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Project properties |
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| Title | Radiative cooling over flat and complex terrain: a forgotten term?
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| Group | Meteorology and Air Quality Group |
| Project type | thesis |
| Credits | 36 |
| Supervisor(s) | Gert-Jan Steeneveld (Gert-Jan.Steeneveld@wur.nl) |
| Examiner(s) | Prof. dr. AAM Holtslag |
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| Begin date | 2018/01/01 |
| End date | 2020/02/01 |
| Description | The atmospheric boundary layer undergoes a clear diurnal cycle. During daytime solar radiation heats the surface, and the warm land surface triggers thermals to develop, i.e. a convective boundary layer is created. During the daytime the 2 m temperature is strongly governed by turbulent mixing, i.e. the sensible heat flux H. After sunset, the land surface cools due to radiative cooling, and a stable boundary layer develops. At night the turbulence is relatively weak due to stable stratification and the 2 m temperature is governed by both turbulent mixing and longwave radiative cooling
Unfortunately the last term is a "forgotten factor" in both modeling and observational studies (Steeneveld et al., 2010). At the same time it is known that weather forecast and climate models have large difficulty with temperature forecasts in stable conditions (e.g. Atlaskin et al., 2012), and we aim to identify whether longwave radiative cooling can explain the deficiencies. In order to quantify this term, an 8 meter high tower with measurements of net longwave radiation at 5 levels have been employed at the Veenkampen (flat terrain) since October 2011 and in the BLLAST field campaign (complex terrain, Lannemezan, France, Pyrenees; http://bllast.sedoo.fr). The aims of this thesis work are: " Relative calibration of instruments. " Document typical diurnal cycle of longwave radiative cooling for Veenkampen " Document typical diurnal cycle of longwave radiative cooling for BLLAST. " Quantify relevance of longwave radiative cooling for different wind regimes. " Compare results for Veenkampen and BLLAST " Compare results with WRF weather forecast model results. References: Atlaskin E, Vihma T. 2012. Evaluation of NWP results for wintertime nocturnal boundary-layer temperatures over Europe and Finland. Q. J. R. Meteorol. Soc. DOI:10.1002/qj.1885. Steeneveld, G.J., M.J.J. Wokke, C.D. Groot Zwaaftink, S. Pijlman, B.G. Heusinkveld, A.F.G. Jacobs, and A.A.M. Holtslag (2010), Observations of the radiation divergence in the surface layer and its implication for its parameterization in numerical weather prediction models, J. Geophys. Res., 115, D06107, doi:10.1029/2009JD013074. |
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