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The Convective Cloud Population during the Buildup of the Madden- Julian Oscillation AGU Fall Meeting, San Francisco, 7 December 2011 R. Houze, S. Brodzik, J. Yuan University of Washington
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The Convective Cloud Population during the Buildup of the Madden- Julian Oscillation Three perspectives: A-Train DYNAMO TRMM Still going on!
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The MJO
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Wheeler and Hendon 2004 Phases of the MJO
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TRMM
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Phase 1Phase 5 Phase 7Phase 3 Frequency of radar echo in “broad stratiform regions” of MCSs
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Phase 7Phase 3 Phase 1Phase 5 Frequency of radar echo in “deep convective cores”
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Phase 7Phase 3 Phase 1Phase 5 Frequency of “shallow isolated” radar echoes (anomaly)
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Variation of Echo Category with MJO Phase
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A-Train
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Mesoscale Convective Systems (MCSs) have cold tops and large intense raining cores Both raining and anvil components are identified using A-Train instruments
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CMCSs SMCSs HCSs excl.MCSs non-HCSs Percentage % a) Cloud coverage b) Contribution to precipitation “Connected MCSs” “Separated MCSs” Other High Cloud Systems Non-high-cloud Systems
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DYNAMO
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Cloud Structures (NCAR S-PolKa radar)
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Suppressed phase: Lines of non- precipitating clouds
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Suppressed phase: Clouds at cold pool boundaries
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Suppressed phase: Clouds at cold pool boundaries
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4 km 8 km graupel small ice large non-melting ice heavy rain Small cumulonimbus melting snow
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Small, weak stratiform area
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Active phase: Large mesoscale system Stratiform Convective
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5 km 10 km Robust melting layer in Large MCS
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Convection feeding into a large MCS
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Shear
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Low-level westerly component, upper-level easterly component NE SW
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Biggest MCS of first active phase: weak unidirectional shear
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Larger-than-mesoscale Organization
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Giant Rings of Convection
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Westerly Surges
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End This research is supported by NSF grant ATM AGS-1059611, DOE grant DE-SC0001164/ER-64752, and NASA grants NNX10AM28G and NNX10AH70G
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Extras
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Identify each contiguous 3D echo object seen by TRMM PR Convective component Stratiform component Extreme characteristic Contiguous 3D volume of convective echo > 30 dBZ Top height > 8 km “Deep convective core” Horizontal area > 800 km 2 Horizontal area > 800 km 2 “Wide convective core” Extreme characteristic Contiguous stratiform echo with horizontal area > 50 000 km 2 “Broad stratiform region” Categories of radar echoes seen by TRMM
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MODIS TB11 + AMSR-E ( Yuan and Houze 2010) combined to find“cold centers” & “raining areas” Use 260 K threshold Locate 1 st closed contour Use 1 mm/h threshold for rain rate Associate pixels with nearest cold center Use 6 mm/h threshold for heavy rain
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1 2 3 4 5 6 7 8 Phase
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Pressure (hPa) Phases 1,8 Phases 2,3 Phases 4,5 Phases 6,7 50 E 100 E 150 E 200 E DYNAMO Mixing ratio anomaly 1000 600 200 1000 600 200
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Descent of easterlies
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