Synoptic variability of energy parameters in an ice-covered lake at the end of winter

Abstract

Synoptic variability of the energy parameters in an ice-covered lake was studied during the period of spring radiatively-driven convection. Measurements of water temperature (a chain with 14 temperature sensors TR-1060 RBR), solar radiation fluxes (two star-shaped pyranometer Theodor Friderich & Co, Germany for recording the incident and reflected radiation and one pyranometer M80 for recording radiation penetrating the ice) in an ice-covered small boreal lake carried out from 28 March to 6 April 2020. During the measurement period, there was a sharp change in the weather - first there were five sunny days, then heavy snow fell for two days, the next three days there was partly cloudy weather, and on the last day of measurements there was sunny weather. The flux of under-ice radiation reacted sensitively to snowfall and decreased from 100 W/m2 (day maximum) to 5-10 W/m2 after snowfall. This flux increased to 50-60 W/m2 as the snow melted. Changes in background potential energy (BPE), and buoyancy flux were calculated using TR-chain and pyranometer M80 data. A well-pronounced increase in BPE and buoyancy flux against the sunny weather and a sharp slowdown in the growth of these parameters after snowfall were revealed.