Thermal Characterisation of Lake Morskie Oko Water in 2007 Based on Measurements by a Gradient Thermal Probe

The study was undertaken to illustrate a wide range of application of a gradient thermal probe in thermal characterisation of water reservoirs on the example of Lake Morskie Oko whose water temperature has been measured since 2006. For analysis, the data collected in 2007 were chosen because of the least missing data; in this year only the data from 13 days were not recorded. The data permitted analysis of changes in daily mean temperatures of water at particular depths, with the daily means calculated as arithmetic means from 144 measurements made at every 10 m. The daily amplitudes of temperatures at particular depths and mean daily amplitudes for particular months were determined, which permitted an assessment of the scale of the temperature amplitude damping with increasing depth. High frequency of temperature reading permitted detection of short-duration anomalies, taking place e.g., over a time span of 10 m, or their vertical extent. It has been established that measurement at 2 a.m. is the optimum for determination of the annual mean temperature. The time moments at which the minimum and maximum temperatures are recorded within a day at the surface were identified. Different variants of temporary jump changes in the surface water temperature within the day were analysed. The dynamics of temperature changes from the surface to the bottom of the lake was discussed.