Penumbra: A spatially distributed, mechanistic model for simulating ground-level incident solar energy across heterogeneous landscapes
Citation:
Halama, Jonathan J, R. Kennedy, J. Graham, Robert B Mckane, Brad L Barnhart, K. Djang, Paul B Pettus, A. Brookes, AND P. Wingo. Penumbra: A spatially distributed, mechanistic model for simulating ground-level incident solar energy across heterogeneous landscapes. PLOS ONE . Public Library of Science, San Francisco, CA, 13(12):e0206439, (2018). https://doi.org/10.1371/journal.pone.0206439
Impact/Purpose:
This is a journal article to be submitted to PLOS ONE. The journal is especially interested in interdisciplinary research, which the tool and research we present here ties into many different ecological needs. Some methods and tools exist to inform ecological models of solar energy; however, few tools exist to predict solar energy across landscapes at user defined spatial and temporal resolutions. We introduce a tool called Penumbra that simulates spatially-distributed ground-level shade and incident solar irradiance at flexible timescales by modeling local and distant topographic shading, vegetation shading, and the influence of cloud coverage. Spatially resolved inputs of a digital elevation model, normalized digital surface model, and landscape object transmittance are used to estimate spatial variations in incident solar irradiance at user-defined temporal time steps. We test Penumbra’s accuracy against several independent irradiance datasets. Penumbra is a dynamic, spatially-distributed ground-level solar incident irradiance model to be used for producing spatial data of shade percentage and irradiance. Output data is intended for estimating effects of solar energy patterns on the health and resilience of aquatic and terrestrial ecosystems. Penumbra is a novel surface irradiance model which filled an environmental modeling niche by accounting for topographical shading, object shading, and impacts of atmospheric conditions. This information will lead to more integrated modeling systems that better inform stakeholders such as: watershed councils, tribes, local, state, and federal decision makers interested in quantifying effects of land use and impacts due to local climate shifts. Penumbra can better inform models influencing future land management by making more evident the full consequential impacts of management decisions on human and natural systems.
Description:
Landscape solar energy is a significant environmental driver, yet it remains complicated to model well. Several solar radiation models simplify the complexity of light by estimating it at discrete point locations or by averaging values over larger areas. These modeling approaches may be useful in certain cases, but they are unable to provide spatially distributed and temporally dynamic representations of solar energy across entire landscapes. We created a landscape-scale ground-level shade and solar energy model called Penumbra to address this deficiency. Penumbra simulates spatially distributed ground-level shade and incident solar energy at user-defined timescales by modeling local and distant topographic shading and vegetative shading. Spatially resolved inputs of a digital elevation model, a normalized digital surface model, and landscape object transmittance are used to estimate spatial variations in solar energy at user-defined temporal timesteps. The research goals for Penumbra included: 1) simulations of spatiotemporal variations of shade and solar energy caused by both objects and topographic features, 2) minimal user burden and parameterization, 3) flexible user defined temporal parameters, and 4) flexible external model coupling. We test Penumbra’s predictive skill by comparing the model’s predictions with monitored open and forested sites, and achieve calibrated mean errors ranging from -17.3 to 148.1 μmoles/m2/s. Penumbra is a dynamic model that can produce spatial and temporal representations of shade percentage and ground-level solar energy. Outputs from Penumbra can be used with other ecological models to better understand the health and resilience of aquatic, near stream terrestrial, and upland ecosystems.
URLs/Downloads:
DOI: Penumbra: A spatially distributed, mechanistic model for simulating ground-level incident solar energy across heterogeneous landscapes