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Improving satellite-based modelling of gross primary production in deciduous broadleaf forests by accounting for seasonality in light use efficiency
摘要： Vegetation gross primary production (GPP), the photosynthetic yields by green plants per unit area per unit time, is a key metric of carbon flux in understanding the land–atmosphere interactions and terrestrial carbon cycles. Satellite-based light use efficiency (LUE) models are valuable methods to retrieve large-scale terrestrial GPP using remote sensing data. As studies have reported that maximum light use efficiency, a key parameter that is often assumed to be constant in the LUE models, there is a need to explore the effects of LUE seasonality on GPP simulation and ways for correction. This study proposes a method based on leaf area index to account for LUE seasonality and applies it to four different light use efficiency models (i.e., the MOD17 algorithm, the vegetation photosynthesis model, the radiation partitioning model, and the vegetation index model) for comparisons. Based on 59 site-years flux tower data from deciduous broadleaf forest sites in the United States, the results show that all models could simulate daily GPP time series well and explain more than 85.0% variance of tower-based GPP. There is, however, a tendency to overestimate GPP during the non-growing season but underestimate GPP during the growing season. By applying the correction function, GPP simulation using the LUE models improved in all experiments as indicated by increased correlation coefficients, the index of agreement and decreased root-mean-square errors. Among all models, the radiation partitioning model achieves the highest correlation coefficients between modelled and observed daily GPP likely because it considers the influences of direct and diffuse radiation partitioning on daily canopy photosynthesis. Our study indicates that satellite-based light use efficiency models could be successfully applied for deriving daily vegetation GPP and potentially producing daily routine satellite products, while considering the effects of LUE seasonality on canopy could help improve significantly the simulation accuracy of daily GPP in phenology.
关键词： seasonality,light use efficiency,satellite-based modelling,gross primary production,deciduous broadleaf forests
更新于2025-09-23 15:21:21
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[IEEE 2019 Fourteenth International Conference on Ecological Vehicles and Renewable Energies (EVER) - Monte-Carlo, Monaco (2019.5.8-2019.5.10)] 2019 Fourteenth International Conference on Ecological Vehicles and Renewable Energies (EVER) - Modelling and Optimal Sizing of Photovoltaic Water Pumping Systems – Sensitivity Analysis
摘要： Recently we have developed a model of photovoltaic water pumping systems (PVWPS) for domestic water access in poor rural areas. In this article, we perform a sensitivity analysis over the 14 parameters of this model. We study how the variation of the parameters value influences the model output and the optimal sizing obtained from the model, for both the dry and the wet season. Results indicate that the peak power of the photovoltaic modules, the efficiency of the motor-pump and the tank volume have the highest impact on the model output. Besides, the parameters which significantly influence the optimal sizing are the position of the water entry in the tank, the position of the stop level of the float switch, the distance between the stop and restart levels of the float switch, the height between the floor and the bottom of the tank, and the static water level in the borehole. Finally, the thermal parameters of the PV modules and the hydraulic losses have a small impact on the model output and on the optimal sizing. This study can be useful to companies, governments and non-governmental organizations which install PVWPS for domestic water access. It can help them to determine the accuracy at which a given parameter has to be known to correctly model or size these systems. It can also allow them to evaluate the robustness of PVWPS sizing to parameters variation with time. Finally, it may guide the choice of components made by PVWPS installers.
关键词： Photovoltaic system,Water Pumping,Seasonality,Optimization,Sensitivity analysis
更新于2025-09-11 14:15:04