*4.1. Spatial Pattern*

Figure 3 shows six *DI* maps that were averaged based on the annual draught indices from 2001 to 2018. Figure 3a–e presents those drought indices whose lower values indicate severe drought, while Figure 3f shows the TVDI map for which a higher value indicates severe drought.

**Figure 3.** Six drought indices averaged over 18 years for the Greater Changbai Mountains (GCM). (**a**) Precipitation condition index (PCI), (**b**) temperature condition index (TCI), (**c**) vegetation condition index (VCI), (**d**) vegetation health index (VHI), (**e**) scaled drought condition index (SDCI), and (**f**) temperature–vegetation dryness index (TVDI).

According to the PCI shown in Figure 3a and the classification scheme presented in Table 4, the southeast area of the GCM region where Baishan, Tonghua, and Dandong Cities are located, exhibits no drought conditions, whereas the northeast area (ShuangyaShan) has a low PCI value, indicating obvious drought conditions. Most of the remaining areas had slight or no drought. The TCI and VCI maps show slightly different drought patterns. According to the TCI map, most of the GCM area experienced drought conditions, except for the mountains in the central region. The VCI map indicates that most of the area experienced slight or no drought, except for the low-lying areas in the southwest and northeast. Since the TCI is related to LST, and the VCI is related to NDVI, the conflict between the TCI and VCI suggests that vegetation flourished in the mountains despite the high LST, indicating that the vegetation in the GCM area has high drought endurance. The VHI is high (no drought/wet conditions) in the southeast area with high elevation, while low (drought conditions) in the low-lying southwest and northeast areas. The other area has moderate VHI values, indicating mild drought conditions according to the classification in Table 4. The SDCI map shows a pattern similar to that of the PCI map, largely because the PCI is an important factor in the SDCI. According to the TVDI map, no drought conditions occurred in the southeast area with high elevation. The remaining parts of the region exhibited slight to moderate drought conditions. The spatial pattern of the TVDI was similar to that of the VHI. Thus, these six indices exhibit different drought information for the GCM area. This is mainly because they are calculated from different combinations of precipitation, LST, and vegetation status. Thus far, we cannot conclude which index is more reliable because they all try to reflect one

or more aspects of drought conditions. The di fferences among the index maps also suggests that the method for drought monitoring should be selected carefully.
