Probabilistic Assessment of the Impact of Compound Dry and Hot Events on Vegetation Drought Over Northwestern China

Climate extremes have garnered considerable attention recently because of their devastating effects on both water resources and vegetation health. The vegetation responses to climate extremes, such as high temperatures (hot events), droughts (dry events) and compound dry and hot events (CDHEs), have been extensively evaluated. However, the risk of vegetation drought considering different severity levels of individual and compound climate extremes is not well assessed. In this study, we employed the meta-Gaussian (MG) model, a multivariate approach, to evaluate the response of vegetation drought [characterized by the Standardized Normalized Difference Vegetation Index (SNDVI)] to dry events, hot events and CDHEs. The study found that the dominant factor of vegetation drought, in the central and northwestern parts of Northwestern China (NWC), was the dry events. Conversely, in the southern NWC, temperature exerted a substantial influence on vegetation drought. Relative to individual dry events (hot events), the conditional probability of vegetation drought under CDHEs had decreased (increased) by approximately 24% (17%). Furthermore, the response of grassland to both individual and compound climate extremes was sensitive, whereas forests demonstrated greater resilience to droughts. These findings help us better understand the influence that various severity levels of climate extremes exert on vegetation dynamics.