Radiative Processes in the Stable Boundary Layer: Part II. The Development of the Nocturnal Boundary Layer |
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| Authors: | J M Edwards |
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| Institution: | (1) Met Office, FitzRoy Road, Exeter, EX1 3PB, UK |
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| Abstract: | The interaction between radiation and turbulence in the stable boundary layer over land is explored using an idealized model,
with a focus on the surface layer after the evening transition. It is shown that finer vertical resolution is required in
transitional boundary layers than in developed ones. In very light winds radiative cooling determines the temperature profile,
even if similarity functions without a critical Richardson number are used; standard surface similarity theory applied over
thick layers then yields poor forecasts of near-surface air temperatures. These points are illustrated with field data. Simulations
of the developing nocturnal boundary layer are used to explore the wider role of radiation. Comparatively, radiation is less
significant within the developed stable boundary layer than during the transition; although, as previous studies have found,
it remains important towards the top of the stable layer and in the residual layer. Near the ground, reducing the surface
emissivity below one is found to yield modest relative radiative warming rather than intense cooling, which reduces the potential
importance of radiation in the developed surface layer. The profile of the radiative heating rate may be strongly dependent
on other processes, leading to quite varied behaviour. |
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| Keywords: | Evening transition Near-surface air temperature Radiative cooling Stable boundary layer |
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