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