S' Platnick1, M' D' King1, J' Riedi2, - PowerPoint PPT Presentation

Title: S' Platnick1, M' D' King1, J' Riedi2,


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The MODIS Operational Cloud Optical and
Microphysical Products Overview of the
Collection 5 Processing Algorithm
S. Platnick1, M. D. King1, J. Riedi2, T.
Arnold1,3, B. Wind1,3, G. Wind1,3, P.
Hubanks1,3 and S. Ackerman4, R. Frey4, B. Baum4,
P. Menzel4,5, P. Yang6, R. Pincus7 1 NASA
Goddard Space Flight Center, Greenbelt MD, 2
Laboratoire dOptique Atmosphérique, USTL, Lille,
France, 3 SSAI, Inc., Seabrook MD, 4 U.
Wisconsin, Madison, WI, 5 NOAA/NESDIS, 6 Texas
AM, College Station, TX, 6 NOAA/CIRES, Boulder,
CO
AMS 12th Conference on Atmospheric
Radiation Madison, WI 10 July 2006
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Outline

• MODIS cloud product summary
• Cloud optical and microphysical retrieval issues
  and the new Collection 5 algorithm (collection
  refers to a processing stream)
• Collection 5 examples

AMS, Platnick, 10 July 06
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Summary of MODIS Operational Cloud Products

• Pixel level products (Level-2)
• Cloud mask. S. Ackerman, R. Frey, U.
  Wisconsin/CIMSS
• 1km, 48-bit mask/11 spectral tests, clear sky
  confidence in bits 1,2
• Cloud top properties pressure, temperature,
  effective emissivity. P. Menzel, R. Frey,
  NOAA-NESDIS U. Wisconsin/CIMSS
• 5 km, CO2 slicing for high clouds, 11 µm for low
  clouds
• Cloud optical microphysical properties optical
  thickness, t, effective particle size, re, water
  path, thermodynamic phase. Primary re from 2.1 µm
  band. M. D. King, S. Platnick, GSFC
• IR-derived thermodynamic phase. B. Baum, U.
  Wisconsin/SSEC
• Cirrus reflectance (via 1.38 µm band). B.-C. Gao,
  Naval Res. Lab
• Gridded time-averaged products (Level-3)
  statistics, histograms, contains all atmosphere
  products (clouds, aerosol, clear sky aggregations)

AMS, Platnick, 10 July 06
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Optical/Microphysical Retrieval Issues

• Critical issues (esp. for global processing)
• To retrieve or not to retrieve?
• Cloud thermodynamic phase liquid water or ice
  libraries?
• Ice cloud models.
• Multilayer/multiphase scenes detectable?
• Surface spectral albedo, including ancillary
  information regarding snow/ice extent.
• Atmospheric correction requires cloud top
  pressure, ancillary information regarding
  atmospheric moisture temperature profiles.
• Cloud-top temperature, ancillary surface
  temperature needed for 3.7 µm emission (band
  contains solar and emissive radiance).
• 3D cloud effects.

AMS, Platnick, 10 July 06
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Some MOD06 Optical/Microphysical Collection 5
Changes (http//modis-atmos.gsfc.nasa.gov/product
s_C005update.html)

• New Clear Sky Restoral algorithm implemented
  after cloud mask (to identify pixels incorrectly
  identified as cloud or partly-cloudy pixels).
• Updated cloud phase algorithm (still a difficult
  problem)!
• New ice cloud models (Baum et al. 2005).
• New research-level multilayer cloud flag. Level-3
  code separately aggregates single layer and
  multilayer cloud fraction, as well as single
  layer retrievals.
• New MODIS-derived global snow-free land surface
  spectral albedo maps snow/ice spectral albedo
  maps for Antarctica, Greenland hemispheric
  average ecosystem-based snow/ice albedo over land
  and for sea ice new IGBP ecosystem map.
  Available for download on Atmosphere team web
  site.
• New 1.6-2.1 µm retrievals over ocean and snow/ice
  surfaces.
• New pixel-level ?, re, WP retrieval uncertainties
  (baseline) and estimates of uncertainty of L3
  means.

AMS, Platnick, 10 July 06
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Example MODIS Data GranuleCanadian Fires, MODIS
Terra, 7 July 2002
AMS, Platnick, 10 July 06
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Example MODIS Data GranuleCanadian Fires, MODIS
Terra, 7 July 2002
true color
SWIR composite
sea ice
smoke
ice cloud
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SWIR composite
Cloud Mask overall conf.
Clear Sky Restoral
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SWIR composite
Cloud Mask overall conf.
Retrieval process. phase
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Optical Thickness, Effective Radius Retrievals
optical thickness
effective radius (µm)
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Retrieval Uncertainty Estimates

• Error sources cal./fwd. model (5), sfc.
  albedo(15), atmo. correction (20 PWc)

Dtc /tc ()
Dre /re ()
AMS, Platnick, 10 July 06
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MODIS Aqua Collection 5, Dtc /tc ()
liquid water clouddaily aggregation, 1 April
2005(assumption correlation between pixels 1)
liquid water cloudmonthly aggregation, April
2005 (assumption daily uncertainties
uncorrelated)
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MODIS Aqua Collection 5, Dre /re ()
liquid water clouddaily aggregation, 1 April 2005
liquid water cloudmonthly aggregation, April 2005
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Multilayer Flag

• Multilayers of different phases disagreement
  between IR-phase retrieval and phase derived for
  optical/microphysical retrieval (SWIR bands,
  cloud mask tests, ).
• General multilayer 0.94 µm water vapor
  absorption band.

SWIR composite
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MODIS Aqua Collection 5Multilayer Cloud Flag,
monthly L3, April 2005
Fraction of cloudy pixels (all phases) where the
Multilayer Flag is set
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Spectral Surface Albedo Examples
Spatially complete white-sky albedo in the
MODIS 0.86 µm band for four 16-day periods in
2002 (after Moody et al. 2005a).
Northern hemisphere multi-year average white-sky
spectral snow albedo as a function of selected
IGBP ecosystem classifications from 2000-2004
MOD43B3 data (after Moody et al. 2006b).
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Summary

• MODIS Atmosphere Team Collection 5 status
• Aqua reprocessing/forward processing began in
  early April 2006, reprocessing nearly complete
• Terra reprocessing/forward processing will begin
  after completion of Aqua reprocessing expected
  to be completed in Dec. 2006
• All Atmosphere Collection 5 products now being
  archived and distributed via the MODIS production
  system LAADS (disk storage archive w/ftp access,
  search capability, subsetting, etc.).
  Distribution from Goddard DAAC will be
  discontinued.
• MODIS operational cloud algorithms benefit from
  instruments spectral coverage, spatial
  resolution, and radiometric/spectral
  characterization.
• Collection 5 enhancements include clear sky
  restoral, new ice models, L2 and L3 uncertainty
  estimates (for a subset of error sources), new
  surface albedo maps, multilayer flag research
  product.

MODIS Atmosphere Team http//modis-atmos.gsfc.nas
a.gov Collection 5 distribution through LAADS
https//ladsweb.nascom.nasa.gov/
AMS, Platnick, 10 July 06