A global catalogue of large SO \u3c inf\u3e 2 sources and emissions derived from the Ozone Monitoring Instrument

Sulfur dioxide (SO2) measurements from the Ozone Monitoring Instrument (OMI) satellite sensor processed with the new principal component analysis (PCA) algorithm were used to detect large point emission sources or clusters of sources. The total of 491 continuously emitting point sources releasing from about 30 kt yr-1 to more than 4000 kt yr-1 of SO2 per year have been identified and grouped by country and by primary source origin: volcanoes (76 sources); power plants (297); smelters (53); and sources related to the oil and gas industry (65). The sources were identified using different methods, including through OMI measurements themselves applied to a new emission detection algorithm, and their evolution during the 2005-2014 period was traced by estimating annual emissions from each source. For volcanic sources, the study focused on continuous degassing, and emissions from explosive eruptions were excluded. Emissions from degassing volcanic sources were measured, many for the first time, and collectively they account for about 30 % of total SO2 emissions estimated from OMI measurements, but that fraction has increased in recent years given that cumulative global emissions from power plants and smelters are declining while emissions from oil and gas industry remained nearly constant. Anthropogenic emissions from the USA declined by 80 % over the 2005-2014 period as did emissions from western and central Europe, whereas emissions from India nearly doubled, and emissions from other large SO2-emitting regions (South Africa, Russia, Mexico, and the Middle East) remained fairly constant. In total, OMI-based estimates account for about a half of total reported anthropogenic SO2 emissions; the remaining half is likely related to sources emitting less than 30 kt yr-1 and not detected by OMI

Utilisations et applications pratiques du modèle d'aide à la gestion des eaux du lac de Guiers (modèle LGPLG) : alternatives de gestion actuelle et future

Le lac de Guiers est amené à jouer un rôle important dans les années à venir, rôle de réservoir destiné à garantir l'approvisionnement des cultures irriguées sur son pourtour et de l'usine des eaux de N'Gnith et passage obligé des eaux du fleuve vers le canal de Cayor, projet essentiel pour la survie du Sénégal. Les critères hydrologiques constitueront la base de la gestion future du lac; d'autres éléments de décision, économiques, écologiques et sanitaires devront aussi être pris en considération. La gestion pratique du lac se révèlera complexe et l'outil informatique indispensable. Un modèle de gestion des eaux (LGPLG) a été mis au point en 1991 dans le cadre du projet EQUESEN. Le but de cette étude est de présenter les différentes composantes du modèle et d'en décrire l'utilisation par le biais d'exemples pratiques d'application destinés à familiariser l'opérateur à l'outil de gestion. Ces exemples se réfèrent à des situations hydrologiques fictives pour la plupart; les disponibilités futures en eau fluviale tout comme les besoins des divers utilisateurs à l'horizon 2000-2025 sont encore très imprécis aujourd'hui. Néanmoins les bases de la gestion future probable du Guiers sont pris en compte. Ce travail n'optimalise pas les critères de la politique de gestion du lac de Guiers mais doit être perçu comme un manuel d'application. (Résumé d'auteur

Fonctionnement et bilan hydrologique du lac de Guiers en 1991

Le bilan hydrique du Lac de Guiers est établi pour l'année 1991. Les composantes essentielles sont d'ordre purement physique : les apports en eau sont tributaires de la crue fluviale (87,3 %). Les composantes secondaires sont de nature anthropique et liées à l'action de l'homme soit pour les apports aux rejets de la CSS (6,3 %), soit au chapitre des pertes par les prélèvements de la CSS (3,8 %), de la SONEES (2,2 %) ou encore de la SAED (1,4 %). (Résumé d'auteur

First observations of volcanic eruption clouds from the L1 Earth-Sun Lagrange point by DSCOVR/EPIC

Volcanic sulfur dioxide (SO2) emissions have been measured by ultraviolet sensors on polar‐orbiting satellites for several decades but with limited temporal resolution. This precludes studies of key processes believed to occur in young (~1–3 hr old) volcanic clouds. In 2015, the launch of the Earth Polychromatic Imaging Camera (EPIC) aboard the Deep Space Climate Observatory (DSCOVR) provided an opportunity for novel observations of volcanic eruption clouds from the first Earth‐Sun Lagrange point (L1). The L1 vantage point provides continuous observations of the sunlit Earth, offering up to eight or nine observations of volcanic SO2 clouds in the DSCOVR/EPIC field of view at ~1‐hr intervals. Here we demonstrate DSCOVR/EPIC\u27s sensitivity to volcanic SO2 using several volcanic eruptions from the tropics to midlatitudes. The hourly cadence of DSCOVR/EPIC observations permits more timely measurements of volcanic SO2 emissions, improved trajectory modeling, and novel analyses of the temporal evolution of volcanic clouds

In situ measurements of tropospheric volcanic plumes in Ecuador and Colombia during TC

A NASA DC‐8 research aircraft penetrated tropospheric gas and aerosol plumes sourced from active volcanoes in Ecuador and Colombia during the Tropical Composition, Cloud and Climate Coupling (TC4 ) mission in July–August 2007. The likely source volcanoes were Tungurahua (Ecuador) and Nevado del Huila (Colombia). The TC4 data provide rare insight into the chemistry of volcanic plumes in the tropical troposphere and permit a comparison of SO2 column amounts measured by the Ozone Monitoring Instrument (OMI) on the Aura satellite with in situ SO2 measurements. Elevated concentrations of SO2, sulfate aerosol, and particles were measured by DC‐8 instrumentation in volcanic outflow at altitudes of 3–6 km. Estimated plume ages range from ∼2 h at Huila to ∼22–48 h downwind of Ecuador. The plumes contained sulfate‐rich accumulation mode particles that were variably neutralized and often highly acidic. A significant fraction of supermicron volcanic ash was evident in one plume. In‐plume O3 concentrations were ∼70%–80% of ambient levels downwind of Ecuador, but data are insufficient to ascribe this to O3 depletion via reactive halogen chemistry. The TC4 data record rapid cloud processing of the Huila volcanic plume involving aqueous‐phase oxidation of SO2 by H2O2, but overall the data suggest average in‐plume SO2 to sulfate conversion rates of ∼1%–2% h−1 . SO2 column amounts measured in the Tungurahua plume (∼0.1–0.2 Dobson units) are commensurate with average SO2 columns retrieved from OMI measurements in the volcanic outflow region in July 2007. The TC4 data set provides further evidence of the impact of volcanic emissions on tropospheric acidity and oxidizing capacit

Modeling of 2008 Kasatochi volcanic sulfate direct radiative forcing: Assimilation of OMI SO \u3c inf\u3e 2 plume height data and comparison with MODIS and CALIOP observations

Volcanic SO2 column amount and injection height retrieved from the Ozone Monitoring Instrument (OMI) with the Extended Iterative Spectral Fitting (EISF) technique are used to initialize a global chemistry transport model (GEOS-Chem) to simulate the atmospheric transport and lifecycle of volcanic SO2 and sulfate aerosol from the 2008 Kasatochi eruption, and to subsequently estimate the direct shortwave, top-of-the-atmosphere radiative forcing of the volcanic sulfate aerosol. Analysis shows that the integrated use of OMI SO2 plume height in GEOS-Chem yields: (a) good agreement of the temporal evolution of 3-D volcanic sulfate distributions between model simulations and satellite observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) and Cloud-Aerosol Lidar with Orthogonal Polarisation (CALIOP), and (b) an e-folding time for volcanic SO 2 that is consistent with OMI measurements, reflecting SO2 oxidation in the upper troposphere and stratosphere is reliably represented in the model. However, a consistent (∼25%) low bias is found in the GEOS-Chem simulated SO2 burden, and is likely due to a high (∼20%) bias of cloud liquid water amount (as compared to the MODIS cloud product) and the resultant stronger SO2 oxidation in the GEOS meteorological data during the first week after eruption when part of SO2 underwent aqueous-phase oxidation in clouds. Radiative transfer calculations show that the forcing by Kasatochi volcanic sulfate aerosol becomes negligible 6 months after the eruption, but its global average over the first month is -1.3 Wm -2, with the majority of the forcing-influenced region located north of 20 N, and with daily peak values up to -2 Wm-2 on days 16-17. Sensitivity experiments show that every 2 km decrease of SO2 injection height in the GEOS-Chem simulations will result in a ∼25 % decrease in volcanic sulfate forcing; similar sensitivity but opposite sign also holds for a 0.03 μm increase of geometric radius of the volcanic aerosol particles. Both sensitivities highlight the need to characterize the SO 2 plume height and aerosol particle size from space. While more research efforts are warranted, this study is among the first to assimilate both satellite-based SO2 plume height and amount into a chemical transport model for an improved simulation of volcanic SO2 and sulfate transport

In situ measurements of tropospheric volcanic plumes in Ecuador and Colombia during TC^4

A NASA DC-8 research aircraft penetrated tropospheric gas and aerosol plumes sourced from active volcanoes in Ecuador and Colombia during the Tropical Composition, Cloud and Climate Coupling (TC^4) mission in July–August 2007. The likely source volcanoes were Tungurahua (Ecuador) and Nevado del Huila (Colombia). The TC^4 data provide rare insight into the chemistry of volcanic plumes in the tropical troposphere and permit a comparison of SO_2 column amounts measured by the Ozone Monitoring Instrument (OMI) on the Aura satellite with in situ SO_2 measurements. Elevated concentrations of SO_2, sulfate aerosol, and particles were measured by DC-8 instrumentation in volcanic outflow at altitudes of 3–6 km. Estimated plume ages range from ~2 h at Huila to ~22–48 h downwind of Ecuador. The plumes contained sulfate-rich accumulation mode particles that were variably neutralized and often highly acidic. A significant fraction of supermicron volcanic ash was evident in one plume. In-plume O_3 concentrations were ~70%–80% of ambient levels downwind of Ecuador, but data are insufficient to ascribe this to O_3 depletion via reactive halogen chemistry. The TC^4 data record rapid cloud processing of the Huila volcanic plume involving aqueous-phase oxidation of SO_2 by H_2O_2, but overall the data suggest average in-plume SO_2 to sulfate conversion rates of ~1%–2% h^(−1). SO_2 column amounts measured in the Tungurahua plume (~0.1–0.2 Dobson units) are commensurate with average SO_2 columns retrieved from OMI measurements in the volcanic outflow region in July 2007. The TC^4 data set provides further evidence of the impact of volcanic emissions on tropospheric acidity and oxidizing capacity

Modeling of 2008 Kasatochi Volcanic Sulfate Direct Radiative Forcing: Assimilation of OMI SO2 Plume Height Data and Comparison with MODIS and CALIOP Observations

Volcanic SO2 column amount and injection height retrieved from the Ozone Monitoring Instrument (OMI) with the Extended Iterative Spectral Fitting (EISF) technique are used to initialize a global chemistry transport model (GEOS-Chem) to simulate the atmospheric transport and lifecycle of volcanic SO2 and sulfate aerosol from the 2008 Kasatochi eruption, and to subsequently estimate the direct shortwave, top-of-the-atmosphere radiative forcing of the volcanic sulfate aerosol. Analysis shows that the integrated use of OMI SO2 plume height in GEOS-Chem yields: (a) good agreement of the temporal evolution of 3-D volcanic sulfate distributions between model simulations and satellite observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) and Cloud-Aerosol Lidar with Orthogonal Polarisation (CALIOP), and (b) an e-folding time for volcanic SO2 that is consistent with OMI measurements, reflecting SO2 oxidation in the upper troposphere and stratosphere is reliably represented in the model. However, a consistent (approx. 25 %) low bias is found in the GEOS-Chem simulated SO2 burden, and is likely due to a high (approx.20 %) bias of cloud liquid water amount (as compared to the MODIS cloud product) and the resultant stronger SO2 oxidation in the GEOS meteorological data during the first week after eruption when part of SO2 underwent aqueous-phase oxidation in clouds. Radiative transfer calculations show that the forcing by Kasatochi volcanic sulfate aerosol becomes negligible 6 months after the eruption, but its global average over the first month is -1.3W/sq m, with the majority of the forcing-influenced region located north of 20degN, and with daily peak values up to -2W/sq m on days 16-17. Sensitivity experiments show that every 2 km decrease of SO2 injection height in the GEOS-Chem simulations will result in a approx.25% decrease in volcanic sulfate forcing; similar sensitivity but opposite sign also holds for a 0.03 m increase of geometric radius of the volcanic aerosol particles. Both sensitivities highlight the need to characterize the SO2 plume height and aerosol particle size from space. While more research efforts are warranted, this study is among the first to assimilate both satellite-based SO2 plume height and amount into a chemical transport model for an improved simulation of volcanic SO2 and sulfate transport