Presentation on theme: "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."— Presentation transcript:
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 3 Department of Earth and Space Science and Engineering, York University, Toronto, Canada 2008 AGU Fall Meeting 15-19 December, San Francisco, CA
Lake breezes 1000 2000 Height (m) 0 040 Distance (km) Lake Breeze Inflow Updrafts Weak Subsidence Weak Subsidence Return Flow Assume midday heating over land between two lakes
Lake breezes 1000 2000 Height (m) 0 040 Distance (km) Lake Breeze Inflow Convective Mixed Layer Residual Layer Residual Layer F r e e A t m o s p h e r e CAPPING INVERSION ENTRAINMENT ZONE SURFACE LAYER TIBL Lake Breeze Front Eight different air regimes crossing from lake to lake
Convective Mixed Layer Residual Layer Residual Layer F r e e A t m o s p h e r e CAPPING INVERSION ENTRAINMENT ZONE SURFACE LAYER TIBL Lake breezes 1000 2000 Height (m) 0 040 Distance (km) Lake Breeze Inflow LCL
Classic vs. High Deformation ‘Classic’ lake breeze circulations Weak synoptic wind regime ‘High deformation’ lake breeze circulations Moderate synoptic wind regime (SW)
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?
BAQS-Met 2007 A multi-agency field program combining both high resolution AQ and met measurements N Lake Huron Detroit Windsor London Toledo Sarnia Lake Erie Lake Huron Detroit Windsor London Toledo Sarnia Lake Erie Lake Huron Detroit Windsor London Toledo Lake St. Clair Lake Erie Harrow Ridgetown Bear Creek 0 30 km
BAQS-Met 2007 Mesonet IADN PTK VLL DET DTW YIP ARB MTC PHN YZR YQG XHA WNB WAJ YXU DUH THLO1 45005 FTGM4 THR01 TTF XRG XPT 45147 LSCM4 N FNT 12016 12059 13001 16015 KONZ 85135 SOM ALV LAR PAL CRO PAI MER LIG STA WOO COT PAQ LEA WHE BEA LSC Lake Huron Detroit Windsor London Toledo LEGEND 0 30 km 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 Sarnia Lake Erie Lake Huron Detroit Windsor London Toledo Sarnia Lake Erie Lake Huron Detroit Windsor London Toledo 45132 AMM Mobile: Twin Otter aircraft CRUISER AQ lab AMMOS met vehicle
Lake Breeze Detection Each of these can also be ambiguous at times...
Lake Breeze Detection Wind Speed Temperature Dew Point 1 min data Merlin Station Wind Direction Ozone PM2.5
Lake Breeze Stats (Preliminary) 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 For entire June – August 2007 period: JuneJulyAugustTotal Lake Huron27 days26 days19 days78% Lake St. Clair26 days 22 days80% Lake Erie26 days27 days23 days83% * 1-hr avg O3 >= 80 ppb at more than one station
Lake Breeze Stats (Preliminary) Lake breezes somewhere within study region every day of intensive! 3 Classic lake breeze days (Jun 23 rd, 25 th, Jul 2 nd ), 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 During the 20-day intensive period: Jun 20 – Jul 9 Lake Huron19 days Lake St. Clair18 days Lake Erie19 days
Convective Mixed Layer Residual Layer Residual Layer F r e e A t m o s p h e r e CAPPING INVERSION ENTRAINMENT ZONE SURFACE LAYER TIBL 25 Jun 07 Cross-section 1000 2000 Height (m) Lake ErieLake St. Clair Southwestern Ontario 0 040 Distance (km) Lake Breeze Inflow Convective Mixed Layer Depth ~ 1500 m Lake St. Clair lake breeze depth ~ 300 m
Convective Mixed Layer Residual Layer Residual Layer F r e e A t m o s p h e r e CAPPING INVERSION ENTRAINMENT ZONE SURFACE LAYER TIBL 25 Jun 07 Cross-section 1000 2000 Height (m) Lake ErieLake St. Clair Southwestern Ontario 0 040 Distance (km) Lake Breeze Inflow Updraft at front ~ 2 m s -1 Downdraft behind front ~ 3 m s -1
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.
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