Analysis of Vorticity and Divergence Fields and Other Meteorological Parameters over Lake Ontario during IFYGL

Abstract

Surface wind data obtained from the United States and Canadian International Field Year for the Great Lakes (IFYGL) buoy network are used to estimate the vorticity and divergence feeds over Like Ontario. Hourly values of these variables are computed for the period May?October 1972. Lakewide temperature,, relative humidity and wind speed for the same period of time are also analyzed for their spectral characteristics. Distinct land-lake breeze circulations are observed on calm days in summer, when the flow is divergent and anticyclonic during the day and convergent and cyclonic at night. The six-month averaged daily values show similar but weaker diurnal variations. The changes from land-to-lake and lake-to-land breeze occur at about 0800 and 1800 local time, respectively. The six-month average of the divergent field is zero and that of the vorticity field is cyclonic with a value of 3.5?10?6 s?1. Spectral characteristics are also investigated by analyzing the six-month time series. In addition to diurnal variations, the features of synoptic-scale motions are also obtained. Power spectral densities, coherence spectra, phase difference spectra and calculated time lags between selected variables are analyzed and presented.