articles+ search results

Ecology, Ecologie, Glaciology, Glaciologie, Geology, Géologie, Geophysics, Géophysique, Climatology, meteorology, Climatologie, météorologie, Sciences exactes et technologie, Exact sciences and technology, Terre, ocean, espace, Earth, ocean, space, Geophysique externe, External geophysics, Météorologie, Meteorology, Vents et leurs effets, Winds and their effects, Climatologie, Climatology, Climatología, Distribution vent, Wind field, Distribución viento, Rafale, Gust, Ráfaga, Valeur extrême, extreme value, Variation annuelle, annual variations, Variación anual, Variation interannuelle, Interannual variation, Variación interanual, Vent surface, Surface wind, Viento superficial, Vitesse vent, Wind velocity, and Velocidad viento

The climate of the northeast Atlantic region comprises substantial decadal variability in storminess. It also exhibits strong inter- and intra-annual variability in extreme high and low wind speed episodes. Here the authors quantify and discuss causes of the variability seen in the U.K. wind climate over the recent period 1980-2010. Variations in U.K. hourly mean (HM) wind speeds, in daily maximum gust speeds and in associated wind direction measurements, made at standard 10-m height and recorded across a network of 40 stations, are considered. The Weibull distribution is shown to generally provide a good fit to the hourly wind data, albeit with the shape parameter k spatially varying from 1.4 to 2.1, highlighting that the commonly assumed k = 2 Rayleigh distribution is not universal. It is found that the 10th and 50th percentile HM wind speeds have declined significantly over this specific period, while still incorporating a peak in the early 1990s. The authors' analyses place the particularly low wind year of 2010 into longer-term context and their findings are compared with other recent international studies. Wind variability is also quantified and discussed in terms of variations in the exceedance of key wind speed thresholds of relevance to the insurance and wind energy industries. Associated interannual variability in energy density and potential wind power output of the order of ±20% around the mean is revealed. While 40% of network average winds are in the southwest quadrant, 51 % of energy in the wind is associated with this sector. The findings are discussed in the context of current existing challenges to improve predictability in the Euro-Atlantic sector over all time scales.

Environment, Environnement, Multidisciplinary, Multidisciplinaire, Sciences biologiques et medicales, Biological and medical sciences, Sciences biologiques fondamentales et appliquees. Psychologie, Fundamental and applied biological sciences. Psychology, Ecologie animale, vegetale et microbienne, Animal, plant and microbial ecology, Ecologie appliquée, Applied ecology, Ecotoxicologie, effets biologiques de la pollution, Ecotoxicology, biological effects of pollution, Ecosystèmes marins et saumâtres, Marine and brackish environment, Algae, Algue nuisible, Harmful alga, Alga nociva, Atmosphère, Atmosphere, Atmósfera, Bloom, Dépôt, Deposition, Depósito, Ecosystème, Ecosystem, Ecosistema, Interaction, Interacción, Milieu marin, Marine environment, Medio marino, Ozone, Ozono, Pollution air, Air pollution, Contaminación aire, Pollution eau, Water pollution, Contaminación agua, Zone côtière, Coastal zone, Zona costera, Zone urbaine, Urban area, Zona urbana, Mégapole, Megacity, Megaciudad, Coastal zone management, Harmful algal blooms, and Marine pollution

Megacities are not only important drivers for socio-economic development but also sources of environmental challenges. Many megacities and large urban agglomerations are located in the coastal zone where land, atmosphere, and ocean meet, posing multiple environmental challenges which we consider here. The atmospheric flow around megacities is complicated by urban heat island effects and topographic flows and sea breezes and influences air pollution and human health. The outflow of polluted air over the ocean perturbs biogeochemical processes. Contaminant inputs can damage downstream coastal zone ecosystem function and resources including fisheries, induce harmful algal blooms and feedback to the atmosphere via marine emissions. The scale of influence of megacities in the coastal zone is hundreds to thousands of kilometers in the atmosphere and tens to hundreds of kilometers in the ocean. We list research needs to further our understanding of coastal megacities with the ultimate aim to improve their environmental management.

Biotechnology, Biotechnologies, Ecology, Ecologie, Energy, Énergie, Environment, Environnement, Pollution, Sciences exactes et technologie, Exact sciences and technology, Terre, ocean, espace, Earth, ocean, space, Geophysique externe, External geophysics, Météorologie, Meteorology, Convection, turbulence, diffusion. Structure et dynamique de la couche limite atmosphérique, Convection, turbulence, diffusion. Boundary layer structure and dynamics, Composition et réactions chimiques. Interactions et processus ioniques, Chemical composition and interactions. Ionic interactions and processes, Atmosphère marine, Marine atmosphere, Atmósfera marina, Chimie atmosphérique, Atmospheric chemistry, Couche limite atmosphérique, Atmospheric boundary layer, Capa límite atmosférico, Halogène Composé, halogens compounds, Halógeno, Interface air mer, air-sea interface, Interfase aire mar, Masse air, Air mass, Masa aire, Modèle 1 dimension, one-dimensional models, Modelo 1 dimensión, Relation source puits, Source sink relationship, Relación fuente sumidero, Simulation numérique, digital simulation, and Simulación numérica

We used a one-dimensional model to simulate the chemical evolution of air masses in the tropical Atlantic Ocean, with a focus on halogen chemistry. The model results were compared to the observations of inorganic halogen species made in this region. The model could largely reproduce the measurements of most chlorine species, especially under unpolluted conditions, but overestimated sea salt chloride, BrCl, and bromine species. Agreement with the measurements could be improved by taking into account the reactivity with aldehydes and the effects of dimethyl sulfide (DMS) and Saharan dust on aerosol pH; a hypothetical HOX → X― aqueous-phase reaction could also improve the agreement with measured Cl2 and HOCl, especially under semipolluted conditions. The results also showed that halogens speciation and concentrations are very sensitive to cloud processing. The model was used to calculate the impact of the observed levels of halogens: Cl atoms accounted for 5.4―11.6% of total methane sinks and halogens (mostly bromine and iodine) accounted for 35―40% of total ozone destruction.

Environment, Environnement, Climatology, meteorology, Climatologie, météorologie, Pollution, Sciences exactes et technologie, Exact sciences and technology, Terre, ocean, espace, Earth, ocean, space, Geophysique externe, External geophysics, Météorologie, Meteorology, Composition et réactions chimiques. Interactions et processus ioniques, Chemical composition and interactions. Ionic interactions and processes, Analyse sensibilité, sensitivity analysis, Aérosol, aerosols, Aerosol, Chimie atmosphérique, Atmospheric chemistry, Couche limite atmosphérique, Atmospheric boundary layer, Capa límite atmosférico, Déplétion, Depletion, Depleción, Modèle boîte, Box model, Modelo caja, Modèle chimique, Chemical model, Modelo químico, Mécanisme réaction, Reaction mechanism, Mecanismo reacción, Neige, snow, Nieve, Ozone, ozone, Ozono, Printemps, Spring(season), Primavera, Réaction hétérogène, Heterogeneous reaction, Reacción heterogénea, Système multiphase, Multiphase system, Sistema multifase, Zone polaire, Polar region, Zona polar, Chemical processes, Ozone depletion events, Polar spring, and Sensitivity studies

Near-total depletions of ozone have been observed in the Arctic spring since the mid 1980s. The autocatalytic reaction cycles involving reactive halogens are now recognized to be of main importance for ozone depletion events in the polar boundary layer. We present sensitivity studies using the model MISTRA in the box-model mode on the influence of chemical species on these ozone depletion processes. In order to test the sensitivity of the chemistry under polar conditions, we compared base runs undergoing fluxes of either Br2, BrCl, or C12 to induce ozone depletions, with similar runs including a modification of the chemical conditions. The role of HCHO, H2O2, DMS, C12, C2H6, HONO, NO2, and RONO2 was investigated. Cases with elevated mixing ratios of HCHO, H202, DMS, C12, and HONO induced a shift in bromine speciation from Br/BrO to HOBr/HBr, while high mixing ratios of C2H6 induced a shift from HOBr/HBr to Br/BrO. The shifts from Br/BrO to HOBr/HBr accelerated the aerosol debromination, but also increased the total amount of deposited bromine at the surface (mainly via increased deposition of HOBr). For all NOy species studied (HONO, N02, RONO2) the chemistry is characterized by an increased bromine deposition on snow reducing the amount of reactive bromine in the air. Ozone is less depleted under conditions of high mixing ratios of NOx. The production of HNO3 led to the acid displacement of HCl, and the release of chlorine out of salt aerosol (C12 or BrCl) increased.

CHEMICAL models, ATMOSPHERIC chemistry, ATMOSPHERIC models, COMMUNITIES, and MICROPHYSICS

We present MISTRA-v9.0, a one dimensional (1D) atmospheric chemistry model. The model includes a detailed particle description with regards to the microphysics, gas-particle interactions, and liquid phase chemistry within particles. Version 9.0 is the first release of MISTRA as an open-source community model. A major review of the code has been performed along with this public version release to improve the user-friendliness and platform-independence of the model. In the past 20 years, MISTRA has been used in over 25 studies to address a wide range of scientific questions. The purpose of this public release is to maximise the benefit of MISTRA to the community by making the model freely available and easier to use and develop. This paper presents a thorough description of the model characteristics and components. We show some examples of simulations reproducing previous studies with MISTRA, finding that version 9.0 is consistent with previous versions. [ABSTRACT FROM AUTHOR]

Astronomy earth cosmic environment, Astronomie et environnement cosmique terrestre, Geophysics, Géophysique, Climatology, meteorology, Climatologie, météorologie, Oceanography, Océanographie, Sciences exactes et technologie, Exact sciences and technology, Terre, ocean, espace, Earth, ocean, space, Geophysique externe, External geophysics, Météorologie, Meteorology, Particules et aérosols, Particles and aerosols, Acidité, Acidity, Acidez, Atmosphère marine, Marine atmosphere, Atmósfera marina, Aérosol, Aerosols, Aerosol, Chlorure, Chlorides, Cloruro, Concentration, Concentración, Couche limite atmosphérique, Atmospheric boundary layer, Capa límite atmosférico, Humidité relative, Relative humidity, Humedad relativa, Hydrogène Chlorure, Hydrogen Chlorides, Hidrógeno Cloruro, Partage phase, Phase partition, Repartición fase, Sel marin, Sea salt, Sal marina, Solution analytique, Analytical solution, Teneur eau, Water content, Dosis agua, and pH

Calculations of the pH of sea salt aerosol particles show that the pH decreases with increasing relative humidity and therefore increasing liquid water content of the particles. We show that this puzzling effect is a result of the high concentration of chloride in the particles and the phase partitioning of HCl between the gas and aqueous phase, that makes the gas phase act as a reservoir for acidity for the sea salt particles. Implications for the marine boundary layer are briefly discussed.

Geology, Géologie, Climatology, meteorology, Climatologie, météorologie, Oceanography, Océanographie, Sciences exactes et technologie, Exact sciences and technology, Terre, ocean, espace, Earth, ocean, space, Sciences de la terre, Earth sciences, Géochimie, Geochemistry, Sciences biologiques et medicales, Biological and medical sciences, Sciences biologiques fondamentales et appliquees. Psychologie, Fundamental and applied biological sciences. Psychology, Ecologie animale, vegetale et microbienne, Animal, plant and microbial ecology, Ecologie animale et végétale, Animal and plant ecology, Synécologie, Synecology, Généralités, General aspects, Algae, Heterokontophyta, Plancton, plankton, Action anthropique, human activity, Acción hombre, Activité humaine, Human activity, Actividad humana, Air, air, Bacillariophyta, Biosphère, biosphere, Biosfera, Bloom, Brome, bromine, Bromo, Changement climatique, climate change, Chlorophylle, chlorophyll, Clorofila, Climat, climate, Clima, Concentration, concentration, Concentración, Cycle biogéochimique, biogeochemical cycle, Durée, duration, Dynamique, dynamics, Dinámica, Eau mer, sea water, Agua mar, Ecosystème, ecosystems, Ecosistema, Facteur anthropique, Anthropogenic factor, Factor antrópico, Facteur biogène, Biogenic factor, Factor biógeno, Glace marine, sea ice, Hielo marino, Groupement végétal, Plant community, Comunidad vegetal, Milieu marin, marine environment, Medio marino, Phytoplancton, phytoplankton, Fitoplancton, Structure communauté, Community structure, Estructura comunidad, Variation annuelle, annual variations, Variación anual, Zone côtière, coastal zone, and Méthyle sulfure

[1] Climate change and human activities are expected to have a major impact on the structure and functioning of marine ecosystems and the biogeochemical cycles they mediate in the coming years. Here we describe time series measurements of biogenic bromocarbons (CHBr3 and CH2Br2) collected in coastal waters of the western Antarctic Peninsula which is one of the world's most rapidly changing marine environments. Our measurements spanned a period of changing sea-ice dynamics and phytoplankton community structure driven by climatic forcing. Specifically, the occurrence of high chlorophyll a concentrations (>5 μg L―1) and dominance of the largest phytoplankton size fraction (≥20 μm) indicating diatom bloom conditions was reduced following winter periods with a relatively short winter sea-ice duration (<50 days). While large inter-annual variability in seawater CHBr3 concentrations was observed alongside these changes the same was not found for CH2Br2 which is surprising given their proposed common source. Seawater CHBr3 concentrations were found to be significantly higher (122 [14.7-580] pmol L―1, P < 0.0001, Mann-Whitney) in samples collected in diatom bloom compared to non-bloom waters (42.9 [12.0-126] pmol L―1). A comparison of sea-to-air flux rates suggests that a switch from diatom bloom to non-bloom conditions results in a factor of 3―4 decrease in average CHBr3 sea-to-air emission rates which will reduce the supply of biogenic bromine to the atmosphere. Our calculations suggest that this will drive a decrease in inorganic bromine levels in the troposphere by a factor of 2-3 outside of ozone depletion events with potentially important implications for ozone cycling and dimethyl sulphide oxidation. This work has captured and crucially quantified the impact of a climate-induced change in a marine ecosystem on ocean-atmosphere biogeochemistry.

Astronomy earth cosmic environment, Astronomie et environnement cosmique terrestre, Geophysics, Géophysique, Climatology, meteorology, Climatologie, météorologie, Oceanography, Océanographie, Sciences exactes et technologie, Exact sciences and technology, Terre, ocean, espace, Earth, ocean, space, Sciences de la terre, Earth sciences, Amérique du Nord, North America, America del norte, Age, age, Edad, Appauvrissement, depletion, Brome, bromine, Bromo, Cendre, ash, Ceniza, Concentration, concentration, Concentración, Cratère, craters, Cráter, Destruction, destruction, Déplétion, Depletion, Depleción, Modèle, models, Modelo, Ozone, ozone, Ozono, Panache, plumes, Penacho, Troposphère, and troposphere

[1] We measured ozone (03) concentrations in the atmospheric plumes of the volcanoes St. Augustine (1976), Mt. Etna (2004, 2009) and Eyjafjallajökull (2010) and found 03 to be strongly depleted compared to the background at each volcano. At Mt. Etna 03 was depleted within tens of seconds from the crater, the age of the St. Augustine plumes was on the order of hours, whereas the O3 destruction in the plume of Eyjafjallajökull was maintained in 1-9 day old plumes. The most likely cause for this 03 destruction are catalytic bromine reactions as suggested by a model that manages to reproduce the very early destruction of O3 but also shows that 03 destruction is ongoing for several days. Given the observed rapid and sustained destruction of O3, heterogeneous loss of O3 on ash is unlikely to be important.

Astronomy earth cosmic environment, Astronomie et environnement cosmique terrestre, Geophysics, Géophysique, Climatology, meteorology, Climatologie, météorologie, Oceanography, Océanographie, Sciences exactes et technologie, Exact sciences and technology, Terre, ocean, espace, Earth, ocean, space, Sciences de la terre, Earth sciences, Air, air, Cap, capes, Cabo, Chimie atmosphérique, Atmospheric chemistry, Climat, climate, Clima, Eau mer, sea water, Agua mar, Gaz, gases, Gas, Incertitude, uncertainties, Io, Iode, iodine, Iodo, Matière volatile, volatiles, Materia volátil, Modèle atmosphère, Atmosphere model, Modelo atmósfera, Monde, global, Mundo, Phénomène précurseur, precursors, Fenómeno precursor, Précurseur, Precursor, Zone tropicale, tropical zone, and Zona tropical

[1] Oceanic emissions of gaseous organic iodine-atom precursors have the potential to significantly affect atmospheric chemistry and climate, however there is currently considerable uncertainty associated with quantifying their sources. We present sea-air fluxes calculated from simultaneous air and seawater measurements of a comprehensive range of volatile organic iodine compounds (VOICs), including CH3I and the less commonly reported dihalomethanes CH2ICl, CH2IBr and CH2I2, made during two cruises in the Atlantic Ocean between 15-58°N. The combined dihalomethane flux provides a global iodine source (∼0.33 ± 0.19 Tg I y-1 ) comparable to that of CH3I, and a surface iodine atom source 3-4 times higher. However, a 1 D atmospheric model reveals that, in the tropical east Atlantic Ocean in the vicinity of Cape Verde, even these combined VOIC fluxes are capable of supporting only ∼10-25% of the observed IO levels, and suggests that a substantial (340-640 nmol I m-2 d-1) additional photochemical source of iodine is required.