Free and Forced Convection Effects on Evaporation

Sill, Ben L.

doi:10.1061/(asce)0733-9429(1983)109:9(1216)

Cited by 30 publications

(32 citation statements)

References 6 publications

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“…As a conclusion from these analyses, for small water surfaces with low wind speeds the wind function (which is commonly used in mass transfer methods to estimate evaporation from water surfaces) can be justified for free convection situations. As this issue is beyond the aims of this study the reader is referred to the literature, for example Sill (1983), Huang (2002) and Edson et al (2007), for more details.…”

Section: Sensible and Latent Heat Fluxesmentioning

confidence: 99%

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

Abbasi

Annor

Giesen

2017

Hydrological Sciences Journal

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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

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Section: Sensible and Latent Heat Fluxesmentioning

confidence: 99%

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

Abbasi

Annor

Giesen

2017

Hydrological Sciences Journal

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“…The evaporation rate is commonly expressed as a function of the forced convection provided by wind. However for sites like Mirror Lake, evaporation can still be significant under light or even negligible winds when the boundary layer near the air-water interface is unstable and free convection is present (Ryan et al, 1974;Sill, 1983). The latent heat flux formula developed by Ryan et al (1974) and improved by Adams et al (1990) includes both wind-forced convection and free convection under an unstable atmosphere.…”

Section: Appendix I: Heat Flux Formulationsmentioning

confidence: 99%

Predicting the onset of thermal stratification in shallow inland waterbodies

Branco

Torgersen

2009

Aquat. Sci.

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Diurnal thermal stratification in shallow lakes and ponds is well documented and affects biogeochemical gradients. The onset of thermal stratification should occur when the stratification parameter I S = -HB/u* rises above a critical value, I crit . Previous applications of the stratification parameter lack a common definition for the onset stratification and include assumptions inappropriate for shallow inland waterbodies. Here, the onset of stratification is defined relative to a practical threshold given by the Rohr-Stillinger criterion, N 2 = e/(20n). Using this definition, the utility of I S for predicting stratification in two shallow ponds was evaluated using select periods from over 600 days of temperature profiles, standard weather data and measured light attenuation coefficients. Though uncertainties in B and u* can produce errors in I S on the order of 40 -60 %, the parameter is robust for predicting the onset of stratification. Accuracy can be improved by sitespecific determinations of wind sheltering. The critical value for the onset of stratification was found to be approximately 1. The stratification parameter can be an effective screening tool for 1) predicting the presence of significant chemical gradients, and 2) determining the minimum wind speed required to prevent diurnal thermal stratification from developing.

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“…In summary, the longwave terms are based on blackbody calculations, including emissivity terms. The calculation of evaporation includes both convective and mechanical removal of water vapour (Sill, 1983) such that the evaporative flux depends on the wind speed, humidity gradient and also on the air-sea temperature difference. The sensible heat transfer is calculated from the evaporation using a Bowen ratio approach (see e.g.…”

Section: ~T ~ I(kh+~z) ~T ) ~0mentioning

confidence: 99%

Modelling sea surface temperature rise resulting from increasing atmospheric carbon dioxide concentrations

Henderson‐Sellers

1987

Climatic Change

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Concern over the role of the oceans in a warming world, likely to result from increasing atmospheric carbon dioxide, has prompted analysis using simple models. Results from two recent, independent studies using a simple box-diffusion model suggest that over the last 130 years, observations and models are not in disagreement. Although a diffusive deep ocean was indeed included in this simplistic model, it is suggested here that the resulting ocean model offers an oversimplistic view of the oceanic contribution to the overall global atmosphere-ocean climate system and that it is necessary to add a convective capability to the water column. Using this approach it is suggested that, on a timescale of a century, the sea surface temperature increase is likely to be less by a factor of at least 3 than that previously forecast.

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Free and Forced Convection Effects on Evaporation

Cited by 30 publications

References 6 publications

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

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

Predicting the onset of thermal stratification in shallow inland waterbodies

Modelling sea surface temperature rise resulting from increasing atmospheric carbon dioxide concentrations

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