Diurnal Variations of Precipitation during the Warm Season over China:1954-2001

【摘要】：正The spatial distribution and seasonal change of diurnal variations of precipitation during the warm season(May to September) over China were analyzed using 48-year hourly data from 62 rain gauges during 1954-2001.Nocturnal precipitation predominates for the stations over the Tibetan Plateau as well as in southwest and northwest China.For stations to the east of about 110°E,daytime precipitation predominates in the northern and southern part,whereas nocturnal precipitation predominates in the middle and lower reaches of the Yangtze River and the North China Plain.Further,the magnitude of diurnal variations first decreases and then increases from the south toward the north.The significant diurnal variations in vertical circulation(stronger during the day and weaker at night),the meso-local-scale mountain-valley winds,and the nighttime cooling of cloud tops could be the processes behind the nocturnal rain in the western part of China(to the west of about 11 CPE).Daytime precipitation in the eastern part of China(to the east of about 110°E) could be attributed to the moist convection connected with solar heating.The morning peaks for stations in the middle and lower reaches of the Yangtze River and the North China Plain seem to be connected with the advance and retreat of the East Asian summer monsoon.The morning maxima at coastal stations may be mainly attributed to the local land-sea breeze.The seasonal changes of the diurnal variations for the western part of China are relatively small,with nighttime precipitation maxima remaining fairly constant during the warm season.This part is not directly influenced by the monsoon.For most of the stations in the eastern part,the morning peaks tend to be strengthened/weakened along with the East Asian monsoon's advancing/retreating.