Kexin Zhang

Using MetOp-A AVHRR Clear-Sky Measurements to Cloud-Clear MetOp-A IASI Column Radiances

AbstractHigh spatial resolution measurements from the Advanced Very High Resolution Radiometer (AVHRR) on the Meteorological Operation (MetOp)-A satellite that are collocated to the footprints from the Infrared Atmospheric Sounding Interferometer (IASI) on the satellite are exploited to improve and quality control cloud-cleared radiances obtained from the IASI. For a partial set of mostly ocean MetOp-A orbits collected on 3 October 2010 for latitudes between 70°S and 75°N, these cloud-cleared radiances and clear-sky subpixel AVHRR measurements within the IASI footprint agree to better than 0.25-K root-mean-squared difference for AVHRR window channels with almost zero bias. For the same dataset, surface skin temperatures retrieved using the combined AVHRR, IASI, and Advanced Microwave Sounding Unit (AMSU) cloud-clearing algorithm match well with ECMWF model surface skin temperatures over ocean, yielding total uncertainties ≤1.2 K for scenes with up to 97% cloudiness.

Pre-Launch Evaluation of NPP-CrIMSS EDR Algorithm Products with Matched ECMWF Analysis, RAOB Measurements, and IASI Retrievals

Atmospheric vertical temperature and moisture profiles retrieved by the Cross-track Infrared Sounder and Advanced Technology Microwave Sounder (CrIMSS) algorithm were evaluated with matched radiosonde measurements, model analysis, and retrievals from Infrared Atmospheric Sounder Interferometer (IASI) observations.

A Methodology to Adjust ATMS Observations for Limb Effect and Its Applications

The Advanced Technology Microwave Sounders (ATMS), carried on the Suomi National Polar-orbiting Partnership (S-NPP) satellite, was launched on October 28, 2011. The ATMS is a follow-on instrument to Advanced Microwave Sounding Unit (AMSU), currently flying on National Oceanic and Atmospheric Administration (NOAA) satellites. The primary new ATMS features are a reduced hardware package and improved gap coverage. One thing in common about cross-track sounders is a scan perpendicular to the motion of the satellite, allowing a broad swath of measurements to be taken. But an undesirable feature is that the measurements vary with scan angle because of changes in the optical pathlength through the earths atmosphere between the earth and the satellite. One approach to this problem is to limb adjust the measurements to a fixed view angle. The limb correction algorithm applied to ATMS is based on the heritage methodology originally applied to MSU and later to AMSU. The limb correction method is applied to each of the 96 ATMS field-of-view (FOV) per scan line, adjusting the off-nadir FOV to the nadir view with fitting error generally within the instrumental noise. The limb adjusted brightness temperature were used in the original, legacy TOVS and ATOVS NOAA sounding product algorithms and more recently to derive the total precipitation water (TPW) retrieval over ocean, with a bias of 0.046 mm and a standard deviation of 3.43 mm, when compared with ECMWF TPW data. The limb corrected brightness temperature can be used to detect the atmospheric weather features, such as the warm cores for tropical cyclones, and the imagery presents snapshots for quick weather signal diagnosis.

Estimation of Near-Real-Time Outgoing Longwave Radiation from Cross-Track Infrared Sounder (CrIS) Radiance Measurements

AbstractThis study describes the algorithm for deriving near-real-time outgoing longwave radiation (OLR) from Cross-Track Infrared Sounder (CrIS) hyperspectral infrared sounder radiance measurements. The estimation of OLR on a near-real-time basis provides a unique perspective for studying the variability of Earth’s current atmospheric radiation budget. CrIS-derived OLR values are estimated as a weighted linear combination of CrIS-adjusted “pseudochannel” radiances. The algorithm uses the Atmospheric Infrared Sounder (AIRS) as the transfer instrument, and a least squares regression algorithm is applied to generate two sets of regression coefficients. The first set of regression coefficients is derived from collocated Clouds and the Earth’s Radiant Energy System (CERES) OLR on Aqua and pseudochannel radiances calculated from AIRS radiances. The second set of coefficients is derived to adjust the CrIS pseudochannel radiance to account for the differences in pseudochannel radiances between AIRS and CrIS. The...

Validation of IASI Temperature and Water Vapor Retrievals with Global Radiosonde Measurements and Model Forecasts

Atmospheric temperature and water vapor profiles retrieved from the MetOp-IASI instrument were evaluated with global radiosonde measurements and ECMWF analysis. Analysis of information content embedded in these retrievals was also attempted.