Journal of Arid Meteorology ›› 2020, Vol. 38 ›› Issue (2): 226-233.DOI: 10.11755/j.issn.1006-7639(2020)-02-0226

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Distribution Characteristics of Hourly Precipitation Probability in Southwestern China

PAN Jianhua   

  1. Sichuan Meteorological Observatory, Chengdu 610072, China
  • Online:2020-04-28 Published:2020-04-28

中国西南地区小时雨量概率分布特征

潘建华   

  1. 四川省气象台,四川 成都 610072
  • 作者简介:潘建华(1960— ),女,湖南冷水江人,高级工程师,主要从事决策气象服务工作. E-mail:scqxpjh@sina.com。
  • 基金资助:
    国家自然科学基金(41375059)和国家行业专项(气象)重点项目(GYHY201306022)共同资助

Abstract: Based on hourly precipitation data at 369 national meteorological stations from 1 April 2005 to 31 October 2017 in southwestern China, the frequency distribution and probability distribution fitted by Gamma function of hourly precipitation at 31 tap positions were analyzed comparatively. The results are follows as: (1) The frequency distribution curve of hourly precipitation at each station of southwestern China showed typical ‘L’ pattern, and the turning point of curve at most stations appeared from the second to the fifth tap positions. More than 80 percent of hourly precipitation at most stations concentrated at the first tap position, while the ratio of hourly precipitation was less than ten percent at the second tap position, the frequency between two taps decreased rapidly. The frequency of hourly precipitation at higher taps was smaller, and there was discontinuity. (2) Frequency of hourly precipitation at the first tap decreased with the increase of topographic height, while that at the tap of turning point increased with the increase of topographic height. (3) The fitting parameters of α and β of Gamma function were strongly related with topographic height. The higher height was, the higher α was, while the smaller β was, and vice versa. (4) Probability distribution of hourly precipitation at 95 percent and above stations of southwestern China could be fitted by Gamma function directly. The difference method and parameters change of Gamma function could reduce the great difference between frequency and probability at the first tap, which was beneficial to passing χ2 test of samples, and further the satisfying fitting result could be obtained.

Key words: hourly precipitation, frequency, probability, Gamma function fitting, turning point, topographic height

摘要: 利用中国西南五省市2005—2017年夏半年369个国家气象站逐小时降水量资料,针对31个档位的小时雨量频率分布和伽马函数拟合概率分布进行对比分析。结果表明:(1)中国西南地区小时雨量频率分布曲线均呈“L”型,大多数站点在第2、3、4、5档位出现拐点,且80%以上的小时雨量集中出现在第1档位,而在第2档位的不足10%,两档位间频率衰减剧烈;高档位的小时雨量出现频率极低,且多呈不连续状态。(2)小时雨量在第1档位的频率随着海拔高度的增加而减小,但拐点所在档位处的小时雨量频率则随海拔高度的增加而增大。(3)伽马函数拟合参数α和β与地形分布密切相关,海拔越高,α越大、β越小,反之亦然。(4)中国西南地区95%以上站点的小时雨量频率分布可用伽马函数拟合,少数未通过χ2检验的站点样本可通过统一的差分与参数控制方法获得满意的拟合结果。

关键词: 小时雨量, 频率, 概率, 伽马函数拟合, 拐点, 地形高度

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