ANALYSIS OF THERMAL FEATURES OF LAKE-MICHIGAN FROM AVHRR SATELLITE IMAGES

The seasonal dynamics of thermal features in Lake Michigan were studied using numerous sea surface temperature images acquired from the NOAA Advanced Very High Resolution Radiometer from May-December, 1990. In southern Lake Michigan, the vernal thermal front moved offshore and to the north between 7 May 1990 and 11 June 1990. Inshore of the front, surface temperatures were > 10.0-degrees-C while offshore surface temperatures remained < 4.5-degrees-C. In northern Lake Michigan, thermal fronts were not prevalent until late June. Southern Green Bay consistently contained the warmest water in Lake Michigan and exceeded 15.0-degrees-C in May. Warm bay-water frequently mixed with cooler lake-water through the channels at the north end of the bay. Warm water plumes remained intact for several days with S/SW winds but were quickly obliterated by a N/NE wind. Upwelling was most conspicuous along the eastern shore of the lake. Depending on wind direction, upwelled water formed broad continuous nearshore bands or isolated patches of relatively cold water. Evidence of upwelling 1-3 days after the instigating wind event suggested oscillations of internal waves. Our study shows that the frequent acquisition of satellite images is useful to describe significant thermal features in a large lake.