Model simulations of the changing distribution of Ozone and its radiative forcing of climate: past, present and future

A background tropospheric chemistry model that is coupled to the general circulation model ECHAM4 is used to calculate tropospheric ozone with preindustrial, present-day and future (IS92a) emission scenarios as boundary conditions. The model calculates separate contributions to tropospheric ozone levels from stratosphere-troposphere exchange (STE) and from photo- chemical production in the troposphere. In the preindustrial atmosphere, the simulated annual tropospheric ozone content is 190 Tg 03, of which about 110 Tg 03 originates from the strato- sphere. In the present-day simulation the ozone content is about 80 Tg 03 larger, mainly due to O3 precursor emissions from industrial processes in the NH and from biomass burning in trop- ical regions. In the next few decades, industrial growth is expected to occur mainly at NH (sub) tropical latitudes, leading to an additional increase of the tropospheric ozone budget by 60 Tg 03. We calculate a global and annual average radiative forcing by tropospheric ozone perturbations of 0.42 w m-2 creases in the next few decades of 0.31 W m-2 for the present-day simulation, and an additional forcing due to ozone in- The model results indicate that the amount of tropospheric ozone from stratospheric origin remains relatively unaffected by the changing pho- tochemistry

Reformulating atmospheric aerosol thermodynamics and hygroscopic growth into fog, haze and clouds

International audienceModeling atmospheric aerosol and cloud microphysics is rather complex, even if chemical and thermodynamical equilibrium is assumed. We show, however, that the thermodynamics can be considerably simplified by reformulating equilibrium to consistently include water, and transform laboratory-based concepts to atmospheric conditions. We generalize the thermodynamic principles that explain hydration and osmosis ? merely based on solute solubilities ? to explicitly account for the water mass consumed by hydration. As a result, in chemical and thermodynamical equilibrium the relative humidity (RH) suffices to determine the saturation molality, including solute and solvent activities (and activity coefficients), since the water content is fixed by RH for a given aerosol concentration and type. As a consequence, gas/liquid/solid aerosol equilibrium partitioning can be solved analytically and non-iteratively. Our new concept enables an efficient and accurate calculation of the aerosol water mass and directly links the aerosol hygroscopic growth to fog, haze and cloud formation. We apply our new concept in the 3rd Equilibrium Simplified Aerosol Model (EQSAM3) for use in regional and global chemistry-transport and climate models. Its input is limited to the species' solubilities from which a newly introduced stoichiometric coefficient for water is derived. Analogously, we introduce effective stoichiometric coefficients for the solutes to account for complete or incomplete dissociation. We show that these coefficients can be assumed constant over the entire activity range and calculated for various inorganic, organic and non-electrolyte compounds, including alcohols, sugars and dissolved gases. EQSAM3 calculates the aerosol composition and gas/liquid/solid partitioning of mixed inorganic/organic multicomponent solutions and the associated water uptake for almost 100 major compounds. It explicitly accounts for particle hygroscopic growth by computing aerosol properties such as single solute molalities, molal based activities, including activity coefficients for volatile compounds, efflorescence and deliquescence relative humidities of single solute and mixed solutions. Various applications and a model inter-comparison indicate that a) the application is not limited to dilute binary solutions, b) sensitive aerosol properties such as hygroscopic growth and the pH of binary and mixed inorganic/organic salt solutions up to saturation can be computed accurately, and c) aerosol water is central in modeling atmospheric chemistry, visibility, weather and climate

Large-Scale Modelling of the Environmentally-Driven Population Dynamics of Temperate Aedes albopictus (Skuse)

The Asian tiger mosquito, Aedes albopictus, is a highly invasive vector species. It is a proven vector of dengue and chikungunya viruses, with the potential to host a further 24 arboviruses. It has recently expanded its geographical range, threatening many countries in the Middle East, Mediterranean, Europe and North America. Here, we investigate the theoretical limitations of its range expansion by developing an environmentally-driven mathematical model of its population dynamics. We focus on the temperate strain of Ae. albopictus and compile a comprehensive literature-based database of physiological parameters. As a novel approach, we link its population dynamics to globally-available environmental datasets by performing inference on all parameters. We adopt a Bayesian approach using experimental data as prior knowledge and the surveillance dataset of Emilia-Romagna, Italy, as evidence. The model accounts for temperature, precipitation, human population density and photoperiod as the main environmental drivers, and, in addition, incorporates the mechanism of diapause and a simple breeding site model. The model demonstrates high predictive skill over the reference region and beyond, confirming most of the current reports of vector presence in Europe. One of the main hypotheses derived from the model is the survival of Ae. albopictus populations through harsh winter conditions. The model, constrained by the environmental datasets, requires that either diapausing eggs or adult vectors have increased cold resistance. The model also suggests that temperature and photoperiod control diapause initiation and termination differentially. We demonstrate that it is possible to account for unobserved properties and constraints, such as differences between laboratory and field conditions, to derive reliable inferences on the environmental dependence of Ae. albopictus populations

Diurnal ozone cycle in the tropical and subtropical marine boundary layer

A conceptual analysis of diurnal ozone (O3 ) changes in the marine boundary layer (MBL) is presented. Such changes are most pronounced downwind of O3 sources in tropical and subtropical latitudes, and during summer at higher latitudes. Previously, it has been assumed that daytime photochemical O3 loss, and nighttime replenishment through entrainment from the relatively O3 -rich free troposphere, explains the diurnal O3 cycle. We show, however, that in a net O3 -destruction environment (low NOx ) this diurnal cycle can be explained by photochemistry and advection, which establish a horizontal O3 gradient that is typical for the MBL. We support this hypothesis firstly by calculations with a conceptual 1-D advection-diffusion model, and secondly by simulations with an interactive 3-D chemistry-transport model. The results are in good agreement with observations, for example, in the Indian Ocean Experiment (INDOEX)

Modeled global effects of airborne desert dust on air quality and premature mortality

Fine particulate matter is one of the most important factors contributing to air pollution. Epidemiological studies have related increased levels of atmospheric particulate matter to premature human mortality caused by cardiopulmonary disease and lung cancer. However, a limited number of investigations have focused on the contribution of airborne desert dust particles. Here we assess the effects of dust particles with an aerodynamic diameter smaller than 2.5 μm (DU_2.5) on human mortality for the year 2005. We used the EMAC atmospheric–chemistry general circulation model at high resolution to simulate global atmospheric dust concentrations. We applied a health impact function to estimate premature mortality for the global population of 30 yr and older, using parameters from epidemiological studies. We estimate a global cardiopulmonary mortality of about 402 000 in 2005. The associated years of life lost are about 3.47 million per year. We estimate the global fraction of the cardiopulmonary deaths caused by atmospheric desert dust to be about 1.8%, though in the 20 countries most affected by dust this is much higher, about 15–50%. These countries are primarily found in the so-called "dust belt" from North Africa across the Middle East and South Asia to East Asi

Global risk from the atmospheric dispersion of radionuclides by nuclear power plant accidents in the coming decades

We estimate the global risk from the release and atmospheric dispersion of radionuclides from nuclear power plant accidents using the EMAC atmospheric chemistry–general circulation model. We included all nuclear reactors that are currently operational, under construction and planned or proposed. We implemented constant continuous emissions from each location in the model and simulated atmospheric transport and removal via dry and wet deposition processes over 20 years (2010–2030), driven by boundary conditions based on the IPCC A2 future emissions scenario. We present global overall and seasonal risk maps for potential surface layer concentrations and ground deposition of radionuclides, and estimate potential doses to humans from inhalation and ground-deposition exposures to radionuclides. We find that the risk of harmful doses due to inhalation is typically highest in the Northern Hemisphere during boreal winter, due to relatively shallow boundary layer development and limited mixing. Based on the continued operation of the current nuclear power plants, we calculate that the risk of radioactive contamination to the citizens of the USA will remain to be highest worldwide, followed by India and France. By including stations under construction and those that are planned and proposed, our results suggest that the risk will become highest in China, followed by India and the USA

Technical Note: The Modular Earth Submodel System (MESSy) ? a new approach towards Earth System Modeling

International audienceGenerally, the typical approach towards Earth System Modeling has been to couple existing models of different domains (land, ocean, atmosphere, ...) offline, using output files of one model to provide input for the other. However, for a detailed study of the interactions and feedbacks between chemical, physical, and biological processes, it is necessary to perform the coupling online. One strategy is to link the existing domain-specific models with a universal coupler. In many cases, however, a much simpler approach is more feasible. To achieve the online coupling, we have developed the Modular Earth Submodel System (MESSy). Data are exchanged between a and several within one comprehensive model system. MESSy includes a generalized interface structure for the standardized control of the and their interconnections. The internal complexity of the is controllable in a transparent and user friendly way. This provides remarkable new possibilities to study feedback mechanisms (by two-way coupling), e.g., by applying MESSy to a general circulation model (GCM)

Lightning and convection parameterisations ? uncertainties in global modelling

International audienceThe simulation of convection, lightning and consequent NOx emissions with global atmospheric chemistry models is associated with large uncertainties since these processes are heavily parameterised. Each parameterisation by itself has deficiencies and the combination of these substantially increases the uncertainties compared to the individual parameterisations. In this study several combinations of state-of-the-art convection and lightning parameterisations are used in simulations with the global atmospheric chemistry general circulation model ECHAM5/MESSy, and are evaluated against lightning observations. A wide range in the spatial and temporal variability of the simulated flash densities is found, attributed to both types of parameterisations. Some combinations perform well, whereas others are hardly applicable. In addition to resolution dependent rescaling parameters, each combination of lightning and convection schemes requires individual scaling to reproduce the observed flash frequencies. The resulting NOx profiles are inter-compared, however definite conclusions about the most realistic profiles can currently not be drawn

A 1° x 1° resolution data set of historical anthropogenic trace gas emissions for the period 1890-1990

An anthropogenic emissions data set has been constructed for CO2, CO, CH4, nonmethane volatile organic compounds, SO2, NOx, N2O, and NH3 spanning the period 1890–1990. The inventory is based on version 2.0 of the Emission Database for Global Atmospheric Research (EDGAR 2.0). In EDGAR the emissions are calculated per country and economic sector using an emission factor approach. Calculations of the emissions with 10 year intervals are based on historical activity statistics and selected emission factors. Historical activity data were derived from the Hundred Year Database for Integrated Environmental Assessments (1890–1990) supplemented with other data and our own estimates. Emission factors account for changes in economical and technological developments in the past. The calculated emissions on a country basis have been interpolated onto a 1°x1° grid. This consistent data set can be used in trend studies of tropospheric trace gases and in environmental assessments, for example, the analysis of historical contributions of regions and countries to environmental forcing like the enhanced greenhouse gas effect, acidification, and eutrofication. The database focuses on energy/industrial and agricultural/waste sources; for completeness, historical biomass-burning estimates where added using a simple and transparent approach. ? 2001 American Geophysical Unio

Data-driven aeolian dust emission scheme for climate modelling evaluated with EMAC 2.55.2

Aeolian dust has significant impacts on climate, public health, infrastructure and ecosystems. Assessing dust concentrations and the impacts is challenging because the emissions depend on many environmental factors and can vary greatly with meteorological conditions. We present a data-driven aeolian dust scheme that combines machine learning components and physical equations to predict atmospheric dust concentrations and quantify the sources. The numerical scheme was trained to reproduce dust aerosol optical depth retrievals by the Infrared Atmospheric Sounding Interferometer on board the MetOp-A satellite. The input parameters included meteorological variables from the fifth-generation atmospheric reanalysis of the European Centre for Medium-Range Weather Forecasts. The trained dust scheme can be applied as an emission submodel to be used in climate and Earth system models, which is reproducibly derived from observational data so that a priori assumptions and manual parameter tuning can be largely avoided. We compared the trained emission submodel to a state-of-the-art emission parameterisation, showing that it substantially improves the representation of aeolian dust in the global atmospheric chemistry–climate model EMAC.</p