Dynamical-Chemical Feedbacks in General Circulation Models and Their Influence on Sudden Stratospheric Warming Events

Stratospheric Warming ◽

Stratospheric Polar Vortex ◽

Feedback Mechanisms ◽

Surface Climate ◽

Sudden Stratospheric Warming events (SSWs) are rapid disruptions of the Northern Hemisphere (NH) winter stratospheric polar vortex and represent the largest source of inter-annual variability in the NH winter stratosphere. They have been linked to winter surface climate anomalies such as cold snaps over North America and Eurasia. Representing these events accurately in large scale GCMs as well as developing a greater understanding of them is key to improving predictability of winter surface climate. A key component of a GCM is its representation of atmospheric chemistry. Chemical distributions are either prescribed or calculated interactively by coupling an atmospheric chemistry model to radiation and dynamical components, thus capturing any chemical dynamical feedback mechanisms but incurring significant running cost.This work evaluates the impact of interactive chemistry when modelling SSW events and explores the feedback mechanisms between chemical distributions and stratospheric dynamical variability. Pre-industrial control runs from the MetOffice HadGEMGC3.1 model which prescribes chemical fields and UKESM1 which calculates trace gas concentration interactively are utilised. Over the whole season - The Earth System Model appears to suppress warmings while the model with prescribed physics overestimates their occurrence compared to reanalysis. The differing representation of the equatorial stratosphere appears to be partially responsible for this difference. Additionally we find that middle stratosphere equatorial ozone concentration in late NH summer is closely associated with SSW probability in the ensuing winter in UKESM1. Anomalously low ozone is generally associated with an elevated SSW rate. This implies a chemical-dynamical coupling between the equator and the vortex in this model which preliminary results suggest could be driven by chemical feedbacks influencing the state of the early winter Quasi Biennial Oscillation (QBO) and Semi-Annual Oscillation (SAO) in zonal winds which can alter the distribution of planetary wave propagation and breaking (the primary cause of SSWs). Further work will assess whether this phenomenon is observed in other GCMs and further explore the physical mechanisms responsible.

The Effect of a Well-Resolved Stratosphere on Surface Climate: Differences between CMIP5 Simulations with High and Low Top Versions of the Met Office Climate Model

Journal of Climate ◽

10.1175/jcli-d-11-00579.1 ◽

2012 ◽

Vol 25 (20) ◽

pp. 7083-7099 ◽

Cited By ~ 44

Author(s):

S. C. Hardiman ◽

N. Butchart ◽

T. J. Hinton ◽

S. M. Osprey ◽

L. J. Gray

Keyword(s):

General Circulation ◽

Climate Model ◽

Southern Oscillation ◽

Coupled Model ◽

Circulation Model ◽

Climate Simulation ◽

Reanalysis Dataset ◽

Surface Climate ◽

Abstract The importance of using a general circulation model that includes a well-resolved stratosphere for climate simulations, and particularly the influence this has on surface climate, is investigated. High top model simulations are run with the Met Office Unified Model for the Coupled Model Intercomparison Project Phase 5 (CMIP5). These simulations are compared to equivalent simulations run using a low top model differing only in vertical extent and vertical resolution above 15 km. The period 1960–2002 is analyzed and compared to observations and the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis dataset. Long-term climatology, variability, and trends in surface temperature and sea ice, along with the variability of the annular mode index, are found to be insensitive to the addition of a well-resolved stratosphere. The inclusion of a well-resolved stratosphere, however, does improve the impact of atmospheric teleconnections on surface climate, in particular the response to El Niño–Southern Oscillation, the quasi-biennial oscillation, and midwinter stratospheric sudden warmings (i.e., zonal mean wind reversals in the middle stratosphere). Thus, including a well-represented stratosphere could improve climate simulation on intraseasonal to interannual time scales.

Differing responses of the QBO to SO2 injections in two global models

10.5194/acp-2020-206 ◽

2020 ◽

Author(s):

Ulrike Niemeier ◽

Jadwiga H. Richter ◽

Simone Tilmes

Keyword(s):

General Circulation ◽

Climate Model ◽

Numerical Models ◽

Injection Rate ◽

Equatorial Region ◽

Vertical Advection ◽

Model Studies ◽

Abstract. Artificial injections of sulfur dioxide (SO2) into the stratosphere show in several model studies an impact on stratospheric dynamics. The quasi-biennial oscillation (QBO) has been shown to slow down or even vanish, under higher SO2 injections in the equatorial region. But the impact is only qualitatively, but not quantitatively consistent across the different studies using different numerical models. The aim of this study is to understand the reasons behind the differences in the QBO response to SO2 injections between two general circulation models, the Whole Atmosphere Community Climate Model (WACCM-110L) and MAECHAM5-HAM. We show that the response of the QBO to injections with the same SO2 injection rate is very different in the two models, but similar when a similar stratospheric heating rate is induced by SO2 injections of different amounts. The reason for the different response of the QBO corresponding to the same injection rate is very different vertical advection in the two models, even in the control simulation. The stronger vertical advection in WACCM results in a higher aerosol burden and stronger heating of the aerosols, and, consequently in a vanishing QBO at lower injection rate than in simulations with MAECHAM5-HAM.

Differing responses of the quasi-biennial oscillation to artificial SO2 injections in two global models

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-8975-2020 ◽

2020 ◽

Vol 20 (14) ◽

pp. 8975-8987

Author(s):

Ulrike Niemeier ◽

Jadwiga H. Richter ◽

Simone Tilmes

Keyword(s):

General Circulation ◽

Climate Model ◽

Numerical Models ◽

Horizontal Resolution ◽

Injection Rate ◽

Vertical Advection ◽

The Impact ◽

Biennial Oscillation

Abstract. Artificial injections of sulfur dioxide (SO2) into the stratosphere show in several model studies an impact on stratospheric dynamics. The quasi-biennial oscillation (QBO) has been shown to slow down or even vanish under higher SO2 injections in the equatorial region. But the impact is only qualitatively but not quantitatively consistent across the different studies using different numerical models. The aim of this study is to understand the reasons behind the differences in the QBO response to SO2 injections between two general circulation models, the Whole Atmosphere Community Climate Model (WACCM-110L) and MAECHAM5-HAM. We show that the response of the QBO to injections with the same SO2 injection rate is very different in the two models, but similar when a similar stratospheric heating rate is induced by SO2 injections of different amounts. The reason for the different response of the QBO corresponding to the same injection rate is very different vertical advection in the two models, even in the control simulation. The stronger vertical advection in WACCM results in a higher aerosol burden and stronger heating of the aerosols and, consequently, in a vanishing QBO at lower injection rate than in simulations with MAECHAM5-HAM. The vertical velocity increases slightly in MAECHAM5-HAM when increasing the horizontal resolution. This study highlights the crucial role of dynamical processes and helps to understand the large uncertainties in the response of different models to artificial SO2 injections in climate engineering studies.

Stratospheric warming influence on the mesosphere/lower thermosphere as seen by the extended CMAM

Annales Geophysicae ◽

10.5194/angeo-32-589-2014 ◽

2014 ◽

Vol 32 (6) ◽

pp. 589-608 ◽

Cited By ~ 18

Author(s):

M. G. Shepherd ◽

S. R. Beagley ◽

V. I. Fomichev

Keyword(s):

Atmospheric Chemistry ◽

Middle Atmosphere ◽

Lower Thermosphere ◽

Lower Atmosphere ◽

Fourier Transform Spectrometer ◽

Stratospheric Warming ◽

New Information ◽

The Impact ◽

Chemistry Experiment

Abstract. The response of the upper mesosphere/lower thermosphere region to major sudden stratospheric warming (SSW) is examined employing temperature, winds, NOX and CO constituents from the extended Canadian Middle Atmosphere Model (CMAM) with continuous incremental nudging below 10 hPa (~ 30 km). The model results considered cover high latitudes (60–85° N) from 10 to 150 km height for the December–March period of 2003/2004, 2005/2006 and 2008/2009, when some of the strongest SSWs in recent years were observed. NOX and CO are used as proxies for examining transport. Comparisons with ACE-FTS (Atmospheric Chemistry Experiment–Fourier Transform Spectrometer) satellite observations show that the model represents well the dynamics of the upper mesosphere/lower thermosphere region, the coupling of the stratosphere–mesosphere, and the NOX and CO transport. New information is obtained on the upper mesosphere/lower thermosphere up to 150 km showing that the NOX volume mixing ratio in the 2003/2004 winter was very perturbed indicating transport from the lower atmosphere and intense mixing with large NOX influx from the thermosphere compared to 2006 and 2009. These results, together with those from other models and observations, clearly show the impact of stratospheric warmings on the thermosphere.

The Influence of Ocean Thermocline Temperatures on the Earth’s Surface Climate

Journal of Climate ◽

10.1175/jcli3382.1 ◽

2005 ◽

Vol 18 (13) ◽

pp. 2222-2246 ◽

Cited By ~ 2

Author(s):

Robert J. Oglesby ◽

Monica Y. Stephens ◽

Barry Saltzman

Keyword(s):

Carbon Dioxide ◽

Mixed Layer ◽

General Circulation ◽

Atmospheric Carbon Dioxide ◽

Deep Ocean ◽

High Latitudes ◽

Surface Climate ◽

Low Latitudes ◽

Atmospheric Carbon ◽

Abstract A coupled mixed layer–atmospheric general circulation model has been used to evaluate the impact of ocean thermocline temperatures (and by proxy those of the deep ocean) on the surface climate of the earth. Particular attention has been devoted to temperature regimes both warmer and cooler than at present. The mixed layer ocean model (MLOM) simulates vertical dynamics and thermodynamics in the upper ocean, including wind mixing and buoyancy effects, and has been coupled to the NCAR Community Climate Model (CCM3). Simulations were made with globally uniform thermocline warmings of +2°, +5°, and +10°C, as well as a globally uniform cooling of −5°C. A simulation was made with latitudinally varying changes in thermocline temperature such that the warming at mid- and high latitudes is much larger than at low latitudes. In all simulations, the response of surface temperature over both land and ocean was larger than that expected just as a result of the imposed thermocline temperature change, largely because of water vapor feedbacks. In this respect, the simulations were similar to those in which only changes in atmospheric carbon dioxide were imposed. In fact, when carbon dioxide was explicitly changed along with thermocline temperatures, the results were not much different than if only the thermocline temperatures were altered. Land versus ocean differences are explained largely by latent heat flux differences: the ocean is an infinite evaporative source, while land can be quite dry. The latitudinally varying case has a much larger response at mid- to high latitudes than at low latitudes; the high latitudes actually appear to effectively warm the low latitudes. Simulations exploring scenarios of glacial inception suggest that the deep ocean alone is not likely to be a key trigger but must operate in conjunction with other forcings, such as reduced carbon dioxide. Moist upland regions at mid- and high latitudes, and land regions adjacent to perennial sea ice, are the preferred locations for glacial inception in these runs. Finally, the model combination equilibrates very rapidly, meaning that a large number of simulations can be made for a fairly modest computational cost. A drawback to this is greatly reduced sensitivity to parameters such as atmospheric carbon dioxide, which requires a full response of the ocean. Thus, this approach can be considered intermediate between fixing, or prescribing, sea surface temperatures and a fully coupled modeling approach.

Winter 2018 major sudden stratospheric warming impact on midlatitude mesosphere from microwave radiometer measurements

10.5194/acp-2018-1361 ◽

2019 ◽

Cited By ~ 2

Author(s):

Yuke Wang ◽

Valery Shulga ◽

Gennadi Milinevsky ◽

Aleksey Patoka ◽

Oleksandr Evtushevsky ◽

...

Keyword(s):

Zonal Wind ◽

Geopotential Height ◽

Microwave Radiometer ◽

Recovery Phase ◽

The Arctic ◽

Stratospheric Warming ◽

Easterly Wind ◽

The Impact ◽

Midlatitude Mesosphere

Abstract. The impact of a major sudden stratospheric warming (SSW) in the Arctic in February 2018 on the mid-latitude mesosphere was investigated by performing microwave radiometer measurements of carbon monoxide (CO) and zonal wind above Kharkiv, Ukraine (50.0° N, 36.3° E). The mesospheric peculiarities of this SSW event were observed using recently designed and installed microwave radiometer in East Europe for the first time. The data from the ERA-Interim and NCEP–NCAR reanalyses, as well as the Aura Microwave Limb Sounder measurements, have been also used. Microwave observations of the daily CO profiles in January–March 2018 allowed retrieving mesospheric zonal wind at 70–85 km (below the winter mesopause) over the Kharkiv site. The reverse of the mesospheric westerly from about 10 m s−1 to the easterly wind of about −10 m s−1 around 10 February has been registered. Local microwave observations in the NH midlatitudes combined with reanalysis data show wide ranges of daily variability in CO, zonal wind, temperature and geopotential height in the mesosphere and stratosphere during the SSW 2018. Oscillations in the vertical CO profile, zonal wind, and geopotential height during the SSW, stratopause disappearance after the SSW onset and strong CO and westerly wind peaks at the start of the SSW recovery phase have been observed. The observed CO variability can be explained by vertical and horizontal air mass redistribution due to planetary wave activity with the replacement of the CO-rich air by CO-poor air and vice versa, in agreement with other studies. The results of microwave measurements of CO and zonal wind in the midlatitude mesosphere at 70–85 km altitudes, which still is not adequately covered by ground-based observations, are useful for improving our understanding of the SSW impacts in this region.

The Role of Zonal Asymmetry in the Enhancement and Suppression of Sudden Stratospheric Warming Variability by the Madden–Julian Oscillation

Journal of Climate ◽

10.1175/jcli-d-17-0489.1 ◽

2018 ◽

Vol 31 (6) ◽

pp. 2399-2415 ◽

Cited By ~ 4

Author(s):

Wanying Kang ◽

Eli Tziperman

Keyword(s):

General Circulation ◽

Dominant Role ◽

The Arctic ◽

Stationary Waves ◽

Madden Julian Oscillation ◽

Stratospheric Warming ◽

Zonal Asymmetry ◽

Forced Waves ◽

The Arctic Oscillation

Sudden stratospheric warming (SSW) events influence the Arctic Oscillation and midlatitude extreme weather. Previous work showed the Arctic stratosphere to be influenced by the Madden–Julian oscillation (MJO) and that the SSW frequency increases with an increase of the MJO amplitude, expected in a warmer climate. It is shown here that the zonal asymmetry in both the background state and forcing plays a dominant role, leading to either enhancement or suppression of SSW events by MJO-like forcing. When applying a circumglobal MJO-like forcing in a dry dynamic core model, the MJO-forced waves can change the general circulation in three ways that affect the total vertical Eliassen–Palm flux in the Arctic stratosphere. First, weakening the zonal asymmetry of the tropospheric midlatitude jet, and therefore preventing the MJO-forced waves from propagating past the jet. Second, weakening the jet amplitude, reducing the waves generated in the midlatitudes, especially stationary waves, and therefore the upward-propagating planetary waves. Third, reducing the Arctic lower-stratospheric refractory index, which prevents waves from upward propagation. These effects stabilize the Arctic vortex and lower the SSW frequency. The longitudinal range to which the MJO-like forcing is limited plays an important role as well, and the strongest SSW frequency increase is seen when the MJO is located where it is observed in current climate. The SSW suppression effects are active when the MJO-like forcing is placed at different longitudinal locations. This study suggests that future trends in both the MJO amplitude and its longitudinal extent are important for predicting the Arctic stratosphere response.

Sensitivity of simulated oxygen isotopes in ice cores and speleothems to Last Glacial Maximum surface conditions

10.5194/egusphere-egu21-2305 ◽

2021 ◽

Author(s):

André Paul ◽

Alexandre Cauquoin ◽

Stefan Mulitza ◽

Thejna Tharammal ◽

Martin Werner

Keyword(s):

Last Glacial Maximum ◽

General Circulation ◽

Ice Cores ◽

Glacial Maximum ◽

Sea Surface ◽

Surface Conditions ◽

Last Glacial ◽

The Impact ◽

Mean Square Errors

In simulations of the climate during the Last Glacial Maximum (LGM), we employ two different isotope-enabled atmospheric general circulation models (NCAR iCAM3 and MPI ECHAM6-wiso) and use simulated (by coupled climate models) as well as reconstructed (from a new global climatology of the ocean surface duing the LGM, GLOMAP) surface conditions.The resulting atmospheric fields reflect the more pronounced structure and gradients in the reconstructions, for example, the precipitation is more depleted in oxygen-18 in the high latitudes and more enriched in low latitudes, especially in the tropical convective regions over the maritime continent in the equatorial Pacific and Indian Oceans and over the equatorial Atlantic Ocean. Furthermore, at the sites of ice cores and speleothems, the model-data fit improves in terms of the coefficients of determination and root-mean square errors.In additional sensitivity experiments, we also use the climatologies by Annan and Hargreaves (2013) and Tierney et al. (2020) and consider the impact of changes in reconstructed sea-ice extent and the global-mean sea-surface temperature.Our findings imply that the correct simulation or reconstruction of patterns and gradients in sea-surface conditions are crucial for a successful comparison to oxygen-isotope data from ice cores and speleothems.

Winter 2018 major sudden stratospheric warming impact on midlatitude mesosphere from microwave radiometer measurements

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-10303-2019 ◽

2019 ◽

Vol 19 (15) ◽

pp. 10303-10317 ◽

Cited By ~ 5

Author(s):

Yuke Wang ◽

Valerii Shulga ◽

Gennadi Milinevsky ◽

Aleksey Patoka ◽

Oleksandr Evtushevsky ◽

...

Keyword(s):

Zonal Wind ◽

Microwave Radiometer ◽

Polar Vortex ◽

The Arctic ◽

Stratospheric Warming ◽

Time Data ◽

Easterly Wind ◽

The Impact ◽

Midlatitude Mesosphere

Abstract. The impact of a major sudden stratospheric warming (SSW) in the Arctic in February 2018 on the midlatitude mesosphere is investigated by performing the microwave radiometer measurements of carbon monoxide (CO) and zonal wind above Kharkiv, Ukraine (50.0∘ N, 36.3∘ E). The mesospheric peculiarities of this SSW event were observed using a recently designed and installed microwave radiometer in eastern Europe for the first time. Data from the ERA-Interim and MERRA-2 reanalyses, as well as the Aura microwave limb sounder measurements, are also used. Microwave observations of the daily CO profiles in January–March 2018 allowed for the retrieval of mesospheric zonal wind at 70–85 km (below the winter mesopause) over the Kharkiv site. Reversal of the mesospheric westerly from about 10 m s−1 to an easterly wind of about −10 m s−1 around 10 February was observed. The local microwave observations at our Northern Hemisphere (NH) midlatitude site combined with reanalysis data show wide-ranging daily variability in CO, zonal wind, and temperature in the mesosphere and stratosphere during the SSW of 2018. The observed local CO variability can be explained mainly by horizontal air mass redistribution due to planetary wave activity. Replacement of the CO-rich polar vortex air by CO-poor air of the surrounding area led to a significant mesospheric CO decrease over the station during the SSW and fragmentation of the vortex over the station at the SSW start caused enhanced stratospheric CO at about 30 km. The results of microwave measurements of CO and zonal wind in the midlatitude mesosphere at 70–85 km altitudes, which still are not adequately covered by ground-based observations, are useful for improving our understanding of the SSW impacts in this region.

A Simplistic Approach for Assessing Hydroclimatic Vulnerability of Lakes and Reservoirs with Regulated Superficial Outflow

Hydrology ◽

10.3390/hydrology6030061 ◽

2019 ◽

Vol 6 (3) ◽

pp. 61 ◽

Cited By ~ 1

Author(s):

Kleoniki Demertzi ◽

Dimitris Papadimos ◽

Vassilis Aschonitis ◽

Dimitris Papamichail

Keyword(s):

Climate Change ◽

General Circulation ◽

Drainage Basin ◽

Management Strategies ◽

Climatic Conditions ◽

Modified Model ◽

Natural Lakes ◽

The Future ◽

This study proposes a simplistic model for assessing the hydroclimatic vulnerability of lakes/reservoirs (LRs) that preserve their steady-state conditions based on regulated superficial discharge (Qd) out of the LR drainage basin. The model is a modification of the Bracht-Flyr et al. method that was initially proposed for natural lakes in closed basins with no superficial discharge outside the basin (Qd = 0) and under water-limited environmental conditions {mean annual ratio of potential/reference evapotranspiration (ETo) versus rainfall (P) greater than 1}. In the proposed modified approach, an additional Qd function is included. The modified model is applied using as a case study the Oreastiada Lake, which is located inside the Kastoria basin in Greece. Six years of observed data of P, ETo, Qd, and lake topography were used to calibrate the modified model based on the current conditions. The calibrated model was also used to assess the future lake conditions based on the future climatic projections (mean conditions of 2061-2080) derived by 19 general circulation models (GCMs) for three cases of climate change (three cases of Representative Concentration Pathways: RCP2.6, RCP4.5 and RCP8.5). The modified method can be used as a diagnostic tool in water-limited environments for analyzing the superficial discharge changes of LRs under different climatic conditions and to support the design of new management strategies for mitigating the impact of climate change on (a) flooding conditions, (b) hydroelectric production, (c) irrigation/industrial/domestic use and (d) minimum ecological flows to downstream rivers.