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CN 11-1768/O4

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Main Modes of Spring Snow Depth in Eurasia and Their Relationship with the North Atlantic SST
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    Abstract:

    On the basis of the daily snow depth (SD) data provided by the Japanese 55-year Reanalysis project, the global reanalysis data from the European Centre for Medium-Range Weather Forecasts and sea temperature data from Hadley Center (Hadley), this study analyzes the asymmetric modes of the spring SD anomaly in Eurasia and its teleconnection with the North Atlantic sea surface temperature (SST). Results are verified by numerical simulation analysis. Significant differences are found between the first two spring SD modes over the Eurasian continent that are represented as two asymmetric forms in this study: the first mode features a zonal uniform distribution, and the second displays an obvious west–east contrast distribution. North Atlantic “tri-polar” and “saddle” SST modes have a significant correlation with the first and second SD modes, 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), both of which have different effects on the position and intensity of the westerly air flow in middle–high latitudes, and thus exert different remote influences on the SD distribution in Eurasia. The localized multiscale energy and vorticity analysis 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 high-level KE accumulation and outward divergence and creating remote effects on downstream areas. The CAM5.1 model simulation is used to study the effects of the two SST modes on the propagation characteristics of wave activity fluxes. Simulation results verify the observation results well. SST modes may be responsible for the SRP and EU propagation characteristics of wave activity fluxes. Meanwhile, changes in the climatic field elements of the two SST modes are consistent with the distribution characteristics of the corresponding SD modes.

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History
  • Received:April 10,2019
  • Revised:
  • Adopted:
  • Online: July 28,2020
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