Long-term change of potential evapotranspiration over southwest China and teleconnections with large-scale climate anomalies

Potential evapotranspiration (PET) is a sensitive factor for atmospheric and ecological systems over southwest China which is characterized by intensive karst geomorphology and fragile environment. Based on daily meteorological data of 94 stations during 1961-2013, the spatiotemporal characteristics of PET are analysed. The changing characteristics of local meteorological factors and large-scale climatic features are also investigated to explain the potential reasons for changing PET. Study results are as follows: (1) The high-value centre of PET with a mean value of 1097 mm a(-1) locates in the south mainly resulted from the regional climatic features of higher air temperature (TEM), sunshine duration (SSD) and lower relative humidity (RHU), and the low-value centre of PET with a mean value of 831 mm a(-1) is in the northeast primarily attributed to higher RHU and weaker SSD. (2) Annual PET decreases at -10.04 mm decade(-1) before the year 2000 but increases at 50.65 mm decade(-1) thereafter, and the dominant factors of PET change are SSD, RHU and wind speed (WIN), with the relative contributions of 33.29, 25.42 and 22.16%, respectively. (3) The abrupt change of PET in 2000 is strongly dominated by large-scale climatic anomalies. The strengthened 850 hPa geostrophic wind (0.51 m s(-1) decade(-1)), weakened total cloud cover (-2.25% decade(-1)) and 500 hPa water vapour flux (-2.85% decade(-1)) have provided advantageous dynamic, thermal and dry conditions for PET over southwest China since the 21st century.