A view of UT clouds and relative humidity using AIRS, CALIPSO, and CloudSat

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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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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.

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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.

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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
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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)

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AIRS RHI Vertical structure, higher RHI _at_ cloud
top
RHI limited to (1) q gt 15 ppmv (2) T 243
K (3) Quality Flag Best or Good
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AIRS RHI most useful in broken/thin Cirrus
clear sky
Purple Cirrus Blue Altostratus Red
Cumulus Dark Red Nimbostratus
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AIRS RHI CloudSat IWC anti-correlated

• Variability from scene-to-scene
• Information about cirrus formation/evolution?

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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)
• 2550 of Cirrus with IWC 110 mg m3 is
  supersaturated

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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.

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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?

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Hemispheric seasonal variance in T and RHI
NH 1? Temperature variability
NH Cloudy Sky RHI

• 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)

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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