Abstract. This paper introduces a novel Lagrangian model
(Concentration Trajectory Route of Air pollution with an Integrated
Lagrangian model, C-TRAIL version 1.0) output from a Eulerian air quality
model for validating the source–receptor direct link by following polluted
air masses. To investigate the concentrations and trajectories of air masses
simultaneously, we implement the trajectory-grid (TG) Lagrangian advection
scheme in the CMAQ (Community Multiscale Air Quality) Eulerian model version
5.2. The TG algorithm follows the concentrations of representative air
“packets” of species along trajectories determined by the wind field. The
diagnostic output from C-TRAIL accurately identifies the origins of
pollutants. For validation, we analyze the results of C-TRAIL during the
KORUS-AQ campaign over South Korea. Initially, we implement C-TRAIL in a
simulation of CO concentrations with an emphasis on the long- and
short-range transport effects. The output from C-TRAIL reveals that local
trajectories were responsible for CO concentrations over Seoul during the
stagnant period (17–22 May 2016) and during the extreme pollution period
(25–28 May 2016), highly polluted air masses from China were distinguished
as sources of CO transported to the Seoul Metropolitan Area (SMA). We
conclude that during the study period, long-range transport played a crucial
role in high CO concentrations over the receptor area. Furthermore, for May 2016, we find that the potential sources of CO over the SMA were the result
of either local transport or long-range transport from the Shandong
Peninsula and, in some cases, from regions north of the SMA. By identifying
the trajectories of CO concentrations, one can use the results from C-TRAIL
to directly link strong potential sources of pollutants to a receptor in
specific regions during various time frames.
Abstract. This paper introduces a reliable and comprehensive Lagrangian output (Concentration Trajectory Route of Air pollution with Integrated Lagrangian model, C-TRAIL version 1.0) from an Eulerian air quality model for validating the source-receptor link by following real polluted air masses. To investigate the concentrations and trajectories of air masses simultaneously, we implement the trajectory-grid (TG) Lagrangian advection scheme in the CMAQ (Community Multiscale Air Quality) Eulerian model version 5.2. The TG algorithm follows the concentrations of representative air packets of species along trajectories determined by the wind field. The generated output from C-TRAIL accurately identifies the origins of pollutants. For validation, we analyzed the results of C-TRAIL during the KORUS-AQ campaign over South Korea. Initially, we implemented C-TRAIL in a simulation of CO concentrations with an emphasis on the long- and short-range transport effect. The output from C-TRAIL reveals that local trajectories were responsible for CO concentrations over Seoul during the stagnant period (May 17–22, 2016) and during the extreme pollution period (May 25–28, 2016), highly polluted air masses from China were distinguished as sources of CO transported to the Seoul Metropolitan Area (SMA). We conclude that long-range transport played a crucial role in high CO concentrations over the receptor area during this period. Furthermore, for May 2016, we find that the potential sources of CO over that SMA were the result of either local transport or long-range transport from the Shandong Peninsula and, in some cases, from north of the SMA. By identifying the trajectories of CO concentrations, one can use the results from C-TRAIL to directly link strong potential sources of pollutants to a receptor in specific regions during various time frames.
To improve the representation of convective mixing of atmospheric pollutants in the presence of clouds, we developed a convection module based on Kain and Fritsch (KF) method and implemented it in the CMAQ (Community Multiscale Air Quality) model. The KF-convection method is a mass-flux-based model that accounts for updraft flux, downdraft flux, entrainment, detrainment, and the subsidence effect. The method is consistent with the convection parametrization of the meteorology model. We apply the KF-convection model to an idealized case and to a reference setup prepared for East Asia during the KORUS-AQ campaign period to investigate its impact on carbon monoxide (CO) concentration at various atmospheric altitudes. We investigate the impact of KF-convection on the horizontal distribution of CO concentrations by comparing it to aircraft measurements and the MOPITT CO column. We further discuss two types of impacts of KF-convection: the direct impact caused by vertical movement of CO concentrations by updraft or downdraft and the indirect impact caused by transport of lifted CO concentrations to another region. May 12 saw a high indirect impact originating from the Shanghai region at higher altitudes and a high direct impact of updraft fluxes at 1 km altitude. However, May 26 revealed an immense updraft increasing higher altitude concentrations (up to 40 ppbv) and diverse indirect impacts over the region of the study (±50 ppbv). The overall comparison shows a strong connection between differences in the amount of concentration caused by the direct impact at each altitude with the presence of an updraft at that altitude.The developed model can be employed in large domains (i.e., East Asia, Europe, North America, and Northern Hemisphere) with sub-grid scale cloud modeling to include the impacts of convection.
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