Effects of Explicit Urban-Canopy Representation on Local Circulations Above a Tropical Mega-City |
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| Authors: | José L Flores Rojas Augusto J Pereira Filho Hugo A Karam Felipe Vemado Valéry Masson |
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| Institution: | 1.USP/IAG/DCA,Universidade de S?o Paulo, S?o Paulo,S?o Paulo,Brazil;2.UFRJ/IGEO/CCMN,Universidade Federal de Rio de Janeiro, Rio de Janeiro,Cidade Universitária - Ilha do Fund?o Rio de Janeiro,Brazil;3.Centre National de Recherches Météorologiques,Météo-France/CNRS,Toulouse,France |
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| Abstract: | The Advanced Regional Prediction System (ARPS) is coupled with the tropical town energy budget (tTEB) scheme to analyze the effects of the urban canopy circulation over the metropolitan area of São Paulo and its interactions with the sea breeze and mountain-valley circulation in the eastern state of São Paulo, Brazil. Two experiments are carried out for the typical sea-breeze event occurring on 22 August 2014 under weak synoptic forcing and clear-sky conditions: (a) a control run with the default semi-desert surface parametrization and; (b) a tTEB run for the urban canopy of São Paulo. A realistic land-use database over the south-eastern domain of Brazil is used in the downscaling simulation to a horizontal grid resolution of 3 km. Our results indicate that ARPS effectively simulates features of the nighttime and early morning land-breeze circulation, which is affected by the surrounding hills and the nocturnal heat island of São Paulo. By early afternoon, the south-eastern sea-breeze circulation moves inland perpendicular to the upslope of the Serra do Mar scarp, which generates a line of moisture convergence and updrafts further inland. Later, the convergence line reaches São Paulo and interacts with the circulation arising from the urban heat island (UHI), which increases the moisture convergence and strength of updrafts. The surface energy balance indicates that the UHI is caused by large sensible heat storage within the urban canopy during the day, which is later released in the afternoon and at night. The simulations are verified with available radiosonde and surface weather station data, land-surface-temperature estimates from the moderate resolution imaging spectroradiometer, as well as the National Center for Atmospheric Research reanalysis databases. The three-dimensional geometry of the urban canyons within the tTEB scheme consistently improves the thermodynamically-induced circulation over São Paulo. |
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