The Role of Solar Radiation and Water Vapor Pressure Deficit on Controlling Latent Heat Flux Density over the Alpine Wetland of the Source Region of the Yellow River
As the alpine wetland underlying surface is moist and sensitive to climate change,quantitative assessments of environmental factors on the influence of latent heat flux over there have important scientific significance.Environmental factors on the influence of latent heat flux are potential to be expressed as sums of the atmosphere and surface factors.By using the datasets collected from the land surface process field experiment which was conducted in the source region of the Yellow River from June 1 to August 31,2014,the characteristics of solar radiation and water vapour pressure deficit in controlling latent heat flux density were analyzed,and further assessment was evaluated by a defined controlling factor.The main results are as follows:(1) The average values of relative atmospheric controlling factors on latent heat flux density exercised by solar radiation and water vapour pressure deficit are 0.98 and 0.02.Relative atmospheric controlling factor on latent heat flux density is mainly exercised by solar radiation,and the role of water vapour pressure deficit is only marginal.(2) The average values of relative surface controlling factor over latent heat flux density exercised by solar radiation and water vapour pressure deficit are 0.12 and-0.31.The former is larger in the morning and evening,and smaller in the noon.The absolute value of the latter is smaller in the morning and evening,and larger in the noon.(3) The average values of absolute total controlling over the latent heat flux density exercised by solar radiation and water vapour pressure deficit are 0.22 and-0.06 W·m~(-2)·Pa~(-1).The average values of relative total control are 1.10 and-0.29.(4) Solar radiation controls the latent heat flux mainly through a direct effect (atmospheric factor).While the water vapour pressure deficit controls latent heat flux mainly through the indirect effect of altering surface resistance (surface factor).(5) The average value of the decoupling factor over the alpine wetland is 0.38.It implied that the coupling between the alpine wetland and atmospheric is low.It is of practical,the solar radiation is the main factor to control the latent heat flux over alpine wetland.This study provides a new research approach for the study of the parameterization of latent heat flux and evaporation under the context of global climate change.