Modeling Of Atmospheric Processes Research Articles

Molecular Simulation for Atmospheric Reactions: Non-Equilibrium Dynamics, Roaming, and Glycolaldehyde Formation following Photoinduced Decomposition of syn-Acetaldehyde Oxide.

The decomposition dynamics of vibrationally excited syn-CH3CHOO to form vinoxy + hydroxyl (CH2CHO + OH) radicals or to recombine to form glycolaldehyde (CH2OHCHO) are characterized using statistically significant numbers of molecular dynamics simulations using a full-dimensional neural-network-based potential energy surface at the CASPT2 level of theory. The computed final OH-translational and rotational state distributions agree well with experiments and probe the still unknown O-O bond strength DeOO for which best values from 22 to 25 kcal/mol are found. OH-elimination rates are consistent with experiments and do not vary appreciably with DeOO due to the non-equilibrium nature of the process. In addition to the OH-elimination pathway, OH roaming is observed following O-O scission, which leads to glycolaldehyde formation on the picosecond time scale. Together with recent work involving the methyl-ethyl-substituted Criegee intermediate, we conclude that OH roaming is a general pathway to be included in molecular-level modeling of atmospheric processes. This work demonstrates that atomistic simulations with machine-learned energy functions provide a viable route for exploring the chemistry and reaction dynamics of atmospheric reactions.

Уточнення чисельних метеорологічних прогнозів за допомогою глибокого навчання

This paper briefly describes the history of numerical weather prediction development. The difficulties, which occur in the modelling of atmospheric processes, their nature and possible ways of their mitigation, are described. It also indicates alternative methods of improving the quality of meteorological forecasts. A brief history of deep learning and possible ways of its application to meteorological problems are given. Then, the paper describes the format used to store the 2m temperature forecasts of the COSMO numerical regional model. The proposed neural network architecture enables correcting the forecast errors of the numerical model. We conducted the experiments on the data of eight meteorological stations of the Kyiv region, so we obtained eight trained neural network models. The results showed that the proposed architecture enables obtaining better-quality forecasts in more than 50% of cases. Root-mean-square errors of the resulting forecasts decreased, and it is a widespread skill-score of improved-quality forecasts in meteorological science.

MODERN ASPECTS OF THE IMPLEMENTATION OF THE COURSE "METEOROLOGY AND CLIMATOLOGY" IN THE EDUCATIONAL PROCESS OF STUDENTS IN THE DIRECTION OF PREPARATION 101 ECOLOGY

Modern meteorology is a very practical science necessary for social life. Most meteorologists model weather and climate forecasts, while others work for government and military organizations as well as private companies, providing forecasts for aviation, navigation, agriculture, construction, and radio and television broadcasting. In many countries, meteorology is often called "atmospheric physics", and ordinary meteorologists deal more with complex mathematical formulas and calculations that model physical and physico-chemical processes in the Earth's atmosphere. However, since the latter is closely related to all other envelopes, the work of meteorologists also has a distinct geographic element, since only geography needs to be taken into account for weather forecasting and modeling of atmospheric processes. In addition, the conditions of the atmosphere and the processes that take place in it differ in different parts of the globe due to geographic patterns (regions, altitude bands, etc.). Long-term weather conditions in a certain area are called climate. So, climatology is a science that studies such issues as climate formation, description and classification of the global climate, and the impact of human activity on the climate. By its nature, it is more closely related to other geographical disciplines.
 Modern research in the field of meteorology and climatology is at the center of mass media reports, as it sheds light on the future of our planet and life on it in light of actual and potential climate change. This is their mission today. they can only answer questions posed as elements of the system of geographic science.
 The article contains basic provisions on the environment, aspects of life in various regions, especially natural areas and objects subject to special protection. The work on environmental impact assessment is characterized. The article covers some issues of human bioclimatology, synrheological effects of individual meteorological variables and atmospheric factors and methods of assessing the complex impact of weather on the human body. The influence of climate warming on the health of the population and adaptation to climate change in Ukraine are mentioned.

Potential Climate Impacts of Reforestation and Waterlogging in Belarus

The article discusses the expected climate changes in Belarus as a result of two types of land transformation – rewetting degraded peatlands and increasing forest cover. The analysis was performed for the growing season (May–September) based on long-term Earth remote sensing data, mesoscale modeling of atmospheric processes, and balance calculations using ERA5 reanalysis. It is shown that as a result of waterlogging, the daytime temperature of the underlying surface for the southern part of Belarus (below the latitude of Minsk) decreases within 1.5°С due to increased consumption, and for the northern part – within 0.5°С due to albedo regularity. At night, waterlogging, depending on the soil and climatic conditions, can cause both an increase and a specific value of the underlying surface temperature within 1°C. Evapotranspiration due to waterlogging in the northern regions of Belarus, and in the southern regions – emissions, which is associated with a significant ratio between consumption and transpiration in these regions. During the reforestation of cropland, the daytime land surface temperature of Belarus territory decreases within 2°C, and at night – within 0.4°C. The total evapotranspiration for the growing season due to the increase in forest cover reaches 100 mm, and approaching (maximum possible) consumption remains at the same level, which overestimates soil absorption at an increased amount of atmospheric pressure. The above changes in the physical characteristics of the underlying surface as a result of reclamation determine the standard surface air temperature in the reclamated disease within 0.4°C and an increase in the sums of atmospheric conditions within 2% of the climatic norm. At the same time, secondary reactions are predominantly distributed in morbidity due to western transfer with an emphasis on the eastern border distribution to the reclaimed region.

Sensitivity of Heavy Convective Precipitation Simulations to Changes in Land‐Atmosphere Exchange Processes Over China

AbstractHeavy precipitation and associated flood hazards can cause enormous socioeconomic losses. The advances in atmospheric modeling enable great promise in accurately predicting precipitation. However, the representation of land‐atmosphere exchange processes in atmospheric models and its impacts on precipitation evolution remain high uncertainties. This study investigated the sensitivity of convective precipitation to land‐atmosphere exchanges and examined the improvements in precipitation simulations by a dynamic vegetation‐type‐dependent exchange scheme. We conducted 3‐km‐resolution convection‐permitting modeling for three heavy precipitation events that occurred over areas with different dominant land‐cover types. The results showed that land‐atmosphere exchange efficiency significantly altered the precipitation intensity as well as the onset and peak time of precipitation but hardly affected the precipitation pattern. Strong exchange simulations could agree better with the observed precipitation in the 21 July 2012 Beijing and the 19 June 2010 Jiangxi heavy precipitation events occurring over humid and semihumid zones, while weak exchange simulations could attain higher consistencies with the observations in the 30 July 2012 Ningxia heavy precipitation event occurring over arid and semiarid zones. As a more physical alternative, the dynamic exchange simulations could achieve the closest agreement with the field observations, especially the intensity and location of the heaviest rainfall. The dynamic scheme modifies land‐atmosphere exchange efficiency to match local land cover conditions and could provide promising applications in heavy precipitation modeling studies.

Rates and Yields of Unimolecular Reactions Producing Highly Oxidized Peroxy Radicals in the OH-Induced Autoxidation of α-Pinene, β-Pinene, and Limonene.

Recent ambient atmospheric measurements have detected highly oxygenated organic molecules (HOMs) at many sites and are a consequence of autoxidation processes occurring at ambient temperatures. Monoterpenes in particular have a propensity to autoxidize although they exhibit a wide range of HOM yields, which may be due to a variety of reasons including reactions with different oxidants like OH and O3, differing hydrogen (H) atom transfer or peroxy radical cyclization rates, numbers of available reaction pathways, and/or energy loss processes for activated HO-monoterpene or O3-monoterpene adducts. In this work, the autoxidation mechanisms of (+)-α-pinene, (+)-β-pinene, and (+)-limonene following initial OH oxidation and three successive O2 additions are examined using density functional theory (DFT) to understand what accounts for the disparity. Rates of different potential autoxidation pathways initiated by OH addition or abstraction reactions are quantified using transition-state theory (TST) and master equation approaches using the lowest-energy conformers. OH abstraction reactions do not appreciably influence HOM production in the pinenes and limit autoxidation for limonene because the subsequent autoxidation reactions are slow while OH addition reactions are found to be the main route to HOMs for all three monoterpenes. Generally, faster autoxidation rates are computed in later unimolecular reactions that produce RO7 radicals after OH addition (∼10 s-1 or greater) than rates for RO5 peroxy radical production (0.2-7 s-1). Mechanistic pathways that form RO7 peroxy radicals are similar for all three monoterpenes with a particular bicyclo RO7 radical involving a five-membered peroxide ring being favored for all three monoterpenes. The molar yields of RO7 radicals are 4.6% (+10.0/-2.4), 3.8% (+9.1/-2.6), and 7.6% (+13.1/-4.9) for α-pinene, β-pinene, and limonene, respectively, at 298 K and 1 ppb of NO and only significantly decline at NO concentrations exceeding 10 ppb. The higher yield for limonene relative to the pinenes is predominantly a consequence of the initial oxidation step: OH adducts of the bicyclic pinenes have to use the excess energy after OH addition to break one of the rings and make the molecule more flexible for autoxidation although this process is inefficient, while one of the prominent OH adducts for monocyclic limonene does not have to do this and may add O2 immediately before autoxidizing further. These insights may be used to guide a better representation of these processes in atmospheric models because they affect particulate matter (PM), NOx, and ozone concentrations via enhanced production of low-volatility species, less early-generation NOx cycling, and altered organic nitrate production.

Моделирование выбросов загрязняющих веществ в атмосферу города Рудный

Научная работа основана на современных методах математического моделирования атмосферных процессов, которые позволяют рассчитать, на основе статистических данных, объемы выбросов загрязняющих веществ в отдельных (контрольных) точках и строить изолинейные карты распределения концентраций загрязняющих веществ. В данной научной статье картирование уровня загрязнения атмосферы г. Рудный проводилось с учетом выбросов с территории промышленных предприятий по методике В.А. Петрухина и В.А. Вишенского, позволяющей рассчитать средние значения концентраций загрязняющих веществ по слою перемешивания. Рассмотрен вклад природных факторов в загрязнение атмосферы. Выявлены основные источники загрязнения атмосферы, приведены объёмы выбросов согласно данным стационарных постов. В работе составлены модели рассеивания загрязняющих веществ по 4 показателям.

Overview: Fusion of radar polarimetry and numerical atmospheric modelling towards an improved understanding of cloud and precipitation processes

Abstract. Cloud and precipitation processes are still a main source of uncertainties in numerical weather prediction and climate change projections. The Priority Programme “Polarimetric Radar Observations meet Atmospheric Modelling (PROM)”, funded by the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG), is guided by the hypothesis that many uncertainties relate to the lack of observations suitable to challenge the representation of cloud and precipitation processes in atmospheric models. Such observations can, however, at present be provided by the recently installed dual-polarization C-band weather radar network of the German national meteorological service in synergy with cloud radars and other instruments at German supersites and similar national networks increasingly available worldwide. While polarimetric radars potentially provide valuable in-cloud information on hydrometeor type, quantity, and microphysical cloud and precipitation processes, and atmospheric models employ increasingly complex microphysical modules, considerable knowledge gaps still exist in the interpretation of the observations and in the optimal microphysics model process formulations. PROM is a coordinated interdisciplinary effort to increase the use of polarimetric radar observations in data assimilation, which requires a thorough evaluation and improvement of parameterizations of moist processes in atmospheric models. As an overview article of the inter-journal special issue “Fusion of radar polarimetry and numerical atmospheric modelling towards an improved understanding of cloud and precipitation processes”, this article outlines the knowledge achieved in PROM during the past 2 years and gives perspectives for the next 4 years.

Turbulent vortex dynamo in the Earth’s atmosphere and the emerging opportunity to affect tropical cyclogenesis

The interpretation of tropical cyclogenesis as an extreme threshold event in the helical atmospheric turbulence allows us to discuss the idea on affecting the birth of a hurricane. A hypothetical way is based on the crucial role of the intense vortical cloud convection, known as Vortical Hot Towers, in the excitation and maintenance of large-scale helical-vortex instability. Some quantitative estimates are given, for which results of idealized cloud-resolving numerical simulation have been applied. The modern numerical modeling of atmospheric processes makes it possible to investigate and evaluate the possibilities of managing the instability, for example, on the basis of “Hurricane Nature Run.”

Spectroscopic imaging of sub-kilometer spatial structure in lower-tropospheric water vapor

Abstract. The subgrid spatial variability of water vapor is an important geophysical parameter for modeling tropical convention and cloud processes in atmospheric models. This study maps sub-kilometer spatial structures in total atmospheric column water vapor with visible to shortwave infrared (VSWIR) imaging spectroscopy. We describe our inversion approach and validate its accuracy with coincident measurements by airborne imaging spectrometers and the AERONET ground-based observation network. Next, data from NASA's AVIRIS-NG spectrometer enable the highest-resolution measurement to date of water vapor's spatial variability and scaling properties. We find second-order structure function scaling exponents consistent with prior studies of convective atmospheres. Airborne lidar data show that this total column measurement provides information about variability in the lower troposphere. We conclude by discussing the implications of these measurements and paths toward future campaigns to build upon these results.

The sub-adiabatic model as a concept for evaluating the representation and radiative effects of low-level clouds in a high-resolution atmospheric model

Abstract. The realistic representation of low-level clouds, including their radiative effects, in atmospheric models remains challenging. A sensitivity study is presented to establish a conceptual approach for the evaluation of low-level clouds and their radiative impact in a highly resolved atmospheric model. Considering simulations for six case days, the analysis supports the notion that the properties of clouds more closely match the assumptions of the sub-adiabatic rather than the vertically homogeneous cloud model, suggesting its use as the basis for evaluation. For the considered cases, 95.7 % of the variance in cloud optical thickness is explained by the variance in the liquid water path, while the droplet number concentration and the sub-adiabatic fraction contribute only 3.5 % and 0.2 % to the total variance, respectively. A mean sub-adiabatic fraction of 0.45 is found, which exhibits strong inter-day variability. Applying a principal component analysis and subsequent varimax rotation to the considered set of nine properties, four dominating modes of variability are identified, which explain 97.7 % of the total variance. The first and second components correspond to the cloud base and top height, and to liquid water path, optical thickness, and cloud geometrical extent, respectively, while the cloud droplet number concentration and the sub-adiabatic fraction are the strongest contributors to the third and fourth components. Using idealized offline radiative transfer calculations, it is confirmed that the shortwave and longwave cloud radiative effects exhibit little sensitivity to the vertical structure of clouds. This reconfirms, based on an unprecedented large set of highly resolved vertical cloud profiles, that the cloud optical thickness and the cloud top and bottom heights are the main factors dominating the shortwave and longwave radiative effect of clouds and should be evaluated together with radiative fluxes using observations to attribute model deficiencies in the radiative fluxes to deficiencies in the representation of clouds. Considering the different representations of cloud microphysical processes in atmospheric models, the analysis has been further extended and the deviations between the radiative impact of the single- and double-moment schemes are assessed. Contrasting the shortwave cloud radiative effect obtained from the double-moment scheme to that of a single-moment scheme, differences of about ∼40 W m−2 and significant scatter are observed. The differences are attributable to a higher cloud albedo resulting from the high values of droplet number concentration in particular in the boundary layer predicted by the double-moment scheme, which reach median values of around ∼600 cm−3.

Numerical Modeling of Dust Propagation in the Atmosphere of a City with Complex Terrain. The Case of Background Eastern Light Air

Micro-scale processes of dust distribution in the city of Tbilisi with very complex topography are modeled using a 3D regional model of atmospheric processes and numerical integration of the transport-diffusion equation of the impurity. The Terrain-following coordinate system is used to take into account the influence of a very complex relief on the process of atmospheric pollution. Modeling is carried out using horizontal grid steps of 300 m and 400 m along latitude and longitude, respectively. Cases of the stationary background eastern light air are considered. In the model, motor transport is considered as a nonstationary source of pollution from which dust is emitted into the atmosphere. Modeling of dust micro-scale diffusion process showed that the city air pollution depends on the spatial distribution of the main sources of city pollution, i.e. on vehicle traffic intensity, as well as on the spatial distribution of highways, and micro-orography of city and relief of the surrounding territories. It is shown that the dust pollution level in the surface layer of the atmosphere is minimal at 6 a.m. Ground-level concentration rapidly grows with the increase of vehicle traffic intensity and at 12 a.m. reaches maximum allowable concentration (MAC = 0.5 mg/m3) in the vicinity of central city mains. From 12 a.m. to 9 p.m. maximum dust concentration values are within the limits of 0.9 - 1.2 MAC. In the mentioned time interval formation of the high pollution zones, the slow growth of their areas and the value of ground-level concentrations take place. These zones are located in both central and peripheral parts of the city. Their disposition and area sizes depend on the spatial distribution of local wind-generated under the action of complex terrain, as well as on the processes of turbulent and advective dust transfer. From 9 p.m. to 24 p.m. reduction of dust pollution and ground-level concentration takes place. After midnight the city dust pollution process continues quasi-periodically.

Parallel-in-time multi-level integration of the shallow-water equations on the rotating sphere

The modeling of atmospheric processes in the context of weather and climate simulations is an important and computationally expensive challenge. The temporal integration of the underlying PDEs requires a very large number of time steps, even when the terms accounting for the propagation of fast atmospheric waves are treated implicitly. Therefore, the use of parallel-in-time integration schemes to reduce the time-to-solution is of increasing interest, particularly in the numerical weather forecasting field.We present a multi-level parallel-in-time integration method combining the Parallel Full Approximation Scheme in Space and Time (PFASST) with a spatial discretization based on Spherical Harmonics (SH). The iterative algorithm computes multiple time steps concurrently by interweaving parallel high-order fine corrections and serial corrections performed on a coarsened problem. To do that, we design a methodology relying on the spectral basis of the SH to coarsen and interpolate the problem in space.The methods are evaluated on the shallow-water equations on the sphere using a set of tests commonly used in the atmospheric flow community. We assess the convergence of PFASST-SH upon refinement in time. We also investigate the impact of the coarsening strategy on the accuracy of the scheme, and specifically on its ability to capture the high-frequency modes accumulating in the solution. Finally, we study the computational cost of PFASST-SH to demonstrate that our scheme resolves the main features of the solution multiple times faster than the serial schemes.

Relative importance of gas uptake on aerosol and ground surfaces characterized by equivalent uptake coefficients

Abstract. Quantifying the relative importance of gas uptake on the ground and aerosol surfaces helps to determine which processes should be included in atmospheric chemistry models. Gas uptake by aerosols is often characterized by an effective uptake coefficient (γeff), whereas gas uptake on the ground is usually described by a deposition velocity (Vd). For efficient comparison, we introduce an equivalent uptake coefficient (γeqv) at which the uptake flux of aerosols would equal that on the ground surface. If γeff is similar to or larger than γeqv, aerosol uptake is important and should be included in atmospheric models. In this study, we compare uptake fluxes in the planetary boundary layer (PBL) for different reactive trace gases (O3, NO2, SO2, N2O5, HNO3 and H2O2), aerosol types (mineral dust, soot, organic aerosol and sea salt aerosol), environments (urban areas, agricultural land, the Amazon forest and water bodies), seasons and mixing heights. For all investigated gases, γeqv ranges from magnitudes of 10−6–10−4 in polluted urban environments to 10−4–10−1 under pristine forest conditions. In urban areas, aerosol uptake is relevant for all species (γeff≥γeqv) and should be considered in models. On the contrary, contributions of aerosol uptakes in the Amazon forest are minor compared with the dry deposition. The phase state of aerosols could be one of the crucial factors influencing the uptake rates. Current models tend to underestimate the O3 uptake on liquid organic aerosols which can be important, especially over regions with γeff≥γeqv. H2O2 uptakes on a variety of aerosols are yet to be measured under laboratory conditions and evaluated. Given the fact that most models have considered the uptakes of these species on the ground surface, we suggest also considering the following processes in atmospheric models: N2O5 uptake by all types of aerosols, HNO3 and SO2 uptake by mineral dust and sea salt aerosols, H2O2 uptake by mineral dust, NO2 uptakes by sea salt aerosols and O3 uptake by liquid organic aerosols.

The particle dry deposition component of total deposition from air quality models: right, wrong or uncertain?

Dry deposition is an important loss process for atmospheric particles and can be a significant part of total deposition estimates calculated for critical loads analyses. However, algorithms used in large-scale air quality and atmospheric chemistry models to predict particle deposition velocity as a function of particle size are highly uncertain. Many of these algorithms, although derived from a common heritage, predict vastly different particle deposition velocities for a given particle diameter even under identical environmental conditions for major land use classes. Even more problematic, for vegetated landscapes (forests, in particular) the algorithms do not agree very well with available measurements. In this work, we perform a sensitivity study to estimate how significant the uncertainties in particle deposition algorithms may be in an air quality model’s predictions of ground-level fine particle concentrations, particle deposition and overall total deposition of nitrogen and sulfur. Our results suggest that fine particle concentration predictions at the surface may vary by 5–15% depending on the choice of particle deposition velocity algorithm, while particle dry deposition is affected to a much greater extent with differences among algorithms >200%. Moreover, if accumulation mode particle dry deposition measurements over forests are correct, then dry particle deposition and total elemental deposition to these landscapes may be much larger than is typically simulated by current air quality and atmospheric chemistry models, calling into question commonly available estimates of total deposition and their use in critical loads analyses. Since accurate predictions of atmospheric particle concentrations and deposition are critically important for future air quality, weather and climate models and management of pollutant deposition to sensitive ecosystems, an investment in new dry deposition measurements in conjunction with integrated modelling efforts seems not only justified but vitally necessary to advance and improve the treatment of particle dry deposition processes in atmospheric models.

Accretion Product Formation from Self- and Cross-Reactions of RO2 Radicals in the Atmosphere.

Hydrocarbons are emitted into the Earth's atmosphere in very large quantities by human and biogenic activities. Their atmospheric oxidation processes almost exclusively yield RO2 radicals as reactive intermediates whose atmospheric fate is not yet fully unraveled. Herein, we show that gas-phase reactions of two RO2 radicals produce accretion products composed of the carbon backbone of both reactants. The rates for accretion product formation are very high for RO2 radicals bearing functional groups, competing with those of the corresponding reactions with NO and HO2 . This pathway, which has not yet been considered in the modelling of atmospheric processes, can be important, or even dominant, for the fate of RO2 radicals in all areas of the atmosphere. Moreover, the vapor pressure of the formed accretion products can be remarkably low, characterizing them as an effective source for the secondary organic aerosol.

A Framework for Convection and Boundary Layer Parameterization Derived from Conditional Filtering

Abstract A new theoretical framework is derived for parameterization of subgrid physical processes in atmospheric models; the application to parameterization of convection and boundary layer fluxes is a particular focus. The derivation is based on conditional filtering, which uses a set of quasi-Lagrangian labels to pick out different regions of the fluid, such as convective updrafts and environment, before applying a spatial filter. This results in a set of coupled prognostic equations for the different fluid components, including subfilter-scale flux terms and entrainment/detrainment terms. The framework can accommodate different types of approaches to parameterization, such as local turbulence approaches and mass flux approaches. It provides a natural way to distinguish between local and nonlocal transport processes and makes a clearer conceptual link to schemes based on coherent structures such as convective plumes or thermals than the straightforward application of a filter without the quasi-Lagrangian labels. The framework should facilitate the unification of different approaches to parameterization by highlighting the different approximations made and by helping to ensure that budgets of energy, entropy, and momentum are handled consistently and without double counting. The framework also points to various ways in which traditional parameterizations might be extended, for example, by including additional prognostic variables. One possibility is to allow the large-scale dynamics of all the fluid components to be handled by the dynamical core. This has the potential to improve several aspects of convection–dynamics coupling, such as dynamical memory, the location of compensating subsidence, and the propagation of convection to neighboring grid columns.

The Modulation of Stationary Waves, and Their Response to Climate Change, by Parameterized Orographic Drag

Abstract The parameterization of orographic drag processes in atmospheric models remains uncertain because of a lack of observational and theoretical constraints on their formulation and free parameters. While previous studies have demonstrated that parameterized orographic drag acting near the surface has a significant impact on the atmospheric circulation, this work follows a more systematic approach to investigate its impacts on the large-scale circulation and the circulation response to climate change. A set of experiments with a comprehensive atmospheric general circulation model is used to ascertain the range of climatological circulations that may arise from parameter uncertainty. It is found that the Northern Hemisphere (NH) wintertime stationary wave field is strongly damped over the North Pacific (NP) and amplified over the North Atlantic (NA) as a result of increased low-level parameterized orographic drag, both of which are shown to be conducive to higher-latitude westerlies. A comparison with the stationary wave field presented in other studies suggests that the too-zonal NA jet and equatorward NP jet biases that are prevalent in climate models may be at least partly due to their representation of orographic drag. The amplitude of the stationary wave response to climate change across the experiments is shown to scale with the magnitude of low-level parameterized orographic drag through its influence on the present-day climatological stationary wave amplitudes over different sectors of the NH, which is consistent with linear stationary wave theory. This work highlights the importance of fidelity in a model’s basic state for regional climate change projections.

Knudsen cell studies of the uptake of gaseous ammonia and amines onto C3-C7 solid dicarboxylic acids.

While atmospheric particles affect health, visibility and climate, the details governing their formation and growth are poorly understood on a molecular level. A simple model system for understanding the interactions between the gas and particle phases is the reaction of bases with acids, both of which are common constituents of atmospheric particles. In the present study, uptake coefficients for the reactions of gas phase ammonia, methylamine, ethylamine, dimethylamine and trimethylamine with a series of solid dicarboxylic acids (diacids) were measured at 296 ± 1 K using a Knudsen cell interfaced to a quadrupole mass spectrometer. The uptake coefficients (γ) for a given amine follow an odd-even trend in carbon number of the diacid, and are larger for the odd carbon diacids. Values range from γ = 0.4 for ethylamine on malonic acid (C3) to less than ∼10-6 for ammonia and all amines on adipic (C6) and pimelic (C7) acids. Basicity or structure of the amines/ammonia alone do not explain the effect of the base on uptake. The crystal structures of the diacids also play a key role, which is especially evident for malonic acid (C3). Evaporation of aqueous mixtures of amines/ammonia with odd carbon diacids show the formation of ionic liquids (ILs) or in some cases, metastable ILs that revert back to a stable solid salt upon complete evaporation of water. The trends with amine and diacid structure provide insight into the mechanisms of uptake and molecular interactions that control it, including the formation of ionic liquid layers in some cases. The diversity in the kinetics and mechanisms involved in this relatively simple model system illustrate the challenges in accurately representing such processes in atmospheric models.

Long-sought atmospheric intermediate detected

Using a high-sensitivity spectroscopic technique, researchers have detected an elusive chemical species in a common atmospheric reaction—the formation of carbon dioxide via the combination of the engine combustion by-product carbon monoxide and hydroxyl radicals naturally formed from water (Science 2016, DOI: 10.1126/science.aag1862). The findings provide a more detailed understanding of the reaction, allowing for improved modeling of atmospheric processes that contribute to air pollution and climate change. Forty-three years ago, Ian W. M. Smith and Reinhard Zellner at the University of Cambridge proposed that the reaction proceeds through an excited hydrocarboxyl radical intermediate, HOCO•* (J. Chem. Soc. Faraday Trans. 2 1973, DOI: 10.1039/f29736901617). They noted that collisions with other molecules could deactivate HOCO•* to form HOCO•, which can then participate in other reactions. But HOCO• is so reactive and fleeting that, in all this time, no technique used to study the reaction has had the requisite sensitivity to detect HOCO•