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

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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

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Retrieval Uncertainty Estimates

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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

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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