Transcript 090729Madison_CloudSatSciTeamV3_HouzeYuan.ppt

Global Variability of Mesoscale
Convective System (MCS) Anvils
Jian Yuan
Robert A. Houze
Department 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
1
2
AMSR-E rain & MODIS TB11
MODIS TB11
MCS Precipitating Cores
High Cloud Systems
MCSs (raining center + non-raining anvil clouds)
3
Analysis of MCS anvil cloud composite
CloudSat (GEOPROF-2B)
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
MODIS
MCS
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
And
• At least 10% of the raining area has R>6 mm/hr
Annual Mean Occurrence of MCS
Precipitating Cores
Step 2: Identify Total Cloud Area of MCS
MODIS TB11 (Ko)
CloudSat “high cloud” PDF
(tops above 10 km)
CloudSat High Cloud Thickness (km)
High cloud systems Identification
Length
Locate High Clouds
Find Cold Centers
Identify Cloud Systems
Identify MCS Systems
Raining
systems
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<208K
“Warm”: 220>min Tb11208K
Cold
Warm
Whole year
Step 3: Analyze anvil structure
To make sure we aren’t analyzing
precipitating anvils--
Require
• Maximum reflectivity between 1.25 to 2.5
km to be < -10 dBZ
• Maximum reflectivity around the surface
level to be > 25 dBZ
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
Summary
• 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
End
This presentation was supported by NASA Grant NNX07AQ89G