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Applied Modeling of the Nighttime Surface Energy Balance over Land

A. A. M. HoltslagRoyal Netherlands Meteorological institute, de Bilt, The Netherlands

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H. A. R. De BruinDepartment of Physics and Meteorology, Agricultural University of Wageningen, The Netherlands

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Abstract

In this paper a semiempirical scheme is proposed which relates the nocturnal surface fluxes of sensible heat, latent heat, and momentum to routine weather data. The main components of the surface radiation and energy balance over land are described on a half-hourly basis. Observations over a grass-covered surface at Cabauw are used to investigate topics proposed in the literature, and to develop new parameterizations. The input data of the scheme are total cloud cover, wind speed, air temperature, and specific humidity deficit at single heights in the atmospheric surface layer. A semiempirical expression is proposed for the estimation of the soil heat flux. Also the relation between the surface radiation temperature and the temperature at the level of the roughness length is described semiempirically. It is found that their difference is considerable, especially for low wind speeds. The output of the scheme is presented in terms of the main forcing terms. On average, the agreement of the model quantities with observations is reasonable. For instance, for clear skies with total cloud cover N ≦ 0.25, it appears that root mean square errors are at best 9 W m−2 for sensible heat flux, 6 W m−2 for latent heat flux, 9 W m−2 for soil heat flux, 13 W m−2 for net radiation, and 1.8 K for surface radiation temperature. The temperature profile up to 80 m is well described by the present scheme. The difference of the scheme with previous methods in literature is discussed.

Abstract

In this paper a semiempirical scheme is proposed which relates the nocturnal surface fluxes of sensible heat, latent heat, and momentum to routine weather data. The main components of the surface radiation and energy balance over land are described on a half-hourly basis. Observations over a grass-covered surface at Cabauw are used to investigate topics proposed in the literature, and to develop new parameterizations. The input data of the scheme are total cloud cover, wind speed, air temperature, and specific humidity deficit at single heights in the atmospheric surface layer. A semiempirical expression is proposed for the estimation of the soil heat flux. Also the relation between the surface radiation temperature and the temperature at the level of the roughness length is described semiempirically. It is found that their difference is considerable, especially for low wind speeds. The output of the scheme is presented in terms of the main forcing terms. On average, the agreement of the model quantities with observations is reasonable. For instance, for clear skies with total cloud cover N ≦ 0.25, it appears that root mean square errors are at best 9 W m−2 for sensible heat flux, 6 W m−2 for latent heat flux, 9 W m−2 for soil heat flux, 13 W m−2 for net radiation, and 1.8 K for surface radiation temperature. The temperature profile up to 80 m is well described by the present scheme. The difference of the scheme with previous methods in literature is discussed.

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