Author Affiliations
1National Satellite Meteorological Center (National Center for Space Weather), Key Laboratory of Radiometric Calibration and Validation for Environmental Satellites, China Meteorological Administration, Beijing 100081, China2Innovation Center for FengYun Meteorological Satellite (FYSIC), Beijing 100081, China3School of Surveying and Land Information Engineering, Henan Polytechnic University, Jiaozuo 454003, Henan, Chinashow less
Fig. 1. Flowchart of the MERSI-II radiometric response evaluate method based on DCC
Fig. 2. DCC reflectance PDF curves for different VZA angle intervals. (a) 0.65 μm; (b) 1.64 μm
Fig. 3. Normalized monthly DCC reflectance corrected by BRDF models from 2018 to 2022. (a) 0.65 μm; (b) 1.64 μm
Fig. 4. Geographical distribution of monthly DCC from 2020 to 2022. (a) Every April; (b) every July
Fig. 5. Annual variation curves of DCC monthly reflectance from 2018 to 2022. (a) 1.64 μm; (b) 2.13 μm
Fig. 6. Seasonal correction factor of DCC
Fig. 7. Comparison of deseasonalization and BRDF correction results. (a) 0.65 μm; (b) 0.865 μm; (c) 1.64 μm; (d) 2.13 μm
Fig. 8. Normalized monthly DCC reflectance and linear fitting of FY-3D/MERSI-II in RSB from 2018 to 2022. (a) VIS bands; (b) NIR bands; (c) SWIR bands
| Band | Central wavelength /μm | Spectra bandwidth /μm | Resolution /m | Dynamic range |
|---|
| 1 | 0.470 | 50 | 250 | 90% | | 2 | 0.550 | 50 | 250 | 90% | | 3 | 0.650 | 50 | 250 | 90% | | 4 | 0.865 | 50 | 250 | 90% | | 5 | 1.380 | 20/30 | 1000 | 90% | | 6 | 1.640 | 50 | 1000 | 90% | | 7 | 2.130 | 50 | 1000 | 90% | | 8 | 0.412 | 20 | 1000 | 30% | | 9 | 0.443 | 20 | 1000 | 30% | | 10 | 0.490 | 20 | 1000 | 30% | | 11 | 0.555 | 20 | 1000 | 30% | | 12 | 0.670 | 20 | 1000 | 30% | | 13 | 0.709 | 20 | 1000 | 30% | | 14 | 0.746 | 20 | 1000 | 30% | | 15 | 0.865 | 20 | 1000 | 30% | | 16 | 0.905 | 20 | 1000 | 100% | | 17 | 0.936 | 20 | 1000 | 100% | | 18 | 0.940 | 50 | 1000 | 100% | | 19 | 1.030 | 20 | 1000 | 100% | | 20 | 3.800 | 180 | 1000 | 200-350 K | | 21 | 4.050 | 155 | 1000 | 200-380 K | | 22 | 7.200 | 500 | 1000 | 180-280 K | | 23 | 8.550 | 300 | 1000 | 180-300 K | | 24 | 10.800 | 1000 | 250 | 180-330 K | | 25 | 12.000 | 1000 | 250 | 180-330 K |
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Table 1. FY-3D/MERSI-II spectral channel specifications
| Band | Center wavelength /μm | Standard deviation of mean（mode）/% |
|---|
| No BRDF | Hu BRDF | CERES BRDF |
|---|
| 1 | 0.470 | 2.32（1.93） | 2.22（1.94） | 1.93（0.76） | | 2 | 0.550 | 2.62（2.13） | 2.72（2.11） | 2.33（0.83） | | 3 | 0.650 | 2.73（2.22） | 2.45（2.01） | 1.65（0.77） | | 4 | 0.865 | 1.63（1.58） | 1.53（1.42） | 1.66（0.73） | | 5 | 1.380 | 0.83（1.08） | 1.13（1.28） | 1.16（1.33） | | 6 | 1.640 | 0.82（0.89） | 0.87（0.96） | 0.98（1.10） | | 7 | 2.130 | 0.76（0.88） | 1.26（1.36） | 1.08（1.21） | | 16 | 0.905 | 1.44（1.28） | 1.43（1.12） | 1.41（0.53） | | 17 | 0.936 | 1.53（1.28） | 1.58（1.17） | 1.66（0.73） | | 18 | 0.940 | 1.22（1.08） | 1.37（1.04） | 1.66（0.67） | | 19 | 1.030 | 1.47（1.13） | 1.33（1.02） | 1.67（0.74） |
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Table 2. Standard deviation of PDF reflectance mean (mode) in different VZA angle intervals
| Spectral band /μm | Decline rate of RSD /% | Decline rate of 2δ/mean /% |
|---|
| 0.470 | 10.3 | 29.9 | | 0.550 | 9.6 | 27.3 | | 0.650 | 28.9 | 44.3 | | 0.865 | 16.7 | 30.5 | | 1.380 | 22.4 | 52.7 | | 1.640 | 22.0 | 51.2 | | 2.130 | 23.9 | 54.5 | | 0.905 | 17.6 | 33.5 | | 0.936 | 18.3 | 35.6 | | 0.940 | 18.1 | 32.4 | | 1.030 | 20.4 | 42.8 |
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Table 3. Decline rates of DCC reflectance RSD and fluctuation in each channel after deseasonal correction
| Condition | Parameter |
|---|
| Spectral bands | B1-B7，B16-19 | | Data time | 2018—2022 | | Longitude /（o） | -180-+180 | | Latitude /（o） | -20-+20 | | SZA，VZA /（o） | ≤40 | | IR-BT threshold /K | ≤205 | | IR-BT uniformity threshold /K | ≤1 | | VIS uniformity threshold /% | ≤3 | | Reflectance | Monthly PDF mode（VIS/NIR），mean（SWIR） | | Reflectance correction | CERES ice cloud BRDF（VIS/NIR），deseasonal（SWIR） |
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Table 4. Summary of the research area, data, and methods
| Band | Central wavelength /μm | Reflectance mean | Total degradation rate /% | Annual degradation rate /% | σ/% |
|---|
| 1 | 0.470 | 0.8999 | 6.9110 | 1.3820 | 1.1740 | | 2 | 0.550 | 0.8853 | 1.7330 | 0.3466 | 0.9643 | | 3 | 0.650 | 0.8957 | 0.1428 | 0.0286 | 0.9640 | | 4 | 0.865 | 0.9178 | 2.2060 | 0.4412 | 1.0640 | | 5 | 1.380 | 0.5023 | 16.1500 | 3.2310 | 4.0120 | | 6 | 1.640 | 0.2248 | 15.5700 | 3.1140 | 3.5650 | | 7 | 2.130 | 0.1501 | 10.6700 | 2.1340 | 3.1670 | | 16 | 0.905 | 0.8617 | 2.5540 | 0.5108 | 1.7270 | | 17 | 0.936 | 0.7571 | 3.6040 | 0.7208 | 2.5310 | | 18 | 0.940 | 0.8424 | 4.5720 | 0.9144 | 2.9850 | | 19 | 1.030 | 0.8223 | 9.7620 | 1.9520 | 1.1910 |
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Table 5. Results of FY-3D/MERSI-II reflected solar bands radiation response degradation from 2018 to 2022
