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Main modes of spring snow depth in Eurasia and their relationship with the North Atlantic SST

1.Nanjing University of Information Science &2.amp;3.Technology

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    Based on the daily snow depth (SD) data provided by the Japanese 55-year Reanalysis (JRA) project, the global reanalysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF) and the sea temperature data from Hadley Center(Hadley), this paper analyzes asymmetric modes of the spring SD anomaly in Eurasia and its teleconnection with the North Atlantic sea surface temperature(SST), the results are verified by numerical simulation analysis. The results show that there are significant differences between the first two modes of the spring SD over the Eurasian continent, which are represented as two asymmetric forms in this paper: the first mode features a zonal uniform distribution, and the second displays an obvious west–east contrast distribution. The North Atlantic "tri-polar" and the "saddle" SST modes have significant correlation with the first and the second mode of the SD, respectively. Corresponding to the two SST modes, the wave activity fluxes in the mid-high latitudes over the northern hemisphere are characterized by two kinds of propagation characteristics: Silk Road pattern (SRP) and Eurasian teleconnection pattern (EU), which have different effects on the position and intensity of the westerly air flow in the mid-high latitudes, and thus exert different remote influences on the SD distribution in Eurasia. The Localized Multiscale Energy and Vorticity Analysis (MSE-VA) shows that the kinetic energy (KE) of source region in the North Atlantic has a transform process from bottom to top. In addition, the average KE conversions enhance over the exit region of the Westerly Jet, benefiting the high-level KE accumulation and divergence outward and creating a remote effect on downstream areas. The CAM5.1 model simulation is used to study the effects of the two SST modes on the propagation characteristics of the wave activities flux. The simulation results verified the observation results well. The SST modes may responsible for SRP and EU propagation characteristics of the wave activities flux, meanwhile, the changes of the climatic field elements of the two SST modes are consistent with the distribution characteristics of the corresponding snow depth modes.

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  • Received:April 04,2019
  • Revised:November 03,2019
  • Adopted:November 15,2019
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