Spatial distribution in long-wave radiation flux in São Paulo City, Brazil

Abstract

The long-wave radiation (L*) in the urban canyons in São Paulo City, Brazil was observed through the use of
a Pyrgeometer PIR model (Precision Infrared Radiometer by Eppley) and a Net Radiometer LITE model (NRLITE
by Kipp & Zonen). A simple scheme to estimate the upward longwave radiation (L↑) from observations
of the net all-wave radiation (Q*) is evaluated using a 2,200 km dataset. The instruments are set up on a
mobile platform, which moves through the bottom of the canyons. The results are compared with the
observed wall surface apparent temperatures. The thermal and radiation patterns are verified along the
traverses through the different land use types in typical nocturnal and diurnal periods during the dry
season. This upward long-wave radiation parameterization is most sensitive to urban aspect ration effects
on incoming long-wave radiation (L↓). Air temperature measurements and estimates of the convective QH
flux between the atmosphere and urban buildings are also taken. For incoming long-wave radiation, even
clear sky estimates show a large degree of scatter, the results degrade as intensive vehicle traffic periods
are included.