MICS-Asia III: overview of model intercomparison and evaluation of acid deposition over Asia

Abstract

Abstract. The Model Inter-Comparison Study for Asia (MICS-Asia) phase III was conducted to promote understanding of regional air quality and climate change in Asia, which have received growing attention due to the huge amount of anthropogenic emissions worldwide. This study provides an overview of acid deposition. Specifically, dry and wet deposition of the following species was analyzed: S (sulfate aerosol, sulfur dioxide (SO2), and sulfuric acid (H2SO4)), N (nitrate aerosol, nitrogen monoxide (NO), nitrogen dioxide (NO2), and nitric acid (HNO3)), and A (ammonium aerosol and ammonia (NH3)). The wet deposition simulated by a total of nine models was analyzed and evaluated using ground observation data from the Acid Deposition Monitoring Network in East Asia (EANET). In the phase III study, the number of observation sites was increased from 37 in the phase II study to 54, and southeast Asian countries were newly added. Additionally, whereas the analysis period was limited to representative months of each season in MICS-Asia phase II, the phase III study analyzed the full year of 2010. The scope of this overview mainly focuses on the annual accumulated deposition. In general, models can capture the observed wet deposition over Asia but underestimate the wet deposition of S and A, and show large differences in the wet deposition of N. Furthermore, the ratio of wet deposition to the total deposition (the sum of dry and wet deposition) was investigated in order to understand the role of important processes in the total deposition. The general dominance of wet deposition over Asia and attributions from dry deposition over land were consistently found in all models. Then, total deposition maps over 13 countries participating in EANET were produced, and the balance between deposition and anthropogenic emissions was calculated. Excesses of deposition, rather than of anthropogenic emissions, were found over Japan, northern Asia, and southeast Asia, indicating the possibility of long-range transport within and outside of Asia, as well as other emission sources. To improve the ability of models to capture the observed wet deposition, two approaches were attempted, namely, ensemble and precipitation adjustment. The ensemble approach was effective at modulating the differences in performance among models, and the precipitation-adjusted approach demonstrated that the model performance for precipitation played a key role in better simulating wet deposition. Finally, the lessons learned from the phase III study and future perspectives for phase IV are summarized.

Model Performance Differences in Fine-Mode Nitrate Aerosol during Wintertime over Japan in the J-STREAM Model Inter-Comparison Study

“…This difference was more than 1.0 µg/m 3 , and considering the low concentration level over the northern part of d01 (e.g., the far-east region of Russia), the selection of the global model will be an important setting for refining the model simulation over northern parts of the Asian continent. This point was also mentioned in the Asian-scale model inter-comparison study (MICS-Asia) [45,46]. Another possibility in addition to the aerosol components themselves was the difference caused by other species.…”

Supplementary material to "Comparison of three aerosol representations of NHM-Chem (v1.0) for the simulations of air quality and climate-relevant variables"

“…Many of the schemes are similar or almost equivalent to those implemented in widely used regional community models, such as CMAQ (Byun and Schere, 2006;Wong et al, 2012) and WRF-Chem (Grell et al, 2005;Chapman et al, 2009), as seen from the result of a multi-CTM intercomparison study (Li et al, 2019;Chen et al, 2019;Itahashi et al, 2020;Kong et al, 2020;Tan et al, 2020;Ge et al, 2020): NHM-Chem behaved similarly to the other models, including CMAQ and WRF-Chem. The advantage of the current model is not considerable, except for the detailed fog deposition and belowcloud scavenging parameterizations.…”

Why do models perform differently on particulate matter over East Asia? A multi-model intercomparison study for MICS-Asia III

“…In this study, the WRF-Chem models (M7 and M8) turned off the sea-salt emissions; thus, their PMC concentrations over the oceans and seas are not defined. The two WRF-CMAQ models use the in-line sea-salt emission module of Gong (2003) with updates by Kelly et al (2010). They predict consistent distributions of PMC over oceans.…”

“…Sea-salt emissions are reported to contribute 20 %-40 % of SNA and PM 10 over coastal regions . Including the sea-salt emissions in model simulations can improve the model accuracy with an 8 %-20 % increase in PM 10 , SNA, Na + and Cl − (Kelly et al, 2010;Im, 2013). The influence of sea-salt emissions is not the focus of this study, but further study is strongly recommended.…”