Emergence of representative signals for sudden stratospheric warmings beyond current predictable lead times

Abstract. Major sudden stratospheric warmings (SSWs) are extreme wintertime circulation events of the Arctic stratosphere that are accompanied by a breakdown of the polar vortex and are considered an important source of predictability of tropospheric weather on subseasonal to seasonal timescales over the Northern Hemisphere midlatitudes and high latitudes. However, SSWs themselves are difficult to predict, with a predictability limit of around 1 to 2 weeks. The predictability limit for determining the type of event, i.e., wave-1 or wave-2 events, is even shorter. Here we analyze the dynamics of the vortex breakdown and look for early signs of the vortex deceleration process at lead times beyond the current predictability limit of SSWs. To this end, we employ a mode decomposition analysis to study the potential vorticity (PV) equation on the 850 K isentropic surface by decomposing each term in the PV equation using the empirical orthogonal functions of the PV. The first principal component (PC) is an indicator of the strength of the polar vortex and starts to increase from around 25 d before the onset of SSWs, indicating a deceleration of the polar vortex. A budget analysis based on the mode decomposition is then used to characterize the contribution of the linear and nonlinear PV advection terms to the rate of change (tendency) of the first PC. The linear PV advection term is the main contributor to the PC tendency at 25 to 15 d before the onset of SSW events for both wave-1 and wave-2 events. The nonlinear PV advection term becomes important between 15 and 1 d before the onset of wave-2 events, while the linear PV advection term continues to be the main contributor for wave-1 events. By linking the PV advection to the PV flux, we find that the linear PV flux is important for both types of SSWs from 25 to 15 d prior to the events but with different wave-2 spatial patterns, while the nonlinear PV flux displays a wave-3 wave pattern, which finally leads to a split of the polar vortex. Early signs of SSW events arise before the 1- to 2-week prediction limit currently observed in state-of-the-art prediction systems, while signs for the type of event arise at least 1 week before the event onset.

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Extended-range predictability of sudden stratospheric warming events suggested by mode decomposition

10.5194/wcd-2021-14 ◽

2021 ◽

Author(s):

Zheng Wu ◽

Bernat Jiménez-Esteve ◽

Raphaël de Fondeville ◽

Enikő Székely ◽

Guillaume Obozinski ◽

...

Keyword(s):

Decomposition Analysis ◽

Polar Vortex ◽

Principal Component ◽

Empirical Orthogonal Functions ◽

Rate Of Change ◽

The Arctic ◽

Lead Times ◽

Main Contributor ◽

Budget Analysis ◽

Mode Decomposition

Abstract. Major sudden stratospheric warmings (SSWs) are extreme wintertime circulation events of the Arctic stratosphere that are accompanied by a breakdown of the polar vortex and are considered an important source of predictability of tropospheric weather on subseasonal to seasonal time scales over the Northern Hemisphere mid- and high- latitudes. However, SSWs themselves are difficult to forecast, with a predictability limit of around one to two weeks. The predictability limit for determining the type of event, i.e., wave-1 or wave-2 events, is even shorter. Here we analyze the dynamics of the vortex breakdown and look for early signs of the vortex deceleration process with lead times beyond the current predictability limit of SSWs. To this end, we employ a mode decomposition analysis to analyze potential vorticity (PV) equation on the 850 K isentropic surface by decomposing each term in the PV equation using the empirical orthogonal functions of the PV. The first principal component (PC) is an indicator of the strength of the polar vortex and starts to increase from around 25 days before the onset of SSWs, indicating a deceleration of the polar vortex. We then use a budget analysis based on the mode decomposition to characterize the contribution of the linear and the nonlinear PV advection terms to the rate of change (tendency) of the first PC. The linear PV advection is the main contributor to the PC tendency at 15 to 25 days before the onset of both types of SSW events. The nonlinear PV advection becomes important between 1 to 15 days before the onset of wave-2 events, while the linear PV advection continues to be the main contributor for wave-1 events. By linking the PV advection to the PV flux, we find that the linear PV flux is important for both types of SSWs from 15 to 25 days before the events but with different wave-2 spatial patterns, while the nonlinear PV flux displays a wave-3 wave pattern, which finally leads to a split of the polar vortex. The signals found here indicate that both the lead times for predicting the SSW onset and the lead times for predicting the type of the SSW event could potentially be extended beyond the current predictability limit of one to two weeks.

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Extended-range predictability of sudden stratospheric warming events suggested by mode decomposition

10.5194/egusphere-egu21-2607 ◽

2021 ◽

Author(s):

Zheng Wu ◽

Bernat Jiménez-Esteve ◽

Raphael de Fondeville ◽

Eniko Székely ◽

Guillaume Obozinski ◽

...

Keyword(s):

Vortex Breakdown ◽

Early Stage ◽

Principal Component ◽

Empirical Orthogonal Functions ◽

The Arctic ◽

Lead Times ◽

Dynamical Process ◽

Orthogonal Functions ◽

Mode Decomposition ◽

Advection Term

Major sudden stratospheric warmings (SSWs) are extreme wintertime circulation events of the Arctic stratosphere that are accompanied by a breakdown of the polar vortex. The stratospheric anomalies can propagate downward to the lower stratosphere and influence the weather of the troposphere and the surface for up to two months after the onset of SSW events. Therefore, SSWs can be an important source of predictability on subseasonal to seasonal (S2S) time scales over the Northern Hemisphere (NH) mid- and high- latitudes. However, SSWs themselves are difficult to forecast, with a predictability limit of around one to two weeks. Therefore, understanding the dynamical process that leads to the vortex breakdown is crucial to improve the predictability of SSWs, and ultimately, the weather at the Earth&#8217;s surface. To this end, we employ a mode decomposition diagnosis to analyze Ertel's potential vorticity (PV) equation by decomposing each term using empirical orthogonal functions (EOFs) of PV to study the vortex weakening process. With this method, a principal component (PC) tendency equation can be derived, which includes the evolution of the linear and nonlinear PV advection terms and indicates how they contribute to the vortex weakening. The results show that the linear advection term is the main contributor to the increase of PC tendency in the early stage of the warming and contains distinct signals that indicate the weakening of the vortex as early as 25 days before the onset of SSWs using ERA-interim daily data. Our results indicate that both the lead times of the onset of SSW events as well as the type of the event may be extended beyond the current predictability limit, promising to provide longer lead times for the prediction of surface weather.&#160;

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On the Nonlinearity of Winter Northern Hemisphere Atmospheric Variability

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-18-0182.1 ◽

2019 ◽

Vol 76 (1) ◽

pp. 333-356 ◽

Cited By ~ 3

Author(s):

A. Hannachi ◽

W. Iqbal

Keyword(s):

North Atlantic ◽

Polar Vortex ◽

Principal Component ◽

Empirical Orthogonal Functions ◽

The Arctic ◽

Climate Change Signal ◽

Two Dimensional ◽

Orthogonal Functions ◽

Local Flow ◽

The North

Abstract Nonlinearity in the Northern Hemisphere’s wintertime atmospheric flow is investigated from both an intermediate-complexity model of the extratropics and reanalyses. A long simulation is obtained using a three-level quasigeostrophic model on the sphere. Kernel empirical orthogonal functions (EOFs), which help delineate complex structures, are used along with the local flow tendencies. Two fixed points are obtained, which are associated with strong bimodality in two-dimensional kernel principal component (PC) space, consistent with conceptual low-order dynamics. The regimes reflect zonal and blocked flows. The analysis is then extended to ERA-40 and JRA-55 using daily sea level pressure (SLP) and geopotential heights in the stratosphere (20 hPa) and troposphere (500 hPa). In the stratosphere, trimodality is obtained, representing disturbed, displaced, and undisturbed states of the winter polar vortex. In the troposphere, the probability density functions (PDFs), for both fields, within the two-dimensional (2D) kernel EOF space are strongly bimodal. The modes correspond broadly to opposite phases of the Arctic Oscillation with a signature of the negative North Atlantic Oscillation (NAO). Over the North Atlantic–European sector, a trimodal PDF is also obtained with two strong and one weak modes. The strong modes are associated, respectively, with the north (or +NAO) and south (or −NAO) positions of the eddy-driven jet stream. The third weak mode is interpreted as a transition path between the two positions. A climate change signal is also observed in the troposphere of the winter hemisphere, resulting in an increase (a decrease) in the frequency of the polar high (low), consistent with an increase of zonal flow frequency.

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A Match-based approach to the estimation of polar stratospheric ozone loss using Aura Microwave Limb Sounder observations

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-9945-2015 ◽

2015 ◽

Vol 15 (17) ◽

pp. 9945-9963 ◽

Cited By ~ 21

Author(s):

N. J. Livesey ◽

M. L. Santee ◽

G. L. Manney

Keyword(s):

Stratospheric Ozone ◽

Potential Temperature ◽

Polar Vortex ◽

Rate Of Change ◽

The Arctic ◽

Air Mass ◽

Ozone Loss ◽

Chemical Destruction ◽

Induced Changes ◽

The Impact

Abstract. The well-established "Match" approach to quantifying chemical destruction of ozone in the polar lower stratosphere is applied to ozone observations from the Microwave Limb Sounder (MLS) on NASA's Aura spacecraft. Quantification of ozone loss requires distinguishing transport- and chemically induced changes in ozone abundance. This is accomplished in the Match approach by examining cases where trajectories indicate that the same air mass has been observed on multiple occasions. The method was pioneered using ozonesonde observations, for which hundreds of matched ozone observations per winter are typically available. The dense coverage of the MLS measurements, particularly at polar latitudes, allows matches to be made to thousands of observations each day. This study is enabled by recently developed MLS Lagrangian trajectory diagnostic (LTD) support products. Sensitivity studies indicate that the largest influence on the ozone loss estimates are the value of potential vorticity (PV) used to define the edge of the polar vortex (within which matched observations must lie) and the degree to which the PV of an air mass is allowed to vary between matched observations. Applying Match calculations to MLS observations of nitrous oxide, a long-lived tracer whose expected rate of change is negligible on the weekly to monthly timescales considered here, enables quantification of the impact of transport errors on the Match-based ozone loss estimates. Our loss estimates are generally in agreement with previous estimates for selected Arctic winters, though indicating smaller losses than many other studies. Arctic ozone losses are greatest during the 2010/11 winter, as seen in prior studies, with 2.0 ppmv (parts per million by volume) loss estimated at 450 K potential temperature (~ 18 km altitude). As expected, Antarctic winter ozone losses are consistently greater than those for the Arctic, with less interannual variability (e.g., ranging between 2.3 and 3.0 ppmv at 450 K). This study exemplifies the insights into atmospheric processes that can be obtained by applying the Match methodology to a densely sampled observation record such as that from Aura MLS.

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Understanding the role of the troposphere in the surface impact of the 2018 sudden stratospheric warming event

10.5194/egusphere-egu21-8495 ◽

2021 ◽

Author(s):

Juan J. González-Alemán ◽

Christian M. Grams ◽

Blanca Ayarzagüena ◽

Pablo Zurita-Gotor ◽

Daniela I. V. Domeisen Domeisen ◽

...

Keyword(s):

North Atlantic ◽

Vortex Breakdown ◽

Rapid Change ◽

Polar Vortex ◽

The Arctic ◽

Lead Times ◽

Strong Impact ◽

Ensemble Forecasts ◽

Stratospheric Polar Vortex ◽

The North

Sudden stratospheric warmings (SSWs) are impressive phenomena that consist of a rapid stratospheric polar vortex breakdown. SSWs can have a strong impact on the tropospheric weather and are mainly associated with the negative phases of the Arctic and North Atlantic Oscillations (AO, NAO), and with northern European cold outbreaks, thus causing high societal impact. However, the mechanisms behind the downward impact from the stratosphere are insufficiently understood, especially the role played by the troposphere. In this work, we investigate this coupling and its associated predictability limits by studying the 2018 SSW event.By analyzing ECMWF 15-day ensemble forecasts and partitioning them into different weather regimes, we search for possible dynamical tropospheric events that may have favored the downward stratosphere-troposphere coupling during and after the SSW. It is found that two cyclogenesis events were the main drivers of the negative NAO pattern associated with a Greenland Blocking, causing a rapid change from prevailing westerlies into a blocked state in the North Atlantic region. Unless these cyclogenesis events are simulated in the forecasts, the prediction of a Greenland Blocking does not become highly prevalent. No important stratospheric differences between WRs were found. A possible oceanic contribution to this blocked state is also found. This work corroborates that individual synoptic events might constitute a &#8220;predictability barrier" for subsequent forecast lead times. It also sheds light, on the specific topic of troposphere-stratosphere coupling.

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A Match-based approach to the estimation of polar stratospheric ozone loss using Aura Microwave Limb Sounder observations

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-10041-2015 ◽

2015 ◽

Vol 15 (7) ◽

pp. 10041-10083 ◽

Cited By ~ 2

Author(s):

N. J. Livesey ◽

M. L. Santee ◽

G. L. Manney

Keyword(s):

Stratospheric Ozone ◽

Potential Temperature ◽

Polar Vortex ◽

Rate Of Change ◽

The Arctic ◽

Ozone Loss ◽

Chemically Induced ◽

Chemical Destruction ◽

Induced Changes ◽

The Impact

Abstract. The well-established "Match" approach to quantifying chemical destruction of ozone in the polar lower stratosphere is applied to ozone observations from the Microwave Limb Sounder (MLS) on NASA's Aura spacecraft. Quantification of ozone loss requires distinguishing transport- and chemically induced changes in ozone abundance. This is accomplished in the Match approach by examining cases where trajectories indicate that the same airmass has been observed on multiple occasions. The method was pioneered using ozone sonde observations, for which hundreds of matched ozone observations per winter are typically available. The dense coverage of the MLS measurements, particularly at polar latitudes, allows matches to be made to thousands of observations each day. This study is enabled by recently developed MLS Lagrangian Trajectory Diagnostic (LTD) support products. Sensitivity studies indicate that the largest influence on the ozone loss estimates are the value of potential vorticity (PV) used to define the edge of the polar vortex (within which matched observations must lie) and the degree to which the PV of an airmass is allowed to vary between matched observations. Applying Match calculations to MLS observations of nitrous oxide, a long-lived tracer whose expected rate of change on these timescales is negligible, enables quantification of the impact of transport errors on the Match-based ozone loss estimates. Our loss estimates are generally in agreement with previous estimates for selected Arctic winters, though indicating smaller losses than many other studies. Arctic ozone losses are greatest during the 2010/11 winter, as seen in prior studies, with 2.0 ppmv (parts per million by volume) loss estimated at 450 K potential temperature. As expected, Antarctic winter ozone losses are consistently greater than those for the Arctic, with less interannual variability (e.g., ranging between 2.3 and 3.0 ppmv at 450 K). This study exemplifies the insights into atmospheric processes that can be obtained by applying the Match methodology to a densely sampled observation record such as that from Aura MLS.

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The Diurnal Variation in Stratospheric Ozone from MACC Reanalysis, ERA-Interim, WACCM, and Earth Observation Data: Characteristics and Intercomparison

Atmosphere ◽

10.3390/atmos12050625 ◽

2021 ◽

Vol 12 (5) ◽

pp. 625

Author(s):

Ansgar Schanz ◽

Klemens Hocke ◽

Niklaus Kämpfer ◽

Simon Chabrillat ◽

Antje Inness ◽

...

Keyword(s):

Diurnal Variation ◽

Climate Model ◽

Stratospheric Ozone ◽

Polar Vortex ◽

Model Systems ◽

Atmospheric Composition ◽

The Arctic ◽

Observation Data ◽

High Latitudes ◽

Free Running

In this study, we compare the diurnal variation in stratospheric ozone of the MACC (Monitoring Atmospheric Composition and Climate) reanalysis, ECMWF Reanalysis Interim (ERA-Interim), and the free-running WACCM (Whole Atmosphere Community Climate Model). The diurnal variation of stratospheric ozone results from photochemical and dynamical processes depending on altitude, latitude, and season. MACC reanalysis and WACCM use similar chemistry modules and calculate a similar diurnal cycle in ozone when it is caused by a photochemical variation. The results of the two model systems are confirmed by observations of the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) experiment and three selected sites of the Network for Detection of Atmospheric Composition Change (NDACC) at Mauna Loa, Hawaii (tropics), Bern, Switzerland (midlatitudes), and Ny-Ålesund, Svalbard (high latitudes). On the other hand, the ozone product of ERA-Interim shows considerably less diurnal variation due to photochemical variations. The global maxima of diurnal variation occur at high latitudes in summer, e.g., near the Arctic NDACC site at Ny-Ålesund, Svalbard. The local OZORAM radiometer observes this effect in good agreement with MACC reanalysis and WACCM. The sensed diurnal variation at Ny-Ålesund is up to 8% (0.4 ppmv) due to photochemical variations in summer and negligible during the dynamically dominated winter. However, when dynamics play a major role for the diurnal ozone variation as in the lower stratosphere (100–20 hPa), the reanalysis models ERA-Interim and MACC which assimilate data from radiosondes and satellites outperform the free-running WACCM. Such a domain is the Antarctic polar winter where a surprising novel feature of diurnal variation is indicated by MACC reanalysis and ERA-Interim at the edge of the polar vortex. This effect accounts for up to 8% (0.4 ppmv) in both model systems. In summary, MACC reanalysis provides a global description of the diurnal variation of stratospheric ozone caused by dynamics and photochemical variations. This is of high interest for ozone trend analysis and other research which is based on merged satellite data or measurements at different local time.

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Effects of Climatic Drivers and Teleconnections on Late 20th Century Trends in Spring Freshet of Four Major Arctic-Draining Rivers

Water ◽

10.3390/w13020179 ◽

2021 ◽

Vol 13 (2) ◽

pp. 179

Author(s):

Roxanne Ahmed ◽

Terry Prowse ◽

Yonas Dibike ◽

Barrie Bonsal

Keyword(s):

Arctic Ocean ◽

Large Scale ◽

Southern Oscillation ◽

Rate Of Change ◽

The Arctic ◽

Late 20Th Century ◽

Basin Scale ◽

The Arctic Ocean ◽

Spring Freshet ◽

Climatic Drivers

Spring freshet is the dominant annual discharge event in all major Arctic draining rivers with large contributions to freshwater inflow to the Arctic Ocean. Research has shown that the total freshwater influx to the Arctic Ocean has been increasing, while at the same time, the rate of change in the Arctic climate is significantly higher than in other parts of the globe. This study assesses the large-scale atmospheric and surface climatic conditions affecting the magnitude, timing and regional variability of the spring freshets by analyzing historic daily discharges from sub-basins within the four largest Arctic-draining watersheds (Mackenzie, Ob, Lena and Yenisei). Results reveal that climatic variations closely match the observed regional trends of increasing cold-season flows and earlier freshets. Flow regulation appears to suppress the effects of climatic drivers on freshet volume but does not have a significant impact on peak freshet magnitude or timing measures. Spring freshet characteristics are also influenced by El Niño-Southern Oscillation, the Pacific Decadal Oscillation, the Arctic Oscillation and the North Atlantic Oscillation, particularly in their positive phases. The majority of significant relationships are found in unregulated stations. This study provides a key insight into the climatic drivers of observed trends in freshet characteristics, whilst clarifying the effects of regulation versus climate at the sub-basin scale.

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Chemical ozone loss and ozone mini-hole event during the Arctic winter 2010/2011 as observed by SCIAMACHY and GOME-2

Atmospheric Chemistry and Physics ◽

10.5194/acp-14-3247-2014 ◽

2014 ◽

Vol 14 (7) ◽

pp. 3247-3276 ◽

Cited By ~ 16

Author(s):

R. Hommel ◽

K.-U. Eichmann ◽

J. Aschmann ◽

K. Bramstedt ◽

M. Weber ◽

...

Keyword(s):

Transport Model ◽

Polar Vortex ◽

The Arctic ◽

Optical Absorption Spectroscopy ◽

Late Winter ◽

Total Column Ozone ◽

Bromine Oxide ◽

Ozone Loss ◽

Catalytic Cycles ◽

Total Column

Abstract. Record breaking loss of ozone (O3) in the Arctic stratosphere has been reported in winter–spring 2010/2011. We examine in detail the composition and transformations occurring in the Arctic polar vortex using total column and vertical profile data products for O3, bromine oxide (BrO), nitrogen dioxide (NO2), chlorine dioxide (OClO), and polar stratospheric clouds (PSC) retrieved from measurements made by SCIAMACHY (Scanning Imaging Absorption SpectroMeter for Atmospheric CHartography) on-board Envisat (Environmental Satellite), as well as total column ozone amount, retrieved from the measurements of GOME-2 (Global Ozone Monitoring Experiment) on MetOp-A (Meteorological Experimental Satellite). Similarly we use the retrieved data from DOAS (Differential Optical Absorption Spectroscopy) measurements made in Ny-Ålesund (78.55° N, 11.55° E). A chemical transport model (CTM) has been used to relate and compare Arctic winter–spring conditions in 2011 with those in the previous year. In late winter–spring 2010/2011 the chemical ozone loss in the polar vortex derived from SCIAMACHY observations confirms findings reported elsewhere. More than 70% of O3 was depleted by halogen catalytic cycles between the 425 and 525 K isentropic surfaces, i.e. in the altitude range ~16–20 km. In contrast, during the same period in the previous winter 2009/2010, a typical warm Arctic winter, only slightly more than 20% depletion occurred below 20 km, while 40% of O3 was removed above the 575 K isentrope (~23 km). This loss above 575 K is explained by the catalytic destruction by NOx descending from the mesosphere. In both Arctic winters 2009/2010 and 2010/2011, calculated O3 losses from the CTM are in good agreement to our observations and other model studies. The mid-winter 2011 conditions, prior to the catalytic cycles being fully effective, are also investigated. Surprisingly, a significant loss of O3 around 60%, previously not discussed in detail, is observed in mid-January 2011 below 500 K (~19 km) and sustained for approximately 1 week. The low O3 region had an exceptionally large spatial extent. The situation was caused by two independently evolving tropopause elevations over the Asian continent. Induced adiabatic cooling of the stratosphere favoured the formation of PSC, increased the amount of active chlorine for a short time, and potentially contributed to higher polar ozone loss later in spring.

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Volcanic activity sparks the Arctic Oscillation

Scientific Reports ◽

10.1038/s41598-021-94935-6 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Weizheng Qu ◽

Fei Huang ◽

Jinping Zhao ◽

Ling Du ◽

Yong Cao

Keyword(s):

Volcanic Activity ◽

Volcanic Eruption ◽

Arctic Oscillation ◽

Polar Vortex ◽

Volcanic Eruptions ◽

The Arctic ◽

Vortex System ◽

Significant Fluctuation ◽

The Arctic Oscillation

AbstractThe parasol effect of volcanic dust and aerosol caused by volcanic eruption results in the deepening and strengthening of the Arctic vortex system, thus stimulating or strengthening the Arctic Oscillation (AO). Three of the strongest AOs in more than a century have been linked to volcanic eruptions. Every significant fluctuation of the AO index (AOI = ΔH_middle latitudes − ΔH_Arctic) for many years has been associated with a volcanic eruption. Volcanic activity occurring at different locations in the Arctic vortex circulation will exert different effects on the polar vortex.

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