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Clouds, Aerosols and Precipitation

Clouds, Aerosols and Precipitation. GRP Meeting August 2011 Susan C van den Heever Department of Atmospheric Science Colorado State University Fort Collins, CO. GRP Team Members. Tom Ackerman Hiro Masunaga Jim Mather Sue van den Heever. Cloud-Aerosol-Precipitation Interactions (CAPI).

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Clouds, Aerosols and Precipitation

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  1. Clouds, Aerosols and Precipitation GRP Meeting August 2011 Susan C van den Heever Department of Atmospheric Science Colorado State University Fort Collins, CO

  2. GRP Team Members Tom Ackerman Hiro Masunaga Jim Mather Sue van den Heever

  3. Cloud-Aerosol-Precipitation Interactions (CAPI) Cloud-Aerosol-Precipitation Interactions More general term than Aerosol Indirect Effects (Twomey, 1977; Twomey et al., 1984; Albrecht, 1989) Allows for inclusion of a range of related responses such as cloud dynamic forcing

  4. GEWEX Objectives • CAPI • impacts on both the energy and water cycle processes through cloud and precipitation forcing • regarded as one of the most uncertain aspects of climate change through radiative effects • Enhancing our understanding of these processes • directly in keeping with basic GEWEX objectives • Improve model parameterization schemes with CRMs and GCMs

  5. Question 1 • Are aerosol responses different under different environments? What is the relative role of CAP interactions versus environment? • => modulated by different environmental characteristics • lower tropospheric static stability • lower tropospheric relative humidity • CAPE

  6. Question 1 Required Data • Aerosol concentrations • Surface precipitation • Base state variables

  7. Question 2 • Do precipitation responses to aerosol indirect forcing differ based on storm type? • Suppression in shallow clouds but enhanced precipitation in more convectively active clouds? • Isolated clouds versus organized cloud systems?

  8. Question 2 Required Data • Aerosol concentrations • Surface precipitation • Cloud top height

  9. Question 3 • How does the raindrop size distribution vary as a function of aerosol concentration? • Modeling studies suggest that under enhanced aerosol concentrations => greater number of smaller cloud droplets => reduced warm rain efficiency => more cloud water available in cloud => greater collection efficiencies once rain drops forms => larger raindrops • DSDs => impacts on precipitation estimation from remote sensors

  10. Question 3 Required Data • Aerosol concentrations • Drop size distributions

  11. Question 4 • Is there a dynamic response to aerosol indirect forcing? • Enhanced CCN concentrations => suppressed warm rain processes => more cloud water lofted => enhanced ice formation and latent heat release => enhanced buoyancy => deeper convection => enhanced precipitation • Impacts on drop size distributions => cold pool response => impacts on secondary convection => impacts on integrated rainfall

  12. Question 4 Required Data • Aerosol concentrations • Surface precipitation • Cloud top height • Ice water content • Surface temperature

  13. Proposed Data Set 1 • Combine the following: • TRMM 3 hour precipitation product • SPRINTARS aerosol information • Information on next slide • ECMWF Meteorological data • Reanalysis and realtime products available • Allows for assessment of Question 1, as well as basic aerosol indirect effects on precipitation

  14. An example of SPRINTARS output – total aerosol optical thickness on 4 July 2010 • SPRINTARS (Takemura et al., 2000) • Global product with varying vertical and horizontal resolution • Natural and anthropogenic sources (black carbon, organic matter, sulfate, soil dust, and sea salt) • Aerosol transport processes (emission, advection, diffusion, wet deposition, dry deposition, and gravitational settling)

  15. Proposed Data Set 2 • Combine the following: • CloudSat, TRMM and AMSR-E precipitation • MODIS, CALIPSO and SPRINTARS aerosol information • Allows for assessment of Questions 2 and 4 although sampling is limited

  16. Proposed Data Set 3 • Combine numerous aerosol and cloud properties from the DOE ARM (ASR) SGP site • Aerosol concentrations • Cloud base and top heights • Cloud type • Meteorological variables • Cloud ice and liquid water • Vertical velocity • Latent heat flux • Allow for assessment on Question 3 and Question 4 although only on a limited regional basis

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