Lake-breezes Impact on High-resolution Numerical Weather Predictions for a Coastal Urban Area

An integrated experimental sub-kilometer atmospheric modeling system with grid-spacings of 1 km and 250 m using hourly forcing of lake-surface temperatures and including urban processes has been developed at the Meteorological Service of Canada (MSC) in order to provide more accurate weather forecasts at the city scale. A real-time forecasting system has been designed over the Greater Toronto Area (GTA) lying on the coast of Lake Ontario, and has provided forecasts for the last year and in particular during the Panam 2015 sport event. Surface physical processes are represented with the Town Energy Balance (TEB) model for the built-up covers and with the Interactions between the Surface, Biosphere, and Atmosphere (ISBA) land surface model for the natural covers. Surface temperatures for the Great Lakes are prescribed using 2-km hourly output from an ocean model. In this study the ability of the system to capture the lake-breeze patterns for several conditions will be presented. The influence of lake-breeze on several forecasted variables will be discussed, as for example, on thermal stress indices deveolped in the system. Observations from a dense surface network will support the discussions.