*Letter* **Monitoring Droughts in the Greater Changbai Mountains Using Multiple Remote Sensing-Based Drought Indices**

**Yang Han 1,**†**, Ziying Li 1,**†**, Chang Huang 2,\*, Yuyu Zhou 3, Shengwei Zong 1, Tianyi Hao 1, Haofang Niu 1 and Haiyan Yao 1**


Received: 26 December 2019; Accepted: 3 February 2020; Published: 6 February 2020

**Abstract:** Various drought indices have been developed to monitor drought conditions. Each index has typical characteristics that make it applicable to a specific environment. In this study, six popular drought indices, namely, precipitation condition index (PCI), temperature condition index (TCI), vegetation condition index (VCI), vegetation health index (VHI), scaled drought condition index (SDCI), and temperature–vegetation dryness index (TVDI), have been used to monitor droughts in the Greater Changbai Mountains(GCM) in recent years. The spatial pattern and temporal trend of droughts in this area in the period 2001–2018 were explored by calculating these indices from multi-source remote sensing data. Significant spatial–temporal variations were identified. The results of a slope analysis along with the F-statistic test showed that up to 20% of the study area showed a significant increasing or decreasing trend in drought. It was found that some drought indices cannot be explained by meteorological observations because of the time lag between meteorological drought and vegetation response. The drought condition and its changing pattern di ffer from various land cover types and indices, but the relative drought situation of di fferent landforms is consistent among all indices. This work provides a basic reference for reasonably choosing drought indices for monitoring drought in the GCM to gain a better understanding of the ecosystem conditions and environment.

**Keywords:** multi-source remote sensing data; drought index; trend analysis; MODIS; TMPA
