Validating Aerosol Optical Depth Estimation Methods Using the National Institute of Environmental Research Operational Numerical Forecast Model

Hye-Jin Kim,Ja-Ho Koo,Ki-Pyo Nam,Chang H Jung,Sang-Hun Park,Uju Shin,Won Jun Choi

doi:10.3390/app12052556

Abstract

Currently, significant efforts are being made to enhance the performance of the National Institute of Environmental Research (NIER) operational model. However, the model performance concerning Aerosol Optical Depth (AOD) estimation remains uninvestigated. In this study, three different estimation methods for AOD were implemented using the NIER operational model and validated with satellite and ground observations. In the widely used Interagency Monitoring of Protected Visual Environments (IMPROVE) method, AOD exponentially increases with relative humidity owing to a hygroscopic growth factor. However, alternative methods show better performance, since AOD estimation considers the size dependency of aerosol particles and is not sensitive to high relative humidity, which reduces the high AOD in areas with large cloud fractions. Although some R values are significantly low, especially for a single observational comparison and small numerical domain analysis, one of the alternative estimation methods achieves the best performance for diagnosing AOD in the East Asia region.

Highlights

As a representing parameter of atmospheric aerosol, aerosol optical depth (AOD), defined as the extinction of solar radiation caused by aerosol and integrated into the whole atmospheric column, is a fundamental optical property parameter and is widely used [2] in the scientific community
Significant efforts are being made to enhance the performance of National Institute of Environmental Research (NIER)’s operational model, in this study, we focused on the ability and performance of AOD estimation based on past forecasting results
Before comparing the capability of AOD estimation between different methods, we summarized the performance of the NIER operational air quality system from the temporal distributions of daily PM2.5

Summary

Introduction

Atmospheric aerosols influence the Earth’s radiation balance by absorbing or scattering radiation and induce climate change [1]. As a representing parameter of atmospheric aerosol, aerosol optical depth (AOD), defined as the extinction of solar radiation caused by aerosol and integrated into the whole atmospheric column, is a fundamental optical property parameter and is widely used [2] in the scientific community. AOD can be expressed as a function of several aerosol related factors, such as aerosol mass concentration, composition, size distribution, and meteorological parameters. Among the many factors which influence the calculation of AOD, hygroscopicity is one of the most uncertain factors [3]. The hygroscopic growth of aerosols is closely related to relative humidity (RH) and influence the physico-chemical characteristics of aerosol. Different aerosol sources, types, and chemical components cause aerosol hygroscopicity to vary with space and time and affect the aerosol optical properties, such as AOD, due to increasing water uptake by increasingly hydrophilic compositions [4]

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