gillespie, 1982: Meteorological conditions associated with ozone in southwestern Ontario, Canada. Atmospheric Environment, 16, 2095–2106. Sills, D. M. L., 1998: Lake and land breezes in southwestern Ontario: observations, analyses and numerical modelling. PhD dissertation, CRESS, York University, 338 pp. Sills, D., P. Taylor, P. King, W. Hocking and I. Nichols, 2002: ELBOW 2001 - studying the relationship between lake breezes and severe weather: project overview and preliminary results. Preprints, 21st Severe Local Storms Conference, San Antonio, TX, Amer. Meteorol. Soc., 611-614.