Temporal And Spatial Variability Of Snow Water Equivalent Major Modes In Northern Hemisphere On Seasonal And Interannual Timescales And The Climate Impact With Arctic Sea Ice

Based on the monthly mean satellite remote sensing snow waterequivalent (SWE) data during the period1979-2007from National Snowand Ice Data Center (NSIDC), the spatial and temporal variabilities of SWEover the Northern Hemisphere are studied. Seasonal evolution of SWEshows that the far east of Eurasia and parts of North America haveexperienced an earlier snowfall and later melting compared to the other parton the same latitude. The hemispheric SWE usually has two monthpersistence in spring and fall seasons, especially in November, while“spring barrier” occurs from late winter to spring. The leading mode ofSWE on seasonal timescale appears a consistent variability on the wholehemisphere with annual cycle and about93%variance contribution. On theinterannual timescale, there are two major modes of SWE which variancecontribution respectively reach13.1%and8.3%. The first mode mostlyreflect the variability of SWE over the Eurasia Midwest, while the secondmode mainly reflect the variability of SWE over most mid-high latitude ofthe North America. The Eurasia Midwest mode of SWE has a greatrelationship with sea ice, atmospheric circulation and storm activity. Thecorrelation analysis results show that the melting of previous year summerArctic sea ice will cause the negative anomalies of Arctic Oscillation (AO)which can weaken the pressure difference between middle and highlatitudes and conduct the polar cold air more easy down to the Eurasia. Theupper air over the Atlantic sector of the Arctic, extending to the UralMountains, is a high pressure anomaly which can obstruct and divert the200hPa jet to south. This steer current and high pressure anomaly will also increase storm activity on southwest of Eurasia. The synoptic system fromsoutheast of Atlantic will bring more moisture and energy which will beavailable for the formation of snow on west of Eurasia after landing.Otherwise, there enhance the storm activity from polar southward thecentral of Eurasia for the snow increasing there. The Arctic sea ice forcednumerical experiments can highlight the function of sea ice to theatmosphere on mid and high latitudes and snow, and the simulation resultscan better reflect the west Eurasia snow changes. Only with the melting ofArctic sea ice can forced the high pressure anomaly on high latitude andnegative temperature anomaly corresponding with the increasing of snowdepth on west Eurasia. While the temperature and pressure anomaly fieldare more northern and eastern, either is the positive position of upper air jet.Nevertheless, the storm activities over the west Eurasia are apparentlypositive anomaly which prove that the storm activities will affect the snowdirectly.