The Tropical Cloud Population
R. A. Houze
Lecture, Indian Institute of Tropical Meteorology, Pune, 9 August 2010
Clouds in Low Latitudes
Lecture Sequence
1.
2.
3.
4.
5.
6.
7.
Basic tropical cloud types
Severe convection & mesoscale systems
Tropical cloud population
Convective feedbacks to large-scales
Monsoon convection
Diurnal variability
Clouds in tropical cyclones
Before Satellites
Visual Observation
Cumulonimbus and
mesoscale
convective systems
Cumulus congestus
Small cumulus
View from an aircraft flying over the South China Sea
Radiosonde Data
“Hot tower
hypothesis”
of
Riehl &
Malkus 1958
Satellite Observations
Large cloud shields
Large cloud shields
Circa 1970
Satellite view of the
tropical cloud population
Good:
•Explained satellite pictures
•Retained the hot tower notion
•Included smaller clouds
Not good:
•Missing downdraft
•No stratiform rain
•Unrealistic scale separation
Radars
GATE 1974
GATE SHIP
ARRAY
More Field Projects to Study Convection
BoB 1979
TEPPS
1997
EPIC
2001
(Dashed: No sounding network)
JASMINE
1999
Post-GATE view of the tropical cloud population
MESOSCALE CONVECTIVE SYSTEMS (MCSs)
STRATIFORM
RAIN
Houze et al. (1980)
By the early 1980’s
Idealized life cycle of tropical MCS
Houze 1982
Precipitation Radar in Space
The TRMM Satellite
TRM
M
Radar
Low altitude, low inclination orbit
TRMM Satellite Instrumentation
 = 2 cm
Important! PR
measures 3D
structure of radar
echoes
Kummerow et al, 1998
Knowledge of global rainfall before satellites measured
rain from space
Knowledge of global rainfall after TRMM & other
satellites measured rain from space
Combined satellite rainfall July 2000
TRMM plus passive microwave sensors + other
How is tropical rain distributed by
cloud size and type?
2 Years of
TRMM PR data
Large Cbs
MCSs
Small
isolated Cbs
Schumacher &
Houze 2003
How do the environments of these
regimes differ?
Trade Wind Regime
Stratocumulus Regime
Trade Wind Regime
Indo/Pacific Warm Pool
Traditional conceptual view of mean meridional distribution of
tropical convection
Simpson 1992
“Trimodal”
distribution
Johnson et al.
1999
Conceptual
model based on
TOGA COARE
observations
Cu congestus
Small Cb
“Trimodal”
distribution
Johnson et al.
1999
Evidence from
TOGA COARE
sounding
data
MANUS
X
“Trimodal”
distribution
Hollars et al.
1999
Evidence
from Manus ARM
cloud radar
observations
Tropical cloud population related to SST
TRMM PR Deep Convective
SST Climatology (July)
July SST
TRMM PR Shallow, Isolated Convective
Land vs Ocean
TRMM view of Africa vis a vis the Atlantic
Rain
MCSs with large 85
GHz ice scattering
Stratiform Rain Fraction
Lightning
Cloud Radar in Space
Anvils of Mesoscale Convective Systems (MCSs)
Yuan and Houze 2010
Three steps of analysis of multi-sensor data
1
&
(TB11)
(GEOPROF-2B)
2
3
(TB11)
(GEOPROF-2B)
Yuan and Houze 2010
MODIS
MODIS
Use MODIS and CloudSat to find threshold of thick
high cloud
CloudSat
Yuan and Houze 2010
1-Find“cold centers”
2-Use AMSR-E to find rain areas
Locate 1st
closed
contour
Use 260 K
threshold
Associate
pixels with
nearest
cold center
Use 1 mm/h
threshold for
rain rate
Yuan and Houze 2010
Define criterion for MCS that is reasonable for all
these regions
Yuan and Houze 2010
Temperature defining cold center
Colors show rain amount
TB11 = 220
Area > 2000 km2
account for most
of the rainfall
Size of cold cloud top
Yuan and Houze 2010
“Connected” and “Separated” MCSs
Yuan and Houze 2010
MCSs Over the Whole Tropics
Yuan and Houze 2010
MCSs Over the Whole Tropics
Yuan and Houze 2010
Frequency of MCS anvils over tropics
Yuan and Houze 2010
Comparison of MCS anvils in different parts
of the tropics
CloudSat data
Yuan and Houze 2010
Milestones in determining the tropical cloud
population
Pre-satellite era
Hot towers and smaller clouds
Radars in field projects
MCSs, squall lines, stratiform precipitation
Precipitation radar in space
Patterns of convective, stratiform, shallow isolated
Relation to ocean & land
Cloud radar in space
Global distributions of MCSs & anvils
Clouds in Low Latitudes
Lecture Sequence
1.
2.
3.
4.
5.
6.
7.
Basic tropical cloud types
Severe convection & mesoscale systems
Next
Tropical cloud population
Convective feedbacks to large-scales
Monsoon convection
Diurnal variability
Clouds in tropical cyclones
This research was supported by
NASA grants NNX07AD59G, NNX07AQ89G, NNX09AM73G, NNX10AH70G, NNX10AM28G,
NSF grants, ATM-0743180, ATM-0820586,
DOE grant DE-SC0001164 / ER-6