Characteristics and causes of abnormally high temperature and drought in the central Hexi Corridor in 2023

In 2023, the central part of the Hexi Corridor experienced an extreme high temperature and drought that would occur once every 60 years, which adversely affected local agricultural production and ecological environment, causing serious economic losses. This study uses various observational datasets to discuss the characteristics and effects of the high-temperature and drought in the central Hexi Corridor in 2023 from perspectives of meteorology, hydrology, ecology and agriculture. We further examine the responses of summer precipitation in the central Hexi Corridor to anomalous atmospheric circulation and sea surface temperature (SST). The datasets used in this study include monthly precipitation and temperature data during 1951—2023 from six national basic stations in the central Hexi Corridor, the Heihe river runoff data from Yingluoxia hydrological station in the upper reaches of the Heihe river, the FY-3D/MERSI satellite data, the GF-1 satellite data, and the NCEP/NCAR monthly mean reanalysis data, and 88 atmospheric circulation indexes and 26 SST indexes provided by National Climate Centre. The results show that precipitation and average temperature in the central part of the Hexi Corridor from May to September 2023 both exceeded historical extremes, with precipitation reached a new historical low and temperature reached a new historical high. The combined effect of high temperature and low precipitation significantly exacerbated the intensity of drought. In the middle Qilian mountains, the average snow cover area decreased by 45.8%, the annual runoff decreased by 15%, the main reservoir area decreased by 25.8%—66.0%. The characteristics of drought spread are meteorological drought—hydrological drought—ecological and agricultural drought. We find that precipitation in the central Hexi Corridor from May to September had significant multi-scale oscillations in 5, 11, 17 and 32 a, and multiple time scales showed that 2023 was in a period of less oscillation. When the drought in the central Hexi Corridor was observed, the atmospheric circulation anomalies included a southward shifted ridge line of the western Pacific subtropical high, an eastward shifted ridge point of the western extension, a westward shifted ridge point of the South Asian high pressure, a weaker than normal Indian low, a smaller polar vortex area in the northern hemisphere and Asia, a stronger blocking high in the middle and high latitudes of Asia, and increased longitudinal coverage of the westerly circulation in Eurasia. Meanwhile, positive SST anomalies occurred in the Nino3 area and the west wind drift region, while negative SST anomalies occurred in the Kuroshio region.