Mesoα－ γScale Structures of Heavy Rainfall System in Yangtze River in Meiyu Fro

nt

Liu Liping Ruan Zheng State Key Laboratory of Severe Weather,

Chinese Academy of Meteor. Sciences

Contents

• Introduction

• Observation system and data

• Mesoα β γ Structure of Rain Band

• Summary

Introduction

In moonsoon season, the heavy rain systems in the Yangtze River often produce flood. The basic, crucial theoretic problems and scientific issues concerning the three-dimension mesoscale structures of convective precipitation system still remain to be solved. The field experiment was conducted by the Project of National Key Fundamental Research Program “China Heavy Rain Experiment and Study” in Yangtze River.

In July 22, 23, the heavy rainfall over middle reach of Yangtze River was observed by dual Doppler radar systems. Now we use satellite and Doppler radar data to analyze the meso-α,βandγstructures and their processes.

• meso α:Satellite and Doppler radar network )

• meso β:Dual Doppler radar

• meso γ: Radial velocity of radar

Observational system in middle reach of Yangtze River

1 dual Doppler radar system

3 S band Doppler radar system

7 Sounding Stations

Meso α scale Structure of heavy rainfall A meso- α rain band(1500km) was over Yangtze River, rain band is divided into Stritiform cloud and convective cloud. The meso- β cloud clutters have lifetime short than 6 hour, and with a width less than 100km. The cloud move toward northeast.

11 ： 19, July 22Radar Reflectivity by Changde Radar

Tbb

18 ： 59

23 日 2 ： 36

2 ： 36, July, 23

Vertical Structures of Rain band

Bright band echo

Mosaic of Radar Network (Yicahng, Jingzhou and Changde)

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Daily precipitation (08:00 July 22 to 08:00 23 July)

Meso-β structures of rain band

1 Precipitation distribution

2 Three-dimensional structures of wind field

The Rainfall rate and Height-Time map of radar reflectivity in Jinzhou Station near radar sit

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There are six convective cells to pass the station and

produce the heavy rain .

YichangJingzhou

Dual Doppler radar system by Yichang and Jingzhou Radars

9 ： 48 17 ： 00  

11 ： 08 17 ： 49

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CAPPI of wind field in 2km level at 12 ： 25,July 22

Vertical structure of wind field.

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CAPPI of wind field in 1.5km level at 02:26 July 23

Meso-γ structures

The development of meso-γ scale Convective echo, meso-scale vortex and outflow

 图 8 11 ：一次“新回波在右后侧生成的右移对流云”的雷达回波演变过程

The right back building echo

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14:00

14:00

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Reflectivity (Z) and Radial Velocity （ V ）

Outflow ?

12:24 12:36

Mesoscale Cycle (6k between two velocity centers,20m/s wind shear)

Summary •Satellite, Doppler radar network and Dual-Doppler radar data are used to analyze the mesoscale structures of heavy rainfall in Meiyu Front.

•For the meso-αstructure, the rain band has a length of more than 1000km. The radar echo can be divided into two parts: Stritiform and convective echo. •For the meso β scale, the wind shear below 4km level and low-level-jet are found in the heavy rainfall area. The convective activity is related with the disturbance of wind shear. The convergence and divergence occurred below 4km level.

•The right back building echo and mesoscale cycles in meso- γ scale are found in strong echo. The strong echo move to northwestern area.