Mauricio Jonas Ferreira

Radiation balance at the surface in the city of São Paulo, Brazil: diurnal and seasonal variations

The main goal of this work is to describe the diurnal and seasonal variations of the radiation balance components at the surface in the city of São Paulo based on observations carried out during 2004. Monthly average hourly values indicate that the amplitudes of the diurnal cycles of net radiation (Q*), downwelling and upwelling shortwave radiation (SWDW, SWUP), and longwave radiations (LWDW, LWUP) in February were, respectively, 37%, 14%, 19%, 11%, and 5% larger than they were in August. The monthly average daily values indicate a variation of 60% for Q*, with a minimum in June and a maximum in December; 45% for SWDW, with a minimum in May and a maximum in September; 50% for SWUP, with a minimum in June and a maximum in September; 13% for LWDW, with a minimum in July and a maximum in January; and 9% for LWUP, with a minimum in July and a maximum in February. It was verified that the atmospheric broadband transmissivity varied from 0.36 to 0.57; the effective albedo of the surface varied from 0.08 to 0.10; and the atmospheric effective emissivity varied from 0.79 to 0.92. The surface effective emissivity remained approximately constant and equal to 0.96. The albedo and surface effective emissivity for São Paulo agreed with those reported for urban areas in Europe and North America cities. This indicates that material and geometric effects on albedo and surface emissivity in São Paulo are similar to ones observed in typical middle latitudes cities. On the other hand, it was found that São Paulo city induces an urban heat island with daytime maximum intensity varying from 2.6°C in July (16:00 LT) to 5.5°C in September (15:00 LT). The analysis of the radiometric properties carried out here indicate that this daytime maximum is a primary response to the seasonal variation of daily values of net solar radiation at the surface.

DIURNAL AND SEASONAL VARIATION OF SURFACE SENSIBLE AND LATENT HEAT FLUXES IN THE CITY OF SÃO PAULO

Resumo Nesse trabalho e apresentada a variacao diurna e sazonal dos fluxos verticais turbulentos de calor sensivel e latente na superficie representativa de uma area suburbana da Regiao Metropolitana da Cidade de Sao Paulo (RMSP). Os valores horarios medios mensais dos fluxos turbulentos de calor sensivel e latente foram determinados pelo metodo empirico do balanco de energia utilizando como referencia valores horarios medios de temperatura e radiacao liquida observados na plataforma micrometeorologica do IAG da USP durante 2009. Medidas simultâneas de turbulencia realizadas em maio e junho de 2009 com um anemometro sonico CSAT3 da Campbell e analisador de gas da LICOR permitiram estimar atraves do metodo da “eddy correlation” os fluxos de calor sensivel e latente utilizados como referencia na calibracao do metodo do balanco de energia.

ESTUDO NUMÉRICO DO BALANÇO DE RADIAÇÃO NA SUPERFÍCIE: VARIAÇÃO DIURNA E ANUAL DO ALBEDO NA CIDADE DE SÃO PAULO

A solar radiation balance at the surface scheme proposed byMartilli is applied to investigate the diurnal and seasonal evolutions ofalbedo in City of Sao Paulo. Comparisons with observational data arediscussed.

Downward Atmospheric Longwave Radiation in the City of São Paulo

This work evaluates objectively the consistency and quality of a 9 year dataset based on 5 minute average values of downward longwave atmospheric (LW) emission, shortwave radiation, temperature and relative humidity. All these parameters were observed simultaneously and continuously from 1997 to 2006 in the IAG micrometeorological platform, located at the top of the IAG‐USP building. The pyrgeometer dome emission effect was removed using neural network technique reducing the downward long wave atmospheric emission error to 3.5%. The comparison, between the monthly average values of LW emission observed in Sao Paulo and satellite estimates from SRB‐NASA project, indicated a very good agreement. Furthermore, this work investigates the performance of 10 empirical expressions to estimate the LW emission at the surface. The comparison between the models indicates that Brunt’s one presents the better results, with smallest “MBE,” “RMSE” and biggest “d” index of agreement, therefore Brunt is the most indicated m...

ESTUDO DA CLP URBANA POR MEIO DE UM MODELO DE FECHAMENTO DE SEGUNDA ORDEM UNIDIMENSIONAL

Um modelo de fechamento de segunda ordem (MFSO) acopladoa um modelo de dossel urbano (MDU) e utilizado para estudar o papel daocupacao do solo de uma regiao urbana sobre o balanco de energia na superficiee sobre a estrutura vertical da camada limite planetaria (CLP). Emtodos os casos o dossel e considerado homogeneo e sem topografia. Aevolucao temporal da altura da CLP e da temperatura na superficie e osperfis verticais de temperatura potencial e energia cinetica turbulenta (ECT)sao discutidos.