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New Products from combined MODIS/AIRS
Jun Li, Chian-Yi Liu, Allen Huang, Xuebao Wu, and Liam Gumley
Cooperative Institute for Meteorological Satellite StudiesSpace Science and Engineering Center
University of Wisconsin-Madison1225 West Dayton Street, Madison, Wisconsin
International EOS/NPP Direct Readout Meeting, 3 – 6 October 2005
Benevento, Italy
New products for IMAPP from combined MODIS/AIRS
• MODIS classification mask• AIRS sub-pixel cloud detection products using MODIS data
(Li et al. 2004a -JAM)• Single FOV Cloud/Aerosol property products from AIRS
radiances (Li et al. 2004b - JAM; 2005a - JAM) with the help of MODIS (cloud mask, cloud phase mask, cloud classification mask, etc.)
• AIRS cloud-clearing radiance products using multi-band MODIS clear radiances (Li et al. 2005b – IEEE TGARS)
• AIRS sub-pixel cloud detection and characterization using MODIS (Li et al. 2004a - JAM).
– Use MODIS cloud mask (1 km) for AIRS single field-of-view (SFOV) clear mask
– Use MODIS cloud phase mask (1 km) for AIRS SFOV cloud phase mask
– Use MODIS cloud classification mask (1 km) for AIRS SFOV cloud classification mask
Aqua MODIS RGB Natural Color; 17 September 2003: Hurricane Isabel
MODIS 1 km cloud mask
MODIS confident clear pixels are counted for AIRS clear coverage !
Clear Cloudy
AIRS clear coverage
Unknown
Mixed Phase
Ice Clouds
Water Clouds
Clear
MODIS cloud phase mask with 1 km spatial resolution
AIRS cloud phase mask with 13.5 km resolution (mixed phase clouds appear frequently !)
AIRS Window BT(K)
Water Land L. Cld Mid Cld L. Cld H. Cld H. Cld Mid Cld Mid. Cld
F3F2F1
MODIS 1km classification mask superimposed to the AIRS footprints of the study area. The MODIS classification mask gives the cloud layer information with each AIRS footprint.
• Cloud property products from AIRS radiances (Li et al. 2004b - JAM; 2005a - JAM) with help of MODIS – MODIS cloud mask is used for AIRS SFOV clear/cloudy
detection– MODIS cloud phase mask is used for AIRS SFOV phase
determination– Cloud properties are retrieved from from AIRS radiances
with a physical algorithm (Minimum Residual Method)
Fast Cloudy Radiative Transfer Model
Observed HES Radiance Measurements
),,,...,,,,( 10321 COTCPSECAECAECAECACTPX
CTP: Cloud-Top Pressure; ECA: Effective Cloud Amount at 10 wavenumbersCPS: Cloud Particle Size in diameter; COT: Cloud Optical Thickness at 0.55µm
)()( XRRXJ m
Minimum Residual (MR) algorithm for cloud property retrieval (Li et al. 2004b - JAM; 2005a - JAM)
Cost function
clear
cloudyCOT, CPS (window region): 790 – 1130 cm-1
CTP and ECA (CO2 region): 670 – 790 cm-1
COT=10.0
COT=5.0
COT=1.0
COT=0.05
CPS=10CPS=20CPS=30CPS=50
AIRS BT(K) @ 901.69 cm-1 1km MODIS classification mask superimposed to AIRS footprints
F1: Thick ice clouds
F1: CTP=258, CPS=33.90, COT=1.62
AIRS window BT image over North America region
AIRS cloud-top pressure retrieval with help of MODIS cloud mask
AIRS cloud optical thickness retrieval with help of MODIS cloud mask and cloud phase mask
Validation of cloud properties
• Compare with MODIS natural color image
• Compare with MODIS classification results
• Ground measurements
• Lidar observation
MODIS/AIRS
Spatial resolution:MODIS CTP: 5 kmAIRS CTP: 13.5 kmGOES CTP: 10 km
AIRS CTH (m)
Barrow
Box A
MPACE: Mixed Phase Artic Cloud ExperimentGranule 223, 17 October 2004
CTP comparison with LidarAIRS time is 22:17:32
MODIS CTH=5.5 km; AIRS CTH=7.6 km
Vertical Layers
AIRS Effective Radius=38.6 um
AIRS time = 22:17:32 UTC
AIRS OD=1.44
Desert Vs Dust aerosol
Dust
MODIS (BT11 - BT12)
Desert
AIRS window BT
MODIS Naturalcolor
Dust/aerosol
Desert Low surface emissivity @ 8.9 um over desert
Negative slope between 11 and 12 um
Synergy of MODIS/AIRS is expected to improved aerosol/dust products which are useful for regional applications
Derive AIRS cloud-cleared radiances using MODIS/AIRS cloud-clearing algorithm
• MODIS multi-spectral IR clear radiances within AIRS sub-pixel are used for AIRS cloud-clearing on SFOV basis (Li et al. 2005b, IEEE-TGARS)
• MODIS clear radiances within AIRS sub-pixel are used for Quality Control (QC) on AIRS cloud-clearing
Aqua MODIS IR SRF Overlay on AIRS Spectrum
Direct spectral relationship between IR MODIS and AIRS provides unique application of MODIS in AIRS cloud_clearing !
Optimal imager/sounder cloud-clearing Methodology
(Li et al. 2005; IEEE Trans. On Geoscience and Remote sensing, June issue).
N* is solved from 9 MODIS band (22, 24, 25, 28, 30, 31, 32, 33, 34) are used
*
*21
1 N
NRRR cc
iii
clrMi
i
iii
clrMi
i
RfRfRRf
RfRfRRf
N
i
i
)]()(][)([1
)]()(][)([1
2122
2112
*
85
4
3
2
1 6
7
1ccR
2ccR
3ccR
4ccR
5ccR
6ccR
7ccR
8ccR
(1) CCR is obtained on single footprint basis (3 by 3 box moves by single footprint
(2) MODIS clear radiances are used for QC
AIRS clear(13.5 km)
AIRS clear + CC-S(13.5 km)
MODIS clear(1 km)
AIRS single FOV profile retrieval versus ECMWF analysis
Cloud contaminated Cloud-cleared
Clear neighbor
Temperature
Water Vapor Mixing Ratio
Contaminated by thin clouds !!
Cloud-cleared (MODIS/AIRS)
Temperature RMS difference between AIRS and ECMWF~ 250 thin cloud FOVs
Clear Neighbor
1. There are potential new products from combined MODIS/AIRS, especially the SFOV cloud property products that include AIRS cloud mask, cloud phase mask, cloud layer information mask, etc.
2. AIRS SFOV cloud-cleared radiances will be derived using MODIS/AIRS cloud-clearing approach.
3. Efforts are also on deriving AIRS SFOV sounding products under both clear and cloudy skies with help of existing MODIS products.
Summary