| 摘要 |
Based on the reanalysis data of the National Center for Environmental Prediction (NCEP) and the precipitation dataset of the U.S. Climate Prediction Center (CPC), the changing trend of summer precipitation in North China (35°- 40° N, 110°-125° E) during 1979-2020 was studied. By calculating the monthly climatic precipitation in North China, it is found that precipitation was mainly distributed from June to August, the trend of precipitation in North China from June to August was mainly analyzed. Firstly, the five-point moving average of regional mean precipitation in North China from June to August during 1979-2020 was conducted. It is found that the fitting curve of the five-point sliding average was basically consistent with the changing trend of regional precipitation, and it showed a certain upward trend. Secondly, the cumulative anomaly of regional average summer precipitation in North China showed a significant upward trend after 2005, which was similar to the moving average result, indicating that the precipitation in the later period increased compared with the earlier period. The changing trend of summer precipitation in North China in the past 42 years was analyzed, and the results show that precipitation showed a significant increasing trend in most areas of North China, so that regional average precipitation also tended to increase significantly. By comparing the precipitation in the past five years (2016-2020) and the last 36 years (1979-2015), it is found that the increase of summer precipitation in North China was more obvious, so the reasons for the increase in precipitation were further analyzed. Since the occurrence of precipitation requires favorable thermal dynamic conditions, the one-dimensional linear regression of water vapor content at 850 hPa and meridional wind speed was conduced, and it is found that the two variables tended to increase obviously, which was consistent with the increasing trend of precipitation. Seen from both the results of regional average and the spatial distribution of trends, the lower atmospheric water vapor content and wind speed showed a significant positive trend, which led to the increase of summer precipitation. Therefore, it can be concluded that there was a certain changing trend of summer precipitation in North China in the past 42 years, which can provide certain reference for the future forecast of summer precipitation in North China. |
