Evaluation of VIIRS thermal emissive bands inter-sensor consistency using radiative transfer modeling

This study evaluates the inter-sensor consistency of the Visible Infrared Imaging Radiometer Suite (VIIRS) moderate-resolution Thermal Emissive Bands (M TEBs; M12–M16) across three satellites−Suomi National Polar-orbiting Partnership (S-NPP), NOAA-20, and NOAA-21, covering a period from March 18, 2023, to June 30, 2024. The field of interest is limited to the ocean surface between 60°S and 60°N, specifically under clear-sky conditions. Taking radiative transfer modeling (RTM) as the transfer reference, we employed the Community Radiative Transfer Model (CRTM) to simulate VIIRS TEB brightness temperatures (BTs) using collocated European Centre for Medium-range Weather Forecasts (ECMWF) reanalysis data as inputs. <br/> <br/> Excellent inter-sensor consistency among these three VIIRS instruments is confirmed through the double-difference analysis method (O-O) using CRTM simulation as a radiance transfer. This method relies on the observation minus background BT differences (O-B ΔBTs), between VIIRS measurements obtained from daily operational data (O) and CRTM simulations (B). The mean inter-VIIRS O-O BT differences remain within 0.08 K for all M-band TEBs, except for M13. Even in the case of M13, the O-O BT differences between NOAA-21 and NOAA-20/S-NPP have values of 0.312 K and 0.236 K, respectively, which are comparable to the 0.2 K difference observed in overlapping TEBs between VIIRS and MODIS at simultaneous nadir overpasses (SNOs). These disparities are primarily attributed to the significant differences in the Spectral Response Function (SRF) of NOAA-21 compared to NOAA-20 and S-NPP. <br/> <br/> Our study confirms the effectiveness of the RTM-based TEB quality evaluation method in assessing inter-sensor consistency. The double-difference approach effectively mitigates uncertainties and biases inherent to CRTM simulations, establishing a robust mechanism for assessing inter-sensor consistency. Moreover, it has been noticed that for M12, both the time-series of O-O and O-B BT differences possess the greatest vibrations (i.e., largest standard deviations) compared to other bands, alongside the distinct seasonal variations of O-B BT differences. These observations can be attributed to the fact that M12 radiance is affected by reflected solar radiation during daytime, as M12 operates as a shortwave infrared channel. Furthermore, in this study, we’ve also characterized the spatial distributions of inter-VIIRS BT differences, identifying variations among VIIRS M TEBs.