5th GOES Users' Conference


Inter-calibration of geostationary imagers with MetOP/IASI hyperspectral measurements

Likun Wang, QSS Group Inc, Camp Spring, MD; and C. Cao

Inter-calibration of the radiance measurements from geostationary imagers is important to verify the proper functioning of sensors, monitor sensor performance over time, reveal differences between sensors, and quantify measurement uncertainties. Launched in October 2006, the Infrared Atmospheric Sounding Interferometer is one of the most advanced instruments on the MetOP satellite, which measures radiation emitted from the surface and atmosphere in the 645 2760 cm-1 (i.e., 3.6-15.5 μm) with high spectral resolution (i.e., 8461 spectral channels with a spectral sampling of 0.25 cm-1). Preliminary comparison of the measurements between IASI and the aircraft sensor (such as the Joint Airborne IASI Validation Experiment (JAIVEx)) indicates that IASI has operated well within specifications, maintaining superb spectral and radiometric calibration accuracy. Given the high hyperspectral nature and good data quality, IASI hyperspectral measurements allow more accurate comparisons of measured radiances with other broadband instruments sharing the same spectral regions, which provide an accurate evaluation for the on-board calibration. In this presentation, we explore the use of MetOP/IASI spectra to evaluate the radiances from the geostationary imagers. We will concentrate on the nadir observations with homogeneous regions. It is found that MetOp passes over the sub-point of a geostationary satellite every seven days. We will spectrally convolve the IASI measurements with the spectral response functions of the Geostationary Imagers. The spatial collocation will be performed to match the Geostationary Imagers and IASI pixels. Specifically, we will inter-calibrate the geostationary imagers on GOES-11 and GOES-12 using IASI by analyzing several months of datasets. The potential root causes of the bias will be investigated in this study, such as spectral uncertainties and day-night time effects. Compared with the existing studies that use the High Resolution Infrared Radiation Sounder (HIRS) and Atmospheric Infrared Sounders (AIRS) for inter-calibrating GOES imagers, using the IASI measurements does not need to deal with the spectral gaps and difference in the spectral response functions. We believe that IASI can potentially serve as a baseline to inter-calibrate the future Advanced Baseline Imager (ABI) flown the GOES-R satellite to verify the calibration of the ABI thermal channels.

Poster Session 1, Fifth GOES Users' Confererence Poster Session
Wednesday, 23 January 2008, 2:30 PM-4:00 PM, Exhibit Hall B

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