Variation of main rainy‐season precipitation in eastern China and relevance to regional warming

Abstract China has experienced dramatic warming in summer mean temperature since the early 1990s, leading to precipitation variation across the region. We have studied the variation of rainy‐season (April–September) precipitation in eastern China during 1961–2016. Overall, we found that rainy‐season precipitation increased in the south and decreased in the north during 1992–2016 (PII) compared to 1961–1991 (PI). By defining rainfall‐belt indices of intensity and central location, we found that the southern rainfall‐belt during the main rainy‐season tends to produce much more‐intense precipitation during PI relative to PII, in contrast to the northern rainfall‐belt, which tends to have less‐intense precipitation during PII. Despite some fluctuations, the central positions of neither the northern nor the southern rainfall‐belts exhibit a statistically significant difference between the two periods. Unlike during PI, during PII, there is an obvious anticyclone over the Lake Baikal region. This anticyclone has caused anomalous north winds flowing from north‐central to southwestern China, leading to weakening of the northward moisture transport. Also, regions such as northeastern, north‐central, and southwestern China have been controlled by negative geopotential height anomalies and weak vertical air‐motion anomalies, resulting in drying from north to southwestern China. At the same time, the enhanced water‐vapour convergence in the southeastern coastal region of China favours increased precipitation there. These processes working in concert created the drying‐north–wetting‐south pattern in the main rainy‐season during 1961–2016. The change in rainfall‐belt intensity in eastern China has also shown a close relationship with the change in vapour transport from low latitudes. The weakened land‐sea thermal difference in the East Asia–Northwest Pacific region, which has weakened water‐vapour and atmospheric circulation, has also played a role in the change of rainfall‐belt intensity.