Urban-rural air temperature patterns from remotely sensed land surface temperature

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Urban-rural air temperature patterns from
remotely sensed land surface temperature

• Koen De Ridder, Bino Maiheu, VITO Flemish
  Institute for Technological Research, Mol,
  Belgium
• Enrique Montero, INDRA Espacio, Madrid, Spain
• Giulio Ceriola, Paolo Manunta, Monique Viel,
  Planetek Italia, Bari, Italy
• Iphigenia Keramitsoglou, Vassilis Amiridis, NOA
  National Observatory of Athens, Athens, Greece
• Marc Paganini, ESA-ESRIN, Frascati, Italy
• Bénédicte Dousset, University of Hawaï,
  Honolulu, Hawaï, USA
• José Sobrino, University of Valencia, Valencia,
  Spain
• Kostas Kourtidis, Democritus University of
  Thrace, Xanthi, Greece
• Xavier Briotet, ONERA, Toulouse, France

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urban heat island phenomenon impacts
health
energy consumption

• The evidence that heat waves can result in both
  increased deaths and illness is substantial, and
  concern over this issue is rising because of
  climate change

Reid CE, ONeill MS, Gronlund CJ, Brines SJ,
Brown DG, Diez-Roux AV, et al. 2009. Mapping
Community Determinants of Heat Vulnerability.
Environ Health Perspect 1171730-1736.
Sailor, D. J. 2002. Urban Heat Islands,
Opportunities and Challenges for Mitigation and
Adaptation. Sample Electric Load Data for New
Orleans, LA (NOPSI, 1995). North American Urban
Heat Island Summit. Toronto, Canada. 14 May
2002. Data courtesy Entergy Corporation.
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ESA-UHI project objectives

• demonstrate use of thermal infrared (TIR)
  satellite imagery to map urban heat island
  characteristics for ten European cities and using
  different sensors (SEVIRI, AVHRR, ASTER, )
• thermal remote sensing alone is not sufficient to
  describe the urban heat island ? need to
  determine air temperature from land surface
  temperature imagery
• this presentation focuses on
• retrieval of air temperature from ASTER TIR
  imagery
• case study for the Madrid area

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ASTER Advanced Spaceborne Thermal Emission and
Reflection Radiometer

• onboard Terra platform
• channels
• visible / near infrared
• short-wave infared
• thermal infrared
• five thermal channels
• range 8.125 11.65 µm
• spatial resolution 90 m

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land surface temperature derived from
ASTERMadrid area, 25 June 2008, 2218
UTatmospheric and surface emissivity
corrections
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method (1)

• calculate turbulent sensible heat flux H from
• vertical temperature gradient Ts-Ta
• aerodynamic resistance rah
• use H as lower boundary condition in a numerical
  advection-diffusion model, forced by ECMWF
  large-scale forcing
• update air temperature Ta using this model
• back to step 1. ?

background air temperature
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method (2)

• ASTER pixels are characterized by a single
  temperature only while they are composed of a
  mixture of land cover types (vegetation, soil,
  urban, )
• this requires the specification of aggregated
  values for
• momentum roughness length z0 (? Mason, 1988)
• thermal roughness length z0t (? Beljaars and
  Holtslag, 1991)
• specification of kB-1 ? ln(z0/z0t)
• kB-1 2 over vegetation
• over cities ? Zilitinkevich (1970)

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validation
ASTER 25 June 2008 2218 UT
ASTER 25 June 2008 1113 UT
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day versus night air temperature
sealed soil surfaces
2-m air temperature 25 June 2008 1113 UT
2-m air temperature 25 June 2008 2218 UT
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air temperature transects across Retiro Park
day
night
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conclusions

• we implemented
• an aerodynamic method to obtain sensible heat
  flux from satellite surface temperature,
• coupled to a coarse atmospheric model to estimate
  background air temperature
• validation for Madrid for a day/night image pair
  yielded
• average errors of the order of 1C
• pattern correlation coefficients ? 0.8
• it was found that
• the UHI is stronger at night than during the day
• cooling effect Retiro park ? 0.5-1.5 C
  (background temperature!)