Spatiotemporal relationship between evaporation and temperature in the south and north of Qinling Mountains and its influential factors

: Evaporation ( ET 0 ) is an important part of the hydrological cycle. A detailed analysis of the relationship between ET 0 and meteorological factors is of great significance for water resources, ecological restoration and reconstruction, and sustainable development of social and economic in China ’ s important ecological transition zone. In this paper, based on the data from 70 meteorological stations in the south and north of Qinling Mountains during 1970—2017, potential evaporation was first calculated using FAO (Food and Agriculture Organization of the United Nations) Penman - Monteith model. Moreover, variation of temperature and ET 0 in the south and north of Qinling Mountains is analyzed and the relationship between ET 0 and meteorological factors i.e., temperature, wind speed, sunshine duration, relative humidity are investigated to determine which factor primarily influences ET 0 using a sliding correlation coefficient and wavelet coherence. The results are as follow: based on the mutual correspondence of trends, there is uncertainty in the response relationship between ET 0 and temperature in the south and north of Qinling Mountains. It is not a simple reverse correspondence, that is, the higher the temperature, the more the evaporation. Based on the sliding correlation coefficient, whether we adjusted the size of sliding correlation window or divided the different time periods, there is always a significant positive correlation between ET 0 and temperature, implying that the existence of “ evaporation paradox ” phenomenon in the study region could not be detected. However, there is a spatiotemporal difference in the correlation between the temperature and ET 0 in the south and north of Qinling Mountains. In terms of the relationship between temperature and evaporation, 1993 was a turning change point since the correlation in the whole period increased initially and then decreased. In terms of spatial variation, regardless of the sequence (original or detrending) and sliding correlation window (11 a or 21 a), the correlation pattern of temperature and ET 0 in the south and north of Qinling Mountains has not changed much, while a weak correlation is observed in the western part of Qinling Mountains. For the influence of meteorological factors change on ET 0 change, it is well established that with the observed decreased sunshine duration and wind speed and increased relative humidity, the ET 0 has been decreasing over the past 48 a, which confirmed three existing assumptions: (1) the reductions in sunshine duration is the first factor for the decline in ET 0 resulting from the evidences in three sub - regions in the south and north of Qinling Mountains, (2) the decreasing wind speed is the second factor for the decline in both northern and south piedmont of Qinling Mountains, and (3) the increasing change in relative humidity exacerbated the decrease of ET 0 in Hanjiang River Basin. However, temperature is the last related factor to ET 0 in south and north of Qinling Mountains. The interaction of multiple factors may influence the variation of ET 0 rate, which is the main reason for the complexity of the ‘ evaporation paradox ’ in south and north of Qinling Mountains.