The tropical convective
cloud population
Robert Houze
University of Washington
Peking University Seminar, Beijing, 4 July 2011
The tropical convective
cloud population
What do we know?
How has technology contributed?
What comes next?
Before Satellites
Visual Observation
Cumulonimbus
Cumulus congestus
Small cumulus
Radiosonde data in the tropics
“Hot tower
hypothesis”
Riehl & Malkus
1958
Joanne
Simpson
Convective parameterization
Satellite Observations:
an “inconvenient truth”
Large cloud shields
Early 1970’s
Satellite view of the
tropical cloud population
•Explained satellite pictures
•Retained the hot tower notion
•Included smaller clouds
Radars:
The second “inconvenient
truth”
GATE 1974
1974
40 ships!
12 aircraft!
4 shipborne
scanning
digital
C-band radars
More Field Projects to Study Convection
BoB 1979
TEPPS
1997
EPIC
2001
JASMINE
1999
(Dashed: No sounding network)
Ground, ship, & airborne cm radars
Post-GATE view of the tropical cloud population
MESOSCALE CONVECTIVE SYSTEMS (MCSs)
Hot
Tower
GCM grid
STRATIFORM
RAIN
Houze et al. (1980)
Heating and cooling processes in an MCS
Houze 1982
Simplified MCS Heating Profiles
Height (km)
Stratiform
Convective
Schumacher et al. 2004
Deg K/day
MCS Net Heating Profiles
70% stratiform
Height (km)
40% stratiform
0% stratiform
Deg K/day
Schumacher et al. 2004
Precipitation Radar in Space
The TRMM Satellite
Ku-band Radar
Low altitude, low inclination orbit
Rainfall mapping revolutionized!
Combined satellite rainfall July 2000
TRMM plus passive microwave sensors + other
TRMM Satellite Instrumentation
 = 2 cm
Important! PR
measures 3D
structure of radar
echoes
Kummerow et al, 1998
How tropical rain is
distributed by cloud size
and type
2 Years of
TRMM PR data
Large Cbs
MCSs
Small
isolated Cbs
Schumacher &
Houze 2003
Traditional conceptual view of mean meridional distribution of
tropical convection
Simpson 1992
Suggested by
TOGA COARE
radiosonde data
Johnson et al.
1999
“Trimodal
distribution”
Cu congestus
Small Cb
Cloud Radars
MANUS
X
“Trimodal”
Distribution
Frequency of
cloud-top height
from 9 mm
wavelength
vertically pointing
radar
Hollars et al. 1999
Cloud Radar in Space
The A-Train Satellites show the complete MCS
Yuan and Houze 2010
MCSs Over the Whole Tropics
(< 12000 km2)
(> 40000 km2)
Yuan and Houze 2010
Morphology of MCS anvils in different parts
of the tropics
Data from CloudSat mm-Wavelength Cloud Profiling Radar
Yuan and Houze 2010
Internal structure of MCS anvils shown by
CloudSat Cloud Profiling Radar
Africa
Indian Ocean
Yuan, Houze, and Heymsfield 2011
Conceptual model of anvil microphysics
graupel
snow
convective rain
stratiform rain
Cetrone and Houze 2011
Five radars on a tiny island
Addu Atoll
Radar Supersite Approach
Will document many aspects of the convective population
HUMIDITY
DUAL WAVELENGTH
Water vapor
MM-WAVELENGTH
Non-precipitating
Cumulus
CM-WAVELENGTH
Precipitation
DOPPLER
Air motions
MM-WAVELENGTH
Anvil cloud
POLARIMETRY
Microphysics
Summary & Conclusions
Timeline of progress
Pre-satellite era
Hot towers
Radars in field projects
MCSs, convective and stratiform precipitation regions
Precipitation radar in space
Global patterns—convective, stratiform, shallow
Cloud radars
Ground based—trimodality of the population
Satellite based—global distributions of MCSs, anvils, ...
Dual wavelength
Water vapor
What we’ve learned
Spectrum of convective cloud types and sizes covers a
wide range of types and sizes of convective entities
• Mesoscale systems with stratiform rain
• Top-heavy heating profiles
• Multimodal size distributions
• Shallow isolated cells
• Structures of large anvil clouds
• Global variability of the population
Where we are going
How does convective population project onto largerscale dynamics?
• Latent heating profiles
• Radiative heating profiles in anvils of MCSs
• Nonprecipitating convective clouds
• Relation between humidity field and cloud
population evolution
• Role of clouds in MJO, ENSO, monsoon, &
coupled equatorial waves
End
This research was supported by
NASA grants NNX07AD59G, NNX07AQ89G, NNX09AM73G, NNX10AH70G, NNX10AM28G,
NSF grants, ATM-0743180, ATM-0820586,
DOE grant DE-SC0001164 / ER-6
Extra Slides
Internal structure of “thick” anvils shown by CloudSat
Africa
Indian Ocean
Yuan, Houze, and Heymsfield 2011
Data from MCSs seen
by ARM
W-band radar in
Niamey, Niger
Cetrone & Houze 2011
and also
Yuan et al. 2011-CloudSat
Height (km)
Internal
structures of
MCS anvils
Reflectivity (dBZ)
Data from MCSs seen
by ARM
W-band radar in
Niamey, Niger
Cetrone & Houze 2011
and also
Yuan et al. 2011-CloudSat
Height (km)
Internal
structures of
MCS anvils
Reflectivity (dBZ)