Understanding the spatiotemporal variations of evapotranspiration (ET), the sum of evaporation and plant transpiration, is a vital component in regional hydrological studies in Asia. However, there is currently only limited knowledge which climatic variables influence the evaporative environment on global or regional scales.
Dr. FAN Zexin of Xishuangbanna Tropical Botanical Garden (XTBG) and Dr.Axel Thomas provided decadal (1961–2004) linear trends for Penman–Monteith reference evapotranspiration (ET0) rates and analyzed spatiotemporal trend variability over Yunnan Province. Monthly mean data for 119 stations in Yunnan Province were obtained from the National Meteorological Information Centre of China.
They analyzed trends of climatic parameters (sunshine duration, wind speed, temperature and relative humidity) and their temporal contribution to reference evapotranspiration rates. They aimed to: (1) evaluate temporal trends and spatial patterns of reference evapotranspiration rates and other climatic parameters over Yunnan Province; (2) identified the major climate factors contributing to reference evapotranspiration variability and (3) determined whether the relationship between reference evapotranspiration and its driving climatological variables was stable or not.
They found that the reference evapotranspiration rates had been decreasing during the past four decades (1961–2004), particularly in the eastern and northern parts of Yunnnan Province. Declines of reference evapotranspiration rates appeared to be linked primarily to decreasing sunshine duration in the humid summer and post-monsoon seasons. Relative humidity and maximum temperature contributed to some extent in the dry post-monsoon and winter seasons. The contribution of wind speed was minimal.
