Examination of Radiometric Deviations in Bands 29, 31, and 32 of MODIS Collection 6.0 and 6.1.

The radiometric stability of selected thermal emissive bands (TEBs) of the Moderate-Resolution Imaging Spectroradiometer (MODIS) on the Terra and Aqua satellites is examined via a direct intersensor comparison with the Visible Infrared Imaging Radiometer Suite (VIIRS) aboard the Suomi National Polar-orbiting Partnership (SNPP) satellite. The analysis adapts a “nadir-only” refinement of the simultaneous nadir overpasses (SNOs) analysis to evaluate radiometric deviations in MODIS Collection 6.0 and 6.1 data releases, the latter having been implemented with a version of crosstalk effect mitigation for Terra MODIS bands 27–30. The comparison time series result, with an average precision of 0.4%, shows radiometric deviation in Terra MODIS band 29 ($8.55~\mu \text{m}$) up to 6%, or 3 K in brightness temperature (BT), in Collection 6.0, and correspondingly −1.5%, or −0.7 K in BT, in Collection 6.1, in particular significantly worsened by the safe mode event of February 2016. This paper includes the inter-TEB comparisons of MODIS bands B31 and B32 with SNPP VIIRS as two representative cases of nonideal spectral match demonstrating various key features and new information as revealed under the “nadir-only” framework, and also describes a procedure using both radiance-to-radiance comparison and BT-difference time series to estimate the BT-difference uncertainty specifications as well as the radiance-to-radiance time series baselines that are shifted away from unity. The finding for Terra MODIS band 29 highlights the continual nontrivial impact of crosstalk effect on numerous TEBs of MODIS Collection 6.1 not fully mitigated, which can further impact cloud masks, sea surface temperatures, and other product retrievals. [ABSTRACT FROM AUTHOR]