Seasonal Evolution of the Surface Radiation Balance in the City of São Paulo

Amauri Pereira de Oliveira

Jacyra SoaresGrupo de Micrometeorologia

Departamento de Ciências Atmosféricas – IAG/USP

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).

Land use of São Paulo

SOURCE:ATLAS AMBIENTALDO MUNICÍPIO DE SÃO PAULO”

Topography of São Paulo

650

700

750

800

850

900

950

1000

1050

1100

Area = 50 km x 50 km centered at CUASO (GTOP)

Objective

• Estimate the components of radiation balance at the surface;

• Seasonal evolution of the net radiation at the surface for São Paulo city.

Part 1

Data set, sites and sensors

Data set

7 years

5 years

9 years

Localization of observations

• CUASO – IAG Micrometeorológical Plataform, University Campus “Armando Salles de Oliveira” at Butantã, at 744 m above the mean sea level (23033' S, 46043' W);

• PEFI – IAG Meteorological Station, “Parque Estadual das Fontes do Ipiranga” at “Parque do Estado”, at 780 m above the mean sea level (23039' S, 46037’ W).

Localization - Regional land use

CUASO

PEFI

20 km

Tietê river

Micrometeorological Platform - CUASO

Net radiation components Net Radiometer Kipp Zonen

Atmospheric long wave emissionPyrgeometer Eppley

PEFI

Surface Temperature

Air Temperature

Part 2

Solar radiation effects on pyrgeometer

Pyrgeometer model PIR Eppley

Schematic of wiring and connections for the Eppley PIR

cV

Manufacturer recommendation

4c

01

cDW T

s

V

s

VL

The value of s1 is provided by the manufacturer is 3.63 0.04 V W-1 m-2.

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.

Dome Effect Correction proposed by Fairall et al. (1998)

4D

4c

4c

0

1DW TTBT

s

VL

Where L1DW is the corrected value of longwave

radiation, V is the thermopile voltage, Tc and TD are,

respectively, the case and dome temperatures, s0 and B

are calibration factors which depend of the sensor direct calibration.

Sensor temperature

Problem of Fairall corrections

• Requires TC and TD measurements;

• Due to data acquisition limitations measurements of dome and case temperatures started only in October of 2003;

• Measurements of LDW started in September 1997.

Perez Allados-Arboledas (1999)

1V

I099.0LL DW

DW2DW

Where is the corrected long wave radiation L2DW is the

long wave radiation obtained using expression proposed

by manufacturer, IDW is the global solar radiation in

Wm-2 and V is the wind intensity in ms-1.

Longwave atmospheric emission

Fairall et al. (1998)Manufacturer

Perez and Allados-Arboledas (1999)

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.

PEFI representativity

Part 3

Monthly averaged Air temperature

Sea Breeze

Hourly values of Temperature

Sea Breeze

Surface longwave emission

Reflected solar radiation

Part 4

Seasonal evolution of radiation balance components

Global solar radiation ( IDW )

Reflected solar radiation ( IUP )

Top

SurfaceTemperature ( TG )

at PEFI

Surface longwave

emission ( LUP )

Seasonal Evoluation of net radiation

2 4 6 8 1 0 1 2 1 4 1 6 1 8 2 0 2 2

L o ca l tim e ( h )

1

3

5

7

9

11

Mo

nthN et rad ia tio n

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;

Acknowledgement

• CNPq and FAPESP;

• IAG/USP meteorological station at PEFI.