Effects of atmospheric stability conditions on heat fluxes from small water surfaces in (semi-)arid regions

Abstract

Atmospheric stability conditions over the water surface can affect the evaporative and convective heat fluxes from the water surface. Atmospheric instability occurred 72.5% of the time and resulted in 44.7 and 89.2% increases in the average and maximum estimated evaporation, respectively, when compared to the neutral condition for a small shallow lake (Binaba) in Ghana. The proposed approach is based on the bulk-aerodynamic transfer method and the Monin-Obukhov similarity theory (MOST) using standard meteorological parameters measured over the surrounding land. For water surface temperature, a crucial parameter in heat flux estimation from water surfaces, an applicable method is proposed. This method was used to compute heat fluxes and compare them with observed heat fluxes. The heat flux model was validated using sensible heat fluxes measured with a 3-D sonic anemometer. The results show that an unstable atmospheric condition has a significant effect in enhancing evaporation alongside the sensible heat flux from water surfaces.ARTICLE HISTORY

Nighttime Cooling of an Urban Pond

“…where . λ, q s , and q z were calculated for each time step (Abbasi et al, 2017). where e sat [kPa] is saturated vapor pressure, e a [kPa] actual vapor pressure, and P atm [kPa] is atmospheric pressure.…”

Influence of Atmospheric Stability on the Size Distribution of the Vertical Dust Flux Measured in Eroding Conditions Over a Flat Bare Sandy Field

“…Again, this correction assumes that the vertical transport of particles and momentum are similar. However, relatively ancient (Businger, ; Businger et al, ) and more recent (Abbasi et al, ; Li & Bou‐Zeid, ; Smedman et al, ) studies indicate that even in slightly unstable conditions, the ratio of the eddy diffusivity of scalars (water vapor and heat) to that of momentum increases dramatically, which means that these scalars are transported more efficiently than momentum. For particles, experimental data are missing but Freire et al () used large eddy simulation to show that even in idealized conditions (spatially and temporally constant emission flux), atmospheric stability and particle size (in the range 1–30 μm) should be taken into account in the derivation of the surface net flux from the vertical profiles of concentration measured in the surface boundary layer.…”

The effects of small water surfaces on turbulent flow in the atmospheric boundary layer: URANS approach implemented in OpenFOAM

“…These were constructed to promote dry season farming (crop and livestock), fishing and domestic water uses. Their closeness to the point of use made them very attractive (Abbasi et al, 2017c;Keller et al, 2000). However with recent changes in climate (climate change), the small reservoirs which were to increase the resilience of the communities which use them are at risk from high evaporation losses from them.…”