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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
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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).
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Land use of São Paulo
SOURCE:ATLAS AMBIENTALDO MUNICÍPIO DE SÃO PAULO”
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Topography of São Paulo
650
700
750
800
850
900
950
1000
1050
1100
Area = 50 km x 50 km centered at CUASO (GTOP)
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Objective
• Estimate the components of radiation balance at the surface;
• Seasonal evolution of the net radiation at the surface for São Paulo city.
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Part 1
Data set, sites and sensors
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Data set
7 years
5 years
9 years
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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).
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Localization - Regional land use
CUASO
PEFI
20 km
Tietê river
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Micrometeorological Platform - CUASO
Net radiation components Net Radiometer Kipp Zonen
Atmospheric long wave emissionPyrgeometer Eppley
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PEFI
Surface Temperature
Air Temperature
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Part 2
Solar radiation effects on pyrgeometer
Pyrgeometer model PIR Eppley
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Schematic of wiring and connections for the Eppley PIR
cV
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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.
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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.
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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.
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Sensor temperature
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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.
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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.
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Longwave atmospheric emission
Fairall et al. (1998)Manufacturer
Perez and Allados-Arboledas (1999)
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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.
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PEFI representativity
Part 3
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Monthly averaged Air temperature
Sea Breeze
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Hourly values of Temperature
Sea Breeze
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Surface longwave emission
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Reflected solar radiation
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Part 4
Seasonal evolution of radiation balance components
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Global solar radiation ( IDW )
Reflected solar radiation ( IUP )
Top
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SurfaceTemperature ( TG )
at PEFI
Surface longwave
emission ( LUP )
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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
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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;
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Acknowledgement
• CNPq and FAPESP;
• IAG/USP meteorological station at PEFI.