Abstract
Meteorological modelling in the planetary boundary layer (PBL) over Greater Paris is performed using the Weather Research and Forecast (WRF) numerical model. The simulated meteorological fields are evaluated by comparison with mean diurnal observational data or mean vertical profiles of temperature, wind speed, humidity and boundary-layer height from 6 to 27 May 2005. Different PBL schemes, which parametrize the atmospheric turbulence in the PBL using different turbulence closure schemes, may be used in the WRF model. The sensitivity of the results to four PBL schemes (two non-local closure schemes and two local closure schemes) is estimated. Uncertainties in the PBL schemes are compared to the influence of the urban canopy model (UCM) and the updated Coordination of Information on the Environment (CORINE) land-use data. Using the UCM and the CORINE land-use data produces more realistic modelled meteorological fields. The wind speed, which is overestimated in the simulations without the UCM, is improved below 1,000 m height. Furthermore, the modelled PBL heights during nighttime are strongly modified, with an increase that may be as high as 200 %. At night, the impact of changing the PBL scheme is lower than the impact of using the UCM and the CORINE land-use data.
Highlights
The vertical dispersion of atmospheric pollutants in the planetary boundary layer (PBL) is mostly governed by motions caused by turbulence
The Yonsei University (YSU) and the Mellor–Yamada–Nakanishi and Niino (MYNN) schemes perform better than the others
As modelled meteorological data in the PBL have previously shown to be very sensitive to the PBL scheme, simulations were performed with various PBL schemes
Summary
The vertical dispersion of atmospheric pollutants in the planetary boundary layer (PBL) is mostly governed by motions caused by turbulence. The impact of land-use data on temperature in the lower atmosphere was studied using WRF/UCM over the Phoenix metropolitan area in the U.S.A. by Grossman-Clarke et al (2010) and over northern Taiwan by Lin et al (2008). Flagg and Taylor (2011) examined the sensitivity of the surface energy balance, canopy layer and boundary-layer processes on the scale of urban surface representation They found that small changes in the scale can affect the urban fraction used in the surface representation, affecting meteorological fields (e.g., surface heat flux and skin surface temperature) in Detroit, U.S.A.–Windsor (Canada) area. This paper aims at evaluating the relative impact of the PBL scheme used in the WRF model and the use of an UCM over Greater Paris. The WRF model version 3.3 with the Advanced Research WRF (ARW) dynamics solver is used to obtain meteorological fields over Greater Paris (Skamarock et al 2008)
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