Changes in characteristics of climate extremes from 1961 to 2017 in Qilian Mountain area, northwestern China

In this study, the temporal and spatial characteristics of extreme climate from 1961 to 2017 were analyzed using daily precipitation and temperature data from 24 meteorological stations in the Qilian Mountain area, northwestern China. The results showed that warming accelerated considerably after 1985, particularly during the 1990s. The warming trend then increased after 2000 and further increased after 2010. The Qilian Mountains and the Hexi and Qaidam Inland River Basins greatly affected the Atlantic Multidecadal Oscillation (AMO), Northern Tropical Atlantic Index (NTA), Caribbean sea-level surface temperature (SST) Index (CAR), South China Sea Summer Monsoon Index (SCSSMI), and South American Summer Monsoon Index (SAMSMI). The circulation index on the extreme temperature warm index was stronger than that of the extreme temperature cold index. There were greater increases in all extreme indexes in the central part of the Qilian Mountain area, and the region of increase decreased from inside to outside. The interannual change in the warming index of extreme temperature was similar to that of the cold index of extreme temperature. TX10, TN10, ice days (ID), and frost days (FD) showed significant negative correlations with altitude, whereas TXN and TNN showed significant positive correlations with altitude. Changes in TX10, TN10, TXN, TNN, ID, FD, and diurnal temperature range were most noticeable in high-altitude areas (> 2500 m), whereas changes in TN90, TX90, TXX, TNX, and growing season length were most noticeable in low altitude areas (< 2500 m). The Qilian Mountain area and the Hexi and Qaidam Inland River Basins were greatly affected by the AMO, NTA, CAR, SCSSMI, and SAMSMI; however, they were only slightly affected by the Nino4, Northern Atlantic Oscillation, North Pacific model, Southern Oscillation Index, Arctic Oscillation, and Multiple ENSO Index. The effect of the circulation index of Atlantic Multidecadal Oscillation, Tropical Northern Atlantic Index, Tropical Southern Atlantic Index, North Tropical Atlantic SST Index, and CAR on the extreme temperature warm index was stronger than that of the extreme temperature cold index.