内蒙古极端降水特征及预报

Characteristics and Forecast of Extreme Pre-cipitation in Inner Mongolia

摘要: 极端天气事件是全球气候变化研究的热点，而中纬度内陆半干旱地带出现极端降水则是气象学面临的新问题。近年内蒙古地区夏季暴雨多发，2012年到2019年逐年出现极端降水事件的站次为25次、26次、12次、31次、12次、22次、47次，2019年无极端降水事件。本文采用1954年至今的历史降水资料、2011年至今的常规气象观测、NCEP再分析资料，分析内蒙古极端降水与特征，总结其与暴雨的预报指标异同，结果表明：1) 内蒙古极端降水阈值范围15.3~120.9毫米，并呈现西低东高的态势。阿拉善盟西部极端降水阈值 ≤ 25毫米，为最小；兴安盟、呼伦贝尔市中东部极端降水阈值最大，为90~110毫米。2) 内蒙古极端降水次数呈现增多趋势，年平均10.19次。1988年后，内蒙古极端降水次数明显增多。3) 内蒙古极端降水频次空间分布较为分散，大值中心在内蒙古中部及东北部，0.12~0.48次/年。4) 内蒙古极端降水、暴雨的天气型均可分为北槽南涡型、西来槽型、冷涡型、切变型四类。北槽南涡型均是最常见类型，西来槽型次之，冷涡型、切变型较少。5) 极端降水、暴雨四类天气型中，预报指标具有一致的差异性。极端降水CAPE阈值比暴雨高。K指数接近。极端降水低层比湿与暴雨阈值相近或更大。极端降水低层T-Td阈值下限接近或小于暴雨，上限更大，即上干下湿更加明显。低空700 hPa南风到达的纬度值极端降水与暴雨相近或纬度低于暴雨，南风风速阈值高于暴雨。极端降水Pw阈值明显高于暴雨。

Abstract: Extreme weather events are a hot topic in global climate change research, and extreme precipitation in mid-latitude inland semi-arid areas is a new problem for meteorology. Rainstorms have frequently occurred in Inner Mongolia in recent years, and from 2012 to 2019, the station numbers of extreme precipitation events occurred each year respectively are 25, 26, 12, 31, 12, 22, 47, and 0. In this paper, based on historical precipitation data from 1954 to the present, conventional meteorological observations from 2011 to the present, and NCEP reanalysis data, extreme precipitation and characteristics in Inner Mongolia were analyzed, and the similarities and differences between the forecast index and heavy rain were summarized. The results show: 1) The threshold of extreme precipitation in Inner Mongolia ranges from 15.3 to 120.9 millimeters, showing a low trend in the west and high in the east. The min extreme precipitation threshold appears at the western part of Alxa League, with the value below 25 mm, and the max appears at the central and eastern parts of Xing’an League and Hulunbuir, with the value ranging from 90 to110 mm. 2) The number of extreme precipitation events in Inner Mongolia showed an increasing trend, with an annual average of 10.19. After 1988, the number of extreme precipitation in Inner Mongolia increased significantly. 3) The spatial distribution of extreme precipitation frequencies in Inner Mongolia is relatively scattered, with large value centers in central and northeastern Inner Mongolia at 0.12 to 0.48 times/year. 4) The weather patterns of extreme precipitation and heavy rain in Inner Mongolia can be divided into north trough south vortex type, west trough type, cold vortex type and shear type. The northern vortex and southern vortex are the most common types, followed by the western vortex and the cold vortex and shear types are the least. In the four types of weather patterns of extreme precipitation and heavy rain, the forecast indicators have consistent differences. CAPE of the extreme precipitation threshold is higher than the heavy rainfall, while K index of the extreme precipitation threshold is close with the heavy rainfall. The specific humidity in low level of extreme precipitation is similar to or greater than the threshold of wet and heavy rainfall. The lower limit of the T-Td threshold for extreme precipitation is close to or less than the heavy rain, and the upper limit is greater, that is, the upper-dry and lower-wet state is more obvious. The latitude value reached by the southerly wind of low level in 700 hPa is similar to the torrential rain or the latitude is lower than the torrential rain. The Pw threshold of extreme precipitation is significantly higher than the heavy rain.