agu annual meeting, san francisco, 11 december 2013
TRANSCRIPT
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Scales of Convective Activity in the MJO
Robert A. Houze, Jr.
With contributions from:
S. Powell, M. Zuluaga, H. Barnes, A. Rowe
AGU Annual Meeting, San Francisco, 11 December 2013
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The MJO scale
~30-60 days
TOGACOARE
West Pacific 1
2
3
7
8
5
6
4
“ActivePeriod”
~1-3 weeks
Wheeler & Hendon 2004
“ActivePeriod”
~1-3 weeks
IndianOcean
DYNAMO
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The convective scales
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Examples from DYNAMO
Examples
Broad stratiform
Deep coresShallow isolated
Wide cores
From Powell and Houze 2013
~½-1 h
~5-10 h
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TRMM radar shows how the scale of individual convective entities vary with phase of the MJO
Barnes and Houze 2013
Shallow Isolated Echoes
Deep Convective Cores
Broad Stratiform Regions
Wide Convective Cores
Active conditions
Suppressed conditions
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Convective Stratiform
Kingsmill and Houze 1999
~50 aircraft surveys in TOGA COARE
x
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Kingsmill and Houze 1999
~50 aircraft surveys in TOGA COARE
x
Convective Stratiform
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Wide convective elements and broad stratiform regions are like Moncrieff’s mesoscale layer model of deep tropical convection…
Moncrieff 1992
…mesoscale adjustment to shear and thermodynamic stratification
100-200 km
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DYNAMO radar data show microphysical stratification ~constant for both convective and stratiform entities
Melting snowGraupel
Dry snow
Small ice
Convective
Stratiform
Convective
Stratiform
Convective
Stratiform
% of observations
October November December
Rowe & Houze 2013
Melting snowGraupel
Dry snow
Small ice
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Intermediate scales• Smaller than MJO• Larger than convective entities
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S-PolKa Radar Rainfall at Addu Atoll in DYNAMO
Powell and Houze 2013
OLR
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Rain seen by the S-PolKa radar in
DYNAMO
Zuluaga and Houze 2013
October Active Period
November Active Period
December Active PeriodOccurred in “episodes”
separated by ~2-7 days
Filter and composite
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Zuluaga and Houze 2013
Composite large-scale divergence and vertical motion during 2-day rainfall episodes
Divergence
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Variation of the DYNAMO radar echo population relative to a precpitation episode
Zuluaga and Houze 2013
Composite of all 2-day rainfall episodes
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The largest scale
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Vertical structure of the MJO
Moncrieff 2004
~10,000 km~30-60 days
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Vertical structure of the MJO
Moncrieff 2004
~10,000 km~30-60 days
Coupling with the
changeable convective population
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Vertical structure of the MJO
Moncrieff 2004
~10,000 km~30-60 days
• Kelvin wave• Rossby wave• 2-7 day waves• Cloud-
humidity feedback
• Mid-latitude interaction
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Summary Convection in the MJO has multiple important scales
• Shallow isolated• Deep cores• Wide cores• Broad stratiform rain areas
How does convection accommodate systematically to
• Intermediate scale waves, which account for most of the rainfall
• Larger scale of the MJO itself
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EndThis research was supported by
NASA grants NNX10AH70G, NNX13AQ37G and NNX13AG71G NSF grant AGS-1059611
DOE grant DE-SC0008452
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Extra Slides
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…Barnes talk & upcoming paper
ConvectiveConvective entities
DYNAMO radar data composited relative to the mesoscale airflow
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DYNAMO radar data composited relative to the mesoscale airflow
ConvectiveConvective entities0°C
Stratiform entities
…Barnes talk & upcoming paper
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Stretched Building Block HypothesisMapes et al. 2006
Large-scale wave structure at the same times
Cloud population at three different times
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Vertical structure of the MJO
Moncrieff 2004
~10,000 km
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Upper-level eastward propagating Kelvin waves?
…Scott Powell’s poster
u’ at 150 mb
DYNAMO