Evaporation abrupt changes in the Qinghai-Tibet Plateau during the last half-century

Pan evaporation (Epan) was regarded as a critical indicator of climate change, especially in the Qinghai-Tibet Plateau (QTP). By using the measured daily Epan data of 274 stations in the QTP from 1970 to 2017, the study detected abrupt changes in annual Epan series in different spatial scales, through integrating the Mann-Kendall abrupt change test, moving t-test and piecewise linear fitting model. Results showed that abrupt changes existed generally in the QTP where mean and trend abrupt changes were detected in 76.6% and 97.8% of 274 stations during the last half-century. Major abrupt change time of mean values and trends was respectively in around 1996, 1989 and 2007. In comparison, early abrupt changes were observed in the south (south of 30°N) and north (north of 35°N) but late ones in the midland (30–35°N). Corresponding to the low frequent behaviors, pan evaporation paradox only existed in the QTP as a whole in 1970–1990 and was not apparent at site scale, with less than 9.5% of 274 stations detected in different periods. The results confirmed prevailing abrupt change of pan evaporation and its distinct spatial pattern in the QTP.