Assessing drought disaster hazard in Xinjiang of China using MCI and Gumbel-Copula function

Drought is one of the major meteorological disasters in the world. It is urgent to accurately assess the frequency of drought events and the risk of drought disasters in the region, particularly for the warning, prevention and mitigation of regional damage. In this study, the MCI (meteorological drought composite index) was calculated using the daily observation data from the 106 meteorological stations in Xinjiang in western China during 1961-2019. The drought process was identified using the runs theory. The joint distribution of duration and intensity was also established to calculate the return period using the Gumbel-Copula function. Eventually, the hazard factors were taken as the frequency duration and intensity of drought events. The weights were calculated to assess the hazards of drought using the random forest. The results show that there were 47 drought events in the study area during 1961-2019. Among them, drought events with short duration and low intensity (intensity ≤ 50 and duration ≤ 60d) were frequent, whereas, the extreme drought events occurred less frequently with long duration and high intensity (intensity ≥200 and duration ≥180 d) tend to associtate with longer return periods. Long duration and high intensity tended to occur simultaneously. However, the probability of occurrence decreased with the increasing drought duration and intensity. The drought return period was longer along the Tianshan mountain range than that of other regions under the same duration and intensity conditions. The spatial distribution of drought hazards was performed as the middle low, and the high north-south ends. The hazard was much lower along the Tianshan Mountains. The drought events occurred less frequently on the northern slope, especially with the short duration and the low intensity. The higher hazards can be observed in most parts of the southern region. A similar trend was found in the northwestern part of the Tarbagatay Prefecture, as well as the central and northern of the Altay Prefecture in the northern region. There were different characteristics of drought, although the hazards were high in both the northern and southern regions. The drought events occurred less frequently, but lasted for a long duration with the high intensity in most stations in the southern region. However, the high frequency of droughts was found in the northern region, but for a short duration and low intensity. The northern and southern regions should respond to the drought disasters in different plans. An efficient drought early warning and monitoring system can consider the drought occurrences and development trends in the local conditions. Efficient allocation and utilization of water resources can then be balanced to reduce the risk of drought disasters.