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Global Variability of Mesoscale Convective System (MCS) Anvils

Global Variability of Mesoscale Convective System (MCS) Anvils. Jian Yuan Robert A. Houze Department of Atmospheric Sciences, University of Washington. This Talk. 1-MCS identification 2-Separation of MCS anvil from rain 3-MCS anvil cloud structure viewed by CloudSat. Data and Methodology.

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Global Variability of Mesoscale Convective System (MCS) Anvils

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  1. Global Variability of Mesoscale Convective System (MCS) Anvils Jian Yuan Robert A. Houze Department of Atmospheric Sciences, University of Washington

  2. This Talk • 1-MCS identification • 2-Separation of MCS anvil from rain • 3-MCS anvil cloud structure viewed by CloudSat

  3. 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)

  4. Step 1: Identify MCS Precipitating Cores TB11

  5. Choosing Rain Rate Thresholds Ocean Land

  6. Latent Heating within 1 mm/h threshold Areas of Different Sizes and Heights MCS MODIS 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

  7. Annual Mean Occurrence of MCS Precipitating Cores

  8. Step 2: Identify Total Cloud Area of MCS

  9. CloudSat “high cloud” PDF(tops above 10 km) TB11 (Ko) MODIS CloudSat High Cloud Thickness (km)

  10. High cloud systems Identification Locate High Clouds Find Cold Centers Length Identify Cloud Systems Identify MCS Systems Raining systems Length

  11. Active MCSs and other cloud Features Two conditions for active MCS: • Total raining areas as a whole meets MCS requirements. • 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)

  12. Comparison of Active MCS cloud systems Small: Rain +Anvil Area < 10000 km2Large: Rain +Anvil Area > 22500 km2 Small Large

  13. Comparison of Active MCS cloud systems “Cold”: min Tb11<208K “Warm”: 220>min Tb11208K Cold Warm Whole year

  14. Step 3: Analyze anvil structure

  15. 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

  16. 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

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

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

  19. 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

  20. End This presentation was supported by NASA Grant NNX07AQ89G

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