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PHYS 622 - Clouds spring ‘04 S. Platnick (NASA GSFC/UMBC PHYS Adjunct Faculty)

PHYS 622 - Clouds spring ‘04 S. Platnick (NASA GSFC/UMBC PHYS Adjunct Faculty). Texts: Rogers, R.R., and M. K. Yau, A Short Course in Cloud Physics , Pergamon Press, 1989. Twomey, S., Atmospheric Aerosols , Elsevier Publishing, 1977. PHYS 622 - Clouds, spring ‘04, lect. 1, Platnick.

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PHYS 622 - Clouds spring ‘04 S. Platnick (NASA GSFC/UMBC PHYS Adjunct Faculty)

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  1. PHYS 622 - Cloudsspring ‘04S. Platnick (NASA GSFC/UMBC PHYS Adjunct Faculty) • Texts: • Rogers, R.R., and M. K. Yau, A Short Course in Cloud Physics, Pergamon Press, 1989. • Twomey, S., Atmospheric Aerosols, Elsevier Publishing, 1977. PHYS 622 - Clouds, spring ‘04, lect. 1, Platnick

  2. Clouds - The “Wet” Aerosol • “Wet” aerosol: much of the mathematics (e.g., size distribution, etc.) used for characterizing aerosol microphysics applies to clouds. • A cloud definition: visible suspension of water and/or ice particles in the atmosphere. • Key word is visible, but not quantitative. Example, “sub-visual cirrus” (observed through non-visible, non-passive sensors/imagers or lidars). • Cloud physics: branch of physical meteorology, study of cloud formation (macrophysical & microphysical), lifecycles, precipitation, radiation, etc. • Macrophysical: larger scale spatial information, total/column water amounts, etc. • Microphysical: thermodynamic phase, size distribution, ice particle shape (habit), water content, etc. PHYS 622 - Clouds, spring ‘04, lect. 1, Platnick

  3. Why Clouds? • Weather • Dynamics: Latent heat and/or radiative effects impacting atmospheric stability/instability, atmospheric heating/cooling • Radiation (e.g., surface heating) • Chemical processes • Climate • General circulation • Hydrological cycle • Radiation budget • Clouds are a critical component of climate models (for reasons cited above) and therefore also to climate change studies • Not well-represented in climate models • Climate change: cloud-climate feedback, cloud-aerosol interactions (to be discussed), etc. PHYS 622 - Clouds, spring ‘04, lect. 1, Platnick

  4. Earth’s Hydrological Cycle - Schematic • Evaporation, transpiration (plants) • Atmospheric transport (vapor) • Condensation (liquid water, ice) • Precipitation • Surface transport (continental rivers, aquifers and ocean currents) PHYS 622 - Clouds, spring ‘04, lect. 1, Platnick

  5. NASA TRMM (Tropical Rainfall Measurement Mission) Tropical cyclone Elita Precipitation Radar PHYS 622 - Clouds, spring ‘04, lect. 1, Platnick

  6. TRMM 16 Feb 2004 weekly global rainfall accumulation PHYS 622 - Clouds, spring ‘04, lect. 1, Platnick

  7. PHYS 622 - Clouds, spring ‘04, lect. 1, Platnick

  8. PHYS 622 - Clouds, spring ‘04, lect. 1, Platnick

  9. Earth’s Radiation Budget - Schematic PHYS 622 - Clouds, spring ‘04, lect. 1, Platnick

  10. CERES (Clouds & Earth Radiant Energy System experiment) Radiation Budget Measurements - NASA Terra(March 2000 - May 2001) Record setting heat wave in CA, NV PHYS 622 - Clouds, spring ‘04, lect. 1, Platnick Courtesy CERES Science Team, NASA LaRC

  11. Cloud-aerosol interactions ex.: ship tracks (27 Jan. 2003, N. Atlantic) MODIS (MODerate resolution Imaging Spectroradiometer) PHYS 622 - Clouds, spring ‘04, lect. 1, Platnick

  12. Convective development (mesoscale, local) Synoptic development Cold front - steep frontal slopes Warm front - shallow frontal slopes PHYS 622 - Clouds, spring ‘04, lect. 1, Platnick

  13. MODIS (MODerate resolution Imaging Spectroradiometer) true-color composite, NASA Terra, ~1030 LT PHYS 622 - Clouds, spring ‘04, lect. 1, Platnick

  14. Cloud Classifications (a nomenclature) high level mid-level PHYS 622 - Clouds, spring ‘04, lect. 1, Platnick

  15. Cloud Classifications, cont. low level (base) vertical extent (potentially) PHYS 622 - Clouds, spring ‘04, lect. 1, Platnick

  16. cirrus alto cumulus cirrostratus: thin cirrus, note 22° halo => hexagonal crystals, parhelia (sundogs) => oriented crystals PHYS 622 - Clouds, spring ‘04, lect. 1, Platnick

  17. cumulus (fair weather) mammatus (implies sinking air) cumulus congestus (from NASA WB-57, July 13 2002) PHYS 622 - Clouds, spring ‘04, lect. 1, Platnick

  18. Kelvin-Helmholtz waves PHYS 622 - Clouds, spring ‘04, lect. 1, Platnick

  19. Cumulonimbus (from NASA ER-2, July 19 2002) PHYS 622 - Clouds, spring ‘04, lect. 1, Platnick

  20. Overview of Cloud Climatologies (statistics)- What do we know? How do we know it? • Quantities of interest • Cloud frequency (fraction), cloud-top height, cloud phase (ice vs. liquid water), optical properties (optical thickness), microphysics (particle size), column water amount (aka, “water path”), solar and IR radiative impact • Historic data sets • Ground observations • e.g.: Warren, S. G., et al. 1988: Global distribution of total cloud over and cloud type amounts over the ocean. NCAR/TN-317+STR [Available from the National Center for Atmospheric Research, Boulder, CO, 80307] • Satellite observations • ISCCP (International Satellite Cloud Climatology Project), solar reflective & IR techniques • amount, temperature, optical thickness, water path • HIRS (High Resolution Infrared Radiation Sounder - on NOAA polar orbiters), GOES VAS (VISSR [Vis-Ir Spin-Scan Sounder] Atmospheric Sounder) • amount, effective emissivity, and pressure heights with “CO2 slicing” technique PHYS 622 - Clouds, spring ‘04, lect. 1, Platnick

  21. Overview of Cloud Climatologies (statistics), cont. • SSM/I () - microwave passive remote sensing • liquid water path • ERBE (Earth Radiation Budget Experiment) - mid-80’s, instruments flown on the Earth Radiation Budget Satellite (ERBS), and NOAA -9, -10 • Recent/new data sets • Satellite observations • Solar IR imager: MODIS, flown on Terra, Aqua • Microwave: AMSR (Japanese ADEOS-II), AMSR-E (Aqua) • Radiation Budget: CERES (Clouds and the Earth’s Radiant Energy System) - next generation of radiation budget measurements, flown on TRMM, Terra, Aqua PHYS 622 - Clouds, spring ‘04, lect. 1, Platnick

  22. HIRS cloud frequency vs. month[Wylie et al., Journal of Climate, Vol. 7, No. 12, December, 1994]

  23. HIRS cloud frequency vs. altitude (September)

  24. HIRS cloud frequency vs. month for “thicker” clouds (opt thickness >6)

  25. ISCCP climatology exampleslow-level cloud amount (%)

  26. ISCCP climatology examplesmid-level cloud amount (%)

  27. ISCCP climatology exampleshigh-level cloud amount (%)

  28. AMSR-E cloud liquid water pathSept 2003(from F. Wentz, http://www.ssmi.com/) PHYS 622 - Clouds, spring ‘04, lect. 1, Platnick

  29. Cloud Microphysics PHYS 622 - Clouds, spring ‘04, lect. 1, Platnick

  30. Clouds Particle Scales PHYS 622 - Clouds, spring ‘04, lect. 1, Platnick

  31. Cloud Microphysical Quantities • Size distribution [n(r)] - droplet size pdf • Thermodynamic phase (liquid water, ice) • Number concentration [N] - e.g., cm-3; range: 10’s cm-3 - 100’s cm-3 for liquid water droplets, 10 liter-1 for ice particles • Water Content [LWC, IWC] - mass density, e.g., g-m-3 • Water Path [W] - vertical integration of water content, e.g., g-m-2 • Particle Size Moments • Mean • Effective radius [re] - radiatively relevant moment PHYS 622 - Clouds, spring ‘04, lect. 1, Platnick

  32. surface Cloud Microphysical Quantitiesschematic of vertically inhomogeneous cloud (horizontally homogeneous)

  33. MODIS monthly cloud fraction - Sept. 2003 Sc regimes Liquid water cloud fraction ITCZ (climatological feature) Ice cloud fraction PHYS 622 - Clouds, spring ‘04, lect. 1, Platnick

  34. MODIS monthly cloud particle size retrievals - Sept. 2003 Sc regimes Liquid water cloud particle effective radius (QA) Ice cloud particle effective radius PHYS 622 - Clouds, spring ‘04, lect. 1, Platnick

  35. Clouds are difficult, in part, by the natureof the relevant spatial scales and interdisciplinary fields PHYS 622 - Clouds, spring ‘04, lect. 1, Platnick

  36. Cold Cloud Processes Warm Cloud Processes PHYS 622 - Clouds, spring ‘04, lect. 1, Platnick

  37. PHYS 622 Clouds Emphasis on cloud microphysics: cloud particle nucleation, growth • Water Clouds • Formation concepts • Water path for adiabatic cloud parcel • Nucleation theory for water droplets • Ice Clouds • Precipitation mechanisms } Next 2,3 lectures PHYS 622 - Clouds, spring ‘04, lect. 1, Platnick

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