青藏高原雨季的客观监测方法及其近60年的变化趋势

本文通过对青藏高原降水季节演变特征的分析,选取日降水量和降水频率两个特征量来定义青藏高原各站点及全区的雨季,揭示了1961—2019年青藏高原雨季开始时间、结束时间、雨季长度和总雨量等的气候和变化特征.分析发现,青藏高原雨季的开始自东向西推进,而结束西早东晚,雨季持续时间自东向西缩短,雨季雨量东多西少.就青藏高原整体而言,雨季开始的平均日期在5月4日,结束的平均日期在10月15日,雨季平均持续163天,雨季雨量平均为413.2 mm.近60年,青藏高原雨季发生了显著变化,表现为开始时间提前、结束时间推迟、雨季延长、雨量增多.青藏高原各站点雨季的变化具有一定的区域性差异,主要表现为：高原雨季的开始整体提前,但是,高原东部边缘雨季开始提前的变化幅度相对较小;高原雨季的结束时间在南部和北部提前而在中部和东部推后;高原大部地区雨季雨量增多,但南部边缘等部分地区雨季雨量有所减少.

The objective monitoring method of the Tibetan Plateau rainy season and its changing trend over the past 6 decades

In this study, an objective monitoring method is proposed to define the Tibetan Plateau rainy season, based on daily precipitation and precipitation frequency. Then the climatic characteristics and changing trends of the onset, end, duration, and precipitation amount of the rainy season from 1961 to 2019 are investigated. The results show that the rainy season on the Tibetan Plateau begins earlier in the east than in the west but ends earlier in the west than in the east. Therefore, the duration of the rainy season shortens from the east to the west, and the total precipitation is higher in the east than in the west. The Tibetan Plateau rainy season lasts 163 days from May 4 to October 15 climatically. The average total amount of precipitation during the rainy season is 413.2 mm. From 1961 to 2019, the Tibetan Plateau rainy season changed significantly, starting earlier and ending later, with longer duration and more precipitation. The change in the rainy season is not uniform across the Tibetan Plateau. The onset of the rainy season advanced across most Tibetan Plateau, but the magnitude of change is small in the eastern fringe. The end of the rainy season advanced in the north and south but was postponed in the center and east. The rainy season precipitation increased in most areas of the Tibetan Plateau but decreased in some areas of the southern margin.