Observation Of Energy Partitioning And Lake Evaporation In The Badain Jaran Desert

This paper, using the eddy covariance method, combined with positioning observation of precipitation, radiation, water level in the desert hinterland, discussed the energy distribution and the evaporation of land and lake surface in the hinterland of Badain Jaran desert and its response to changes in the weather and seasonal changes. The land surface energy closure was also evaluated and we calculated the recharge of a typical lake based on the water balance modle. The following conclusions:(1) The downward and upward shortwave radiation as well as net radiation of the land surface and the lake surface was gradually reduced along with weather of "sunny-cloudy-cloudy-precipitation". On the other hand, the downward longwave radiation and the lake’s upward longwave radiation presentd a increasing trend.(2) Similar to the land surface energy distribution of the response to the changes in the weather, sensible heat accounted for the major part of the net radiation on land surface. Cloud and precipitation could all directly affect the land surface sensible heat flux and latent heat flux, and the former generally decreased with increasing cloudiness, and the latter gradually increased. The typical sunny land surface radiation budget and energy distribution on behalf of its climate mean state.(3) In terms of energy partitioning on lake surface, the latent heat flux appear no obvious change in response to different weather. On typical sunny day, the sensible heat of lake surface perform positive value between midnight and morning, and after noon, lake "temperature inversion" lead to sensible heat flux is negative. When precipitation emergy, air temperature decreased rapidly and it undermined the "temperature inversion" layer on the surface of the lake, and the sensible heat flux throughout the day are all positive. The latent heat exceeds the net radiation on lake surface indicated that the heat carried by the groundwater/spring water impact the in the lake energy cycle, and the horizontal heat transferd between the land surface and lake surface might also affect the latent heat flux on lake surface,however, the effect of former is much higher than the latter. The typical sunny of lake surface radiation budget and energy distribution could not represent its climate mean state.(4) With regard to the energy distribution seasonal variation, land surface sensible heat flux are accounted for more than half of the net radiation, and latent heat flux depends mainly on precipitation. The Bowen ratio of land surface vary evidently with different precipitation. The surface heat storage in up-layer can not be ignored in the energy balance study and the ratio of energy closure is0.859, higher than the case of without the consideration of up-layer heat storage, the latter is only roughly0.5. The daytime energy closure was significantly better than the nighttime. The lake sensible heat flux has a significant diurnal variation and average daily H accounts for about1%of the net radiation,however, the latent heat took up more than85%of the net radiation. Monthly Bowen ratio on lake surface is close to zero.(5) The evaporation of the lakes in the hinterland of the desert is greatly special. We should take consideration of the difference of the climate between the margin area and the hinterland as well as the cold island effect and the salinity effect of the lakes.The eddy covariance system could accurately calculate of lake evaporation. And with help from precipitation and water level observation, we can extrapolate the groundwater recharge to the typical lake. From March25,2012to September10, the average daily evaporation of the Yindeertu is5.3mm, and the average daily groundwater recharge is3.8mm. The wind speed is the main factors affecting lake evaporation. The amount of groundwater recharge performed no apparent relationship between evaporation and precipitation in desert.