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Land-atmospheric water and energy cycle of winter wheat,Loess Plateau,China


International journal of Climatology


Tangtang Zhang,Jun Wen,Zhigang Wei,Rogier van der Velde,Zhenchao Li,Rong Liu,Shaoning Lv,Hao Chen









Corresponding Author

Zhang, TT

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land surface process; water and energy cycle; eddy correlation data correction; winter wheat


Surface energy partitioning and the characteristics of the water and energy cycle provide important information for improving land surface and weather forecast modelling. In this study, the land-atmospheric water and energy cycle of winter wheat was investigated on Loess Plateau in the northwest of China, using the eddy covariance technique, soil heat flux, and four component radiation measurements during the period from 8 April 2006 to 15 July 2006. Results show that the four components underwent daily changes throughout the period, and varied diurnally according to the synoptic conditions. Latent heat flux was the main consumer of available energy during the studied period. The daily energy partitionings LE/Rn, Hs/Rn and G0/Rn were on average 45%, 34% and 10%, respectively, and the Bowen ratio is estimated at 0.90. Surface albedo of winter wheat field was on average 0.19, over the total period from 8 April to 15 July, but decreased at the time of the heading of the wheat as compared to other seasons because of increased vegetation cover. The energy closure results show that the energy balance closure reached 89% through a thermal storage term of soil correction, which indicates that an energy imbalance of 11% was encountered in our observations. The daily variations in the water and energy fluxes were also analysed, including the diurnal variations on cloudy and clear sky days. Results show that the available sensible as well as latent heat flux both changed daily. The latent heat flux was primarily controlled by antecedent precipitation, with several high latent heat flux days being produced after intensive rain events. The sensible heat flux was mainly controlled by net radiation.