The regression coefficients for the wintertime precipitation and air temperature in China are shown in Figs. 3.4a,b. It can be seen from Fig. 3.4a that during a warm PDO phase the precipitation is less than normal in most of China, especially in northeastern, northern China and along Yangtze River valley. This can be attributed to the deepening and southward moving of Aleutian low and the strengthening of winter monsoon in East Asia. On the interdecadal timescale, there is a significant northwesterly anomaly along the coastal regions, which is not in favor of precipitation.

The temperature is significantly warmer than normal in the northeastern, northwestern and northern China while cooler than normal in the southwestern and southeastern China (Fig. 3.4b). A variety of studies have shown that over the past two decades the temperature anomalously rises in northern part of China, and the "warming winter" phenomenon occurred successively. However, this is not true for the southwestern and southeastern China where the surface is cooling. As shown in Fig. 3.3b, similar cooling can be seen at 850hPa. Thus, the "northern warming versus southern cooling" pattern is a typical feature for the interdecadal variations of winter temperature in China, which is closely associated with the PDO.

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