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气象:2020,46(8):1001-1014
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强西南急流背景下湘桂边界两次预报失败的暖区暴雨个例分析
付炜,唐明晖,叶成志
(湖南省永州市气象台,永州 425000; 气象防灾减灾湖南省重点实验室,长沙 410007; 湖南省气象台,长沙 410007)
Analysis of Two Forecast Failure Cases of Warm-Sector Rainstorms on Hunan-Guangxi Border Area in Severe Southwest Jet
FU Wei,TANG Minghui,YE Chengzhi
(Yongzhou Meteorological Observatory of Hunan Province, Yongzhou 425000; Key laboratory of Preventing and Reducing Meteorological Disaster, Changsha 410007; Hunan Meteorological Observatory, Changsha 410007)
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投稿时间:2019-07-10    修订日期:2020-06-13
中文摘要: 利用常规观测资料、FY-2G卫星黑体亮温(TBB)资料、多普勒天气雷达资料以及ERA-Interim再分析资料,对2016年5月5日(以下简称“16·5”过程)和2018年4月23日(以下简称“18·4”过程)两次强西南急流背景下的暖区暴雨预报失败案例进行对比分析。结果表明:两次暖区暴雨过程的水汽分别来源于925 hPa西南急流和显著西南风,“16·5”过程的水汽辐合强度及范围较“18·4”过程更强、更广,导致暴雨出现的范围更广;超低空急流断裂处的辐合区叠加在湘桂边界南岭山脉特殊地形上,动力抬升触发及维持作用更加明显。大气层结稳定度对暖区暴雨的发生具有重要指示作用,“16·5”过程大气不稳定度更大导致了更强的暖区暴雨;两次暖区暴雨的湿层厚度较锋面暴雨浅薄,中低层的显著湿区导致了暴雨或大暴雨的出现;“16·5”暖区暴雨发生过程中能量长时间的维持,是西南低空急流暖湿输送导致高温、高湿、高能的对流不稳定层结反复重建的结果,最终导致强降水持续,进而导致了更大的总降水量。“18·4”过程冷锋前100 km外相对较弱的水汽辐合区,是暖区暴雨的一个重要预报指标;两次过程中高空槽的经向度是决定暖区暴雨范围大小的重要因子。地形在两次暖区暴雨过程中的降水增幅作用明显,降水中心主要出现在山谷或盆地的迎风坡位置;两次暖区暴雨与边界层的动力辐合、水汽供应关系密切,边界层辐合抬升和地形的作用明显,短期预报需重点关注边界层辐合区及特殊地形位置,对数值预报进行适当订正。雷达风廓线资料揭示了两次暖区暴雨过程西南风厚度的差异对降水强度的影响;垂直风切变的增强、环境风偏弱特征在这两次过程中分别提供了强降水持续维持的信息,对暴雨的预报预警的升级有一定的指示作用。
Abstract:Based on the conventional upper-air and surface observations, temperature of brightness blackbody (TBB) from FY-2G Satellite, Doppler weather radar data and reanalysis data from ERA-Interim, two forecast failure cases of warm-sector rainstorm forecasts in severe southwest jet on 5 May 2016 and 23 April 2018 are analyzed. The results are as follows. The water vapor sources of the two warm-sector rainstorms came from strong southwest jet at 925 hPa and southwest wind respectively. The water vapor convergence in the former rainstorm had higher intensity and wider range than the latter, resulting in a broader range of torrential rain. The superposition between the strong convergence and the special topography of Nanling Mountain on the Hunan-Guangxi border could result in a stronger dynamic uplift and a longer lifetime of rainstorm. Strong atmospheric instability in the former process led to more severe rainstorms in warm sectors. The wet layers of the two rainstorms were more shallow than that in typical frontal rainstorms. And the significant wet sectors in the middle and lower layers led to the occurrence of rainstorms. The energy maintained a long time in the former process which was caused by the warm moist air mass transport of the low-level jet that led to repetitive formation of low-level convective instability with high temperature, high humidity and high energy, finally resulting in longer rainfall duration and more precipitation. The weaker moisture convergence zone ahead of the front was an important predictor of the warm-sector rainstorms in the April 2018 process. So attention must be paid to the relationship between the trough and warm-sector rainstorms. The length of meridional trough was an important factor for the precipitation zone forecast in the warm-sector rainstorms. The topography contributed to the precipitation in these two rainstorms. The rainstorm centers mainly appeared on the windward slope of valleys or basins. The rainstorms were closely related to the dynamic convergence of the boundary layer and the water vapor supply. Therefore, in forecasting operation, we should pay attention to the convergence area of the boundary layer, the special topographies and locations, and make appropriate empirical revisions to numerical forecasts so as to improve its accuracy. The radar wind profile data analysis showed that the enhancement of vertical wind shear can indicate the occurrence of rainstorms. The differences of the southwest wind thickness can reflect the difference of precipitation intensity, providing an important reference for the ascertaining of the alert level.
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基金项目:中国气象局气象预报业务关键技术发展专项[YBGJXM(2017)1A-10、YBGJXM(2018)1A-10]、湖南省气象局预报员专项(XQKJ17C006)和湖南省气象局重点项目(XQKJ17A002)共同资助
引用文本:
付炜,唐明晖,叶成志,2020.强西南急流背景下湘桂边界两次预报失败的暖区暴雨个例分析[J].气象,46(8):1001-1014.
FU Wei,TANG Minghui,YE Chengzhi,2020.Analysis of Two Forecast Failure Cases of Warm-Sector Rainstorms on Hunan-Guangxi Border Area in Severe Southwest Jet[J].Meteor Mon,46(8):1001-1014.