Numerical study of urban mesoscale effects on the atmospheric boundary layer

Urban boundary layers effects are simulated numerically with the MESO-NH atmospheric model, coupled with the TEB (Town Energy Budget) surface scheme -for urban areas- and the ISBA surface scheme -for surroundings vegetated areas. The area under study is Paris.

The agglomeration influence is examinated through several cases of heat island effect (both in winter or summmer), and fog cases. The results are compared to the operational surface network observations, and available radiosoundings.

The ability of the MESO-NH model to retrieve these heat island effects is discussed. Then, the intensity of the induced phenomena (such as the urban breeze circulation intensity and boundary layer height) is studied.

Finally, sensitivity experiments are presented to evaluate the relative importance of urbanization and (relatively flat) orography in the Paris area on the Boundary Layer structures.