Winter Transport Research Articles

An environmental and techno-economic analysis of transporting LNG via Arctic route

The Northern Sea Route (NSR) might be a promising route for LNG transportation from the LNG plants in Russia’s Yamal Peninsula to Northeast Asia countries with significant savings in sailing distance and time compared to traditional Suez Canal Route (SCR). However, surging transportation activities along NSR might harm the environment with the greenhouse gas (GHG) and atmospheric pollutant emissions. Little research has been done to investigate the environmental and techno-economic potential of transporting LNG via NSR. Furthermore, this paper analyses the relevance of an Arc4 ice-class vessel, not currently used for this route. This paper targets to address the question that how much GHGs and atmospheric pollutants does a carrier emit and how is the feasibility of different fuel types for the summer and winter transportation considering environmental impacts. An environmental and techno-economic model quantifying the emissions and total costs have been developed and 3 scenarios of using different fuel types (HFO, MDO, LNG) are proposed to investigate the environmental and economic performances in summer and winter respectively. Our results reveal that the unit cost of transporting LNG via NSR is around 90 U.S. $ cents/GJ in summer and 120 $ cents/GJ in winter considering environmental cost. The findings also show that in the short run when regardless of environmental cost, HFO is still the preferable option for ships by its competitive cost. While when considering the environmental cost, LNG has better economic and environmental performance than other fuel types. So, for the long run, LNG might be encouraged to be the main fuel used in Arctic.

December-March temperature reconstruction from tree-ring earlywood width in southeastern China during the period of 1871-2016.

Extremely cold temperatures are a significant threat to agriculture and transportation in winter in southeastern China. However, due to the shortness of instrumental records and the scarcity of long-term temperature reconstructions, more high-quality temperature reconstructions are still needed to fully examine their spatial-temporal variability over the past several centuries. In this study, we built an earlywood width (EWW) chronology, a latewood width (LWW) chronology, and a tree-ring width (TRW) chronology using tree-ring samples of Pinus taiwanensis Hayata from the western Tianmu Mountains and the Xianyu Mountains in southeastern China. The tree growth-climate relationships were analyzed, and we found the strongest correlation between December and March mean temperature and the EWW chronology. The December-March mean temperature history was then reconstructed over the period of 1871-2016 using a linear regression model, which is the first EWW-based temperature reconstruction in southeastern China. With a higher explained variance (47.0%) than that (31.7%) of a previous reconstruction using a TRW chronology, the quality of the model has largely improved. This reconstruction was also comparable with other nearby records, further demonstrating the reliability of our new model. Furthermore, our reconstruction exhibits a significantly negative relationship with the East Asian winter monsoon index (EAWMI) since the 1920s, which may be attributed to the obviously enhanced EAWMI thereafter.

SIMULATION OF THE AUTUMN-WINTER RUNOFF OF THE ANADYR RIVER

. Runoff during the autumn-winter low-water period is of great importance in the life of river ecosystems. In this work, the goal is to construct a mathematical model of the curves of daily water discharge during the autumn-winter low-water period (September-April) on the Anadyr River near the village Snezhny (catchment area 106 000 km2 ). Anadyr River is the largest waterway of the Chukotka. The river is used by public utilities, river transport in summer and road transport in winter. Pacific salmon spawn in this river every year. The conditions for the survival of salmon eggs in winter are influenced by the water content of the rivers. The basin under consideration is located in a zone of subarctic climate and continuous permafrost. Therefore, the autumn-winter low-water period on the Anadyr River lasts from September to April during this period, 4–6 % of the annual runoff occurs. Based on the average annual monthly water discharges for September-April, the averaged runoff depletion curve was calculated in relative ordinates, which is approximated by an exponential function. Based on this curve, you can predict daily water discharges from September 15th to April 15th of the following year. Verification calculations for the years of winters with different water content showed that the mathematical model works satisfactorily. Based on the data on the runoff of other hydrological stations in the Anadyr catchment, the study can be continued to derive a basin formula, which can be used to predict the daily water discharges of the autumn-winter low-water period on any unexplored river.

Картографирование сезонной автотранспортной доступности Арктического региона России

Transport accessibility is one of the main categories in transport research and planning of socio-economic development of territories. For Russia, which has the largest area of the northern and arctic territories, this problem is especially urgent. The presence and condition of the road network determines the territorial integrity and unity of the economic space, therefore fulfilling the most important strategic task of the spatial integration of the country. Automobile transport in the Arctic zone of the Russian Federation is poorly developed and is characterized by a low density of the public network. Its main features are the disunity of the road network, the heterogeneous degree of transport development of the territories and the noticeable role of winter roads in the road infrastructure. An integral part of the transport logistics of the Arctic regions of Russia are winter roads, which allow transportation in the winter season at the lowest cost. The purpose of this study is to develop a database structure and thematic mapping of automobile roads in the Arctic zone of the Russian Federation, taking into account the seasonality of their operation. As a result of this work, a classification of winter automobile roads and ice crossings of the Arctic territories was developed and an overview map “Seasonal road transport accessibility of the Arctic region of Russia” at a scale of 1:20,000,000 was compiled. The map demonstrates the contrast between the relatively good winter transport development of the territory and summer impassability. On the basis of statistical materials, maps “Density of all-season motorable roads” and “Level of motorization” were compiled, which give an idea of the differentiation of the regions of the Arctic zone of the Russian Federation by these indicators. A high level of motorization significantly exceeds the capacity of the existing roads. This is due to the fact that off-road transport is the only guarantor of mobility for the population of hard-to-reach settlements.

Molecular Distributions of Diacids, Oxoacids, and α‐Dicarbonyls in Summer‐ and Winter‐Time Fine Aerosols From Tianjin, North China: Emissions From Combustion Sources and Aqueous Phase Secondary Formation

AbstractTo understand the characteristics and sources of organic aerosols (OA) in North China, we studied diacids, oxoacids, and α‐dicarbonyls in summer‐ and winter‐time fine aerosols (PM2.5) collected from Tianjin. Oxalic (C2) acid was found to be the most abundant diacid species, followed by succinic (C4), malonic (C3), and sebacic (C8) acids, respectively. Glyoxylic (ωC2) was the most abundant oxoacids followed by pyruvic acid. Concentrations of total diacids, oxoacids, and α‐dicarbonyls in winter were 2–3 times higher than those in summer, but their mass fractions in PM2.5 were exactly the opposite. On average, total diacids carbon accounted for 2.9% in total carbon and 3.3% in organic carbon (OC) in summer and 1.8% and 2.0%, respectively, in winter. Their contributions to water‐soluble OC (WSOC) was almost the same in both seasons (5.5% and 5.3%, respectively). Molecular distributions, mass ratios of selected diacid (C3, C4, M, F, C6, Ph, and C9) species, and the linear relations among the selected species (including ∑C2–C4 and ∑C8–C12) and with inorganic markers (K+ and SO42−) implied that the diacids and related compounds are mainly originated from coal combustion and biomass burning emissions and produced in the atmosphere by both in situ photochemical reactions at local scale and aging during long‐range transport in both summer and winter. This study revealed that diacids and related compounds and WSOC are increased with increasing SO42− and they are produced in the aqueous phase, implying that the reduction in NOx and SO2 emissions could possibly control the water‐soluble OA loading over North China.

Temporal characteristics of carbon dioxide and ozone over a rural-cropland area in the Yangtze River Delta of eastern China

In this study, rural atmospheric carbon dioxide (CO2) and ozone (O3) were measured from January 2015 to December 2018 to investigate characteristics of greenhouse gases in eastern China. Results showed that the annual average CO2 (O3) concentration in 2018 decreased by 2% (increased by 19%) when compared with that in 2015. CO2 concentrations exhibited monthly variability, peaking in February (443.7 ppm) and reaching their lowest levels in July (363.0 ppm); whereas, monthly O3 showed a bimodal pattern with peaks in June (51.3 ppb) and September (34.5 ppb). Regarding the diurnal variation, the maximum CO2 (O3) concentration occurred at nighttime (in the daytime) and a minimum CO2 (O3) in the daytime (at nighttime). As demonstrated by correlation analysis, CO2 and O3 variations were partly modulated by NOx and PM2.5. Furthermore, CO2 showed significant positive correlations with relative humidity in winter, while O3 showed strong positive correlations with temperature in spring. CO2 was accumulated from local sources under calm conditions (< 2 m s−1) and derived from remote sources at high wind speeds (> 4 m s−1), while O3 concentrations were peaking at medium wind speeds of 2–4 m s−1. CO2 was found to derive from long-distance (short-distance transport) transport in spring (the other three seasons), whereas O3 is mainly from long-distance (short-distance) transport in winter (the other three seasons). This work sheds light on the temporal characteristics of CO2 and O3, which has important implications for implementing practices to mitigate source emissions over cropland areas.

Kuroshio intrusion in the Luzon Strait in an eddy-resolving ocean model and air-sea coupled model

The Kuroshio intrusion in a quasi-global eddy-resolving model (LICOMH) and a fully air-sea coupled model (LICOMHC) was evaluated against observations. We found that the Kuroshio intrusion was exaggerated in the former, while biases were significantly attenuated in the latter. Luzon Strait transport (LST) in winter was reduced from −8.8×106 m3/s in LICOMH to −6.0×106 m3/s in LICOMHC. Further analysis showed that different LST values could be explained by different large-scale and local surface wind stresses and the eddies east to the Luzon Strait as well. The relatively stronger cyclonic eddies in LICOMH northeast of the Luzon Island led to weak Kuroshio transport and strong intrusion through the Luzon Strait. The summed transport of all three factors was approximately 2.0×106 m3/s, which was comparable with the difference in LST between the two experiments. The EKE budget showed that strong EKE transport and the baroclinic transformation term led to strong cyclonic eddies east of the Kuroshio in LICOMH, while surface winds contributed little to the differences in the eddies.

Predictors of public transport use among university students during the winter: A MIMIC modelling approach

The current study aimed to examine attitudinal factors underlying the use of public transport in winter among university students. A self-administered questionnaire survey was conducted among 441 students at the two largest university campuses in Trondheim, Norway. A Multiple Indicators Multiple Causes (MIMIC) modelling approach was used to test relationships among constructs using an extended version of the theory of planned behaviour hypothesized to predict public transport use during the winter. Analyses revealed strong effects of social-normative influence and perceived behavioural control on the use of public transport. Social status attribution and perceived accident involvement probability had significant influences on the attitude. The findings suggest that campaigns promoting sustainable and environmentally friendly travel modes can benefit from highlighting the above factors while bearing in mind the demographic characteristics of the target population.

Spatial Distributions of Nitric Oxide in the Antarctic Wintertime Middle Atmosphere During Geomagnetic Storms

AbstractEnergetic electron precipitation leads to increased nitric oxide (NO) production in the mesosphere and lower thermosphere. NO distributions in the wintertime, high‐latitude Southern Hemisphere atmosphere during geomagnetic storms are investigated. NO partial columns in the upper mesosphere at altitudes 70–90 km and in the lower thermosphere at 90–110 km have been derived from observations made by the Solar Occultation For Ice Experiment (SOFIE) on board the Aeronomy of Ice in the Mesosphere (AIM) satellite. The SOFIE NO measurements during 17 geomagnetic storms in 2008–2014 have been binned into selected geomagnetic latitude and geographic latitude/longitude ranges. The regions above Antarctica showing the largest instantaneous NO increases coincide with high fluxes of 30–300 keV precipitating electrons from measurements by the second‐generation Space Environment Monitor (SEM‐2) Medium Energy Proton and Electron Detector (MEPED) instrument on the Polar‐orbiting Operational Environmental Satellites (POES). Significant NO increases over the Antarctic Peninsula are likely due to precipitation of &gt;30 keV electrons from the radiation belt slot region. NO transport is estimated using Horizontal Wind Model (HWM14) calculations. In the upper mesosphere strong eastward winds (daily mean zonal wind speed ~20–30 m s−1 at 80 km) during winter transport NO‐enriched air away from source regions 1–3 days following the storms. Mesospheric winds also introduce NO‐poor air into the source regions, quenching initial NO increases. Higher up, in the lower thermosphere, weaker eastward winds (~5–10 m s−1 at 100 km) are less effective at redistributing NO zonally.

Analysis of aerosol optical properties in a Lanzhou suburb of China

In order to accurately identify feature layer and monitor the spatial and temporal distribution of pollutants, the inversion method of lidar measurement based on multiscale algorithm is proposed in this paper. The detection of clouds, aerosols and dust layers using a modified retrieval algorithm for a dual-wavelength lidar is presented at the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL). Moreover, the aerosol optical depth calculated from the Klett-Fernald algorithm obviously excludes the influence of clouds. Two cases were presented to demonstrate that the modified algorithm can capture low-clouds and dust layers well. The aerosol optical properties including aerosol optical depth (AOD), effective radius, depolarization ratio and black carbon aerosol mass concentration are analysed in terms of their monthly and seasonal variations. It is shown that the maximum of AOD, depolarization ratio and effective radius were found in spring (0.42 ± 0.35, 0.17 ± 0.1, 0.63 ± 0.24 μm) and the minimums were found in summer and autumn. The black carbon aerosol mass concentration varies significantly throughout year, with the maximum value in winter (2.35 ± 1.56 μg m−3) and a secondary maximum in autumn (1.93 ± 1.28 μg m−3), a minimum (1.03 ± 0.76 μg m−3) in spring. The vertical distribution of extinction coefficient has a peak near 1 km (0.1 km−1). The depolarization ratio vertically distributes at approximately 0.15. In general, pollution is more serious in spring and winter at SACOL, the former pollutants are coarse-mode non-spherical dust particles which originate from the Taklimakan Desert and the Gobi Desert, and the latter are fine mode spherical black carbon aerosols and coarse-mode non-spherical dust aerosols which are the results of both local combustion and long-distance transport. The dust particles existed high-altitude transport in spring and winter at SACOL.

Norwegian Atlantic Slope Current along the Lofoten Escarpment

Abstract. Observations from moored instruments are analyzed to describe the Norwegian Atlantic Slope Current at the Lofoten Escarpment (13∘ E, 69∘ N). The data set covers a 14-month period from June 2016 to September 2017 and resolves the core of the current from 200 to 650 m depth between the 650 and 1500 m isobaths. The along-isobath current, vertically averaged between 200 and 600 m depth, has an annual cycle amplitude of 0.1 m s−1, with the strongest currents in winter, and a temporal average of 0.15 m s−1. Higher-frequency variability is characterized by fluctuations that reach 0.8 m s−1, lasting for 1 to 2 weeks, and extend as deep as 600 m. In contrast to observations in Svinøy (2∘ E, 63∘ N), the slope current is not barotropic and varies strongly with depth (a shear of 0.05 to 0.1 m s−1 per 100 m in all seasons). Within the limitations of the data, the average volume transport of Atlantic Water is estimated at 2.0±0.8 Sv (1 Sv =106 m3 s−1), with summer and winter averages of 1.6 and 2.9 Sv, respectively. The largest transport is associated with the high temperature classes (&gt;7 ∘C) in all seasons, with the largest values of both transport and temperature in winter. Calculations of the barotropic and baroclinic conversion rates using the moorings are supplemented by results from a high-resolution numerical model. While the conversion from mean to eddy kinetic energy (e.g., barotropic instability) is likely negligible over the Lofoten Escarpment, the baroclinic conversion from mean potential energy into eddy kinetic energy (e.g., baroclinic instability) can be substantial, with volume-averaged values of (1–2)×10-4 W m−3.

Regional transport in Beijing-Tianjin-Hebei region and its changes during 2014–2017: The impacts of meteorology and emission reduction

Emissions of air pollutants have been dramatically reduced in the Beijing-Tianjin-Hebei (BTH) region of China during 2014–2017. However, impacts of emission reduction on regional air quality are not well quantified. This study evaluates the impacts of emission reduction and inter-annual meteorological conditions on regional air pollution transport in BTH region by employing Community Multiscale Air Quality model embedded with the Integrated Source Apportionment Model (CMAQ-ISAM). Results suggest that the regional transport contributed 32.5%–68.4% of total PM2.5 mass concentrations and 52.4%–83.2% of sulfate, nitrate and ammonium in 2017. During 2014–2017, the annual averaged PM2.5 concentrations in BTH region decreased by 33%, of which the decrease of local emissions, inter-regional transport and transport from outside the BTH region contributed for 47%, 25%, and 28%, respectively. Emission reductions (91%) mitigate not only the impacts of local sources, but also influence the regional transport with similar magnitude, demonstrating the effectiveness of multiple regional joint controls. The variation of meteorology contributes only 9% to the decrease of PM2.5 in BTH, with higher contributions from the change of regional transport compared to local sources since the regional transport is more sensitive to the meteorology variation. The impacts of meteorological variations are considerable, with over 20% on the relative changes of local and regional contributions, and up to 40% on regional transport in spring and winter. Therefore, more strengthened regional joint air pollution control is suggested in winter and spring for this region.

Chemical characteristics, sources and evolution processes of fine particles in Lin’an, Yangtze River Delta, China

In this study, daily PM2.5 mass and chemical composition were measure in Lin’an Reginal Background Station, Yangzte River Delta, from March 1, 2018, to February 28, 2019. Organic matter (OM) was found to be the most dominant component in four seasons. The proportions of nitrate in PM2.5 presented dramatically lowest in warm seasons but highest in winter, indicating that NO3− was maily driven by thermodynamics. Regional transportation in winter plays a strong impact on PM2.5 concentration, which showed the highest average mass of 60.1 μg m−3. Sulfate occupied a significant portion of PM2.5 in summer (19%), followed by spring (17%), fall (15%), and winter (12%), respectively, suggesting photochemical processes may play a dominant role in the sulfate formation. Secondary inorganic aerosol (SIA) was the dominant component (70%) in the highest polluted periods (PM2.5 > 75 μg m−3), whereas OM decreased into the lowest fraction (22%) of PM2.5. Nitrate was the most important component in SIA in the highest polluted periods with regarding winter. Source apportionment results shown that winter haze was likely strongly dominated by SIA, which was mainly affected by air masses from the North China Plain and Shang-Hangzhou direction. PM2.5 is known to play an important role in sunlight absorption and reversing to human health, continuous observation on PM2.5 species in a background site can help us to evaluate the control policy, and promote our insights to lifetime, formation pathways, health effects of PM2.5.

Совершенствование эксплуатационного менеджмента зимнего содержания транспортных сооружений методами математического моделирования

Совершенствование эксплуатационного менеджмента зимнего содержания транспортных сооружений методами математического моделирования

Meat Quality and Cooking Characteristics in Broilers Influenced by Winter Transportation Distance and Crate Density.

A study was conducted to determine the effect of transportation distance and crating density on meat quality traits during winter. ROSS-308 broilers aged 35 days were divided into 10 treatment groups based on three transportation distances (80, 160, and 240 km) with three crating densities (10, 12, and 15 birds per crate) along with birds slaughtered on farm without crating as a control group. Each treatment was replicated 10 times and placed at various locations in the truck. The birds were transported in plastic crates of 0.91 m×0.55 m×0.30 m at ambient temperature and relative humidity of 3.6–9.5°C and 63.3–78.8%, respectively. The breast meat quality parameters including pH, color, drip loss, shear force, marinade uptake and retention, cooking losses, and yield were determined. The results showed significantly higher pH 15 min post-slaughter (PS), drip loss, lightness, marinade uptake, raw meat cooking yield, and shear force in birds slaughtered on farm without any transportation. The birds transported for 240 km had significantly higher pH at 2 hours (h) PS, marinade retention, and cooking yield. Whereas, pH at 24 h PS, meat redness, yellowness, chroma, and marinated meat cooking yield were significantly higher in all transported treatments compared to the control group. Among different crating densities, the birds transported with 10 birds per crate showed significantly higher meat redness, marinade retention, and cooking yield. The crating density of 15 birds per crate had significantly higher lightness, hue, cooking loss, and shear force. However, no effect of crating density was observed on meat pH, drip loss, and marinade uptake. It can be concluded that an increase in transportation distance and low crating density during winter can negatively affect physical quality of meat with significant improvement in marination and cooking characteristics.

Evolution From Past to Future Conditions of Fast Ice Coverage in James Bay

Fast ice is often used by coastal communities in the James Bay area for transportation in winter using snowmobiles. Therefore, the extent of fast ice along the James Bay coastline is important for land use and any changes to these extents may have significant impacts on the lifestyles of local communities. The eastern coastline has experienced changes in recent decades that might have affected the ice processes, namely hydrologic modifications due to hydroelectric development by Hydro-Québec along with climatic changes that have been observed worldwide. A statistical analysis in the form of summarized ice charts of the ice extents in the middle of winter have been compiled for the past four decades to highlight any recent changes in ice coverage using data from satellite imagery and ice charts produced by the Canadian Ice Service. A statistical analysis has also been carried out on the freeze-up and breakup dates using historical data. Moreover, a statistical analysis of hydrological data and climatic data has been carried out to determine the long-term and short-term trends in the parameters influencing the ice processes. After testing sensitivity of the past ice regime to climatic and hydrological parameters, the trends detected in the extents of fast ice, as well as freeze-up and breakup conditions, have been correlated with climatic parameters. Using the dominant parameters, a simplified model of the extents of fast ice has been developed, as well as criteria to determine freeze-up and breakup dates. Air temperature projections have also been obtained for two greenhouse gas emissions scenarios using global climate model results to establish future climatic conditions. Finally, projections of the fast ice regime around the year 2050 have been developed to determine a long-term trend covering both historical changes and future conditions. We expect around the year 2050 a recession of the landfast ice coverage of several kilometers, a delay of one to three weeks of the freeze-up dates and an advance of two to ten days of the breakup dates in comparison to the period of 1998-2016 in the James Bay area.

Wintertime photosynthesis and spring recovery of Ilex aquifolium L.

Abstract: Former studies using the chlorophyll fluorescence technique on evergreen Ilex aquifolium L. showed that its photosynthetic potential for electron transport in winter recovers quickly when exposed to more favorable conditions. Since little is known, however, about its photosynthetic carbon gain in winter, we investigated its leaf gas exchange over an entire winter and spring period. Measurements were made rotationally in the field and in the laboratory to also investigate if I. aquifolium profits from warmer phases during winter in terms of net carbon gain. From the end of autumn until the end of spring, three different climate-driven phases of photosynthetic responses could be distinguished: first, an acclimation phase which lasted until February and was characterized by a gradually decreasing light-saturated gross photosynthesis (Amax(gross)), decreasing apparent quantum yield of CO2-assimilation (ΦΦi) and a decreasing ability of these parameters to recover overnight inside the laboratory. At the same time, maximal quantum yield of PSII (Fv/Fm) could fully regenerate. In this phase, single warmer days had a positive effect on carbon assimilation. Second, a phase of relatively constant but low photosynthesis which was virtually unaffected by temperature, lasting for almost two months occurred. Here, Amax(gross) and Φi had lost their ability to recover from winter conditions in the field, while Fv/Fm was much less affected. I. aquifolium was still able to conduct positive light-saturated net photosynthesis at a leaf temperature of -0.5 °C, but during this time it could not profit from milder temperatures in terms of carbon gain. Third, a phase of increasing photosynthesis (spring recovery) occurred, starting in March when the 5-day average temperature was above 5 °C and radiation in the field increased, and where all parameters slowly recovered from winter depressions. Our findings show that I. aquifolium is photosynthetically active over the whole winter, even at temperatures around 0 °C. In terms of carbon gain, however, I. aquifolium does not profit from warmer phases during winter, despite the fast recovery seen in chlorophyll fluorescence measurements.

Study on the contribution of transport to PM2.5 in typical regions of China using the regional air quality model RAMS-CMAQ

Regional transport plays a significant role in the air pollution in China, which is characterized by diverse emission sources and distinct distributions. To improve the understanding of factors determining the PM2.5 level in China, a source apportionment tool coupled with the RAMS-CMAQ model (CMAQ-ISAM) was used to quantify the contribution of transport to PM2.5 and its major components during 2017 in the North China Plain (NCP), Yangtze River Delta (YRD), Pearl River Delta (PRD), and Chengyu area. It is found that transport accounts for a predominant fraction of the PM2.5 in Beijing, Tianjin, and Shanghai with relatively low PM2.5 levels. Transport in the NCP is mainly at intraregional scale and comparable to local emissions. In contrast, the contributions of interregional transport from the NCP to the YRD (~10–25%) and from NCP and YRD to PRD and Chengyu (~5–25%) is at similar level to those of intraregional transport and local emissions in winter and fall, but are lower in spring and summer. It is worth noting that particle components have very different transport capabilities. Nitrate exhibits much stronger intraregional transport than other components in the NCP, and much higher concentration than other components during winter. In contrast, the concentration of sulfate is higher than that of nitrate during spring and summer in most provinces. In addition, the transport potential of primary OC, EC, and ammonia are relatively weaker, but these compounds can still have considerable contributions. Our results reveal that the notable contributions of regional transport to PM2.5 should be addressed according to targeted emission sources in order to improve air quality efficiently.

Source estimation of SO42− and NO3− based on monitoring-modeling approach during winter and summer seasons in Beijing and Tangshan, China

SO42−, NO3− and NH4+ are the important components of PM2.5 in China. This study developed a modeling-monitoring coupled approach to determining the sources of SO42− and NO3− as well as the secondary oxidation ratio of SO2 to SO42−, through a monitoring of PM2.5 in Beijing and Tangshan, and a WRF-CAMx simulation over North China. Measurement showed that the concentrations of NO3−, SO42− and NH4+ in winter (summer) were 24.2 ± 25.2 μg/m3 (5.1 ± 2.9 μg/m3), 17.5 ± 18.5 μg/m3 (5.8 ± 3.7 μg/m3) and 14.5 ± 14.1 μg/m3 (4.7 ± 2.9 μg/m3) in Beijing, while 12.2 ± 11.0 μg/m3 (13.3 ± 4.5 μg/m3), 15.8 ± 11.9 μg/m3 (14.3 ± 4.9 μg/m3) and 14.6 ± 13.0 μg/m3 (9.6 ± 3.7 μg/m3) in Tangshan. CAMx-PSAT simulation showed that the concentrations of SO42− in Beijing was affected more by regional transport. In Tangshan, local SO2 was the main source of SO42−. As for NO3−, both cities were affected more by regional transport in both winter and summer. Sulfate/nitrate aged ratio (SAR and NAR) and sulfate oxidation ratio (SOR) calculated by the coupling approach stated above could reflect the regional and local atmospheric oxidation capacity respectively. The NAR in Beijing were 0.13 ± 0.08 in winter and 0.09 ± 0.06 in summer, 0.08 ± 0.05 and 0.15 ± 0.05 in Tangshan. The SAR were 0.32 ± 0.17 and 0.51 ± 0.17 in Beijing, 0.13 ± 0.11 and 0.19 ± 0.11 in Tangshan. Then, we further designed several scenarios in CAMx to differentiated the SO42− converted from outside SO2 in the studied city from that in outside areas, and to further evaluated the SOR. It was 0.22 ± 0.15 and 0.23 ± 0.11 in winter and summer in Beijing, and 0.11 ± 0.10 and 0.14 ± 0.08 in Tangshan. It implies a stronger atmospheric oxidation ability in Beijing compared with Tangshan, and the impact of regional transport of sulfur pollutants on Beijing is much more obvious. Moreover, the correlation coefficient between RH and SOR was 0.94 and 0.93 in winter, 0.05 and 0.17 in summer in two cities. It indicates that SO42− is transformed mainly through liquid-phase and heterogeneous reaction in winter and gaseous reaction in summer.

Spectral Decomposition and Extremes of Atmospheric Meridional Energy Transport in the Northern Hemisphere Midlatitudes

AbstractThe atmospheric meridional energy transport in the Northern Hemisphere midlatitudes is mainly accomplished by planetary and synoptic waves. A decomposition into wave components highlights the strong seasonal dependence of the transport, with both the total transport and the contributions from planetary and synoptic waves peaking in winter. In both winter and summer months, poleward transport extremes primarily result from a constructive interference between planetary and synoptic motions. The contribution of the mean meridional circulation is close to climatology. Equatorward transport extremes feature a mean meridional equatorward transport in winter, while the planetary and synoptic modes mostly transport energy poleward. In summer, a systematic destructive interference occurs, with planetary modes mostly transporting energy equatorward and synoptic modes again poleward. This underscores that baroclinic conversion dominates regardless of season in the synoptic wave modes, whereas the planetary waves can be either free or forced, depending on the season.