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.

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, Canada2Air Quality Research Division, Environment Canada, Toronto, Canada

3Department of Earth and Space Science and Engineering, York University, Toronto, Canada

2008 AGU Fall Meeting15-19 December, San Francisco, CA

Lake breezes

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Assume midday heating over land between two lakes

Lake breezes

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ake Breeze F

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Eight different air regimes crossing from lake to lake

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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 St. Clair

Lake ErieLake Erie

Harrow

Ridgetown

Bear Creek

0 30 km

BAQS-Met 2007 Mesonet

IADN

PTK

VLL

DET

DTWYIPARB

MTC

PHNYZR

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

BEALSC

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 dataMerlin Station

Wind DirectionOzonePM2.5

Lake Breeze Detection

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:

June July August Total

Lake Huron 27 days 26 days 19 days 78%

Lake St. Clair 26 days 26 days 22 days 80%

Lake Erie 26 days 27 days 23 days 83%

* 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 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

During the 20-day intensive period:

Jun 20 – Jul 9

Lake Huron 19 days

Lake St. Clair 18 days

Lake Erie 19 days

25 Jun 2007

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25 Jun 07 Cross-section

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Convective Mixed Layer Depth ~ 1500 m Lake St. Clair lake breeze depth ~ 300 m

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25 Jun 07 Cross-section

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Lake Erie Lake St. ClairSouthwestern Ontario0

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Lake Breeze InflowLake 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!)

ReferencesBiggs, 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.