The 2022 eruption of the Hunga Tonga‐Hunga Ha'apai volcano caused substantial impacts on the atmosphere, including a massive injection of water vapor, and the largest increase in stratospheric ...aerosol for 30 years. The Ozone Mapping and Profiler Suite (OMPS) Limb Profiler instrument has been critical in monitoring the amount and spread of the volcanic aerosol in the stratosphere. We show that the rapid imagery from the OMPS instrument enables a tomographic retrieval of the aerosol extinction that reduces a critical bias of up to a factor of two, and improves vertical structure and agreement with coincident lidar and occultation observations. Due to the vertically thin and heterogeneous nature of the volcanic aerosol, this impacts integrated values of aerosol across latitude, altitude, and time for several months. We also investigate the systematic impact of uncertainty in assumed particle size that result in an underestimation of the aerosol extinction at the peak of the volcanic aerosol layer.
Plain Language Summary
The Hunga Tonga‐Hunga Ha'apai volcano erupted in 2022. The eruption plume went higher into the atmosphere than ever observed before in the modern age. It also carried large amounts of water vapor and other gases and particles, called aerosols, into the stratosphere. The NASA satellite instrument, called the Ozone Mapping and Profiler Suite (OMPS) Limb Profiler, has given us valuable measurements of these aerosols, which are helpful in understanding the impact the volcanic eruption might have on climate. We use an advanced technique to analyze the OMPS measurements that provides a clearer view of the plume. This analysis gives somewhat different results about the thickness of the volcanic plume than the standard method.
Key Points
Tomographic retrievals reduce a critical bias in Ozone Mapping and Profiler Suite Limb Profiler volcanic aerosol extinction, improving agreement with Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observation and Stratospheric Aerosol and Gas Experiment III/International Space Station
Biases of up to a factor of two extend beyond the early plume, with zonal, temporal, and altitude integrated values affected for months
Uncertainty in particle size distribution also has an impact that should be considered when analyzing aerosol loading
The Australian bushfires around the turn of the year 2020 generated an unprecedented perturbation of stratospheric composition, dynamical circulation and radiative balance. Here we show from ...satellite observations that the resulting planetary-scale blocking of solar radiation by the smoke is larger than any previously documented wildfires and of the same order as the radiative forcing produced by moderate volcanic eruptions. A striking effect of the solar heating of an intense smoke patch was the generation of a self-maintained anticyclonic vortex measuring 1000 km in diameter and featuring its own ozone hole. The highly stable vortex persisted in the stratosphere for over 13 weeks, travelled 66,000 km and lifted a confined bubble of smoke and moisture to 35 km altitude. Its evolution was tracked by several satellite-based sensors and was successfully resolved by the European Centre for Medium-Range Weather Forecasts operational system, primarily based on satellite data. Because wildfires are expected to increase in frequency and strength in a changing climate, we suggest that extraordinary events of this type may contribute significantly to the global stratospheric composition in the coming decades.
The 2019/2020 Australian wildfires generated a smoke cloud that organized itself into a persistent vortex structure and ascended to 35 km altitude through solar heating, according to satellite tracking.
The Nabro stratovolcano in Eritrea, northeastern Africa, erupted on 13 June 2011, injecting approximately 1.3 teragrams of sulfur dioxide (SO 2 ) to altitudes of 9 to 14 kilometers in the upper ...troposphere, which resulted in a large aerosol enhancement in the stratosphere. The SO 2 was lofted into the lower stratosphere by deep convection and the circulation associated with the Asian summer monsoon while gradually converting to sulfate aerosol. This demonstrates that to affect climate, volcanic eruptions need not be strong enough to inject sulfur directly to the stratosphere.
Ozone forms in the Earth's atmosphere from the photodissociation of molecular oxygen, primarily in the tropical stratosphere. It is then transported to the extratropics by the Brewer-Dobson ...circulation (BDC), forming a protective "ozone layer" around the globe. Human emissions of halogen-containing ozone-depleting substances (hODSs) led to a decline in stratospheric ozone until they were banned by the Montreal Protocol, and since 1998 ozone in the upper stratosphere is rising again, likely the recovery from halogen-induced losses. Total column measurements of ozone between the Earth's surface and the top of the atmosphere indicate that the ozone layer has stopped declining across the globe, but no clear increase has been observed at latitudes between 60degS and 60degN outside the polar regions (60-90deg). Here we report evidence from multiple satellite measurements that ozone in the lower stratosphere between 60degS and 60degN has indeed continued to decline since 1998. We find that, even though upper stratospheric ozone is recovering, the continuing downward trend in the lower stratosphere prevails, resulting in a downward trend in stratospheric column ozone between 60degS and 60degN. We find that total column ozone between 60degS and 60degN appears not to have decreased only because of increases in tropospheric column ozone that compensate for the stratospheric decreases. The reasons for the continued reduction of lower stratospheric ozone are not clear; models do not reproduce these trends, and thus the causes now urgently need to be established.
Interest in stratospheric aerosol and its role in climate have increased over the last decade due to the observed increase in stratospheric aerosol since 2000 and the potential for changes in the ...sulfur cycle induced by climate change. This review provides an overview about the advances in stratospheric aerosol research since the last comprehensive assessment of stratospheric aerosol was published in 2006. A crucial development since 2006 is the substantial improvement in the agreement between in situ and space-based inferences of stratospheric aerosol properties during volcanically quiescent periods. Furthermore, new measurement systems and techniques, both in situ and space based, have been developed for measuring physical aerosol properties with greater accuracy and for characterizing aerosol composition. However, these changes induce challenges to constructing a long-term stratospheric aerosol climatology. Currently, changes in stratospheric aerosol levels less than 20% cannot be confidently quantified. The volcanic signals tend to mask any nonvolcanically driven change, making them difficult to understand. While the role of carbonyl sulfide as a substantial and relatively constant source of stratospheric sulfur has been confirmed by new observations and model simulations, large uncertainties remain with respect to the contribution from anthropogenic sulfur dioxide emissions. New evidence has been provided that stratospheric aerosol can also contain small amounts of nonsulfatematter such as black carbon and organics. Chemistry-climate models have substantially increased in quantity and sophistication. In many models the implementation of stratospheric aerosol processes is coupled to radiation and/or stratospheric chemistry modules to account for relevant feedback processes.
We describe the construction of a continuous 38-year record of stratospheric
aerosol optical properties. The Global Space-based Stratospheric Aerosol
Climatology, or GloSSAC, provided the input data ...to the construction of the
Climate Model Intercomparison Project stratospheric aerosol forcing data set
(1979–2014) and we have extended it through 2016 following an identical
process. GloSSAC focuses on the Stratospheric Aerosol and Gas Experiment
(SAGE) series of instruments through mid-2005, and on the Optical
Spectrograph and InfraRed Imager System (OSIRIS) and the Cloud-Aerosol Lidar
and Infrared Pathfinder Satellite Observation (CALIPSO) data thereafter. We
also use data from other space instruments and from ground-based, air, and
balloon borne instruments to fill in key gaps in the data set. The end result
is a global and gap-free data set focused on aerosol extinction coefficient
at 525 and 1020 nm and other parameters on an “as available” basis. For
the primary data sets, we developed a new method for filling the
post-Pinatubo eruption data gap for 1991–1993 based on data from the
Cryogenic Limb Array Etalon Spectrometer. In addition, we developed a new
method for populating wintertime high latitudes during the SAGE period
employing a latitude-equivalent latitude conversion process that greatly
improves the depiction of aerosol at high latitudes compared to earlier
similar efforts. We report data in the troposphere only when and where it is
available. This is primarily during the SAGE II period except for the most
enhanced part of the Pinatubo period. It is likely that the upper troposphere
during Pinatubo was greatly enhanced over non-volcanic periods and that
domain remains substantially under-characterized. We note that aerosol levels
during the OSIRIS/CALIPSO period in the lower stratosphere at mid- and high
latitudes is routinely higher than what we observed during the SAGE II
period. While this period had nearly continuous low-level volcanic activity,
it is possible that the enhancement in part reflects deficiencies in the data
set. We also expended substantial effort to quality assess the data set and
the product is by far the best we have produced. GloSSAC version 1.0 is
available in netCDF format at the NASA Atmospheric Data Center at
https://eosweb.larc.nasa.gov/. GloSSAC users should cite this paper and
the data set DOI (https://doi.org/10.5067/GloSSAC-L3-V1.0).
Stratospheric aerosols play a key role in atmospheric chemistry and climate. Their particle size is a crucial factor controlling the microphysical, radiative, and chemical aerosol processes in the ...stratosphere. Despite its importance, available observations on aerosol particle size are rather sparse. This limits our understanding and knowledge about the mechanisms and importance of chemical and climate aerosol feedbacks. The retrieval described by Malinina et al. (2018) provides the stratospheric particle size distribution (PSD) from SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) limb observations in the tropics. This algorithm has now been improved and extended to work on the entire globe. Two PSD parameters of a unimodal lognormal PSD, the median radius and the geometric standard deviation, are retrieved between 18 and 35 km altitude from SCIAMACHY limb observations by a multiwavelength nonlinear regularized inversion. The approach assumes an aerosol particle number density profile that does not change during the retrieval. The effective Lambertian surface albedo pre-retrieved from coinciding SCIAMACHY nadir observations is integrated into the retrieval algorithm to mitigate the influence of the surface albedo on the retrieval results. The extinction coefficient and the effective radius are calculated from the PSD parameters. The aerosol characteristics from SCIAMACHY are compared with in situ balloon-borne measurements from Laramie, Wyoming, and retrievals from the satellite instruments of the Stratospheric Aerosol and Gas Experiment series (SAGE II and SAGE III) and Optical Spectrograph and InfraRed Imager System (OSIRIS). In the Northern Hemisphere, the median radius differs by less than 27 % and the geometric standard deviation by less than 11 % from both balloon-borne and SAGE III data. Differences are mainly attributed to errors in the assumed a priori number density profile. Globally, the SCIAMACHY extinction coefficient at 750 nm deviates by less than 35 % from SAGE II, SAGE III, and OSIRIS data. The effective radii from SCIAMACHY, balloon-borne measurements, and SAGE III agree within about 18 %, while the effective radius based on SAGE II measurements is systematically larger. The novel data set containing the PSD parameters, the effective radius, and the aerosol extinction coefficients at 525, 750, and 1020 nm from SCIAMACHY observations is publicly available.
Measurements of limb-scattered sunlight from the Ozone Mapping and Profiler Suite Limb Profiler (OMPS-LP) can be used to
obtain vertical profiles of ozone in the stratosphere. In this paper we ...describe a two-dimensional, or tomographic,
retrieval algorithm for OMPS-LP where variations are retrieved simultaneously in altitude and the along-orbital-track
dimension. The algorithm has been applied to measurements from the center slit for the full OMPS-LP mission to create the
publicly available University of Saskatchewan (USask) OMPS-LP 2D v1.0.2 dataset. Tropical ozone anomalies are compared with measurements from the
Microwave Limb Sounder (MLS), where differences are less than 5 % of the mean ozone value for the majority of the
stratosphere. Examples of near-coincident measurements with MLS are also shown, and agreement at the 5 % level is
observed for the majority of the stratosphere. Both simulated retrievals and coincident comparisons with MLS are shown at
the edge of the polar vortex, comparing the results to a traditional one-dimensional retrieval. The one-dimensional
retrieval is shown to consistently overestimate the amount of ozone in areas of large horizontal gradients relative to
both MLS and the two-dimensional retrieval.
The Stratospheric Aerosol and Gas Experiment
(SAGE) III has been operating on the International Space
Station (ISS) since mid-2017. Nitrogen dioxide (NO2) number
density profiles are routinely ...retrieved from SAGE
III/ISS solar occultation measurements in the middle atmosphere.
Although NO2 density varies throughout the day due
to photochemistry, the standard SAGE NO2 retrieval algorithm
neglects these variations along the instrument’s line of
sight by assuming that the number density has a constant gradient
within a given vertical layer of the atmosphere. This assumption
will result in a retrieval bias for a species like NO2
that changes rapidly across the terminator. In this work we
account for diurnal variations in retrievals of NO2 from the
SAGE III/ISS measurements, and we determine the impact
of this algorithm improvement on the resulting NO2 number
densities. The first step in applying the diurnal correction is
to use publicly available SAGE III/ISS products to convert
the retrieved number density profiles to optical depth profiles.
The retrieval is then re-performed with a new matrix
that applies photochemical scale factors for each point along
the line of sight according to the changing solar zenith angle.
In general NO2 that is retrieved by accounting for these
diurnal variations is more than 10% lower than the standard
algorithm below 30 km. This effect is greatest in winter at
high latitudes and generally greater for sunrise occultations
than sunset. Comparisons with coincident profiles from the
Optical Spectrograph and InfraRed Imager System (OSIRIS)
show that NO2 from SAGE III/ISS is generally biased high;
however the agreement improves by up to 20% in the mid-stratosphere
when diurnal variations are accounted for in
the retrieval. We conclude that diurnal variations along the
SAGE III/ISS line of sight are an important term to consider
for NO2 analyses at altitudes below 30 km.
The article presents new high-quality continuous stratospheric aerosol observations spanning 1994–2015 at the French Observatoire de Haute-Provence (OHP, 44° N, 6° E) obtained by two independent, ...regularly maintained lidar systems operating within the Network for Detection of Atmospheric Composition Change (NDACC). Lidar series are compared with global-coverage observations by Stratospheric Aerosol and Gas Experiment (SAGE II), Global Ozone Monitoring by Occultation of Stars (GOMOS), Optical Spectrograph and InfraRed Imaging System (OSIRIS), Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP), and Ozone Mapping Profiling Suite (OMPS) satellite instruments, altogether covering the time span of OHP lidar measurements. Local OHP and zonal-mean satellite series of stratospheric aerosol optical depth are in excellent agreement, allowing for accurate characterization of stratospheric aerosol evolution and variability at northern midlatitudes during the last 2 decades. The combination of local and global observations is used for a careful separation between volcanically perturbed and quiescent periods. While the volcanic signatures dominate the stratospheric aerosol record, the background aerosol abundance is found to be modulated remotely by the poleward transport of convectively cleansed air from the deep tropics and aerosol-laden air from the Asian monsoon region. The annual cycle of background aerosol at midlatitudes, featuring a minimum during late spring and a maximum during late summer, correlates with that of water vapor from the Aura Microwave Limb Sounder (MLS). Observations covering two volcanically quiescent periods over the last 2 decades provide an indication of a growth in the nonvolcanic component of stratospheric aerosol. A statistically significant factor of 2 increase in nonvolcanic aerosol since 1998, seasonally restricted to late summer and fall, is associated with the influence of the Asian monsoon and growing pollution therein.
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