Spatial/Temporal Features Of Winter Snow Depth Anomaly Over Eurasian Continent And Its Impacting Factors

Using the former Soviet Union daily snow depth data during 1948-1994 provided by the National Snow and Ice Data Center, the NCEP/NCAR reanalysis data and month by month the NOAA Extended Reconstructed SST V3b, an index used to reflect the winter fresh snow depth was defined, as the winter fresh snow depth can more directly reflect the situation in winter snowfall. In the view of this point, the possible linkages among the winter snow depth over Eurasian Continent, the atmospheric circulation, and sea surface temperature are studied. Then based on the diagnostic results, we simulated the impact of the anomaly of the SST of the global ocean using NCAR CAM3 atmospheric general circulation model. The main conclusions are as follows:The leading EOF modes of both the winter fresh snow depth and winter snow depth show a coherent negative anomaly in the Eurasia Continent north to 50°N and positive anomaly in the south part. The correlation coefficient of the two EOF mode time series is 0.75. The second modes of EOF reflect east-west dipole pattern over the whole Eurasian Continent. Further analysis suggests that there is no correlation between late autumn snow depth anomaly and winter snow depth anomaly in aspects of both their spatial pattern and temporal evolution. The variability of winter snow depth over Eurasian Continent is mainly decided by the variability of winter fresh snow depth but not that of the snow depth in late autumn.The result of Height filed and snow depth using SVD technique shows that:the circulation through the two factors of temperature and precipitation will affect the abnormal distribution of the winter fresh snow depth, thereby affecting the distribution of winter snow depth. When showing the zonal circulation in the development of the Eurasian continent, the European slot and blocking are reduced, most of northern Eurasia controlled by the ridge of high pressure circulation, the system presents the warm ridge and cold trough, while rainfall over the ground is not conducive to the formation of snow in winter, so winter snow depth show a coherent negative anomaly in the Eurasia Continent north, whereas the snow depth increases; when showing a similar type of circulation EUP, the corresponding temperature, precipitation averaging a similar distribution, winter snow depth field show the inverse distribution spatial distribution between Eurasian central and eastern, western over Eurasian continent.The result of sea surface temperature and snow depth using SVD technique shows that the distribution of SST and snow depth is significant association. The statistical analysis of 500hPa height field and the winter sea surface temperature show that the abnormal distribution of sea surface temperature in the North Atlantic, the Pacific will affect the distribution of circulation over Eurasian continent, while the southern Atlantic, Indian Ocean may also affect the Northern Hemisphere circulation. In particular the distribution of the North Atlantic circulation and the Pacific are closely related field.Numerical experiments verify that Sea surface temperature will impact the distribution of winter snow depth, mainly through the circulation to link sea surface temperature and snow depth. The result is that Northern Hemisphere circulation is also sensitive to the southern hemisphere sea surface temperature, the North Atlantic, the Pacific, and the southern Atlantic sea surface temperature will affect abnormal distribution of the Eurasian Continent height field, and show the PNA teleconnection signal, when the North Atlantic sea surface temperature field in three-core type distribution, the inverse distribution spatial distribution between North America, the Pacific coast of the eastern equatorial Pacific and North Pacific sea surface temperature, the height field shows EUP teleconnection signal.