Correlation Analysis of Urban Land Surface Temperature and Fluxes Based on Remote Sensing Technology

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1 Senor & Tranducer, Vol. 180, Iue 10, October 01, pp Senor & Tranducer 01 by IFSA Publihing, S. L. Correlation Analyi of Urban Land Surface Temperature and Fluxe Baed on Remote Sening Technology 1, Wen-Xia QIU 1 Chengdu Unierity of Technology, Chengdu, China Intitute of Engineering Sureying, Sichuan College of Architectural Technology, Deyang, China @qq.com Receied: June 01 /Accepted: 30 September 01 /Publihed: 31 October 01 Abtract: Land urface temperature and fluxe (oil heat flux, enible heat flux and latent heat flux) of the Nanchong city in Sichuan Proince on September 0, 007, were retrieed uing Landat ETM+ image. Then baed on ampling point in tudy area, urface temperature and each flux were compared with catter diagram, and imulated the function to explore their correlation. The reearch reult are the following: 1) Land urface temperature had poitiely correlation with both oil heat flux and enible heat flux, but negatiely correlation with latent heat flux. ) Surface temperature wa abolutely affected by enible heat flux. Copyright 01 IFSA Publihing, S. L. Keyword: Land urface temperature, Soil heat flux, Senible heat flux, Latent heat flux, Correlation analyi. 1. Introduction In recent year, with the deelopment of urbanization, the cale of city ha expanded continuouly, the population of which ha increaed harply, and large amount of natural urface, for example, woodland, farmland and graland, etc, hae changed into building, road, etc., which ue cement a main material, in addition a lot of heat, which i from car, computer, air conditioning, refrigerator, mobile phone, and IPAD, etc., ha dicharged into air. Thee hae caued obiou Heat Iland Effect, which i eriouly affecting city people quality of life. At preent, there are two method of urban heat iland reearch uing remote ening technology. The firt i retrieing land urface temperature, the econd i retrieing land urface fluxe. But the relationhip between urface temperature and heat fluxe ha not yet been tudied pecially. Baed on thi, taking the Nanchong city in Sichuan Proince a an example, the correlation between urface temperature and heat fluxe, which wa retrieed repectiely uing remote ening technology, wa explored to proide bai for reearch work of Urban Heat Iland.. Reearch Region and Data Source The Nanchong City lie in the northeat of Sichuan Bain, and locate in the middle reache of the Jialing Rier (ee Fig. 1). The topography i mainly hilly, and the altitude i from 6 to 80 meter. The reearch region i the urban area of the Nanchong city, which locate in the wet of the Jialing Rier and the eat of the Xi Rier, including the Shunqing Ditrict, the Jialing Ditrict and the 67

2 Senor & Tranducer, Vol. 180, Iue 10, October 01, pp Gaoping Ditrict. The Shunqing Ditrict and the Jialing Ditrict lie in the wet of the Jialing Rier, and the Gaoping Ditrict lie in the eat of the Jialing Rier. The Jialing Rier flow through the eat ide of the urban from north to outh. The urban area i urrounded by the highway. The highway from Chengdu to Nanchong run acro the outh of urban area. L Lmax L min ( Q Qmin ) L, min (1) Q Q max min where λ i the band alue, L λ i the pectral radiance by the enor (W m - r -1 μm -1 ), Q λ i the digital number of analyzed pixel, Q max i the maximum recorded (55), Q min i the minimum recorded, L max and L min are the maximum and minimum pectral radiance, detected for Q min and Q max. 3.. Radiation Calibration 1) Retrieing brightne temperature (BT). Baed on pectral radiation alue of pixel on enor, BT can be calculated directly by Planck' radiation function or an approximation Formula () [-3]. T=K /ln(1+k 1 /L λ ), () where T i the BT of pixel and it unit i K, K 1 and K are the pre-launch calibration contant, a for ETM+ band6, K 1 i W m - ter -1 μm -1, and K i K. ) Retrieing land urface temperature (LST). LST can be calculated according to Formula (3) []. Trad T ( T / ) ln, (3) 1 rad Fig. 1. General ituation of reearch region. Thi reearch ued Landat-7 ETM+ data obtained on September 0, 007, DEM and atmophere temperature. The projection of the ETM+ image wa UTM 8N, the ellipoid and reduced plane of which wa WGS8, the patial reolution of which wa 30 m. The quality of image wa good. DEM wa downloaded from Global Mapper, and it projection and reolution wa ame a ETM+ image. 3. Retrieing Land Surface Temperature 3.1. Radiation Calibration Radiation calibration i a proce of conerting the digital alue of remote ening data into pectral radiance alue of enor. The model i Formula (1) [1]. where T i the LST and it unit i K; T rad i the BT; λ i the center waelength (11. μm); h c /, where h i the Planck contant ( J ), c i the elocity of light 8 ( m / ), i the Boltzmann contant 3 ( J / K ); ε i the urface emiiity, when NDVI<0.05, ε=0.973, when NDVI>0.7, ε=0.99, when 0.05 NDVI 0.7, 0.00P , where P i the egetation proportion in pixel, P NDVI NDVI ) /( NDVI NDVI ), ( NDVI ( 3) /( 3), 3 and are the urface reflectance acquired in the iible (red) and near-infrared band, repectiely [5-6]. NDVI (0.7) and NDVI (0.05) tand for the NDVI alue of egetation and bare land.. Retrieing Land Surface Fluxe Thi reearch i mainly baed on the urface energy balance Equation () [7]. R n LE H G PH, () 68

3 Senor & Tranducer, Vol. 180, Iue 10, October 01, pp where R n i the net radiation, LE i the latent heat flux, H i the enible heat flux, G i the oil heat flux, and the unit i w / m. PH i the energy for plant photoynthei and bioma increaed, and can be neglected in actual calculation becaue it alue i ery mall. formula. In thi paper, the oil heat flux i calculated baed on the Formula (6) [1] propoed by Batiaanen in 000. G Rn T ( ), (6) (1 0.98NDVI ) / where R n i the urface net radiation, T S i the urface temperature, i the urface albedo. 3) Etimating enible heat flux (H). The enible heat flux i the exchange energy between land urface and atmophere, and i determined by the urface temperature, are temperature and air reitance. The model i Formula (7) [1]. H C dt air p, r ah (7) 5.6 ( T Z) / T T, (8) air / 3 where air i the air denity ( kg m ), and i calculated by Formula (8) [13-1], C p i the air 1 1 pecific heat at contant preure ( 100J kg K ), Fig.. Land urface temperature ditribution on September 0, ) Etimating urface net radiation (Rn). The urface net radiation (Rn) i obtained according to the Formula (5) [8]. R n Q, (5) ( 1 ) T T where Q i the total olar radiation, Q Gd w co, G i the olar contant ( 1367w / m ), d i the unearth ditance, i the zenith angle, 90, i the olar eleation, i the urface albedo,.356r (1) 0.130R (3) 0.373R () 0.085R 0 (5) 0.07R (7) [9], R (i) i the band urface reflectance, i the Stefan-Boltzmann 8 contant, and it alue i W m K, T i the atmopheric long wae radiation, i the atmopheric emiiity, ( ln w) [10] w i the atmopheric 5 tranmittance, w Z [11], T i the urface long wae radiation, i the urface emiiity, T i the near urface air temperature, T i the land urface temperature, Z i the altitude at the meaurement point and it alue i from DEM. ) Etimating oil heat flux (G). The oil heat flux i the heat tored in the oil layer, and often etimated uing the empirical dt i the temperature difference at the height of Z 1 and Z, Z 1 (0.01 m) i the bare land roughne length, Z (m) i the reference height of meteorological data, dt a( T Z ) b, a and b are contant, and their alue are obtained by electing the cold point and hot point from remote ening image; r ah i the corrected aerodynamic reitance, untable, and can be calculated through multiple recurie calculation. ) Etimating Latent heat flux (LE). The latent heat flux i the heat energy of eaporation or condenation water, can be calculated by the urface heat balance Equation (9). LE Rn H G (9) 5. Correlation Analyi of Land Surface Temperature and Fluxe To analyze the correlation between urface temperature and heat fluxe, 163 ampling point were uniformly elected in tudy area. Then, the alue of land urface temperature, oil heat flux, enible heat flux, and latent heat flux of ampling point were obtained through patial analyi between ampling point data and urface temperature, oil heat flux, enible heat flux, latent heat flux, repectiely. Finally, urface temperature and oil heat flux, enible heat flux, latent heat flux of each ampling point were compared with catter diagram repectiely, and leat quare method wa ued to imulate the function (Fig. ~6). 69

4 Senor & Tranducer, Vol. 180, Iue 10, October 01, pp Land urface temperature(k) 30 y = 0.005x x Soil heat flux (G)(W/ ) Fig.. Correlation diagram between land urface temperature and oil heat flux. a) Soil heat flux (G) Land urface temperature(k) y = 0.169x Senible heat flux (H)(W/ ) Fig. 5. Correlation diagram between land urface temperature and enible heat flux. Land urface temperature(k) 30 y = x x Latent heat flux (LE) (W/ ) b) Senible heat flux (H) Fig. 6. Correlation diagram between land urface temperature and latent heat flux. c) Latent heat flux (LE) Fig. 3. Land urface heat fluxe ditribution on September 0, 007. The analyi reult howed that, 1) Land urface temperature (y) and oil heat flux (x) wa poitiely related, the fitting relationhip: y=0.005x x+35.88, and the correlation coefficient wa All data ditributed in the right part of the function ymmetry axi, o land urface temperature wa increaed moothly with increaing oil heat flux. ) Land urface temperature (y) had abolutely linear poitie correlation with enible heat flux (x), the fit function wa: y = 0.169x , and the correlation coefficient wa 1. So land urface temperature wa increaed linearly with increaing enible heat flux. 3) Land urface temperature (y) wa negatiely correlated with latent heat flux (x), the fit function wa y= x x+86.85, and the correlation coefficient wa All data ditributed in the right part of the function ymmetry axi, o land urface temperature wa decreaed moothly with increaing latent heat flux. 70

5 Senor & Tranducer, Vol. 180, Iue 10, October 01, pp Concluion and Dicuion The Nanchong city in Sichuan Proince wa taken a an example, the correlation between land urface temperature and heat fluxe were reearched. The main concluion are the following: 1) Land urface temperature had poitiely correlation with both oil heat flux and enible heat flux, but negatiely correlation with latent heat flux. ) Land Surface temperature wa abolutely effected by enible heat flux. 3) Influence mechanim of heat iland effect i that the imperiou urface area ha higher oil heat flux, lower latent heat flux, becaue it cut off the oil-atmophere heat exchange, it eapotranpiration i mall, energy coneration ability i weak, peed of aborbing or releaing energy i high, and higher enible heat flux, becaue it roughne i lower, and it albedo i higher, mot of olar radiation i reflected to the atmophere, more heat in life i dicharged in addition, and conerely, the natural urface or egetation coer area ha lower oil heat flux, higher latent heat flux, and lower enible heat flux. So the land urface temperature of imperiou urface area i higher, which of natural urface or egetation coer area i lower. Acknowledgement Thi work wa upported in part wa upported by the open foundation of the Laboratory of Geopecial Information Technology Minitry of Land and Reource, Chengdu Unierity of Technology China (No. KLGSIT013-10), and by the reearch project of Sichuan College of Architecture Technology (011) and by Key Project of Education Department of Sichuan Proince under Grant 1ZA55 and by The key cience and technology project of the Deyang City (No. 013ZZ07-05). Reference [1]. Xu Hanqiu, Image-baed Normalization Technique Ued for Landat TM/ETM+ Imagery, Geomatic and Information Science of Wuhan Unierity, Vol. 3, No. 1, 007, pp []. Gyaneh Chander and Brian Markham, Reied Landat-5 TM Radiometric Calibration Procedure and Pot-calibration Dynamic Range, IEEE Tranaction on Geocience and Remote Sening, Vol. 1, No. 11, Noember, 003. [3]. J. F. Mutard, M. A. Camey, A. Sen, The ue of atellite data to quantify thermal effluent impact, Etuarine Coatal and Shelf Science, 9, 1999, pp []. Arti D. A., Carnahan W. H., Surey of emiiity ariability in thermography of urban area, Remote Sening of Enironment, Vol. 1, No., 198, p [5]. Goward S. N., Markham B., Dye D. G., Dulaney W., Yang J., Normalized difference egetation index meaurement from the adanced ery high reolution radiometer, Remote Sening of Enironment, Vol. 35, 1991, pp [6]. Santo P., Negri A. J., A comparion of the normalized difference egetation index and rainfall for the Amazon and Northeatern Brazil, Journal of Applied Meteorology and Climatology, Vol. 36, 1997, pp [7]. Zhao Yinghi, Analyi theory and method of remote ening application, Science Pre, Beijing, 003. [8]. Liebe H. J., Hufford G. A., Cotton M. C., Propagation Modeling of Moit air and upended water/ice particle at frequencie below 1000 GHz, in Proceeding of the AGARD 5 nd Special Meeting of the Electromagnetic Wae Propagation Pand, Vol , pp [9]. Liang Shunlin, Narrowband to broadband conerion of land urface albedo I algorithm, Remote Sening of Enironment, Vol. 76, 000, pp [10]. Batiaanen W. G. M, Menenti M., Fedde R. A., et al., A remote ening urface energy balance algorithm for land (SEBAL) formulation, Journal of Hydrology, 1998, pp [11]. Taumi M., Allen R. G., Application of the SEBAL methodology for etimating conumptie ue of water and tream flow depletion in the Bear Rier Bain of L daho through remote ening, Final Report Submitted to the Raytheon Sytem Company, Earth Oberation Sytem Data and Information Sytem Project, 000. [1]. Batiaaneen W. G. M., SEBAL-baed enible and latent heat fluxe in the irrigated Gediz Bain, Journal of Hydrology, Turkey, Vol. 9, 000, pp [13]. Burman R. D., Jenen M. E., Allen R. G., Thermodynamic factor in eapotranpiration, in Proceeding of the Irrigation Sytem for the 1t Century Conference, 1987, pp [1]. Smith M., Allen R. G., Monteith J. L., et al., Report on the expert conultation on procedure for reiion of FAO guideline for prediction of crop water requirement, Land and Water Deelopment Diiion, United Nation Food and Agriculture Serice, Rome, Italy, Copyright, International Frequency Senor Aociation (IFSA) Publihing, S. L. All right reered. ( 71