3.4.3. Relative Standard Deviation (RSD)

Similar to SD, we also extracted 90%, 95%, and 99% percentiles of relative standard deviation as shown in Figure 16. The 99% percentile of RSD (red color) mainly occurs in southern Tibet and western Sichuan, which is almost the same as the SD 99% percentile regions (Section 3.4.2). The 95% percentile of RSD (green color) mainly occurs in northern Tibet (region D in Figure 16) and Guizhou province, and 90% percentile of RSD (blue color) mainly occurs in northern Tibet (region D in Figure 16); this region is also analyzed by a boxplot (Figure 15d). In region A, the GLOBMAP LAI is a little low whereas the MODIS LAI is a little high. What is more, the LAI values in this region are lower than 0.2, which may attribute to the high relative standard deviation.

**Figure 16.** Percentile distribution of relative standard deviation of four LAI climatologies over China. Blue represents 90% percentile level, green represents 95% percentile level, and red represents 99% percentile level.

Then we counted the proportion of each land cover type at different significance levels (Table 8). At 99% and 95% percentile RSD levels, grassland, barren and evergreen needleleaf forest have the highest proportion; at the 90% percentage RSD level, grassland, cropland, barren and evergreen needleleaf forest have the highest proportion. This is generally in agreement with the RSD rankings shown in Table 4.

The results on the proportion of each climate type (Table 9) show that temperate warm summer/dry winter, cold dry winter/warm summer and temperate dry hot summer climate types are the top three at 99% percentile RSD level. Temperate warm summer/dry winter, cold dry winter/warm summer, and temperate hot summer/no dry season climate types are the top three at the 95% percentile RSD level, and temperate hot summer no dry season, cold dry winter warm summer and temperate warm summer dry winter climate types are the top three at 90% percentile RSD level.

In the LAI difference case analysis, ENF has both the highest SD and RSD among the four LAI products, while EBF and SAV have the highest SD, and SHR and GRA have the highest RSD. From the perspective of climate zones, tropical savannah, tropical monsoon, and temperate warm summer/no dry season climate show the highest mean SD, while cold zone dry and cold summer, cold zone dry and warm summer and temperate warm summer/dry winter climate show the highest RSD. The comparison of LAI differences for each biome type indicates that GLASS, GLOBALBNU, and GLOBMAP LAI are all higher than MODIS LAI for all biome types and most of the climate types. To look at this issue more closely, the 90%, 95%, and 99% percentile of difference have been studied, and results demonstrate that ENF and woody savannas have the highest proportion of large SD, whereas ENF and grassland are responsible for large RSD; temperate dry hot summer, temperate warm summer/dry winter, and temperate hot summer/no dry season climate account for the largest SD, and temperate warm summer/dry winter and cold dry winter/warm summer climate correspond to large RSD.


**Table 8.** Pixel proportion of different biome types at three relative standard deviation percentile levels.

**Table 9.** Pixel proportion of different climate types at three relative standard deviation percentile levels.

