1. Seasonal Evolution of the Surface Radiation Balance in the City of São Paulo Amauri Pereira de Oliveira Jacyra Soares Grupo de Micrometeorologia Departamento de Ciências Atmosféricas – IAG/USP

2. City Climate The characterization of the climate in city is a very complex task due to the large heterogeneity of the land use and topography (Oke, 1982; Oke et al., 1999, Gambi et al., 2000).

3. Land use of São Paulo SOURCE:ATLAS AMBIENTAL DO MUNICÍPIO DE SÃO PAULO

4. Topography of São Paulo Area = 50 km x 50 km centered at CUASO (GTOP)

5. Objective Estimate the components of radiation balance at the surface; Seasonal evolution of the net radiation at the surface for São Paulo city.

6. Part 1 Data set, sites and sensors

7. Data set 7 years 5 years 9 years

8. Localization of observations CUASO – IAG Micrometeorológical Plataform, University Campus Armando Salles de Oliveira at Butantã, at 744 m above the mean sea level (23 0 33' S, 46 0 43' W); PEFI – IAG Meteorological Station, Parque Estadual das Fontes do Ipiranga at Parque do Estado, at 780 m above the mean sea level (23 0 39' S, 46 0 37 W).

9. Localization - Regional land use CUASO PEFI 20 km Tietê river

10. Micrometeorological Platform - CUASO Net radiation components Net Radiometer Kipp Zonen Atmospheric long wave emission Pyrgeometer Eppley

11. PEFI Surface Temperature Air Temperature

12. Part 2 Solar radiation effects on pyrgeometer Pyrgeometer model PIR Eppley

13. Schematic of wiring and connections for the Eppley PIR

14. Manufacturer recommendation The value of s 1 is provided by the manufacturer is 3.63 0.04 V W -1 m -2.

15. Fairall, C. W., Persson, P. O. G., Bradley, E. F., Payne, R. E. and Anderson, S. P., 1998: A New Look at Calibration and Use of Eppley Precision Infrared Radiometers. Part I: Theory and Application, Journal of Atmospheric and Oceanic Technology, 15, 1229 – 1242. According to Fairall et al (1998) the error ~ 5.5 % using manufacturer recommendation. Too much for radiation balance studies at the surface.

16. Dome Effect Correction proposed by Fairall et al. (1998) Where L 1 DW is the corrected value of longwave radiation, V is the thermopile voltage, T c and T D are, respectively, the case and dome temperatures, s 0 and B are calibration factors which depend of the sensor direct calibration.

17. Sensor temperature

18. Problem of Fairall corrections Requires T C and T D measurements; Due to data acquisition limitations measurements of dome and case temperatures started only in October of 2003; Measurements of L DW started in September 1997.

19. Perez Allados-Arboledas (1999) Where is the corrected long wave radiation L 2 DW is the long wave radiation obtained using expression proposed by manufacturer, I DW is the global solar radiation in Wm -2 and V is the wind intensity in ms -1.

20. Longwave atmospheric emission Fairall et al. (1998) Manufacturer Perez and Allados-Arboledas (1999)

21. Corrections for pyrgeometer PIR Correction proposed by Perez and Allados- Arboledas (1999) was applied to estimate the monthly averaged longwave atmospheric emission measured by the pyrgeometer PIR at CUASO using: –Diurnal evolution of monthly averaged wind speed from CETESB (Oliveira et al., 2003); –Monthly averaged values of global solar radiation measured in CUASO.

22. PEFI representativity Part 3

23. Monthly averaged Air temperature Sea Breeze

24. Hourly values of Temperature Sea Breeze

25. Surface longwave emission

26. Reflected solar radiation

27. Part 4 Seasonal evolution of radiation balance components

28. Global solar radiation ( I DW ) Reflected solar radiation ( I UP ) Top

29. Surface Temperature ( T G ) at PEFI Surface longwave emission ( L UP )

30. Seasonal Evoluation of net radiation

31. Conclusion Seasonal evolution of the monthly average hourly values of net radiation indicates: –Nighttime maximum in winter (June) of +50 W.m -2 and a nighttime minimum in summer (December) near zero; –Daytime maximum in the summer (December) of -500 W.m -2 and a daytime minimum in winter (June) of -370 W.m -2 ;

32. Acknowledgement CNPq and FAPESP; IAG/USP meteorological station at PEFI.