伊宁市主汛期降水日变化特征

Daily Variations Characteristics of Rainfall in Flood Season in Yining City

基于伊宁市2007—2011年逐时自动降水资料,分析主汛期(5—8月)降水日变化特征。结果表明,降水主要集中在22:00至翌日09:00,最大值出现在02:00,其次为18:00至翌日19:00,最小值出现在13:00。降水频次的高值区在23:00至翌日11:00,降水最不易产生的时间为16:00。降水强度最高值出现在18:00,其次为19:00,此时间段也是累积降水量高值区,降水强度最低值13:00也是累积降水的低值区。降水强度和降水频次与降水量的相关性较高。在≥0.1 mm、≥1 mm和≥3 mm的逐时降水频次中,夜晚和早晨出现降水的次数较下午多,其中,≥0.1 mm的降水次数最多。降水主要以夜雨为主,且以3 h的短时间降水贡献率最大。总云量和低云量与降水量呈显著正相关。

The formation of precipitation variation is often closely linked with all sorts of daily variation of atmospheric phenomena,is one of the most main oscillation phenomenon in the earth's atmosphere. Based on the hourly automatic rainfall data in Yining station from 2007 to 2011,the diurnal variation characteristics of rainfall was analyzed in main flood season( 5- 8 month). The results showed that the rainfall was mainly concentrated at 22: 00 to 09: 00 next day of Beijing time,with the maximum rainfall value appearing at 02: 00 next day,and it took second place at 18: 00 to 19: 00 next day with the minimum value appearing at 13: 00 next day. The high value of rainfall frequency occurred at 23: 00 to 11: 00 next day,it was not easy to generate at16: 00. The highest rainfall intensity generally appeared at 18: 00 and the higher intensity was at 19: 00,which was consistent with the accumulated precipitation. The minimum rainfall intensity generally occurred at 13:00,corresponding to the low value of accumulated precipitation. The correlation of rainfall intensity and accumulated precipitation was higher than the rainfall frequency and accumulated precipitation. According to the different levels,defined by the hourly rainfall of ≥ 0. 1 mm or ≥ 1 mm or ≥ 3 mm,respectively,rainfall easily occurred at night or morning than afternoon,the rainfall( hourly rainfall ≥ 0. 1 mm) was more frequent than other levels. Precipitation mainly occurred in night,and the 1- 3 hour rainfall duration made the greatest contribution to the total rainfall. The total and low cloud cover both showed a significant positive correlation with rainfall. The above result is helpful to understand rainfall characteristics in yining city thoroughly.