Atmospheric Environment (v.58, #C)

Air Quality Modeling in Asia 2011 by G.R. Carmichael; C.H. Song; Y. Sun Woo; T. Ohara; A. Lau; Y. Koo (2-4).

Development of an anthropogenic emissions processing system for Asia using SMOKE by Jung-Hun Woo; Ki-Chul Choi; Hyeon Kook Kim; Bok H. Baek; Meongdo Jang; Jeong-Hee Eum; Chul Han Song; Young-Il Ma; Young Sunwoo; Lim-Seok Chang; Seung Heon Yoo (5-13).
Air quality modeling is a useful methodology to investigate air quality degradation in various locations and to analyze effectiveness of emission reduction plans. A comprehensive air quality model usually requires a coordinated set of emissions input of all necessary chemical species. We have developed an anthropogenic emissions processing system for Asia in support of air quality modeling and analysis over Asia (named SMOKE-Asia). The SMOKE (Sparse Matrix Operator kernel Emissions) system, which was developed by U.S. EPA and has been maintained by the Carolina Environmental Program (CEP) of the University of North Carolina, was used to develop our emissions processing system. A merged version of INTEX 2006 and TRACE-P 2000 inventories was used as an initial Asian emissions inventory. The IDA (Inventory Data Analyzer) format was used to create SMOKE-ready emissions. Source Classification Codes (SCCs) and country/state/county (FIPS) code, which are the two key data fields of SMOKE IDA data structure, were created for Asia. The 38 SCCs and 2752 FIPS codes were allocated to our SMOKE-ready emissions for more comprehensive processing. US EPA’s MIMS (Multimedia Integrated Modeling System) Spatial Allocator software, along with many global and regional GIS shapes, were used to create spatial allocation profiles for Asia. Temporal allocation and chemical speciation profiles were partly regionalized using Asia-based studies. Initial data production using the developed SMOKE-Asia system was successfully performed. NOx and VOC emissions for the year 2009 were projected to be increased by 50% from those of 1997. The emission hotspots, such as large cities and large point sources, are distinguished in the domain due to spatial allocation. Regional emission peaks were distinguished due to temporally resolved emission information. The PAR (Paraffin carbon bond) and XYL (Xylene and other polyalkyl aromatics) showed the first and second largest emission rate among VOC species. Most of point source emissions are located in layers 3 to 4, which the altitude range reaches 310–550 m AGL. Qualitative inter-comparison between model output and ground/satellite measurement showed good agreements in terms of spatial and temporal patterns. We expect that the result of this study will provide better air quality modeling inputs, which will act as a major step to improve our understanding of Asian air quality.► We developed an anthropogenic emissions processing system for Asia using SMOKE. ► We developed comprehensive modeling emissions inventory and surrogates for processing. ► The 38 SCCs and 2752 FIPS codes were allocated to our SMOKE-ready emissions. ► Performance evaluation using SMOKE-CMAQ and measurements showed good performance.
Keywords: Air Quality; Emission inventory; Emissions processing; SMOKE; CMAQ; Asia;

Effects of below-cloud scavenging on the regional aerosol budget in East Asia by Soo Ya Bae; Rokjin J. Park; Yong Pyo Kim; Jung-Hun Woo (14-22).
We examine the effects of below-cloud scavenging on regional aerosol simulations over East Asia using wet deposition fluxes observed at Acid Deposition Monitoring Network in East Asia (EANET) sites and the Community Multiscale Air Quality (CMAQ) model together with a new below-cloud-scavenging scheme. Typical air quality models, including CMAQ, assume below-cloud scavenging as a simple first-order process with a constant or simple form depending on rain intensity. The scheme used here accounts for the collection efficiency, terminal velocity of raindrops, raindrop-size distributions, and particle-size distributions, which are important factors affecting below-cloud scavenging. We conduct model simulations for spring 2001, including baseline and sensitivity simulations. Our analysis mainly focuses on May 2001 to rule out the effect of dust aerosols. Simulated wet deposition fluxes of SO4 2−, NO3 , and NH4 + by the new scheme are increased by 103, 16, and 108%, respectively, relative to the baseline simulation and show better agreement with observations. The effect of below-cloud scavenging on coarse particles is even greater, producing wet deposition fluxes two orders of magnitude higher than the baseline. The resulting changes in the model indicate the considerable impacts of below-cloud scavenging on regional aerosol simulations over East Asia, where both anthropogenic emissions and natural sources of aerosols are present throughout the year. An accurate wet scavenging simulation is critical to simulate the atmospheric burden and wet deposition fluxes of both fine-mode and coarse-mode aerosols over East Asia.► Use a new mechanistic below-cloud scavenging scheme in CMAQ. ► Effects of below-cloud scavenging are significant for PM wet deposition. ► The effect of below-cloud scavenging on coarse particle is event greater. ► A new scheme alters chemical and physical characteristics of aerosols.
Keywords: CMAQ model; Wet deposition; Aerosol concentration;

Significant differences were found between two particulate sulfate size-distributions measured using a MOUDI impactor at Gosan, Jeju Island, Korea, and simulated via the Lagrangian photochemical model under a condition of aerosol internal mixing between mineral dust and urban pollution particles. It was suspected that these differences might have resulted from: (1) the assumption of aerosol internal mixing and (2) the uses of identical reaction probabilities (γ) of the gaseous sulfate precursors (SO2 and H2SO4) onto both urban pollution particles and mineral dust in the Lagrangian photochemical model simulations. In this study; therefore, some cases of aerosol external mixing between urban-derived pollution aerosols and mineral dust were investigated, with different magnitudes of γ for the gas-phase sulfate precursors onto the two different condensing media. The model simulations under the external mixing condition, with different magnitudes of the reaction probabilities (γi ,urban and γi ,dust) onto urban pollution particles and mineral dust, successfully reproduced the size-dependent particulate sulfate formation measured at the Gosan station. Further attempts were made to approximate the magnitudes of γ SO2,urban and γ H2SO4,dust under external mixing state conditions with the fixed γ SO2,dust and γ H2SO2,urban values of 10−4 and 1.0. The best-estimates of γ SO2,urban and γ H2SO4,dust found in this study were in the orders of 10−4–10−5 and 10−2–10−3, respectively.► Mineral dust particles are found to be mixed almost externally with urban-derived pollution particles in Northeast Asia. ► Two sulfate precursors (SO2 and H2SO4) have different reaction probabilities onto mineral dust and urban-derived pollution particles. ► The best-estimates of γ SO2,urban and γ H2SO4,dust in this study were in the orders of 10−4–10−5 and 10−2–10−3, respectively.
Keywords: Aerosol mixing state; Reaction probability; Lagrangian backward trajectory photochemical model; Urban pollution particles; Mineral dust;

A numerical study on indicators of long-range transport potential for anthropogenic particulate matters over northeast Asia by Cheol-Hee Kim; Sin-Young Park; Yun-Jong Kim; Lim-Seok Chang; Sang-Keun Song; Yun-Seob Moon; Chang-Keun Song (35-44).
Several indicators of the long-range transport potential of particulate matters have been proposed. These indicators can be used in the interpretation of the long-range transport process over northeast Asia. In order to characterize the indicators of long-range transport potential for days during which the concentration of particulate matter is high, we first classified these days during which PM10 concentration was high into two extreme synoptic cases: long-range transport (LRT) case, and local emission with stagnation (LES) case. The classification employed here was on the basis of semi-empirical approach by employing the synoptic meteorological variables including relative vorticity, vorticity advection, and geostrophic wind speed/direction at a geopotential level of over 850 hPa. Simulation results of the two cases using the MM5-CMAQ modeling system were contrasted to determine suitable indicators of LRT potential.The results showed that the most effective indicator is the ratio of aromatic organic compounds to NOx, with correlation coefficients of 0.70 for toluene/NOx, and 0.72 for xylene/NOx. The ratios of N-containing species such as NOx (or NOy) to CO were the next best alternative indicators, with correlation coefficients of 0.53–0.62. The sulfur conversion ratios such as SO4 2−/(SO2 + SO4 2−) and SO4 2−/SO2 suggested good indicators for high sulfate condition (i.e., SO4 2− > 10 μg m−3). However, carbon aerosol ratio OC/EC did not show clearly separated regression lines distinguishing the LRT and LES cases, implying that ratios of both sulfur conversion in less polluted atmosphere and carbon aerosol should be considered carefully using them with confidence about their indication of the LRT potential over northeast Asia.► Little studies on LRT indicator have been carried out over northeast Asia. ► This study proposes indicators of LRT potential for the particulate pollutant. ► The ratio of organic compounds to NOx is found to be the best indicator. ► N-containing ratios such as NOx (or NOy) to CO are the next alternative indicators. ► Sulfur conversion ratios and carbon aerosol ratio are sometimes inadequate.
Keywords: Long range transport indicator; Particulate matters; MM5-CMAQ model; Northeast Asia;

Distribution and direct radiative forcing of black carbon aerosols over Korean Peninsula by Min Young Kim; Seung-Bok Lee; Gwi-Nam Bae; Seung Shik Park; Kyung Man Han; Rae Seol Park; Chul Han Song; Sung Hoon Park (45-55).
Regional air quality modelling was used to simulate the distribution of BC aerosol over the Korean Peninsula for four mid-season months of 2009. Compared to ground-based and satellite observations, the model underestimated the average BC burden significantly, which might be attributed to inaccuracy in BC emissions inventories partly due to the neglect of the emissions from biomass burning although it is not possible to rule out inaccurate prediction of meteorology. The model-estimated monthly average BC burden was highest in winter because of the largest emission. When the BC burden was divided by the monthly emission factor, the adjusted BC burden was much higher in spring and fall than in winter and summer due to strong influence of Chinese source conveyed by westerly wind prevailing in spring and fall. Both long-range transport and local sources were shown to contribute to atmospheric BC over the Korean Peninsula. Urban areas were influenced more by local sources while the effect of long-range transport was higher in remote areas. Based on the model simulations, the direct radiative forcing (DRF) of BC was estimated to be 0.1–1.8 W m−2 over the Korean Peninsula with the domain-average value of 0.39 W m−2. Accounting for the model underestimation of absorbing aerosol optical depth by BC by 48% compared to measured monthly averages due to the underestimated emissions inventories, the adjusted average DRF is 0.75 W m−2.► Black carbon distribution over Korean Peninsula for four seasons was simulated. ► High trans-boundary transport was predicted in spring and in autumn. ► Model underestimated black carbon concentration due to inaccuracy in emissions. ► Both long-range transport and local sources contribute over Korean peninsula. ► Direct forcing of black carbon is larger than that of methane over Korean Peninsula.
Keywords: Black carbon; Radiative forcing; Air quality; Climate; Modelling; Korean Peninsula;

Performance evaluation of the updated air quality forecasting system for Seoul predicting PM10 by Youn-Seo Koo; Sung-Tae Kim; Jin-Sik Cho; Young-Kee Jang (56-69).
The performance of the updated Air Quality Forecasting System (AQFS) using Weather Research and Forecasting (WRF v.3.1) and the U.S. EPA's Models-3/Community Multiscale Air Quality (CMAQ v4.6) with emphasis on PM10 (Particulate Matter with aerodynamic diameters less than 10 μm) forecast is evaluated over the Seoul Metropolitan Area (SMA) for 2010. The simulations of the updated and old forecasting systems are compared with air quality and meteorological measurements in the modeling domain.The results of the analysis show that the updated forecasts of daily PM10 can reproduce the magnitude and temporal variation of the observations. The time variations of forecasted PM10 are in good agreement with the observations with the range of Index of Agreement (IOA) over 0.7. The forecasted concentrations of daily PM10 are underestimated in all forecasting regions with a range of Normalized Mean Bias (NMB) from −10.76% in the Seoul Metropolitan to −21.29% in the North Gyeonggi province. The discrepancy can be attributed to uncertainties in emissions, forecasted meteorology and models. Even with persistent uncertainties in emission data, the PM10 forecasts from the updated system with emission inventories of INTEX-B for year 2006 in Asia, as well as CAPSS supplementing fugitive dust and biomass emissions for year 2007 in Korea, perform better than those of the old system, which consists of MM5 (v4.7) and CMAQ (v.4.3) and the emission data from TRACE-P for 2000 in Asia and CAPSS for 2003 in Korea.It is also demonstrated that the forecasting system is effective to detect the onset time of the episode and peak value of PM10 in advance which is mainly caused by the long-range transport of aerosols from eastern China to the SMA. The Probability of Detection (POD) for the “C” category of Air Quality Index (AQI), which indicates a health risk for the sensitive group, improves to over 60% by applying the bias-adjustment of hybrid forecast (HF).► A development of the Korean Air Quality Forecasting System (AQFS) using WRF and CMAQ models especially focusing on the Seoul Metropolitan Area (SMA). ► Performance evaluation of the AQFS for the year 2010 as well as intensive analysis for the PM10 episode period. ► Updated emissions in Korea were tested using the AQFS. ► The operational PM10 forecasting system is able to provide valuable information to detect the PM10 episode in the SMA.
Keywords: WRF; CMAQ; Forecast; East Asia; Seoul Metropolitan Area; PM10;

Urban air quality and regional haze weather forecast for Yangtze River Delta region by Tijian Wang; Fei Jiang; Junjun Deng; Yi Shen; Qinyan Fu; Qian Wang; Yin Fu; Jianhua Xu; Danning Zhang (70-83).
Air pollution and haze weather have become more and more important environmental and meteorological issues in Yangtze River Delta (YRD) region of China. In order to foster urban and regional air quality management and realize operational prediction and early warning of air pollution and haze weather episode, an urban air quality forecasting system based on the new generation of weather research forecast and chemistry model WRF-Chem and a regional haze weather forecasting system based on Regional Atmospheric Environment Modeling System (RegAEMS) were applied in Shanghai, Nanjing and YRD area. More than one year runs and typical case studies show that WRF-Chem performed well in urban air quality forecast on surface concentrations of air pollutants such as SO2, NO2 and PM10. The accuracy rate of prediction on urban Air Pollution Index (API) is 50–83% and 80% for Shanghai and Nanjing, respectively. RegAEMS presents relatively good ability in forecast on regional haze weather. A new classification standard on haze level was proposed, which take the key parameters such as relative humidity, PM2.5 and visibility into account. It is estimated that RegAEMS predicts haze level with accuracy rate of 58 and 77% for Nanjing and Shanghai in YRD region. Many factors, including meteorology, emission inventory and chemical processes can be attributable to the forecast bias. However, from this study, it is highly suggested that improvements of emission inventory from construction dust, fugitive dust, soil dust, transportation and biomass burning are very crucial to get better performance on air quality and haze weather prediction.► We conduct air quality and haze weather forecast for Yangtze River Delta region. ► WRF-Chem is used for urban air quality forecast in Shanghai and Nanjing. ► RegAEMS is applied for regional haze weather forecast in Yangtze River Delta. ► Both models show good performance in chemical weather forecast.
Keywords: Air quality forecast; Haze weather forecast; Yangtze River Delta; Nanjing; Shanghai;