Convective Clouds Lecture Sequence 1. 2. 3. 4. 5. 6. 7. 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? Before Satellites Visual Observation Cumulonimbus Cumulus congestus Small cumulus Radiosonde data in the tropics “Hot tower hypothesis” Riehl & Malkus 1958 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 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 = 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 How do the environments of these regimes differ? 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 Stratocumulus Regime Trade Wind Regime Indo/Pacific Warm Pool “Trimodal” distribution Johnson et al. 1999 Evidence from TOGA COARE sounding data 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)