Comparisons between Canadian Limited Area Model (LAM) Simulations of the Lake Breeze and Lidar, Radar and Mesonet Measurements during the 2015 Pan American and Parapan American Games in Toronto

The Lake Ontario lake breeze plays an important role in modifying temperature, humidity and winds across coastal regions. Updrafts along the lake-breeze front can transport pollutants vertically and can also help to initiate thunderstorm development. Previous studies of the lake breeze in the Toronto area were limited to analyses of surface meteorological data with clear-air radar reflectivity, and aircraft observations of winds and pollutants. Doppler Lidars and Radars can remotely obtain continuous high-resolution winds and therefore can be used to observe lake breeze circulations more in detail.  In addition, a dense mesonet can provide enhanced details at the surface and in an urban environment.

In order to investigate the capability of Doppler Lidars in measuring lake breeze evolution over Lake Ontario and the Toronto area, an extensive field campaign was conducted during the 2015 Pan American and Parapan American Games. Two scanning Doppler Lidars were operated in constant elevation, constant azimuth, and vertically staring modes while the King City C-band Radar provided 5-min low-level scans. A special urban mesonet consisting of 55 surface sites was deployed to collect surface meteorological data and provide 1-min averages. The high-resolution version of the GEM (Global Environmental Multiscale) model in Limited Area Model mode was used to simulate the lake breeze flow with the horizontal spatial resolution of 0.25 km during the Games. This work will present comparisons of the observations and the simulations of lake breezes on several days. Preliminary results indicate that the high-resolution model is capable of reproducing the observed effects of strong lake breezes. The errors in modelled lake breeze timing, intensity and location will be discussed. The results can be used to improve the model forecast capabilities in the region.