Emissivity of clear skies

Berdahl, Paul; Martin, M.

doi:10.1016/0038-092x(84)90144-0

Cited by 203 publications

(69 citation statements)

References 3 publications

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“…In this work, in order to evaluate ε sky , use was made of the expression developed by Paul and Martin (1984) that correlates ε sky with T dp and the solar hour for clear sky (see Table 2). Replacing this expression in equation (13), the following expression for T sky is obtained:…”

Section: Diffuse Solar Radiationmentioning

confidence: 99%

Physical modelling of globe and natural wet bulb temperatures to predict WBGT heat stress index in outdoor environments

Gaspar

Quintela

2009

Int J Biometeorol

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The present paper describes a physical model that estimates the globe and the natural wet bulb temperatures from the main parameters generally recorded at meteorological weather stations, in order to predict the wet bulb globe temperature (WBGT) heat stress index for outdoor environments. The model is supported by a thermal analysis of the globe and the natural wet bulb temperature sensors. The results of simultaneous measurements of the WBGT and climatological parameters (solar radiation, wind velocity, humidity, etc.) are presented and used to validate the model. The final comparison between calculated and measured values shows a good agreement with the experimental data, with a maximum absolute deviation of 2.8% for the globe temperature and 2.6% for the natural wet bulb temperature and the WBGT index. The model is applied to the design reference year for Coimbra, Portugal, in order to illustrate its preventative capabilities from a practical point of view. The results clearly show that during the summer there is a critical daily period (1200-1600 hours, local standard time) during which people working outdoors should not be allowed to perform their normal activities.

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Section: Diffuse Solar Radiationmentioning

confidence: 99%

Physical modelling of globe and natural wet bulb temperatures to predict WBGT heat stress index in outdoor environments

Gaspar

Quintela

2009

Int J Biometeorol

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“…Emissivity formula was obtained by an approximate integration of the Schwartzschild's transfer equation for a standard atmosphere. 4) Berdahl and Martin (1984) (B&M) introduced some modifications to the formula developed by Berdahl and Fromberg (1982), based on the use of a more extensive dataset. Their final parameterisation was function of the dewpoint temperature, T d (°C).…”

Section: Clear Skiesmentioning

confidence: 99%

“…Berdahl and Martin (1984) proposed the addition of a corrective term evaluated as a function of the hour of the day:…”

Section: Parameterisations With Locally Fitted Coefficientsmentioning

confidence: 99%

Estimation of downwelling longwave irradiance under all‐sky conditions

Alados

Foyo-Moreno

Alados-Arboledas

2011

Intl Journal of Climatology

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This work is focused on the characterization and parameterisation of the downward atmospheric irradiance (LW) for clear and cloudy skies. LW is a component of the surface radiation budget that is present throughout the day. Unlike solar irradiance, LW is not measured routinely in extended networks, so it must be estimated indirectly. We evaluated five parameterisations for estimating LW under clear skies. After some consideration regarding the local fitting of the parameterisations, we analysed their different behaviour during day and night and propose a correction model for this effect. We use measurements registered at Tabernas (Spain) from 2001 to 2003. For the locally adjusted parameterisations the root mean square deviation (RMSD) and the mean bias deviation (MBD) are smaller than 5.7 and 0.6%, respectively. The combination of the more complex correction parameterisation of the day/night differences with the locally adjusted formula of Brutsaert and the original formula of Berdalh and Martin leads to estimations with RMSD below 3.1%. Using data registered at Palaiseau (France) the proposed parameterisations yields MBD close to 0% and RMSD below 3.2%. Cloudy conditions were analysed and two different approaches were used to estimate the cloud effect. Both approaches determine all sky LW using a clear-sky formulae and a cloud modification factor, computed with the solar global irradiance on a horizontal surface. The results show that LW can be estimated under all-sky conditions during the daytime with a RMSD of 5.8 and 6.2%, and a MBD of 1.6 and −2.2% for the Crawford and Duchon scheme and the parameterisation in k t , respectively, at Tabernas. The application of the same parameterisations to Palaiseau yields RMSD of 6.7 and 7.7%, and MBD of −2.5 and 0.7%.

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“…Bliss, 1961;Berdahl & Martin, 1984) take into consideration the dew point temperature. According to Bliss (1961), for a clear night with high humidity, T sky can be around 10 K cooler than T o .…”

Section: The Cfd Modelmentioning

confidence: 99%

Shading screens for the improvement of the night time climate of unheated greenhouses

Montero¹,

Muñoz²,

Sánchez-Guerrero

et al. 2013

Span. j. agric. res.

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The objective of this work was to study the effect of shading screens, normally used during the day for cooling purposes, on the night-time climate of unheated greenhouses. For this purpose, first a number of experimental measurements were taken during cold nights to characterise the greenhouse climate both with and without an aluminised external screen. Secondly a Computational Fluid Dynamic (CFD) model of greenhouse was developed. After validation of the model by comparison with experimental data, the model was used to simulate the greenhouse climate for different sky conditions ranging from cloudless to overcast nights. Simulations were performed for a greenhouse with internal and external shading screens and for the same greenhouse without screens. Experimental results showed the positive effect of an external shading screen, whose use increased night-time temperature and reduced the risk of thermal inversion. Its effect was much stronger under clear sky conditions. The CFD model supported this conclusion and provided a detailed explanation of the temperature behaviour of all the greenhouse types considered. CFD simulations proved that an aluminised screen placed inside the greenhouse at gutter height gave the greatest thermal increase. Therefore, external or internal screens can help to increase the sustainability of greenhouse production in areas with mild winter climates by enhancing the use of solar energy stored in the greenhouse soil during the previous day and released at night-time.

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Emissivity of clear skies

Cited by 203 publications

References 3 publications

Physical modelling of globe and natural wet bulb temperatures to predict WBGT heat stress index in outdoor environments

Physical modelling of globe and natural wet bulb temperatures to predict WBGT heat stress index in outdoor environments

Estimation of downwelling longwave irradiance under all‐sky conditions

Shading screens for the improvement of the night time climate of unheated greenhouses

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