The 'Urban Boundary Layer' measurement campaign is proposed by Patrice Mestayer (ECN), Joël Noilhan (CNRM), Alexis Coppalle (CORIA), Jean-Pierre Lagouarde (INRA), Frédérique Saïd (LA), Sylvie Cautenet (LAMP), Philippe Drobinski (LMD), Sue Grimmond (Indiana University), Tim Oke (University of British Columbia) and co-ordinated by Patrice Mestayer et Pierre Durand. It replaces the project URBCAP Marseilles 2001.


CLU-Escompte objectives

To evaluate the urban soil models and their parameterisations of the soil-canopy-atmosphere thermodynamic interactions : LUMPS (Grimmond et Oke, 2000), TEB (Town Energy Budget, Masson, 2000) associated to ISBA (Noilhan et Planton, 1989), and SM2-U (Soil Model for Sub-Meso - Urban, Dupont et al., 2000).

To evaluate the models simulating the urban boundary layer at the meso-g and meso-d scales : MESO-NH (Masson, Noilhan, CNRM), SUBMESO (Calmet, Mestayer, ECN) and RAMS (Audiffren, Cautenet, LAMP).

To furnish the reference dynamic data for the Chemistry-Transport simulations in nested domains, from the Escompte d omain down to the sub mesoscales of the city (computations of the spatial distribution of air quality in the quarter s) : MESO-NH-C (Rosset, LA; Tulet, SCEM), SUBMESO/Transchim (Coppalle, CORIA; Chollet, LMG), RAMS (Audiffren, Cautenet, L AMP) and probably MERCURE/AZUR (Carissimo, EDF, Toupance, LISA) (to be confirmed)

? and for the model validation exercises of SATURN, the urban sub-project of EUROTRAC-2.

Planned measurements in Marseilles urban area

These measurements come in addition to the chemistry and meteorology documentation of the Escompte domain. They cover three aspects.

The three-dimensional structure of the UBL, its depth and its turbulent fluxes :

  • tethered balloon, UHF and RASS profilers at one "Reference station " located at the coast or at the built- up area boarder;
  • 1-D, 2-D or 3-D soundings with the wind Lidar LVT;
  • evolution of the wind and turbulence vertical profiles over the canopy with 2 sodars at stations North and South;
  • air plane (Merlin) flights at the UBL upper boundary.

The soil-canopy-UBL exchanges (thermal and radiative budgets and the turbulent fluxes over the canopy) :

  • 3 stations equipped with radiometers (visible and IR, incoming and outgoing), sonic anemo-thermometers, HW anemomete rs, thermocouples, Krypton hygrometers:

    - South Station in a "green" sub-urban site (Michelet - Ste Marguerite),

    - North Station in a "mixed" sub-urban site (IUT Faculty St Jérôme);

  • two scintillometers to evaluate the sensible heat flux, integrated over two 2 km paths orientated N-S and E-W over t he city centre;
  • a network of 20 automatic T/RH sensor/recorders at the ground or over buses;
  • T/RH measurements over coast-city-countryside transects with car-borne sensors.

The IR remote sensing of surface temperatures :

  • 2 portable radiometers to evaluate the temperatures of walls, roofs and artificial surfaces of the Central and North stations surroundings;
  • airborne IRT radiometry with a radiometer and an INFRAMETRICS 760 camera on board of the Merlin and Piper Aztec airc rafts during specific flights over the city;
  • thermal IR satellite imagery Meteosat and NOAA-AVHRR.

In addition, for an analyse of the urban albedo (data from AVHRR, VEGETATION, ASTER, MODIS), a photometer will measure the atmosphere optical depth during the experiment.

The "reference" station with tethered balloon and the UHF and RASS profilers, the Doppler Lidar LVT, and the energy budget "central" station are also part of the Escompte experimental set-up and therefore pertain to the two projects. The Merlin et Piper-Aztec aircrafts, with their instrumentation are also part of the Escompte set-up, exce pt the IRT camera, but specific flight hours are requested for the project UBL/CLU.

Specific analyses will be driven to establish the maps of the land uses over the Marseilles basin and region with CORINE Land Cover, and with a higher resolution over the urban area with IGN's BDTopo, the city registry, or SPOT images. BDTopo analysis with dedicated softwares will also allow to map the built-up morphology, the view factors, and the roughness parameters. A high resolution emission inventory should also be built for the sensitivity studies of the meso-d chemistry-transport simulations.

The experimental data will be collected either in the Escompte data base, or in a compatible specific data base ; in particular the various measurements of the surface temperature will be integrated in a communal Geographical Information System. The data will be used for three types of analyses, within the frameworks of the INSU-CNRS programs PATOM (urban meteorology), PNTS (Environmental urban remote sensing) and PNCA (Atmospheric pollution of the urban and suburban zones), as well as in the framework of the European program SATURN/Eurotrac-2 (model intercomparison).

The co-operative experimental project is open to all foreign research groups able to participate on their own funds, to complete the experimental set-up for documenting the urban boundary layer (contact : or ).