variavel0=<b>Amauri Pereira Oliveira</b> - apdolive@usp.br Universidade de São Paulo
<b>Jacyra Soares</b> - jacyra@model.iag.usp.br Universidade de São Paulo
<b>João Francisco Escobedo</b> - escobedo@fca.unesp.br UNESP
<b>Antonio Jaschke Machado</b> - ajmachad@model.iag.usp.br Universidade de São Paulo
<b>Georgia Codato</b> - gecodato@terra.com.br Universidade de São Paulo
<b>Emerson Galvani</b> - galvani@fca.unesp.br UNESP
<b>Abstract.</b> Seasonal variation of diurnal evolution of the global, diffuse and direct solar radiations at surface are described in details for the cities of São Paulo and Botucatu. The description is based on measurements of (i) global and diffuse solar radiation carried out in São Paulo (7.5 years) and in Botucatu (5 years). This description includes also continuous measurements of long wave downward atmospheric emission, air temperature and humidity carried in São Paulo (3.5 years). The diurnal cycle of the diffuse and direct components of solar radiation at the surface have a distinct evolution in these two cities. In July, arrives in Botucatu about 24 % more global radiation and 45 % more direct beam solar radiation than in São Paulo. The amplitude of the diurnal cycle of long wave downward atmospheric emission has maximum amplitude of 420 W m-2, in the summer around noontime, and a minimum of 300 W m-2, in the winter between 2:00 and 3:00 LT. Under clear sky conditions, simultaneous observations indicated a large contrast of long wave downward atmospheric emission, air moisture and temperature between São Paulo and Botucatu. The pollution effect combined with the distance from the Atlantic Ocean may be responsible for the discrepancy found between São Paulo and Botucatu.
<b>Keywords.</b> Solar Radiation, Atmospheric Radiation, Urban Climate, São Paulo City, Botucatu City.