We use observed daily precipitation data from years 2004-2017 to investigate and compare the characteristics of precipitation at the Vostok and Casey stations in inland and coastal Antarctica, respectively. The precipitation has a positive trend at Vostok (3.3 mm yr-1, significant) and a negative trend at Casey (-4.4 mm yr-1, insignificant). The annual number of precipitation days has a significant positive trend at Vostok (14.4 days yr-1) and Casey (3.3 days yr-1). The air-mass backward trajectories from the stations are simulated applying the HYSPLIT model. The moisture needed for high-precipitation events originates from the ocean but in many (some) cases the trajectories cover long distances over the ice sheet before reaching Vostok (Casey). We apply three methods including composite analysis, Empirical Orthogonal Functions (EOF), and Self-Organizing Maps (SOMs) to examine the synoptic patterns associated with extreme precipitation events. At Vostok in the inland high plateau, atmospheric reanalysis data (ERA-Interim) show that the synoptic patterns governing the extreme precipitation events are relatively complicated. Amplified planetary waves allow water vapor to reach the Vostok Station from different source regions, including the Weddell Sea, Ross Sea and the Indian Ocean off the Amery Ice Shelf. A dipole structure of negative (positive) height anomalies to the west (east) of the station is identified as the cause of southward water vapor transport and resulting precipitation at Casey in coastal Antarctica.
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