scholarly journals Structure and Dynamics of the Quasi-Biennial Oscillation in MERRA-2

2016 ◽  
Vol 29 (14) ◽  
pp. 5339-5354 ◽  
Author(s):  
Lawrence Coy ◽  
Krzysztof Wargan ◽  
Andrea M. Molod ◽  
William R. McCarty ◽  
Steven Pawson
Keyword(s):  
Meridional Circulation ◽  
Wave Drag ◽  
Quasi Biennial Oscillation ◽  
Zonal Winds ◽  
Time Period ◽  
Mean Meridional Circulation ◽  
Downward Propagation ◽  
Phase Amplitude ◽  
Modern Era ◽  
Biennial Oscillation

Abstract The structure, dynamics, and ozone signal of the quasi-biennial oscillation (QBO) produced by the 35-yr NASA Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2), are examined based on monthly mean output. Along with the analysis of the QBO in assimilation winds and ozone, the QBO forcings created by assimilated observations, dynamics, parameterized gravity wave drag (GWD), and ozone chemistry parameterization are examined and compared with the original MERRA system. Results show that MERRA-2 produces a realistic QBO in the zonal winds, mean meridional circulation, and ozone over the 1980–2015 time period. In particular, the MERRA-2 zonal winds show improved representation of the QBO 50-hPa westerly phase amplitude at Singapore when compared to MERRA. The use of limb ozone observations creates improved vertical structure and realistic downward propagation of the ozone QBO signal during times when the MLS ozone limb observations are available (from October 2004 to present). The increased equatorial GWD in MERRA-2 has reduced the zonal wind data analysis contribution compared to MERRA so that the QBO mean meridional circulation can be expected to be more physically forced and therefore more physically consistent. This can be important for applications in which MERRA-2 winds are used to drive transport experiments.

scholarly journals Constraints on Wave Drag Parameterization Schemes for Simulating the Quasi-Biennial Oscillation. Part I: Gravity Wave Forcing

2005 ◽  
Vol 62 (12) ◽  
pp. 4178-4195 ◽  
Author(s):  
Lucy J. Campbell ◽  
Theodore G. Shepherd
Keyword(s):  
Gravity Wave ◽  
Zonal Wind ◽  
Shear Zones ◽  
Wave Drag ◽  
Planetary Waves ◽  
Vertical Diffusion ◽  
Quasi Biennial Oscillation ◽  
Parameterization Schemes ◽  
Downward Propagation ◽  
Biennial Oscillation

Abstract Parameterization schemes for the drag due to atmospheric gravity waves are discussed and compared in the context of a simple one-dimensional model of the quasi-biennial oscillation (QBO). A number of fundamental issues are examined in detail, with the goal of providing a better understanding of the mechanism by which gravity wave drag can produce an equatorial zonal wind oscillation. The gravity wave–driven QBOs are compared with those obtained from a parameterization of equatorial planetary waves. In all gravity wave cases, it is seen that the inclusion of vertical diffusion is crucial for the descent of the shear zones and the development of the QBO. An important difference between the schemes for the two types of waves is that in the case of equatorial planetary waves, vertical diffusion is needed only at the lowest levels, while for the gravity wave drag schemes it must be included at all levels. The question of whether there is downward propagation of influence in the simulated QBOs is addressed. In the gravity wave drag schemes, the evolution of the wind at a given level depends on the wind above, as well as on the wind below. This is in contrast to the parameterization for the equatorial planetary waves in which there is downward propagation of phase only. The stability of a zero-wind initial state is examined, and it is determined that a small perturbation to such a state will amplify with time to the extent that a zonal wind oscillation is permitted.

scholarly journals Net influence of an internally generated quasi-biennial oscillation on modelled stratospheric climate and chemistry

2013 ◽  
Vol 13 (24) ◽  
pp. 12187-12197 ◽  
Author(s):  
M. M. Hurwitz ◽  
L. D. Oman ◽  
P. A. Newman ◽  
I.-S. Song
Keyword(s):  
Climate Model ◽  
Stratospheric Ozone ◽  
Wave Drag ◽  
Relative Increase ◽  
Meridional Overturning Circulation ◽  
Overturning Circulation ◽  
Quasi Biennial Oscillation ◽  
Zonal Winds ◽  
Biennial Oscillation ◽  
Stratospheric Variability

Abstract. A Goddard Earth Observing System Chemistry-Climate Model (GEOSCCM) simulation with strong tropical non-orographic gravity wave drag (GWD) is compared to an otherwise identical simulation with near-zero tropical non-orographic GWD. The GEOSCCM generates a quasi-biennial oscillation (QBO) zonal wind signal in response to a tropical peak in GWD that resembles the zonal and climatological mean precipitation field. The modelled QBO has a frequency and amplitude that closely resembles observations. As expected, the modelled QBO improves the simulation of tropical zonal winds and enhances tropical and subtropical stratospheric variability. Also, inclusion of the QBO slows the meridional overturning circulation, resulting in a generally older stratospheric mean age of air. Slowing of the overturning circulation, changes in stratospheric temperature and enhanced subtropical mixing all affect the annual mean distributions of ozone, methane and nitrous oxide. Furthermore, the modelled QBO enhances polar stratospheric variability in winter. Because tropical zonal winds are easterly in the simulation without a QBO, there is a relative increase in tropical zonal winds in the simulation with a QBO. Extratropical differences between the simulations with and without a QBO thus reflect the westerly shift in tropical zonal winds: a relative strengthening of the polar stratospheric jet, polar stratospheric cooling and a weak reduction in Arctic lower stratospheric ozone.

scholarly journals Variability in the speed of the Brewer–Dobson circulation as observed by Aura/MLS

2013 ◽  
Vol 13 (9) ◽  
pp. 4563-4575 ◽  
Author(s):  
T. Flury ◽  
D. L. Wu ◽  
W. G. Read
Keyword(s):  
Time Series ◽  
Interannual Variability ◽  
Lower Stratosphere ◽  
Meridional Circulation ◽  
Time Lag ◽  
Quasi Biennial Oscillation ◽  
One Year ◽  
The Tropics ◽  
Biennial Oscillation ◽  
Stratospheric Water Vapour

Abstract. We use Aura/MLS stratospheric water vapour (H2O) measurements as tracer for dynamics and infer interannual variations in the speed of the Brewer–Dobson circulation (BDC) from 2004 to 2011. We correlate one-year time series of H2O in the lower stratosphere at two subsequent pressure levels (68 hPa, ~18.8 km and 56 hPa, ~19.9 km at the Equator) and determine the time lag for best correlation. The same calculation is made on the horizontal on the 100 hPa (~16.6 km) level by correlating the H2O time series at the Equator with the ones at 40° N and 40° S. From these lag coefficients we derive the vertical and horizontal speeds of the BDC in the tropics and extra-tropics, respectively. We observe a clear interannual variability of the vertical and horizontal branch. The variability reflects signatures of the Quasi Biennial Oscillation (QBO). Our measurements confirm the QBO meridional circulation anomalies and show that the speed variations in the two branches of the BDC are out of phase and fairly well anti-correlated. Maximum ascent rates are found during the QBO easterly phase. We also find that transport of H2O towards the Northern Hemisphere (NH) is on the average two times faster than to the Southern Hemisphere (SH) with a mean speed of 1.15 m s−1 at 100 hPa. Furthermore, the speed towards the NH shows much more interannual variability with an amplitude of about 21% whilst the speed towards the SH varies by only 10%. An amplitude of 21% is also observed in the variability of the ascent rate at the Equator which is on the average 0.2 mm s−1.

scholarly journals Stratospheric semi-decadal oscillations in NCEP data

2008 ◽  
Vol 26 (8) ◽  
pp. 2143-2157 ◽  
Author(s):  
H. G. Mayr ◽  
J. G. Mengel ◽  
F. T. Huang ◽  
E. R. Talaat ◽  
E. R. Nash ◽  
...  
Keyword(s):  
Spectral Analysis ◽  
Data Analysis ◽  
Temperature Data ◽  
Spectral Features ◽  
Altitude Range ◽  
Quasi Biennial Oscillation ◽  
Atmospheric Research ◽  
Zonal Winds ◽  
Environmental Prediction ◽  
Biennial Oscillation

Abstract. An analysis of the National Centers for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) data is presented to provide a more complete description of the stratospheric 5-year semi-decadal (SD) oscillation (Mayr et al., 2007). The zonal-mean temperature and zonal wind data from the Atmospheric Research R-1 analysis are employed, covering the years from 1962 to 2002 in the altitude range from 10 to 30 km. For diagnostic purposes, the data are separated into the hemispherically symmetric and anti-symmetric components, and spectral analysis is applied to identify the signatures of the SD oscillations. Through the synthesis or filtering of spectral features, the SD modulations of the annual oscillation (AO) and quasi-biennial oscillation (QBO) are delineated. In agreement with the earlier findings, the magnitude of the SD oscillation is more pronounced when the 30-month QBO dominates during the years from 1975 to 1995. This is consistent with results from a numerical model, which shows that such a QBO generates the SD oscillation through interaction with the 12-month AO. In the zonal winds, the SD oscillation in the NCEP data is confined to equatorial latitudes, where it modulates the symmetric AO and QBO by about 5 m/s below 30 km. In the temperature data, the effect is also seen around the equator, but it is much larger at polar latitudes where the SD oscillation produces variations as large as 2 K. Our data analysis indicates that the SD oscillation is mainly hemispherically symmetric, and it appears to originate at equatorial latitudes where most of the energy resides.

scholarly journals Global Balanced Wind Derived from SABER Temperature and Pressure Observations and its Validations

2021 ◽  
Author(s):  
Xiao Liu ◽  
Jiyao Xu ◽  
Jia Yue ◽  
You Yu ◽  
Paulo P. Batista ◽  
...  
Keyword(s):  
Zonal Wind ◽  
Meteor Radar ◽  
Quasi Biennial Oscillation ◽  
Height Range ◽  
Zonal Winds ◽  
Wind Theory ◽  
Temperature And Pressure ◽  
Identical Zero ◽  
Biennial Oscillation ◽  
Good Agreement

Abstract. Zonal winds in the stratosphere and mesosphere play important roles in the atmospheric dynamics and aeronomy. However, the direct measurement of winds in this height range is difficult. We present a dataset of the monthly mean zonal wind in the height range of 18–100 km and at latitudes of 50° S–50° N from 2002 to 2019, which is derived by the gradient balance wind theory and the temperature and pressure observed by the SABER instrument. The tide alias above 80 km at the equator is replaced by the monthly mean zonal wind measured by a meteor radar at 0.2° S. The dataset (named as BU) is validated by comparing with the zonal wind from MERRA2 (MerU), UARP (UraU), HWM14 empirical model (HwmU), meteor radar (MetU) and lidar (LidU) at seven stations from 53.5° N to 29.7° S. At 18–70 km, BU and MerU have (1) nearly identical zero wind lines, (2) year-to-year variations of the eastward/westward wind jets at middle and high latitudes, (3) the quasi-biennial oscillation (QBO) and semi-annual oscillation (SAO), especially the anormal QBO in early 2016. The comparisons among BU, UraU and HwmU show good agreement in general below 80 km. Above 80 km, the agreements among BU, UraU, HwmU, MetU and LidU are good in general, except some discrepancies at limited heights and months. The BU data are archived as netCDF files and can be available at https://dx.doi.org/10.12176/01.99.00574 (Liu et al., 2021). 

scholarly journals Net influence of an internally-generated QBO on modelled stratospheric climate and chemistry

2013 ◽  
Vol 13 (5) ◽  
pp. 13495-13518
Author(s):  
M. M. Hurwitz ◽  
L. D. Oman ◽  
P. A. Newman ◽  
I.-S. Song
Keyword(s):  
Climate Model ◽  
Stratospheric Ozone ◽  
Wave Drag ◽  
Relative Increase ◽  
Meridional Overturning Circulation ◽  
Overturning Circulation ◽  
Quasi Biennial Oscillation ◽  
Zonal Winds ◽  
Stratospheric Temperature ◽  
Stratospheric Variability

Abstract. A Goddard Earth Observing System Chemistry–Climate Model (GEOSCCM) simulation with strong tropical non-orographic gravity wave drag (GWD) is compared to an otherwise identical simulation with near-zero tropical non-orographic GWD. The GEOSCCM generates a quasi-biennial oscillation (QBO) zonal wind signal in response to strong, quasi-realistic tropical GWD. The modelled QBO has a frequency and amplitude that closely resembles observations. In the annual mean, the modelled QBO improves the simulation of tropical zonal winds and enhances tropical and sub-tropical stratospheric variability. Also, inclusion of the QBO slows the meridional overturning circulation, resulting in a generally older stratospheric mean age-of-air. Slowing of the overturning circulation, changes in stratospheric temperature and enhanced sub-tropical mixing all affect the mean distributions of ozone, methane and nitrous oxide. Furthermore, the modelled QBO enhances polar stratospheric variability in winter. Because tropical zonal winds are easterly in the simulation without a QBO, there is a relative increase in tropical zonal winds in the simulation with a QBO. Extra-tropical differences between the simulations with and without a QBO thus reflect a bias toward the westerly phase of the QBO: a relative strengthening of the polar stratospheric jet, polar stratospheric cooling and a weak reduction in Arctic lower stratospheric ozone.

scholarly journals The middle atmospheric meridional circulation for 2002–2012 derived from MIPAS observations

2021 ◽  
Vol 21 (11) ◽  
pp. 8823-8843
Author(s):  
Thomas von Clarmann ◽  
Udo Grabowski ◽  
Gabriele P. Stiller ◽  
Beatriz M. Monge-Sanz ◽  
Norbert Glatthor ◽  
...  
Keyword(s):  
Meridional Circulation ◽  
Trace Gases ◽  
Michelson Interferometer ◽  
Velocity Fields ◽  
Fickian Diffusion ◽  
Quasi Biennial Oscillation ◽  
Data Set ◽  
Effective Velocity ◽  
Mean Meridional Circulation ◽  
Stratospheric Circulation

Abstract. Measurements of long-lived trace gases (SF6, CFC-11, CFC-12, HCFC-22, CCl4, N2O, CH4, H2O, and CO) performed with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) have been used to infer the stratospheric and mesospheric meridional circulation. The MIPAS data set covers the time period from July 2002 to April 2012. The method used for this purpose was the direct inversion of the two-dimensional continuity equation for the concentrations of trace gases and air density. This inversion predicts an “effective velocity” that gives the best fit for the evolution of the concentrations on the assumption that an explicit treatment of Fickian diffusion can be neglected. These effective velocity fields are used to characterize the mean meridional circulation. Multiannual monthly mean effective velocity fields are presented, along with their variabilities. According to this measure, the stratospheric circulation is found to be highly variable over the year, with a quite robust annual cycle. The new method allows us to track the evolution of various circulation patterns over the year in more detail than before. According to the effective velocity characterization of the circulation, the deep branch of the Brewer–Dobson circulation and the mesospheric overturning pole-to-pole circulation are not separate but intertwined phenomena. The latitude of stratospheric uplift in the middle and upper stratosphere is found to be quite variable and is not always found at equatorial latitudes. The usual schematic of stratospheric circulation with the deep and the shallow branch of the Brewer–Dobson circulation and the mesospheric overturning circulation is an idealization which best describes the observed atmosphere around equinox. Sudden stratospheric warmings and the quasi-biennial oscillation cause a pronounced year-to-year variability of the meridional circulation.

scholarly journals The Seasonal Cycle of Gravity Wave Drag in the Middle Atmosphere

2008 ◽  
Vol 21 (18) ◽  
pp. 4664-4679 ◽  
Author(s):  
Manuel Pulido ◽  
John Thuburn
Keyword(s):  
Gravity Wave ◽  
Seasonal Cycle ◽  
Middle Atmosphere ◽  
Three Dimensional ◽  
Wave Drag ◽  
Smooth Transition ◽  
Quasi Biennial Oscillation ◽  
Summer Hemisphere ◽  
Jet Streaks ◽  
Biennial Oscillation

Abstract Using a variational technique, middle atmosphere gravity wave drag (GWD) is estimated from Met Office middle atmosphere analyses for the year 2002. The technique employs an adjoint model of a middle atmosphere dynamical model to minimize a cost function that measures the differences between the model state and observations. The control variables are solely the horizontal components of GWD; therefore, the minimization determines the optimal estimate of the drag. For each month, Met Office analyses are taken as the initial condition for the first day of the month, and also as observations for each successive day. In this way a three-dimensional GWD field is obtained for the entire year with a temporal resolution of 1 day. GWD shows a pronounced seasonal cycle. During solstices, there are deceleration regions of the polar jet centered at about 63° latitude in the winter hemisphere, with a peak of 49 m s−1 day−1 at 0.24 hPa in the Southern Hemisphere; the summer hemisphere also shows a deceleration region but much weaker, with a peak of 24 m s−1 day−1 centered at 45° latitude and 0.6 hPa. During equinoxes GWD is weak and exhibits a smooth transition between the winter and summer situation. The height and latitude of the deceleration center in both winter and summer hemispheres appear to be constant. Important longitudinal dependencies in GWD are found that are related to planetary wave activity; GWD intensifies in the exit region of jet streaks. In the lower tropical stratosphere, the estimated GWD shows a westward GWD descending together with the westward phase of the quasi-biennial oscillation. Above, GWD exhibits a semiannual pattern that is approximately out of phase with the semiannual oscillation in the zonal wind. Furthermore, a descending GWD pattern is found at those heights, similar in magnitude and sign to that in the lower stratosphere.

Development of the Extratropical Response to the Stratospheric Quasi-Biennial Oscillation

2021 ◽  
pp. 1-44
Author(s):  
Jian Rao ◽  
Chaim I. Garfinkel ◽  
Ian P. White
Keyword(s):  
Climate Models ◽  
Meridional Circulation ◽  
Polar Vortex ◽  
Late Winter ◽  
Flux Divergence ◽  
Quasi Biennial Oscillation ◽  
Atlantic Sector ◽  
Near Surface ◽  
Surface Response ◽  
Biennial Oscillation

AbstractUsing the Model of an Idealized Moist Atmosphere (MiMA) capable of spontaneously generating a Quasi-Biennial Oscillation (QBO), the gradual establishment of the extratropical response to the QBO is explored. The period and magnitude of the QBO and the magnitude of the polar Holton-Tan (HT) relationship is simulated in a free-running configuration of MiMA, comparable to that in state-of-the-art climate models. In order to isolate mechanisms whereby the QBO influences variability outside of the tropical atmosphere, a series of branch experiments are performed with nudged QBO winds. When easterly QBO winds maximized around 30 hPa are relaxed, an Eliassen-Palm (E-P) flux divergence dipole quickly forms in the extratropical middle stratosphere as a direct response to the tropical meridional circulation, in contrast to the HT mechanism which is associated with wave propagation near the zero wind line. This meridional circulation response to the relaxed QBO winds develops within the first 10 days in seasonally-varying and fixed-seasonal experiments. No detectable changes in upward propagation of waves in the midlatitude lowermost stratosphere are evident for at least 20 days after branching, with the first changes only evident after 20 days in perpetual midwinter and season-varying runs, but after 40 days in perpetual November runs. The polar vortex begins to respond around the 20th day, and subsequently a near-surface response in the Atlantic sector forms in mid-to-late winter runs. These results suggest that the maximum near-surface response observed in mid-to-late winter is not simply due to a random seasonal synchronization of the QBO phase, but also due to the long (short) lag of the surface response to a QBO relaxation in early (mid-to-late) winter.

Sign in / Sign up

Export Citation Format

Share Document