Analysis on seasonal retreat of Siberian High(with attention to characteristics of the Siberian High between late winter and midwinter)

Abstract:

In midwinter the Siberian high predominates with its center around 45~55N/80~120E to bring the intense cold air outbreak in East Asia. However, seasonal retreat processes of the Siberian High from winter to spring, including the day-to-day variations, have not been systematically understood yet other than that it is weakened rapidly in April. According to our previous reports (EGU2015-3172, etc.) pointed out by a case study for 1984 (cold winter around Japan Islands), although the strong Siberian High still appeared frequently in early spring (e.g., 16Feb.~15Mar.) its 3-dimensional structure was rather different from that in midwinter (e.g., 1Jan.~15Feb.). The latitude of the strong surface high center which appeared in the eastern area (100~120E) in the early spring, with wider meridional range (45~65N), corresponded to the southern edge of the extremely low temperature area (Siberian air mass), differently from that in midwinter. In the present study, we will further perform the analyses on the above phenomena, with attention also to the persistency of the high, behavior of surface lows, and soon, by using mainly the daily weather maps provided by Japan Meteorological Agency and the NCEP/NCAR reanalysis data for 1975~1984. The maximum value of the surface high does not decrease so much in early spring in the Siberian area, but the appearance frequency of such highs decreased then. Thus, the seasonal decrease in the areal mean SLP there seems to be reflected by the slight weakening of the Siberian High itself with lower persistency, not by the increase in the cyclone activity around Siberia in early spring (the cyclone activity there did not increase so much until April). It is also noted that daily Siberian High with its extremely high pressure (e.g., more than 1040hPa) showed much less persistency in early spring than in midwinter. In this study, we will present of the overall features of the seasonal retreat processes of the Siberian High, also with combination of our previous results.