The Convective Cloud
Population during the
Buildup of the MaddenJulian
Oscillation
R. Houze, S. Brodzik, J. Yuan
University of Washington
AGU Fall Meeting, San Francisco, 7 December 2011
The Convective Cloud
Population during the
Buildup of the MaddenJulian
Oscillation
Three perspectives:
TRMM
A-Train
DYNAMO
Still going on!
The MJO
Phases of
the MJO
Indian
Ocean
1
2
Wheeler and Hendon
2004
3
4
5
6
7
8
DYNAMO
TRMM
Frequency of radar echo in “broad stratiform regions” of MCSs
Phase 1
Phase 5
Phase 3
Phase 7
Frequency of radar echo in “deep convective cores”
Phase 1
Phase 5
Phase 3
Phase 7
Frequency of “shallow isolated” radar echoes (anomaly)
Phase 1
Phase 5
Phase 3
Phase 7
Variation of Echo Category with MJO Phase
A-Train
Mesoscale Convective Systems (MCSs) have
cold tops and large intense raining cores
Both raining and anvil components are
identified using A-Train instruments
a) Cloud coverage
b) Contribution to precipitation
SMCSs
HCSs excl.MCSs
Percentage %
CMCSs
“Connected MCSs”
“Separated MCSs”
Other High Cloud
Systems
non-HCSs
Non-high-cloud
Systems
DYNAMO
Cloud Structures
(NCAR S-PolKa radar)
Suppressed
phase:
Lines of nonprecipitating
clouds
Suppressed
phase:
Clouds at cold
pool boundaries
Suppressed
phase:
Clouds at cold
pool boundaries
Small cumulonimbus
small ice
large non-melting ice
graupel
8 km
melting snow
4 km
heavy rain
Small, weak
stratiform area
Active phase:
Large
mesoscale
system
Stratiform
Convective
Robust melting
layer
in
Large MCS
10 km
5 km
Convection feeding
into a large MCS
Shear
Low-level westerly component, upper-level easterly component
NE
SW
NE
SW
Biggest MCS of first active phase: weak unidirectional shear
Larger-than-mesoscale
Organization
Giant Rings of Convection
Westerly Surges
Conclusions
• Shallow isolated clouds
present all the time
• Stratiform regions have
the biggest variation
from suppressed to
active phases
• SF regions are associated with the largest MCSs
• SF regions can be extremely robust with strong
melting layers with melting graupel as well as snow
• Shear seems to inhibit stratiform region formation
• Convection has larger-than-mesoscale organization:
rings, westerly bursts,….
End
This research is supported by NSF grant ATM AGS-1059611, DOE grant DE-SC0001164/ER-64752, and
NASA grants NNX10AM28G and NNX10AH70G
Extras
Categories of radar echoes seen by TRMM
Identify each contiguous 3D echo object
seen by TRMM PR
Convective component
Stratiform component
Extreme characteristic
Extreme characteristic
Contiguous 3D volume of
convective echo > 30 dBZ
Contiguous stratiform echo
with horizontal area > 50 000 km2
“Broad stratiform region”
Top height > 8 km
“Deep convective core”
Horizontal area > 800 km2
“Wide convective core”
MODIS TB11 + AMSR-E (Yuan and Houze 2010)
combined to find“cold centers” & “raining areas”
Locate 1st
closed
contour
Use 260 K
threshold
Use 1 mm/h
threshold for
rain rate
Associate
pixels with
nearest
cold center
Use 6 mm/h
threshold for
heavy rain
1
2
3
4
5
Phase
6
7
8
Phases 1,8
200
600
1000
Phases 4,5
Pressure (hPa)
Phases 2,3
Phases 6,7
200
600
1000
50 E
100 E
DYNAMO
150 E
200 E
Mixing ratio
anomaly
Descent of easterlies