The urban boundary-layer field campaign in marseille (ubl/clu-escompte): set-up and first results

Abstract

The UBL/CLU (urban boundary layer/couche limite urbaine) observation and modelling campaign is a side-project of the regional photochemistry campaign ESCOMPTE. UBL/CLU focuses on the dynamics and thermodynamics of the urban boundary layer of Marseille, on the Mediterranean coast of France. The objective of UBL/CLU is to document the four-dimensional structure of the urban boundary layer and its relation to the heat and moisture exchanges between the urban canopy and the atmosphere during periods of low wind conditions, from June 4 to July 16, 2001. The project took advantage of the comprehensive observational set-up of the ESCOMPTE campaign over the Berre-Marseille area, especially the ground-based remote sensing, airborne measurements, and the intensive documentation of the regional meteorology. Additional instrumentation was installed as part of UBL/CLU. Analysis objectives focus on (i) validation of several energy balance computational schemes such as LUMPS, TEB and SM2-U, (ii) ground truth and urban canopy signatures suitable for the estimation of urban albedos and aerodynamic surface temperatures from satellite data, (iii) high resolution mapping of urban land cover, land-use and aerodynamic parameters used in UBL models, and (iv) testing the ability of high resolution atmospheric models to simulate the structure of the UBL during land and sea breezes, and the related transport and diffusion of pollutants over different districts of the city. This paper presents initial results from such analyses and details of the overall experimental set-up.Ã

Modeling the energy balance in Marseille: Sensitivity to roughness length parameterizations and thermal admittance

“…This study has shown that the ARPS-LAICa model setup is able to satisfactory simulate the flux differences between urban and rural areas, especially by using the thermal roughness length parameterization of Zilitinkevich et al [1992] and a thermal admittance value m of 1206.23 J m À2 s 1/2 K À1 . Moreover, comparisons with more complex models as the TEB/ISBA scheme over the same terrain [Mestayer et al, 2005] shows that using this simple approach, same magnitude of flux errors compared to observations are obtained. Moreover, comparison to a study done by Lemonsu et al [2004] shows that our simple model setup generates results for the surface fluxes (in terms of RMSE) similar to that of TEB-ISBA using a single urban class as defined in the CORINE land cover classification (as used in this study) over Marseille.…”

“…The difference in MAE and RMSE are of the same order of magnitude, which proof that those errors in heat storage flux by using the RES method are not responsible for the variances in the sensible heat flux. Comparing these result with the more complex TEB-ISBA model setup, thereby using observed forcing to run in offline mode, results for the heat storage flux are of the same order of error magnitude with a RMSE of 66.2 and 71.1 for the complex TEB/ISBA scheme and our reference run respectively Mestayer et al, 2005].…”

“…From the observed daytime peak in latent heat flux (70 W m À2 ) the water mass flux is calculated, yielding a value of 0.028 g m À2 s À1 . Under a pressure P of 1010 h Pa and a specific humidity q of 8 g kg À1 [Mestayer et al, 2005], the vapor pressure e amounts to 13 h Pa. This results in a vapor pressure deficit (VPD) of 20 h Pa [Oke, 1987].…”

“…iiasa.ac.at/Research/TNT/WEB/heat/). Using the ration of energy from traffic from the Energy Yearly statistics from (http:// epp.eurostat.ec.europa.eu/portal/page?_pageid=1073,46587259& , and Various Urban Classes [Mestayer et al, 2005], and Results From LUMPS …”

North-western Mediterranean sea-breeze circulation in a regional climate system model

“…1). A second reason is the availability of a large measurement dataset collected in the frame of the ESCOMPTE projet in 2001 (Cros et al 2004;Mestayer et al 2005) and available for model evaluation.…”