Urban Soil-Canopy-Atmosphere Exchanges at Submesoscales: Learning from Model Development, Evaluation, and Coupling with LES - Meteorological and Air Quality Models for Urban Areas - page 39

Chapter 6
Urban Soil-Canopy-Atmosphere Exchanges
at Submesoscales: Learning from Model
Development, Evaluation, and Coupling
with LES

Isabelle Calmet and Patrice Mestayer

Abstract The Soil Model for Sub-Mesoscales Urban version (SM2U) can be used
as a stand-alone urban climatology model or as a boundary conditioning model
in atmospheric codes. It is presented here by pointing out the specific parameter-
izations which make it differ from classical surface energy budget models. This
paper relates the experience gained by performing validation exercises in docu-
mented meteorological situations for both the hydric and the thermal parts of the
model, and sensitivity studies aimed at disclosing the relative efficiency of the dif-
ferent parameterizations (wall conduction, radiative trapping ). The SM2U model

is then shown a very useful tool for small-scale climatology mainly due to the cou-
pled computation of water and energy budgets. The atmospheric response to the
SM2U ground forcing is also evaluated when coupled with a LES model, for differ-
ent description modes of a coastal city. The heterogeneity of the districts and a fine
description of the city are shown very important in the realistic assessment of the
atmospheric lower layers, even in very complex situations including orography and
sea influences.

...

6.1 Introduction

The Soil Model for Sub-Mesoscales Urban version (SM2U) has been developed as a
surface flux processor for high resolution atmospheric boundary layer (ABL) model
simulations over urbanized areas, and as a stand-alone model to simulate canopy
exchanges at spatial resolutions ranging from 100 to 1000 m. The initial of the
force-restore mesoscale two-layer soil model developed from Noilhan and Planton
(1989) ISBA model for partially vegetated natural soils skeleton is Pleim and Xiu's
(1995) version. A third reservoir layer (Noilhan and Mahfouf, 1996) is included in
the model which computes in parallel the surface temperature and specific humidity