Variations in the underlying surface temperature and the problem of closure of the heat balance equation

The results of measurements of the components of the heat balance equation fur the land surface and of time variations in land surface temperature are given. It is shown that the daily regime of the exchange between the atmos phere and the underlying surface is essentially nonstationary. In this conn ection, the authors propose that, instead of the heat balance equation, the heat influx equation should be used in studying heat balance. The heat inf lux equation takes into account variations in the heat content of the lower atmospheric surface layer and a thin (3-5 cm) soil layer, which can range up to 30% of the value of the radiation balance during daylight hours. It i s also shown that, when the layer between the land surface and the level at which an instrument is mounted to measure the heat flux into the soil is t aken into account, the value of the recorded imbalance in the heat influx r educes by 4%. The employment of the BREB (Bowen Ratio Energy Balance) metho d, based on the use of the surface heat balance equation for stationary con ditions without taking into account variations in land surface temperature, may result in an error up to 40% in determining the values of turbulent he at and humidity fluxes.