Post on 06-Jan-2016
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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