Dry Removal Processes Research Articles

Numerical coupling of aerosol emissions, dry removal, and turbulent mixing in the E3SM Atmosphere Model version 1 (EAMv1) – Part 2: A semi-discrete error analysis framework for assessing coupling schemes

Abstract. Part 1 (Wan et al., 2024) of this study discusses the motivation and empirical evaluation of a revision to the aerosol-related numerical process coupling in the atmosphere component of the Energy Exascale Earth System Model version 1 (EAMv1) to address the previously reported issue of strong sensitivity of the simulated dust aerosol lifetime and dry removal rate to the model's vertical resolution. This paper complements that empirical justification of the revised scheme with a mathematical justification leveraging a semi-discrete analysis framework for assessing the splitting error of process coupling methods. The framework distinguishes the error due to numerical splitting from the error due to the time integration method(s) used for each individual process. Such a distinction results in a framework that provides an intuitive understanding of the causes of the splitting error. The application of this framework to the dust life cycle in EAMv1 confirms (i) that the original EAMv1 scheme artificially strengthens the effect of dry removal processes and (ii) that the revised splitting reduces that artificial strengthening. While the error analysis framework is presented in the context of the dust life cycle in EAMv1, the framework can be broadly leveraged to evaluate process coupling schemes, both in other physical problems and for any number of processes. This framework will be particularly powerful when the various process implementations support a variety of time integration approaches. Whereas traditional local truncation error approaches require separate consideration of each combination of time integration methods, this framework enables evaluation of coupling schemes independent of particular time integration approaches for each process while still allowing for the incorporation of these specific time integration errors if so desired. The framework also explains how the splitting error terms result from (i) the integration of individual processes in isolation from other processes and (ii) the choices of input state and time step size for the isolated integration of processes. Such a perspective has the potential for the rapid development of alternative coupling approaches that utilize knowledge both about the desired accuracy and about the computational costs of individual processes.

Regional HYSPLIT simulation of atmospheric transport and deposition of the Chernobyl 137Cs releases

In this work we report the results of HYSPLIT numerical simulations of the Chernobyl 137Cs atmospheric transport, dispersion, and deposition on the regional scale (~1000 km from the source) with the main focus on the analysis of the deposition processes. In the simulations we used three different gridded datasets of input meteorology and three release scenarios previously published in the literature. The resistance method and the predefined constant value of the deposition velocity (0.005 m/s) were applied to calculate dry depositions whereas an approach based on a scavenging coefficient was used for both wet in-cloud and below-cloud removals. The results were statistically evaluated against the measurements of 137Cs total depositions on the territory of Ukraine. Our simulations show considerable dependence of the HYSPLIT-predicted accumulated deposition pattern on both the input meteorology and source parameterizations. The best performance of HYSPLIT was obtained with the ERA Interim reanalysis data and the source model of Talerko (2005) and the constant deposition velocity. This simulation reproduced fairly well the spatial structure of the 137Cs contamination on the territory of Ukraine with good evaluation statistics. However, not all significant local maxima of the contamination pattern were captured clearly. Our simulations also show that dry removal processes account for approximately 50% of the total depositions in Ukraine. Both wet in-cloud and below-cloud removal mechanisms had roughly equal influence on the total amount of 137Cs radionuclides deposited on the territory of Ukraine.

Non-Plasma Based Atomic Layer Dry Removal Technology for 10nm Node and Beyond

The fabrication of nanoscale devices is increasingly relying on digital precision process engineering that goes well beyond conventional continuous etch and clean technology. Interest in atomic layer etch and clean (ALE/C) has been intensifying as it emerges as an enabling technology for advanced etch and clean applications. As features on a chip continue to decrease in size, the ability to precisely remove materials to create those features becomes increasingly difficult and vitally important. ALE/C can deliver the level of control needed by using cycles of multi-step processes that are self-limiting and remove a few atomic layers at a time, making it useful for manufacturing 3D, high aspect ratio, and other challenging structures requiring extreme precision and fidelity. COR (Chemical Oxide Removal) is a technique that removes thin layers of material using sequential self-limiting reactions and is considered one of the promising techniques for achieving the low process variability necessary in the nano-scale and atomic-scale era. The basic COR concept starts with a reaction step to form a byproduct layer, followed by a removal step to take off only this modified layer. Using gas distribution plate allows for the semi-directional etching and cleaning required to form deep, narrow structures. In this paper, non-plasma based dry removal processes such as COR is illustrated, and applications and prospects for COR will also be discussed.

Number concentration and chemical composition of ultrafine and nanoparticles from WTE (waste to energy) plants

Stack field testing at four municipal waste-to-energy (WTE) plants was conducted to investigate total number concentrations and size distributions in a size range extended towards the evaluation of ultrafine (UFP) and nanoparticle (NP) fractions with diameters smaller than 100nm and 50nm, respectively. Measurements were performed with a specifically designed sampling line, equipped with a dilution system and a particle counting device for measuring both primary particles in raw flue gases at stack conditions and the contributions of condensable origin, arising from their cooling and dilution immediately following stack release into the atmosphere. Average concentration levels detected ranged between 5×103–6×105cm−3: for all sampling conditions, ultrafine fractions largely prevailed in number size distributions, with average diameters constantly located in the nanoparticle size range. Stack concentrations appeared to be influenced by the design and process configuration of flue gas cleaning systems, with most significant effects related to the presence of wet scrubbing units and the baghouse operating temperature of dry removal processes. Chemical speciation (i.e., trace metals, anions and cations, carbonaceous compounds) of size-resolved particulate fractions was performed on one of the plants. NP and UFP composition was essentially in accordance with the most important fuel and combustion process characteristics: in particular, the presence of chlorides and metal species was consistent with the respective waste feed content and their expected behavior during combustion and flue gas cleaning processes.

Corrigendum to "Technical Note: An implementation of the dry removal processes DRY DEPosition and SEDImentation in the Modular Earth Submodel System (MESSy)" published in Atmos. Chem. Phys., 6, 4617–4632, 2006

Corrigendum to "Technical Note: An implementation of the dry removal processes DRY DEPosition and SEDImentation in the Modular Earth Submodel System (MESSy)" published in Atmos. Chem. Phys., 6, 4617–4632, 2006

Characterization of dry deposition associated with fire in plastic scrap market of West Delhi

Abstract Samples of dry deposition were collected at National Physical Laboratory during a fire incident occurred at Jwalapuri, a plastic scrap market located in west Delhi. About 2500 shops were gutted in this fire and almost 1 4 th of the city was affected by the plume. The collected samples were analyzed for Cl, NO3, SO4 and NH4. pH and Electrical Conductance of the samples were also measured. Data showed that deposition of Cl, SO4, NO3 was significantly higher than the normal conditions as reported earlier. It was estimated that respectively 21, 11, 16 and 0.2 tones of Cl, SO4, NO3 and NH4 were deposited by dry removal process during this fire incident.

Characterization of dry deposition associated with fire in plastic scrap market of west Delhi

Samples of dry deposition were collected at National Physical Laboratory during a fire incident occurred at Jwalapuri, a plastic scrap market located in west Delhi. About 2500 shops were gutted in this fire and almost 1 4 th of the city was affected by the plume. The collected samples were analyzed for Cl, NO 3, SO 4 and NH 4. pH and Electrical Conductance of the samples were also measured. Data showed that deposition of Cl, SO 4, NO 3 was significantly higher than the normal conditions as reported earlier. It was estimated that respectively 21, 11, 16 and 0.2 tones of Cl, SO 4, NO 3 and NH 4 were deposited by dry removal process during this fire incident.

The origin of Arctic air pollutants: lessons learned and future research

Results of various studies on the origin of Arctic air pollution are reviewed, focusing on what is known about its physical characteristics and chemical composition, as well as on emission sources and major pathways of pollutant transport to the region. Emissions from anthropogenic sources in Eurasia have been found to be a major contributor to Arctic air pollution measured at altitudes of up to 2–3 km in the atmosphere during winter. During sporadic summer transport of pollutants to the region, emissions from sources in Europe seem to be more important than those from other sources. Polluted air masses, carrying a mixture of anthropogenic and natural air pollutants from a variety of sources in different geographical regions, have been identified in the Arctic at altitudes of 4–5 km during both summer and winter. Long-range transport of airborne loess from deserts in Asia and Africa to the Arctic at these altitudes was suggested. Model calculations indicate that <10% of pollutants emitted in the major source regions is deposited in the Arctic, although our knowledge on wet and dry removal processes in this region is very incomplete. Maximum concentrations of sulfates and fine particles in the Arctic were observed at the beginning of the 1980s. No major changes in concentrations were observed during the 1980s and some decrease was measured at selected stations at the end of that period. This decrease, particularly in lead and fine particle concentrations, was related to the decrease in their emissions in some source regions. A meteorological shift was also suggested as a possible cause of the decrease in concentration. Major gaps in information on sources, pathways and behavior of pollutants in the Arctic are identified. Current research programs that should improve our understanding of the origins and environmental effects of Arctic air pollution are presented.

Two‐dimensional simulations of possible mesoscale effects of nuclear war fires: 2. Model results

The two‐dimensional mesoscale meteorological model and the aerosol model described in the companion paper by Giorgi [this issue] are used to investigate mesoscale effects induced by atmospheric injections of purely absorbing smoke from nuclear war fires. Simulations are carried out for different fire types (city center, suburban, and forest fires), aerosol loadings, particle properties, and atmospheric conditions. We analyze three effects which develop on spatial scales of 10–500 km and time scales of 1–2 days and can be important for assessments of environmental impacts of nuclear war: (1) smoke‐induced formation of clouds and precipitation and efficiency of smoke removal; (2) smoke vertical transport; and (3) surface cooling induced by the smoke absorption. In convectively unstable and moist environments the low‐level uplifting induced by the smoke heating can initiate convective precipitation. In the absence of substantial moisture sources from the fires, precipitation develops mostly at the edges of the smoke plumes and is associated with the inhomogeneities in the smoke distribution, since these allow low‐level smoke heating. When the smoke is dispersed by the atmospheric winds and attains a more homogeneous distribution, most of the heating takes place at more stable higher altitudes, the smoke shielding stabilizes the lower troposphere and precipitation formation is hindered. Wet removal dominates dry removal processes and its efficiency depends on the properties and vertical distribution of the injected aerosol. In a wide variety of experiments, the fraction of the total injected smoke mass removed during 48 hour simulations varied from 3 to 20% for injections from suburban fires, from 10 to 20% for forest fires, and about 1% for city center fires. It is also shown that substantial moisture sources from the fires can significantly enhance precipitation formation and removal. Early after injection, when the individual smoke plumes have not yet merged together, self‐lofting in the upper regions of the plumes and cloud updrafts in the presence of smoke‐induced deep convection carry out most of the smoke vertical transport. At later stages, when the smoke is progressively dispersed by the atmospheric winds, the smoke heating generates a region of relatively weak stability in the upper troposphere overlying a midtropospheric inversion. As a result, upper tropospheric smoke is efficiently uplifted, while lower tropospheric smoke is trapped near the surface. In our simulations, after 48 hours of model time, 34–37% of the smoke mass is transported above 280 mbar for city center fires and 5–12% for suburban fires (with 25–30% above 500 mbar). In the case of forest fires, 80–90% of the smoke remains trapped below 500 mbar. For vegetated surfaces, the canopy foliage temperature is more sensitive to depleted insolation than the ground temperature (by up to several degrees) and as such could be a better indicator for assessments of ecological impacts of nuclear war. For dry environments and large smoke loadings, our calculated canopy foliage coolings reach 25–30 K for the peak daytime temperature and 6–7 K for the minimum nighttime temperature. They decrease for increasing atmospheric water vapor, soil moisture, and surface layer winds. We give an example of conditions that can lead to foliage frosting but not ground freezing during the quick‐freezing episodes predicted by recent general circulation model studies. We finally discuss how our results can be used in the design of injection scenarios for general circulation model simulations.