SAGE III/ISS aerosol/cloud categorization and its impact on GloSSAC

Kovilakam, Mahesh; Thomason, L. W.; Knepp, T. N.

doi:10.5194/amt-2022-222

Cited by 3 publications

(7 citation statements)

References 20 publications

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“…Since most ice cloud particles observed by a SAGE instrument are optically large, they essentially all have extinction ratios of about 1, and the more cloud-like the observation the closer the extinction ratio approaches 1. This is a well-known phenomenon and the basis for essentially all cloud detection algorithms for SAGElike instruments (Thomason and Vernier, 2013;Kovilakam et al, 2023). For the Norman Wells event, as can be seen in Fig.…”

Section: Identifying and Depicting Outlier Eventsmentioning

confidence: 82%

“…In the absence of information suggesting otherwise, high extinction and low ratio data points are most often interpreted as "cloud" or aerosol-cloud mixtures (e.g., Thomason and Vernier, 2013). This observation forms the basis for essentially all mechanisms to identify and remove the effects of clouds on the aerosol observations including for such data sets as GloSSAC (Kovilakam et al, 2023). Despite numerous positive outliers in Fig.…”

Section: Differentiating Between Outlier Events and Cloudsmentioning

confidence: 99%

“…We focus on these records since they are very compatible data sets that produce aerosol extinction coefficient profiles at essentially the same wavelengths using the same measurement approach and very similar processing algorithms to produce near-global observations. Issues related to uncertainties in characterizing the scattering processes add potential systematic bias to the records from OSIRIS, OMPS, and CALIPSO and make intercomparisons of these records with SAGE and each other more difficult (Kovilakam et al, 2023;Bourassa et al, 2023), and inclusion of these data sets is deferred. The SAGE instruments are key sources of data to the Global Space-based Stratospheric Aerosol Climatology (GloSSAC), and a key outcome of this study is to infer the impact of smoke on this climate data record.…”

Section: Introductionmentioning

confidence: 99%

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Quantifying SAGE II (1984–2005) and SAGE III/ISS (2017–2022) observations of smoke in the stratosphere

Thomason,

Knepp

2023

Atmos. Chem. Phys.

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Abstract. Using a common analysis approach for data sets produced by the Stratospheric Aerosol and Gas Experiment instruments SAGE II and SAGE III/ISS, we identify 13 likely smoke events based on enhancements in the aerosol extinction coefficient. Nine of these are sufficiently large compared to ambient aerosol levels to compute mean mid-latitude 1020 nm optical depth enhancements that range from 0.0005 to 0.011. We also note that, for large events, the 525 to 1020 nm aerosol extinction coefficient ratio asymptotes at a high extinction coefficient to values between 2 and 3, suggesting that the aerosol radius is relatively small (< 0.3 µm) and relatively consistent from event to event. Most of these events are primarily confined to the lower stratosphere and rarely can be observed above 20 km. We also infer an increase in the frequency of smoke events between the SAGE II (1984–1991, 1996–2005) and SAGE III/ISS (2017-present) periods by almost a factor of 2 and also note that the two largest events occur in the latter data set. However, given the low frequencies overall, we are not confident that the differences can be attributed to changes between the two periods. We also attempt to disentangle the mixing of aerosol in the Northern Hemisphere summer of 1991 from a pyrocumulus event (Baie-Comeau, Quebec) and Mt. Pinatubo and conclude that, while there is evidence for smoke in the lower stratosphere, virtually all of the enhanced aerosol observations in the northern mid-latitudes in the summer of 1991 are associated with the Mt. Pinatubo eruption.

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Section: Identifying and Depicting Outlier Eventsmentioning

confidence: 82%

Section: Differentiating Between Outlier Events and Cloudsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Quantifying SAGE II (1984–2005) and SAGE III/ISS (2017–2022) observations of smoke in the stratosphere

Thomason,

Knepp

2023

Atmos. Chem. Phys.

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“…Our algorithm follows the approach in Bourassa (2008), Thomason and Vernier (2013), Schoeberl et al (2021) and Kovilakam et al (2022). Using the SAKATRAN radiative transfer model, we show that the color ratio is independent of the number density and only a function of the particle size for a log-normal function size distribution with a fixed width.…”

Section: Discussionmentioning

confidence: 99%

“…In our algorithm, we use extinction at two wavelengths to constrain both the derived number density and size using the Level 2 (L2) extinction products from the current OMPS algorithm. The algorithm is based on Bourassa et al (2007) approach using OSIRIS measurements and Thomason and Vernier's (2013) work using SAGE II measurements that have been extended to SAGE III/ISS (Schoeberl et al, 2021;Kovilakam et al, 2022). In the next section, we detail the algorithm and results.…”

Section: Introductionmentioning

confidence: 99%

Using OMPS-LP color ratio to extract stratospheric aerosol particle size and concentration with application to volcanic eruptions

Wang

Schoeberl

Taha

et al. 2023

Preprint

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Abstract. We develop an algorithm that uses the aerosol extinction at two wavelengths (color ratio) to derive the size and number density for stratospheric aerosols. We apply our algorithm to Ozone Mapping Profiler Suite Limb Profiler (OMPS-LP) L2 and Stratospheric Aerosol and Gas Experiment (SAGE) data. We show that the color ratio between two wavelengths (e.g. 510 nm/869 nm) is insensitive to aerosol concentration and thus can be used to derive aerosol size assuming a log-normal size distribution. With the size and the extinction, we can compute a number density consistent with both wavelengths. Our results compare favorably to balloon borne particle size and concentration measurements. Our results are also consistent with SAGE solar occultation measurements. Finally, we show the background distribution of stratospheric aerosols and the changes in those distributions during the Reikoke and Hunga Tonga-Hunga Ha’apai volcanic eruptions. We also show the evolution of the size and number density of aerosols following both of those eruptions.

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An ocean of stratospheric aerosols after the Hunga Tonga– Hunga Haʻapai volcanic eruption

Vernier¹

2023

Preprint

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Volcanic eruptions are key drivers of the natural variability of the Earth’s Climate system. The sulfate aerosols produced by major volcanic events can last for several years and reduce surface temperatures while warming the stratosphere1. However, this “classic” view is now challenged by the January 15th, 2022, Hunga Tonga Hunga Ha’apai submarine eruption. For the first time in the satellite era, a volcano injected material up to the mesosphere2 leading to an increase in the global stratospheric water vapor burden by 10% from seawater injected3. However, no information is available about the chemical properties of the plume. Herein, we show a detailed analysis of the chemical composition of the HTHH plume through a new balloon-based sampling technique. The ion chromatographic analysis of the sampled aerosols shows the presence of sea salts as opposed to a pure sulfate plume alone. The chemical analysis thereby revealed that the HTHH is more complex than initially thought and may explain the unexpected aerosol burden created by this eruption relative to the expected sulfate aerosol produced from the modest 0.6 Tg SO2 injected. These results challenge the current models that simulate the climate impacts of volcanoes.

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SAGE III/ISS aerosol/cloud categorization and its impact on GloSSAC

Cited by 3 publications

References 20 publications

Quantifying SAGE II (1984–2005) and SAGE III/ISS (2017–2022) observations of smoke in the stratosphere

Quantifying SAGE II (1984–2005) and SAGE III/ISS (2017–2022) observations of smoke in the stratosphere

Using OMPS-LP color ratio to extract stratospheric aerosol particle size and concentration with application to volcanic eruptions

An ocean of stratospheric aerosols after the Hunga Tonga– Hunga Haʻapai volcanic eruption

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