Seriously stringent emission regulations are applied in the coal-fired power sector in China. GB13223-2011 standards and ultra-low emission limits are promulgated to improve the application of ...pollutant abatement systems and reduce emissions, respectively. However, the accompanying problem of additional economic burden may affect the operation of power units and sectors. This study proposed a cost estimate model of multi-pollutant control and designed several scenarios to evaluate the total cost of different emission standards in China's coal-fired power sector. The operating costs of NOx, SO2, and PM control of a typical 300 MW unit were 6.9, 11.7, and 4.3 CNY/MWh, respectively, when meeting the GB13223-2011 emission standard and 8.2, 13.8, and 7.9 CNY/MWh, respectively, when meeting the ultra-low emission limits. Investment, energy consumption, and catalyst greatly influenced the operating cost. The scenarios analysis suggested that the total costs of multi-pollutant control under the GB13223-2011 standards and ultra-low emission limits were approximately 141.79–170.28 and 186.35–221.67 billion CNY per year, respectively. Feasible cost reduction strategies were analyzed on the basis of operation management and sector planning. The economic influence of the application of pollutant abatement systems on coal-fired power units should be evaluated comprehensively.
•The additional cost of emission control in coal-fired power sector is acceptable.•High investment and energy and resource consumptions are the main barriers.•Regional costs of different scenarios are estimated at different standards.•Operation management can achieve the cost reduction.•Installing the pollutants abatement system in small capacity unit will cost more.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Global reactive nitrogen (N) deposition has more than tripled since 1860 and is expected to remain high due to food production and fossil fuel consumption. Global sulfur emissions have been ...decreasing worldwide over the last 30 years, but many regions are still experiencing unhealthily high levels of deposition. We update the 2010 global deposition budget for reactive nitrogen and sulfur components with new regional wet deposition measurements from Asia, improving the ensemble results of 11 global chemistry transport models from the second phase of the United Nations Economic Commission for Europe's Task Force on Hemispheric Transport of Air Pollution (HTAP II). The observationally adjusted global N deposition budget is 114.5 Tg N, representing a minor increase of 1 % from the model-only derived values, and the adjusted global sulfur deposition budget is 88.9 Tg S, representing a 6.5 % increase from the modeled values, using an interpolation distance of 2.5∘. Regionally, deposition adjustments can be up to ∼ 73 % for nitrogen and 112 % for sulfur. Our study demonstrates that a global measurement–model fusion approach can improve N and S deposition model estimates at a regional scale, with sufficient availability of observations; however, in large parts of the world, alternative approaches need to be explored. The analysis presented here represents a step forward toward the World Meteorological Organization's goal of global fusion products for accurately mapping harmful air pollution deposition.
Wildfire emission inventories are usually applied with biome‐scale emission factors for atmospheric modeling. However, emission factors measured for different plant species vary substantially within ...the same biome. We apply the species‐specific emission factors and refine the Fire Emission Inventory‐northern Eurasia (FEI‐NE), and derive the wildfire black carbon emission inventory in northern Eurasia from 2002 to 2015. Our new inventory produces 61% more black carbon emissions than current estimates based on Global Fire Emission Database (GFED) and 33% less than FEI‐NE. Model simulations with different inventories are compared with ground‐based and satellite retrievals of aerosol absorption optical depth (AAOD). Compared with the Ozone Monitoring Instrument, the normalized root mean square deviation of AAOD over northern Eurasia is reduced from 1.0 under FEI‐NE to 0.95 through application of the new inventory. This study reveals the importance of applying sub‐biome‐scale emission factors for wildfire inventories development and revisiting emissions uncertainty in atmospheric modeling.
Plain Language Summary
A recent biomass burning emission inventory for black carbon in northern Eurasia was developed as FEI‐NE. We found that the emission factors applied for wildfires in northern Eurasia boreal forest and grassland were adopted from the prescribed fire measurements conducted in the United States for woody savannas and wetlands, respectively. By comparing with recently published local measurements in Siberia, we mapped the emission factors for plant species from the database published by U.S. Forest Service to biomass structures in northern Eurasia and rebuilt the FEI‐NE inventory as FEI‐NEsp. Modeling results obtained from GEOS‐Chem for 2011–2012 suggested that the simulation with FEI‐NEsp agreed better with ground‐based and satellite observations than FEI‐NE and GFEDv4.1s.
Key Points
Emission factors indexed by plant species are used to replace biome‐scale factors to update fire emission inventory over northern Eurasia
Updated fire emission for black carbon over northern Eurasia is 33% lower than the original inventory FEI‐NE, but 61% higher than GFED
Simulation with the new inventory shows better reproduced ground‐based and satellite retrievals of aerosol absorption optical depth
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
We apply the Lagrangian-based moisture back trajectory method to two reanalysis datasets to determine the moisture sources for wet season precipitation over the Arabian Peninsula, defined as land on ...the Asian continent to the south of the Turkish border and west of Iran. To accomplish this, we make use of the evaporative source region between 65°W–120°E and 30°S–60°N, which is divided into twelve sub-regions. Our comparison of reanalyses and multiple observations allows us to validate datasets and highlight broad-scale similarities in characteristics, notwithstanding some inconsistencies in the southwest AP. The results indicate north-to-south spatiotemporal heterogeneity in the characteristics of dominant moisture sources. In the north, moisture for precipitation is mainly sourced from midlatitude land and water bodies, such as the Mediterranean and Caspian Seas. Areas further south are dependent on moisture transport from the Western Indian Ocean and parts of the African continent. The El Niño-Southern Oscillation (ENSO) exhibits an overall positive but sub-seasonally varying influence on the precipitation variability over the region, with noticeable moisture anomalies from all major source regions. A significant drying trend exists over parts of the Peninsula, which both reanalyses partially attribute to anomalies in the moisture advection from the Congo Basin and South Atlantic Ocean. However, considerable uncertainty in evaporation trends over the terrestrial evaporative sources in observations warrants additional modeling studies to further our understanding of key processes contributing to the negative trends.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Spatiotemporal variations of ozone (O3) and nitrogen oxide (NOx) mixing ratios from 14 state-of-the-art chemical transport models (CTMs) are intercompared and evaluated with O3 observations in East ...Asia, within the framework of the Model Inter-Comparison Study for Asia Phase III (MICS-Asia III). This study was designed to evaluate the capabilities and uncertainties of current CTMs simulations for Asia and to provide multi-model estimates of pollutant distributions. These models were run by 14 independent groups working in China, Japan, South Korea, the United States and other countries/regions. Compared with the previous phase of MICS-Asia (MICS-Asia II), the evaluation with observations was extended from 4 months to 1 full year across China and the western Pacific Rim. In general, model performance levels for O3 varied widely by region and season. Most models captured the key patterns of monthly and diurnal variation of surface O3 and its precursors in the North China Plain and western Pacific Rim but failed to do so for the Pearl River Delta. A significant overestimation of surface O3 was evident from May to September/October and from January to May over the North China Plain, the western Pacific Rim and the Pearl River Delta. Comparisons drawn from observations show that the considerable diversity in O3 photochemical production partly contributed to this overestimation and to high levels of inter-model variability in O3 for North China. In terms of O3 soundings, the ensemble average of models reproduced the vertical structure for the western Pacific, but overestimated O3 levels to below 800 hPa in the summer. In the industrialized Pearl River Delta, the ensemble average presented an overestimation for the lower troposphere and an underestimation for the middle troposphere. The ensemble average of 13 models for O3 did not always exhibit superior performance compared with certain individual models in contrast with its superior value for Europe. This finding suggests that the spread of ensemble-model values does not represent all of the uncertainties of O3 or that most MICS-Asia III models missed key processes. This study improved the performance of modeling O3 in March at Japanese sites compared with MICS-Asia II. However, it overpredicted surface O3 concentrations for western Japan in July, which was not found by MICS-Asia II. Major challenges still remain with regard to identifying the sources of bias in surface O3 over East Asia in CTMs.
Accurate estimation on reaction nitrogen (Nr) deposition is highly demanded for assessing the impacts on the environment and human beings. This study investigated the wet deposition of inorganic ...nitrogen (IN) in mainland China by measurements from over 500 sites from five observational networks/databases and ensemble results of eleven chemical transport models (CTMs). Each data source has its focus and limitations and together formed a comprehensive view over China. But the inconsistency among different sources may hinder the appropriate usage of data. Model evaluation results demonstrated the models' deficiency in simulating the wet NO3− deposition over Southeast China (40 % underestimation) and showed an overall underestimation of wet NH4+ deposition over the hotspot regions (5–60 % underestimation). A synthesis of this study and twelve reference studies was conducted to quantify the national amount of wet IN deposition. The estimations by CTMs ranged 2.4–3.9 Tg(N) yr−1 for wet NOy deposition and 4–6.7 Tg(N) yr−1 for wet NHx deposition, after adjusting the results with 10–19 % underestimations in wet NOy deposition and 1–40 % underestimations in wet NHx deposition. The estimations by ground observations ranged 7.1–9 Tg(N) yr−1 for wet NOy deposition and 8–13.1 Tg(N) yr−1 for wet NHx deposition, which were 20–275 % higher than the estimation by CTMs, but the results were strongly influenced by the abundances and representative of measurements. Studies using statistical techniques to interpolate site observations predicted 3–5.5 Tg(N) yr−1 for wet NOy deposition and 3.9–7.2 Tg(N) yr−1 for wet NHx deposition. This approach benefited from high accuracy and good robustness of the statistical models, but the uncertainty in the interpolation methods could be a potential drawback.
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•Monitoring networks of wet Nr deposition (>500 sites) over China are summarized.•Model capability on predicting wet Nr deposition are evaluated.•China's wet Nr deposition ranges 7–22 Tg(N) yr−1 by different approaches.•Uncertainties of different estimation approaches are discussed.•Intergradation of available data (monitoring, satellite and modelling) is suggested.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Topic 3 of the Model Inter-Comparison Study for Asia (MICS-Asia) Phase III
examines how online coupled air quality models perform in simulating
wintertime haze events in the North China Plain region ...and evaluates the
importance of aerosol radiative feedbacks. This paper discusses the
estimates of aerosol radiative forcing, aerosol feedbacks, and possible
causes for the differences among the participating models. Over the
Beijing–Tianjin–Hebei (BTH) region, the ensemble mean of estimated aerosol
direct radiative forcing (ADRF) at the top of atmosphere, inside the
atmosphere, and at the surface are −1.1, 7.7, and −8.8 W m−2 during
January 2010, respectively. Subdivisions of direct and indirect aerosol
radiative forcing confirm the dominant role of direct forcing. During severe
haze days (17–19 January 2010), the averaged reduction in near-surface
temperature for the BTH region can reach 0.3–1.6 ∘C. The
responses of wind speeds at 10 m (WS10) inferred from different models show
consistent declines in eastern China. For the BTH region, aerosol–radiation
feedback-induced daytime changes in PM2.5 concentrations during
severe haze days range from 6.0 to 12.9 µg m−3 (<6 %).
Sensitivity simulations indicate the important effect of aerosol mixing
states on the estimates of ADRF and aerosol feedbacks. Besides, black carbon (BC) exhibits
a large contribution to atmospheric heating and feedbacks although it accounts
for a small share of mass concentration of PM2.5.
Despite the significant progress in improving chemical transport models (CTMs), applications of these modeling endeavors are still subject to large and complex model uncertainty. The Model ...Inter-Comparison Study for Asia III (MICS-Asia III) has provided the opportunity to assess the capability and uncertainty of current CTMs in East Asian applications. In this study, we have evaluated the multi-model simulations of nitrogen dioxide (NO2), carbon monoxide (CO) and ammonia (NH3) over China under the framework of MICS-Asia III. A total of 13 modeling results, provided by several independent groups from different countries and regions, were used in this study. Most of these models used the same modeling domain with a horizontal resolution of 45 km and were driven by common emission inventories and meteorological inputs. New observations over the North China Plain (NCP) and Pearl River Delta (PRD) regions were also available in MICS-Asia III, allowing the model evaluations over highly industrialized regions. The evaluation results show that most models captured the monthly and spatial patterns of NO2 concentrations in the NCP region well, though NO2 levels were slightly underestimated. Relatively poor performance in NO2 simulations was found in the PRD region, with larger root-mean-square error and lower spatial correlation coefficients, which may be related to the coarse resolution or inappropriate spatial allocations of the emission inventories in the PRD region. All models significantly underpredicted CO concentrations in both the NCP and PRD regions, with annual mean concentrations that were 65.4 % and 61.4 % underestimated by the ensemble mean. Such large underestimations suggest that CO emissions might be underestimated in the current emission inventory. In contrast to the good skills for simulating the monthly variations in NO2 and CO concentrations, all models failed to reproduce the observed monthly variations in NH3 concentrations in the NCP region. Most models mismatched the observed peak in July and showed negative correlation coefficients with the observations, which may be closely related to the uncertainty in the monthly variations in NH3 emissions and the NH3 gas–aerosol partitioning. Finally, model intercomparisons have been conducted to quantify the impacts of model uncertainty on the simulations of these gases, which are shown to increase with the reactivity of species. Models contained more uncertainty in the NH3 simulations. This suggests that for some highly active and/or short-lived primary pollutants, like NH3, model uncertainty can also take a great part in the forecast uncertainty in addition to the emission uncertainty. Based on these results, some recommendations are made for future studies.
In this study, the spatial pattern and temporal evolution of PM2.5 over North China Plain (NCP) and Northeast China (NEC) during 2014–2018 was investigated. The annual mean PM2.5 shows clear ...decreasing trends over time, but the seasonal mean PM2.5 as well as the seasonal total duration and frequency of haze days shows large inter-annual fluctuation. Based on the atmospheric stagnation index (ASI), this study examined the correlation between ASI and haze events over NCP and NEC. Detailed analysis indicates that location dependency exists of ASI in the capability of capturing the haze events, and the ability is limited in NCP. Therefore, we first propose two alternative methods in defining the ASI to either account for the lag effect or enlarge the threshold value of wind speed at 500 hPa. The new methods can improve the ability of ASI to explain the haze events over NEC, though marginal improvement was achieved in NCP. Furthermore, this study constructed the equation based on the boundary layer height and wind speed at 10-meter, apparently improving the ability in haze capture rate (HCR), a ratio of haze days during the stagnation to the total haze days. Based on a multi-model ensemble analyses under Representative Concentration Pathway (RCP) 8.5, we found that by the end of this century, climate change may lead to increases in both the duration and frequency of wintertime stagnation events over NCP. In contrast, the models predict a decrease in stagnant events and the total duration of stagnation in winter over NEC.
•Large variability exists in seasonal mean PM2.5 and haze duration and frequency.•The feasibility of the atmospheric stagnation index (ASI) varies by location.•In future, the climate models predict a decrease of stagnation in Northeast China.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In order to clarify the causes of variability among the model outputs for
surface ozone in the Model Intercomparison Study Asia Phase III (MICS-Asia III),
three regional models, CMAQ v.5.0.2, ...CMAQ v.4.7.1, and NAQPMS
(abbreviated as NAQM in this paper), have been selected. Detailed analyses of
monthly averaged diurnal variation have been performed for selected grids
covering the metropolitan areas of Beijing and Tokyo and at a remote oceanic
site, Oki. The chemical reaction mechanism, SAPRC99, used in the CMAQ models
tended to give a higher net chemical ozone production than CBM-Z used in
NAQM, agreeing with previous studies. Inclusion of the heterogeneous
“renoxification” reaction of HNO3 (on soot surface)→NO+NO2
only in NAQM would give a higher NO concentration resulting in a
better agreement with observational data for NO and nighttime O3 mixing
ratios. In addition to chemical processes, the difference in the vertical
transport of O3 was found to affect the simulated results significantly.
Particularly, the increase in downward O3 flux from the upper layer to
the surface after dawn was found to be substantially different among the
models. Larger early morning vertical transport of O3 simulated by CMAQ 5.0.2
is thought to be the reason for higher daytime O3 in July in this
model. All three models overestimated the daytime ozone by ca. 20 ppbv at
the remote site Oki in July, where in situ photochemical activity is minimal.
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