Modeling intercontinental air pollution transport over the trans‐Pacific region in 2001 using the Community Multiscale Air Quality modeling system

Abstract

The Community Multiscale Air Quality modeling system is used to study the intercontinental transport of air pollution across the Pacific region. Baseline simulations are conducted for January, April, July, and October 2001 at a 108 km horizontal grid resolution. A sensitivity simulation is conducted for April 2001 to study the impact of Asian anthropogenic emissions on the United States's air quality. Process analysis is conducted to study pollutant formation and transport and to quantify the relative contributions of atmospheric processes to ozone (O3) and fine particulate matter (PM2.5). Model simulations are evaluated with available surface, aircraft, and satellite observations. Simulated meteorology basically captures the synoptic pattern, but precipitation amounts are significantly underpredicted. Most of the PM2.5 components are overestimated over the United States and most gases are underestimated over east Asia. Simulated NO2 and CO columns agree well with satellite observations. Aerosol optical depths and tropospheric O3 residuals are underpredicted, especially in July. The simulated horizontal fluxes and process analyses show that the transport in the lower free troposphere followed by a large‐scale subsidence over the United States provides a major Asian pollution export pathway for most pollutants, while the transport in the planetary boundary layer also plays an important role, especially for CO, O3, PM2.5, and SO42−. The background concentrations of O3 and SO42− in the western United States can increase by ∼1 ppb (∼2.5%) and 0.4 μg m−3 (∼20%) in monthly average, up to 2.5 ppb and 1.0 μg m−3 in daily average, respectively, due to the Asian emissions in April.

Multi-year downscaling application of two-way coupled WRF v3.4 and CMAQ v5.0.2 over east Asia for regional climate and air quality modeling: model evaluation and aerosol direct effects

“…The CMAQ performance of chemical predictions in this study was comparable to or even better than those of other air quality studies over east Asia (Wang et al, 2009(Wang et al, , 2012Liu et al, , 2016Zheng et al, 2015;Hu et al, 2016;Zhang et al, 2016a). This study predicted relatively well for Figure 7.…”

“…Recently, the online-coupled Weather Research and Forecasting (WRF) model with Chemistry (WRF-Chem) was evaluated for decadal application over the continental US under RCP4.5 and RCP8.5 (Yahya et al, 2016(Yahya et al, , 2017a and applied to decadal projections of future climate and air quality under both scenarios (Yahya et al, 2017b). The Community Multi-scale Air Quality (CMAQ) model has historically been an offline model developed by the US Environmental Protection Agency (EPA) and widely used for air quality simulations over numerous countries and regions (Wang et al, 2009(Wang et al, , 2012Gao et al, 2013;Penrod et al, 2014;Sun et al, 2015;Zheng et al, 2015;Hu et al, 2016); it has recently been further developed to provide an online-coupled version with the Weather Research Forecast (WRF) model to simulate feedbacks between chemistry and meteorology (Wong et al, 2012). Several applications of the two-way coupled WRF-CMAQ model have been conducted to evaluate the performance of the coupled model system and to investigate aerosol direct effects Gan et al, 2015;Hogrefe et al, 2015;Xing et al, 2016) and indirect effects (Yu et al, 2014) on climate and air quality.…”

Application of an Online-Coupled Regional Climate Model, WRF-CAM5, over East Asia for Examination of Ice Nucleation Schemes: Part I. Comprehensive Model Evaluation and Trend Analysis for 2006 and 2011

“…As a result, the model agreement with observations is not expected to be comparable with simulations that use FDDA. The annual mean MBs of T2 are larger than the suggested threshold values by Emery et al ([49]) but they are comparable or even better than the performance using MM5 (e.g., [44,50]) and WRF (e.g., [47,48,51,52]), and hence deemed acceptable.…”

Online coupled regional meteorology chemistry models in Europe: current status and prospects

“…Operational evaluation was not only a focus of AQMEII but has generally been the most widely used approach in the past for both offline (Trukenmüller et al, 2004;Schlünzen and Meyer, 2007;Appel et al, 2008;Wang et al, 2009;Zhang et al, 2009a;Liu et al, 2010) and online coupled models (Zhang et al, 2010a(Zhang et al, , b, 2012c(Zhang et al, , d, 2013Knote et al, 2011;Tuccella et al, 2012).…”