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A view of UT clouds and relative humidity using AIRS, CALIPSO, and CloudSat by Brian H. Kahn

A view of UT clouds and relative humidity using AIRS, CALIPSO, and CloudSat by Brian H. Kahn Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA presented at: HIRDLS Science Team Meeting Wednesday January 30th, 2880 NCAR, Boulder, CO.

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A view of UT clouds and relative humidity using AIRS, CALIPSO, and CloudSat by Brian H. Kahn

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  1. A view of UT clouds and relative humidity using AIRS, CALIPSO, and CloudSat by Brian H. Kahn Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA presented at: HIRDLS Science Team Meeting Wednesday January 30th, 2880 NCAR, Boulder, CO

  2. Thin cirrus retrievals in the tropics via AIRS • Retrieval based on Yue et al. (2007), J. Atmos. Sci. • Results presented in Kahn et al. (2007), Atmos. Chem. Phys. Discuss.

  3. Thin cirrus + RHI retrievals via AIRS • RHI calculation following Gettelman et al. (2006), J. Climate • Results presented in Kahn et al. (2007), Atmos. Chem. Phys. Discuss.

  4. Motivation – Inter-hemispheric differences in UT RHI • What are the causes and implications? • Cirrus nucleation + aerosol differences, dynamic variability reflected in T(z), variability in q(z)? Others? Gettelman et al. (2006), J. Climate

  5. An illustration of AIRS RHI + CloudSat/CALIPSO cloud profiles CloudSat/CALIPSO ground track Cirrus observed by CloudSat/ CALIPSO • Products used: • RHI (AIRS) • Cloud profiles (CSat + CAL) • IWC (CSat) • Cloud type (CSat)

  6. AIRS RHI: Vertical structure, higher RHI @ cloud top RHI limited to: (1) q > 15 ppmv (2) T ≤ 243 K (3) Quality Flag = “Best” or “Good”

  7. AIRS RHI most useful in broken/thin Cirrus & clear sky Purple: Cirrus Blue: Altostratus Red: Cumulus Dark Red: Nimbostratus

  8. AIRS RHI & CloudSat IWC anti-correlated • Variability from scene-to-scene • Information about cirrus formation/evolution?

  9. RHI & IWC anti-correlated for 5 days of data • Anti-correlation of IWC and RHI consistent with some in situ aircraft spirals (e.g. MIDCIX campaign) • 25–50% of Cirrus with IWC ≤ 1–10 mg m3 is supersaturated

  10. RHI dependent on cloud/clear sky & season • All distributions are global (July 2006 and January 2007) • Note January ‘07 has smaller dynamic range in RHI • CALIPSO RHI closer to clear sky: thin Cirrus produces low RHI bias • Kahn et al. (2007), Atmos Chem. Phys. Discuss.

  11. Hemispheric & seasonal variance in RHI SH Cloudy Sky RHI NH Cloudy Sky RHI • RHI less variable in SH • Similar differences for CALIPSO-centric view of clouds & clear sky • What controls the variability?

  12. Hemispheric & seasonal variance in T and RHI NH Cloudy Sky RHI NH 1 Temperature variability • Width of PDFs between T and RHI correspond: dynamical control of RHI PDF? • Similar view using CALIPSO-observed clouds & clear sky • BUT: nice correspondence not true in SH (not shown)

  13. Take Home Messages & (Near) Future Work • Combined A-train observations reveal global-scale, long-term insights • AIRS cirrus + RHI PDFs reveal physical relationships consistent with other • measurements • Hemispheric/seasonal differences modulate RHI distributions within cloud • and clear sky • T variability appears to have asymmetric hemispheric correspondence with • RHI PDFs •  Important to constrain dynamical influences to detect other controlling • factors in RHI • Continued investigation into linkage between T and q variability, and • seasonal/hemispheric characteristics of RHI PDFs • Acknowledgments: AIRS, CloudSat, CALIPSO science, algorithm and processing teams, NASA post-doctoral program (NPP), and NASA radiation sciences program for funding support

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