https://researchweb.iiit.ac.in/~sai.deepak/lectures/14.%20Thermal%20remote%20sensing%20of%20urban%20climates%202003%20Voogt%20and%20Oke.pdf

Thermal remote sensing of urban climates

Foliage and soil temperatures are key variables for assessing the exchanges of turbulent heat fluxes between vegetated land and the atmosphere. Using multiple-view-angle thermal-infrared (TIR) observations, the temperatures of soil and vegetation may be retrieved. However, particularly for sparsely vegetated areas, the soil and vegetation component temperatures in the sun and in the shade may be very different depending on the solar radiation, the physical properties of the surface, and the meteorological conditions. This may interfere with a correct retrieval of component temperatures, but it might also yield extra information related to canopy structure. Both are strong reasons to investigate this phenomenon in some more detail. To this end, the relationship between the TIR radiance directionality and the component temperatures has been analyzed. In this paper, we extend the four-stream radiative transfer (RT) formalism of the Scattering by Arbitrarily Inclined Leaves model family to the TIR domain. This new approach enables us to simulate the multiple scattering and emission inside a geometrically homogenous but thermodynamically heterogeneous canopy for optical as well as thermal radiation using the same modeling framework. In this way top-of-canopy thermal radiances observed under multiple viewing angles can be related to the temperatures of sunlit and shaded soil and sunlit and shaded leaves. In this paper, we describe the development of this unified optical-thermal RT theory and demonstrate its capabilities. A preliminary validation using an experimental data set collected in the Shunyi remote sensing field campaign in China is briefly addressed

Unified Optical-Thermal Four-Stream Radiative Transfer Theory for Homogeneous Vegetation Canopies

This paper describes a modified version of the Surface Energy Balance System (SEBS) as regards the use of radiometric data from space and presents the results of a large area validation study on estimated sensible heat flux, extended over several months. The improvements were made possible by the characteristics of the Along Track Scanning Radiometer (ATSR-2) on board the European Remote Sensing satellite (ERS-2) and relate to: (a) the use of bi-angular radiometric data in two thermal infrared channels to estimate column atmospheric water vapor: (b) the use of bi-angular radiometric data in four spectral channels in the 550-1600 nm spectral regions to estimate aerosols optical depth: (c) determination of bottom of atmosphere (BOA) spectral reflectance using column water vapor, aerosols optical depth and a two-stream radiative transfer scheme to relate BOA spectral reflectance to top of atmosphere spectral radiance (d) direct and inverse modeling of radiative transfer in a vegetation canopy to relate BOA spectral reflectance to canopy properties, such as spectrally integrated hemispherical reflectance (albedo). A parameterization of the aerodynamic resistance for heat transfer (in term of kB(-1)) was applied for the first time at large spatial scales. For such large area analyses SEBS requires wind speed, potential temperature and humidity of air at an appropriate reference height. The latter was taken as being the height of the planetary boundary layer (PBL) and the data used were fields generated by an advanced numerical weather prediction model, i.e. regional atmospheric climate model (RACMO), integrated over the PBL. Validation of estimated sensible heat flux H obtained with the ATSR radiometric data was done using long-range, line-averaged measurements of H done with large aperture scintillometers (LAS) located at three sites in Spain and operated continuously between April and September 1999. The root mean square deviation of SEBS H estimates from LAS H measurements was 25.5 W m(-2). (C) 2003 Elsevier Science Ltd. All rights reserved.

Estimation of sensible heat flux using the Surface Energy Balance System (SEBS) and ATSR measurements

Airborne experimental measurements of the angular variations in surface temperature over urban areas: case study of Marseille (France)

Experimental Study of Brightness Surface Temperature Angular Variations of Maritime Pine (Pinus pinaster) Stands

A steady-state thermal radiance model to compute thermal exitance and energy balance within forest canopies is described. The model treats fully leafed canopies as discrete ensembles of leaves partitioned into slope-angle and height classes. Short-wave energy flux absorbed within the canopy is estimated by solving simplified radiosity equations. Sensible heat exchange is estimated using a logarithmic wind profile above the canopy and a modified exponential profile within the canopy. The latent heat boundary layer resistance is estimated from site-specific measurements summarizing the effects of solar irradiance, air temperature, and vapor pressure deficit on stomatal conductance. Example comparisons for a dense spruce-fir forest study site in central Maine are given. For clear days the resulting root mean square error in modeled versus measured canopy temperatures was 1.2/spl deg/C. Corresponding errors in latent and sensible heat flux energy budget terms were 30 and 32 W/m/sup -2/, respectively. For partly cloudy days the root mean square error in predicted temperature was 1.0/spl deg/C and corresponding errors in latent and sensible heat were 40 and 110 W/m/sup -2/. >

S. M. Goltz

Papers

A thermal exitance and energy balance model for forest canopies

A thermal exitance and energy balance model for forest canopies