Hybrid Single-Particle Lagrangian Integrated Trajectory Model Research Articles

Effect of oasis and irrigation on mountain precipitation in the northern slope of Tianshan Mountains based on stable isotopes

Water is one of the scarcest resources in arid regions, and irrigation is an important means to improve crop yield and ensure food security. The Xinjiang features an integrated irrigation agriculture and oasis economy paradigm. However, the understanding of the impact mechanism and quantitative analysis of irrigation on precipitation is inadequate now. With the aim of clarifying the response relationship between mountain precipitation and irrigation in oasis, we clarify and quantify the moisture sources of precipitation using the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model and multisource data (including field-collected isotopes data, C-Isoscape, ERA5, and GDAS). The results obtained show: (1) Isotope analysis provides valuable insights into the climate background and precipitation recycling. The Local Meteoric Water Line's lower slope and intercept than Global Meteoric Water Line suggest a severe arid climate and strong sub-cloud evaporation. The intercept (13.44) of Local Meteoric Water Line in Mountain Areas exceeds the global average, indicating significant moisture recycling in mountain areas (MA). The d-excess in MA is prominent year-round, highlighting the influence of recycled moisture. (2) The oasis and irrigation influence the local precipitation through offset, remote, combination, and delayed effects. The offset effect hinders precipitation formation in irrigation areas (IA) due to the counteracting irrigation-induced humidification and cooling effect. Through the interaction of westerly circulation and local mountain-oasis hydrological cycle, irrigation-induced moisture is transported to MA and uplifted, which is remote effect. The combination effect synergistically enhances precipitation intensity, especially in intricate MA, through the combined influence of terrain's forced uplift and convective cells. Furthermore, the mountainous precipitation influenced by the mountain-oasis hydrological cycle often exhibits a delayed effect. (3) Based on HYSPLIT model tracking results, the contribution ratio of oasis and irrigation induced evapotranspiration to summer precipitation in MA is approximately 19.60%, ranging from 13.68% to 28.49%. The findings provide insights into the mechanisms of irrigation and water resource management in the northern slope of Tianshan Mountains.

Investigating the Role of the Low-Level Jet in Two Winters Severe Dust Rising in Southwest Iran

The dust storms with local and non-local dust sources mostly affect Khuzestan province in southwest (SW) Iran. In this study, the role of the low-level jet in the activation of the internal dust events in SW Iran during two severe dust cases was investigated. For this purpose, the fifth-generation ECMWF reanalysis for the global climate and weather (ERA5) data was used to identify the synoptic patterns and the low-level jet (LLJ) characteristics in the study area. Furthermore, the images of the moderate resolution imaging spectroradiometer (MODIS) sensor, the outputs of the hybrid single-particle Lagrangian integrated trajectory (HYSPLIT) model, and a weather research and forecasting model coupled with chemistry (WRF-Chem) were used to investigate the propagation and transport of the dust particles. The results of the synoptic analysis in both dust cases show the simultaneous occurrence of the divergence zone associated with cyclonic curvature in the subtropical jet stream (STJ) at 300 hPa, causing convergence at 925 hPa, upward motion, and the development of low surface pressure in SW Iran. Examining the vertical wind profile shows the existence of the maximum horizontal wind speeds of 975 to 875 hPa, along with the positive and negative shear below and above it, respectively, which emphasizes the existence of the LLJ and its role in local dust emission. The results of the comparison between the satellite images, WRF-Chem, and HYSPLIT model outputs show the formation and transportation of dust particles from the inner regions of Khuzestan in SW Iran. The horizontal dust surface distribution, vertical raised dust mass, and kinetic energy transfers are well simulated by the WRF-Chem model when LLJ broke at 09:00 to 12:00 UTC. The most important finding of this research is that, for the first time, the role of low-level jet is investigated in the activation of internal dust events in SW Iran.

Combined use of HYSPLIT model and MODIS aerosols optical depth to study the spatiotemporal circulation patterns of Saharan dust events over Central Europe

Mineral dust released from the desert region and transported into the atmosphere has a crucial impact on the Earth's climate system's biogeochemical cycle. It has serious adverse effects on human health. The Sahara is one of the world's dustiest areas. This investigation intends to uncover the underlying reasons for atmospheric dust dispersion throughout the year by tracking the dusttransport and deposition in Central Europe, focusing on arid areas of North Africa. In this paper, we use the GDAS (Global Data Assimilation System) archival meteorological database to compute the analytical forward trajectories and configure the particle concentrations using the HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) model. Besides, we investigate the synoptic meteorological conditions of acute Saharan dust episodes to determine the dynamic atmospheric system during their onset. The forward trajectories reveal the seasonality of wind-blown dust throughout the year. Dust storms are typically more prevalent in the spring, with a second peak in the Summer. As a result, particle transport takes various paths as the seasons and climatic conditions change. The most dust-laden masses, which reach high altitudes from the source areas, are often transported to Central Europe, where their seasonal distribution is relatively similar to that of the studied African region. However, the intensity and frequency of Saharan dust events (SDEs) have significantly changed in the previous decades, with an increased number of intense winter storms. According to the synoptic analysis, this variability is strongly linked to two factors. (1) The intensity and lifetime variation of the Mediterranean cyclones and (2) Climate change triggered lee-side (Sharav) cyclogenesis modified by the topographic complexity of Atlas. This study also confirmed the effectiveness of the HYSPLIT model in simulating atmospheric dust after comparing it with annual aerosol optical depth measurements from MODIS (Moderate-Resolution Imaging Spectroradiometer) data.

Exploring Spatial and Temporal Dynamics of Red Sea Air Quality through Multivariate Analysis, Trajectories, and Satellite Observations

The Red Sea, a significant ecoregion and vital marine transportation route, has experienced a consistent rise in air pollution in recent years. Hence, it is imperative to assess the spatial and temporal distribution of air quality parameters across the Red Sea and identify temporal trends. This study concentrates on utilizing multiple satellite observations to gather diverse meteorological data and vertical tropospheric columns of aerosols and trace gases, encompassing carbon monoxide (CO), nitrogen dioxide (NO2), sulfur dioxide (SO2), and ozone (O3). Furthermore, the study employs the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model to analyze the backward trajectory of air mass movement, aiding in the identification of significant sources of air pollutants. A principal component analysis (PCA) with varimax rotation is applied to explore the relationship and co-variance between the aerosol index (AI), trace gas concentrations, and meteorological data. The investigation reveals seasonal and regional patterns in the tropospheric columns of trace gases and AI over the Red Sea. The correlation analysis indicates medium-to-low positive correlations (0.2 < r < 0.6) between air pollutants (NO2, SO2, and O3) and meteorological parameters, while negative correlations (−0.3 < r < −0.7) are observed between O3, aerosol index, and wind speed. The results from the HYSPLIT model unveil long-range trajectory patterns. Despite inherent limitations in satellite observations compared to in situ measurements, this study provides an encompassing view of air pollution across the Red Sea, offering valuable insights for future researchers and policymakers.

Modeling the Seasonal Variation of Windborne Transmission of Porcine Reproductive and Respiratory Syndrome Virus between Swine Farms.

Modeling the windborne transmission of aerosolized pathogens is challenging. We adapted an atmospheric dispersion model named the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model to simulate the windborne dispersion of porcine reproductive and respiratory syndrome virus (PRRSv) between swine farms and incorporated the findings into an outbreak investigation. The risk was estimated semi-quantitatively based on the cumulative daily deposition of windborne particles and the distance to the closest emitting farm with an ongoing outbreak. Five years of data (2014:2018) were used to study the seasonal differences of the deposition thresholds of the airborne particles containing PRRSv and to evaluate the model in relation to risk prediction and barn air filtration. When the 14-day cumulative deposition was considered, in winter, above-threshold particle depositions would reach up to 30 km from emitting farms with 84% of them being within 10 km. Long-distance pathogen transmission was highest in winter and fall, lower in spring, and least in summer. The model successfully replicated the observed seasonality of PRRSv, where fall and winter posed a higher risk for outbreaks. Reaching the humidity and temperature thresholds tolerated by the virus in spring and summer reduced the survival and infectivity of aerosols beyond 10-20 km. Within the data limitations of voluntary participation, when wind was assumed to be the sole route of PRRSv transmission, the predictive performance of the model was fair with >0.64 AUC. Barn air filtration was associated with fewer outbreaks, particularly when exposed to high levels of viral particles. This study confirms the usefulness of the HYSPLIT model as a tool when determining seasonal effects and distances and informs the near real-time risk of windborne PRRSv transmission that can be useful in future outbreak investigations and for implementing timely control measures.

Transmission paths and source areas of near-surface ozone pollution in the Yangtze River delta region, China from 2015 to 2021

Near-ground ozone in the Yangtze River Delta (YRD) region has become one of the main air pollutants that threaten the health of residents. However, to date, the transport behavior and source areas of ozone in the YRD region have not been systematically analyzed. In this study, by combining the ozone observational record with a HYSPLIT (hybrid single-particle Lagrangian integrated trajectory) model, we tried to reveal the spatiotemporal regularity of the airflow transport trajectory of ozone. Spatially, high ozone concentrations mainly clustered in industrial cities and resource-based cities. Temporally, the center of the ozone pollution shifted westward of Nanjing from 2015 to 2021. With the passage of time, the influence of meteorological elements on the ozone concentration in the YRD region gradually weakened. Marine atmosphere had the most significant impact on the transmission path of ozone in Shanghai, of which the trajectory frequency in 2021 accounted for 64.21% of the total frequency. The transmission trajectory of ozone in summer was different from that in other seasons, and its transmission trajectory was mainly composed of four medium-distance transmission paths: North China-Bohai Sea, East China Sea-West Pacific Ocean, Philippine Sea, and South China Sea-South China. The contribution source areas mainly shifted to the southeast, and the emission of pollutants from the Shandong Peninsula, the Korean Peninsula-Japan, and the Philippine Sea-Taiwan area increased the impact of ozone pollution in the Shanghai area from 2019 to 2021. This study identified the regional transport path of ozone in the YRD region and provided a scientific reference for the joint prevention and control of ozone pollution in this area.

Trajectory-geospatial approach using HYSPLIT Model in determining air pollution sources at Pasir Gudang industrial areas

Industrial air pollutants emissions can be hazardous to human health and the environment. This study aims to determine the source of air pollution exposure in Malaysia's busiest industrial area, Pasir Gudang by using the trajectory-geospatial approach. The Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model was used to determine the pathway of air backwards-trajectory. While the geospatial analysis for air pollution sources identification in Pasir Gudang was conducted using Geographic Information System (GIS). Three days of air mass backwards-trajectories were successfully obtained, where the dominant air mass pathways direction came from West Sumatra, Indonesia, influenced by the Southwest monsoon wind. The air mass backwards-trajectories also show there are influenced by nearby factories' emissions. From the geospatial buffer analysis, about 17 to 60 factories were identified to be possible sources of air pollution exposure since the location of factories are within a 1 km buffer zone of six affected schools in Pasir Gudang. The meteorological factors that influence the flow of high emissions of air masses pollutant from nearby factories have worsened the exposure level of air pollution until impacted the health of school’s students. From the findings, a standard of procedure (SOP) for air pollution source identification using a trajectory-geospatial approach has been developed as a guideline for all the stakeholders involved and essential in understanding better strategies in monitoring and mitigating industrial air pollution, particularly in Pasir Gudang as the buffer zones required by the authorities are not actively functioning to mitigate the air pollution exposures. Keywords: Air pollution, buffer zones, HYSPLIT, industrial area, Pasir Gudang, trajectory-geospatial approach

Sentinel-2 satellite and HYSPLIT model suggest that local cereal harvesting substantially contribute to peak Alternaria spore concentrations

Alternaria is a human/animal allergen and plant/animal pathogen. Cereal harvesting emits a large amount of Alternaria spores into the atmosphere. However, estimating the peak spore periods and source areas from large areas is often a challenge because of insufficient observation stations. The purpose of this study was to examine, using remote sensing and an atmospheric transport and dispersion model, the contribution of cereal harvesting to peak Alternaria spore concentrations. Daily Alternaria spores were collected using Hirst-type traps in 12 sites in Europe for the period 2016-2018. Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) back-trajectory and dispersion model was integrated with Sentinel-2 satellite imagery, Corine Land Cover 2018 (CLC2018) and Eurostat cereal data 2016 to map the Alternaria spore peaks and source areas in the 12 sites. Ground truth harvest data, collected at Worcester, UK, in 2018, and meteorological data were used to determine any effect of cereal harvesting and weather on peak spore concentrations. The results showed that the Sentinel-2 satellite detected agricultural areas that underwent intensive harvesting and this coincided with a rapid increase of Alternaria spore concentrations. Furthermore, local agricultural areas cultivated with cereals were the main sources of the peak Alternaria spore concentrations in all the study sites. Remote agricultural and non-agricultural sources, to a lesser extent, contributed to the peak spore concentrations at some sites, e.g. Borstel, Leicester and Worcester. Temperature during the harvesting periods (July and August) was found to significantly contribute to the peak spore concentrations. Overall, the study showed that it is possible to use Sentinel-2 satellite data alongside atmospheric transport and dispersion models to estimate periods of peak Alternaria spore concentrations and sources at a continental scale. This approach can be replicated for other bioaerosols that affect human health, agriculture and forestry.

Aerosol Distributions and Sahara Dust Transport in Southern Morocco, from Ground-Based and Satellite Observations

The present study investigates aerosols distributions and a strong Sahara dust-storm event that occurred by early August 2018, in the South of Morocco. We used columnar aerosol optical depth (AOD), Angstrom Exponent (AE) and volume size distributions (VSD) as derived from ground-based observations by 2 AERONET (AErosol RObotic NETwork) sun-photometers at Saada (31.63°N, 8.16°W) and Ouarzazate (30.93°N, 6.91°W) sites, over the periods 2004–2019 and 2012–2015, respectively. The monthly seasonal distributions of AOD, AE, and VSD showed a seasonal trend dominated by the annual cycle, with a maximum aerosol load during summer (July–August) and a minimum in winter (December–January), characterized by a coarse mode near the radius of 2.59 μm and a fine mode at the radius of 0.16 μm, respectively. Indeed, this study showed that aerosol populations in southern Morocco are dominated by Saharan desert dust, especially during the summer season. The latter can sometimes be subject of dust-storm events. The case study presented in this paper reports on one of these events, which happened in early August 2018. The HYSPLIT (HYbrid Single Particle Lagrangian Integrated Trajectory) model was used to simulate air-mass back-trajectories during the event. In agreement with ground-based (AERONET sun-photometers) and satellite (CALIOP, MODIS and AIRS) observations, HYSPLIT back-trajectories showed that the dust air-mass at the 4-km layer, the average height of the dust plume, has crossed southern Morocco over the Saada site, with a westward direction towards the Atlantic Ocean, before it changed northward up to the Portuguese coasts.

Assessment of aerosol burden over Ghana

Although air pollution in Ghana is ranked number one in environmental health threats to public health and sixth to cause of deaths, routine monitoring is rare. This paper presents fourteen years (2005-2018) assessment of aerosol optical depth (AOD) at 3 km resolution from MODIS Aqua and Terra satellites to ascertain the Spatio-temporal and seasonal distribution of aerosols over Ghana and its major cities. The MODIS AOD at 3 km were validated against ground-based Aerosol Robotic Network (AERONET) AODs to ascertain the suitability of the MODIS 3 km data for air quality application in the region. The contribution of distant aerosols to city aerosol loadings was also assessed with Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) backscatter model. A moderate-high aerosol burden (AODs ∼ 0.50) was observed over Ghana with a significant contribution from the pre-monsoon season. City centres of Takoradi and Kumasi showed higher aerosol loads (AODs ∼ 0.80) than Accra and Tamale. The HYSPLIT model showed that distant or transported aerosol sources to the city centres were of both marine and land generated origins. Linear regression analysis between MODIS AOD and AERONET AOD showed a reasonably good correlation of ∼ 0.60 for Aqua and Terra. From the validation analysis, both Aqua and Terra satellites can be used for air quality monitoring over Ghana; however, more ground research must be conducted to ascertain better aerosol model assumptions for the region.

Variation and dispersal of PM10 and PM2.5 during COVID-19 lockdown over Kolkata metropolitan city, India investigated through HYSPLIT model

The higher concentration of PM10 and PM2.5 in the lower atmosphere is severely harmful for human health and it also makes visibility diminution along with weather and climate modifications. The main objective is to find out the spatiotemporal variation and dispersal of PM10 and PM2.5 along with COVID-19 infection in the dusty city Kolkata. The consecutive two years PM10 and PM2.5 data of different stations have been obtained from State Pollution Control Board, Govt. of West Bengal. Forward trajectory analysis has been done through HYSPLIT (Hybrid Single Particle Lagrangian Integrated Trajectory) model to find the path and direction of air particles. The result showed that the various meteorological or environmental factors (such as temperature, relative humidity, wind, wind speed, pressure and gusty wind) and geographical location regulate the spatiotemporal variation of PM10 and PM2.5. These factors like high temperature with relative humidity and strong wind influence to disperse the particulate matters from north to south direction from city to outside during summer in Kolkata metropolitan city. During summer (both pre and lockdown years), the height of particles is extended up to 1000 m owing to active atmospheric ventilation whereas in winter it is confined within 100 m. The HYSPLIT model clearly specified that the particles dispersed from south, south-west to north and north east direction due to strong wind. The constant magnification of PM10 and PM2.5 in the lower atmosphere leads to greater frequency of COVID-19 infections and deaths. In Kolkata, the one of the crucial reasons of high infection and deaths (COVID-19) is co-morbidity of people.

Spatio-temporal changes of AOD in Xinjiang of China from 2000 to 2019: Which factor is more influential, natural factor or human factor?

Aerosol optical depth (AOD), which represents the optical attenuation, poses a major threat to the production activity, air quality, human health and regional sustainable development of arid and semi-arid areas. To some degree, AOD shows areal air pollution level and possesses obvious spatio-temporal characteristics. However, long-time sequences and detailed AOD information can not be provided due to currently limited monitoring technology. In this paper, a daily AOD product, MODIS-based Multi-angle Implementation of Atmospheric Correction (MAIAC), is deployed to analyze the spatio-temporal characteristics in Xinjiang Uygur Autonomous Region from 2000 to 2019. In addition, the importance of influencing factors for AOD is calculated through Random Forest (RF) Model and the propagation trajectories of pollutants are simulated through Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) Model. Spatio distribution of AOD presents a tendency that AOD value in northern Xinjiang is low while the value in southern Xinjiang is high. Regions with high AOD values are mainly concentrated in Tarim Basin. AOD in southern Xinjiang is the highest, followed by that in eastern Xinjiang and AOD value in northern Xinjiang is the lowest. Seasonal variation of AOD is significant: Spring (0.309) > summer (0.200) > autumn (0.161) > winter (0.158). Average AOD value in Xinjiang is 0.196. AOD appears wavy from 2000 to 2014 with its low inflection point (0.157) appearing in 2005, and then increases, reaching its peak in 2014 (0.223). The obvious downward tendency after 2014 shows that the use of coal to natural gas (NG) conversion project improves the conditions of local environment. According to RF Model, NG contributes most to AOD. HYSPLIT Model reveals that aerosol in southern Xinjiang is related to the short-distant carriage of dust aerosol from the Taklimakan Desert. Aerosol there can affect Inner Mongolia through long-distant transport. Blocked by the Tianshan Mountains, fine dust particles can not cross the Tianshan Mountains to become a factor contributing to AOD in northern Xinjiang.

Comparative Analysis of Three Methods for HYSPLIT Atmospheric Trajectories Clustering

Using the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model to obtain backward trajectories and then conduct clustering analysis is a common method to analyze potential sources and transmission paths of atmospheric particulate pollutants. Taking Qingdao (N36 E120) as an example, the global data assimilation system (GDAS 1°) of days from 2015 to 2018 provided by National Centers for Environmental Prediction (NCEP) is used to process the backward 72 h trajectory data of 3 arrival heights (10 m, 100 m, 500 m) through the HYSPLIT model with a data interval of 6 h (UTC 0:00, 6:00, 12:00, and 18:00 per day). Three common clustering methods of trajectory data, i.e., K-means, Hierarchical clustering (Hier), and Self-organizing maps (SOM), are used to conduct clustering analysis of trajectory data, and the results are compared with those of the HYSPLIT model released by National Oceanic and Atmospheric Administration (NOAA). Principal Component Analysis (PCA) is used to analyze the original trajectory data. The internal evaluation indexes of Davies–Bouldin Index (DBI), Silhouette Coefficient (SC), Calinski Harabasz Index (CH), and I index are used to quantitatively evaluate the three clustering algorithms. The results show that there is little information in the height data, and thus only two-dimensional plane data are used for clustering. From the results of clustering indexes, the clustering results of SOM and K-means are better than the Hier and HYSPLIT model. In addition, it is found that DBI and I index can help to select the number of clusters, of which DBI is preferred for cluster analysis.

Distribution Trends of Cadmium and Lead in Timberline Coniferous Forests in the Eastern Tibetan Plateau

The concentrations of Pb and Cd in the needles and twigs of fir and spruce collected from 26 sites in the Eastern Tibetan Plateau were measured and analyzed in this study. The mean concentrations of Cd and Pb were 0.034 and 1.291 mg/kg, respectively, in the needles and 0.101 and 2.511 mg/kg, respectively, in the twigs. These concentrations increased significantly with needle and twig age and peaked at 5 years. The twigs were significantly enriched in Pb and Cd compared with the needles. The spatial distributions of Pb and Cd were determined using the inverse-distance-weighted spatial interpolation method on the basis of the mean concentration of the elements in the needles and twigs from each site. The highest concentrations of Pb and Cd in twigs and needles were found in Yunnan Province and Gongga Mountain. They showed a tendency to decline from Yunnan Province to the northern direction, as well as from Gongga Mountain to the western area. Principal component analysis showed that Pb and Cd originated from the anthropogenic activities in this area. The mining activities and climatic factors may be the main sources of Pb and Cd in this area. Combining the HYSPLIT (The Hybrid Single-Particle Lagrangian Integrated Trajectory) model and PCA, the results implied that exterior Pb and Cd sources from Southeast Asia and the eastern developed cities in China can infiltrate the ecosystem through long-range transportation and accumulate in timberline forests, with atmospheric deposition in the Eastern Tibetan Plateau. This plateau suffers from severe Pb pollution but slight Cd contamination.

Fluxes of Atmospheric Greenhouse‐Gases in Maryland (FLAGG‐MD): Emissions of Carbon Dioxide in the Baltimore, MD‐Washington, D.C. Area

To study emissions of CO2 in the Baltimore, MD-Washington, D.C. (Balt-Wash) area, an aircraft campaign was conducted in February 2015, as part of the FLAGG-MD (Fluxes of Atmospheric Greenhouse-Gases in Maryland) project. During the campaign, elevated mole fractions of CO2 were observed downwind of the urban center and local power plants. Upwind flight data and HYSPLIT (Hybrid Single Particle Lagrangian Integrated Trajectory) model analyses help account for the impact of emissions outside the Balt-Wash area. The accuracy, precision, and sensitivity of CO2 emissions estimates based on the mass balance approach were assessed for both power plants and cities. Our estimates of CO2 emissions from two local power plants agree well with their CEMS (Continuous Emissions Monitoring Systems) records. For the 16 power plant plumes captured by the aircraft, the mean percentage difference of CO2 emissions was -0.3 %. For the Balt-Wash area as a whole, the 1σ CO2 emission rate uncertainty for any individual aircraft-based mass balance approach experiment was ±38 %. Treating the mass balance experiments, which were repeated seven times within nine days, as individual quantifications of the Balt-Wash CO2 emissions, the estimation uncertainty was ±16 % (standard error of the mean at 95% CL). Our aircraft-based estimate was compared to various bottom-up fossil fuel CO2 (FFCO2) emission inventories. Based on the FLAGG-MD aircraft observations, we estimate 1.9±0.3 MtC of FFCO2 from the Balt-Wash area during the month of February 2015. The mean estimate of FFCO2 from the four bottom-up models was 2.2±0.3 MtC.

High post-season Alnus pollen loads successfully identified as long-range transport of an alpine species

Abstract Alnus pollen is one of the Northern Hemisphere's major aeroallergens. In Central Europe, the genus is represented by three species (Alnus glutinosa, Alnus incana, and Alnus viridis). The most common one, A. glutinosa (L.) Gaertn., is widespread in lowland riparian forests, swamps, and forest edges. However, to date is still unknown if all of them - in terms of pollen exposure - are clinically relevant for sensitized individuals. To investigate the associated pollen exposure, particularly also because of long-range transport of airborne pollen, we used backward air mass trajectories and tested this method for the year 2015, based on daily Alnus pollen concentrations at 26 sites in Bavaria, Germany. A. glutinosa's main pollen season extends from February to March, but a six-day, post-season episode was additionally identified in June. For this episode and all sites, 72-h backward trajectories were calculated at 3-h intervals using high spatial and temporal resolution ERA5 reanalysis data and the HYSPLIT (hybrid single-particle Lagrangian integrated trajectory) model. This backward trajectory method identified air masses from the alpine region in Switzerland and Austria, where relevant areas of A. viridis (Chaix) DC as potential pollen sources exist. These may explain the post-season episode in June, as additionally confirmed by its unique spatial distribution, by a considerably later flowering period, and by repeated long-range transport events as observed in a 23-year pollen time series.

Retrieval of Fine-Resolution Aerosol Optical Depth (AOD) in Semiarid Urban Areas Using Landsat Data: A Case Study in Urumqi, NW China

The aerosol optical depth (AOD) represents the light attenuation by aerosols and is an important threat to urban air quality, production activities, human health, and sustainable urban development in arid and semiarid regions. To some extent, the AOD reflects the extent of regional air pollution and is often characterized by significant spatiotemporal dynamics. However, detailed local AOD information is ambiguous at best due to limited monitoring techniques. Currently, the availability of abundant satellite data and constantly updated AOD extraction algorithms offer unprecedented perspectives for high-resolution AOD extraction and long-time series analysis. This study, based on the long-term sequence MOD09A1 data from 2010 to 2018 and lookup table generation, uses the improved deep blue algorithm (DB) to conduct fine-resolution (500 m) AOD (at 550 nm wavelength) remote sensing (RS) estimation on Landsat TM/OLI data from the Urumqi region, analyzes the spatiotemporal AOD variation characteristics in Urumqi and combines gray relational analysis (GRA) and the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model to analyze AOD influence factors and simulate pollutant propagation trajectories in representative periods. The results demonstrate that the improved DB algorithm has a high inversion accuracy for continuous AOD inversion at a high spatial resolution in urban areas. The spatial AOD distribution in Urumqi declines from urban to suburban areas, and higher AODs are concentrated in cities and along roads. Among these areas, Xinshi District has the highest AOD, and Urumqi County has the lowest AOD. The seasonal AOD variation characteristics are distinct, and the AOD order is spring (0.411) > summer (0.285) > autumn (0.203), with the largest variation in spring. The average AOD in Urumqi is 0.187, and the interannual variation generally shows an upward trend. However, from 2010 to 2018, AOD first declined gradually and then declined significantly. Thereafter, AOD reached its lowest value in 2015 (0.076), followed by a significant AOD increase, reaching a peak in 2016 (0.354). This shows that coal to natural gas (NG) project implementation in Urumqi promoted the improvement of Urumqi’s atmospheric environment. According to GRA, the temperature has the largest impact on the AOD in Urumqi (0.699). Combined with the HYSPLIT model, it was found that the aerosols observed over Urumqi were associated with long-range transport from Central Asia, and these aerosols can affect the entire northern part of China through long-distance transport.

The radiological assessment, hazard evaluation, and spatial distribution for a hypothetical nuclear power plant accident at Baiji potential site

BackgroundThe safety assessment in site selection for a new nuclear power plant is an essential issue for human health. It could be improved by predicting the consequences for a hypothetical accident. This paper is contextual with the nuclear safety regarding the risk upon human health from the hazard constituted by the emission of radioactive material due to a hypothetical nuclear power plant accident. HYSPLIT model used and configured based on terrestrial and meteorological conditions for this purpose.ResultsIt presents an analysis of the time-series and spatial distribution for dispersed radioactive contaminants from a hypothetical accident at Baiji potential site. This is based on the geological and meteorological specifications of the potential site. Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model configured to simulate the atmospheric dispersion of fission emissions, then assesses the public health consequences of a hypothetical nuclear accident. Results indicate that the total individual dose intake by the population living around the potential site from the hypothetical accident exceeded 1 Sv, greater than the allowed dose limits by International Commission on Radiological Protection (ICRP). The probability of cancer incidence at regions on directions of southeast to northeast along 30 km from the potential site was high (0.0378 to 0.00131) risk/person. However, the areas that laid on the west and south-west of the site recorded higher levels of influence compared to regions on other directions. Also, the reduction of exposure dose with the distance from the site presented. The north-direction regions from the Baiji site recorded a rapid reduction of exposure dose to become zero at 40 km distance.ConclusionsFinally, to minimize the radiological impacts on population, emergency procedures are required at the regions that laid on the west and south-west of the site. These countermeasure remedy actions should include evacuation, sheltering, ban the sale of local agriculture productions, and long-range resettlement of the population. Since the plume of radioactive contaminants did not arrive at the regions on east and northeast, 40 km away from Baiji site, these areas could be categorized as a support zone.

Assessment of Urban CO2 Measurement and Source Attribution in Munich Based on TDLAS-WMS and Trajectory Analysis

Anthropogenic carbon dioxide (CO2) emissions mainly come from cities and their surrounding areas. Thus, continuous measuring of CO2 in urban areas is of great significance to studying human CO2 emissions. We developed a compact, precise, and self-calibrated in-situ CO2/H2O sensor based on TDLAS (tunable diode laser absorption spectroscopy), WMS (wavelength modulation spectroscopy), and VCSEL (vertical-cavity surface-emitting laser). Multi-harmonic detection is utilized to improve the precision of both measurements to 0.02 ppm for CO2 and 1.0 ppm for H2O. Using the developed sensor, we measured CO2 concentrations continuously in the city center of Munich, Germany, from February 2018 to January 2019. Urban CO2 concentrations are strongly affected by several factors, including vegetation photosynthesis and respiration (VPR), planetary boundary layer (PBL) height, and anthropogenic activities. In order to further understand the anthropogenic contribution in terms of CO2 sources, the HySPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) model was applied to calculate six-hour backward trajectories. We analyzed the winter CO2 with the trajectory clustering, PSCF (potential source contribution function), and CWT (concentration weighted trajectory) methods, and found that local emissions have a great impact on urban CO2 concentration, with main emission sources in the north and southeast directions of the measurement site. In situations with an uneven trajectory distribution, PSCF proves somewhat superior in predicting the potential emission sources compared to CWT.

Analysis of a Severe PM2.5 Episode in the Seoul Metropolitan Area in South Korea from 27 February to 7 March 2019: Focused on Estimation of Domestic and Foreign Contribution

In this study, domestic and foreign contributions to a severe PM2.5 episode in South Korea, in which “emergency reduction measures against particulate matter” were issued, were analyzed. During the period between 27 February and 7 March in 2019 when high PM2.5 concentrations occurred, the PM2.5 concentration in the Seoul metropolitan area (SMA) in South Korea was approximately 87.3 μg/m3 on average, and a severe PM2.5 concentration level of approximately 113.4 μg/m3 was observed between 3 March and 5 March. The results of the analysis conducted using the HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) model and meteorological observation data showed that northwesterly wind or westerly winds were formed during the P1 and P3 periods when the PM2.5 concentration markedly increased. When the PM2.5 concentrations in East Asia were simulated using the Community Multiscale Air Quality (CMAQ), it was found that the high PM2.5 concentrations that occurred in the SMA of South Korea were mostly affected by PM2.5 transported over long distances and following atmospheric stagnation. When the domestic and foreign contributions were evaluated using the brute-force method (BFM), the foreign and domestic contribution concentrations were found to be 62.8 and 16.8 μg/m3, respectively, during the target period of this study. It was also found that the foreign contribution was 78.8%, while the domestic contribution was 21.2%.