Beyond that, a constraint of the maximum and minimum value of emissivity between 0 and 1 is also used in our study to ensure that all retrieved LSEs are in the physical range.
To directly compare CrIS LSEs with AIRS, we interpolated the CrIS LSEs into identical channels in the AIRS LSE product from 800 to 970 [cm.sup.-1]: 819.67 [cm.sup.-1] (B1), 847.46 [cm.sup.-1] (B2), 877.19 [cm.sup.-1] (B3), 909.09 [cm.sup.-1] (B4), and 943.4 [cm.sup.-1] (B5).
According to Table 2, the total RMSDs of the LSEs at each band are approximately 1.22-1.66%.
From Figure 4(a), it is clear that the LSEs retrieved from November were with an obvious bias error, which indicates the ISSTES algorithm was more sensitive to the atmospheric correction under dry-cold conditions.
As shown, when the mean LSEs are compared, the retrieved LSEs exhibit good shape consistency with the AIRS product.
Currently, a simultaneous solution approach is used to retrieve the atmospheric profiles together with the LST and LSEs from the CrIS data .
Unlike the complicated simultaneous approach used to retrieve atmospheric profiles, LST, and LSEs, in this paper, a simpler method with two steps are used, (1) atmospheric correction and (2) TES, to retrieve just the LST and LSEs from the CrIS data.
Compared with the present approach, our method is more effective and provides comparable accuracies for both the LST and LSEs with a higher spatial resolution.
When evaluating the retrievals of LSEs, because CrIS and AIRS have notably different spatial and temporal features, only the AIRS pixels covered with sufficient CrIS pixels within 6 hours of acquisition time are used in our study.
Caption: Figure 4: The comparisons of LSEs between CrIS and AIRS: (a) scatterplots of LSEs in five bands for 2 months; (b) histograms of LSE differences between CrIS and AIRS.
Land Surface Temperature and Emissivity (LST and LSE) are two key parameters in quantitative remote sensing and have been widely used in many fields such as meteorological and climate models, lithological mapping, and resources exploration [1,2].
Unlike the validation for LSTs, because no LSE product can be provided by the instruments onboard the S-NPP, the AIRS, which was also used as a reference instrument in designing the CrIS, is selected in our study for evaluating the LSE retrievals.