The Convective Cloud Population during the Buildup of the Madden-JulianOscillation

AGU Fall Meeting, San Francisco, 7 December 2011

R. Houze, S. Brodzik, J. YuanUniversity of Washington

The Convective Cloud Population during the Buildup of the Madden-JulianOscillation

Three perspectives:

A-Train

DYNAMO

TRMMStill going on!

The MJO

Wheeler and Hendon 2004

Phases of the MJO

TRMM

Phase 1 Phase 5

Phase 7Phase 3

Frequency of radar echo in “broad stratiform regions” of MCSs

Phase 7Phase 3

Phase 1 Phase 5

Frequency of radar echo in “deep convective cores”

Phase 7Phase 3

Phase 1 Phase 5

Frequency of “shallow isolated” radar echoes (anomaly)

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

CMCSs SM

CSs HCSs excl.M

CSs non-HCSs

Perc

enta

ge %

a) Cloud coverage b) Contribution to precipitation

“Connected MCSs”

“Separated MCSs”

Other High CloudSystems

Non-high-cloudSystems

DYNAMO

Cloud Structures(NCAR S-PolKa radar)

Suppressed phase:

Lines of non-precipitating

clouds

Suppressed phase:

Clouds at cold pool boundaries

Suppressed phase:

Clouds at cold pool boundaries

4 km

8 km

graupel

small icelarge non-melting ice

heavy rain

Small cumulonimbus

melting snow

Small, weakstratiform area

Active phase:

Large mesoscale

system Stratiform

Convective

5 km

10 km

Robust melting layer

inLarge MCS

Convection feeding into a large MCS

Shear

Low-level westerly component, upper-level easterly component

NE

NE

SW

SW

Biggest MCS of first active phase: weak unidirectional shear

Larger-than-mesoscale Organization

Giant Rings of Convection

Westerly Surges

EndThis research is supported by NSF grant ATM AGS-1059611, DOE grant DE-SC0001164/ER-64752, and

NASA grants NNX10AM28G and NNX10AH70G

Extras

Identify each Identify each contiguouscontiguous 3D echo object 3D echo objectseen by TRMM PR seen by TRMM PR

Convective componentConvective component Stratiform componentStratiform component

Extreme characteristicExtreme characteristicContiguous 3D volume ofContiguous 3D volume ofconvective echo > 30 dBZ convective echo > 30 dBZ

Top height > 8 kmTop height > 8 km

““Deep convective coreDeep convective core”” Horizontal area > 800 kmHorizontal area > 800 km22

““Wide convective coreWide convective core””

Extreme characteristicExtreme characteristicContiguous stratiform echoContiguous stratiform echo

with horizontal area > 50 000 kmwith horizontal area > 50 000 km22

““Broad stratiform regionBroad stratiform region””

Categories of radar echoes seen by TRMM Categories of radar echoes seen by TRMM

MODIS TB11 + AMSR-E (Yuan and Houze 2010)

combined to find“cold centers” & “raining areas”

Use 260 K threshold

Locate 1st closed contour

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 6 7 8Phase

Pres

sure

(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

Descent of easterlies