Using MODIS and AIRS for cloud property characterization Jun W. Paul Menzel #, Steve Chian-Yi and Institute for Meteorological Satellite Studies (CIMSS) Space Science and Engineering Center University of Wisconsin-Madison #Center for Satellite Applications and Research (STAR) NOAA/NESDIS MODIS Science Team Meeting 4 – 6 January 2006 Radisson Plaza Lord Baltimore Hotel, Baltimore

New and Improved products are found combinations of MODIS and AIRS data MODIS AIRS Sounding capability Spectral resolution Spatial resolution Cloud masking

Why MODIS/AIRS synergy ? AIRS provides sounding capability but is influenced by clouds during to large footprint size (13.5 km at nadir), MODIS clear radiances can help AIRS cloud-clearing (removal of clouds) MODIS provides less cloud microphysical information during night, AIRS provides cloud microphysical properties for semi-transparency clouds but needs MODIS masks (cloud mask and cloud phase mask) for sub-pixel cloud characterization.

How MODIS/AIRS synergy ? Use MODIS masks (cloud mask, cloud phase mask, and cloud classification mask) for AIRS sub-pixel cloud characterization (Li et al. 2004) Use combined MODIS and AIRS for cloud property (cloud-top pressure, optical thickness, particle radius) retrieval during night Use MODIS for AIRS cloud-clearing in partial cloud cover –Use MODIS clear radiances within AIRS sub-pixel plus AIRS cloudy radiances to construct AIRS clear column radiance spectrum – Use MODIS clear radiances for QC on MODIS/AIRS cloud- cleared radiances and AIRS sounding retrieval

AIRS sub-pixel cloud detection and characterization using MODIS (Li et al. 2004a). –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 ! ClearCloudy 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 F3 F2 F1 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.

1DVAR during daytime: MODIS cloud products are used as background Fast Cloudy Radiative Transfer Model Observed AIRS Radiance Measurements CTP: Cloud-Top Pressure ECA: Effective Cloud Amount CPS: Cloud Particle Size COT: Cloud Optical Thickness at 0.55µm Background Information from MODIS COT and CPS: 790 – 1130 cm**-1 CTP and ECA: 670 – 790 cm**-1 Minimum Residual (MR) during nighttime

AIRS cm -1 1km MODIS classification mask F1: CTP=251, COT=0.34 F2: CTP=248, COT=1.18 Wavenumber (cm**-1) F1 F2

AIRS cm -1 1km MODIS classification mask superimposed to AIRS footprints F3: Thick ice clouds

p c =258 mb, effective cloud amount =0.70 D e =33.9 µm,  c =1.62 Microphysical information

AIRS window BT image

AIRS cloud-top pressure retrieval (MODIS is used for AIRS cloud detection)

AIRS cloud optical thickness retrieval (MODIS is used for AIRS cloud phase detection)

AIRS CTH (m) Barrow Box A MPACE: Mixed Phase Artic Cloud Experiment Granule 223, 17 October 2004 MODIS are used for AIRS cloud detection and cloud phase detection ! BT (K)

CTP comparison with Lidar AIRS time is 22:17:32 AIRS CTH=7.6 km RAOB: T and Td

Vertical Layers AIRS Effective Radius=38.6 um AIRS time = 22:17:32 UTC AIRS OD=1.44

Using MODIS for AIRS cloud- clearing MODIS and AIRS see the same IR spectral regions Using MODIS for AIRS cloud-clearing is relevant to GOES-R ABI/HES retrieval (no microwave data available on GOES-R) MODIS can be used for QC on AIRS cloud- cleared radiances and sounding retrieval

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 (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 clr + CC BT ( convolved to MODIS 6.7 um band) AIRS granule 184 of Sept 24, 2004

AIRS BT (All) AIRS BT (Clear Only) AIRS BT (Cloud-Cleared)

Summary MODIS high spatial resolution masks (cloud mask, cloud phase mask and classification mask) are perfect for AIRS sub-pixel cloud characterization MODIS/AIRS combination provides good cloud properties (cloud-top pressure, optical thickness, particle radius) during night time MODIS can be used for AIRS cloud-clearing on single footprint basis