Gabriel Chiodo

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Chiodo

First Name

Gabriel

ORCID

0000-0002-8079-6314

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Publications 1 - 10 of 43

Tropospheric links to uncertainty in stratospheric subseasonal predictions
Wu, Rachel Wai-Ying; Chiodo, Gabriel; Polichtchouk, Inna; et al. (2024)
Atmospheric Chemistry and Physics
Variability in the stratosphere, especially extreme events such as sudden stratospheric warmings (SSWs), can impact surface weather. Understanding stratospheric prediction uncertainty is therefore crucial for skillful surface weather forecasts on weekly to monthly timescales. Using ECMWF subseasonal hindcasts, this study finds that stratospheric uncertainty is most strongly linked to tropospheric uncertainty over the North Pacific and Northern Europe, regions that can modulate but also respond to stratospheric variability, suggesting a two-way propagation of uncertainty. A case study of the 2018 SSW event shows an initial poleward and upward propagation of uncertainty from tropical convection, followed by a downward propagation where ensemble members that accurately predict the SSW are also better at predicting its downward impacts. These findings highlight the locations in the troposphere that are linked to stratospheric uncertainty and suggest that improved model representation of tropospheric mechanisms linked to polar vortex variability could enhance both stratospheric and extratropical surface prediction.
Near-future rocket launches could slow ozone recovery
Revell, Laura E.; Bannister, Michele T.; Brown, Tyler F.M.; et al. (2025)
npj Climate and Atmospheric Science
Rocket emissions thin the stratospheric ozone layer. To understand if significant ozone losses could occur as the launch industry grows, we examine two scenarios. Our 'ambitious' scenario (2040 launches/year) yields a -0.29% depletion in annual-mean, near-global total column ozone in 2030. Antarctic springtime ozone decreases by 3.9%. Our 'conservative' scenario (884 launches/year) yields -0.17% annual, near-global depletion; current licensing rates suggest this scenario may be exceeded before 2030. Ozone losses are driven by the chlorine produced from solid rocket motor propellant, and black carbon which is emitted from most propellants. The ozone layer is slowly healing from the effects of CFCs, yet global-mean ozone abundances are still 2% lower than measured prior to the onset of CFC-induced ozone depletion. Our results demonstrate that ongoing and frequent rocket launches could delay ozone recovery. Action is needed now to ensure that future growth of the launch industry and ozone protection are mutually sustainable.
Exploring the link between austral stratospheric polar vortex anomalies and surface climate in chemistry-climate models
Bergner, Nora; Friedel, Marina; Domeisen, Daniela; et al. (2022)
Atmospheric Chemistry and Physics
Extreme events in the stratospheric polar vortex can lead to changes in the tropospheric circulation and impact the surface climate on a wide range of timescales. The austral stratospheric vortex shows its largest variability in spring, and a weakened polar vortex is associated with changes in the spring to summer surface climate, including hot and dry extremes in Australia. However, the robustness and extent of the connection between polar vortex strength and surface climate on interannual timescales remain unclear. We assess this relationship by using reanalysis data and time-slice simulations from two chemistry-climate models (CCMs), building on previous work that is mainly based on observations. The CCMs show a similar downward propagation of anomalies in the polar vortex strength to the reanalysis data: a weak polar vortex is on average followed by a negative tropospheric Southern Annular Mode (SAM) in spring to summer, while a strong polar vortex is on average followed by a positive SAM. The signature in the surface climate following polar vortex weakenings is characterized by high surface pressure and warm temperature anomalies over Antarctica, the region where surface signals are most robust across all model and observational datasets. However, the tropospheric SAM response in the two CCMs considered is inconsistent with observations. In one CCM, the SAM is more negative compared to the reanalysis after weak polar vortex events, whereas in the other CCM, it is less negative. In addition, neither model reproduces all the regional changes in midlatitudes, such as the warm and dry anomalies over Australia. We find that these inconsistencies are linked to model biases in the basic state, such as the latitude of the eddy-driven jet and the persistence of the SAM. These results are largely corroborated by models that participated in the Chemistry-Climate Model Initiative (CCMI). Furthermore, bootstrapping of the data reveals sizable uncertainty in the magnitude of the surface signals in both models and observations due to internal variability. Our results demonstrate that anomalies of the austral stratospheric vortex have significant impacts on surface climate, although the ability of models to capture regional effects across the Southern Hemisphere is limited by biases in their representation of the stratospheric and tropospheric circulation.
Separating and quantifying the distinct impacts of El Niño and sudden stratospheric warmings on North Atlantic and Eurasian wintertime climate
Oehrlein, Jessica; Chiodo, Gabriel; Polvani, Lorenzo M. (2019)
Atmospheric Science Letters
Sudden stratospheric warmings (SSWs) significantly influence Eurasian wintertime climate. The El Niño phase of the El Niño–Southern Oscillation (ENSO) also affects climate in that region through tropospheric and stratospheric pathways, including increased SSW frequency. However, most SSWs are unrelated to El Niño, and their importance compared to other El Niño pathways remains to be quantified. We here contrast these two sources of variability using two 200‐member ensembles of 1‐year integrations of the Whole Atmosphere Community Climate Model, one ensemble with prescribed El Niño sea surface temperatures (SSTs) and one with neutral‐ENSO SSTs. We form composites of wintertime climate anomalies, with and without SSWs, in each ensemble and contrast them to a basic state represented by neutral‐ENSO winters without SSWs. We find that El Niño and SSWs both result in negative North Atlantic Oscillation anomalies and have comparable impacts on European precipitation, but SSWs cause larger Eurasian cooling. Our results have implications for predictability of wintertime Eurasian climate.
Stronger Arctic amplification from ozone-depleting substances than from carbon dioxide
Liang, Yu-Chiao; Polvani, Lorenzo M.; Previdi, Michael; et al. (2022)
Environmental Research Letters
Arctic amplification (AA)-the greater warming of the Arctic near-surface temperature relative to its global mean value-is a prominent feature of the climate response to increasing greenhouse gases. Recent work has revealed the importance of ozone-depleting substances (ODS) in contributing to Arctic warming and sea-ice loss. Here, using ensembles of climate model integrations, we expand on that work and directly contrast Arctic warming from ODS to that from carbon dioxide (CO2), over the 1955-2005 period when ODS loading peaked. We find that the Arctic warming and sea-ice loss from ODS are slightly more than half (52%-59%) those from CO2. We further show that the strength of AA for ODS is 1.44 times larger than that for CO2, and that this mainly stems from more positive Planck, albedo, lapse-rate, and cloud feedbacks. Our results suggest that AA would be considerably stronger than presently observed had the Montreal Protocol not been signed.
The influence of future changes in springtime Arctic ozone on stratospheric and surface climate
Chiodo, Gabriel; Friedel, Marina; Seeber, Svenja; et al. (2023)
Atmospheric Chemistry and Physics
Stratospheric ozone is expected to recover by the mid-century due to the success of the Montreal Protocol in regulating the emission of ozone-depleting substances (ODSs). In the Arctic, ozone abundances are projected to surpass historical levels due to the combined effect of decreasing ODSs and elevated greenhouse gases (GHGs). While long-term changes in stratospheric ozone have been shown to be a major driver of future surface climate in the Southern Hemisphere during summertime, the dynamical and climatic impacts of elevated ozone levels in the Arctic have not been investigated. In this study, we use two chemistry climate models (the SOlar Climate Ozone Links - Max Planck Ocean Model (SOCOL-MPIOM) and the Community Earth System Model - Whole Atmosphere Community Climate Model (CESM-WACCM)) to assess the climatic impacts of future changes in Arctic ozone on stratospheric dynamics and surface climate in the Northern Hemisphere (NH) during the 21st century. Under the high-emission scenario (RCP8.5) examined in this work, Arctic ozone returns to pre-industrial levels by the middle of the century. Thereby, the increase in Arctic ozone in this scenario warms the lower Arctic stratosphere; reduces the strength of the polar vortex, advancing its breakdown; and weakens the Brewer-Dobson circulation. The ozone-induced changes in springtime generally oppose the effects of GHGs on the polar vortex. In the troposphere, future changes in Arctic ozone induce a negative phase of the Arctic Oscillation, pushing the jet equatorward over the North Atlantic. These impacts of future ozone changes on NH surface climate are smaller than the effects of GHGs, but they are remarkably robust among the two models employed in this study, canceling out a portion of the GHG effects (up to 20% over the Arctic). In the stratosphere, Arctic ozone changes cancel out a much larger fraction of the GHG-induced signal (up to 50 %- 100 %), resulting in no overall change in the projected springtime stratospheric northern annular mode and a reduction in the GHG-induced delay of vortex breakdown of around 15 d. Taken together, our results indicate that future changes in Arctic ozone actively shape the projected changes in the stratospheric circulation and their coupling to the troposphere, thereby playing an important and previously unrecognized role as a driver of the large-scale atmospheric circulation response to climate change.
Substantial twentieth-century Arctic warming caused by ozone-depleting substances
Polvani, Lorenzo M.; Previdi, Michael; England, Mark R.; et al. (2020)
Nature Climate Change
REtrieval Method for optical and physical Aerosol Properties in the stratosphere (REMAPv1)
Jörimann, Andrin; Sukhodolov, Timofei; Luo, Beiping; et al. (2025)
Geoscientific Model Development
Stratospheric aerosol is an important climate forcing agent as it scatters some of the incoming solar radiation back to space, thus cooling the Earth's surface and the troposphere. At the same time, it absorbs some of the upwelling terrestrial radiation that heats the stratosphere. It also plays an important role in stratospheric ozone chemistry by hosting heterogeneous reactions. Major volcanic eruptions can cause strong perturbations of stratospheric aerosol, changing its radiative and chemical effects by more than an order of magnitude. Many global climate models require prescribed stratospheric aerosol as input to properly simulate both climate effects in the presence and absence of volcanic eruptions. This paper describes REMAP, a retrieval method and code for aerosol properties that has been used in several model intercomparison projects (under the name Stratospheric Aerosol and Gas Experiment-3λ, SAGE-3λ). The code fits a single-mode lognormal size distribution for a pure aqueous sulfuric acid aerosol to aerosol extinction coefficients from observational or model data sets. From the retrieved size distribution parameters, the code calculates the effective radius; surface area density; and extinction coefficients, single-scattering albedos, and asymmetry factors of the aerosol within the wavelength bands specified for each individual climate model. We validate REMAP using balloon-borne observations after the Mount Pinatubo and Hunga Tonga-Hunga Ha'apai (HTHH) volcanic eruptions, as well as 4 decades of lidar measurements. Within the constraints of a single-mode lognormal distribution, REMAP generates realistic effective radii and surface area densities after volcanic eruptions and generally matches the lidar backscatter time series within measurement uncertainty. Deviations in aerosol backscatter by up to a factor of 2 arise when (non-volcanic) tropospheric intrusions (e.g., from wildfires) are present and the size distribution deviates significantly from the single-mode lognormal type. We describe the products that have been used in CCMI (Chemistry-Climate Model Initiative), CMIP6 (Coupled Model Intercomparison Project Phase 6 ), and other model intercomparison projects and provide practical instructions for use of the code in future applications.
Solar signals in CMIP‐5 simulations: the stratospheric pathway
Mitchell, Daniel M.; Misios, Stergios; Gray, Lesley; et al. (2015)
Quarterly Journal of the Royal Meteorological Society
The 11 year solar‐cycle component of climate variability is assessed in historical simulations of models taken from the Coupled Model Intercomparison Project, phase 5 (CMIP‐5). Multiple linear regression is applied to estimate the zonal temperature, wind and annular mode responses to a typical solar cycle, with a focus on both the stratosphere and the stratospheric influence on the surface over the period ∼1850–2005. The analysis is performed on all CMIP‐5 models but focuses on the 13 CMIP‐5 models that resolve the stratosphere (high‐top models) and compares the simulated solar cycle signature with reanalysis data. The 11 year solar cycle component of climate variability is found to be weaker in terms of magnitude and latitudinal gradient around the stratopause in the models than in the reanalysis. The peak in temperature in the lower equatorial stratosphere (∼70 hPa) reported in some studies is found in the models to depend on the length of the analysis period, with the last 30 years yielding the strongest response. A modification of the Polar Jet Oscillation (PJO) in response to the 11 year solar cycle is not robust across all models, but is more apparent in models with high spectral resolution in the short‐wave region. The PJO evolution is slower in these models, leading to a stronger response during February, whereas observations indicate it to be weaker. In early winter, the magnitude of the modelled response is more consistent with observations when only data from 1979–2005 are considered. The observed North Pacific high‐pressure surface response during the solar maximum is only simulated in some models, for which there are no distinguishing model characteristics. The lagged North Atlantic surface response is reproduced in both high‐ and low‐top models, but is more prevalent in the former. In both cases, the magnitude of the response is generally lower than in observations.
Stratospheric injection of solid particles reduces side effects on circulation and climate compared to SO2 injections
Stefanetti, Fabrice; Vattioni, Sandro; Dykema, John A.; et al. (2024)
Environmental Research: Climate
Most research of stratospheric aerosol injection (SAI) for solar radiation modification has focused on injection of SO₂. However, the resulting sulfuric acid aerosols lead to considerable absorption of terrestrial infrared radiation, resulting in stratospheric warming and reduced cooling efficiency. Recent research suggests that solid particles, such as alumina, calcite or diamond, could minimize these side effects. Here we use, for the first time, the atmosphere-ocean-aerosol-chemistry-climate model SOCOLv4.0, incorporating a solid particle scheme, to assess the climatic impacts of SAI by these injection materials. For each substance, we model tropical SAI by means of constant yearly injection of solid particles, aimed to offset the warming induced by a high-GHG emission scenario over the 2020-2100 period by 1 K. We show that solid particles are more effective than sulfur at minimising stratospheric heating, and the resulting side-effects on the general atmospheric circulation, stratospheric moistening, and tropopause height change. As a result, solid particles also induce less residual warming over the arctic, resulting in greater reduction of GHG-induced polar amplification compared to sulfuric acid aerosols. Among the materials studied here, diamond is most efficient in reducing global warming per unit injection, while also minimizing side effects.

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