Three-dimensional linkage between meteorological drought and vegetation drought across China

Advance knowledge of the linkage between meteorological drought and vegetation drought is relevant for the risk of droughts and the impacts on vegetation health. This study employs a 3-dimensional clustering identification method to capture drought events and their characteristics (i.e., drought severity, intensity, area, center, and trajectory) in vegetated regions of China during 1982-2018. The probability of vegetation droughts, triggered by different types of drought events, is investigated by using a K-means trajectory clustering method and copula with the vegetation health index (VHI). Moreover, the impacts of moisture deficit and high temperature caused by drought on vegetation are examined with the vegetation condition index (VCI) and temperature condition index (TCI). The analysis has identified a total of 93 drought events in 1982-2018. The drought occurrences have become more concentrated in space along the time and droughts frequently occur in spring and summer. Drought events are categorized into three types, and droughts in type 1 lead to vegetation droughts with larger area, droughts in type 2 lead to vegetation droughts with stronger intensity, droughts in type 3 pose the least threat to vegetation. Additionally, the impacts of moisture deficit and high temperature have significant seasonal difference and contradictory trends over time. For example, grassland is most sensitive to moisture deficit in summer, while forest is the most sensitive to moisture deficit in spring and winter. The complex response of vegetation to drought is resulted from the combined effects of moisture and heat stress and different regional climate and vegetation types.