scholarly journals The impact of volcanic aerosol on the Northern Hemisphere stratospheric polar vortex: mechanisms and sensitivity to forcing structure

2014 ◽  
Vol 14 (23) ◽  
pp. 13063-13079 ◽  
Author(s):  
M. Toohey ◽  
K. Krüger ◽  
M. Bittner ◽  
C. Timmreck ◽  
H. Schmidt
Keyword(s):  
Northern Hemisphere ◽  
High Latitude ◽  
Climate Model ◽  
Polar Vortex ◽  
Volcanic Aerosol ◽  
Stratospheric Polar Vortex ◽  
Model Simulations ◽  
Aerosol Forcing ◽  
Climate Model Simulations ◽  
The Impact

Abstract. Observations and simple theoretical arguments suggest that the Northern Hemisphere (NH) stratospheric polar vortex is stronger in winters following major volcanic eruptions. However, recent studies show that climate models forced by prescribed volcanic aerosol fields fail to reproduce this effect. We investigate the impact of volcanic aerosol forcing on stratospheric dynamics, including the strength of the NH polar vortex, in ensemble simulations with the Max Planck Institute Earth System Model. The model is forced by four different prescribed forcing sets representing the radiative properties of stratospheric aerosol following the 1991 eruption of Mt. Pinatubo: two forcing sets are based on observations, and are commonly used in climate model simulations, and two forcing sets are constructed based on coupled aerosol–climate model simulations. For all forcings, we find that simulated temperature and zonal wind anomalies in the NH high latitudes are not directly impacted by anomalous volcanic aerosol heating. Instead, high-latitude effects result from enhancements in stratospheric residual circulation, which in turn result, at least in part, from enhanced stratospheric wave activity. High-latitude effects are therefore much less robust than would be expected if they were the direct result of aerosol heating. Both observation-based forcing sets result in insignificant changes in vortex strength. For the model-based forcing sets, the vortex response is found to be sensitive to the structure of the forcing, with one forcing set leading to significant strengthening of the polar vortex in rough agreement with observation-based expectations. Differences in the dynamical response to the forcing sets imply that reproducing the polar vortex responses to past eruptions, or predicting the response to future eruptions, depends on accurate representation of the space–time structure of the volcanic aerosol forcing.

scholarly journals The impact of volcanic aerosol on the Northern Hemisphere stratospheric polar vortex: mechanisms and sensitivity to forcing structure

2014 ◽  
Vol 14 (11) ◽  
pp. 16777-16819
Author(s):  
M. Toohey ◽  
K. Krüger ◽  
M. Bittner ◽  
C. Timmreck ◽  
H. Schmidt
Keyword(s):  
High Latitude ◽  
Climate Model ◽  
Polar Vortex ◽  
Volcanic Aerosol ◽  
Stratospheric Polar Vortex ◽  
Model Simulations ◽  
Aerosol Forcing ◽  
Climate Model Simulations ◽  
The Impact ◽  
Forcing Set

Abstract. Observations and simple theoretical arguments suggest that the Northern Hemisphere (NH) stratospheric polar vortex is stronger in winters following major volcanic eruptions. However, recent studies show that climate models forced by prescribed volcanic aerosol fields fail to reproduce this effect. We investigate the impact of volcanic aerosol forcing on stratospheric dynamics, including the strength of the NH polar vortex, in ensemble simulations with the Max Planck Institute Earth System Model. The model is forced by four different prescribed forcing sets representing the radiative properties of stratospheric aerosol following the 1991 eruption of Mt. Pinatubo: two forcing sets are based on observations, and are commonly used in climate model simulations, and two forcing sets are constructed based on coupled aerosol–climate model simulations. For all forcings, we find that temperature and zonal wind anomalies in the NH high latitudes are not directly impacted by anomalous volcanic aerosol heating. Instead, high latitude effects result from robust enhancements in stratospheric residual circulation, which in turn result, at least in part, from enhanced stratospheric wave activity. High latitude effects are therefore much less robust than would be expected if they were the direct result of aerosol heating. While there is significant ensemble variability in the high latitude response to each aerosol forcing set, the mean response is sensitive to the forcing set used. Significant differences, for example, are found in the NH polar stratosphere temperature and zonal wind response to two different forcing data sets constructed from different versions of SAGE II aerosol observations. Significant strengthening of the polar vortex, in rough agreement with the expected response, is achieved only using aerosol forcing extracted from prior coupled aerosol–climate model simulations. Differences in the dynamical response to the different forcing sets used imply that reproducing the polar vortex responses to past eruptions, or predicting the response to future eruptions, depends on accurate representation of the space-time structure of the volcanic aerosol forcing.

scholarly journals The effect of interactive ozone chemistry on weak and strong stratospheric polar vortex events

2020 ◽  
Author(s):  
Jessica Oehrlein ◽  
Gabriel Chiodo ◽  
Lorenzo M. Polvani
Keyword(s):  
Climate Variability ◽  
Northern Hemisphere ◽  
North Atlantic ◽  
Climate Model ◽  
Stratospheric Ozone ◽  
Polar Vortex ◽  
Late Winter ◽  
Stratospheric Polar Vortex ◽  
Winter Climate ◽  
The Impact

Abstract. Modeling and observational studies have reported effects of stratospheric ozone extremes on Northern Hemisphere spring climate. Recent work has further suggested that the coupling of ozone chemistry and dynamics amplifies the surface response to midwinter sudden stratospheric warmings (SSWs). Here, we study the importance of interactive ozone chemistry in representing the stratospheric polar vortex and Northern Hemisphere winter surface climate variability. We contrast two simulations from the interactive and specified chemistry (and thus ozone) versions of the Whole Atmosphere Community Climate Model, designed to isolate the impact of interactive ozone on polar vortex variability. In particular, we analyze the response with and without interactive chemistry to midwinter SSWs, March SSWs, and strong polar vortex events (SPVs). With interactive chemistry, the stratospheric polar vortex is stronger, and more SPVs occur, but we find little effect on the frequency of midwinter SSWs. At the surface, interactive chemistry results in a pattern resembling a more negative North Atlantic Oscillation following midwinter SSWs, but with little impact on the surface signatures of late winter SSWs and SPVs. These results suggest that including interactive ozone chemistry is important for representing North Atlantic and European winter climate variability.

scholarly journals The effect of interactive ozone chemistry on weak and strong stratospheric polar vortex events

2020 ◽  
Vol 20 (17) ◽  
pp. 10531-10544
Author(s):  
Jessica Oehrlein ◽  
Gabriel Chiodo ◽  
Lorenzo M. Polvani
Keyword(s):  
Climate Variability ◽  
Northern Hemisphere ◽  
North Atlantic ◽  
Climate Model ◽  
Stratospheric Ozone ◽  
Polar Vortex ◽  
Late Winter ◽  
Stratospheric Polar Vortex ◽  
Winter Climate ◽  
The Impact

Abstract. Modeling and observational studies have reported effects of stratospheric ozone extremes on Northern Hemisphere spring climate. Recent work has further suggested that the coupling of ozone chemistry and dynamics amplifies the surface response to midwinter sudden stratospheric warmings (SSWs). Here we study the importance of interactive ozone chemistry in representing the stratospheric polar vortex and Northern Hemisphere winter surface climate variability. We contrast two simulations from the interactive and specified chemistry (and thus ozone) versions of the Whole Atmosphere Community Climate Model, which is designed to isolate the impact of interactive ozone on polar vortex variability. In particular, we analyze the response with and without interactive chemistry to midwinter SSWs, March SSWs, and strong polar vortex events (SPVs). With interactive chemistry, the stratospheric polar vortex is stronger and more SPVs occur, but we find little effect on the frequency of midwinter SSWs. At the surface, interactive chemistry results in a pattern resembling a more negative North Atlantic Oscillation following midwinter SSWs but with little impact on the surface signatures of late winter SSWs and SPVs. These results suggest that including interactive ozone chemistry is important for representing North Atlantic and European winter climate variability.

scholarly journals On the Choice of Ensemble Mean for Estimating the Forced Signal in the Presence of Internal Variability

2018 ◽  
Vol 31 (14) ◽  
pp. 5681-5693 ◽  
Author(s):  
Leela M. Frankcombe ◽  
Matthew H. England ◽  
Jules B. Kajtar ◽  
Michael E. Mann ◽  
Byron A. Steinman
Keyword(s):  
Regional Differences ◽  
Climate Model ◽  
Surface Air Temperature ◽  
Internal Variability ◽  
Single Model ◽  
Sea Level Pressure ◽  
Model Simulations ◽  
Ensemble Mean ◽  
Climate Model Simulations ◽  
The Impact

Abstract In this paper we examine various options for the calculation of the forced signal in climate model simulations, and the impact these choices have on the estimates of internal variability. We find that an ensemble mean of runs from a single climate model [a single model ensemble mean (SMEM)] provides a good estimate of the true forced signal even for models with very few ensemble members. In cases where only a single member is available for a given model, however, the SMEM from other models is in general out-performed by the scaled ensemble mean from all available climate model simulations [the multimodel ensemble mean (MMEM)]. The scaled MMEM may therefore be used as an estimate of the forced signal for observations. The MMEM method, however, leads to increasing errors further into the future, as the different rates of warming in the models causes their trajectories to diverge. We therefore apply the SMEM method to those models with a sufficient number of ensemble members to estimate the change in the amplitude of internal variability under a future forcing scenario. In line with previous results, we find that on average the surface air temperature variability decreases at higher latitudes, particularly over the ocean along the sea ice margins, while variability in precipitation increases on average, particularly at high latitudes. Variability in sea level pressure decreases on average in the Southern Hemisphere, while in the Northern Hemisphere there are regional differences.

scholarly journals Enhanced Seasonal Prediction of European Winter Warming following Volcanic Eruptions

2009 ◽  
Vol 22 (23) ◽  
pp. 6168-6180 ◽  
Author(s):  
A. G. Marshall ◽  
A. A. Scaife ◽  
S. Ineson
Keyword(s):  
Climate Model ◽  
Initial Conditions ◽  
Polar Vortex ◽  
Volcanic Eruptions ◽  
Seasonal Prediction ◽  
The Arctic ◽  
Extended Model ◽  
Similar Response ◽  
Volcanic Aerosol ◽  
The Impact

Abstract The impact of explosive volcanic eruptions on the atmospheric circulation at high northern latitudes is assessed in two versions of the Met Office Hadley Centre’s atmospheric climate model. The standard version of the model extends to an altitude of around 40 km, while the extended version has enhanced stratospheric resolution and reaches 85-km altitude. Seasonal hindcasts initialized on 1 December produce a strengthening of the winter polar vortex and anomalous warming over northern Europe characteristic of the positive phase of the Arctic Oscillation (AO) when forced with volcanic aerosol following the 1963 Mount Agung, 1982 El Chichón, and 1991 Mount Pinatubo eruptions, as is observed. The AO signal in the extended model is of comparable strength to that in the standard model, showing that there is little impact from both increasing the vertical resolution in the stratosphere and extending the model domain to near the mesopause. The presence of this signal in the models, however, is likely due to the persistence of the observed signal from the initial conditions, because a similar set of experiments initiated with the same conditions, but with no volcanic aerosol forcing, exhibits a similar response as the forced runs. This suggests that the model has limited fidelity in capturing the response to volcanic aerosols on its own, consistent with previous studies on the impact of volcanic forcing in long climate simulations, but does support the premise that seasonal winter forecasts are substantially improved with the inclusion of stratospheric information.

scholarly journals Trends in Downward Solar Radiation at the Surface over North America from Climate Model Projections and Implications for Solar Energy

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Gerardo Andres Saenz ◽  
Huei-Ping Huang
Keyword(s):  
United States ◽  
North America ◽  
Solar Radiation ◽  
Solar Energy ◽  
Climate Model ◽  
Global Climate Model ◽  
The United States ◽  
Model Simulations ◽  
Climate Model Simulations ◽  
The Impact

The projected changes in the downward solar radiation at the surface over North America for late 21st century are deduced from global climate model simulations with greenhouse-gas (GHG) forcing. A robust trend is found in winter over the United States, which exhibits a simple pattern of a decrease of sunlight over Northern USA. and an increase of sunlight over Southern USA. This structure was identified in both the seasonal mean and the mean climatology at different times of the day. It is broadly consistent with the known poleward shift of storm tracks in winter in climate model simulations with GHG forcing. The centennial trend of the downward shortwave radiation at the surface in Northern USA. is on the order of 10% of the climatological value for the January monthly mean, and slightly over 10% at the time when it is midday in the United States. This indicates a nonnegligible influence of the GHG forcing on solar energy in the long term. Nevertheless, when dividing the 10% by a century, in the near term, the impact of the GHG forcing is relatively minor such that the estimate of solar power potential using present-day climatology will remain useful in the coming decades.

scholarly journals The impact of volcanic aerosols on stratospheric ozone and the Northern Hemisphere polar vortex: separating radiative from chemical effects under different climate conditions

2015 ◽  
Vol 15 (10) ◽  
pp. 14275-14314 ◽  
Author(s):  
S. Muthers ◽  
F. Arfeuille ◽  
C. C. Raible ◽  
E. Rozanov
Keyword(s):  
Northern Hemisphere ◽  
Climate Model ◽  
Stratospheric Ozone ◽  
Polar Vortex ◽  
Volcanic Eruptions ◽  
Radiative Heating ◽  
Dynamical Response ◽  
Climate Conditions ◽  
Column Ozone ◽  
The Impact

Abstract. After strong volcanic eruptions stratospheric ozone changes are modulated by heterogeneous chemical reactions (HET) and dynamical perturbations related to the radiative heating in the lower stratosphere (RAD). Here, we assess the relative importance of both processes as well as the effect of the resulting ozone changes on the dynamics using ensemble simulations with the atmosphere–ocean–chemistry–climate model (AOCCM) SOCOL-MPIOM forced by eruptions with different strength. The simulations are performed under present day and preindustrial conditions to investigate changes in the response behaviour. The results show that the HET effect is only relevant under present day conditions and causes a pronounced global reduction of column ozone. These ozone changes further lead to a slight weakening of the Northern Hemisphere (NH) polar vortex during mid-winter. Independent from the climate state the RAD mechanism changes the column ozone pattern with negative anomalies in the tropics and positive anomalies in the mid-latitudes. The influence of the climate state on the RAD mechanism significantly differs in the polar latitudes, where an amplified ozone depletion during the winter months is simulated under present day conditions. This is in contrast to the preindustrial state showing a positive column ozone response also in the polar area. The dynamical response of the stratosphere is clearly dominated by the RAD mechanism showing an intensification of the NH polar vortex in winter. Still under present day conditions ozone changes due to the RAD mechanism slightly reduce the response of the polar vortex after the eruption.

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