Changes and Drive Mechanism of Climate Extremes During Recent 60 Years in Qilian Mountains, Northwestern China

Abstract A interesting study of analyzing the temporal and spatial characteristics and the reason change of extreme climate indexes based on the daily precipitation and temperature data of 24 meteorological stations in Qilian Mountains from 1961 to 2017. The results showed that the interannual change of the warming index of extreme temperature was similar to that of the cold index of extreme temperature. All daily indexes of extreme precipitation except CWD passed the significance level test of 5%. All daily indexes of extreme precipitation except for CDD in Hexi inland river basin, Qaidam inland river basin and Yellow river basin showed an increasing trend. However, the increasing extent of CWD, R10MM, R20MM and R25MM in Yellow river basin was lower than that of Qilian Mountain. The warming range of the four indexes (TX10, TN10, TXN and TNN) decreased from south to north. The spatial distribution of PRCPTOT, SDII, RX1DAY, RX5DAY, R95 and R99 was similar in the Qilian Mountains. The central part of the Qilian Mountains was the area with larger increasing region, and the increase region decreased from inside to outside. TX10, TN10, ID, FD showed a significant negative correlation with altitude, while TXN, TNN showed a significant positive correlation with altitude. The changes of TX10, TN10, TXN, TNN, ID, FD and DTR were the most obvious in the high altitude area (> 2500m), and the changes of TN90, TX90, TXX, TNX and GSL were the most obvious in the low altitude area (< 2500m). Qilian Mountains, Hexi inland river basin and Qaidam inland river basin were greatly affected by the AMO, NTA, CAR, SCSSMI, SAMSMI and were slightly affected by the Nino4, NAO, NP, SOI, AO, MEI. Extreme precipitation days indexes of Yellow river basin is highly correlated with AO and SCSSMI. The effect of the circulation index of Atlantic multidecadal Oscillation, Tropical Northern Atlantic Index, Tropical Southern Atlantic Index, North Tropical Atlantic SST Index, Caribbean SST index on the extreme temperature warm index was stronger than that of extreme temperature cold index.