资源环境科技发展态势分析平台

The surface energy balance over Harbin, one of the major cities in severe cold regions of China, is examined during the snow-covered and snow-melt periods (January 11 to April 20, 2017) using radiation and eddy covariance measurements. Comparisons of radiation and energy fluxes from fresh snow, cold snow, melting snow, and snow-free periods revealed that the presence of snow cover has a considerable impact on the radiation and energy balances. The daytime net radiation was mostly dissipated as sensible heat flux with a fraction of 43% during the fresh snow periods. During the cold snow periods, the daytime fraction of sensible heat flux decreased to 31% and most available energy was stored in the urban surfaces. During the melting snow periods, since the snowmelt process consumed a considerable portion of available energy, the daytime fraction of sensible heat flux decreased about 20% when compared to the cold snow periods, while the daytime fraction of latent heat flux increased about 50% due to the evaporation of melt water. After the snow melted, the ratio of daytime latent heat flux decreased because vegetation was not yet active during the snow-free periods and the Bowen ratio increased from 2.3 (melting snow periods) to 5.9 (snow-free periods).