Table 1.
Description of the three NDVI NOAA-AVHRR data sets used in this study [adapted from 27, 30, 31, 34, Los personal communication, updated version of 36, 64, 69, 70].
| PAL | GIMMS | FASIR | |
|---|---|---|---|
| Data Set Origins (and its spatial resolution) | NOAA-AVHRR GAC 1B (4 km) | NOAA-AVHRR GAC 1B (4 km) | Radiance in PAL dataset (8 km) [32] |
| Instrument and change in times | 7, 9, 11, 14 | 7, 9, 11, 9 (descending), 14, 16 | 7, 9, 11, 14 |
| Known temporal span | 1981-2001 | 1981-2006 | 1982-1999 |
| Temporal resolution | 10 days | 15 days | 10 days |
| Spatial resolution | 8 km | 8 km | 8 km |
| Spatial compositing | Forward, nearest neighbor mapping. Selection of the 4 km pixel with the maximum NDVI value for the 8 km output bin. Only pixels within 42° of nadir are considered. | Forward, nearest neighbor mapping. Selection of the 4 km pixel with the maximum NDVI value for the 8 km output bin. | Inherited from PAL series. |
| Temporal compositing | Maximum NDVI values composition of the 10-days images [60]. | Maximum NDVI values composition of the 15-days images [60]. | Inherited from PAL series. |
| Radiometric corrections | Calibration with pre-flight constants modified by degradation over time [61], based on the use of desert invariant calibration targets. | NOAA-7 to NOAA-14 channels 1 and 2 calibrations using the Vermote and Kaufman parameters [62]. NOAA-16 channels calibrations using pre-flight values. Data further adjustment using invariant desert targets [28]. | Data correction following the Los technique of invariant desert targets [28]. |
| Viewing and illumination corrections | No specific corrections have been applied. | Correction of illumination and viewing angle effects using the adaptive empirical mode decomposition (EMD) method [63]. | Correction of illumination and viewing angle effects with Bidirectional Reflectance Distribution Function (BRDF) techniques for Pathfinder radiances [64]. |
| Cloud corrections | Based on Cloud Advanced Very High Resolution Radiometer (CLAVR) algorithm [65]. | Based on thermal band. | Based on thermal band and reconstruction of tropical evergreen broadleaf vegetation data with a maximum filter. |
| Stratospheric aerosols correction | No corrections. | Volcanic aerosol correction for 1982-1984 and 1991- 1994 [66, 67]. | Volcanic aerosol correction for 1982-1984 and 1991-1994 [66]. |
| Molecular absorption and scattering corrections | Ozone absorption from the Total Ozone Mapping Spectrometer (TOMS) data set, and Rayleigh scattering [68]. | No corrections. | Inherited from PAL series. |
| Manual checking | On every layer of the composite files. | On navigation accuracy, data drop outs, bad scan lines, and other strange values. | On navigation accuracy, data drop outs, bad scan lines, and other strange values. |
| Noise attenuation | Not applied. | Removal of noise and attenuation of cloud and missing pixels effects with Kriging interpolation. | Replacement of extreme outliers and missing data with the long-term mean. Posterior restoration of outliers caused by cloud interferences and short-term atmospheric effects through Fourier Adjustment. |
| Scaling procedures | Not applied. | Match with SPOT Vegetation NDVI data during overlapping period [34]. | Data extrapolation for winter needleleaf evergreen areas. |