Abstract
To investigate the mechanism of available energy partitioning to sensible and latent heat fluxes over semi-arid regions, data from the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL) were analyzed to assess the effects of soil moisture, net radiation, and vapor pressure deficit (VPD) on available energy partitioning, as quantified by Bowen ratio. It was found that the Bowen ratio decreased rapidly with increasing soil moisture when soil was dry but was insensitive to the change in soil moisture when soil became wet. Net radiation and VPD affected the sensitivity of the Bowen ratio to soil moisture under dry conditions and the soil moisture threshold above which the Bowen ratio became insensitive to soil moisture. The Bowen ratio increases with net radiation at a high level of VPD, while the Bowen ratio first increases and then decreases with net radiation at a low level of VPD. Reduced soil moisture enhanced the effects of the net radiation and VPD on available energy partitioning. The effects of the VPD on Bowen ratio depended on the relative strength of the positive and negative impacts of VPD on the latent heat flux under different soil and net radiation conditions.
Highlights
Mass and energy exchanges between the land surface and atmosphere are key components of land-atmosphere interactions [1,2,3]
This paper aims to answer the questionof how soil moisture, net radiation, and vapor pressure deficit (VPD) affect the partitioning of available energy over the semi-arid areas of the Loess Plateau in China
The Bowen ratio decreases rapidly with increasing soil moisture when the soil is than a threshold under relatively dry conditions
Summary
Mass and energy exchanges between the land surface and atmosphere are key components of land-atmosphere interactions [1,2,3]. Sensible heat flux and latent heat flux, key variables in energy and water vapor exchanges between the land surface and atmosphere, drive the dynamics of the. The available energy, which is the difference between the net radiation and soil heat flux, is partitioned into the sensible heat flux and latent heat flux [8,9]. This partitioning of available energy has an important effect on regional climates, the water cycle, boundary layer characteristics, and cloud development [10,11,12,13]. Zeng et al [15] used a series of Weather
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