Meteorological influence on the seasonal and diurnal variability of the dispersion of volcanic emissions in Nicaragua: a numerical model

Nicaragua comprises seven historically active volcanoes (Cosigüina, San Cristobal, Telica, Cerro Negro, Momotombo, Masaya, and Concepcion), five of which are in a state of continuous degassing. Published measurements of the atmospheric dispersion of continuous emissions from Nicaraguan volcanoes, the chemical and aerosol microphysical modifications of the released gases and aerosols, and related acid deposition and impacts on the environment cover only short periods of time. We applied a three-dimensional atmosphere-chemistry/aerosol numerical model over Central America focussing on Nicaraguan volcanic emissions for month long simulation periods during the dry and wet seasons of 2003. The model is able to reproduce observed monthly precipitation and wind speed throughout the year 2003. Model results for near surface SO2 concentrations and SO2 dry deposition fluxes around Masaya volcano are in very good agreement with field measurements. During the dry season, oxidation of SO2 to sulphate plays only a minor role downwind of the Nicaraguan volcanoes and over the Pacific Ocean, whereas SO2 released from Arenal and Poas in Costa Rica is oxidised to sulphate much faster and closer to the volcanoes due to higher humidity and cloud water availability. During the wet season, more variable wind conditions lead to reduced dispersion of SO2 over the Pacific Ocean and increased dispersion inland. The availability of liquid water in the atmosphere favours sulphate formation close to the Nicaraguan volcanoes via aqueous phase oxidation and represents another limitation for the dispersion of SO2. Strong precipitation removes sulphate quickly from the atmosphere by wet deposition. Atmospheric SO2 concentrations and in particular dry deposition close to the volcanoes show a pronounced diurnal cycle

Aerosol Distribution over Europe: a Model Evaluation Study with Detailed Aerosol Microphysics

This paper summarizes an evaluation of model simulations with a regional scale atmospheric climate-chemistry/ aerosol model called REMOTE, which has been extended by a microphysical aerosol module. Model results over Europe are presented and compared with available measurements in surface air focusing on the European distribution and variability of primary and secondary aerosols. Additionally, model results obtained with detailed aerosol microphysics are compared to those based on an aerosol bulk mass approach revealing the impact of dry deposition fluxes on atmospheric burden concentration. An improved determination of elevated ozone and sulfate concentrations could be achieved by considering a diurnal cycle in the anthropogenic emission fluxes. Deviation between modelled and measured organic carbon concentrations can be mainly explained by missing formation of secondary organic aerosols and deficiencies in emission data. Changing residential heating practices in Europe, where the use of wood is no longer restricted to rural areas, need to be considered in emission inventories as well as vegetation fire emissions which present a dominant source of organic carbon.JRC.DDG.H.2-Climate chang

A comparison of satellite- and ground-based measurements of SO2emissions from Tungurahua volcano, Ecuador

Satellite-measured SO2 mass loadings and ground-based measurements of SO2 emission rate are not directly comparable, with ∼40% differences between mean emissions reported by each technique from Tungurahua volcano, Ecuador, during late 2007. Numerical simulations of postemission processing and dispersal of Tungurahua's SO2 emissions enable more effective comparison of ground- and satellite-based SO2 data sets, reducing the difference between them and constraining the impact of plume processing on satellite SO2 observations. Ground-based measurements of SO2 emission rate are used as the model input, and simulated SO2 mass loadings are compared to those measured by the Ozone Monitoring Instrument (OMI). The changing extent of SO2 processing has a significant impact on daily variation in SO2 mass loading for a fixed volcanic emission rate. However, variations in emission rate at Tungurahua are large, suggesting that overall volcanic source strength and not subsequent processing is more likely to be the dominant control on atmospheric mass loading. SO2 emission rate estimates are derived directly from the OMI observations using modeled SO2 lifetime. Good agreement is achieved between both observed and simulated mass loadings (∼21%) and satellite-derived and ground-measured SO2 emission rates (∼18%), with a factor of 2 improvement over the differences found by simple direct comparison. While the balance of emission source strength and postemission processing will differ between volcanoes and regions, under good observation conditions and where SO2 lifetime is ∼24 hours, satellite-based sensors like OMI may provide daily observations of SO2 mass loading which are a good proxy for volcanic source strength

Contribution of isoprene oxidation products to marine aerosol over the north-east atlantic

Secondary organic aerosol (SOA) formation through isoprene oxidation was investigated with the regional-scale climate model REMOTE. The applied modeling scheme includes a treatment for marine primary organic aerosol emissions, aerosol microphysics, and SOA formation through the gas/particle partitioning of semivolatile, water-soluble oxidation products. The focus was on SOA formation taking place over the North-East Atlantic during a period of high biological activity. Isoprene SOA concentrations were up to similar to 5ng m(-3) over North Atlantic in the base case model runs, and isoprene oxidation made a negligible contribution to the marine organic aerosol (OA) mass. In particular, isoprene SOA did not account for the observed water-soluble organic carbon (WSOC) concentrations over North Atlantic. The performed model calculations, together with results from recent field measurements, imply a missing source of SOA over remote marine areas unless the isoprene oxidation products are considerably less volatile than the current knowledge indicates

Contribution of isoprene oxidation products to marine aerosol over the north-east atlantic

Secondary organic aerosol (SOA) formation through isoprene oxidation was investigated with the regional-scale climate model REMOTE. The applied modeling scheme includes a treatment for marine primary organic aerosol emissions, aerosol microphysics, and SOA formation through the gas/particle partitioning of semivolatile, water-soluble oxidation products. The focus was on SOA formation taking place over the North-East Atlantic during a period of high biological activity. Isoprene SOA concentrations were up to similar to 5ng m(-3) over North Atlantic in the base case model runs, and isoprene oxidation made a negligible contribution to the marine organic aerosol (OA) mass. In particular, isoprene SOA did not account for the observed water-soluble organic carbon (WSOC) concentrations over North Atlantic. The performed model calculations, together with results from recent field measurements, imply a missing source of SOA over remote marine areas unless the isoprene oxidation products are considerably less volatile than the current knowledge indicates

A combined organic-inorganic sea-spray source function

This study presents a novel approach to develop a combined organic-inorganic sub-micron sea-spray source function for inclusion in large-scale models. It requires wind speed and surface ocean chlorophyll-a concentration as input parameters. The combined organic-inorganic source function is implemented in the REMOTE regional climate model and sea-spray fields are predicted with particular focus on the North East Atlantic. The model predictions using the new source functions compare well with observations of total sea-spray mass and organic carbon fraction in sea-spray aerosol. During winter (periods of low oceanic biological activity), sea-salt dominates the sea-spray mass while in summer (when biological activity is high), water soluble organic carbon contributes between 60-90% of the submicron sea-spray mass

A combined organic-inorganic sea-spray source function

This study presents a novel approach to develop a combined organic-inorganic sub-micron sea-spray source function for inclusion in large-scale models. It requires wind speed and surface ocean chlorophyll-a concentration as input parameters. The combined organic-inorganic source function is implemented in the REMOTE regional climate model and sea-spray fields are predicted with particular focus on the North East Atlantic. The model predictions using the new source functions compare well with observations of total sea-spray mass and organic carbon fraction in sea-spray aerosol. During winter (periods of low oceanic biological activity), sea-salt dominates the sea-spray mass while in summer (when biological activity is high), water soluble organic carbon contributes between 60-90% of the submicron sea-spray mass