Atmospheric Circulation Characteristics of Anomalous Precipitation in Northern China in April and Its Relationship to Sea Surface Temperature Anomalies

Using monthly precipitation data from 81 observational stations in Northern China for 1960-2007 and American NCEP/ NCAR reanalysis data, this paper studies temporal and spatial characteristics of precipitation in North of China in April and its relationship to anomalous atmospheric circulation and sea surface temperature anomalies (SSTA) in key oceanic areas. The results show that in rich rainfall years there was negative phase of EU teleconnection pattern in the upper level of troposphere on high latitude in Northern Hemisphere, and East Asia was controlled by and located at southwest of anomalous anticyclone. Accordingly, strong southerly prevailed over Eastern China, and there was strong water vapor transportation from south to north, which brought rich water vapor into North of China. At the same time, at middle and high latitudes were large-scale anomalous zonal circulation and front zone in Northern Hemisphere, and Northern China was controlled by anomalous warm ridge and large-scale front. Meeting of cold and warm air masses, and role of the large-scale front led to rich rainfall in North of China. In less rainfall years at middle and high latitudes were anomalous large-scale meridional circulation and front zone in Northern Hemisphere, and Northern China was affected by cold air flow at southwest of anomalous cyclone and was drought. In rich rainfall years precipitation in Northern China in April had close connections to previous and synchronous SSTA in key oceanic areas, as well as to SSTA evolution from winter to next spring; in less rainfall years, it was not so clear. Therefore, the relationships between rich rainfall and SSTA or its evolution, as well as between less rainfall and SSTA or its evolution, were obviously asymmetric.