Simple approximation to extinction efficiency valid over all size parameters

Evans, B. T. N.; Fournier, Georges

doi:10.1364/ao.29.004666

Cited by 37 publications

(14 citation statements)

References 1 publication

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“…Once the feedback mechanism is turned on, the execution time increases only slightly with CAM but increases about 60 % with RRTMG. The numerical techniques used to compute aerosol optical characteristics (extinction, scattering, and asymmetry factor) with the Mie approach used in RRTMG are much more computationally intensive than the Mie approximation (Evans and Fournier, 1990) used in the CAM implementation. However, this new scheme used for RRTMG is more accurate and robust over a wider range of refractive indices.…”

Section: C Wong Et Al: Wrf-cmaq Two-way Coupled System With Aeromentioning

confidence: 99%

WRF-CMAQ two-way coupled system with aerosol feedback: software development and preliminary results

et al. 2012

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Abstract. Air quality models such as the EPA Community Multiscale Air Quality (CMAQ) require meteorological data as part of the input to drive the chemistry and transport simulation. The Meteorology-Chemistry Interface Processor (MCIP) is used to convert meteorological data into CMAQ-ready input. Key shortcoming of such one-way coupling include: excessive temporal interpolation of coarsely saved meteorological input and lack of feedback of atmospheric pollutant loading on simulated dynamics. We have developed a two-way coupled system to address these issues. A single source code principle was used to construct this two-way coupling system so that CMAQ can be consistently executed as a stand-alone model or part of the coupled system without any code changes; this approach eliminates maintenance of separate code versions for the coupled and uncoupled systems. The design also provides the flexibility to permit users: (1) to adjust the call frequency of WRF and CMAQ to balance the accuracy of the simulation versus computational intensity of the system, and (2) to execute the two-way coupling system with feedbacks to study the effect of gases and aerosols on short wave radiation and subsequent simulated dynamics. Details on the development and implementation of this two-way coupled system are provided. When the coupled system is executed without radiative feedback, computational time is virtually identical when using the Community Atmospheric Model (CAM) radiation option and a slightly increased (∼8.5 %) when using the Rapid Radiative Transfer Model for GCMs (RRTMG) radiation option in the coupled system compared to the offline WRF-CMAQ system. Once the feedback mechanism is turned on, the execution time increases only slightly with CAM but increases about 60 % with RRTMG due to the use of a more detailed Mie calculation in this implementation of feedback mechanism. This two-way model with radiative feedback shows noticeably reduced bias in simulated surface shortwave radiation and 2-m temperatures as well improved correlation of simulated ambient ozone and PM 2.5 relative to observed values for a test case with significant tropospheric aerosol loading from California wildfires.

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Section: C Wong Et Al: Wrf-cmaq Two-way Coupled System With Aeromentioning

confidence: 99%

WRF-CMAQ two-way coupled system with aerosol feedback: software development and preliminary results

et al. 2012

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“…This smooth characteristic implies that an accurate approximation to the Mie efficiency can be used in its place to reduce a very computationally intensive task. The method of Evans and Fournier [1990], a highly accurate approximation, is used to calculate Q ext .…”

Section: Model Descriptionmentioning

confidence: 99%

Models‐3 Community Multiscale Air Quality (CMAQ) model aerosol component 1. Model description

et al. 2003

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[1] The aerosol component of the Community Multiscale Air Quality (CMAQ) model is designed to be an efficient and economical depiction of aerosol dynamics in the atmosphere. The approach taken represents the particle size distribution as the superposition of three lognormal subdistributions, called modes. The processes of coagulation, particle growth by the addition of mass, and new particle formation, are included. Time stepping is done with analytical solutions to the differential equations for the conservation of number, surface area, and species mass. The component considers both PM2.5 and PM10 and includes estimates of the primary emissions of elemental and organic carbon, dust, and other species not further specified. Secondary species considered are sulfate, nitrate, ammonium, water, and secondary organics from precursors of anthropogenic and biogenic origin. Extinction of visible light by aerosols is represented by two methods: a parametric approximation to Mie extinction and an empirical approach based upon field data. The algorithms that simulate cloud interactions with aerosols are also described. Results from box model and three-dimensional simulations are exhibited.

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“…Q ext , the Mie extinction efficiency factor, is a function of α and an index of refraction of the particles. It is calculated from the Evans and Fournier approximation (Evans and Fournier, 1990) for each CMAQ species.…”

Section: Appendix a Calculation Of Spectral Extinction From Cmaq Outputsmentioning

confidence: 99%

Simulation of GOES-R ABI aerosol radiances using WRF-CMAQ: a case study approach

Christopher

2014

Atmos. Chem. Phys.

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Abstract. In anticipation of the upcoming GOES-R launch we simulate visible and near-infrared reflectances of the Advanced Baseline Imager (ABI) for cases of high aerosol loading containing regional haze and smoke over the eastern United States. The simulations are performed using the Weather Research and Forecasting (WRF), Sparse Matrix Operator Kernel Emissions (SMOKE), and Community Multiscale Air Quality (CMAQ) models. Geostationary, satellitederived, biomass-burning emissions are also included as an input to CMAQ. Using the CMAQ aerosol concentrations and Mie calculations, radiance is computed from the discrete ordinate atmospheric radiative transfer model. We present detailed methods for deriving aerosol extinction from WRF and CMAQ outputs. Our results show that the model simulations create a realistic set of reflectances in various aerosol scenarios. The simulated reflectances provide distinct spectral features of aerosols which are then compared to data from the Moderate Resolution Imaging Spectroradiometer (MODIS). We also present a simple technique to synthesize green band reflectance (which will not be available on the ABI), using the model-simulated blue and red band reflectance. This study is an example of the use of air quality modeling in improving products and techniques for Earthobserving missions.

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Simple approximation to extinction efficiency valid over all size parameters

Abstract: A semiempirical approximation to the extinction efficiency based on a modification to the anomalous diffraction formula is given and compared to the exact Mie computation. This approximation has been verified for complex refractive indices m = n-ikappa, where 1.01 Show more

Cited by 37 publications

References 1 publication

WRF-CMAQ two-way coupled system with aerosol feedback: software development and preliminary results

WRF-CMAQ two-way coupled system with aerosol feedback: software development and preliminary results

Models‐3 Community Multiscale Air Quality (CMAQ) model aerosol component 1. Model description

Simulation of GOES-R ABI aerosol radiances using WRF-CMAQ: a case study approach

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