Sulfur Dioxide Cloud Research Articles

Improving volcanic sulfur dioxide cloud dispersal forecasts by progressive assimilation of satellite observations

Forecasting the dispersal of volcanic clouds during an eruption is of primary importance, especially for ensuring aviation safety. As volcanic emissions are characterized by rapid variations of emission rate and height, the (generally) high level of uncertainty in the emission parameters represents a critical issue that limits the robustness of volcanic cloud dispersal forecasts. An inverse modeling scheme, combining satellite observations of the volcanic cloud with a regional chemistry-transport model, allows reconstructing this source term at high temporal resolution. We demonstrate here how a progressive assimilation of freshly acquired satellite observations, via such an inverse modeling procedure, allows for delivering robust sulfur dioxide (SO2) cloud dispersal forecasts during the eruption. This approach provides a computationally cheap estimate of the expected location and mass loading of volcanic clouds, including the identification of SO2-rich parts.

Remote sensing and inverse transport modeling of the Kasatochi eruption sulfur dioxide cloud

An analytical inversion method is used to estimate the vertical profile of sulfur dioxide (SO2) emissions from the major 2008 eruption of Kasatochi Volcano, located on the Aleutian Arc, Alaska. The method uses satellite‐observed total SO2 columns from the Global Ozone Monitoring Experiment‐2 (GOME‐2), Ozone Monitoring Instrument (OMI), and Atmospheric InfraRed Sounder (AIRS) during the first 2 days after the eruption, and an atmospheric transport model, FLEXPART, to calculate the vertical emission profile. The inversion yields an emission profile with two large emission maxima near 7 km above sea level (asl) and around 12 km asl, with smaller emissions up to 20 km. The total mass of SO2 injected into the atmosphere by the eruption is estimated to 1.7 Tg, with ∼1 Tg reaching the stratosphere (above 10 km asl). The estimated vertical emission profile is robust against changes of the assumed eruption time, meteorological input data, and satellite data used. Using the vertical emission profile, a simulation of the transport extending for 1 month after the eruption is performed. The simulated cloud agrees very well with SO2 columns observed by GOME‐2, OMI, and AIRS until 6 days after the eruption, and the altitudes agree with both Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observation measurements and ground‐based lidar observations to within 1 km. The method is computationally very fast. It is therefore suitable for implementation within an operational environment, such as the Volcanic Ash Advisory Centers, to predict the threat posed by volcanic emissions for air traffic.

Predicting and Validating the Tracking of a Volcanic Ash Cloud during the 2006 Eruption of Mt. Augustine Volcano

On 11 January 2006, Mount Augustine volcano in southern Alaska began erupting after 20-year repose. The Anchorage Forecast Office of the National Weather Service (NWS) issued an advisory on 28 January for Kodiak City. On 31 January, Alaska Airlines cancelled all flights to and from Anchorage after multiple advisories from the NWS for Anchorage and the surrounding region. The Alaska Volcano Observatory (AVO) had reported the onset of the continuous eruption. AVO monitors the approximately 100 active volcanoes in the Northern Pacific. Ash clouds from these volcanoes can cause serious damage to an aircraft and pose a serious threat to the local communities, and to transcontinental air traffic throughout the Arctic and sub-Arctic region. Within AVO, a dispersion model has been developed to track the dispersion of volcanic ash clouds. The model, Puff, was used operational by AVO during the Augustine eruptive period. Here, we examine the dispersion of a volcanic ash cloud from Mount Augustine across Alaska from 29 January through the 2 February 2006. We present the synoptic meteorology, the Puff predictions, and measurements from aerosol samplers, laser radar (or lidar) systems, and satellites. UAF aerosol samplers revealed the presence of volcanic aerosols at the surface at sitesmore » where Puff predicted the ash clouds movement. Remote sensing satellite data showed the development of the ash cloud in close proximity to the volcano and a sulfur-dioxide cloud further from the volcano consistent with the Puff predictions. Lidars showed the presence of volcanic aerosol with consistent characteristics aloft over Alaska and were capable of detecting the aerosol, even in the presence of scattered clouds and where the cloud is too thin/disperse to be detected by remote sensing satellite data. The lidar measurements revealed the different trajectories of ash consistent with the Puff predictions. Dispersion models provide a forecast of volcanic ash cloud movement that might be undetectable by any other means but are still a significant hazard. Validation is the key to assessing the accuracy of any future predictions. The study highlights the use of multiple and complementary observations used in detecting the trajectory ash cloud, both at the surface and aloft within the atmosphere.« less

Tracking volcanic sulfur dioxide clouds for aviation hazard mitigation

Satellite measurements of volcanic sulfur dioxide (SO2) emissions can provide critical information for aviation hazard mitigation, particularly when ash detection techniques fail. Recent developments in space-based SO2 monitoring are discussed, focusing on daily, global ultraviolet (UV) measurements by the Ozone Monitoring Instrument (OMI) on NASA’s Aura satellite. OMI’s high sensitivity to SO2 permits long-range tracking of volcanic clouds in the upper troposphere and lower stratosphere (UTLS) and accurate mapping of their perimeters to facilitate avoidance. Examples from 2006 to 2007 include eruptions of Soufriere Hills (Montserrat), Rabaul (Papua New Guinea), Nyamuragira (DR Congo), and Jebel at Tair (Yemen). A tendency for some volcanic clouds to occupy the jet stream suggests an increased threat to aircraft that exploit this phenomenon. Synergy between NASA A-Train sensors such as OMI and the Atmospheric Infrared Sounder (AIRS) on the Aqua satellite can provide critical information on volcanic cloud altitude. OMI and AIRS SO2 data products are being produced in near real-time for distribution to Volcanic Ash Advisory Centers (VAACs) via a NOAA website. Operational issues arising from these improved SO2 measurements include the reliability of SO2 as proxy for co-erupted ash, the duration of VAAC advisories for long-lived volcanic clouds, and the potential effects of elevated concentrations of SO2 and sulfate aerosol in ash-poor clouds on aircraft and avionics (including cumulative effects after multiple inadvertent transits through dilute clouds). Further research is required in these areas. Aviation community assistance is sought through continued reporting of sulfurous odors or other indications of diffuse volcanic cloud encounters, in order to validate the satellite retrievals.

The December 1981 eruption of Nyamuragira Volcano (Zaire), and the origin of the “mystery cloud” of early 1982

The “mystery” volcanic aerosols observed in early 1982 were produced by the eruption of Nyamuragira in eastern Zaire. Large sulfur dioxide clouds associated with this volcano were found in the total ozone mapping spectrometer data beginning on December 26, 1981, continuing into early January 1982. This fissure eruption produced 3 million tons of sulfur dioxide in clouds that rose only to the tropopause level on the basis of winds and inferred chemical loss rates (about 20%/day), which are faster than stratospheric loss rates. Two thirds of the SO2 was produced in the first 3 days of the eruption. In the 1980s this eruption was exceeded in sulfur dioxide output only by the April 1982 eruption of El Chichon.

Evaluation of sulfur dioxide emissions from explosive volcanism: the 1982–1983 eruptions of Galunggung, Java, Indonesia

Galunggung volcano, Java, awoke from a 63-year quiescence in April 1982, and erupted sporadically through January 1983. During its most violent period from April to October, the Cikasasah Volcano Observatory reported 32 large and 56 moderate to small eruptions. From April 5 through September 19 the Total Ozone Mapping Spectrometer (TOMS), carried on NASA's Nimbus-7 satellite, detected and measured 24 different sulfur dioxide clouds; an estimated 1730 kilotons (kt) of SO 2 were outgassed by these explosive eruptions. The trajectories, and rapid dispersion rates, of the SO 2 clouds were consistent with injection altitudes below the tropopause. An additional 300 kt of SO 2 were estimated to have come from 64 smaller explosive eruptions, based on the detection limit of the TOMS instrument. For the first time, an extended period of volcanic activity was monitored by remote sensing techniques which enabled observations of both the entire SO 2 clouds produced by large explosive eruptions (using TOMS), and the relatively lower levels of SO 2 emissions during non-explosive outgassing (using the Correlation Spectrometer, or COSPEC). Based on COSPEC measurements from August 1982 to January 1983, and on the relationship between explosive and non-explosive degassing, approximately 400 kt of SO 2 were emitted during non-explosive activity. The total sulfur dioxide outgassed from Galunggung volcano from April 1982 to January 1983 is calculated to be 2500 kt (± 30%) from both explosive and non-explosive activity. While Galunggung added large quantities of sulfur dioxide to the atmosphere, its sporadic emissions occurred in relatively small events distributed over several months, and reached relatively low altitudes, and are unlikely to have significantly affected aerosol loading of the stratosphere in 1982 by volcanic activity.

Global tracking of the SO2 clouds from the June, 1991 Mount Pinatubo eruptions

The explosive June 1991 eruptions of Mount Pinatubo produced the largest sulfur dioxide cloud detected by the Total Ozone Mapping Spectrometer (TOMS) during its 13 years of operation: approximately 20 million tons of SO2, predominantly from the cataclysmic June 15th eruption. The SO2 cloud observed by the TOMS encircled the Earth in about 22 days (∼21 m/s); however, during the first three days the leading edge of the SO2 cloud moved with a speed that averaged ∼35 m/s. Compared to the 1982 El Chichón eruptions, Pinatubo outgassed nearly three times the amount of SO2 during its explosive phases. The main cloud straddled the equator within the first two weeks of eruption, whereas the El Chichón cloud remained primarily in the northern hemisphere. Our measurements indicate that Mount Pinatubo has produced a much larger and perhaps longer‐lasting SO2 cloud; thus, climatic responses to the Pinatubo eruption may exceed those of El Chichón.

Transport of Cerro Hudson SO2 clouds

The Cerro Hudson volcano in southern Chile (45.92°S, 73.0°W) emitted large ash and sulfur dioxide clouds on August 12–15, following several days of minor activity [Global Volcanism Network Bulletin, 1991]. The SO2 clouds were observed using (preliminary) near real‐time data from the Total Ozone Mapping Spectrometer (TOMS) as they encircled the south polar region. The injection of SO2 into the stratosphere has essentially created a gigantic chemical tracer that could provide new insights into the wind patterns and seasonal circulation around the Antarctic region.around the Antarctic region. The TOMS instrument, on board the National Aeronautic and Space Administration's Nimbus 7 satellite, measures the ratio of backscattered Earth radiance to incoming solar irradiance in the ultraviolet spectrum. Although originally designed to measure ozone, it was later discovered that the TOMS instrument could also detect and quantify SO2 [Krueger, 1985]. After this discovery, measurements from TOMS were examined for SO2 emissions for all recorded volcanic eruptions since Nimbus‐7 was launched in October 1978, and current data are analyzed as new eruptions occur. The satellite is in a polar, Sun‐synchronous orbit so that it crosses the equator at local noon and observes the whole sunlit Earth in approximately 14 orbits each day. Total column amounts of SO2 are determined that represent the amount of gas affecting the reflection of ultraviolet light through a column of the atmosphere from the satellite to the reflecting surface, Earth, given in terms of milli atmospheres centimeter (1000 milli atm cm = a gas layer 1‐cm thick at STP). The mass of SO2 is calculated by integrating over the cloud area to obtain a volume, then converting to tons.

Sighting of El Chichón Sulfur Dioxide Clouds with the Nimbus 7 Total Ozone Mapping Spectrometer

The eruptions of El Chichón volcano on 28 March and 3 and 4 April 1982 were observed by the Nimbus 7 total ozone mapping spectrometer due to strong absorption by volcanic gases at the shortest wavelengths of the spectrometer (312.5 and 317.5 nanometers). These ultraviolet pictures permit a measurement of the volume, dispersion, and drift of volcanic gas clouds. The tropospheric clouds were rapidly dispersed in westerly winds while persistent stratospheric clouds drifted in easterly winds at speeds up to 13 meters per second. The spectral reflectance is consistent with sulfur dioxide absorption and rules out carbon disulfide as a major constituent. A preliminary estimate of the mass of sulfur dioxide deposited in the stratosphere by the large eruptions on 3 and 4 April is 3.3 x 10(6) tons. Prior estimates of volcanic cloud volume were based on extrapolation of locally measured sulfur dioxide concentrations.