Chemical loss of Arctic ozone due to anthropogenic halogens is driven by temperature, with more loss occurring during cold winters favourable for formation of polar stratospheric clouds (PSCs). We ...show that a positive, statistically significant rise in the local maxima of PSC formation potential (PFP
) for cold winters is apparent in meteorological data collected over the past half century. Output from numerous General Circulation Models (GCMs) also exhibits positive trends in PFP
over 1950 to 2100, with highest values occurring at end of century, for simulations driven by a large rise in the radiative forcing of climate from greenhouse gases (GHGs). We combine projections of stratospheric halogen loading and humidity with GCM-based forecasts of temperature to suggest that conditions favourable for large, seasonal loss of Arctic column O
could persist or even worsen until the end of this century, if future abundances of GHGs continue to steeply rise.
Arctic warming was more pronounced than warming in midlatitudes in the last decades making this region a hotspot of climate change. Associated with this, a rapid decline of sea-ice extent and a ...decrease of its thickness has been observed. Sea-ice retreat allows for an increased transport of heat and momentum from the ocean up to the tropo- and stratosphere by enhanced upward propagation of planetary-scale atmospheric waves. In the upper atmosphere, these waves deposit the momentum transported, disturbing the stratospheric polar vortex, which can lead to a breakdown of this circulation with the potential to also significantly impact the troposphere in mid- to late-winter and early spring. Therefore, an accurate representation of stratospheric processes in climate models is necessary to improve the understanding of the impact of retreating sea ice on the atmospheric circulation. By modeling the atmospheric response to a prescribed decline in Arctic sea ice, we show that including interactive stratospheric ozone chemistry in atmospheric model calculations leads to an improvement in tropo-stratospheric interactions compared to simulations without interactive chemistry. This suggests that stratospheric ozone chemistry is important for the understanding of sea ice related impacts on atmospheric dynamics.
The eruption of the Hunga Tonga‐Hunga Ha'apai volcano on 15 January 2022 was one of the most explosive eruptions of the last decades. The amount of water vapor injected into the stratosphere was ...unprecedented in the observational record, increasing the stratospheric water vapor burden by about 10%. Using model runs from the ATLAS chemistry and transport model and Microwave Limb Sounder (MLS) satellite observations, we show that while 20%–40% more water vapor than usual was entrained into the Antarctic polar vortex in 2023 as it formed, the direct chemical effect of the increased water vapor on Antarctic ozone depletion in June through October was minor (less than 4 DU). This is because low temperatures in the vortex, as occur every year in the Antarctic, limit water vapor to the saturation pressure and thus reset any anomalies through the process of dehydration before they can affect ozone loss.
Plain Language Summary
The eruption of the Hunga Tonga‐Hunga Ha'apai volcano on 15 January 2022 was one of the most explosive eruptions of the last decades. An amount of water vapor unprecedented in the observational record was injected into the stratosphere, increasing the total stratospheric water vapor mass by about 10%. Using model runs and satellite observations, we show that while the dispersion of the plume increased water vapor in the Antarctic in 2023 by 20%–40% at the beginning of the ozone hole season compared to earlier years, the effect of the increased water vapor on the Antarctic ozone hole was minor. This is because low temperatures in the vortex, as occur every year in the Antarctic, limit water vapor due to condensation and thus reset any anomalies before they can affect ozone loss.
Key Points
The Hunga Tonga‐Hunga Ha'apai eruption increased water vapor in the emerging Antarctic vortex in 2023 by 20%–40% compared to earlier years
The increased water vapor from Hunga Tonga had a minor effect on Antarctic ozone depletion through the end of October (less than 4 DU)
This minor effect is due to low, but not unusual, vortex temperatures that reset water vapor anomalies before they could impact ozone loss
A set of 44 potential explanatory variables is used for statistical modeling of monthly mean total ozone values of 158 ground‐based stations. A stepwise elimination process leads to zonally optimized ...multiple regression models, which account for approximately 78% of the variance in total ozone in the tropics, 85% south of 60°S and more than 90% in the three remaining zones while only retaining six explanatory variables in the model. In all regions the dynamics appear to dominate ozone variability, which is primarily described by a proxy specifically designed to describe the effects of short‐term isentropic excursions at different altitude levels and the compression/expansion of air connected to convergence/divergence. The influence of equivalent effective stratospheric chlorine (EESC) is also important in all regions, indicating the significant effects of anthropogenic emissions of ozone depleting substances (ODS). In addition to the dynamics and EESC, the influence of volcanic eruptions, represented by the integrated surface area density of stratospheric aerosols (SAD), has the largest impact on total ozone in northern regions. The results of the analysis are less clear in the Southern Hemisphere where only a few long‐enough ozone time series are available.
We present a climatology of the diurnal variation of short‐lived atmospheric compounds, such as ClO, BrO, HO2, and HOCl, as well as longer‐lived species: O3, the hydrogen chloride isotopes H35Cl and ...H37Cl, and HNO3. Measurements were taken by the Superconducting Submillimeter‐wave Limb‐Emission Sounder (SMILES). This spectrally resolving radiometer, with very low observation noise and altitude range from the lower stratosphere to the lower thermosphere (20–100km), was measuring vertical profiles of absorption spectra along a non‐sun‐synchronous orbit, thus observing at all local times. We used the retrieved volume mixing ratio profiles to compile climatologies that are a function of pressure, a horizontal coordinate (latitude or equivalent latitude), and a temporal coordinate (solar zenith angle or local solar time). The main product presented are climatologies with a high resolution of the temporal coordinate (diurnal variation climatologies). In addition, we provide climatologies with a high resolution of the horizontal coordinate (zonal climatologies).The diurnal variation climatologies are based on data periods of 2 months and the zonal climatologies on monthly data periods. Consideration of the SMILES time‐space sampling patterns with respect to the averaging coordinates is a key issue for climatology creation, especially in case of diurnal variation climatologies. Biases induced by inhomogeneous sampling are minimized by carefully choosing the size of averaging bins. The sampling biases of the diurnal variation climatology of ClO and BrO are investigated in a comparison of homogeneously sampled model data versus SMILES‐sampled model data from the stratospheric Lagrangian chemistry and transport model Alfred Wegener Institute Lagrangian Chemisrty/Transport System. In most cases, the relative sampling error is in the range of 0–20%. The strongest impact of sampling biases is found where the species' temporal gradients are strongest (mostly at sunrise and sunset), with a relative error of 60–100%. The SMILES climatology data sets are available via the SMILES data distribution home page.
Key Points
A first diurnal variation climatology for short-lived atmospheric compositions.
Species are O3, HCl, HNO3, ClO, BrO, HOCl, HO2, and temperature.
Treatment of SMILES sampling, including a model study.
The Polar SWIFT model is a fast scheme for calculating the chemistry of stratospheric ozone depletion in the polar vortex in winter. It is intended for use in general circulation models (GCMs) and ...earth system models (ESMs) to enable the simulation of interactions between the ozone layer and climate when a full stratospheric chemistry scheme is computationally too expensive. In addition to the simulation of chemistry, ozone has to be transported in the GCM.
As an alternative to the general schemes for the transport and mixing of tracers in the GCMs, a parameterization of the transport of ozone can be used in order to obtain the total change of ozone as the sum of the change by transport and by chemistry. One of the benefits of this approach is the easy and self-contained coupling to a GCM. Another potential advantage is that a transport parameterization based on reanalysis data and measurements can avoid deficiencies in the representation of transport in the GCMs, such as deficits in the representation of the Brewer–Dobson circulation caused by the gravity wave parameterization. Hence, we present a transport parameterization for the Polar SWIFT model that simulates the change in vortex-averaged ozone by transport in a fast and simple way without the need for a complex transport scheme in the GCM.
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