Energy flux measurements and environmental controls in summer over the Poyang Lake, China

Abstract

气候变化加速了全球水文循环过程,然而,气候变化如何影响水体蒸发及其水热通量交换仍然不清楚.基于涡度相关系统观测鄱阳湖水体水热通量过程,在小时和日尺度分析了水热通量的变化规律及其主要影响因子.研究表明,潜热通量日变化波动剧烈,大部分为正值,变化范围在-50~580W/m²之间.而感热通量数值较小,变化范围在-50~50W/m²之间.8月份潜热通量和感热通量均呈波动下降趋势,均值分别为167.4和15.9W/m².8月份日平均潜热通量和感热通量之和大于净辐射,这是由于这一时段储存在水体中的热量释放并补充潜热通量和感热通量.小时尺度上潜热通量日变化在相位上与净辐射无显著相关性,而与风速显著相关.在日尺度变化趋势上,8月份日平均潜热通量仍主要受到风速和水温的影响,感热通量则主要受到风速和饱和水汽压差的影响.;Global hydrologic cycles have been intensified by climate change. However, the ways in which climate change affects the evaporation and surface energy budget over inland waters remain unclear. In this study, the surface energy fluxes were measured by an eddy covariance system over the Poyang Lake in August, 2013. We analyzed the hourly and daily variations of energy fluxes, and their responses to the environmental factors. The results showed that the latent heat flux (LE) has strong turbulence in diurnal variations compared with the sensible heat flux (H) over the Poyang Lake. Most of latent heat fluxes were positive values during the whole day, ranging in -50-580 W/m². The sensible heat flux showed a weakly variance with a range of -50-50 W/m². The daily mean latent and sensible heat flux showed a decreasing trend with a large fluctuation in August, with the daily mean LE and H of 167.4 and 15.9 W/m², respectively. The sum of daily mean LE and H was larger than the net radiation in August, due to heat storage in water body release and supplement of LE and H. In hourly scale, the latent heat flux was out of phase with net radiation, and has a good relationship with the wind speed. In daily scale, the mean LE was mainly controlled by the wind speed and saturate vapor pressure deficit, and H was controlled by the wind speed and air temperature.