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Convective Clouds

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

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  1. 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

  2. The tropical convective cloud population Robert Houze University of Washington Lecture, Summer School on Severe and Convective Weather, Nanjing, 11 July 2011

  3. The tropical convective cloud population What do we know? How has technology contributed? What comes next?

  4. Before Satellites

  5. Visual Observation Cumulonimbus Cumulus congestus Small cumulus

  6. Radiosonde data in the tropics “Hot tower hypothesis” Riehl & Malkus 1958

  7. Convective parameterization GCM grid

  8. Satellite Observations: an “inconvenient truth”

  9. Large cloud shields

  10. Early 1970’s Satellite view of the tropical cloud population • Explained satellite pictures • Retained the hot tower notion • Included smaller clouds

  11. Radars: The second “inconvenient truth”

  12. GATE 1974

  13. 1974 40 ships! 12 aircraft! 4 shipborne scanning digital C-band radars

  14. More Field Projects to Study Convection BoB 1979 JASMINE1999 EPIC 2001 TEPPS1997 (Dashed: No sounding network) Ground, ship, & airborne cm radars

  15. Post-GATE view of the tropical cloud population MESOSCALE CONVECTIVE SYSTEMS (MCSs) Hot Tower STRATIFORMRAIN GCM grid Houze et al. (1980)

  16. Heating and cooling processes in an MCS Houze 1982

  17. Simplified MCS Heating Profiles Stratiform Height (km) Convective Schumacher et al. 2004 Deg K/day

  18. MCS Net Heating Profiles 70% stratiform 40% stratiform Height (km) 0% stratiform Deg K/day Schumacher et al. 2004

  19. Precipitation Radar in Space

  20. The TRMM Satellite Ku-band Radar Low altitude, low inclination orbit

  21. Knowledge of global rainfall before satellites measured rain from space

  22. Rainfall mapping revolutionized! Combined satellite rainfall July 2000 TRMM plus passive microwave sensors + other

  23. TRMM Satellite Instrumentation λ= 2 cm Important! PR measures 3D structure of radar echoes Kummerow et al, 1998

  24. How tropical rain is distributed by cloud sizeand type

  25. 2 Years of TRMM PR data Large CbsMCSs Smallisolated Cbs Schumacher & Houze 2003

  26. How do the environments of these regimes differ?

  27. TRMM PR Deep Convective SST Climatology (July) July SST TRMM PR Shallow, Isolated Convective

  28. Traditional conceptual view of mean meridional distribution of tropical convection Simpson 1992

  29. Stratocumulus Regime

  30. Trade Wind Regime

  31. Indo/Pacific Warm Pool

  32. “Trimodal” distributionJohnson et al. 1999Evidence from TOGA COARE soundingdata

  33. Suggested by TOGA COARE radiosonde data Johnson et al. 1999 “Trimodal distribution” Cu congestus Small Cb

  34. Cloud Radars

  35. MANUS X “Trimodal” Distribution Frequency of cloud-top heightfrom 9 mm wavelength vertically pointing radar Hollars et al. 1999

  36. Cloud Radar in Space

  37. The A-Train Satellites show the complete MCS Yuan and Houze 2010

  38. MCSs Over the Whole Tropics (< 12000 km2) (> 40000 km2) Yuan and Houze 2010

  39. Morphology of MCS anvils in different parts of the tropics Data from CloudSat mm-Wavelength Cloud Profiling Radar Yuan and Houze 2010

  40. Internal structure of MCS anvils shown by CloudSat Cloud Profiling Radar Africa Indian Ocean Yuan, Houze, and Heymsfield 2011

  41. Conceptual model of anvil microphysics graupel snow convective rain stratiform rain Cetrone and Houze 2011

  42. Five radars on a tiny island Addu Atoll

  43. 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

  44. Summary & Conclusions

  45. 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

  46. 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

  47. 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

  48. 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

  49. Extra Slides

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