Characteristics and causes of abnormal heat temperature and drought in the Central Hexi Corridor in 2023

The 2023 compound heat and drought event occurred once in 60 years in central Hexi Corridor, which adversely affected local agricultural production and the ecological environment and caused serious economic losses. This study uses various observational datasets to discuss the characteristics and effects of the high-temperature drought in the central Hexi Corridor in 2023 from the perspectives of meteorology, hydrology, ecology and agriculture. We further examine responses of summer precipitation in the central the Hexi Corridor to anomalous atmospheric circulation and sea surface temperature (SST). These datastes include monthly precipitation and temperature data during 1951-2023 from six national basic stations in the central Hexi Corridor, Heihe River runoff data from Yingluoxia hydrological Station in the upper reaches of Heihe River, FY-3D/MERSI satellite data, GF-1 satellite data, and NCEP/NCAR monthly mean reanalysis data, the 88 atmospheric circulation indexes and 26 SST indexes provided by NCC. The results show that the mean precipitation and average temperature in the central Hexi Corridor from May to September, 2023, monthly average temperature in June, August and September broke through the historical extreme values and reached record highs. In the middle Qilian Mountains, the averaged snow cover area decreased by 45.8%, the annual runoff decreased by 15%, the main reservoir area decreased by 25.8%-66.0%. The transmission characteristics of drought are meteorological drought → hydrological drought → ecological and agricultural drought. We find that precipitation in the central of Hexi Corridor from May to September has significant multi-scale oscillations in 5a, 11a, 17a and 32a, and multiple time scales show that 2023 is in a period of less oscillation. When the drought in the central the Hexi Corridor is observed, the atmospheric circulation anomalies include: a southward shifted ridge line of the subtropical high in the Western Pacific Ocean, the eastward shifted ridge point of the western extension, the westward shifted ridge point of the South Asian high pressure, a weak Indian low is weak, the small polar vortex area in the northern hemisphere and Asia, the strong blocking high in the middle and high latitudes in Asia is strong, the increased longitude of the westerly circulation in Eurasia and Asia. Meanwhile, The SST anomalies are warm in the Nino3 area and the west wind drift region, but cold in the Kuroshio region.