Interactions of an urban heat island and sea-breeze circulations during winter over the metropolitan area of São Paulo,Brazil |
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Authors: | Edmilson D Freitas Christopher M Rozoff William R Cotton Pedro L Silva Dias |
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Institution: | 1.Departamento de Ciências Atmosféricas, Instituto de Astronomia, Geofísica e Ciências Atmosféricas,Universidade de S?o Paulo,S?o Paulo, S.P.,Brazil;2.Department of Atmospheric Science,Colorado State University,Fort Collins,USA |
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Abstract: | The Town Energy Budget (TEB) model, a detailed urban parameterisation using a generalised canyon geometry, coupled with the
Regional Atmospheric Modelling System (RAMS) is used to simulate the wintertime local circulation in the megacity environment
of the metropolitan area of Sao Paulo (MASP) in Brazil. Model simulations are performed using actual topography and land-use
fields. Comparison with a simple urban parameterisation based on the LEAF-2 scheme is also shown. Validation is based on comparison
between model simulations and observations. Sensitivity tests with TEB reveal an important interaction between the sea breeze
and the MASP heat island circulation. Even though topography is known to play an important role in the MASP region’s weather,
in these tests the simulations were performed without topography in order to unambiguously identify the interaction between
the two local circulations. The urban heat island (UHI) forms a strong convergence zone in the centre of the city and thereby
accelerates the sea-breeze front toward the centre of the city. The presence of the urban region increases the sea-breeze
front propagation mean speed by about 0.32 m s−1 when compared with the situation of no city. After its arrival in the urban region, the sea-breeze front stalls over the
centre of the city for about 2 h. Subsequently, the sea breeze progresses beyond the city when the heat island dissipates.
Thereafter, the sea breeze propagates beyond the urban area at a decelerated rate compared to a simulation without an UHI. |
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Keywords: | RAMS Sea breeze Surface scheme Urban heat island |
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