AGU Annual Meeting, San Francisco, 11 December 2013.
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Transcript of AGU Annual Meeting, San Francisco, 11 December 2013.
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
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
The convective scales
Examples from DYNAMO
Examples
Broad stratiform
Deep coresShallow isolated
Wide cores
From Powell and Houze 2013
~½-1 h
~5-10 h
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
Convective Stratiform
Kingsmill and Houze 1999
~50 aircraft surveys in TOGA COARE
x
Kingsmill and Houze 1999
~50 aircraft surveys in TOGA COARE
x
Convective Stratiform
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
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
Intermediate scales• Smaller than MJO• Larger than convective entities
S-PolKa Radar Rainfall at Addu Atoll in DYNAMO
Powell and Houze 2013
OLR
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
Zuluaga and Houze 2013
Composite large-scale divergence and vertical motion during 2-day rainfall episodes
Divergence
Variation of the DYNAMO radar echo population relative to a precpitation episode
Zuluaga and Houze 2013
Composite of all 2-day rainfall episodes
The largest scale
Vertical structure of the MJO
Moncrieff 2004
~10,000 km~30-60 days
Vertical structure of the MJO
Moncrieff 2004
~10,000 km~30-60 days
Coupling with the
changeable convective population
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
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
EndThis research was supported by
NASA grants NNX10AH70G, NNX13AQ37G and NNX13AG71G NSF grant AGS-1059611
DOE grant DE-SC0008452
Extra Slides
…Barnes talk & upcoming paper
ConvectiveConvective entities
DYNAMO radar data composited relative to the mesoscale airflow
DYNAMO radar data composited relative to the mesoscale airflow
ConvectiveConvective entities0°C
Stratiform entities
…Barnes talk & upcoming paper
Stretched Building Block HypothesisMapes et al. 2006
Large-scale wave structure at the same times
Cloud population at three different times
Vertical structure of the MJO
Moncrieff 2004
~10,000 km
Upper-level eastward propagating Kelvin waves?
…Scott Powell’s poster
u’ at 150 mb
DYNAMO