A set of equations for full spectrum and 8‐ to 14‐μm and 10.5‐ to 12.5‐μm thermal radiation from cloudless skies

Idso, Sherwood B.

doi:10.1029/wr017i002p00295

Cited by 483 publications

(301 citation statements)

References 28 publications

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“…The oldest approach to estimate cloud coverage is based on surface observer reports which include temporal and spatial miss-matches as well as observer subjectivity, which [Idso, 1981] …”

Section: The Clear-sky Indexmentioning

confidence: 99%

The clear‐sky index to separate clear‐sky from cloudy‐sky situations in climate research

Marty

Philipona

2000

Geophysical Research Letters

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Abstract. Accurate surface radiation fluxes are required to quantify atmosphere-surface energy exchanges. In climate research, detailed investigations of the influence of diverse atmospheric conditions on radiative fluxes ask for a welldefined distinction between clear-sky and cloudy-sky situations. Effects of clouds, the so called "cloud forcing", can only be determined by explicitly separating clear-sky from all-sky radiation measurements. A Clear-Sky Index (CSI) to separate clear-sky from cloudy-sky situations has therefore been introduced, using accurate atmospheric longwave radiation in conjunction with air temperature and humidity measurements at the station. This clear-sky index, which has the important advantage to be applicable 24 hours a day, was tested and first used on measurements of the Alpine Surface Radiation Budget (ASRB) network, and was of prime importance for the determination of the altitude dependence of cloud forcing and greenhouse effect over the Alps.

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“…The oldest approach to estimate cloud coverage is based on surface observer reports which include temporal and spatial miss-matches as well as observer subjectivity, which [Idso, 1981] …”

Section: The Clear-sky Indexmentioning

confidence: 99%

The clear‐sky index to separate clear‐sky from cloudy‐sky situations in climate research

Marty

Philipona

2000

Geophysical Research Letters

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“…Most of these parameterisations were derived for night-time data using local empirical coefficients (Brunt, 1932;Idso and Jackson, 1969;Brutsaert, 1975;Idso, 1981). Several authors (Paltridge, 1970;Berdahl and Fromberg, 1982;Alados-Arboledas and Jiménez, 1988;Alados-Arboledas, 1993;Dupont et al, 2008) pointed out the differences between the day and night effective emissivity regimes.…”

Section: Introductionmentioning

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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“…is the clear sky atmospheric emissivity dependent on atmospheric water content [Idso, 1981] given by e, = 0.74 + 0.0049e [Bras, 1990] and e is the vapor pressure in millibars, error for all the 0600 surface temperatures lumped together from all the IFCs is 1.3 K. Figure 10 shows the scatterplot between the observed and the simulated 0600 surface temperatures. The agreement is very good.…”

Section: The Incoming Longwave Radiation Is Given By •O-t 4 Where •mentioning

confidence: 99%

A soil‐canopy‐atmosphere model for use in satellite microwave remote sensing

Lakshmi¹,

Wood²,

Choudhury³

1997

J. Geophys. Res.

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Abstract. Regional and global scale studies of land-surface-atmosphere interactions require the use of observations for calibration and validation. In situ field observations are not representative of the distributed nature of land surface characteristics, and large-scale field experiments are expensive undertakings. In light of these requirements and shortcomings, satellite observations serve our purposes adequately. The use of satellite data in land surface modeling requires developing a hydrological model with a thin upper layer to be compatible with the nature of the satellite observations and that would evaluate the soil moisture and soil temperature of a thin layer close to the surface. This paper outlines the formulation of a thin layer hydrological model for use in simulating the soil moistures and soil temperatures. This thin layer hydrological model is the first step in our attempt to use microwave brightness temperature data for regional soil moisture estimation. The hydrological model presented here has been calibrated using five years (1980- utilization of remotely sensed data is important for the purposes of understanding spatial variability and regional scales and in verifying land surface parameterizations [Wood, 1991].Projects like the Global Energy and Water Experiment (GCiP) Continental Scale International Project (GCIP) involve the development and testing of hydrological models on a continental scale over the southern plains of the United States. The availability of data sets for the validation of continental scale soil moisture simulations would be very useful. There are many advantages to remote sensing as a method of soil moisture determination as compared to field sampling. Field sampling is point based and does not give a clear picture of the variation of the soil moisture over an area. Accuracy (difference between the actual soil moisture pattern and the interpolated soil moisture pattern) of interpolation schemes depends on the closeness of the sampled soil moisture data points and the heterogeneity of the soil moisture distribution. In the case where the correlation lengths of soil moisture are smaller than the measurement spatial interval, ground-based data collection may result in the biased sampling of the soil moisture.Satellite remote sensing offers spatial coverage and a certain temporal frequency in monitoring soil moisture from space. The microwave frequencies of the electromagnetic spectrum are the most sensitive to the variations of soil moisture [Schmugge, 1985] fine spatial resolution to simulate the soil moistures close to stream channels; it is used for a catchment in an average sense. The parameters in the following paragraph deal with the soil-vegetation system which is built on the physics to capture the diurnal cycle of the land surface response to atmospheric forcings. The soil hydraulic parameters deal with the movement of moisture in the soil; the soil thermal properties characterize the soil surface interaction with long and shortwave radiation. The vegetation...

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A set of equations for full spectrum and 8‐ to 14‐μm and 10.5‐ to 12.5‐μm thermal radiation from cloudless skies

Cited by 483 publications

References 28 publications

The clear‐sky index to separate clear‐sky from cloudy‐sky situations in climate research

The clear‐sky index to separate clear‐sky from cloudy‐sky situations in climate research

Estimation of downwelling longwave irradiance under all‐sky conditions

A soil‐canopy‐atmosphere model for use in satellite microwave remote sensing

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