Assessment of near-surface air pollutants at an urban station over the central Indo-Gangetic Basin: Role of pollution transport pathways

Abstract Submesoscale structures fill the ocean surface, and recent numerical simulations and indirect observations suggest that they may extend to the ocean interior. It remains unclear, however, how far-reaching their impact may be—in both space and time, from weather to climate scales. Here transport pathways and the ultimate fate of the Irminger Current water from the continental slope to Labrador Sea interior are investigated through regional ocean simulations. Submesoscale processes modulate this transport and in turn the stratification of the Labrador Sea interior, by controlling the characteristics of the coherent vortices formed along West Greenland. Submesoscale circulations modify and control the Labrador Sea contribution to the global meridional overturning, with a linear relationship between time-averaged near surface vorticity and/or frontogenetic tendency along the west coast of Greenland, and volume of convected water. This research puts into contest the lesser role of the Labrador Sea in the overall control of the state of the MOC argued through the analysis of recent OSNAP (Overturning in the Subpolar North Atlantic Program) data with respect to estimates from climate models. It also confirms that submesoscale turbulence scales-up to climate relevance, pointing to the urgency of including its advective contribution in Earth systems models.

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Transport of Antarctic stratospheric strongly dehydrated air into the troposphere observed during the HALO-ESMVal campaign 2012

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-7895-2015 ◽

2015 ◽

Vol 15 (6) ◽

pp. 7895-7932 ◽

Cited By ~ 2

Author(s):

C. Rolf ◽

A. Afchine ◽

H. Bozem ◽

B. Buchholz ◽

V. Ebert ◽

...

Keyword(s):

Water Vapor ◽

Exchange Process ◽

Satellite Measurements ◽

Transport Barrier ◽

Transport Pathways ◽

Near Surface ◽

Air Masses ◽

The Antarctic

Abstract. Dehydration in the Antarctic winter stratosphere is a well-known phenomenon that is occasionally observed by balloon-borne and satellite measurements. However, in-situ measurements of dehydration in the Antarctic vortex are very rare. Here, we present detailed observations with the in-situ and GLORIA remote sensing instrument payload aboard the new German aircraft HALO. Strongly dehydrated air masses down to 1.6 ppmv of water vapor were observed as far north as 47° S and between 12 and 13 km in altitude, which has never been observed by satellites. The dehydration can be traced back to individual ice formation events, where ice crystals sedimented out and water vapor was irreversibly removed. Within these dehydrated stratospheric air masses, filaments of moister air reaching down to the tropopause are detected with the high resolution limb sounder, GLORIA. Furthermore, dehydrated air masses are observed with GLORIA in the Antarctic troposphere down to 7 km. With the help of a backward trajectory analysis, a tropospheric origin of the moist filaments in the vortex can be identified, while the dry air masses in the troposphere have stratospheric origins. The transport pathways of Antarctic stratosphere/troposphere exchange are investigated and the irrelevant role of the Antarctic thermal tropopause as a transport barrier is confirmed. Further, it is shown that the exchange process can be attributed to several successive Rossby wave events in combination with an isentropic interchange of air masses across the weak tropopause and subsequent subsidence due to radiative cooling. Once transported to the troposphere, air masses with stratospheric origin are able to reach near-surface levels within 1–2 months.

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Characteristics of near-surface air pollutants at an urban station in the central Indo-Gangetic Basin

MAUSAM ◽

10.54302/mausam.v71i2.23 ◽

2021 ◽

Vol 71 (2) ◽

pp. 245-254

Author(s):

KUMAR SUNIL ◽

SRIVASTAVA A K ◽

PATHAK V

Keyword(s):

Air Pollutants ◽

Monsoon Season ◽

Ambient Air ◽

Industrial Site ◽

Urban Station ◽

Near Surface ◽

Residential Site ◽

Post Monsoon ◽

Post Monsoon Season ◽

Mass Concentrations

Measurements of near-surface air pollutants at an urban station, Lucknow have been studied at two contrasting sites as residential and industrial during three-year period from 2015 to 2017 to understand their variability on different temporal scales. The annual mean mass concentrations of sulphur dioxide (SO2), nitrogen dioxide (NO2), nitric oxide (NO) and particulate matter of size less than 2.5 µm (PM2.5) at an industrial site were about 10 ± 5, 28 ± 17, 10 ± 11 and 128 ± 99 µg m-3 and at the residential site were about 8 ± 5, 30 ± 21, 9 ± 7 and 102 ± 81 µg m-3 respectively. It was observed that the annual mean mass concentration of PM2.5 was about 3 times higher than its annual National Ambient Air Quality Standards (NAAQS) level. However, SO2 and NO2 were about 5 and 1.5 times lower to their annual NAAQS levels, respectively. The seasonal mean mass concentrations of all the pollutants were found to be highest during the winter/post-monsoon season at both the sites, which are more pronounced at industrial site compared to residential site. The observed high pollutants over the station during the winter/post-monsoon season were found to be largely associated with the air mass back-trajectories from N-NW direction.

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Applications of Energy Beams in Material and Device Processing

MRS Proceedings ◽

10.1557/proc-23-25 ◽

1983 ◽

Vol 23 ◽

Author(s):

G.J. Galvin ◽

L.S. Hung ◽

J.W. Mayer ◽

M. Nastasi

Keyword(s):

Ion Beam ◽

High Energy ◽

Ion Beams ◽

Traditional Role ◽

Near Surface ◽

Device Processing ◽

Composition Modification ◽

Directed Energy ◽

Transistor Fabrication

ABSTRACTEnergetic ion beams used outside the traditional role of ion implantation are considered for semiconductor applications involving interface modification for self-aligned silicide contacts, composition modification for formation of buried oxide layers in Si on insulator structures and reduced disorder in high energy ion beam annealing for buried collectors in transistor fabrication. In metals, aside from their use in modification of the composition of near surface regions, energetic ion beams are being investigated for structural modification in crystalline to amorphous transitions. Pulsed beams of photons and electrons are used as directed energy sources in rapid solidification. Here, we consider the role of temperature gradients and impurities in epitaxial growth of silicon.

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A warm jet in a cold ocean

Nature Communications ◽

10.1038/s41467-021-22505-5 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Jennifer A. MacKinnon ◽

Harper L. Simmons ◽

John Hargrove ◽

Jim Thomson ◽

Thomas Peacock ◽

...

Keyword(s):

The Arctic ◽

Bering Strait ◽

Near Surface ◽

Ice Melt ◽

Beaufort Gyre ◽

The Pacific ◽

Climate Simulations ◽

Initial Evolution ◽

Forecast Models

AbstractUnprecedented quantities of heat are entering the Pacific sector of the Arctic Ocean through Bering Strait, particularly during summer months. Though some heat is lost to the atmosphere during autumn cooling, a significant fraction of the incoming warm, salty water subducts (dives beneath) below a cooler fresher layer of near-surface water, subsequently extending hundreds of kilometers into the Beaufort Gyre. Upward turbulent mixing of these sub-surface pockets of heat is likely accelerating sea ice melt in the region. This Pacific-origin water brings both heat and unique biogeochemical properties, contributing to a changing Arctic ecosystem. However, our ability to understand or forecast the role of this incoming water mass has been hampered by lack of understanding of the physical processes controlling subduction and evolution of this this warm water. Crucially, the processes seen here occur at small horizontal scales not resolved by regional forecast models or climate simulations; new parameterizations must be developed that accurately represent the physics. Here we present novel high resolution observations showing the detailed process of subduction and initial evolution of warm Pacific-origin water in the southern Beaufort Gyre.

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Extreme Surface Winds During Landfalling Atmospheric Rivers: The Modulating Role of Near-Surface Stability

Journal of Hydrometeorology ◽

10.1175/jhm-d-20-0165.1 ◽

2021 ◽

Author(s):

Terence J. Pagano ◽

Duane E. Waliser ◽

Bin Guan ◽

Hengchun Ye ◽

F. Martin Ralph ◽

...

Keyword(s):

Water Vapor ◽

Static Stability ◽

Vapor Transport ◽

Water Vapor Transport ◽

Surface Winds ◽

Near Surface ◽

Extreme Surface ◽

Atmospheric Rivers ◽

Explained Variance

AbstractAtmospheric rivers (ARs) are long and narrow regions of strong horizontal water vapor transport. Upon landfall, ARs are typically associated with heavy precipitation and strong surface winds. A quantitative understanding of the atmospheric conditions that favor extreme surface winds during ARs has implications for anticipating and managing various impacts associated with these potentially hazardous events. Here, a global AR database (1999–2014) with relevant information from MERRA-2 reanalysis, QuikSCAT and AIRS satellite observations are used to better understand and quantify the role of near-surface static stability in modulating surface winds during landfalling ARs. The temperature difference between the surface and 1 km MSL (ΔT; used here as a proxy for near-surface static stability), and integrated water vapor transport (IVT) are analyzed to quantify their relationships to surface winds using bivariate linear regression. In four regions where AR landfalls are common, the MERRA-2-based results indicate that IVT accounts for 22-38% of the variance in surface wind speed. Combining ΔT with IVT increases the explained variance to 36-52%. Substitution of QuikSCAT surface winds and AIRS ΔT in place of the MERRA-2 data largely preserves this relationship (e.g., 44% compared to 52% explained variance for USA West Coast). Use of an alternate static stability measure–the bulk Richardson number–yields a similar explained variance (47%). Lastly, AR cases within the top and bottom 25% of near-surface static stability indicate that extreme surface winds (gale or higher) are more likely to occur in unstable conditions (5.3%/14.7% during weak/strong IVT) than in stable conditions (0.58%/6.15%).

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Decomposing the time-mean Atlantic Meridional Overturning Circulation and its variability with latitude.

10.5194/egusphere-egu21-1164 ◽

2021 ◽

Author(s):

Tomas Jonathan ◽

Mike Bell ◽

Helen Johnson ◽

David Marshall

Keyword(s):

Global Climate ◽

Dominant Role ◽

Meridional Overturning Circulation ◽

Western Boundary ◽

Relative Role ◽

Overturning Circulation ◽

Near Surface ◽

Boundary Density ◽

Meridional Overturning

The Atlantic Meridional Overturning Circulations (AMOC) is crucial to our global climate, transporting heat and nutrients around the globe. Detecting&#160; potential climate change signals first requires a careful characterisation of inherent natural AMOC variability. Using a hierarchy of global coupled model&#160; control runs (HadGEM-GC3.1, HighResMIP) we decompose the overturning circulation as the sum of (near surface) Ekman, (depth-dependent) bottom velocity, eastern and western boundary density components, as a function of latitude. This decomposition proves a useful low-dimensional characterisation of the full 3-D overturning circulation. In particular, the decomposition provides a means to investigate and quantify the constraints which boundary information imposes on the overturning, and the relative role of eastern versus western contributions on different timescales.&#160;The basin-wide time-mean contribution of each boundary component to the expected streamfunction is investigated as a function of depth, latitude and spatial resolution. Regression modelling supplemented by Correlation Adjusted coRrelation (CAR) score diagnostics provide a natural ranking of the contributions of the various components in explaining the variability of the total streamfunction. Results reveal the dominant role of the bottom component, western boundary and Ekman components at short time-scales, and of boundary density components at decadal and longer timescales.

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Evaluating the role of soil physical properties on simulated land-atmosphere interactions over South Africa using coupled atmosphere-hydrological modeling

10.5194/egusphere-egu21-9418 ◽

2021 ◽

Author(s):

Zhenyu Zhang ◽

Patrick Laux ◽

Joël Arnault ◽

Jianhui Wei ◽

Jussi Baade ◽

...

Keyword(s):

South Africa ◽

Physical Properties ◽

Land Degradation ◽

Land Surface ◽

Soil Physical Properties ◽

Near Surface ◽

Soil Database ◽

Global Soil ◽

The Impact

Land degradation with its direct impact on vegetation, surface soil layers and land surface albedo, has great relevance with the climate system. Assessing the climatic and ecological effects induced by land degradation requires a precise understanding of the interaction between the land surface and atmosphere. In coupled land-atmosphere modeling, the low boundary conditions impact the thermal and hydraulic exchanges at the land surface, therefore regulates the overlying atmosphere by land-atmosphere feedback processes. However, those land-atmosphere interactions are not convincingly represented in coupled land-atmosphere modeling applications. It is partly due to an approximate representation of hydrological processes in land surface modeling. Another source of uncertainties relates to the generalization of soil physical properties in the modeling system. This study focuses on the role of the prescribed physical properties of soil in high-resolution land surface-atmosphere simulations over South Africa. The model used here is the hydrologically-enhanced Weather Research and Forecasting (WRF-Hydro) model. Four commonly used global soil datasets obtained from UN Food and Agriculture Organization (FAO) soil database, Harmonized World Soil Database (HWSD), Global Soil Dataset for Earth System Model (GSDE), and SoilGrids dataset, are incorporated within the WRF-Hydro experiments for investigating the impact of soil information on land-atmosphere interactions. The simulation results of near-surface temperature, skin temperature, and surface energy fluxes are presented and compared to observational-based reference dataset. It is found that simulated soil moisture is largely influenced by soil texture features, which affects its feedback to the atmosphere.

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Air Quality and Climate Change, Topic 3 of the Model Inter-Comparison Study for Asia Phase III (MICS-Asia III), Part I: overview and model evaluation

10.5194/acp-2017-731 ◽

2017 ◽

Cited By ~ 1

Author(s):

Meng Gao ◽

Zhiwei Han ◽

Zirui Liu ◽

Meng Li ◽

Jinyuan Xin ◽

...

Keyword(s):

Air Quality ◽

Model Evaluation ◽

Air Pollutants ◽

North China ◽

Correlation Coefficients ◽

Phase Iii ◽

Comparison Study ◽

Model Ensemble ◽

Near Surface ◽

Ensemble Mean

Abstract. Topic 3 of the Model Inter-Comparison Study for Asia (MICS-Asia) Phase III examines how online coupled air quality models perform in simulating high aerosol pollution in the North China Plain region during wintertime haze events and evaluates the importance of aerosol radiative and microphysical feedbacks. A comprehensive overview of the MICS-ASIA III Topic 3 study design, including descriptions of participating models and model inputs, the experimental designs, and results of model evaluation, are presented. Two winter months (January 2010 and January 2013) were selected as study periods, when severe haze occurred in North China. Simulations were designed to evaluate radiative and microphysical feedbacks, together and separately, relative to simulations without feedbacks. Six modeling groups from China, Korea and the United States submitted results from seven applications of online coupled chemistry-meteorology models. Results are compared to meteorology and air quality measurements, including the Campaign on Atmospheric Aerosol Research Network of China (CARE-China) network, and the Acid Deposition Monitoring Network in East Asia (EANET). The analysis focuses on model evaluations and aerosol effects on meteorology and air quality, and potentially other interesting topics, such as the impacts of model resolutions on aerosol-radiation-weather interactions. The model evaluations for January 2010 show that current online-coupled meteorology-chemistry model can generally well reproduced meteorological features and variations of major air pollutants, including aerosol concentrations. The correlation coefficients between multi-model ensemble mean and observed near-surface temperature, water vapor mixing ratio and wind speeds can reach as high as 0.99, 0.99 and 0.98. The correlation coefficients between multi-model ensemble mean and the CARE-China observed near-surface air pollutants range from 0.51 to 0.94 (0.51 for ozone and 0.94 for PM2.5). However, large discrepancies exist between simulated aerosol chemical compositions from different models, which is due to different parameterizations of chemical reactions. The coefficient of variation (standard deviation divided by average) can reach above 1.3 for sulfate in Beijing, and above 1.6 for nitrate and organic aerosol in coastal regions, indicating these compositions are less consistent from different models. During clean periods, simulated Aerosol Optical Depths (AOD) from different models are consistent, but peak values differ during severe haze event, which can be explained by the differences in simulated inorganic aerosol concentrations and the hygroscopic growth efficiency (affected by varied RH). These results provide some brief senses of how current online-coupled meteorology-chemistry models reproduce severe haze events, and some directions for future model improvements.

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Pre-monsoon air quality over Lumbini, a world heritage site along the Himalayan foothills

10.5194/acp-2016-430 ◽

2016 ◽

Cited By ~ 2

Author(s):

Dipesh Rupakheti ◽

Bhupesh Adhikary ◽

Puppala S. Praveen ◽

Maheswar Rupakheti ◽

Shichang Kang ◽

...

Keyword(s):

Air Pollution ◽

Air Quality ◽

Forest Fires ◽

Air Pollutants ◽

Transport Model ◽

World Heritage ◽

World Heritage Site ◽

Pollution Level ◽

Pollution Transport ◽

Heritage Site

Abstract. Lumbini, in southern Nepal, is a UNESCO world heritage site of universal value as the birthplace of Buddha. Poor air quality in Lumbini and surrounding regions is a great concern for public health as well as for preservation, protection and promotion of Buddhist heritage and culture. We present here results from measurements of ambient concentrations of key air pollutants (PM, BC, CO, O3) in Lumbini, first of its kind for Lumbini, conducted during an intensive measurement period of three months (April–June 2013) in the pre-monsoon season. The measurements were carried out as a part of the international air pollution measurement campaign; SusKat-ABC (Sustainable Atmosphere for the Kathmandu Valley – Atmospheric Brown Clouds). The ranges of hourly average concentrations were: PM10: 10.5–604.0 µg m−3, PM2.5: 6.1–272.2 µg m−3; BC: 0.3–30.0 µg m−3; CO: 125.0–1430.0 ppbv; and O3: 1.0–118.1 ppbv. These levels are comparable to other very heavily polluted sites throughout South Asia. The 24-h average PM2.5 and PM10 concentrations exceeded the WHO guideline very frequently (94 % and 85 % of the sampled period, respectively), which implies significant health risks for the residents and visitors in the region. These air pollutants exhibited clear diurnal cycles with high values in the morning and evening. During the study period, the worst air pollution episodes were mainly due to agro-residue burning and regional forest fires combined with meteorological conditions conducive of pollution transport to Lumbini. Fossil fuel combustion also contributed significantly, accounting for more than half of the ambient BC concentration according to aerosol spectral light absorption coefficients obtained in Lumbini. WRF-STEM, a regional chemical transport model, was used to simulate the meteorology and the concentrations of pollutants. The model was able to reproduce the variation in the pollutant concentrations well; however, estimated values were 1.5 to 5 times lower than the observed concentrations for CO and PM10 respectively. Regionally tagged CO tracers showed the majority of CO came from the upwind region of Ganges valley. The model was also used to examine the chemical composition of the aerosol mixture, indicating that organic carbon was the main constituent of fine mode PM2.5, followed by mineral dust. Given the high pollution level, there is a clear and urgent need for setting up a network of long-term air quality monitoring stations in the greater Lumbini region.

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