Atmospheric Environment (v.42, #15)

MICS-Asia II: The model intercomparison study for Asia phase II by Gregory R. Carmichael; Hiromasa Ueda (3465-3467).

MICS-Asia II: The model intercomparison study for Asia Phase II methodology and overview of findings by G.R. Carmichael; T. Sakurai; D. Streets; Y. Hozumi; H. Ueda; S.U. Park; C. Fung; Z. Han; M. Kajino; M. Engardt; C. Bennet; H. Hayami; K. Sartelet; T. Holloway; Z. Wang; A. Kannari; J. Fu; K. Matsuda; N. Thongboonchoo; M. Amann (3468-3490).
Results from the Model Intercomparison Study Asia Phase II (MICS-Asia II) are presented. Nine different regional modeling groups simulated chemistry and transport of ozone (O3), secondary aerosol, acid deposition, and associated precursors, using common emissions and boundary conditions derived from a global model. Four-month-long periods, representing 2 years and three seasons (i.e., March, July, and December in 2001, and March in 2002), are analyzed. New observational data, obtained under the EANET (the Acid Deposition Monitoring Network in East Asia) monitoring program, were made available for this study, and these data provide a regional database to compare with model simulations. The analysis focused around seven subject areas: O3 and related precursors, aerosols, acid deposition, global inflow of pollutants and precursor to Asia, model sensitivities to aerosol parameterization, analysis of emission fields, and detailed analyses of individual models, each of which is presented in a companion paper in this issue of Atmospheric Environment. This overview discusses the major findings of the study, as well as information on common emissions, meteorological conditions, and observations.
Keywords: Air quality modeling; Asia air quality; Ozone; Aerosol composition;

MICS-Asia II: Model intercomparison and evaluation of ozone and relevant species by Z. Han; T. Sakurai; H. Ueda; G.R. Carmichael; D. Streets; H. Hayami; Z. Wang; T. Holloway; M. Engardt; Y. Hozumi; S.U. Park; M. Kajino; K. Sartelet; C. Fung; C. Bennet; N. Thongboonchoo; Y. Tang; A. Chang; K. Matsuda; M. Amann (3491-3509).
Eight regional Eulerian chemical transport models (CTMs) are compared with each other and with an extensive set of observations including ground-level concentrations from EANET, ozone soundings from JMA and vertical profiles from the TRACE-P experiment to evaluate the models’ abilities in simulating O3 and relevant species (SO2, NO, NO2, HNO3 and PAN) in the troposphere of East Asia and to look for similarities and differences among model performances. Statistical analysis is conducted to help estimate the consistency and discrepancy between model simulation and observation in terms of various species, seasons, locations, as well as altitude ranges. In general, all models show a good skill of simulating SO2 for both ground level and the lower troposphere, although two of the eight models systematically overpredict SO2 concentration. The model skills for O3 vary largely with region and season. For ground-level O3, model results are best correlated with observations in July 2001. Comparing with O3 soundings measured in the afternoon reveals the best consistency among models in March 2001 and the largest disparity in O3 magnitude in July 2001, although most models produce the best correlation in July as well. In terms of the statistics for the four flights of TRACE-P experiment, most models appear to be able to accurately capture the variability in the lower troposphere. The model performances for NO x are relatively poor, with lower correlation and with almost all models tending to underpredict NO x levels, due to larger uncertainties in either emission estimates or complex chemical mechanism represented. All models exhibit larger RMSE at altitudes <2 km than 2–5.5 km, mainly due to a consistent tendency of these models towards underprediction of the magnitude of intense plumes that often originate from near surface. Relatively lower correlation at altitudes 2–5.5 km may be attributed to the models’ limitation in representing convection or potential chemical processes. Most of the key features in species distribution have been consistently reproduced by the participating models, such as the O3 enhancement in the western Pacific Ocean in March and in northeast Asia in July, respectively, although the absolute model values may differ considerably from each other. Large differences are found among models in the southern parts of the domain for all the four periods, including southern China and northern parts of some Southeast Asia countries where the behaviors of chemical components and the ability of these models are still not clearly known because of a lack of observational databases.
Keywords: Chemical transport model; EANET; TRACE-P; Evaluation; Model intercomparison; O3 and relevant species; Seasonality;

MICS-Asia II: Model intercomparison and evaluation of particulate sulfate, nitrate and ammonium by Hiroshi Hayami; T. Sakurai; Z. Han; H. Ueda; G.R. Carmichael; D. Streets; T. Holloway; Z. Wang; N. Thongboonchoo; M. Engardt; C. Bennet; C. Fung; A. Chang; S.U. Park; M. Kajino; K. Sartelet; K. Matsuda; M. Amann (3510-3527).
Eight chemical transport models participate in a model intercomparison study for East Asia, MICS-Asia II. This paper analyzes calculated results for particulate matter of sulfate, nitrate and ammonium through comparisons with each other and with monthly measurements at EANET (the acid deposition monitoring network in East Asia) and daily measurements at Fukue, Japan.To the EANET measurements, model ensemble means better agree with model individual results for sulfate and total ammonium, although total nitrate is consistently and considerably underestimated. To measurements at Fukue, the models show better agreement than for the EANET measurements. This is likely because Fukue is centered in many of the model domains, whereas the EANET stations are mostly in Southeast Asia and Russia. Moreover, it would be important that Fukue is in Northeast Asia, where the emission inventory is more reliable than Southeast Asia.The model–model comparisons are made in view of the total amount in the atmosphere, vertical profile, coefficient of variation in surface concentrations, and transformation changes with distance. All the models show reasonable tendencies in vertical profiles and composition ratios. However, total amounts in the atmosphere are discrepant among the models. The consistency of the total amount in the atmosphere would influence source–receptor analysis. It seems that model results would be consistent, if the models take into account the primitive processes like emission, advection/diffusion, chemical transformation and dry/wet deposition, no matter the processes are modeled simply or comprehensively.Through the comparison study, we learned that it would be difficult to find any problems from one comparison (model-observation comparison with one data or many but at one station or in a short period). Modelers tend to examine model performances only from model-observation comparisons. However, taking budget in a certain or whole model domain would be important, before the models are applied to source–receptor analysis.
Keywords: Chemical transport models; Model intercomparison; EANET; Sulfate; Nitrate;

MICS-Asia II: Model inter-comparison and evaluation of acid deposition by Zifa Wang; Fuying Xie; T. Sakurai; H. Ueda; Zhiwei Han; G.R. Carmichael; D. Streets; M. Engardt; T. Holloway; H. Hayami; M. Kajino; N. Thongboonchoo; C. Bennet; S.U. Park; C. Fung; A. Chang; K. Sartelet; M. Amann (3528-3542).
This paper focuses on the comparison of chemical deposition of eight regional chemical models used in Model Inter-Comparison Study for Asia (MICS-Asia) II. Monthly-mean depositions of chemical species simulated by these models, including dry deposition of SO2, HNO3, NH3, sulfate, nitrate and ammonium and wet deposition of SO4 2−, NO3 and NH4 +, have been provided for four periods (March, July, December 2001 and March 2002) in this work. Observations at 37 sites of the Acid Deposition Monitoring Network in East Asia (EANET) are compared with SO4 2−, NO3 and NH4 + wet deposition model results. Significant correlations appeared between the observation and computed ensemble mean of participant models. Also, differences among modeled sulfur and nitrogen dry depositions have been studied at the EANET sites. Based on the analysis of acid deposition for various species from different models, total depositions of sulfur (SO2 and sulfate) and nitrogen (nitrate and ammonium) have been evaluated as the ensemble mean of the eight models. In general, all models capture the observed spatial distribution of sulfur and nitrogen deposition, although the absolute values may differ from measurements. High deposition often occurs in eastern China, Japan, the Republic of Korea, Thailand, Vietnam, Philippines and other parts of Southeast Asia. The magnitude of model bias is quite large for many of the models. In examining the reasons for model–measurement disagreement, we find that differences in chemical processes, deposition parameterization, and modeled precipitation are the main reasons for large model disparities.
Keywords: Acid deposition; EANET; Evaluation; Sulfate; Nitrate; Model inter-comparison;

MICS-Asia II: Impact of global emissions on regional air quality in Asia by Tracey Holloway; Tatsuya Sakurai; Zhiwei Han; Susanna Ehlers; Scott N. Spak; Larry W. Horowitz; Gregory R. Carmichael; David G. Streets; Y. Hozumi; Hiromasa Ueda; S.U. Park; Christopher Fung; M. Kajino; Narisara Thongboonchoo; Magnuz Engardt; Cecilia Bennet; Hiroshi Hayami; Karine Sartelet; Zifa Wang; K. Matsuda; Markus Amann (3543-3561).
This study quantifies the seasonality and geographic variability of global pollutant inflow to Asia. Asia is often looked to as a major source of intercontinental air pollution transport with rising emissions and efficient pollutant export processes. However, the degree to which foreign emissions have been imported to Asia has not been thoroughly examined. The Model Inter-Comparison Study for Asia (MICS-Asia) is an international collaboration to study air pollution transport and chemistry in Asia. Using the global atmospheric chemistry Model of Ozone and Related Tracers (MOZART v. 2.4), and comparing results with a suite of regional models participating in MICS-Asia, we find that imported O3 contributes significantly throughout Asia. The choice of upper boundary condition is found to be particularly important for O3, even for surface concentrations. Both North America and Europe contribute to ground-level O3 concentrations throughout the region, though the seasonality of these two sources varies. North American contributions peak at over 10% of monthly mean O3 during winter months in East Asia, compared to Europe's spring- and autumn-maxima (5–8%). In comparison to observed data from the Acid Deposition Monitoring Network in East Asia (EANET), MOZART concentrations for O3 generally fall within the range of the MICS models, but MOZART is unable to capture the fine spatial variability of shorter-lived species as well as the regional models.
Keywords: MICS-Asia; Inter-comparison; Hemispheric transport; Air pollution; Ozone; Carbon monoxide;

MICS Asia Phase II—Sensitivity to the aerosol module by K.N. Sartelet; H. Hayami; B. Sportisse (3562-3570).
In the framework of the model intercomparison study—Asia Phase II (MICS2), where eight models are compared over East Asia, this paper studies the influence of different parameterizations used in the aerosol module on the aerosol concentrations of sulfate and nitrate in PM 10 .An intracomparison of aerosol concentrations is done for March 2001 using different configurations of the aerosol module of one of the model used for the intercomparison. Single modifications of a reference setup for model configurations are performed and compared to a reference case. These modifications concern the size distribution, i.e. the number of sections, and physical processes, i.e. coagulation, condensation/evaporation, cloud chemistry, heterogeneous reactions and sea-salt emissions.Comparing monthly averaged concentrations at different stations, the importance of each parameterization is first assessed. It is found that sulfate concentrations are little sensitive to sea-salt emissions and to whether condensation is computed dynamically or by assuming thermodynamic equilibrium. Nitrate concentrations are little sensitive to cloud chemistry. However, a very high sensitivity to heterogeneous reactions is observed.Thereafter, the variability of the aerosol concentrations to the use of different chemistry transport models (CTMs) and the variability to the use of different parameterizations in the aerosol module are compared. For sulfate, the variability to the use of different parameterizations in the aerosol module is lower than the variability to the use of different CTMs. However, for nitrate, for monthly averaged concentrations averaged over four stations, these two variabilities have the same order of magnitude.
Keywords: Aerosol; Variability; Chemistry transport model; Size distribution; Coagulation; Condensation; Cloud chemistry; Heterogeneous reactions; Sea-salt emissions;

MICS-Asia II: Modeling gaseous pollutants and evaluating an advanced modeling system over East Asia by Joshua S. Fu; Carey J. Jang; David G. Streets; Zuopan Li; Roger Kwok; Rokjin Park; Zhiwei Han (3571-3583).
An advanced modeling system with a “one-atmosphere” perspective, Models-3/Community Multi-scale Air Quality (CMAQ) modeling system, driven by MM5/NCEP reanalysis data as the meteorology, and GEOS-Chem outputs as boundary values was applied to simulate the O3, and other gaseous pollutants (SO2 and NO2) evolution among other atmospheric chemicals for July 2001. Comparisons had been made with other models in the MICS-II exercise for the same period. Statistics of both monthly and daily means show that the model skill is very good in reproducing O3 and SO2 with small to moderate RMSE. The model species capture the day-to-day and spatial variability of the observations. The same O3 model concentrations that overpredict most of the EANET observations in the MICS-II study may have underpredicted ones from monitoring networks in Beijing area that is not included in this paper. Vertical O3 profiles at 4 ozonesonde sites are well predicted in July 2001. In fact, our model is among the best of those MICS-II models within the 2-km surface layer. The meteorology near surface and lower troposphere is well reproduced. Compared to SO2 and O3, the NO2 gas concentrations are simulated less well, but the correlation coefficient is still significant.The choice of reanalysis meteorological fields and different boundary conditions generated by different global models may result in diverse spatial patterns exhibited by MICS-II models and ours. Our spatial distributions of O3 shows a high concentration patch covering Beijing, a moderate to high pattern across Korea and Japan Sea, and a low but extensive pattern enclosing southern China, Taiwan, and East Sea. Extension of the pattern to southern China coincides with the existence of pollution problems in Guangdong and Taiwan, but overprediction of O3 over the region deserves further improvement by various factors. One of them can be the grid resolution to resolve the complex orography in or close to the ocean. Another factor can be the refinement of local land use data that changes the micro-meteorology in favor of more air pollution events.
Keywords: CMAQ; EANET; GEOS-Chem; Model performance; TRACE-P;

MICS-Asia II: An inter-comparison study of emission inventories for the Japan region by Akiyoshi Kannari; David G. Streets; Yutaka Tonooka; Kentaro Murano; Tsuyoshi Baba (3584-3591).
For the model intercomparison study, MICS Asia phase II, standard air pollutants emission data are provided from published research results (the TRACE-P data set) and other recent work. To provide preliminary information concerning the reliability of the standard emissions data, this inventory was compared with a local emission inventory, EAGrid2000-Japan, which has been developed for detailed analyses with fine grid data resolution for the Japan region. Although these inventories are based upon different estimation methodologies, from the comparative analyses it was found that regional emissions of the standard data are consistent, with differences smaller than 10% for SO2, NO x , NMVOC and CO2, and smaller than 30% for CO and NH3. Differences for all species are smaller than the 95% confidence intervals that were estimated in the research that produced the standard emissions data. Additional information is provided regarding emissions of PM10 and PM2.5, although these did not originate in the TRACE-P data. Furthermore, it was found that the 0.5°×0.5° grid-based emissions from the two inventories match well for NO x , NMVOC, CO, and PM2.5, even though the spatial allocation techniques for the local inventory are much more detailed. For SO2 emissions, the differences in the grid-based inventories are greater. Although some problems still remain, such as diurnal variations that are not considered in the standard emissions data, the intercomparison analysis suggests that the standard emissions data have appropriate properties for atmospheric model simulation.
Keywords: Emissions inventory; Intercomparison; East Asia; Japan;