Modeling directional thermal radiance from a forest canopy

McGuire, Mike; Balick, Lee K.; Smith, James A.; Hutchison, Boyd A.

doi:10.1016/0034-4257(89)90016-3

Cited by 34 publications

(6 citation statements)

References 43 publications

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“…Off-nadir tree canopy temperature distributions show variations in the mean of approximately 3ЊC between the most directly irradiated direction and the most shaded for each flight over the R area. This is similar to the magnitude observed by Balick et al (1987), McGuire et al (1989, and Sun and Mahrt (1995).…”

Section: T C2supporting

confidence: 88%

Complete Urban Surface Temperatures

1997

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An observation program using ground and airborne thermal infrared radiometers is used to estimate the surface temperature of urban areas, taking into account the total active surface area. The authors call this the complete urban surface temperature. This temperature is not restricted by the viewing biases inherent in remote sensors used to estimate surface temperature over rough surfaces such as cities. Two methods to estimate the complete surface temperature are presented. Results for three different land-use areas in the city of Vancouver, British Columbia, Canada, show significant differences exist between the complete, nadir, and off-nadir airborne estimates of urban surface temperature during daytime. For the sites and times studied, the complete surface temperature is shown to agree with airborne off-nadir estimates of the apparent surface temperature of the most shaded walls. Some implications of using the complete surface temperature to estimate screen level air temperature and to calculate surface sensible heat flux are given.

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Section: T C2supporting

confidence: 88%

Complete Urban Surface Temperatures

1997

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“…However, in reality, effects of both canopy geometry and leaves orientation are combined. This explain why numerous modeling studies [ Kimes et al , 1981; Smith et al , 1981; Prévot , 1985; McGuire et al , 1989] are based on accurate measurements of leaves orientation and position within the canopy.…”

Section: Factors Affecting the Apparent Temperature Of Vegetation Coversmentioning

confidence: 99%

“…Radiative transfer models [ Kimes , 1980; Kimes et al , 1980; Smith et al , 1981; Prévot , 1985; McGuire et al , 1989; Olioso , 1995; François et al , 1997; Olioso et al , 1999; Luquet et al , 2001; Luquet , 2002] estimate the cover radiance as a function of sensor viewing direction, temperature distribution, and leaf angle distribution within the canopy. They simulate the propagation and the interactions within the cover of TIR radiation emitted by the cover components or incoming from the atmosphere.…”

Section: Introductionmentioning

confidence: 99%

Thermal infrared radiative transfer within three‐dimensional vegetation covers

Guillevic¹

2003

J. Geophys. Res.

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[1] The angular distribution of thermal infrared (TIR) radiation emitted by vegetation covers can vary widely depending on environmental conditions and canopy structure. As an aid in the interpretation of TIR remotely sensed data from vegetated surface with incomplete canopies, we developed a three-dimensional radiative transfer model in the thermal infrared domain. The model simulates the TIR radiative budget and upward spectral radiance of vegetation covers. The model is an extension to the TIR region of the DART (Discrete Anisotropic Radiative Transfer) model developed for the short wave domain. Radiative transfer simulation relies on discrete 3-D scene representations, which include any distribution of trees and ground covers, possibly with topography. Propagation of emitted and scattered radiation is tracked with a ray-tracing approach and the discrete ordinate method. The model was successfully tested against a physically based model for homogeneous canopies, and a partial validation was carried out with directional TIR measurements on a cotton row crop. Model simulations are presented to illustrate the influence of the canopy geometric structure on the directional apparent temperature of hypothetical vegetation covers.

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“…Effective thermal anisotropy has been observed for a variety of surfaces, namely plant canopies [9][10][11][12], forests [13][14][15], and over larger scale terrain, including the influence of orography [16][17][18][19]. The first remote sensing observations of urban surface temperature were reported by Rao [20].…”

Section: Observations Of Urban Effective Thermal Anisotropymentioning

confidence: 99%

Daytime Thermal Anisotropy of Urban Neighbourhoods: Morphological Causation

Krayenhoff

Voogt

2016

Remote Sensing

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Surface temperature is a key variable in boundary-layer meteorology and is typically acquired by remote observation of emitted thermal radiation. However, the three-dimensional structure of cities complicates matters: uneven solar heating of urban facets produces an "effective anisotropy" of surface thermal emission at the neighbourhood scale. Remotely-sensed urban surface temperature varies with sensor view angle as a consequence. The authors combine a microscale urban surface temperature model with a thermal remote sensing model to predict the effective anisotropy of simplified neighbourhood configurations. The former model provides detailed surface temperature distributions for a range of "urban" forms, and the remote sensing model computes aggregate temperatures for multiple view angles. The combined model's ability to reproduce observed anisotropy is evaluated against measurements from a neighbourhood in Vancouver, Canada. As in previous modeling studies, anisotropy is underestimated. Addition of moderate coverages of small (sub-facet scale) structure can account for much of the missing anisotropy. Subsequently, over 1900 sensitivity simulations are performed with the model combination, and the dependence of daytime effective thermal anisotropy on diurnal solar path (i.e., latitude and time of day) and blunt neighbourhood form is assessed. The range of effective anisotropy, as well as the maximum difference from nadir-observed brightness temperature, peak for moderate building-height-to-spacing ratios (H/W), and scale with canyon (between-building) area; dispersed high-rise urban forms generate maximum anisotropy. Maximum anisotropy increases with solar elevation and scales with shortwave irradiance. Moreover, it depends linearly on H/W for H/W < 1.25, with a slope that depends on maximum off-nadir sensor angle. Decreasing minimum brightness temperature is primarily responsible for this linear growth of maximum anisotropy. These results allow first order estimation of the minimum effective anisotropy magnitude of urban neighbourhoods as a function of building-height-to-spacing ratio, building plan area density, and shortwave irradiance. Finally, four "local climate zones" are simulated at two latitudes. Removal of neighbourhood street orientation regularity for these zones decreases maximum anisotropy by 3%-31%. Furthermore, thermal and radiative material properties are a weaker predictor of anisotropy than neighbourhood morphology. This study is the first systematic evaluation of effective anisotropy magnitude and causation for urban landscapes.

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Modeling directional thermal radiance from a forest canopy

Cited by 34 publications

References 43 publications

Complete Urban Surface Temperatures

Complete Urban Surface Temperatures

Thermal infrared radiative transfer within three‐dimensional vegetation covers

Daytime Thermal Anisotropy of Urban Neighbourhoods: Morphological Causation

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