关键词: 降水相态, 时空分布, 大气环流指数

Abstract:

Based on the daily surface observation data, circulation features indices reorganized by National Climate Center and the reanalysis data of the US National Center for Atmospheric Research of National Centers for Environmental Prediction (NCEP/NCAR), detailed investigation is conducted of the temporal and spatial variations of different precipitation phases (rain, snow, sleet, freezing rain, ice particle) in Eastern China during winter in 1981-2011. The results show that: in Eastern China, the region to the north of 29°N and to the west of 120°E is called main snow region, where the majority of the precipitation phases is snow. On the other hand, the region to the south of 29°N and to the East of 120°E is called main rain region, where the majority of the precipitation phase is rain. Besides, along the 29°N and 120°E, the sleet occurs frequently, and the freezing rain and ice particle are mostly concentrated in the stations which are in the mountains. The different precipitation phases in Eastern China during winter have obvious and different interannual fluctuations. Compared to that in the 21st century, the statistical data of all kinds of precipitation phases are relatively small in the late 1980s to 1990s. Except rain, the fluctuation frequency of snow, sleet, freezing rain, and ice particle tend gradually to the same since 2000. We define a new statistic' station-days' to describe the influence of the precipitation, which combines the temporal and spatial variation characteristics. In Eastern China during the past 30 winters, the station-days of rain and sleet have increased evidently with the positive trend coefficient 0.526 and 0.402 respectively. The station-days of the precipitation phases also have close relationships with the general atmospheric circulation, especially with East Asian Winter Monsoon and polar vortex over Asian. The results of correlation analysis show that the station-days of rain during winter has an obvious negative correlation with the strength of East Asian Winter Monsoon, that is to say, when the East Asian Winter Monsoon is stronger, there is less rain in Eastern China, but the station-days of the other four phases of precipitation have the opposite situation. At the same time, the station-days of snow, sleet, freezing rain, and ice particle are positively correlated with the Asian polar vortex area index, in other words, when the area of polar vortex over Asian is bigger, there are more solid phases of precipitation, especially more snow and ice particle in Eastern China than usual, which can pass the 99% confidence level of T test. The station-days of rain is positively correlated with the Asian polar vortex strength index too, it means that, when the polar vortex over Asian is stronger, there is more rain in Eastern China, which can pass the 95% confidence level of T test.

Key words: precipitation phase, spatial and temporal distribution, atmospheric circulation index