scholarly journals The 2019 Raikoke volcanic eruption – Part 1: Dispersion model simulations and satellite retrievals of volcanic sulfur dioxide

2021 ◽  
Vol 21 (14) ◽  
pp. 10851-10879
Author(s):  
Johannes de Leeuw ◽  
Anja Schmidt ◽  
Claire S. Witham ◽  
Nicolas Theys ◽  
Isabelle A. Taylor ◽  
...  
Keyword(s):  
High Resolution ◽  
Sulfur Dioxide ◽  
Lower Stratosphere ◽  
Temporal Evolution ◽  
Dispersion Modelling ◽  
Dispersion Models ◽  
Model Simulations ◽  
Model Skill ◽  
Horizontal Extent ◽  
Satellite Retrievals

Abstract. Volcanic eruptions can cause significant disruption to society, and numerical models are crucial for forecasting the dispersion of erupted material. Here we assess the skill and limitations of the Met Office's Numerical Atmospheric-dispersion Modelling Environment (NAME) in simulating the dispersion of the sulfur dioxide (SO2) cloud from the 21–22 June 2019 eruption of the Raikoke volcano (48.3∘ N, 153.2∘ E). The eruption emitted around 1.5±0.2 Tg of SO2, which represents the largest volcanic emission of SO2 into the stratosphere since the 2011 Nabro eruption. We simulate the temporal evolution of the volcanic SO2 cloud across the Northern Hemisphere (NH) and compare our model simulations to high-resolution SO2 measurements from the TROPOspheric Monitoring Instrument (TROPOMI) and the Infrared Atmospheric Sounding Interferometer (IASI) satellite SO2 products. We show that NAME accurately simulates the observed location and horizontal extent of the SO2 cloud during the first 2–3 weeks after the eruption but is unable, in its standard configuration, to capture the extent and precise location of the highest magnitude vertical column density (VCD) regions within the observed volcanic cloud. Using the structure–amplitude–location (SAL) score and the fractional skill score (FSS) as metrics for model skill, NAME shows skill in simulating the horizontal extent of the cloud for 12–17 d after the eruption where VCDs of SO2 (in Dobson units, DU) are above 1 DU. For SO2 VCDs above 20 DU, which are predominantly observed as small-scale features within the SO2 cloud, the model shows skill on the order of 2–4 d only. The lower skill for these high-SO2-VCD regions is partly explained by the model-simulated SO2 cloud in NAME being too diffuse compared to TROPOMI retrievals. Reducing the standard horizontal diffusion parameters used in NAME by a factor of 4 results in a slightly increased model skill during the first 5 d of the simulation, but on longer timescales the simulated SO2 cloud remains too diffuse when compared to TROPOMI measurements. The skill of NAME to simulate high SO2 VCDs and the temporal evolution of the NH-mean SO2 mass burden is dominated by the fraction of SO2 mass emitted into the lower stratosphere, which is uncertain for the 2019 Raikoke eruption. When emitting 0.9–1.1 Tg of SO2 into the lower stratosphere (11–18 km) and 0.4–0.7 Tg into the upper troposphere (8–11 km), the NAME simulations show a similar peak in SO2 mass burden to that derived from TROPOMI (1.4–1.6 Tg of SO2) with an average SO2 e-folding time of 14–15 d in the NH. Our work illustrates how the synergy between high-resolution satellite retrievals and dispersion models can identify potential limitations of dispersion models like NAME, which will ultimately help to improve dispersion modelling efforts of volcanic SO2 clouds.

scholarly journals The 2019 Raikoke volcanic eruption: Part 1 Dispersion model simulations and satellite retrievals of volcanic sulfur dioxide

2020 ◽  
Author(s):  
Johannes de Leeuw ◽  
Anja Schmidt ◽  
Claire S. Witham ◽  
Nicolas Theys ◽  
Isabelle A. Taylor ◽  
...  
Keyword(s):  
High Resolution ◽  
Sulfur Dioxide ◽  
Lower Stratosphere ◽  
Temporal Evolution ◽  
Dispersion Modelling ◽  
High Concentration ◽  
Model Simulations ◽  
Model Skill ◽  
Horizontal Extent ◽  
Satellite Retrievals

Abstract. Volcanic eruptions can cause significant disruption to society and numerical models are crucial for forecasting the dispersion of erupted material. Here we assess the skill and limitations of the Met Office’s Numerical Atmospheric-dispersion Modelling Environment (NAME) in simulating the dispersion of the sulfur dioxide (SO2) cloud from the 21–22 June 2019 eruption of the Raikoke volcano (48.3° N, 153.2° E). The eruption emitted around 1.5 ± 0.2 Tg of SO2, which represents the largest volcanic emission of SO2 into the stratosphere since the 2011 Nabro eruption. We simulate the temporal evolution of the volcanic SO2 cloud across the Northern Hemisphere (NH) and compare our model simulations to high-resolution SO2 measurements from the Tropospheric Monitoring Instrument (TROPOMI) and the Infrared Atmospheric Sounding Interferometer (IASI) satellite SO2 products. We show that NAME accurately simulates the observed location and horizontal extent of the SO2 cloud during the first 2–3 weeks after the eruption, but is unable, in its standard configuration, to capture the extent and precise location of very high-concentration regions within the volcanic cloud. Using the Fractional Skill Score as metric for model skill, NAME shows skill in simulating the horizontal extent of the cloud for 12–17 days after the eruption where vertical column densities (VCD) of SO2 (in Dobson Units, DU) are above 1 DU. For SO2 VCDs above 20 DU, which are predominantly observed as small-scale features within the SO2 cloud, the model shows skill on the order of 2–4 days only. The lower skill for these high-concentration regions is partly explained by the model-simulated SO2 cloud in NAME being too diffuse compared to TROPOMI retrievals. Reducing the standard diffusion parameters used in NAME by a factor of four results in a slightly increased model skill during the first five days of the simulation, but on longer timescales the simulated SO2 cloud remains too diffuse when compared to TROPOMI measurements. We find that the temporal evolution of the NH-mean SO2 mass burden simulated by NAME strongly depends on the fraction of SO2 mass emitted into the lower stratosphere, which is uncertain for the 2019 Raikoke eruption. When emitting 0.9–1.1 Tg of SO2 into the lower stratosphere (11–18 km) and 0.4–0.7 Tg into the upper troposphere (8–11 km), both NAME and TROPOMI show a similar peak in SO2 mass burden (1.4–1.6 Tg of SO2) with an average SO2 e-folding time of 14–15 days in the NH. Our work demonstrates the large potential of using high-resolution satellite retrievals to identify and rectify limitations in dispersion models like NAME, which will ultimately help to improve dispersion modelling efforts of volcanic SO2 clouds.

scholarly journals Spatio-Temporal Variations of Atmospheric NH3 over East Asia by Comparison of Chemical Transport Model Results, Satellite Retrievals and Surface Observations

Atmosphere ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 900 ◽  
Author(s):  
Zhe Wang ◽  
Itsushi Uno ◽  
Kazuo Osada ◽  
Syuichi Itahashi ◽  
Keiya Yumimoto ◽  
...  
Keyword(s):  
High Resolution ◽  
East Asia ◽  
Temporal Variations ◽  
Central China ◽  
Model Simulations ◽  
Satellite Retrievals ◽  
In Situ Observations ◽  
Spatio Temporal ◽  
Surface Observations

Atmospheric ammonia (NH3) plays an important role in the formation of secondary inorganic aerosols, the neutralization of acid rain, and the deposition to ecosystems, but has not been well understood yet, especially over East Asia. Based on the GEOS-Chem model results, the IASI satellite retrievals, the in-site surface observations of a nationwide filter pack (FP) network over Japan and the long-term high resolution online NH3 measurements at Fukuoka of western Japan, the spatio-temporal distributions of atmospheric NH3 over East Asia was analyzed comprehensively. A significant seasonal variation with a summer peak was found in all datasets. Comparison between the satellite retrievals and model simulations indicated that the IASI NH3 vertical column density (VCD) showed good consistency with GEOS-Chem results over North and central China, but had large differences over South China due to the effect of clouds. Over the Japan area, GEOS-Chem simulated NH3 concentrations successfully reproduced the spatio-temporal variations compared with in-situ observations, while IASI NH3 VCD retrievals were below or near the detection limit and difficult to obtain a reasonable correlation for with model results. The comprehensive analysis indicated that there were still some differences among different datasets, and more in-situ observations, improved satellite retrievals, and high-resolution model simulations with more accurate emissions are necessary for better understanding the atmospheric NH3 over East Asia.

scholarly journals Chemistry-climate model simulations of the Mt. Pinatubo eruption using CCMI and CMIP6 stratospheric aerosol data

2017 ◽  
Author(s):  
Laura Revell ◽  
Andrea Stenke ◽  
Beiping Luo ◽  
Stefanie Kremser ◽  
Eugene Rozanov ◽  
...  
Keyword(s):  
Lower Stratosphere ◽  
Climate Model ◽  
Stratospheric Aerosol ◽  
Radiative Properties ◽  
Gap Filling ◽  
Data Set ◽  
Model Simulations ◽  
Ozone Loss ◽  
Pinatubo Eruption ◽  
Climate Model Simulations

Abstract. To simulate the impacts of volcanic eruptions on the stratosphere, chemistry-climate models that do not include an online aerosol module require temporally and spatially resolved aerosol size parameters for heterogeneous chemistry and aerosol radiative properties as a function of wavelength. For phase 1 of the Chemistry-Climate Model Initiative (CCMI-1) and, later, for phase 6 of the Coupled Model Intercomparison Project (CMIP6) two such stratospheric aerosol data sets were compiled, whose functional capability and representativeness are compared here. For CCMI-1, the SAGE-4λ data set was compiled, which hinges on the measurements at four wavelengths of the SAGE (Stratospheric Aerosol and Gas Experiment) II satellite instrument and uses ground-based Lidar measurements for gap-filling immediately after the Mt. Pinatubo eruption, when the stratosphere was optically opaque for SAGE II. For CMIP6, the new SAGE-3λ data set was compiled, which excludes the least reliable SAGE II wavelength and uses CLAES (Cryogenic Limb Array Etalon Spectrometer) measurements on UARS, the Upper Atmosphere Research Satellite, for gap-filling following the Mt. Pinatubo eruption instead of ground-based Lidars. Here, we performed SOCOLv3 (Solar Climate Ozone Links version 3) chemistry-climate model simulations of the recent past (1986–2005) to investigate the impact of the Mt. Pinatubo eruption in 1991 on stratospheric temperature and ozone and how this response differs depending on which aerosol data set is applied. The use of SAGE-4λ results in heating and ozone loss being overestimated in the lower stratosphere compared to observations in the post-eruption period by approximately 3 K and 0.2 ppmv, respectively. However, less heating occurs in the model simulations based on SAGE-3λ, because the improved gap-filling procedures after the eruption lead to less aerosol loading in the tropical lower stratosphere. As a result, simulated temperature anomalies in the model simulations based on SAGE-3λ for CMIP6 are in excellent agreement with MERRA and ERA-Interim reanalyses in the post-eruption period. Less heating in the simulations with SAGE-3λ means that the rate of tropical upwelling does not strengthen as much as it does in the simulations with SAGE-4λ, which limits dynamical uplift of ozone and therefore provides more time for ozone to accumulate in tropical mid-stratospheric air. Ozone loss following the Mt. Pinatubo eruption is overestimated by 0.1 ppmv in the model simulations based on SAGE-3λ, which is a better agreement with observations than in the simulations based on SAGE-4λ. Overall, the CMIP6 stratospheric aerosol data set, SAGE-3λ, allows SOCOLv3 to more accurately simulate the post-Pinatubo eruption period.

Organic and inorganic bromine measurements around the extratropical tropopause and lowermost stratosphere (Ex-LMS): Insights into transport pathways and total bromine 

2021 ◽  
Author(s):  
Meike Rotermund ◽  
Vera Bense ◽  
Martyn Chipperfield ◽  
Andreas Engel ◽  
Jens-Uwe Grooß ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Lower Stratosphere ◽  
Boreal Summer ◽  
Transport Modelling ◽  
Transport Pathways ◽  
Air Mass ◽  
Model Simulations ◽  
Extratropical Tropopause ◽  
Background Air ◽  
Middle Stratosphere

<p>We report on measurements of total bromine (Br<sup>tot</sup>) in the upper troposphere and lower stratosphere (UTLS) taken from the German High Altitude and LOng range research aircraft (HALO) over the North Atlantic, Norwegian Sea and north-western Europe in September/ October 2017 during the WISE (Wave-driven ISentropic Exchange) research campaign. Br<sup>tot</sup> is calculated from measured total organic bromine (Br<sup>org</sup>) (i.e., the sum of bromine contained in CH<sub>3</sub>Br, the halons and the major very short-lived brominated substances) added to inorganic bromine (Br<sub>y</sub><sup>inorg</sup>), evaluated from measured BrO and photochemical modelling. Combining these data, the weighted mean [Br<sup>tot</sup>] is 19.2 ± 1.2 ppt in the extratropical lower stratosphere (Ex-LS) of the northern hemisphere. The inferred average Br<sup>tot</sup> for the Ex-LS is slightly smaller than expected for the middle stratosphere in 2016 (~19.6 ppt (ranging from 19-20 ppt) as reported by the WMO/UNEP Assessment (2018)). However, it reflects the expected variability in Br<sup>tot</sup> in the Ex-LS due to influxes of shorter lived brominated source and product gases from different regions of entry. A closer look into Br<sup>org</sup> and Br<sub>y</sub><sup>inorg</sup> as well as simultaneously measured transport tracers (CO, N<sub>2</sub>O, ...) and an air mass lag-time tracer (SF<sub>6</sub>), suggests that a filament of air with elevated Br<sup>tot</sup> protruded into the extratropical lowermost stratosphere (Ex-LMS) from 350-385 K and between equivalent latitudes of 55-80˚N (high bromine filament – HBrF). Lagrangian transport modelling shows the multi-pathway contributions to Ex-LMS bromine. According to CLaMS air mass origin simulations, contributions to the HBrF consist of predominantly isentropic transport from the tropical troposphere (also with elevated [Br<sup>tot</sup>] = 21.6 ± 0.7 ppt) as well as a smaller contribution from an exchange across the extratropical tropopause which are mixed into the stratospheric background air. In contrast, the surrounding LS above and below the HBrF has less tropical tropospheric air, but instead additional stratospheric background air. Of the tropical tropospheric air in the HBrF, the majority is from the outflow of the Asian monsoon anticyclone and the adjacent tropical regions, which greatly influences concentrations of trace gases transported into the Ex-LMS in boreal summer and fall. The resulting increase of Br<sup>tot</sup> in the Ex-LMS and its consequences for ozone is investigated through the TOMCAT/SLIMCAT model simulations. However, more extensive monitoring of total stratospheric bromine in more aged air (i.e., in the middle stratosphere) as well as globally and seasonally is required in addition to model simulations to fully understand its impact on Ex-LMS ozone and the radiative forcing of climate.</p>

scholarly journals Representation of Vertical Atmospheric Structures by Radio Occultation Observations in the Upper Troposphere and Lower Stratosphere: Comparison to High-Resolution Radiosonde Profiles

2019 ◽  
Vol 36 (4) ◽  
pp. 655-670 ◽  
Author(s):  
Zhen Zeng ◽  
Sergey Sokolovskiy ◽  
William S. Schreiner ◽  
Doug Hunt
Keyword(s):  
High Resolution ◽  
Radio Occultation ◽  
Lower Stratosphere ◽  
Small Scale ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Low Latitudes ◽  
Observational Noise ◽  
Horizontal Inhomogeneity ◽  
Cold Point

AbstractGlobal positioning system (GPS) radio occultation (RO) is capable of retrieving vertical profiles of atmospheric parameters with high resolution (<100 m), which can be achieved in spherically symmetric atmosphere. Horizontal inhomogeneity of real atmosphere results in representativeness errors of retrieved profiles. In most cases these errors increase with a decrease of vertical scales of atmospheric structures and may not allow one to fully utilize the physical resolution of RO. Also, GPS RO–retrieved profiles are affected by observational noise of different types, which, in turn, affect the representation of small-scale atmospheric structures. This study investigates the effective resolution and optimal smoothing of GPS RO–retrieved temperature profiles using high-pass filtering and cross correlation with collocated high-resolution radiosondes. The effective resolution is a trade-off between representation of real atmospheric structures and suppression of observational noise, which varies for different latitudes (15°S–75°N) and altitudes (10–27 km). Our results indicate that at low latitudes the effective vertical resolution is about 0.2 km near the tropical tropopause layer and about 0.5 km in the lower stratosphere. The best resolution of 0.1 km is at the cold-point tropical tropopause. The effective resolutions at the midlatitudes are slightly worse than at low latitudes, varying from ~0.2 to 0.6 km. At high latitudes, the effective resolutions change notably with altitude from ~0.2 km at 10–15 km to ~1.4 km at 22–27 km. Our results suggest that the atmospheric inhomogeneity plays an important role in the representation of the vertical atmospheric structures by RO measurements.

scholarly journals HRTS Evidence for Rotation of Transition Region Temperature Spicules

1984 ◽  
Vol 86 ◽  
pp. 32-35
Author(s):  
J.W. Cook ◽  
G.E. Brueckner ◽  
J.-D.F. Bartoe ◽  
D.G. Socker
Keyword(s):  
High Resolution ◽  
Coronal Hole ◽  
Solar Disk ◽  
Temporal Evolution ◽  
Solar Limb ◽  
Scientific Objective ◽  
Short Term ◽  
Central Wavelength ◽  
Region Temperature ◽  
Slit Length

The HRTS (High Resolution Telescope and Spectrograph) instrument is a high spectral (0.05 Å) and spatial (<1 arc sec) resolution spectrograph with a slit length of 900 arc sec on the solar disk (see Bartoe and Brueckner 1975, 1978). HRTS contains in addition a double grating, zero dispersion broadband spectroheliograph which images the spectrograph slit jaw plate (see Cook et al. 1983). The central wavelength is tunable by changing the grating geometry. Hα images are also photographed from the slit jaw plate image. HRTS has been flown four times as a rocket payload, and will fly in April 1985 as one of the solar experiments aboard Spacelab 2. The four rocket flights of the HRTS program have each been customized for a particular scientific objective. For the fourth flight, because the original hardware was utilized as the basis of the Spacelab HRTS, the opportunity was used to design and build a new rocket HRTS instrument specialized for observations at the solar limb. In this configuration the photographic speed was increased, a new curved slit was fabricated, and the spectroheliograph was modified for limb observations. The scientific observing program was a study of structure and short term temporal evolution at the limb, with a comparison of quiet and coronal hole areas.

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