Advanced methods for uncertainty assessment and global sensitivity analysis of an Eulerian atmospheric chemistry transport model

Atmospheric chemistry and physics

Reis, Stefan^2,3¹  Aleksankina, Ksenia^1,2²  Vieno, Massimo^2³ 

[1]NERC Centre for EcologyHydrology, Penicuik, UK^2

[2]School of Chemistry, University of Edinburgh, Edinburgh, UK^1

[3]University of Exeter Medical School, European Centre for Environment and Health, Knowledge Spa, Truro, UK^3

DOI  :  10.5194/acp-19-2881-2019

学科分类：大气科学

来源: Copernicus Publications

【 摘 要 】

Atmospheric chemistry transport models (ACTMs) are extensively used to provide scientific support for the development of policies to mitigate the detrimental effects of air pollution on human health and ecosystems. Therefore, it is essential to quantitatively assess the level of model uncertainty and to identify the model input parameters that contribute the most to the uncertainty. For complex process-based models, such as ACTMs, uncertainty and global sensitivity analyses are still challenging and are often limited by computational constraints due to the requirement of a large number of model runs. In this work, we demonstrate an emulator-based approach to uncertainty quantification and variance-based sensitivity analysis for the EMEP4UK model (regional application of the European Monitoring and Evaluation Programme Meteorological Synthesizing Centre-West). A separate Gaussian process emulator was used to estimate model predictions at unsampled points in the space of the uncertain model inputs for every modelled grid cell. The training points for the emulator were chosen using an optimised Latin hypercube sampling design. The uncertainties in surface concentrations of O₃ , NO₂ , and PM _2.5 were propagated from the uncertainties in the anthropogenic emissions of NO_x , SO₂ , NH₃ , VOC, and primary PM _2.5 reported by the UK National Atmospheric Emissions Inventory. The results of the EMEP4UK uncertainty analysis for the annually averaged model predictions indicate that modelled surface concentrations of O₃ , NO₂ , and PM _2.5 have the highest level of uncertainty in the grid cells comprising urban areas (up to ±7 %, ±9 %, and ±9 %, respectively). The uncertainty in the surface concentrations of O₃ and NO₂ were dominated by uncertainties in NO_x emissions combined from non-dominant sectors (i.e. all sectors excluding energy production and road transport) and shipping emissions. Additionally, uncertainty in O₃ was driven by uncertainty in VOC emissions combined from sectors excluding solvent use. Uncertainties in the modelled PM _2.5 concentrations were mainly driven by uncertainties in primary PM _2.5 emissions and NH₃ emissions from the agricultural sector. Uncertainty and sensitivity analyses were also performed for five selected grid cells for monthly averaged model predictions to illustrate the seasonal change in the magnitude of uncertainty and change in the contribution of different model inputs to the overall uncertainty. Our study demonstrates the viability of a Gaussian process emulator-based approach for uncertainty and global sensitivity analyses, which can be applied to other ACTMs. Conducting these analyses helps to increase the confidence in model predictions. Additionally, the emulators created for these analyses can be used to predict the ACTM response for any other combination of perturbed input emissions within the ranges set for the original Latin hypercube sampling design without the need to rerun the ACTM, thus allowing for fast exploratory assessments at significantly reduced computational costs.

【 授权许可】

CC BY