Effects of snow cover on urban surface energy exchange: Observations in Harbin, China during the winter season

Abstract

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).