| publications-1401 |
PEER REVIEWED ARTICLE |
2016 |
Toohey, M., Stevens, B., Schmidt, H., and Timmreck, C.: |
Easy Volcanic Aerosol (EVA v1.0): An idealized forcing generator for climate simulations |
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10.5194/gmd-9-4049-2016 |
Data Management & Analytics |
Groundwater |
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Abstract. Stratospheric sulfate aerosols from volcanic eruptions have a significant impact on the Earth's climate. To include the effects of volcanic eruptions in climate model simulations, the Easy Volcanic Aerosol (EVA) forcing generator provides stratospheric aerosol optical properties as a function of time, latitude, height, and wavelength for a given input list of volcanic eruption attributes. EVA is based on a parameterized three-box model of stratospheric transport and simple scaling relationships used to derive mid-visible (550 nm) aerosol optical depth and aerosol effective radius from stratospheric sulfate mass. Precalculated look-up tables computed from Mie theory are used to produce wavelength-dependent aerosol extinction, single scattering albedo, and scattering asymmetry factor values. The structural form of EVA and the tuning of its parameters are chosen to produce best agreement with the satellite-based reconstruction of stratospheric aerosol properties following the 1991 Pinatubo eruption, and with prior millennial-timescale forcing reconstructions, including the 1815 eruption of Tambora. EVA can be used to produce volcanic forcing for climate models which is based on recent observations and physical understanding but internally self-consistent over any timescale of choice. In addition, EVA is constructed so as to allow for easy modification of different aspects of aerosol properties, in order to be used in model experiments to help advance understanding of what aspects of the volcanic aerosol are important for the climate system. |
603557 |
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| publications-1402 |
PEER REVIEWED ARTICLE |
2019 |
Kain Glensor , Neil R.P. Harris |
Marginal Benefit to South Asian Economies from SO2 Emissions Mitigation and Subsequent Increase in Monsoon Rainfall |
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10.3390/atmos10020070 |
Data Management & Analytics |
Groundwater |
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Sulphate aerosols are dominated by SO2 emissions from coal-burning for the Indian electricity sector and they are thought to have a short term but significant, negative impact on South Asian Summer Monsoon rainfall. This reduction in precipitation in turn can lead to reduced economic outputs, primarily through smaller agricultural yields. By bringing together estimates of (a) the impact of sulphate aerosols on precipitation and (b) the observed relationship between monsoon rainfall and GDP, we present a methodology to estimate the possible financial cost of this effect on the Indian economy and on its agricultural sector. Our preliminary estimate is that the derived benefits could be large enough that around 50% of India’s SO2 emissions could be economically mitigated at no cost or net benefit, although it should be noted that the large uncertainties in the underlying relationships mean that the overall uncertainty is also large. Comparison of the 1952–1981 and 1982–2011 periods indicates that the Indian economy may now be more resilient to variability of the monsoon rainfall. As such, a case could be made for action to reduce SO2 emissions, particularly in the crucial monsoon period. This would have a significant, positive effect on a crucial and large sector in India’s economy and the effects would be visible almost instantly. The recent growth in renewable energy sources in India and the consequent, reduced increase in coal burning means that further financial costs have already been avoided. This impact should be further investigated so that it can be included in cost-benefit analyses of different fuel types in the region. The significant uncertainties associated with these calculations are discussed. |
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| publications-1403 |
PEER REVIEWED ARTICLE |
2014 |
M. Rex , I. Wohltmann , T. Ridder , R. Lehmann , K. Rosenlof , P. Wennberg , D. Weisenstein , J. Notholt , K. Krüger , V. Mohr , S. Tegtmeier |
A~tropical West Pacific OH minimum and implications for stratospheric composition |
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10.5194/acp-14-4827-2014 |
Data Management & Analytics |
Precipitation & Ecological Systems |
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Abstract. Most of the short-lived biogenic and anthropogenic chemical species that are emitted into the atmosphere break down efficiently by reaction with OH and do not reach the stratosphere. Here we show the existence of a pronounced minimum in the tropospheric column of ozone over the West Pacific, the main source region for stratospheric air, and suggest a corresponding minimum of the tropospheric column of OH. This has the potential to amplify the impact of surface emissions on the stratospheric composition compared to the impact when assuming globally uniform OH conditions. Specifically, the role of emissions of biogenic halogenated species for the stratospheric halogen budget and the role of increasing emissions of SO2 in Southeast Asia or from minor volcanic eruptions for the increasing stratospheric aerosol loading need to be reassessed in light of these findings. This is also important since climate change will further modify OH abundances and emissions of halogenated species. Our study is based on ozone sonde measurements carried out during the TransBrom cruise with the RV Sonne roughly along 140–150° E in October 2009 and corroborating ozone and OH measurements from satellites, aircraft campaigns and FTIR instruments. Model calculations with the GEOS-Chem Chemistry and Transport Model (CTM) and the ATLAS CTM are used to simulate the tropospheric OH distribution over the West Pacific and the transport pathways to the stratosphere. The potential effect of the OH minimum on species transported into the stratosphere is shown via modeling the transport and chemistry of CH2Br2 and SO2. |
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| publications-1404 |
PEER REVIEWED ARTICLE |
2014 |
Dubuisson, P., H. Herbin, F. Minvielle, M. Compiègne, F. Thieuleux, F. Parol, and J. Pelon |
Remote sensing of volcanic ash plumes from thermal infrared: case study analysis from SEVIRI, MODIS and IASI instruments |
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10.5194/amt-7-359-2014 |
Data Management & Analytics |
Precipitation & Ecological Systems |
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Abstract. The Eyjafjallajökull eruption, which occurred during May 2010, is used as a case study to evaluate the consistency of the detection and characterization of volcanic ash plumes from different thermal infrared instruments. In this study, the well-known split window technique is used to retrieve the optical thickness and the effective particle size, and to estimate the mass concentration of volcanic particles from brightness temperatures measured in the infrared atmospheric window (8–12 μm). Retrievals are obtained for several mineral compositions whose optical properties are computed using Mie theory accounting for spectral variations of the refractive index. The impacts of errors in atmospheric parameters on the a posteriori uncertainties have been analysed. This analysis confirmed that major sources of errors are the layer altitude, the particle composition and, most of all, the size distribution for which uncertainties in retrievals can reach 50% in mass loading estimates. This retrieval algorithm is then applied to measurements acquired near-simultaneously from MODIS, SEVIRI and IASI space-borne instruments, using two channels around 11 μm and 12 μm. The retrievals are in close agreement when taking into account the different spatial and spectral configurations, and deviations between retrievals remain less than the uncertainties due to errors in atmospheric parameters. This analysis demonstrates the robustness of the retrieval method and the consistency of observations from these instruments for volcanic ash plume monitoring. |
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| publications-1405 |
PEER REVIEWED ARTICLE |
2015 |
Boichu, M., Clarisse, L., Péré, J.-C., Herbin, H., Goloub, P., Thieuleux, F., Ducos, F., Clerbaux, C., and Tanré, D |
Temporal variations of flux and altitude of sulfur dioxide emissions during volcanic eruptions: implications for long-range dispersal of volcanic clouds |
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10.5194/acp-15-8381-2015 |
Uncategorized |
Uncategorized |
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Abstract. Sulfur-rich degassing, which is mostly composed of sulfur dioxide (SO2), plays a major role in the overall impact of volcanism on the atmosphere and climate. The accurate assessment of this impact is currently hampered by the poor knowledge of volcanic SO2 emissions. Here, using an inversion procedure, we show how assimilating snapshots of the volcanic SO2 load derived from the Infrared Atmospheric Sounding Interferometer (IASI) allows for reconstructing both the flux and altitude of the SO2 emissions with an hourly resolution. For this purpose, the regional chemistry-transport model CHIMERE is used to describe the dispersion of SO2 when released in the atmosphere. As proof of concept, we study the 10 April 2011 eruption of the Etna volcano (Italy), which represents one of the few volcanoes instrumented on the ground for the continuous monitoring of SO2 degassing. We find that the SO2 flux time-series retrieved from satellite imagery using the inverse scheme is in agreement with ground observations during ash-poor phases of the eruption. However, large discrepancies are observed during the ash-rich paroxysmal phase as a result of enhanced plume opacity affecting ground-based ultraviolet (UV) spectroscopic retrievals. As a consequence, the SO2 emission rate derived from the ground is underestimated by almost one order of magnitude. Altitudes of the SO2 emissions predicted by the inverse scheme are validated against an RGB image of the Moderate Resolution Imaging Spectroradiometer (MODIS) capturing the near-source atmospheric pathways followed by Etna plumes, in combination with forward trajectories from the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model. At a large distance from the source, modelled SO2 altitudes are compared with independent information on the volcanic cloud height. We find that the altitude predicted by the inverse scheme is in agreement with snapshots of the SO2 height retrieved from recent algorithms exploiting the high spectral resolution of IASI. The validity of the modelled SO2 altitude is further confirmed by the detection of a layer of particles at the same altitude by the spaceborne Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). Analysis of CALIOP colour and depolarization ratios suggests that these particles consist of sulfate aerosols formed from precursory volcanic SO2. The reconstruction of emission altitude, through inversion procedures which assimilate volcanic SO2 column amounts, requires specific meteorological conditions, especially sufficient wind shear so that gas parcels emitted at different altitudes follow distinct trajectories. We consequently explore the possibility and limits of assimilating in inverse schemes infrared (IR) imagery of the volcanic SO2 cloud altitude which will render the inversion procedure independent of the wind shear prerequisite. |
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| publications-1406 |
PEER REVIEWED ARTICLE |
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Höpfner, M., N. Glatthor, U. Grabowski, S. Kellmann, M. Kiefer, A. Linden, G. Stiller, T. von Clarmann, B. Funke, C.D. Boone, H. Schlager, A.Roiger, |
Volcanic emissions of SO2 into the stratosphere: global height-resolved observations by MIPAS during 2002 – 2012 |
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Uncategorized |
Uncategorized |
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No abstract available |
603557 |
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| publications-1407 |
PEER REVIEWED ARTICLE |
2015 |
Höpfner, M., Boone, C. D., Funke, B., Glatthor, N., Grabowski, U., Günther, A., Kellmann, S., Kiefer, M., Linden, A., Lossow, S., Pumphrey, H. C., R |
Sulfur dioxide (SO2) from MIPAS in the upper troposphere and lower stratosphere 2002–2012 |
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10.5194/acpd-15-5801-2015 |
Simulation & Modeling |
River Basins |
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Abstract. Vertically resolved distributions of sulfur dioxide (SO2) with global coverage in the height region from the upper troposphere to ~ 20 km altitude have been derived from observations by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on Envisat for the period July 2002 to April 2012. Retrieved volume mixing ratio profiles representing single measurements are characterized by typical errors in the range of 70–100 pptv and by a vertical resolution ranging from 3–5 km. Comparison with ACE-FTS observations revealed a slightly varying bias with altitude of −20 to 50 pptv for the MIPAS dataset in case of volcanically enhanced concentrations. For background concentrations the comparison showed a systematic difference between the two major MIPAS observation periods. After debiasing, the difference could be reduced to biases within −10 to 20 pptv in the altitude range of 10–20 km with respect to ACE-FTS. Further comparisons of the debiased MIPAS dataset with in-situ measurements from various aircraft campaigns showed no obvious inconsistencies within a range of around ±50 pptv. The SO2 emissions of more than thirty volcanic eruptions could be identified in the upper troposphere and lower stratosphere (UTLS). Emitted SO2 masses and lifetimes within different altitude ranges in the UTLS have been derived for a large part of these eruptions. Masses are in most cases within estimations derived from other instruments. From three of the major eruptions within the MIPAS measurement period – Kasatochi in August 2008, Sarychev in June 2009 and Nabro in June 2011 – derived lifetimes of SO2 for the altitude ranges 10–14, 14–18, and 18–22 km are 13.3±2.1, 23.6±1.2, and 32.3±5.5 d, respectively. By omitting periods with obvious volcanic influence we have derived background mixing ratio distributions of SO2. At 10 km altitude these indicate an annual cycle at northern mid- and high latitudes with maximum values in summer and an amplitude of about 30 pptv. At higher altitudes of about 16–18 km enhanced mixing ratios of SO2 can be found in the region of the Asian and the North-American monsoon in summer – a possible connection to an aerosol layer discovered by Vernier et al. (2011b) in that region. |
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| publications-1408 |
PEER REVIEWED ARTICLE |
2016 |
P. Sellitto , A. di Sarra , S. Corradini , M. Boichu , H. Herbin , P. Dubuisson , G. Sèze , D. Meloni , F. Monteleone , L. Merucci , J. Rusalem , G. |
Synergistic use of Lagrangian dispersion modelling, satellite and surface remote sensing measurements for the investigation of volcanic plumes: the Mount Etna eruption of 25–27 October 2013 |
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10.5194/acp-16-6841-2016 |
Uncategorized |
Precipitation & Ecological Systems |
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Abstract. In this paper we combine SO2 and ash plume dispersion modelling with satellite and surface remote sensing observations to study the regional influence of a relatively weak volcanic eruption from Mount Etna on the optical and micro-physical properties of Mediterranean aerosols. We analyse the Mount Etna eruption episode of 25–27 October 2013. The evolution of the plume along the trajectory is investigated by means of the FLEXible PARTicle Lagrangian dispersion (FLEXPART) model. The satellite data set includes true colour images, retrieved values of volcanic SO2 and ash, estimates of SO2 and ash emission rates derived from MODIS (MODerate resolution Imaging Spectroradiometer) observations and estimates of cloud top pressure from SEVIRI (Spinning Enhanced Visible and InfraRed Imager). Surface remote sensing measurements of aerosol and SO2 made at the ENEA Station for Climate Observations (35.52° N, 12.63° E; 50 m a.s.l.) on the island of Lampedusa are used in the analysis. The combination of these different data sets suggests that SO2 and ash, despite the initial injection at about 7.0 km altitude, reached altitudes around 10–12 km and influenced the column average aerosol particle size distribution at a distance of more than 350 km downwind. This study indicates that even a relatively weak volcanic eruption may produce an observable effect on the aerosol properties at the regional scale. The impact of secondary sulfate particles on the aerosol size distribution at Lampedusa is discussed and estimates of the clear-sky direct aerosol radiative forcing are derived. Daily shortwave radiative forcing efficiencies, i.e. radiative forcing per unit AOD (aerosol optical depth), are calculated with the LibRadtran model. They are estimated between −39 and −48 W m−2 AOD−1 at the top of the atmosphere and between −66 and −49 W m−2 AOD−1 at the surface, with the variability in the estimates mainly depending on the aerosol single scattering albedo. These results suggest that sulfate particles played a large role in the transported plume composition and radiative forcing, while the contribution by ash particles was small in the volcanic plume arriving at Lampedusa during this event. |
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| publications-1409 |
PEER REVIEWED ARTICLE |
2014 |
Sèze, G., J. Pelon, M. Derrien, H. Le Gléau & B. Six |
Evaluation against CALIPSO lidar observations of the multi-geostationary cloud cover and type dataset assembled in the framework of the Megha-Tropiques mission |
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10.1002/qj.2392 |
Uncategorized |
River Basins |
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To support the Megha‐Tropiques space mission, cloud mask and cloud type classification are needed at high spatial and time resolutions over the tropical belt for water vapour and precipitation analysis. For this purpose, visible and infrared radiance data from geostationary satellites (GEO) are used with a single algorithm initially developed by SAFNWC (Satellite Application Facility for Nowcasting) for Meteosat Second Generation. This algorithm has been adapted by SAFNWC to the spectral characteristics and field of view of each satellite. Retrieved cloud cover characteristics (cloud mask, classification and top pressure) are evaluated over four months in summer of 2009 against CALIOP lidar observations from the CALIPSO polar‐orbiting satellite. To better identify atmospheric and instrumental issues, separate analyses are performed over land and ocean, for 1:30 a.m. and 1:30 p.m. CALIPSO overpasses and for each GEO. Both mean cloud‐cover occurrence and instantaneous cloud‐cover statistics are compared. We found that each classification has specific features, which depend on observed cloud regimes and instrument capabilities. Most important, a common behaviour of the GEOs against CALIOP depending on cloud type is observed. We found that GEO cloud occurrence is lower by about 10% than for CALIOP, with the largest biases over land during daytime and the smallest over ocean during daytime. Further detailed analysis reveals specific discrepancies in the retrieved cloud types. As expected, high‐level clouds are detected more frequently by the lidar. We show that, over ocean when the optical thickness of detected high‐level clouds is limited to greater than 0.1 in the comparisons, multi‐spectral radiometry performs very similarly. However, the most significant difference is attributed to non‐detection of low‐level clouds that are often broken, which causes a reduction of up to 20% in low‐level cloud fraction and even 30% in some regions. Other significant differences are seen over land, where mid‐level clouds are not detected or are misclassified. |
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| publications-1410 |
PEER REVIEWED ARTICLE |
2014 |
Thibaut Dauhut , Jean-Pierre Chaboureau , Juan Escobar , Patrick Mascart |
Large-eddy simulations of Hector the convector making the stratosphere wetter |
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10.1002/asl2.534 |
Uncategorized |
Uncategorized |
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AbstractA large‐eddy simulation (LES) was performed for a Hector thunderstorm observed on 30 November 2005 over the Tiwi Islands. On that day, ice particles reaching 19‐km altitude were measured. The LES developed overshooting updrafts penetrating the stratosphere that compared well with observations. Much of the water injected in the form of ice particles sublimated in the lower stratosphere. Net hydration was found with a 16% increase in water vapour. While moistening appeared to be robust with respect to the grid spacing used, grid spacing on the order of 100 m may be necessary for a reliable estimate of hydration. |
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