SPATIOTEMPORAL CHANGES IN DAILY MAXIMUM AND MINIMUM TEMPERATURES AND THEIR RELATIONS WITH A LARGE-SCALE ATMOSPHERIC CIRCULATION PATTERN: A CASE STUDY IN THE WEI RIVER BASIN, CHINA

The long-term mean air temperature has increased with continued greenhouse-gas emissions in the past decades in the Wei River Basin (WRB) (China), with little understanding of the changes in extreme temperatures. In this study, the change characteristics of both maximum (Tmax) and minimum (Tmin) temperatures at daily, monthly, and annual scales were fully examined, and their relations with the Arctic Oscillation (AO) were also explored. The modified Mann-Kendall trend test method (MMK) and heuristic segmentation method were employed to detect the trends and change points of the Tmax and Tmin at multiple scales, respectively. Subsequently, the cross wavelet transform was adopted to reveal the correlations between Tmax/Tmin and AO. Results indicated: (1) both monthly and annual Tmax and Tmin showed significantly increasing trends, whilst at daily scale they generally exhibited no obvious trends; (2) change points were found in monthly, seasonal, and annual Tmax and Tmin, implying that the stationarity of Tmax and Tmin series in the WRB has been ineffective; (3) AO had strong impacts on Tmax and Tmin changes in the WRB. Our results highlight the asymmetric response of Tmax and Tmin at the monthly, seasonal, and annual scales, which has great implications for ecosystem functions and agricultural production.