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Clouds and Radiation

Clouds and Radiation. Clouds and Radiation. Clouds and Radiation. “..there are substantial uncertainties in decadal trends in all data sets and at present there is no clear consensus on changes in total cloudiness over decadal time scales.” IPCC-The Scientific Basis-Chapter 3, p. 277.

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Clouds and Radiation

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  1. Clouds and Radiation

  2. Clouds and Radiation

  3. Clouds and Radiation “..there are substantial uncertainties in decadal trends in all data sets and at present there is no clear consensus on changes in total cloudiness over decadal time scales.” IPCC-The Scientific Basis-Chapter 3, p. 277 An increase in both clouds and precipitation has occurred over many parts of the land surface (Dai et al., 1999, 2004a, 2006), although not in the tropics and subtropics (which dominate the global land mean; Section 3.3.2.2). IPCC-The Scientific Basis-Chapter 3, p. 279

  4. IPCC WG1 AR4 Report Variability caused by model representations of clouds

  5. How do Clouds Alter the State of the Atmospheric Column? Diabatic Heating Profiles • Latent Heating • Net column latent heating = Precipitation mass * L, where L = latent heat • Radiative Heating • Net column radiative heating= net incoming minus net outgoing • Profiles of diabatic heating impact atmospheric dynamic and thermodynamic structure

  6. Radiative Heating and Cooling of the atmospheric column

  7. a cloud-free column SHORTWAVE λ=1-4 μm includes visible band S S ) S ) S

  8. LONGWAVE λ > 4 μm /Cooling

  9. Radiative Flux Divergence Primer • Radiative Flux Divergence = • net radiation into column - net radiation out of column • positive values imply heating • negative values imply cooling neg pos NET

  10. SHORTWAVE

  11. SHORTWAVE • cirrus (ice clouds) • thin • wispy • semi-transparent • optically thin

  12. SHORTWAVE • cumulus convection • and other optically thick • clouds • (liquid/mixed/ice) • base near surface • > 30% coverage • vertical development • layer clouds

  13. Cirrus and Cumulus from the Space Shuttle Courtesy NASA CERES

  14. LONGWAVE

  15. LONGWAVE • cumulus convection • and other optically thick • clouds • (liquid/mixed/ice)

  16. LONGWAVE • cirrus (ice clouds) • cold cloud tops

  17. What Cloud Properties Change the Radiative Heating Rate Profile? • Hemispheric cloud coverage cloud • Optical thickness of individual clouds and layers • Height in the atmosphere • Layer coherence (or overlap) • Composition • Contain ice crystals, liquid water, or both? • Particle sizes? • Particle concentrations?

  18. How Does the Location of Cloud Impact the Surface Temperature? High Clouds ~10-km Low Clouds ~2-km COOLING WARMING

  19. What types of remote sensors do we use to make cloud measurements? • Vertically-Pointing Lasers (LIDARs) • measure the height of the lowest cloud base • below cloud concentrations of aerosol and water vapor • beam quickly disperses inside cloud • Cloud Radars • cloud location and microphysical composition • in-cloud updrafts, downdrafts, and turbulence • Microwave Radiometers • measure the total amount of liquid water in atmosphere • can’t determine location of liquid • no measure of ice water content

  20. LidarData from Southern Great Plains 20-km No Signal 10-km Low Clouds Ice Clouds Surface time 7:00 pm 7:00 am 24 Hours 7:00 pm Negligible Return Cloud and Aerosol Particles Cloud droplets

  21. Niamey, Niger, Africa • 20 Cloud Droplets • 15 Cloud and/or Aerosol Height (km) • 10 • LIQUID CLOUDS • 5 • Biomass Burning • Dust Negligible Return • 0 • 1200 • 0000 • 0000 Time (UTC)

  22. 3.2 mm cloud radars 8 mm UHF 10 cm VHF

  23. Cloud Radar Wavelengths 8.0 mm 35 GHz 3.2 mm 95 GHz Maximum Propagation Distance 20-30 km 10-15 km

  24. The DOE ARM Cloud Radars

  25. Cloud Radar Data from Southern Great Plains 20-km Black Dots: Laser Measurements Of Cloud Base Height 10-km Surface time 7:00 pm 7:00 am 7:00 pm Small Cloud Particles Typical Cloud Particles Very Light Precipitation

  26. Evolution of Cloud Radar Science • Cloud Structure and Processes • Cloud Statistics • Cloud Composition diurnal variation in cloud fractional coverage and surface precipitation for June 2006 over Lamont, Oklahoma (Courtesy: Lynne DiPretore)

  27. GFS cloud initialization data • mandatory radiosonde data • satellite retrievals of temperature • satellite-derived cloud motion vector • aircraft • cloud fraction parameterization: Xu and Randall (1996) • August • GFS 10-15 km cloud fraction larger than AMF • AMF 0-10 km cloud fraction larger than GFS Height (km) Cloud Fraction (%) Kollias, P, M.A. Miller, K.Johnson, M. Jensen, D. Troyan, 2008

  28. Multiple remote sensors required to measure non- and weakly precipitating clouds Top Radar Echo Low Radar Sensitivity 10-km Base Radar Echo Top Base 2-km Emission Radar Echo Surface Microwave Radiometer Laser Radar

  29. Liquid Cloud Particle Median Radius 6 4 Height (km) 2 0 time 7:00 pm 7:00 am 7:00 pm 25 17 1 4 10 Micrometers Miller and Johnson, 2003

  30. Tobin et al., 2007

  31. Clouds and Radiation from Space (and high altitude)

  32. June 12, 2006 Oklahoma CPL backscatter profiles and MAS comparison Matt McGill/NASA Goddard +37 km 0 -37 6 4 altitude (km) 2 0 19:53 time (UTC) 19:30 275 distance (km) 0

  33. A-TRAIN CONSTELLATION The Afternoon or "A-Train" satellite constellation presently consists of 5 satellites Two additional satellites, OCO and Glory, were supposed to join the constellation OCO was lost during a launch failure on 2/24/2009. Glory is scheduled to launch (02/23/11) Approx equator crossing times

  34. Aqua CALIPSO Aura Glory OCO-2? CloudSat PARASOL OMI - Cloud heights OMI & HIRLDS – Aerosols MLS& TES - H2O & temp profiles MLS & HIRDLS – Cirrus clouds CALIPSO- Aerosol and cloud heights Cloudsat - cloud droplets PARASOL - aerosol and cloud polarization Glory-aerosol size and chemistry MODIS/ CERES IR Properties of Clouds AIRS Temperature and H2O Sounding (Source: M. Schoeberl) Afternoon Constellation Coincidental Observations

  35. CloudSat (Hurricane Ike)

  36. CloudSat

  37. Radar/Lidar Combined Product Development • Formation flying is a key design element in cloudsat • CloudSat has demonstrated formation flying as a practical observing strategy for EO. • Overlap of the CloudSat footprint and the CALIPSO footprint, within 15 seconds, is achieved >90% of the time.

  38. A-Train Cloud Ice Microwave Limb Sounder ECMWF CloudSat

  39. Visual Images of the Sky • cloud coverage (versus cloud fraction) • simple! digitize images and … • daytime only • integrated quantity

  40. Lidar/Radar combined ice microphysics - new A-Train ice cloud microphysics Zhien Wang University of Wyoming

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