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• Mercator (Fortaleza) 15 (3) • Jul-Sep 2016 • https://doi.org/10.4215/RM2016.1503.0006 copy

SEASONAL VARIATION OF SURFACE ENERGY BALANCE OF A CENTRAL BRAZIL CITY

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

This intense growth and populational concentration experienced by Cuiabá City since the 70's has favored to the rapid process of land cover changes on local tropical climate mainly because the replacement of preserved natural areas by building and impervious surfaces. Based on this scenario, this research aimed to evaluate the surface-atmosphere exchanges of an urban site located near downtown of Cuiaba City. In general, the fraction of flux partitioning of anthropogenic heat flux (QF), heat stored inside the urban canopy (ΔQs), latent heat fluxes (QE) and sensible heat fluxes (QH ) corresponded to 3, 26, 28 and 46 % and 3, 23, 31 and 46% of energy available in the environment (Q*+QF) , in the dry and wet season respectively. These fractions of the energy balance were similar to those observed in Miami City, but differ in terms of the timing of the peak and the intensity. The average diurnal Bowen ratios (β) in the dry and wet seasons were 1.67 and 1.55 and showed directed relation with decreasing vegetation cover area. Sensible and latent heat fluxes were positively correlated with impervious surface and vegetated area.

Key words:
Urban energy fluxes; Bowen ratio; Urban canopy

Land use and occupation	Fraction of Area (f_i = A_partial/A_{total area})
Land use and occupation	Impervious area (asphalt and concrete paving)(f_I)	Vegetated area(f_V)	Bare and partially bare soil (f_P)	Building’s roofs area(f_R)	Urban Canyon area (walls areas) (f_C)	f_S/ f_{plain area}
Site 1	21.72%	11.42%	8%	33.97%	24.88%	1.33

Surface material characteristics	Location/ Author Data	Average annual values
Surface material characteristics	Location/ Author Data	a₁ (adimensional)	a₂ (h)	a₃ (Wm^-2)
Vegetation area	Sinop Forest Data¹ 1 Coefficients determined for Sinop forest located in the Amazon-Cerrado transition zone;	0.03	-0.03	-3.30
bare soil/ partial covered soil (pasture and grass)	Miranda Farm site² 2 It was utilized average negative values of a2 e a3; (4) The a1. a2 e a3 coefficients were derived by a fluximeter installed under the concrete slab in the Site 1	0.26	-0.07	-22.75
Asphalt	Anandakumar (1999)ANANDAKUMAR, K. A study on the partition of net radiation into heat fluxes on a dry asphalt surface, Atmospheric Environment, v.33, p. 3911-3918, 1999. ³ 3 It was utilized average negative values of a2 e a3;	0.84	-0.83	-19.29
Concrete	Urban Site⁴ 4 The a1. a2 e a3 coefficients were derived by a fluximeter installed under the concrete slab in the Site 1	0.21	-0.43	-13.90
Building roof cover(ceramic roof tiles)	Meyn e Oke (2009)MEYN, S., OKE, T. R. Heat Fluxes Through Roofs and Their Relevance to Estimates of Urban Heat Storage. Energy and Building, v.41, p.745-752, 2009.	0.07	0.26	-6.0
Urban canyons	Yoshida et al. (1991)YOSHIDA, A.; TOMINAGA, K.; WATATANI, S. Field measurements on energy balance of an urban canyon in the summer season. Energy Building, v.15-16, p.417-423, 1991.	0.52	0.03	-34.0

Site	Fraction of vegetated (f_V)	Fraction of impervious surface area (f_I)	Q_E/Q^*	Q_H/(Q^*-ΔQ_s)	Q_H/Q_E
Site 1	0.15	0.74	0.30	0.64	1.61
Cuiabá 90’s (MAITELLI, 2010MAITELLI, G. T. Balanço de Energia Estimado para a Cidade de Cuiabá: Uma Abordagem de Balanço de Energia pelo Método de Bowen. Clima Urbano e Planejamento das Cidades, v.4, n.2, 2010.)	0.20	0.80	0.38	0.40	1.02
Rural site(BIUDES al al., 2009BIUDES, M. S.et all. Estimativa do balanço de energia em cambarazal e pastagem no norte do Pantanal pelo método da razão de Bowen. Revista Brasileira de Meteorologia, v. 24, n. 2, p. 135-143, 2009.)	0.95	0.05	0.57	0.30	0.62
São Paulo (FERREIRA, 2010FERREIRA, M. J. Balanço de energia na superfície da cidade de São Paulo. 2010. 183f. Tese. (Doutorado) - Departamento de Ciências Atmosféricas, IAG-USP. São Paulo. SP. Brazil, 2010.)	0.05	0.75	0.15	0.93	3.27
Miami-Florida (USA)(NEWTON et al., 2007NEWTON, T. et all. The suburban energy balance in Miami, Florida. Geogr. Ann., v. 89, p.331-347, 2007.)	0.23	0.53	0.27	0.61	1.55

	Dry season		Wet season
Period	*Diurnal (Q>0)**	*Nighttime (Q<0)**	*Diurnal (Q>0)**	*Nighttime (Q<0)**
Q^*	332	-66	300	-54
Q_F	10	4	10	4
ΔQ_s	87	-37	71	-33
Q_E	94	-20	92	-19
Q_H	158	-6	143	3
Fractions
Q_H/Q_E	1.67	0.28	1.55	-0.13
ΔQ_s /(Q^*+Q_F)	0.26	0.60	0.23	0.66
Q_E/(Q^*+Q_F)	0.28	0.33	0.31	0.39
Q_H/(Q^*+Q_F)	0.46	0.09	0.46	-0.05
Q_H/ΔQ_s	1.80	0.15	2.02	-0.08
(ΔQ_s + Q_H)/Q_E	2.60	2.09	2.31	1.56

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