Cloud Resolving Simulation of a Local Heavy Rainfall Event on 26 August 2011 Observed in TOMACS
Cloud Resolving Simulation of a Local Heavy Rainfall Event on 26 August 2011 Observed in TOMACS
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DOI：
10.2151/jmsj.2018-027
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发表时间：
2018-02
影响因子：
3.1
通讯作者：
Kazuo Saito;Masaru Kunii;K. Araki
中科院分区：
文献类型：
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作者：
Kazuo Saito;Masaru Kunii;K. Araki
2011年8月26日，东京和神奈川县出现了约100毫米小时的局部强降雨。这场降雨是由一个中尺度对流系统（MCS）在一个静止锋附近发展而成，并缓慢向南移动。在使用地球同步多用途卫星快速扫描图像和密集的自动气象站网络进行的分析中，MCS的发展发生在东部（鹿岛那田）和南部（东京湾）的海风合并之后。日本气象厅（JMA）的非静力模式（NHM）的数值实验，水平分辨率为10和2公里，使用中尺度4D-VAR分析的JMA的初始条件往往预测的位置，强降雨区的观测位置以西。在利用日本气象厅全球集合预报系统（EPS）一周预报的扰动进行的中尺度集合预报中，东京附近的部分集合成员出现了强降水，但关东北部和北陆地区出现了假降水区。作为改进模式预报的尝试，我们对模式进行了修正，降低了水汽凝结诊断云量辐射的次网格偏差下限。在改进模式的模拟中，东京附近的地面温度增加了约1°C，强降水的位置得到了改善，但集合成员中北陆地区的假降水区也得到了加强，比控制运行带来了更好的预报。我们还进行了集成预测，使用基于NHM的奇异向量方法。其中一个集合成员使关东地区迎风面的低层大气不稳定，并抑制了北陆地区的假降水，NHM以2 km的水平分辨率很好地再现了局地暴雨的观测特征。根据观测、前人研究和数值模拟结果，提出了东南两股海风合并后形成低空辐合区引发深对流的概念模型。在这次暴雨过程中，偏北的环境风对南方海风的北侵起到了抑制作用，对东京附近局地暴雨的发生起到了重要作用。
A local heavy rainfall of about 100 mm h occurred in Tokyo and Kanagawa Prefecture on 26 August 2011. This rain was brought by a mesoscale convective system (MCS) that developed near a stationary front that slowly moved southward. In an analysis using geostationary multi-purpose satellite rapid scan images and dense automated weather station networks, development of the MCS occurred after the merging of sea breezes from the east (Kashima-nada) and the south (Tokyo Bay). Numerical experiments by the Japan Meteorological Agency (JMA) nonhydrostatic model (NHM) with horizontal resolutions of 10 and 2 km using mesoscale 4D-VAR analysis of JMA for initial conditions tended to predict the position of intense rainfall areas west of the observed positions. In the mesoscale ensemble forecast using perturbations from JMA’s one-week global ensemble prediction system (EPS) forecast, some ensemble members showed enhanced precipitation around Tokyo, but false precipitation areas appeared north of the Kanto and Hokuriku districts. As an attempt to improve the model forecast, we modified the model, reducing the lower limit of subgrid deviation of water vapor condensation to diagnose the cloudiness for radiation. In the modified model simulation, surface temperatures around Tokyo increased by about 1°C, and the position of the intense precipitation was improved, but the false precipitation areas in the Hokuriku district were also enhanced in the ensemble member which brought a better forecast than the control run. We also conducted an ensemble prediction using a singular vector method based on NHM. One of the ensemble members destabilized the lower atmosphere on the windward side of the Kanto district and suppressed the false precipitation in the Hokuriku district, and observed characteristics of the local heavy rainfall were well reproduced by NHM with a horizontal resolution of 2 km. A conceptual model of the initiation of deep convection by the formation of a low-level convergence zone succeeding merging of the two sea breezes from the east and south is proposed based on observations, previous studies, and numerical simulation results. In this event, the northerly ambient wind played an important role on the occurrence of the local heavy rainfall around Tokyo by suppressing the northward intrusion of the sea breeze from the south.