The Bowen ratio (B) is impacted by 5 environmental elements: soil moisture availabillity, m, the ratio of resistances between atmosphere and soil pores, atmospheric relative humidity, h,atmospheric stability, △T, an...The Bowen ratio (B) is impacted by 5 environmental elements: soil moisture availabillity, m, the ratio of resistances between atmosphere and soil pores, atmospheric relative humidity, h,atmospheric stability, △T, and enviD ronment temperature. These impacts have been investigated over diverse surfaces, including bare soil, free water surface, and vegetation covered land, using an analytical approach. It was concluded that: (a) B is not a continuous function. The singularity exists at the condition αhcb = h, occurring preferably in the following conditions f weak turbulence, stable stratified stability, dry soil, and humid air, where hcb, defined by Eq.(11) is a critical variable. The existence of a singularity makes the dependence of B on the five variables very complicated. The value of B approaches being inversely proportional to m under the conditions m≥mfc (the soil capacity) and / 0.The proportional coefficient changes with season and latitude with relatively high values in winter and over the poles; (b) B is nearly independent of during the day. The impact of m on B is much larger as compared to that of on B; (c) when h increases, the absolute value of B also increases; (d) over bare soil,when the absolute surface net radiation increases, the absolute value of B will increase. The impact of RN on B is larger at night than during the day, and (e) over plant canopy, the singularity and the dependdes of B on m,rα, and h are modified as compared to that over bare soil.Also (i) during the daytime unstable condition, m exerts an even stronger impact on B; at night, however,B changes are weak in response to the change in m; (ii) the value of B is much more sensitive in response to the changes of turbulent intensity; (iii) the B response to the variation of h over a vegetation covered area is weaker; and (iv) the singularity exists at the condition hcp=h instead of αhcb=h as over bare soil, where hcp is defined by Eq.(49). The formulas derived over bare soil also hold the same when applied to free water bodies as long as they are visualized as a special soil in which the volumetric fraction of soil pore is equal to one and are fully filled with water.Finally, the above discussions are used to briefly study the impact on the thermally induced mesoscale circulations.展开更多
The impact of soil moisture availability on the Bowen ratio and on the partition of net radiation flux into sensible, latent and soil heat fluxes was investigated by using one-dimensional primitive equations with a re...The impact of soil moisture availability on the Bowen ratio and on the partition of net radiation flux into sensible, latent and soil heat fluxes was investigated by using one-dimensional primitive equations with a refined soil parameterization scheme. Simulation results presented that as soil moisture availability increases, the Bowen ratio and the partition of net radiation flux into sensible and soil heat fluxes decrease. The partition of net radiation flux into latent heat flux, however, increases. Quantitative relationships between Bowen ratio and the partitions with soil moisture availability were also given in this study.展开更多
文摘The Bowen ratio (B) is impacted by 5 environmental elements: soil moisture availabillity, m, the ratio of resistances between atmosphere and soil pores, atmospheric relative humidity, h,atmospheric stability, △T, and enviD ronment temperature. These impacts have been investigated over diverse surfaces, including bare soil, free water surface, and vegetation covered land, using an analytical approach. It was concluded that: (a) B is not a continuous function. The singularity exists at the condition αhcb = h, occurring preferably in the following conditions f weak turbulence, stable stratified stability, dry soil, and humid air, where hcb, defined by Eq.(11) is a critical variable. The existence of a singularity makes the dependence of B on the five variables very complicated. The value of B approaches being inversely proportional to m under the conditions m≥mfc (the soil capacity) and / 0.The proportional coefficient changes with season and latitude with relatively high values in winter and over the poles; (b) B is nearly independent of during the day. The impact of m on B is much larger as compared to that of on B; (c) when h increases, the absolute value of B also increases; (d) over bare soil,when the absolute surface net radiation increases, the absolute value of B will increase. The impact of RN on B is larger at night than during the day, and (e) over plant canopy, the singularity and the dependdes of B on m,rα, and h are modified as compared to that over bare soil.Also (i) during the daytime unstable condition, m exerts an even stronger impact on B; at night, however,B changes are weak in response to the change in m; (ii) the value of B is much more sensitive in response to the changes of turbulent intensity; (iii) the B response to the variation of h over a vegetation covered area is weaker; and (iv) the singularity exists at the condition hcp=h instead of αhcb=h as over bare soil, where hcp is defined by Eq.(49). The formulas derived over bare soil also hold the same when applied to free water bodies as long as they are visualized as a special soil in which the volumetric fraction of soil pore is equal to one and are fully filled with water.Finally, the above discussions are used to briefly study the impact on the thermally induced mesoscale circulations.
文摘The impact of soil moisture availability on the Bowen ratio and on the partition of net radiation flux into sensible, latent and soil heat fluxes was investigated by using one-dimensional primitive equations with a refined soil parameterization scheme. Simulation results presented that as soil moisture availability increases, the Bowen ratio and the partition of net radiation flux into sensible and soil heat fluxes decrease. The partition of net radiation flux into latent heat flux, however, increases. Quantitative relationships between Bowen ratio and the partitions with soil moisture availability were also given in this study.
