关键词: 降水, 日变化, 雨强, 持续时间, 乌鲁木齐

Abstract: Based on hourly precipitation data from May to September during 1991—2010 from Urumqi meteorological station, the features of rainfall change during recent 20 years were analyzed. Results showed that the diurnal variations of hourly precipitation and rainfall frequency were consistent. The peaks of hourly rainfall and rainfall frequency both occurred from 20:00 to 11:00, and the minimum value occurred at 16:00. The frequency of rainfall less than or equal to 1.0 mm·h-1 was the most, which was followed by the frequency of rainfall great than or equal to 1.1 mm·h-1 but less than or equal to 3.0 mm·h-1. Nevertheless, the contribution of the latter was the biggest to precipitation. Different magnitudes of precipitation intensity had some different yearly change. The frequency of light rain was the most, the second were moderate rain and heavy rain, and the least was torrential rain. In a day, light rain, moderate rain and heavy rain occurred with the most frequency at the first half of the night, torrential rain at afternoon. During a year, light rain occurred with the most frequency in the middle of July, moderate rain in the middle of May, heavy rain in mid-to-late May, and torrential rain in early and middle of May, middle of July, and late August. The peaks of rainfall events with duration of 1-3 hours occurred at the first half of the night, that with duration of 4-6 hours and 7-9 hours often appeared at night, and that with 10-12 hours duration often appeared in the afternoon and after midnight. The inter-annual change of total rain days is these 20 years in Urumqi was not significant. Compare to during 1991-2000, the torrential rain days increased during 2001-2010, while the days of the other magnitudes decreased.

Key words: rainfall, diurnal variation, rainfall intensity, rainfall duration, Urumqi