Interannual Variation of Upper Stratospheric Ozone in the Northern Midlatitudes in Early Winter Caused by Planetary Waves
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Abstract Ozone mixing ratios in the upper stratosphere, observed with a millimeter‐wave radiometer at Rikubetsu (43.46°N, 143.77°E), Japan, from November 1999 to February 2017 showed both interannual and seasonal variation, which was characterized by a winter maximum and a summer minimum. During the study period, the summer minima were nearly constant whereas the winter maxima varied interannually and also displayed short‐term variability. The observed ozone mixing ratios at 1 hPa were anticorrelated with temperature at 1 hPa from MERRA‐2 data. The slope of the relationship between the logarithm of ozone concentration and the reciprocal of temperature differed between winter data and both summer and annual data. Therefore, we inferred that both chemistry and dynamics affect short‐term variation of ozone mixing ratios in winter. We then examined the contribution of the polar vortex to interannual variations in ozone and temperature at 1 hPa. When the polar vortex was strong, wave number‐1 planetary waves at high latitude propagated toward the midlatitudes instead of vertically. The vertical component of the wave number‐1 Eliassen‐Palm flux along 43°N at 1 hPa was strongly correlated with zonal mean zonal wind along 60°N at 50 hPa. When the zonal mean westerly wind was strong in December, upper stratospheric (~1 hPa) temperatures over Rikubetsu and over a point on the opposite side of the globe (by longitude) were significantly lower and higher, respectively, than the climatological temperature. Thus, planetary wave propagation related to zonal mean westerly wind strength induced early winter interannual variation in upper stratospheric ozone in the midlatitudes.Keywords:
Middle latitudes
Longitude
Mixing ratio
Abstract In the Arctic winter/spring of 2019/2020, stratospheric temperatures were exceptionally low until early April and the polar vortex was very stable. As a consequence, significant chemical ozone depletion occurred in the Arctic polar vortex in spring 2020. Here, we present simulations using the Chemical Lagrangian Model of the Stratosphere that address the development of chlorine compounds and ozone in the Arctic stratosphere in 2020. The simulation reproduces relevant observations of ozone and chlorine compounds, as shown by comparisons with data from the Microwave Limb Sounder, Atmospheric Chemistry Experiment‐Fourier Transform Spectrometer, balloon‐borne ozone sondes, and the Ozone Monitoring Instrument. Although the concentration of chlorine and bromine compounds in the polar stratosphere has decreased by more than 10% compared to peak values around the year 2000, the meteorological conditions in winter/spring 2019/2020 caused unprecedented ozone depletion. The lowest simulated ozone mixing ratio was about 40 ppbv. Because extremely low ozone mixing ratios were reached in the lower polar stratosphere, chlorine deactivation into HCl occurred as is normally observed in the Antarctic polar vortex. The depletion in partial column ozone in the lower stratosphere (potential temperature from 350 to 600 K, corresponding to about 12–24 km) in the vortex core was calculated to reach 143 Dobson Units, which is more than the ozone loss in 2011 and 2016, the years which —until 2020— had seen the largest Arctic ozone depletion on record.
Ozone Depletion
Microwave Limb Sounder
Polar night
Mixing ratio
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Abstract Data from the MIPAS instrument on Envisat, supplemented by meteorological analyses from ECMWF and the Met Office, are used to study the meteorological and trace‐gas evolution of the stratosphere in the Northern Hemisphere during spring and summer 2003. A Pole‐centred approach, together with sequences of vertical profiles along the viewing tracks of the MIPAS instrument, is used to interpret the data in the physically meaningful context of the evolving summertime high. During April the vortex break‐up and build‐up of the summertime high gives rise, in the mid‐stratosphere, to a ‘frozen‐in’ anticyclone (FrIAC), over the Pole, encircled by vortex fragments at ∼50°N. As the summer moves on, the FrIACs and vortex fragments are gradually smoothed out but they persist in the mid‐ and upper stratosphere until July–August as roughly zonally symmetric W‐shaped tracer isopleths. The persistence of the W shows the slowness of isentropic mixing processes at these levels during the summer. As the summertime high becomes dominant during June–August, net photochemical ozone loss produces a low ozone pool in the lower and mid‐stratosphere. Finally, as the summertime high decays and the wintertime polar vortex builds up from September onward, the low ozone pool extends vertically throughout the stratosphere, and the tracer isopleths at high latitudes start to dip, showing the effects of wintertime diabatic descent. Of these features, to our knowledge, the W‐shaped tracer isopleths have not been observed previously. Copyright © 2007 Royal Meteorological Society
Anticyclone
Sudden stratospheric warming
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Sudden stratospheric warming
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Abstract The sensitivity of the wintertime tropospheric circulation to changes in the strength of the Northern Hemisphere stratospheric polar vortex is studied using one of the latest versions of the ECMWF model. Three sets of experiments were carried out: one control integration and two integrations in which the strength of the stratospheric polar vortex has been gradually reduced and increased, respectively, during the course of the integration. The strength of the polar vortex is changed by applying a forcing to the model tendencies in the stratosphere only. The forcing has been obtained using the adjoint technique. It is shown that, in the ECMWF model, changes in the strength of the polar vortex in the middle and lower stratosphere have a significant and slightly delayed (on the order of days) impact on the tropospheric circulation. The tropospheric response shows some resemblance to the North Atlantic Oscillation (NAO), though the centers of action are slightly shifted toward the east compared to those of the NAO. Furthermore, a separate comparison of the response to a weak and strong vortex forcing suggests that to first order the tropospheric response is linear within a range of realistic stratospheric perturbations. From the results presented, it is argued that extended-range forecasts in the European area particularly benefit from the stratosphere–troposphere link.
Forcing (mathematics)
Sudden stratospheric warming
Quasi-biennial oscillation
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The 1999–2000 Arctic stratospheric vortex was unusually cold, especially in the early winter lower stratosphere, with a larger area near polar stratospheric cloud formation temperatures in Dec and Jan, and much lower temperatures averaged over Nov–Jan, than any previously observed Arctic winter. In Nov and early Dec, there was a double jet in the upper stratosphere, with the anticyclone cutoff in a region of cyclonic material. By late Dec, there was a discontinuous vortex, large in the upper stratosphere, small in the lower stratosphere; evolving to a strong, continuous, relatively upright vortex by mid‐Jan. This vortex evolution in 1999–2000 is typical of that in other cold early winters. Despite unusually low temperatures, the lower stratospheric vortex developed more slowly than in previous unusually cold early winters, and was weaker than average until late Dec.
Sudden stratospheric warming
Anticyclone
Polar night
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Observed and simulated precursors of stratospheric polar vortex anomalies in the Northern Hemisphere
The Northern Hemisphere stratospheric polar vortex is linked to surface weather. After Stratospheric Sudden Warmings in winter, the tropospheric circulation is often nudged towards the negative phase of the Northern Annular Mode (NAM) and the North Atlantic Oscillation (NAO). A strong stratospheric vortex is often associated with subsequent positive NAM/NAO conditions. For stratosphere–troposphere associations to be useful for forecasting purposes it is crucial that changes to the stratospheric vortex can be understood and predicted. Recent studies have proposed that there exist tropospheric precursors to anomalous vortex events in the stratosphere and that these precursors may be understood by considering the relationship between stationary wave patterns and regional variability. Another important factor is the extent to which the inherent variability of the stratosphere in an atmospheric model influences its ability to simulate stratosphere–troposphere links. Here we examine the lower stratosphere variability in 300-year pre-industrial control integrations from 13 coupled climate models. We show that robust precursors to stratospheric polar vortex anomalies are evident across the multi-model ensemble. The most significant tropospheric component of these precursors consists of a height anomaly dipole across northern Eurasia and large anomalies in upward stationary wave fluxes in the lower stratosphere over the continent. The strength of the stratospheric variability in the models was found to depend on the variability of the upward stationary wave fluxes and the amplitude of the stationary waves.
Sudden stratospheric warming
Quasi-biennial oscillation
Arctic oscillation
Atmospheric Circulation
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The polar vortex strengthening leads not only to a temperature decrease in the lower stratosphere, but also to its increase in the upper stratosphere inside the vortex. Over the Antarctic, this dependence is observed from autumn to spring: in the upper stratosphere high temperatures are observed inside the polar vortex, and low temperatures occur outside, especially in spring. Over the Arctic, a temperature increase in the upper Arctic stratosphere is observed under conditions of the strengthening of the northern polar vortex. Temperature variations in the upper polar stratosphere are determined by the ozone concentration and depend on the dynamics of the polar vortex: with a decrease in the ozone content inside the strong vortex in the upper stratosphere, a temperature increase is observed.
Sudden stratospheric warming
Ozone Depletion
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