Global Variability of Mesoscale Global Variability of Mesoscale Convective System (MCS) AnvilsConvective System (MCS) AnvilsGlobal Variability of Mesoscale Global Variability of Mesoscale

Convective System (MCS) AnvilsConvective System (MCS) Anvils

Jian YuanJian Yuan

Robert A. HouzeRobert A. Houze

Department of Atmospheric Sciences, University of WashingtonDepartment of Atmospheric Sciences, University of Washington

CloudSat Science Team Meeting, 29 July 2009, Madison, WI

This Talk

• 1-MCS identification

• 2-Separation of MCS anvil from rain

• 3-MCS anvil cloud structure viewed by CloudSat

Data and Methodology

Analysis of MCS anvil cloud compositeCloudSat (GEOPROF-2B)

AMSR-E rain & MODIS TB11AMSR-E rain & MODIS TB11 MODIS TB11

MCSs (raining center + non-raining anvil clouds)MCSs (raining center + non-raining anvil clouds)

MCS Precipitating CoresMCS Precipitating Cores High Cloud SystemsHigh Cloud Systems

1 2

3

Step 1: Identify MCS Precipitating Cores

TB11

Choosing Rain Rate Thresholds

Ocean

Land

Latent Heating within 1 mm/h threshold Areas of Different Sizes and Heights

And

•At least 10% of the raining area has R>6 mm/hr

MO

DIS

AMSR-E Define MCS Precipitating Core as 1 mm h-1 threshold area:

•covering > 2000 km2 = (45 km)2 •with TB11 of the coldest decile of the

raining area < 220oK

MCS

Annual Mean Occurrence of MCS Precipitating Cores

Step 2: Identify Total Cloud Area of MCS

CloudSat “high cloud” PDF(tops above 10 km)

TB

11 (

Ko)

High Cloud Thickness (km)CloudSat

MO

DIS

High cloud systems Identification

Raining systems

Locate High Clouds Find Cold Centers

Identify Cloud Systems Identify MCS Systems

Leng

th

Length

Active MCSs and other cloud Features

Two conditions for active MCS:

1. Total raining areas as a whole meets MCS requirements.

2. The largest raining element is a part of a MCS and it takes at least 70% of total raining areas within the system.

• Active MCS cloud system (meet both 1 and 2)

• Precipitating high cloud systems not associated with active MCSs -- contain active raining systems but do not satisfy 1. or 2.

• Non-Precipitating high cloud systems (no rain)

Comparison of Active MCS cloud systems Small: Rain +Anvil Area < 10000 km2

Large: Rain +Anvil Area > 22500 km2

Small

Large

Comparison of Active MCS cloud systems “Cold”: min Tb11<208K

“Warm”: 220>min Tb11208K

Cold

Warm

Whole year

Step 3: Analyze anvil structure

To make sure we aren’t analyzing precipitating anvils--

• Maximum reflectivity between 1.25 to 2.5 km to be < -10 dBZ

• Maximum reflectivity around the surface level to be > 25 dBZ

Require

CFADs of thick anvil clouds (6-11 km)

• Sampled over open water in the West Pacific maritime continent area

• Broader distribution of reflectivity found in anvils closer to raining area

Continental thick anvil clouds (6-11 km) close to raining area suggests more “convective” microphysics

CFADs of thin anvil clouds (2-6 km) are less sensitive to geographical regions

•Objective analysis of MODIS TB11 and AMSR-E rain product leads to reasonable global distribution of MCSs

•Anvils can be separated from the raining core of the MCS for analysis

•CloudSat GEOPROF-2b shows internal structure of anvils

•Thick anvils have broader distribution of reflectivity closer to raining area

•Continental anvils consistent with more convective microphysics

•Thin anvils are less impacted by convective core

SummarySummary

EndThis presentation was supported by NASA Grant NNX07AQ89G