A faster solution to the horizon problem

Dozier, Jeff; Bruno, John; Downey, Peter

doi:10.1016/0098-3004(81)90026-1

Cited by 126 publications

(74 citation statements)

References 9 publications

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“…The solar radiation incident to the surface is also affected by variations in slope and aspect of the topography and by local terrain shadowing surrounding terrain (Dozier et al, 1981). This shading changes with time of day, time of year, and latitude.…”

Section: Shadowsmentioning

confidence: 99%

“…Terrain slope and aspect have been identified throughout the literature as large contributors to this spatial variability (Carey and Woo, 1998;Dozier et al, 1981;Pomeroy et al, 2003;Ryerson, 1984;Woo and Young, 2004). In a catchment in the Yukon, Canada, Pomeroy et al (2003) found that on a clear day at midday in the peak snowmelt period, a 20 • south-facing slope received 80% more incoming solar shortwave radiation than a similarly steep, north-facing slope.…”

Section: Overviewmentioning

confidence: 99%

“…Examples of horizon-based algorithms are those of Fu and Rich (1999) that are incorporated into the ArcGIS R product by Environmental Systems Research Institute (ESRI) under the name SolarAnalyst, as well as those of Dozier et al (1981), Dozier andFrew (1990), Frew (1990), and Varley et al (1996). Other algorithms are less common but still used, such as via ray-tracing (Coquillart and Gangnet, 1984) or a sector/hull approach (Stewart, 1998).…”

Section: Shadowsmentioning

confidence: 99%

“…It is also necessary to calculate the shortwave radiation that is incident on slopes of various angles and aspects by taking into account selfshading and shading from surrounding topography. The basic geometric equations for estimating shortwave radiation to a slope are well known and have been applied for many years, e.g., Garnier and Ohmura (1968); Dozier et al (1981); Dozier and Frew (1990); Frew (1990); Fu and Rich (1999); Chueca and Julián (2004). However for an algorithm to be widely applicable it must be computationally efficient.…”

Section: Introductionmentioning

confidence: 99%

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Implications of mountain shading on calculating energy for snowmelt using unstructured triangular meshes

Marsh

Pomeroy

Spiteri

2012

Hydrological Processes

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In many parts of the world, the snowmelt energy balance is dominated by net solar shortwave radiation. This is the case in the Canadian Rocky Mountains, where clear skies dominate the winter and spring. In mountainous regions, solar irradiance at the snow surface is not only affected by solar angles, atmospheric transmittance, and the slope and aspect of immediate topography, but also by shadows from surrounding terrain. Many hydrological models do not consider such horizon-shadows. The accumulation of errors in estimating solar irradiance by neglecting horizon-shadows can lead to significant errors in calculating the timing and rate of snowmelt due to the seasonal storage of internal energy in the snowpack.A common approach to representing the landscape is through structured meshes. iii

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Section: Shadowsmentioning

confidence: 99%

Section: Overviewmentioning

confidence: 99%

Section: Shadowsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Implications of mountain shading on calculating energy for snowmelt using unstructured triangular meshes

Marsh

Pomeroy

Spiteri

2012

Hydrological Processes

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“…For the purpose of computing the plane that represents the terrain at each point, a classical approach based on the eight adjacent cells is used (Burrough and McDonnell, 1998, p. 190); the plain serves to compute the normal to the surface (needed for computing incident angles) as well as to know where self-shadows exist (incident angles ≥ 180°). Methods for computing cast-shadowing are derived from Dozier et al (1981).…”

Section: Topographymentioning

confidence: 99%

Mapping a topographic global solar radiation model implemented in a GIS and refined with ground data

Pons

Ninyerola

2008

Intl Journal of Climatology

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This study proposes a methodology to compute solar radiation values on the Earth surface on a monthly and annual basis and taking into account the relief, which is not an usual approach although it has enormous importance for environmental studies. It consists of two steps: a computational, physically-based model (potential solar radiation) and a refining through meteorological data (interpolated solar radiation). The potential solar radiation model allows computing the incident energy assuming uniform atmospheric standard optical density. The only information required is a Digital Elevation Model (DEM, 180 m resolution in our case) and a number of meteorological stations providing global solar radiation data (74 in our case). This model, implemented into the MiraMon Geographic Information System (GIS), takes into account astronomical, atmospheric and geographical factors. Atmospheric effects are considered through correctors obtained by comparing the potential values with the observed at the meteorological stations. The resulting monthly correctors have been spatially interpolated to build up anomaly maps, which allow to obtain a refined solar radiation cartography. The potential model has proven to be very precise as it gives results close to the interpolated radiation values, allowing a conversion to interpolated solar radiation maps with errors of 7.3% (March), 6.1% (June), 6.4% (September) and 13.1% (December) computed from a leave-one-out cross-validation. These results are always better than those obtained by classical interpolators, and still better if the process is run on the rugged terrain areas. A sensitivity analysis estimates the influence of the DEM quality on the model, concluding that an RMS error of 8 m in the DEM heights represents an RMS error of 133 kJ·m −2 ·day −1 (mean monthly) on the results. Finally, we have applied the model to obtain the 12-monthly (based on daily average) global solar radiation maps of Catalonia (NE of Iberian Peninsula) as well as the annual one.

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Modelling runoff using optical satellite remote sensing data in a high mountainous alpine catchment of Italy

Swamy

Brivio

1997

Hydrol. Process.

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Development of hydrological models for seasonal and real-time runo forecast in rivers of high alpine catchments is useful for management of water resources. The conceptual models for this purpose are based on a temperature index and/ or energy budget and can be either lumped or distributed over the catchment area. Remote sensing satellite data are most useful to acquire near real-time geophysical parameters in order to input to the distributed forecasting models. In the present study, integration of optical satellite remote sensing-derived information was made with ground meteorological and hydrological data, and predetermined catchment morphological parameters, to study the feasibility of application of a distributed temperature index snowmelt runo model to one of the high mountainous catchments in the Italian Alps, known as Cordevole River Basin. Five sets of Landsat Multispectral Scanning System (MSS) and Thematic Mapper (TM) computer-compatible tapes (CCTs) were processed using digital image processing techniques in order to evaluate the snow cover variation quantitatively. Digital elevation model, slope and aspect parameters were developed and used during satellite data processing. The satellite scenes were classi®ed as snow, snow under transition and snow free areas. A second-order polynomial ®t has been attempted to approximate the snow depletion and to estimate daily snow cover areal extent for three elevation zones of the catchment separately. Model performance evaluation based on correlation coecient, Nash±Sutclie coecient and percentage volume deviation indicated very good simulation between measured and computed discharges for the entire snowmelt period. The use of average temperature values computed from the maximum and minimum temperatures into the model was studied and a suitable algorithm was proposed.

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A faster solution to the horizon problem

Cited by 126 publications

References 9 publications

Implications of mountain shading on calculating energy for snowmelt using unstructured triangular meshes

Implications of mountain shading on calculating energy for snowmelt using unstructured triangular meshes

Mapping a topographic global solar radiation model implemented in a GIS and refined with ground data

Modelling runoff using optical satellite remote sensing data in a high mountainous alpine catchment of Italy

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