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Convective Clouds. Lecture Sequence. Basic convective cloud types Severe convection & mesoscale systems Tropical cloud population Convective feedbacks to large-scales Extreme convection Diurnal variability Clouds in tropical cyclones. The tropical convective cloud population.
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Convective Clouds Lecture Sequence • Basic convective cloud types • Severe convection & mesoscale systems • Tropical cloud population • Convective feedbacks to large-scales • Extreme convection • Diurnal variability • Clouds in tropical cyclones
The tropical convective cloud population Robert Houze University of Washington Lecture, Summer School on Severe and Convective Weather, Nanjing, 11 July 2011
The tropical convective cloud population What do we know? How has technology contributed? What comes next?
Visual Observation Cumulonimbus Cumulus congestus Small cumulus
Radiosonde data in the tropics “Hot tower hypothesis” Riehl & Malkus 1958
Convective parameterization GCM grid
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”
1974 40 ships! 12 aircraft! 4 shipborne scanning digital C-band radars
More Field Projects to Study Convection BoB 1979 JASMINE1999 EPIC 2001 TEPPS1997 (Dashed: No sounding network) Ground, ship, & airborne cm radars
Post-GATE view of the tropical cloud population MESOSCALE CONVECTIVE SYSTEMS (MCSs) Hot Tower STRATIFORMRAIN GCM grid Houze et al. (1980)
Heating and cooling processes in an MCS Houze 1982
Simplified MCS Heating Profiles Stratiform Height (km) Convective Schumacher et al. 2004 Deg K/day
MCS Net Heating Profiles 70% stratiform 40% stratiform Height (km) 0% stratiform Deg K/day Schumacher et al. 2004
The TRMM Satellite Ku-band Radar Low altitude, low inclination orbit
Knowledge of global rainfall before satellites measured rain from space
Rainfall mapping revolutionized! Combined satellite rainfall July 2000 TRMM plus passive microwave sensors + other
TRMM Satellite Instrumentation λ= 2 cm Important! PR measures 3D structure of radar echoes Kummerow et al, 1998
2 Years of TRMM PR data Large CbsMCSs Smallisolated Cbs Schumacher & Houze 2003
TRMM PR Deep Convective SST Climatology (July) July SST TRMM PR Shallow, Isolated Convective
Traditional conceptual view of mean meridional distribution of tropical convection Simpson 1992
“Trimodal” distributionJohnson et al. 1999Evidence from TOGA COARE soundingdata
Suggested by TOGA COARE radiosonde data Johnson et al. 1999 “Trimodal distribution” Cu congestus Small Cb
MANUS X “Trimodal” Distribution Frequency of cloud-top heightfrom 9 mm wavelength vertically pointing radar Hollars et al. 1999
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 DOPPLER Air motions DUAL WAVELENGTH Water vapor CM-WAVELENGTH Precipitation MM-WAVELENGTH Non-precipitating Cumulus MM-WAVELENGTH Anvil cloud POLARIMETRY Microphysics
Timeline of progress Pre-satellite eraHot towers Radars in field projects MCSs, convective and stratiform precipitation regions Precipitation radar in space Global patterns—convective, stratiform, shallow Cloud radarsGround based—trimodality of the populationSatellite based—global distributions of MCSs, anvils, ... Dual wavelengthWater 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 larger-scale 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