Vertical distribution of aerosols and association with atmospheric boundary layer structures during regional aerosol transport over central China.

Atmospheric boundary layer (ABL) structure was a crucial factor in altering the vertical aerosol distribution and modulating the impact of regional aerosol transport on the atmospheric environment in the receptor region. The long-term characteristics of ABL structures for different vertical aerosol distributions and the distinct influencing mechanisms between daytime and nighttime aerosol transport interacting with the diurnal ABL transition have rarely been studied in the receptor regions. Based on 9-year (2013-2021) satellite-retrieved profiles of aerosol extinction coefficients and meteorological sounding data, we targeted Wuhan, an urban city with noteworthy transport contribution in central China, to reveal the general wintertime transport height of ∼500 m and the corresponding unstable ABL structure during regional transport. By comparing typical daytime and nighttime aerosol transport with high-resolution Lidar observations, the aerosol transport near the ABL top coupled with intense mechanical mixing provided sufficient meteorological conditions for heavy aerosol pollution formation in the receptor regions, which was more favorable during nighttime transport followed by the adequate ABL development after sunrise. These findings enhance our comprehension of the ABL impact on air pollution in the receptor regions, which have implications for the precise prevention and control of the regional atmospheric environment.

Precursor turbulent inflow dataset for large eddy simulation of a semi-idealized European generic city.

This data article provides high-quality turbulent inflow boundary data with a high spatial and temporal resolution of a very rough atmospheric boundary layer (ABL) wind tunnel, which can be applied as the large eddy simulation (LES) inflow condition on the Michelstadt test cases. A high-quality LES of the WOTAN wind tunnel of the Environmental Wind Tunnel Laboratory (EWTL) was conducted using OpenFOAM software, and data is stored at a plane at 1000Hz frequency at the end of the roughness elements. This data serves as the turbulent inflow boundary condition, offering computational fluid dynamics (CFD) researchers a cost-effective means to simulate the benchmark Michelstadt test cases for LES validation. This data will be utilized to perform high-quality LES, which are pivotal in bridging the research gap in understanding the intricate nature of wind dynamics in a realistic urban environment.

Mesoscale structure of the atmospheric boundary layer across a natural roughness transition.

The structure and intensity of turbulence in the atmospheric boundary layer (ABL) drive fluxes of sediment, contaminants, heat, moisture, and CO[Formula: see text] at the Earth's surface. Where ABL flows encounter changes in roughness-such as cities, wind farms, forest canopies, and landforms-a new mesoscopic flow scale is introduced: the internal boundary layer (IBL), which represents a near-bed region of transient flow adjustment that develops over kilometers. Measurement of this new mesoscopic scale lies outside present observational capabilities of ABL flows, and simplified models fail to capture the sensitive dependence of turbulence on roughness geometry. Here, we use large-eddy simulations, run over high-resolution topographic data and validated against field observations, to examine the structure of the ABL across a natural roughness transition: the emergent sand dunes at White Sands National Park. We observe that development of the IBL is triggered by the abrupt transition from smooth playa surface to dunes; however, continuous changes in the size and spacing of dunes over several kilometers influence the downwind patterns of boundary stress and near-bed turbulence. Coherent flow structures grow and merge over the entire [Formula: see text]10 km distance of the dune field and modulate the influence of large-scale atmospheric turbulence on the bed. Simulated boundary stresses in the developing IBL counter existing expectations and explain the observed downwind decrease in dune migration, demonstrating a mesoscale coupling between flow and form that governs landscape dynamics. More broadly, our findings demonstrate the importance of resolving both turbulence and realistic roughness for understanding fluid-boundary interactions in environmental flows.

Inverse effects of aerosol radiative forcing on heavy PM2.5 pollution of local accumulation and regional transport over Central China.

Regional transport of air pollutants is a crucial factor influencing atmospheric environment, and aerosol radiative forcing (ARF) feedback to atmospheric boundary layer (ABL) structure and ambient air pollution is yet to be comprehensively understood over the receptor region of regional transport. By simulating meteorology and air pollutants during a heavy PM2.5 pollution event with WRF-Chem model, we quantitatively investigated the ARF and ABL interaction for PM2.5 pollution over the Twain-Hu Basin (THB), a key receptor region of regional transport over central China. Driven by northerly winds, PM2.5 was transported from upstream north China to downstream THB accompanied by high PM2.5 levels in the free troposphere. The ARF exacerbated local PM2.5 accumulation by up to 20 µg m-3 and inhibited the impact of regional transport on PM2.5 levels in the ABL with reducing near-surface PM2.5 concentrations of 5 µg m-3 over the THB. The ARF-intensified air temperature inversion at the top of ABL was unfavorable for the transported air pollutants crossing the ABL top to the near-surface layer, thus weakening the impact of regional PM2.5 transport on air quality in the receptor region. Meanwhile, the ARF of transported PM2.5 induced updrafts in the free troposphere, promoting vertical mixing of air pollutants with positive feedback on increasing secondary PM2.5 concentrations in the free troposphere. The ARF induced more and less secondary PM2.5 formations respectively in the free troposphere and the near-surface layer during the regional transport period of air pollution. These results enhance our comprehension of aerosol-meteorology feedback in regional changes of atmospheric environment with inverse effects of ARF on PM2.5 pollution of local accumulation and regional transport.

Contradictory response of ozone and particulate matter concentrations to boundary layer meteorology.

At the present stage, collaborative control of particulate matter and ozone pollution has become a modern challenge. The atmospheric boundary layer height (ABLH) is an important meteorological parameter for the sources and sinks of air pollutants. It is generally recognized that the reduction of boundary layer is conducive to the accumulation of pollutants. However, in recent years, some studies have shown that the relationship between ABLH and ozone is not negatively correlated. Here, we analyzed the spatial distribution characteristics of PM2.5 and ozone exceedance in China from 2015 to 2022. The relationships between particulate pollution and ozone pollution and boundary layer meteorology were discussed. The key to coordinated control is to control the PM2.5 concentration in the winter and ozone in summer. Moreover, the two have different responses to meteorological factors, especially to the ABLH. Low temperature and low ABLH are conducive to the deterioration of particulate pollution, but high temperature and high ABLH are conducive to the occurrence and development of ozone pollution. The response of ozone to ABLH is contrary to previous studies in Europe and the United States. Moreover, an abnormal positive correlation was observed for PM2.5 and ABLH in Southwest China, which was mainly due to the impact of biomass combustion in Southeast Asia.

Properties of the mixing layer height retrieved from ceilometer measurements in Slovakia and its relationship to the air pollutant concentrations.

Mixing layer height (MLH) is an important meteorological parameter for air quality since it significantly affects ground-level pollution in the atmosphere. This study examined the properties of the MLH on diurnal and seasonal timescales over a 3-year period (2020-2022) using high temporal resolution measurements from eight Vaisala CL31 ceilometers situated around Slovakia. Hourly averaged MLH data was retrieved from the BL-View software using merged method. The highest daily maxima for the MLH occurred mostly in summer and spring, while the lowest values occurred predominantly during winter and autumn. The average MLH daily maximum in summer was 2229 m, and just 859 m in winter. During summer, the spatial distribution of the MLH daily maxima was more uniform compared to winter, when the air masses within the individual valleys did not mix well. Correlations between ground-level pollutant concentrations and hourly mean/daily mean MLH were analyzed. The highest correlation, R≈0.6, was found for O3. For PM10, PM2.5, and NOx, the anticorrelations with MLH were found with maximum in winter (R ≈ - 0.3 for hourly data and R ≈ - 0.5 for daily mean data) but no relation in summer. Lastly, the ceilometer MLH was compared to the radiosonde retrieved MLH for various cloud covers. Our analysis is based on an extensive set of empirical data, which can improve the accuracy and effectiveness of meteorological and atmospheric chemistry models. The findings can support air pollution forecasting and warning systems, providing valuable insights for policymakers and researchers.

Vertical distribution and transport of microplastics in the urban atmosphere: New insights from field observations.

The distribution and transport of atmospheric microplastics (AMPs) have raised concerns regarding their potential effects on the environment and human health. Although previous studies have reported the presence of AMPs at ground level, there is a lack of comprehensive understanding of their vertical distribution in urban environments. To gain insight into the vertical profile of AMPs, field observations were conducted at four different heights (ground level, 118 m, 168 m and 488 m) of the Canton Tower in Guangzhou, China. Results showed that the profiles of AMPs and other air pollutants had similar layer distribution patterns, although their concentrations differed. The majority of AMPs were composed of polyethylene terephthalate and rayon fibers ranging from 30 to 50 µm. As a result of atmospheric thermodynamics, AMPs generated at ground level were only partially transported upward, leading to a decrease in their abundance with increasing altitude. The study found that the stable atmospheric stability and lower wind speed between 118 m and 168 m resulted in the formation of a fine layer where AMPs tended to accumulate instead of being transported upward. This study for the first time delineated the vertical profile of AMPs within the atmospheric boundary layer, providing valuable data for understanding the environmental fate of AMPs.

Characteristics of elevated aerosol layer over the Indian east coast, Kattankulathur (12.82oN, 80.04°E): A northeast monsoon region.

The elevated aerosol layer (EAL) plays a vital role in weather and climate by modifying the Earth's radiation budget. In the present study, the EAL occurrence and its characteristics in the pre-monsoon season using micropulse lidar (MPL) observations during 2016-2018 and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) during 2007-2018 over Kattankulathur is being reported. We have collected 147 days (101 cases) of MPL (CALIPSO) observations during clear sky conditions in the pre-monsoon 2016-2018 (2007-2018), out of which EAL is observed for 56 days (61 cases). The EAL width is generally found to be ~2.0 km and occurs between ~1.0 km and 5.0 km. Three different types of EALs are categorized based on their altitudinal occurrence using the zero-crossing method. The EALs with their base at ~1.0-1.5 km, ~1.5-2.0 km, and ~ 2.0-3.0 km are taken as types I, II, and III, which occur for 9, 20, and 27 days, respectively. The EAL significantly modifies the total columnar aerosol optical depth (AOD). It is found that AOD, in total, within ABL and EAL, are ~0.72 (0.61), 0.28 (0.25), and 0.45 (0.36) using MPL (CALIPSO), respectively. The aerosols within ABL contribute ~38 % (41 %) while EAL ~ 62 % (59 %) to the total AOD obtained using MPL (CALIPSO). We observed that the ABL and EAL are characterized by different aerosol subtypes, such as dust marine (31 %) and smoke (~ 27 %) aerosols. Other aerosol subtypes, such as dust and polluted dust, commonly occur within the ABL (54 %) and EAL (52 %).

A Novel Near-Surface Wave-Coherent Instantaneous Profiling System for Atmospheric Measurements.

Large knowledge gaps concerning the effect of ocean surface waves on near-surface vertical distributions of temperature and humidity exist due to practical limitations and sensor fidelity challenges of direct measurements. Measurements of temperature and humidity are classically made using rocket- or radiosondes and fixed weather stations and can utilize a tethered profiling system. However, these measurement systems have limitations when obtaining wave-coherent measurements near the sea surface. Consequently, boundary layer similarity models are commonly employed to fill in near-surface measurement gaps despite the documented shortcomings of the models in this region. Thus, this manuscript presents a near-surface wave-coherent measurement platform that measures high-temporal-resolution vertical distributions of temperature and humidity down to ~0.3 m above the instantaneous sea surface. The design of the platform is described along with preliminary observations obtained during a pilot experiment. Ocean surface-wave phase-resolved vertical profiles are also demonstrated from the observations.

Atmospheric Boundary Layer Wind Profile Estimation Using Neural Networks, Mesoscale Models, and LiDAR Measurements.

This paper introduces a novel methodology that estimates the wind profile within the ABL by using a neural network along with predictions from a mesoscale model in conjunction with a single near-surface measurement. A major advantage of this solution compared to other solutions available in the literature is that it requires only near-surface measurements for prediction once the neural network has been trained. An additional advantage is the fact that it can be potentially used to explore the time evolution of the wind profile. Data collected by a LiDAR sensor located at the University of León (Spain) is used in the present research. The information obtained from the wind profile is valuable for multiple applications, such as preliminary calculations of the wind asset or CFD modeling.

Evolution law of atmospheric boundary layer in Gurbantünggüt Desert based on reanalysis dataset and in situ observation data.

As a special geographical unit on the earth, deserts have certain differences in planetary boundary layer (PBL) characteristics from other surface types. In order to find out the long-term evolution law of the Gurbantünggüt Desert, on the basis of evaluating the availability of reanalysis data, using the most effective reanalysis data and situ measured data in this area, the evolution law of the atmospheric boundary layer in the desert area was studied. The results show that among the ERA5, MERRA2, JRA-55 and NCEP-FNL reanalysis data, the ERA5 data has the smallest error with the measured data in the comparison of ground elements or high-altitude meteorology parameters, and can be used for the long-term evolution of the atmospheric boundary layer in desert areas. Based on the ERA5 dataset, the annual planetary boundary layer height (PBLH) of the desert fluctuated between 1979 and 1985, but showed a downward trend overall. From 1986 to 2019, the PBLH generally shows an upward trend, and by 2020, the PBLH decreases again. The PBLH in the summer of the desert was contrary to the inter-annual change trend of the PBLH throughout the year. The spatial distribution shows that the PBLH has the characteristics of north-south anisotropy. The characteristics of the ABL in the Gurbantünggüt Desert in different thermal states in summer vary greatly. Based on the sounding observational data, the average PBLH of the stable boundary layer in the Gurbantünggüt Desert in summer is 496 m, the average PBLH of the convective boundary layer is 1693 m, and the average PBLH of the neutral boundary layer is 1208 m. The ABL in desert areas from 02:00 to 08:00 and 23:00 is dominated by stable boundary layers, of which the proportion of stable boundary layers at 05:00 is as high as 67%. During the day, the boundary layer from 14:00 to 17:00 is mainly the convective boundary layer, accounting for more than 50%, and the boundary layer at 20:00 is mainly a neutral boundary layer, accounting for 55%.

Atmospheric Boundary Layer Over Ahmedabad, Western Indian Region: Impact of COVID-19 Nationwide Lockdown.

The government of India imposed a nationwide lockdown to tackle the outbreak of COVID-19 in 2020. This period witnessed record low anthropogenic activity, which had severe socio-economic impacts but also had orthogonal effects on the ambient air quality of the atmosphere. This study focuses on the variations in the atmospheric boundary layer (ABL) over a western Indian urban region in the light of COVID-19. Continuous backscatter recorded by a ceilometer, stationed at Ahmedabad, was used in this study to monitor the ABL during the national lockdown (NLD) in 2020 and state restrictions in 2021, and compared with the control year of 2019. In parallel, improvement in air quality during the NLD was observed by the SAFAR air quality station at Ahmedabad, with decreased particulate matter concentrations. The ground-based observations were substantiated by the ERA5 reanalysis dataset. A decline in the ABL height was recorded during the NLD, which showed improvement in 2021 but which was shy of the ABL in 2019. This was correlated with rain events during the observational period, recorded by an automatic weather station.

High black carbon episodes over a polluted metropolis near the land-sea boundary and their impact on associated atmospheric dynamics.

The present investigation outlines the crucial factors that influence the black carbon (BC) concentrations over a polluted metropolis, Kolkata (22.57° N, 88.37° E), India. Located in the eastern part of the Indo Gangetic Plain (IGP) outflow region and close to the land-ocean boundary, Kolkata is subject to contrasting seasonal maritime airflow from the Bay of Bengal and continental air mass from the IGP and Tibetan plateau region, which modulates the local concentration of BC. The origin of aerosol transport and associated atmospheric dynamics with high and low BC activities over Kolkata are examined during 2012-2015 using data from multi-technique sources which include measurements of ground-based instruments of aethalometer and multi-frequency microwave radiometer, reanalysis data from ERA-5 and MEERA-2, and model outputs from HYPSLIT back trajectory model simulations. The study highlights the control of IGP wind inflow on the occurrence of anomalous enhancements in BC concentration during weekends and holidays when local emissions are low. High BC events are associated with enhanced atmospheric heating below the boundary layer (2000 m) and significant negative surface radiative forcing. The response of the boundary layer to high and low BC episodes, shown in the diurnal variation in comparison with the seasonal mean, is investigated. Dominant suppression of morning and night-time boundary layer height is observed on high BC days. During the daytime in pre-monsoon, post-monsoon, and winter seasons, boundary layer height peaks are found to be strongly controlled by high BC episode occurrences as obtained from the hourly data of ERA-5.

Insights into multidimensional transport flux from vertical observation and numerical simulation in two cities in North China.

This study represents the first quantitative evaluation of pollution transport budget within the boundary layer of typical cities in the Beijing-Tianjin-Hebei (BTH) region from the perspective of horizontal and vertical exchanges and further discusses the impact of the atmospheric boundary layer (ABL)-free troposphere (FT) exchange on concentration of fine particulate matter (PM2.5) within the ABL during heavy pollution. From the perspective of the transport flux balance relationship, differences in pollution transport characteristics between the two cities is mainly reflected in the ABL-FT exchange effect. The FT mainly flowed into the ABL in BJ, while in SJZ, the outflow from the ABL to the FT was more intense. Combined with an analysis of vertical wind profile distribution, BJ was found to be more susceptible to the influence of northwest cold high prevailing in winter, while sinking of strong cold air allowed the FT flowing into the ABL influence the vertical exchange over BJ. In addition, we selected a typical pollution event for targeted analysis to understand mechanistic details of the influence of ABL-FT exchange on the pollution event. These results showed that ABL-FT interaction played an important role in PM2.5 concentration within the ABL during heavy pollution. Especially in the early stage of heavy pollution, FT transport contributed as much as 82.74% of PM2.5 within the ABL. These findings are significant for improving our understanding of pollution transport characteristics within the boundary layer and the effect of ABL-FT exchange on air quality.

Aerosol-boundary layer dynamics and its effect on aerosol radiative forcing and atmospheric heating rate in the Indian Ocean sector of Southern Ocean.

The study examines the thermodynamic structure of the marine atmospheric boundary layer (MABL) and its effect on the aerosol dynamics in the Indian Ocean sector of Southern Ocean (ISSO) between 30°S-67°S and 57°E-77°E. It includes observations of aerosols and meteorology collected during the Xth Southern Ocean Expedition conducted in December 2017. The results revealed the effect of frontal-region-specific air-sea coupling on the thermodynamic structure of MABL and its role in regulating aerosols in ISSO. The MABL over the subtropical front was unstable and formed a well-evolved mixed layer (≈2400 m) capped by low-level inversions (≈660 m). Convective activities in the Sub-Antarctic Frontal region were associated with the Agulhas Retroflection Current, which supported the formation of a well-developed mixed layer (≈1860 m). The mean estimates of aerosol optical depth (AOD) and black carbon (BC) mass concentrations were 0.095 ± 0.006 and 50 ± 14 ng m-3, respectively, and the resultant clear sky direct shortwave radiative forcing (DARF) and atmospheric heating rate (HR) were 1.32 ± 0.11 W m-2 and 0.022 ± 0.002 K day-1, respectively. In the polar front (PF) region, frequent mid-latitude cyclones led to highly stabilized MABL, supported low-level multi-layered clouds (>3-layers) and multiple high-level inversions (strength > 0.5 K m-1 > 3000 m). The clouds were mixed-phased with temperatures less than -12 °C at 3000 m altitude. Interestingly, there was higher loading of dust and BC aerosols (276 ± 24 ng m-3), maximum AOD (0.109 ± 0.009), clear sky DARF (1.73 ± 0.02 W m-2), and HR (0.029 ± 0.005 K day-1). This showed an accumulation of long-range advected anthropogenic aerosols within baroclinic-boundaries formed over the PF region. Specifically, in the region south of PF, weak convection caused weakly-unstable MABL with a single low-level inversion followed by no clouds/single-layer clouds. Predominant clean maritime air holding a small fraction of dust and BC accounted for lower estimates of AOD (0.071 ± 0.004), BC concentrations (90 ± 55 ng m-3) and associated clear sky DARF and HR were 1.16 ± 0.06 W m-2 and 0.019 ± 0.001 K day-1, respectively.

Source apportionments of black carbon induced by local and regional transport in the atmospheric boundary layer of the Yangtze River Delta under stable weather conditions.

Long-range transport (LRT) and local accumulation (LA) are key atmospheric physical processes affecting air pollution formation, and their impacts on surface air pollution have been extensively researched. Due to the lack of vertical observations and emphases on model simulations, the characteristics and regional sources of black carbon (BC) aerosol profiles have been relatively understudied. In this study, the chemistry-coupled Weather Research and Forecasting model (WRF-Chem) with a BC source-tagging method was used to quantify BC source contributions (considering 18 geographical regions over east Asia, including 3 subregions over the Yangtze River Delta (YRD)) during a November 2017 pollution event in the YRD, China. In this event, the YRD mainly experienced a uniform pressure field, stable weather and weak wind fields. During the uniform high-pressure period, the dominant contribution to surface BC in each sub-region was from that region itself (70.6 %-98.2 %), with little intra- and inter-regional transport. During the uniform low-pressure period, highly variable contributions to the surface BC from intra-regional transport within the YRD (0.05 %-65.9 %) and inter-regional transport outside the YRD (mostly from Anhui (AH) to the west of the YRD, 0.37 %-23.9 %) were simulated. In the vertical direction, the dominant contributors were local YRD sources (73.8 %-94.2 %) below the atmospheric boundary layer (ABL). The inter-transport contributions increased extensively above the ABL. As a westerly trough crossing, a long-range inter-regional transport from South China (SCHN, 3.3 %) and the North China Plain (NCP, 2.7 %) was simulated above the ABL. We found that when the surface experienced similar stable weather conditions, the weather conditions in the upper air may have been quite different, resulting in significant differences in the regional transport of BC in the upper ABL. This study provides a reference for improving air quality from the local scale to the regional scale.

Vertical structure of conventionally neutral atmospheric boundary layers.

SignificanceThe presented model describes the vertical structure of conventionally neutral atmospheric boundary layers. Due to the complicated interplay between buoyancy, shear, and Coriolis effects, analytical descriptions have been limited to the mean wind speed. We introduce an analytical approach based on the Ekman equations and the basis function of the universal potential temperature flux profile that allows one to describe the wind and turbulent shear stress profiles and hence capture features like the wind veer profile. The analytical profiles are validated against high-fidelity large-eddy simulations and atmospheric measurements. Our findings contribute to the scientific community's fundamental understanding of atmospheric turbulence with direct relevance for weather forecasting, climate modeling, and wind energy applications.

Climatology and trends of morning and evening surface-based temperature inversions in southwestern Pennsylvania with air quality implications.

Concerns over regional climate change include its impact on air quality. A major contributor to unhealthy air quality is surface-based temperature inversions. Poor air quality is a serious public health concern that is often addressed by public health agencies. To assist with understanding the climatology and trend of temperature inversions for a large public health department, innovative pragmatic criteria were developed and used to determine morning and evening surface-based temperature inversions from datasets derived from Pittsburgh National Weather Service (NWS) radiosonde measurements made from 1 January 1991 through 31 December 2020. During this 30-year period, the strength of the morning (7 a.m. EST; 12 UTC) inversions was 3.9 °C on average. The depth of the inversion layer measured an average height of 246 m above the ground. The inversions tended to dissipate by 10 a.m. EST. The frequency of occurrence of morning inversions averaged 47%. The mean strength of the evening (7 p.m. EST; 00 UTC) inversions was 1.1 °C with a mean depth of 101 m above the ground. The frequency of evening inversion occurrence averaged 20% during this period. The 30-year climatology revealed generally declining frequency of inversions in the Pittsburgh area. Morning surface-based inversion strengths usually declined while morning depths and break times were steady. Evening inversion strengths and depths increased overall during the 30-year period. Monthly means showed a morning-evening overlap of some months that record the most frequent substantial inversions during the fall time of the year, coinciding with the time when the worst air pollution events occur.

Mechanism of haze pollution in summer and its difference with winter in the North China Plain.

Heavy haze pollution usually occurs in winter. However, according to the enhanced atmospheric boundary layer (ABL) field experiments conducted in the North China Plain (NCP) from 17 June to 6 July 2019, heavy haze pollution may also occur in summer, although with a lower probability. Winter haze pollution is significantly affected by adverse boundary layer meteorological conditions, whereas our study shows different mechanisms of summer haze pollution from that of winter. In summer, PM2.5 is distributed uniformly as a thick layer at a lighter pollution level; however, the PM2.5 column content in summer exceeds that in winter, suggesting that the better air quality in summer is mainly due to improved diffusion conditions. In summer, even under haze conditions, the ABL can develop over 1000 m and has a large ventilation similar to clean periods, which indicates both favourable vertical diffusion conditions and advection capability of the summer ABL. Unlike in winter, the heavy haze pollution in summer is often caused by regional transport which is related to local circulation. To explore the influence of different scale systems on summer haze pollution, we applied the spectral analysis method to surface PM2.5 concentrations. Strong periodicity of PM2.5 concentrations is found in 4-9 d and 1 d, corresponding to the impacts of large-scale synoptic system changes and the ABL evolution, respectively. The influence of weather change is much stronger than that of the ABL evolution on PM2.5 concentrations in summer. The resulting changes in PM2.5 concentrations are approximately 45 µg/m3 and 15 µg/m3, respectively. There has been a consensus on the importance of emission control in winter. And this study shows that heavy haze pollution can also occur in summer and regional joint emission control should also be emphasized in summer.

Atmospheric Boundary Layer Wind Profile Estimation Using Neural Networks Applied to Lidar Measurements.

This paper introduces a new methodology for estimating the wind profile within the ABL (Atmospheric Boundary Layer) using a neural network and a single-point near-ground measurement. An important advantage of this solution when compared with others available in the literature is that it only requires near surface measurements for the prognosis once the neural network is trained. Another advantage is that it can be used to study the wind profile temporal evolution. This work uses data collected by a lidar sensor located at the Universidad de León (Spain). The neural network best configuration was determined using sensibility analyses. The result is a multilayer perceptron with three layers for each altitude: the input layer has six nodes for the last three measurements, the second has 128 nodes and the third consists of two nodes that provide u and v. The proposed method has better performance than traditional methods. The obtained wind profile information obtained is useful for multiple applications, such as preliminary calculations of the wind resource or CFD models.