Temporal And Spatial Characteristics Of Atmospheric Water Cycle In Northeast China And Its Impact On Precipitation

Since the mid of 1980’s, most parts of China, especially the eastern region experienced a climate change which featured a warming of air temperature. Under this circumstance, we studied the spatial and temporal characteristics of precipitable water, precipitation, evaporation and water vapor flux divergence in different seasons over northeast China, analyzed the similarity of the spatial distribution of different moisture cycle factors and the moisture balance of that area, and compared the correlativity between northeast summer(July and August) precipitation and meridional moisture flux of different layers over east China in different time periods. The methods used in this paper mainly include similarity coefficient, trend coefficient, correlation coefficient, wavelet transform, composite and so on. The main conclusions are as follows:(1) The spatial and temporal characteristics of different moisture cycle factors in northeast China:the spatial distribution of precipitable water, precipitation and evaporation is characterized by that the value of elements above in southeastern area is larger than those in northwestern area; in summer, much precipitation and evaporation occurs in Changbai Mountain region as a strong moisture convergence region; in spring and autumn, moisture divergence dominates the northeast China; in winter, the moisture divergence and convergence are weak in this area. From 1979 to 2010, the total precipitation of summer and autumn in northeast China decreased significantly; especially from 1999 to 2010, the summer precipitation always demonstrated negative anomaly. Additionally, other elements in different seasons change in a truly imperceptible way.(2) The relationship among all the different moisture cycle elements:in terms of the similarity, the spatial distribution of precipitable water is most similar to that of precipitation in different seasons. That is to say, on seasonal scale, where there is more precipitable water, there is more precipitation. The spatial distribution of evaporation is similar to that of precipitation in spring and summer. The spatial similarity between zonal moisture flux and precipitation doesn’t vary from season to season, while the spatial similarity between meridional moisture flux and precipitation varies from season to season. In summer, the spatial distribution of meridional moisture flux is similar to that of precipitation. In winter, the spatial distribution of meridional moisture flux is opposite to that of precipitation. In spring and autumn, there is no similarity between them. Also, there is no similarity between water vapor flux divergence and other elements. In terms of the relationship between precipitation and evaporation, In spring, Evaporation is larger than precipitation all over the northeast China. While in summer, it is the opposite:precipitation is larger than evaporation. However, it is not the only season showing this distribution. In autumn and in winter, precipitation is larger than evaporation in the north of northeast China. The closer to coast the area is, the larger the difference between evaporation and precipitation is. In terms of the moisture balance of northeast China, the Interim ECMWF Re-Analysis (ERA-Interim) data has properly described the water balance of different seasons in northeast China. Based on ERA-Interim data, the moisture sinks computed through moisture convergence and moisture local variation are quite consistent with those computed through precipitation and evaporation, which proves that ERA-Interim data can be used in the research of water balance in northeast China. On seasonal scales, the moisture convergence has a greater impact than the local moisture variation on moisture sink, and the latter is variable slightly, generally as a constant. Likewise, in different seasons, the total precipitation has a much greater impact than the evaporation on moisture sink.(3) The influence of the moisture cycle on precipitation(in July and August) in northeast China:the integral whole layer of water vapor flux which has an influence on northeast summer(July and August) precipitation comes from south China sea and east China sea. The water vapor flux that comes from south China sea is obvious no matter they’re integrated in whole layer or in low-level(1000-850hPa) layer. However the water vapor flux that comes from east China sea is only obvious when they’re integrated in whole layer. Although the northeast summer(July and August) precipitation is positively correlated with the meridional moisture flux in different layers over east China from 1960-1984, during 1985-2013, the relationship between them is significant positive correlation only from 1000 to 850hPa, and there is no notable correlation from 850 to 300hPa.