Research On Complementary Relationship Between Water Surface And Unsaturated Soil Evaporation Based On In-situ Observation

Water surface evaporation and soil evaporation are not only significant components of the Earth's water cycle,but also a component of hydrological water resources evaluation.It is of great significance for water resource evaluation and management,ecology and environment to evaluate water surface evaporation and soil evaporation.However,due to the influence of climate factors,the relationship between the two was different,the relationship between the two is studied in this paper.Based on the complementary relationship,the purpose of this study is to investigate the relationship between the water surface evaporation and soil evaporation obtained from day scale experimental of different evaporation pans and Micro-lysimeter.Through analyzing the water surface evaporation,soil evaporation and meteorological data obtained from the in-situ test,the main conclusions were as following:?1?The daily mean value of soil evaporation during the test was 1.466mm·d^-1,the daily soil evaporation rate was fluctuated at 1mm·d^-11 while without rainfall,the maximum evaporation deviation is 0.1mm,and the maximum daily evaporation increaseed to 5mm·d^-1after rainfall.When the area of evaporation pans increased from 2.89m² to 4.84 m²,the evaporation rate of water surface was decreased to 91%of 2.89m².When the water depth of evaporation pans increased from 0.5m to 2.5m,the evaporation rate was reduced to 75.5%of 0.5m.?2?The correlation analysis of soil evaporation and meteorological factors was carried out by using SPSS software for meteorological elements observed in the experiment,which may affect soil evaporation.The results showed that there was a positive correlation between soil evaporation and soil moisture content,air relative humidity,net radiation and other factors.The soil temperature,air temperature,wind speed and the actual evaporation of soil were negatively correlated.?3?Based on principal component analysis?PCA?,the meteorological factors that affected the soil evaporation were analyzed,and two principal components were extracted,the two components contained the factors which influenced soil evaporation most were soil water conditions and solar radiation energy.It is indicated that the water content and solar radiation of soil are main factors controlling the soil evaporation in study area.At the same time,there existed an exponential correlation between the soil surface moisture content?15cm below soil surface?and the soil evaporation,and the correlation coefficient was greater than 0.5.?4?Based on the CR theory,the relationship between the soil evaporation and pan evaporation data obtained from the experiment were analyzed.The results showed that there existed an asymmetric complementary relationship between the two in the study area.The least square fitting was used to obtain the optimal value of the complementary coefficient b for each evaporation pan.The evaporation pan water surface evaporation will change b units while the soil evaporation changes by one unit.In the complementary relationship between different standard pans,complementary coefficient b decreased from 1.964 in the Russian style 3000 to 1.66 in the E601-B with the non-uniformity changed between the pans and the surro unding environment.The complementary coefficient b of evaporation pans with different areas decreased from 1.15 to 1.056 with an increase in the area of the pans.The complementary coefficient b of evaporation pans which the water depth changed from 0.5m to 2.5m processed from 1.77 to the final 1.16.?5?The relationship between soil evaporation and pan evaporation provides an new approach to calculate soil evaporation.Using the meteorological data to inverse computation soil evaporation,based on the reliability of calculated results and maneuverability of the pan evaporation test,it is recommended to use Class A pan to obtained actual soil evaporation in the study area,the complementary coefficient b is 1.87.