Daytime heat balance for estimating non-radiative fluxes of Lake Banyoles, Spain

Abstract

Combining a six-term heat balance equation and a seasonal thermocline model, a new equation to calculate non-radiative fluxes of Lake Banyoles has been determined. Mean daily measurements of global solar radiation, downward longwave radiation, wind speed, air temperature and water surface temperature were used as input data and lake temperature as the calculated output data of the model. To calibrate performance of the new equation, calculated lake temperature was compared with measured lake temperature during both the mixing and the stratified period of the lake. The new coefficients in the wind function to calculate the non-radiative fluxes at the water surface were assumed to depend on the variability of the wind speed, the air temperature of the study area and the surface temperature of the lake. In addition, the results were used to estimate the heat balance of the air-water interface of Lake Banyoles over a period of two years. The processes that have been taken into account are shortwave and longwave radiation, back-radiation emitted by the lake, sensible and latent heat and throughflow.