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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, CO 2 slicing for high clouds, 11 µm for low clouds – Cloud optical & microphysical properties: optical thickness, effective particle size, r e, water path, thermodynamic phase. Primary r e 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) MOD06, MYD06 MOD35, MYD35 Summary of MODIS Operational Cloud Products AMS, Platnick, 10 July 06
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S. PlatnickS. Platnick11, M. D. King, M. D. King11, J. Riedi, J. Riedi22,,T. ArnoldT. Arnold1,31,3, B. Wind, B. Wind1,31,3, G. Wind, G. Wind1,31,3, P. Hubanks, P. Hubanks1,31,3
andand S. AckermanS. Ackerman44, R. Frey, R. Frey44, B. Baum, B. Baum44, P. Menzel, P. Menzel4,54,5, P. Yang, P. Yang66, R. Pincus, R. Pincus77
1 NASA Goddard Space Flight Center, Greenbelt MD,
2 Laboratoire d’Optique Atmosphérique, USTL, Lille, France,3 SSAI, Inc., Seabrook MD, 4 U. Wisconsin, Madison, WI, 5 NOAA/NESDIS,
6 Texas A&M, College Station, TX, 6 NOAA/CIRES, Boulder, CO
AMS 12th Conference on Atmospheric RadiationMadison, WI10 July 2006
The MODIS Operational Cloud Optical and Microphysical Products: Overview of the
Collection 5 Processing Algorithm
• 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
Outline
AMS, Platnick, 10 July 06
• Pixel level products (Level-2)
– Cloud mask. S. Ackerman, R. Frey, U. Wisconsin/CIMSS1km, 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/CIMSS5 km, CO2 slicing for high clouds, 11 µm for low clouds
– Cloud optical & microphysical properties: optical thickness, 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)
MOD0
6,MY
D06
MOD3
5,MY
D35
Summary of MODIS Operational Cloud Products
AMS, Platnick, 10 July 06
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
Some MOD06 Optical/Microphysical Collection 5 Changes
(http://modis-atmos.gsfc.nasa.gov/products_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
Example MODIS Data GranuleCanadian Fires, MODIS Terra, 7 July 2002
AMS, Platnick, 10 July 06
Example MODIS Data GranuleCanadian Fires, MODIS Terra, 7 July 2002
sea ice
smokeice cloud
true color SWIR composite
SWIR composite Cloud Mask overall conf. “Clear Sky Restoral”
cloudy
probably cloudy
spatial/spectral testsedge detection
250m cloud mask
probably clear
clear
AMS, Platnick, 10 July 06
SWIR composite Cloud Mask overall conf. Retrieval process. phase
cloudy
probably cloudy
liquid waterice
undetermined
probably clear
clear
AMS, Platnick, 10 July 06
Optical Thickness, Effective Radius Retrievals
optical thickness effective radius (µm)
100 100101101
ice water
40 2552010 30 10 15 20
ice water
AMS, Platnick, 10 July 06
Retrieval Uncertainty Estimates
AMS, Platnick, 10 July 06
opt. thickness:
effective radius:
500 25 500 25
250 250ice water
c/c (%) re/re (%)
Error sources: cal./fwd. model (5%), sfc. albedo(15%), atmo. correction (20% PWError sources: cal./fwd. model (5%), sfc. albedo(15%), atmo. correction (20% PWcc))
MODIS Aqua Collection 5, MODIS Aqua Collection 5, c/c (%)
liquid water cloudliquid water clouddaily aggregation, daily aggregation,
1 April 20051 April 2005((assumption: assumption:
correlation between correlation between pixels =1pixels =1))
liquid water cloudliquid water cloudmonthly aggregation, monthly aggregation,
April 2005April 2005 ( (assumption: daily assumption: daily
uncertainties uncertainties uncorrelateduncorrelated))
AMS, Platnick, 10 July 06
MODIS Aqua Collection 5, MODIS Aqua Collection 5, re/re (%)
liquid water cloudliquid water clouddaily aggregation, daily aggregation,
1 April 20051 April 2005
liquid water cloudliquid water cloudmonthly aggregation, monthly aggregation,
April 2005April 2005
AMS, Platnick, 10 July 06
Multilayer Flag• Multilayers of different phases: disagreement between IR-phase retrieval and phase Multilayers of different phases: disagreement between IR-phase retrieval and phase
derived for optical/microphysical retrieval (SWIR bands, cloud mask tests, …).derived for optical/microphysical retrieval (SWIR bands, cloud mask tests, …).• General multilayer: 0.94 µm water vapor absorption band.General multilayer: 0.94 µm water vapor absorption band.
AMS, Platnick, 10 July 06
liquid waterice
undetermined
ML, retr’d as waterML, retr’d as ice
ML undetermined
SWIR composite
Fraction of cloudy pixels (all phases) where the Multilayer Flag is set
MODIS Aqua Collection 5MODIS Aqua Collection 5Multilayer Cloud Flag, monthly L3, April 2005Multilayer Cloud Flag, monthly L3, April 2005
AMS, Platnick, 10 July 06
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).
Spectral Surface Albedo
Examples
• MODIS Atmosphere Team Collection 5 status:MODIS Atmosphere Team Collection 5 status:– Aqua reprocessing/forward processing began in early April 2006, Aqua reprocessing/forward processing began in early April 2006,
reprocessing nearly completereprocessing nearly complete– Terra reprocessing/forward processing will begin after completion of Terra reprocessing/forward processing will begin after completion of
Aqua; reprocessing expected to be completed in Dec. 2006Aqua; reprocessing expected to be completed in Dec. 2006• All Atmosphere Collection 5 products now being archived and distributed All Atmosphere Collection 5 products now being archived and distributed
via the MODIS production system: LAADS (disk storage archive w/ftp via the MODIS production system: LAADS (disk storage archive w/ftp access, search capability, subsetting, etc.). Distribution from Goddard access, search capability, subsetting, etc.). Distribution from Goddard DAAC will be discontinued.DAAC will be discontinued.
• MODIS operational cloud algorithms benefit from instrument’s spectral MODIS operational cloud algorithms benefit from instrument’s spectral coverage, spatial resolution, and radiometric/spectral characterization.coverage, spatial resolution, and radiometric/spectral characterization.
• Collection 5 enhancements include: clear sky restoral, new ice models, Collection 5 enhancements include: clear sky restoral, new ice models, L2 and L3 uncertainty estimates (for a subset of error sources), new L2 and L3 uncertainty estimates (for a subset of error sources), new surface albedo maps, multilayer flag research product. surface albedo maps, multilayer flag research product.
MODIS Atmosphere Team: http://modis-atmos.gsfc.nasa.gov Collection 5 distribution through LAADS: https://ladsweb.nascom.nasa.gov/
Summary
AMS, Platnick, 10 July 06