Main features of the thermal regime of Lake Ladoga during the ice-free period

The thermal regime of Lake Ladoga during the ice-free period is determined by primarily incoming solar radiation, wind-induced mixing and the depth distribution. The variation of water surface temperature with time for different areas of the lake is discussed using temperature measurements obtained by means of an aircraft-mounted IR-radiometer. Maximum values of water surface temperature in these areas, as well as the time lags between the areas are determined. Mean rates of temperature variation for the periods of warming and cooling of the lake are also determined. A formula for determining the location of the spring frontal zone at different stages of water warming is suggested. The peculiarities of the interaction of stratified and isothermal waters in the frontal zone, the slope of the frontal zone and the thermal balance components are discussed on the basis of specialized field measurements by using ships and aeroplane. The scales of temperature inhomogeneities are obtained based on computation of 2D spatial correlation functions.