Abstract
Abstract. A total of 14 chemical transport models (CTMs) participated in the first topic of the Model Inter-Comparison Study for Asia (MICS-Asia) phase III. These model results are compared with each other and an extensive set of measurements, aiming to evaluate the current CTMs' ability in simulating aerosol concentrations, to document the similarities and differences among model performance, and to reveal the characteristics of aerosol components in large cities over East Asia. In general, these CTMs can well reproduce the spatial–temporal distributions of aerosols in East Asia during the year 2010. The multi-model ensemble mean (MMEM) shows better performance than most single-model predictions, with correlation coefficients (between MMEM and measurements) ranging from 0.65 (nitrate, NO3-) to 0.83 (PM2.5). The concentrations of black carbon (BC), sulfate (SO42-), and PM10 are underestimated by MMEM, with normalized mean biases (NMBs) of −17.0 %, −19.1 %, and −32.6 %, respectively. Positive biases are simulated for NO3- (NMB = 4.9 %), ammonium (NH4+) (NMB = 14.0 %), and PM2.5 (NMB = 4.4 %). In comparison with the statistics calculated from MICS-Asia phase II, frequent updates of chemical mechanisms in CTMs during recent years make the intermodel variability of simulated aerosol concentrations smaller, and better performance can be found in reproducing the temporal variations of observations. However, a large variation (about a factor of 2) in the ratios of SNA (sulfate, nitrate, and ammonium) to PM2.5 is calculated among participant models. A more intense secondary formation of SO42- is simulated by Community Multi-scale Air Quality (CMAQ) models, because of the higher SOR (sulfur oxidation ratio) than other models (0.51 versus 0.39). The NOR (nitric oxidation ratio) calculated by all CTMs has larger values (∼0.20) than the observations, indicating that overmuch NO3- is simulated by current models. NH3-limited condition (the mole ratio of ammonium to sulfate and nitrate is smaller than 1) can be successfully reproduced by all participant models, which indicates that a small reduction in ammonia may improve the air quality. A large coefficient of variation (CV > 1.0) is calculated for simulated coarse particles, especially over arid and semi-arid regions, which means that current CTMs have difficulty producing similar dust emissions by using different dust schemes. According to the simulation results of MMEM in six large Asian cities, different air-pollution control plans should be taken due to their different major air pollutants in different seasons. The MICS-Asia project gives an opportunity to discuss the similarities and differences of simulation results among CTMs in East Asian applications. In order to acquire a better understanding of aerosol properties and their impacts, more experiments should be designed to reduce the diversities among air quality models.
Highlights
Urbanization and industrialization have stimulated economic growth and population expansion during the last several decades in East Asia (Spence et al, 2008; Yan et al, 2016; Chen et al, 2016) and brought about noticeable degradation of ecological environment at the same time (Hall, 2002; Han et al, 2014; Yue et al, 2017)
All models were required to run for all of the year 2010, and provide gridded monthly simulation results of aerosols in the first model layer. These chemical transport models (CTMs) include the Weather Research and Forecasting model coupled with Community Multi-scale Air Quality (WRFCMAQ), WRF-Chem, the nested air quality prediction model system (NAQPMS), the non-hydrostatic mesoscale model coupled with chemistry transport model (NHM-Chem), the Goddard Earth Observing System with chemistry (GEOSChem), and the Regional Atmospheric Modeling System coupled with CMAQ (RAMS-CMAQ)
Simulation results of black carbon (BC), OC, SO24−, NO−3, NH+4, PM2.5, PM10, and aerosol optical depth (AOD) are requested to submit for the project, but no data can be acquired from M10, and extremely large values are predicted by M3
Summary
Urbanization and industrialization have stimulated economic growth and population expansion during the last several decades in East Asia (Spence et al, 2008; Yan et al, 2016; Chen et al, 2016) and brought about noticeable degradation of ecological environment at the same time (Hall, 2002; Han et al, 2014; Yue et al, 2017). In order to better understand the properties of atmospheric aerosols and their impacts, chemical transport models (CTMs) can be a critical tool, and they have been applied to study various air-pollution issues all over the world. Hayami et al (2008) and Mann et al (2014) pointed out that different parameterizations used in CTMs can cause large variations in simulation results, and the multi-model ensemble mean (MMEM) tends to show better performance than most single-model predictions when compared with observations (Carmichael et al, 2002; Hayami et al, 2008; Wang et al, 2008; Holloway et al, 2008). As a part of the Acid Deposition Monitoring Network in East Asia (EANET), additional research activity, and a continuing research of MICS-Asia series, three topics were discussed, including comparison and evaluation of current multi-scale air quality models (topic 1), development of reliable emission inventories for CTMs in Asia (topic 2), and interactions between air quality and climate changes (topic 3).
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