Seasonal evolution of the dominant modes of the Eurasian snowpack and atmospheric circulation from autumn to the subsequent spring and the associated surface heat budget

本文研究了欧亚大陆地区雪水当量、积雪覆盖率以及500 hPa位势高度的主模态从秋季到次年春季的演变情况。结果表明,欧亚大陆地区的积雪与大气环流主模态从秋季至次年春季呈稳定而显著的相关关系。欧亚地区雪水当量和大气环流主模态的季节演变表现出了良好的连贯性,而积雪覆盖率的主模态则在秋-冬过渡时期表现出了较差的连贯性。在相应的表面热量收支方面,由近表面风驱动的热平流是影响表面热量收支的重要因素,在冬季尤为显著。此外,由积雪引起的短波辐射异常在春季扮演了同样重要甚至更加重要的角色。

This study investigates the seasonal evolution of the dominant modes of the Eurasian snowpack and atmospheric circulation from autumn to the subsequent spring using snow water equivalent （SWE）, snow cover frequency （SCF）, and 500 hPa geopotential height data. It is found that the Eurasian SWE/SCF and circulation dominant modes are stably coupled from autumn to the subsequent spring.The temporal coherence of the seasonal evolution of the dominant modes is examined.The seasonal evolution of the Eurasian circulation and SWE dominant modes exhibit good coherence, whereas the evolution of the Eurasian SCF dominant mode is incoherent during the autumn-winter transition season. This incoherence is associated with a sign-change in the SCF anomalies in Europe during the autumn-winter transition season, which is related to the wind anomalies over Europe. In addition, the surface heat budget associated with the Eurasian SWE/SCF and circulation dominant modes is analyzed. The sensible heat flux （SHF） related to the wind-induced thermal advection dominates the surface heat budget from autumn to the subsequent spring, with the largest effect during winter. The surface net shortwave radiation is mainly modulated by snow cover rather than cloud cover, which is estimated to be as important as, or likely superior to, the SHF for the surface heat budget during spring.The NCEP-NCAR surface heat flux reanalysis data demonstrate a consistency with the SWE/SCF and air temperature observational data, indicating a good capability for snow-atmosphere interaction analysis.