Representation of the equatorial stratopause semiannual oscillation in global atmospheric reanalyses

Abstract. This paper reports on a project to compare the representation of the semiannual oscillation (SAO) in the equatorial stratosphere and lower mesosphere within six major global atmospheric reanalysis datasets and with recent satellite Sounding of the Atmosphere Using Broadband Emission Radiometry (SABER) and Microwave Limb Sounder (MLS) observations. All reanalyses have a good representation of the quasi-biennial oscillation (QBO) in the equatorial lower and middle stratosphere and each displays a clear SAO centered near the stratopause. However, the differences among reanalyses are much more substantial in the SAO region than in the QBO-dominated region. The degree of disagreement among the reanalyses is characterized by the standard deviation (SD) of the monthly mean zonal wind and temperature; this depends on latitude, longitude, height, and time. The zonal wind SD displays a prominent equatorial maximum that increases with height, while the temperature SD reaches a minimum near the Equator and is largest in the polar regions. Along the Equator, the zonal wind SD is smallest around the longitude of Singapore, where consistently high-quality near-equatorial radiosonde observations are available. Interestingly, the near-Singapore minimum in SD is evident to at least ∼3 hPa, i.e., considerably higher than the usual ∼10 hPa ceiling for in situ radiosonde observations. Our measurement of the agreement among the reanalyses shows systematic improvement over the period considered (1980–2016), up to near the stratopause. Characteristics of the SAO at 1 hPa, such as its detailed time variation and the displacement off the Equator of the zonal wind SAO amplitude maximum, differ significantly among the reanalyses. Disagreement among the reanalyses becomes still greater above 1 hPa. One of the reanalyses in our study also has a version produced without assimilating satellite observations, and a comparison of the SAO in these two versions demonstrates the very great importance of satellite-derived temperatures in the realistic analysis of the tropical upper stratospheric circulation.

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Representation of the Equatorial Stratopause Semiannual Oscillation in Global Atmospheric Reanalyses

10.5194/acp-2020-73 ◽

2020 ◽

Author(s):

Yoshio Kawatani ◽

Toshihiko Hirooka ◽

Kevin Hamilton ◽

Anne K. Smith ◽

Masatomo Fujiwara

Keyword(s):

Zonal Wind ◽

Good Representation ◽

Polar Regions ◽

Quasi Biennial Oscillation ◽

Amplitude Maximum ◽

Systematic Improvement ◽

Stratospheric Circulation ◽

Biennial Oscillation ◽

Semiannual Oscillation

Abstract. This paper reports on a project to compare the representation of the semiannual oscillation (SAO) in the equatorial stratosphere and lower mesosphere among six major global atmospheric reanalysis datasets and with recent satellite SABER and MLS observations. All reanalyses have a good representation of the quasi-biennial oscillation (QBO) in the equatorial lower and middle stratosphere and each displays a clear SAO centered near the stratopause. However, the differences among reanalyses are much more substantial in the SAO region than in the QBO dominated region. The degree of disagreement among the reanalyses is characterized by the standard deviation (SD) of the monthly-mean zonal wind and temperature; this depends on latitude, longitude, height, and time. The zonal wind SD displays a prominent equatorial maximum that increases with height, while the temperature SD is minimum near the equator and largest in the polar regions. Along the equator the zonal wind SD is smallest around the longitude of Singapore where consistently high-quality near-equatorial radiosonde observations are available. Interestingly the near-Singapore minimum in SD is evident to at least ~ 3 hPa, i.e. considerably higher than the usual ~ 10 hPa ceiling for in situ radiosonde observations. Our measurement of the agreement among the reanalyses shows systematic improvement over the period considered (1980–2016), up to near the stratopause. Characteristics of the SAO at 1 hPa, such as its detailed time variation and the displacement off the equator of the zonal wind SAO amplitude maximum, differ significantly among the reanalyses. Disagreement among the reanalyses becomes still greater above 1 hPa. One of the reanalyses in our study also has a version produced without assimilating satellite observations and a comparison of the SAO in these two versions demonstrates the very great importance of satellite derived temperatures in the realistic analysis of the tropical upper stratospheric circulation.

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The Semiannual Oscillation of the Tropical Zonal Wind in the Middle Atmosphere Derived from Satellite Geopotential Height Retrievals

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-17-0067.1 ◽

2017 ◽

Vol 74 (8) ◽

pp. 2413-2425 ◽

Cited By ~ 13

Author(s):

Anne K. Smith ◽

Rolando R. Garcia ◽

Andrew C. Moss ◽

Nicholas J. Mitchell

Keyword(s):

Zonal Wind ◽

Geopotential Height ◽

Middle Atmosphere ◽

Dominant Mode ◽

Quasi Biennial Oscillation ◽

Zonal Winds ◽

Broadband Emission ◽

The Tropics ◽

Biennial Oscillation ◽

Semiannual Oscillation

Abstract The dominant mode of seasonal variability in the global tropical upper-stratosphere and mesosphere zonal wind is the semiannual oscillation (SAO). However, it is notoriously difficult to measure winds at these heights from satellite or ground-based remote sensing. Here, the balance wind relationship is used to derive monthly and zonally averaged zonal winds in the tropics from satellite retrievals of geopotential height. Data from the Aura Microwave Limb Sounder (MLS) cover about 12.5 yr, and those from the Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics (TIMED) Sounding of the Atmosphere Using Broadband Emission Radiometry (SABER) cover almost 15 yr. The derived winds agree with direct wind observations below 10 hPa and above 80 km; there are no direct wind observations for validation in the intervening layers of the middle atmosphere. The derived winds show the following prominent peaks associated with the SAO: easterly maxima near the solstices at 1.0 hPa, westerly maxima near the equinoxes at 0.1 hPa, and easterly maxima near the equinoxes at 0.01 hPa. The magnitudes of these three wind maxima are stronger during the first cycle (January at 1.0 hPa and March at 0.1 and 0.01 hPa). The month and pressure level of the wind maxima shift depending on the phase of the quasi-biennial oscillation (QBO) at 10 hPa. During easterly QBO, the westerly maxima are shifted upward, are about 10 m s−1 stronger, and occur approximately 1 month later than those during the westerly QBO phase.

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Representation of the Tropical Stratospheric Zonal Wind in Global Atmospheric Reanalyses

10.5194/acp-2016-76 ◽

2016 ◽

Cited By ~ 2

Author(s):

Y. Kawatani ◽

K. Hamilton ◽

K. Miyazaki ◽

M. Fujiwara ◽

J. Anstey

Keyword(s):

Phase Transitions ◽

Zonal Wind ◽

Phase Changes ◽

Stationary Waves ◽

Strong Constraint ◽

Quasi Biennial Oscillation ◽

Systematic Improvement ◽

Zonal Wavenumber ◽

In Situ Observations

Abstract. This paper reports on a project to compare the representation of the monthly-mean zonal wind in the equatorial stratosphere among major global atmospheric reanalysis datasets. The degree of disagreement among the reanalyses is characterized by the standard deviation (SD) of the monthly-mean zonal wind and this depends on latitude, longitude, height and the phase of the quasi-biennial oscillation (QBO). At each height the SD displays a prominent equatorial maximum, indicating the particularly challenging nature of the reanalysis problem in the low-latitude stratosphere. At 50–70 hPa the geographical distributions of SD are closely related to the density of radiosonde observations. The largest SD values are over the eastern Pacific, where few in situ observations are available. At 10–20 hPa the spread among the reanalyses and differences with in situ observations both depend significantly on the QBO phase. Notably the easterly-to-westerly phase transitions in all the reanalyses except MERRA are delayed relative to those directly observed at Singapore. In addition, the timing of the easterly-to-westerly phase transitions displays considerable variability among the different reanalyses and this spread is much larger than for the timing of the westerly-to-easterly phase changes. The eddy component in the monthly mean zonal wind near the equator is dominated by zonal wavenumber 1 and 2 quasi-stationary planetary waves propagating from mid-latitudes in the westerly phase of the QBO. There generally is considerable disagreement among the reanalyses in the details of the quasi-stationary waves near the equator. At each level, there is a tendency for the agreement to be best near the longitude of Singapore, suggesting that the Singapore observations act as a strong constraint on all the reanalyses. Our measures of the quality of the reanalysis clearly show systematic improvement over the period considered (1979–2012). The SD among the reanalysis declines significantly over the record, although the geographical pattern of SD remains nearly constant.

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Spatio-temporal variations of nitric acid total columns from 9 years of IASI measurements – a driver study

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-4403-2018 ◽

2018 ◽

Vol 18 (7) ◽

pp. 4403-4423 ◽

Cited By ~ 1

Author(s):

Gaétane Ronsmans ◽

Catherine Wespes ◽

Daniel Hurtmans ◽

Cathy Clerbaux ◽

Pierre-François Coheur

Keyword(s):

Time Series ◽

Temporal Variations ◽

Major Influence ◽

P Value ◽

Spatial And Temporal Variability ◽

Good Representation ◽

Polar Regions ◽

Polar Stratospheric Clouds ◽

Quasi Biennial Oscillation ◽

Stratospheric Clouds

Abstract. This study aims to understand the spatial and temporal variability of HNO3 total columns in terms of explanatory variables. To achieve this, multiple linear regressions are used to fit satellite-derived time series of HNO3 daily averaged total columns. First, an analysis of the IASI 9-year time series (2008–2016) is conducted based on various equivalent latitude bands. The strong and systematic denitrification of the southern polar stratosphere is observed very clearly. It is also possible to distinguish, within the polar vortex, three regions which are differently affected by the denitrification. Three exceptional denitrification episodes in 2011, 2014 and 2016 are also observed in the Northern Hemisphere, due to unusually low arctic temperatures. The time series are then fitted by multivariate regressions to identify what variables are responsible for HNO3 variability in global distributions and time series, and to quantify their respective influence. Out of an ensemble of proxies (annual cycle, solar flux, quasi-biennial oscillation, multivariate ENSO index, Arctic and Antarctic oscillations and volume of polar stratospheric clouds), only the those defined as significant (p value < 0.05) by a selection algorithm are retained for each equivalent latitude band. Overall, the regression gives a good representation of HNO3 variability, with especially good results at high latitudes (60–80 % of the observed variability explained by the model). The regressions show the dominance of annual variability in all latitudinal bands, which is related to specific chemistry and dynamics depending on the latitudes. We find that the polar stratospheric clouds (PSCs) also have a major influence in the polar regions, and that their inclusion in the model improves the correlation coefficients and the residuals. However, there is still a relatively large portion of HNO3 variability that remains unexplained by the model, especially in the intertropical regions, where factors not included in the regression model (such as vegetation fires or lightning) may be at play.

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On the origin of the mesospheric quasi-stationary planetary waves in the unusual Arctic winter 2015/2016

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-4803-2018 ◽

2018 ◽

Vol 18 (7) ◽

pp. 4803-4815 ◽

Cited By ~ 8

Author(s):

Vivien Matthias ◽

Manfred Ern

Keyword(s):

Planetary Wave ◽

Polar Night ◽

Quasi Biennial Oscillation ◽

Model Studies ◽

Broadband Emission ◽

Variable Gravity ◽

Stationary Planetary Wave ◽

Second Period ◽

Biennial Oscillation

Abstract. The midwinter 2015/2016 was characterized by an unusually strong polar night jet (PNJ) and extraordinarily large stationary planetary wave (SPW) amplitudes in the subtropical mesosphere. The aim of this study is, therefore, to find the origin of these mesospheric SPWs in the midwinter 2015/2016 study period. The study duration is split into two periods: the first period runs from late December 2015 until early January 2016 (Period I), and the second period from early January until mid-January 2016 (Period II). While the SPW 1 dominates in the subtropical mesosphere in Period I, it is the SPW 2 that dominates in Period II. There are three possibilities explaining how SPWs can occur in the mesosphere: (1) they propagate upward from the stratosphere, (2) they are generated in situ by longitudinally variable gravity wave (GW) drag, or (3) they are generated in situ by barotropic and/or baroclinic instabilities. Using global satellite observations from the Microwave Limb Sounder (MLS) and the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) the origin of the mesospheric SPWs is investigated for both time periods. We find that due to the strong PNJ the SPWs were not able to propagate upward into the mesosphere northward of 50∘ N but were deflected upward and equatorward into the subtropical mesosphere. We show that the SPWs observed in the subtropical mesosphere are the same SPWs as in the mid-latitudinal stratosphere. Simultaneously, we find evidence that the mesospheric SPWs in polar latitudes were generated in situ by longitudinally variable GW drag and that there is a mixture of in situ generation by longitudinally variable GW drag and by instabilities at mid-latitudes. Our results, based on observations, show that the abovementioned three mechanisms can act at the same time which confirms earlier model studies. Additionally, the possible contribution from, or impact of, unusually strong SPWs in the subtropical mesosphere to the disruption of the quasi-biennial oscillation (QBO) in the same winter is discussed.

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Representation of the tropical stratospheric zonal wind in global atmospheric reanalyses

Atmospheric Chemistry and Physics ◽

10.5194/acp-16-6681-2016 ◽

2016 ◽

Vol 16 (11) ◽

pp. 6681-6699 ◽

Cited By ~ 31

Author(s):

Yoshio Kawatani ◽

Kevin Hamilton ◽

Kazuyuki Miyazaki ◽

Masatomo Fujiwara ◽

James A. Anstey

Keyword(s):

Phase Transitions ◽

Zonal Wind ◽

Phase Changes ◽

Stationary Waves ◽

Central Pacific ◽

Strong Constraint ◽

Quasi Biennial Oscillation ◽

Zonal Wavenumber ◽

In Situ Observations

Abstract. This paper reports on a project to compare the representation of the monthly-mean zonal wind in the equatorial stratosphere among major global atmospheric reanalysis data sets. The degree of disagreement among the reanalyses is characterized by the standard deviation (SD) of the monthly-mean zonal wind and this depends on latitude, longitude, height, and the phase of the quasi-biennial oscillation (QBO). At each height the SD displays a prominent equatorial maximum, indicating the particularly challenging nature of the reanalysis problem in the low-latitude stratosphere. At 50–70 hPa the geographical distributions of SD are closely related to the density of radiosonde observations. The largest SD values are over the central Pacific, where few in situ observations are available. At 10–20 hPa the spread among the reanalyses and differences with in situ observations both depend significantly on the QBO phase. Notably the easterly-to-westerly phase transitions in all the reanalyses except MERRA are delayed relative to those directly observed in Singapore. In addition, the timing of the easterly-to-westerly phase transitions displays considerable variability among the different reanalyses and this spread is much larger than for the timing of the westerly-to-easterly phase changes. The eddy component in the monthly-mean zonal wind near the Equator is dominated by zonal wavenumber 1 and 2 quasi-stationary planetary waves propagating from midlatitudes in the westerly phase of the QBO. There generally is considerable disagreement among the reanalyses in the details of the quasi-stationary waves near the Equator. At each level, there is a tendency for the agreement to be best near the longitude of Singapore, suggesting that the Singapore observations act as a strong constraint on all the reanalyses. Our measures of the quality of the reanalysis clearly show systematic improvement over the period considered (1979–2012). The SD among the reanalysis declines significantly over the record, although the geographical pattern of SD remains nearly constant.

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The sunspot cycle, the QBO, and the total ozone over Northeastern Europe: a connection through the dynamics of stratospheric circulation

Annales Geophysicae ◽

10.1007/s00585-997-1595-8 ◽

1997 ◽

Vol 15 (12) ◽

pp. 1595-1603 ◽

Cited By ~ 11

Author(s):

B. Soukharev

Keyword(s):

Solar Cycle ◽

Zonal Wind ◽

Total Ozone ◽

Sunspot Cycle ◽

Correlation Method ◽

Quasi Biennial Oscillation ◽

Sunspot Numbers ◽

Stratospheric Circulation ◽

Solar Signal ◽

Northeastern Europe

Abstract. The interaction between the factors of the quasi-biennial oscillation (QBO) and the 11-year solar cycle is considered as an separate factor influencing the interannual January-March variations of total ozone over Northeastern Europe. Linear correlation analysis and the running correlation method are used to examine possible connections between ozone and solar activity at simultaneous moment the QBO phase. Statistically significant correlations between the variations of total ozone in February and, partially, in March, and the sunspot numbers during the different phases of QBO are found. The running correlation method between the ozone and the equatorial zonal wind demonstrates a clear modulation of 11-y solar signal for February and March. Modulation is clearer if the QBO phases are defined at the level of 50 hPa rather than at 30 hPa. The same statistical analyses are conducted also for possible connections between the index of stratospheric circulation C1 and sunspot numbers considering the QBO phase. Statistically significant connections are found for February. The running correlations between the index C1 and the equatorial zonal wind show the clear modulation of 11-y solar signal for February and March. Based on the obtained correlations between the interannual variations of ozone and index C1, it may be concluded that a connection between solar cycle – QBO – ozone occurs through the dynamics of stratospheric circulation.

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SAR-retrieved wind in polar regions-comparison with in situ data and atmospheric model output

IEEE Transactions on Geoscience and Remote Sensing ◽

10.1109/tgrs.2002.802509 ◽

2002 ◽

Vol 40 (8) ◽

pp. 1720-1732 ◽

Cited By ~ 20

Author(s):

B.R. Furevik ◽

O.M. Johannessen ◽

A.D. Sandvik

Keyword(s):

Atmospheric Model ◽

Polar Regions ◽

Model Output ◽

In Situ Data

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Future Changes in the Ozone Quasi-Biennial Oscillation with Increasing GHGs and Ozone Recovery in CCMI Simulations

Journal of Climate ◽

10.1175/jcli-d-16-0464.1 ◽

2017 ◽

Vol 30 (17) ◽

pp. 6977-6997 ◽

Cited By ~ 4

Author(s):

Hiroaki Naoe ◽

Makoto Deushi ◽

Kohei Yoshida ◽

Kiyotaka Shibata

Keyword(s):

Zonal Wind ◽

Climate Model ◽

Vertical Shear ◽

Quasi Biennial Oscillation ◽

The Past ◽

Meteorological Research Institute ◽

Climate Simulations ◽

The Future ◽

Ozone Depleting Substances ◽

Biennial Oscillation

The future quasi-biennial oscillation (QBO) in ozone in the equatorial stratosphere is examined by analyzing transient climate simulations due to increasing greenhouse gases (GHGs) and decreasing ozone-depleting substances under the auspices of the Chemistry–Climate Model Initiative. The future (1960–2100) and historical (1979–2010) simulations are conducted with the Meteorological Research Institute Earth System Model. Three climate periods, 1960–85 (past), 1990–2020 (present), and 2040–70 (future) are selected, corresponding to the periods before, during, and after ozone depletion. The future ozone QBO is characterized by increases in amplitude by 15%–30% at 5–10 hPa and decreases by 20%–30% at 40 hPa, compared with the past and present climates; the future and present ozone QBOs increase in amplitude by up to 60% at 70 hPa, compared with the past climate. The increased amplitude at 5–10 hPa suggests that the temperature-dependent photochemistry plays an important role in the enhanced future ozone QBO. The weakening of vertical shear in the zonal wind QBO is responsible for the decreased amplitude at 40 hPa in the future ozone QBO. An interesting finding is that the weakened zonal wind QBO in the lowermost tropical stratosphere is accompanied by amplified QBOs in ozone, vertical velocity, and temperature. Further study is needed to elucidate the causality of amplification about the ozone and temperature QBOs under climate change in conditions of zonal wind QBO weakening.

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