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Surface Heat Balance Analysis by using ASTER and Formosat-2 data Soushi Kato Department of Earth Sciences, Earth Dynamic System Research Center, National.

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Presentation on theme: "Surface Heat Balance Analysis by using ASTER and Formosat-2 data Soushi Kato Department of Earth Sciences, Earth Dynamic System Research Center, National."— Presentation transcript:

1 Surface Heat Balance Analysis by using ASTER and Formosat-2 data Soushi Kato Department of Earth Sciences, Earth Dynamic System Research Center, National Cheng Kung University

2 Introduction Estimation of surface heat balance in urban area helpful to understand the causes of heat island effect Using Remote Sensing data useful to obtain spatial pattern RS data with high spatial resolution and wide spectral coverage are suitable to heat balance estimation

3 ASTER and Formosat-2 ASTER VNIR Formosat-2 False-color images around NCKU, Taiwan ( NIR, Green, Red ) Visible & NIR 4 band 8 m & 2 m resolution Visible & NIR 3 band 15m resolution SWIRTIR 6 band 5 band 30 m 90 m

4 Surface Heat Balance Surface H Anthropogenic heat Energy consumption Sensible heat Surface-atmosphere temperature difference Ground heat Surface-subsurface temperature difference RnRn LE Net radiation Short- and longwave radiation Latent heat Evapotranspiration R n + A = H + LE + G Sensible heat flux increase Heat island phenomenon A G

5 Storage Heat Flux ( G) G = G – A = R n – H – LE H RnRn LE G > 0 Heat storage G < 0 Heat discharge Combine G and A Estimated by R n, H and LE G A H RnRn LE G Based on the method for ground measurement (e.g. Oke et al., 1999) Storage heat flux Net radiation Sensible heat Latent heat Anthropogenic heat Ground heat Ground heat (G) Anthropogenic heat (A) Difficult to obtain through a wide area [W/m 2 ]

6 Net Radiation (R n ) Estimation s : Surface emissivity (absorptance) (Ogawa et al., 2003) T a : Atmospheric temperature (K) T s : Surface temperature (K) Relative humidity (%) Reflectance (Liang, 2000) R s : Solar radiation (W/m 2 ) : Albedo R L : Longwave radiation (W/m 2 ) = i T i 4 (Stefan-Boltzmanns law) a : Atmospheric emissivity (Prata, 1996) Atmospheric temperature (K) R n = (1 ) R s + s R L R L RsRs RLRL RLRL s

7 Sensible Heat Flux (H) Estimation : Air density (kg/m 3 ) C p : Specific heat of air at constant pressure (J/kg K) T s : Surface temperature (K) T a : Atmospheric temperature (K) r a : Aerodynamic resistance (s/m) Bulk resistance approach Wind speed (m/s) Roughness length (m) Surface type (Brutsaert, 1982; Kondo, 1994; Yasuda, 1995) T a T s r a T s – T a r a H = C p

8 Latent Heat Flux (LE) Estimation : Air density (kg/m 3 ) C p : Specific heat of air at constant pressure (J/kg K) e s * : Saturation vapor pressure (hPa) e a : Vapor pressure (hPa) : Psychrometric constant (hPa/k) r a : Aerodynamic resisntance (s/m) r s : Stomatal resistance (s/m) (Nishida et al., 2003) Air temperature (K) Relative humidity (%) Surface temperature (K) eaea es*es* r a r s Bulk resistance approach LE = C p e s * – e a r a + r s Air temperature (K) Solar radiation (W/m 2 ) Minimum r s (s/m) Surface type

9 Data Used false color ( NIR: Green: Red ) 0 5km Meteorological Station Study area Tainan, Taiwan Satellite data ASTER 2000 / 3 / 6 Formosat / 7 / 12 Meteorological data Tainan 2000 / 3 / 6

10 Surface Classification Map Urban Road Water Bare soil Short grass Tall grass Bush Forest Formosat-2 Derived from Maximum likelihood method and manual correction

11 Comparison of Classification Maps Formosat-2 Roads and vegetations are distinguished more clearly ASTER Surface classification map around Tainan Station 0 1km

12 W/m W/m W/m 2 Heat Fluxes by ASTER & Formosat-2 Sensible heat H Latent heat LE Storage heat G Net radiation R n W/m 2

13 Further Study Usage of ASTER and Formosat-2 data acquired on the same (at least closer) dates 2-m resolution pan-sharpened Formosat-2 image ASTER 15m Formosat-2 8m Formosat-2 2m

14 Thank you for your attention.


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