Atmospheric correction of thermal-infrared imagery of the 3-D urban environment acquired in oblique viewing geometry

F Meier,J Richters,D Scherer,A Christen

doi:10.5194/amt-4-909-2011

Abstract

Abstract. This research quantifies and discusses atmospheric effects, which alter the radiance observed by a ground-based thermal-infrared (TIR) camera. The TIR camera is mounted on a boom at a height of 125 m above ground on top of a high-rise building in the city of Berlin, Germany (52.4556° N, 13.3200° E) and observes the Earth's surface. The study shows that atmospheric correction of TIR imagery of the three-dimensional (3-D) urban environment acquired in oblique viewing geometry has to account for spatial variability of line-of-sight (LOS) geometry. We present an atmospheric correction procedure that uses these spatially distributed LOS geometry parameters, the radiative transfer model MODTRANTM5.2 and atmospheric profile data derived from meteorological measurements in the field of view (FOV) of the TIR camera. The magnitude of atmospheric effects varies during the analysed 24-hourly period (6 August 2009) and is particularly noticeable for surfaces showing a strong surface-to-air temperature difference. The differences between uncorrected and corrected TIR imagery reach up to 6.7 K at 12:00. The use of non-spatially distributed LOS parameters leads to errors of up to 3.7 K at 12:00 and up to 0.5 K at 24:00.

Highlights

Surface temperature is a key variable in the study of energy and mass exchange at the surface-atmosphere interface
The study shows that atmospheric correction of TIR imagery of the three-dimensional (3-D) urban environment acquired in oblique viewing geometry has to account for spatial variability of line-of-sight (LOS) geometry
The study shows that atmospheric correction of TIR imagery of the 3-D urban environment acquired in oblique viewing geometry has to account for spatial variability of LOS geometry

Summary

Introduction

Surface temperature is a key variable in the study of energy and mass exchange at the surface-atmosphere interface. Thermal-infrared (TIR) remote sensing approaches, which allow the derivation of surface temperatures, have been widely applied in urban climate studies (Voogt and Oke, 2003; Weng, 2009) and were part of several integrated field campaigns like BUBBLE (Rotach et al, 2005), ESCOMPOTE (Mestayer et al, 2005) and CAPITOUL (Masson et al, 2008). Ground-based TIR remote sensing approaches were part of several studies addressing the energy exchange in urban areas. In Tokyo, a TIR camera measured urban surface temperatures from the top of a high-rise building for derivation of a local-scale thermal property parameter (Sugawara et al, 2001). Further ground-based studies used TST for the assessment of thermal characteristics of various urban surfaces (Chudnovsky et al, 2004), to study spatio-temporal differences between surface and air temperature as an important boundary condition for ventilation of the urban canopy layer by buoyancy effects (Yang and Li, 2009), or to study spatiotemporal persistence of shadow effects and surface thermal admittance (Meier et al, 2010)

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