A senior research scientist supporting the CLARREO Pathfinder and CERES projects within the Climate Science Branch of the NASA Langley Research Center (LaRC) Science Directorate in Hampton, VA. His current research focuses on developing techniques of in-flight calibration of geostationary and low-earth orbiting satellite visible observations to assess the sensor’s performance on-orbit and ensure the usability of climate data.
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Nine of the 100 km PICS had clear-sky probabilities between 45% to 55%, however the clear-sky probability for Mali, Mauritania-1, and Mauritania-2 was less than 30%. The 1.61μm, 0.65μm, 2.15μm, 0.48μm, and 0.55μm band atmospheric corrections improved the temporal stability by 5-19%, 12-24%, 47-68%, 22-68%, and 14-54%, respectively. The PW atmospheric correction was the most effective across all PICS, whereas the AOD and ozone atmospheric corrections were less effective. Surprisingly, Libya-2 and Libya-4 had 0.48μm and 0.55μm band atmospheric correction reductions less than 22%, whereas Libya-1 had 0.48μm and 0.55μm band atmospheric corrections greater than 46%. However, the AOD and ozone variability was very similar for the Libya PICS. Libya-1 and Libya-2 are the most optimal PICS having temporal fluctuations within 0.5%. Algeria-1, Algeria-2, Algeria-3, Egypt-1, Libya-4, Niger-1, and Sudan-1 are favorable sites where the temporal variability was within 1.0%. Future work will include combining PICS stabilities as well as finding the most optimal 20 km region contained within the 100 km PICS to attain PICS temporal stabilities less than 0.5%.
Now that many of the recently launched GEO imagers have multiple reflective solar band channels, the DCCRM algorithm is being modified to inter-calibrate those channels as well, especially for the SWIR bands. The spectral uniformity of the DCC over the SWIR bands is not uniform, given that the ice particle absorption is a function of wavelength. New Spectral Band Adjustment Factor (SBAF) strategies will need to be developed. DCC-RM is also wellsuited to inter-calibrate historical near-broadband visible GEO imagers. DCC are spectrally flat across the visible spectrum, which reduces the SBAF uncertainty between two ray-matched sensors. Applying the DCC-RM technique on historical GEO imagers is challenging due to the coarser pixel and temporal resolution of the ISCCP B1U formatted dataset.
The ATO-RM and DCC-RM calibration methods were applied to multiple visible bands on Himawari-8 using MODIS as the calibration reference. The Aqua-MODIS and Himawari-8 calibration difference was less than 0.4% for wavelengths less than 1 µm and for the Terra-MODIS 0.65-μm channel. Other channel combinations would need further examination to obtain consistent ATO and DCC gain results. The ATO-RM and DCC-RM calibration methods were also applied to GOES-8 in the ISCCP B1U format with NOAA-14 AVHRR as the calibration reference. The GOES-8 ATO and DCC calibration gain difference was within 0.15%. The agreement between ATO and DCC gains provides confidence in both methods.
Response versus scan-angle corrections for MODIS reflective solar bands using deep convective clouds
This paper will present initial assessment results for interconsistency between VIIRS and Aqua-MODIS calibration of matching visible channels. Empirically derived exoatmospheric VIIRS radiance models for deep convective clouds and deserts invariant targets are used to assess the initial onboard calibration of VIIRS. The VIIRS models are based on characterizing these invariant targets with Aqua-MODIS as an absolute calibration reference in order to tie the VIIRS calibration to Aqua-MODIS. Correction for spectral band differences in the VIIRS and MODIS channels is performed using the SCIAMACHY hyperspectral data.
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