肖柳斯,张华龙,张旭斌,冯璐,谌志刚,戴光丰. 2021. 基于TRAMS集合预报的“5.22”极端降水事件可预报性分析[J]. 气象学报, (0):-, doi:10.11676/qxxb2021.058
基于TRAMS集合预报的“5.22”极端降水事件可预报性分析
Predictability analysis of the extremely heavy rainfall in the Pearl River Delta on 22 May 2020 using TRAMS-based ensemble prediction system
投稿时间:2020-10-21  修订日期:2021-06-23
DOI:10.11676/qxxb2021.058
中文关键词:  集合预报,热带中尺度集合预报系统,极端降水,可预报性
英文关键词:Ensemble forecast, TRAMS, Extremely heavy rainfall, Predictability
基金项目:省自然科学基金,国家自然科学基金
作者单位邮编
肖柳斯 广州市气象台 511430
张华龙 广东省气象台 510060
张旭斌 中国气象局广州热带海洋气象研究所 510060
冯璐 中国气象局广州热带海洋气象研究所 510060
谌志刚 广州市气象局 511430
戴光丰 中国气象局广州热带海洋气象研究所 510060
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中文摘要:
      2020年5月22日珠三角地区出现了一次极端强降水天气,最大滑动小时雨量201.8 mm,3小时雨量达到351 mm。为探讨此次极端强降水的关键预报因子及可预报性问题,对热带中尺度集合预报系统(TRAMS-EPS)降水预报产品进行检验评估和敏感性分析,结果表明:与欧洲中心集合预报系统(ECMWF-EPS)相比,TRAMS-EPS的好成员对本次过程降水的强度及空间位置的预报结果与实况更接近,但极端性仍有欠缺。该组成员较好的预报能力来自于对低涡和(超)低空急流的演变特征,以及两者强度和位置耦合的有效预测。好成员组预报珠三角东部(超)低空急流南风分量较强,有利于低涡缓慢移动和气旋性辐合增强,致使降水持续时间长、效率高。而低涡自身发展又反馈于急流强度变化,好成员组较准确地刻画了增强的低涡环流反馈导致急流小范围加速的耦合特征。而其他成员组预报的低涡和(超)低空急流的耦合位置偏东偏南,辐合强度偏弱,导致降水强度或落区出现偏差。此外,强降水致使冷池形成,并增强激烈的冷暖气团对峙(水平温度梯度达0.23~0.76 ℃/km),有利于中尺度辐合线维持、加强对流后向传播并产生极端雨量。但TRAMS-EPS两组成员在预报中尺度系统的组织性和传播特征方面均存在明显不足,限制了集合预报系统对极端降水的预报能力。
英文摘要:
      An extremely heavy rainfall occurred in the Pearl River Delta region on May 22, 2020 with the maximum hourly moving accumulated precipitation of 201.8 mm, and the rainfall reached 351 mm in 3 hours. In order to investigate the key forecasting factors and the predictability of this case, the evaluation and sensitivity analysis of precipitation forecasts of the mesoscale ensemble prediction system based on the Tropical Regional Atmosphere Model for the South China Sea (TRAMS-EPS) are carried out. The results show that, compared with the ECMWF Ensemble Prediction System (ECMWF-EPS), good members of TRAMS-EPS have better ability to capture the intensity and spatial distribution of heavy rainfall, but still lack of extremity. The better prediction ability of these members comes from the effective prediction of the evolution characteristics as well as the intensity and location coupling of low vortex and low-level jet (or boundary layer jet). The strong south wind component of the low-level jet (or boundary layer jet) over the eastern part of the Pearl River Delta is conducive to the deceleration of the low vortex velocity and the enhancements of cyclonic convergence, resulting in a long duration of precipitation and high efficiency. In addition, the development of the low vortex itself is fed back to the change of the intensity of low-level jet (or boundary layer jet). The coupling characteristics of the low-level jet (or boundary layer jet) accelerated in a small range due to the feedback of the enhanced vortex circulation, which are accurately described by the good member group. However, the coupling position of low vortex and low-level jet (or boundary layer jet) predicted by other member groups is east and south, and the convergence intensity is weak, which leads to deviation of rainfall intensity or precipitation area. In addition, the heavy rainfall results in cold pool, and intensifies the confrontation between surface warm ridge and cold pool( horizontal temperature gradient of 0.23~0.76 ℃/km), which is conducive to maintaining mesoscale convergence line, strengthening the backward propagation of convection and therefore generating extreme rainfall. However, all members of TRAMS-EPS have obvious deficiencies in forecasting the organization and propagation characteristics of the mesoscale systems, which limits the ability of TRAMS-EPS to predict the extremely heavy rainfall event.
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