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Theor. Appl. Climatol. 84, 3545 (2006)DOI 10.1007/s00704-005-0142-3Centre National de Recherches Meeteeorologiques, Toulouse, FranceUrban surface modeling and the meso-scale impact of citiesV. MassonWith 2 FiguresReceived February 4, 2004; revised April 12, 2004; accepted February 5, 2005
Published online September 26, 2005 # Springer-Verlag 2005SummaryNew developments of the international community in
modeling the urban canopy surface energy balance are
presented and classified into five main categories: (i) models
statistically fit to observations, (ii) and (iii) modified vegetation schemes with or without drag terms in the canopy,
and (iv) and (v), new urban canopy schemes, that present
both horizontal and vertical surfaces, again with or without a
drag approach. The advantages and disadvantages of each
type of model are explained. In general, the more the physics are correctly simulated, the more complex are the urban
phenomenon that can be addressed, on the other hand
however, the more consuming of computer-time and difficult
to couple with atmospheric models the scheme becomes.Present use of these new models in meso-scale atmospheric models show their ability to reproduce the phenomenon of the urban heat island (UHI) and some of its
consequences urban breezes, storm initiation, interaction
with sea-breeze. Their use opens up new perspectives, for
example in the mitigation of the UHI, or assessment of the
role of air-conditioning systems or the impact of urban
dynamics on air pollution.However, there is need to validate further the different
urban models available. In particular it is necessary to compare model output with urban surface energy balance measurements. An intercomparison exercise involving these
urban schemes is suggested as an efficient way to assess
and improve these models.1. Introduction: the urban surfaceWhile cities occupy only 0.05% of the Earths
surface, more than half of the Worlds inhabitantsnow live in urban areas, and are therefore sensitive to their environmental conditions. Among
them, the cities climate is of importance, and
differs from the climate of the adjacent countryside, due to the special nature of urban areas. The
most well known atmospheric effect of towns on
the atmosphere is the urban heat island (UHI): at
night, city air is usually warmer by 310 K (Oke,
1987). This effect has economic consequences,
but also an impact on human health, as has been
shown by the excess mortality of 15,000 people