Recorded presentation2.2
Recalibrating Historical HIRS Visible Channel Measurements towards Creating Fundamental Climate Data Records
Likun Wang, Perot System Government Service, Camp Spring, MD ; and C. Cao
The High-Resolution Infrared Radiation Sounder (HIRS) is an operational broadband atmospheric sounding instrument with 12 longwave IR, 7 shortwave IR, and 1 visible channels, which has been carried on the National Oceanic and Atmospheric Administration (NOAA) Polar Operational Environmental Satellites (POES) for almost 30 years since it was first flown on TIROS-N (Television InfraRed Operational Satellite-N) in 1978. Designed for weather applications, HIRS is mainly used for the operational retrievals of atmospheric temperature and humidity profiles from the IR channels, while the HIRS visible channel is used for cloud detection. With nearly 30 years of the HIRS data, the measurements of the reflected radiation at the top of the atmosphere in the visible channel (channel 20; 0.67–0.71 μm) can potentially become an important climate datasets. However, due to the lack of on-board calibration, the effort to create the climate data records from the HIRS visible channels suffers from poor data quality. This study focuses on recalibrating 22 years of the HIRS visible channel measurements from NOAA6 to NOAA17 using the deep convective clouds (DCC) and Antarctic Dome C site as calibration targets. DCC are excellent calibration targets because they are cold, bright, stable, tropopause level, and nearly isotropic targets located near the equator, which can be easily identified by a simple infrared threshold. By comparison, Dome C site is climatologically stable with a relative uniform snow surface and extremely dry atmospheric condition with low cloud amount and aerosol loading. Both calibration methods have the potential to meet the stability requirements for climate change detection. In this study, the instrument degradation rate is vicariously characterized by tracking the time series of DCC observations from the HIRS visible channel. Then, the Dome-C is used as a transfer calibration site to establish the traceability of HIRS visible channel calibration to Moderate Resolution Imaging Spectroradiometer (MODIS). The final goal of this study is to create the climate data records for the HIRS visible channel historic measurements with accurate calibration.
Session 2, Climate Monitoring and Studies—II
Thursday, 15 January 2009, 11:00 AM-12:15 PM, Room 126BC
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