scholarly journals Migrating and non-migrating tides observed in the stratosphere from FORMOSAT-3/COSMIC temperature retrievals

2020 ◽  
Vol 38 (2) ◽  
pp. 421-435 ◽  
Author(s):  
Uma Das ◽  
William E. Ward ◽  
Chen Jeih Pan ◽  
Sanat Kumar Das
Keyword(s):  
Planetary Wave ◽  
Middle Atmosphere ◽  
High Latitudes ◽  
Sudden Stratospheric Warming ◽  
Short Term ◽  
The Mean ◽  
Tidal Variability ◽  
Using Data ◽  
Stationary Planetary Wave ◽  
Linear Interactions

Abstract. Formosa Satellite-3 and Constellation Observing System for Meteorology, Ionosphere and Climate (FORMOSAT-3/COSMIC) temperature data during October 2009–December 2010 are analysed for tides in the middle atmosphere from ∼10 to 50 km. COSMIC is a set of six micro-satellites in near-Sun-synchronous orbits with 30∘ orbital separations that provides good phase space sampling of tides. Short-term tidal variability is deduced by considering ±10 d data together. The migrating diurnal (DW1) tide is found to peak over the Equator at 30 km. It maximises and slightly shifts poleward during winters. Over middle and high latitudes, DW1 and the non-migrating diurnal tides with wavenumber 0 (DS0) and wavenumber 2 (DW2) are intermittent in nature. Numerical experiments in the current study show that these could be a result of aliasing as they are found to occur at times of a steep rise or fall in the mean temperature, particularly during the sudden stratospheric warming (SSW) of 2010. Further, the stationary planetary wave component of wavenumber 1 (SPW1) is found to be of very large amplitudes in the Northern Hemisphere, reaching 18 K at 30 km over 65∘ N. By using data from COSMIC over shorter durations, it is shown that aliasing between stationary planetary wave and non-migrating tides is reduced and thus results in the large amplitudes of the former. This study clearly indicates that non-linear interactions are not a very important source for the generation of non-migrating tides in the middle- and high-latitude winter stratosphere. There is also a modulation of SPW1 by a ∼60 d oscillation in the high latitudes, which was not seen earlier.

scholarly journals Migrating and Non-Migrating Tides Observed in the Stratosphere from FORMOSAT-3/COSMIC Temperature Retrievals

2019 ◽  
Author(s):  
Uma Das ◽  
William Ward ◽  
Chen Jeih Pan ◽  
Sanat Kumar Das
Keyword(s):  
Planetary Wave ◽  
Middle Atmosphere ◽  
High Latitudes ◽  
Short Term ◽  
The Mean ◽  
Tidal Variability ◽  
Using Data ◽  
Stationary Planetary Wave ◽  
Linear Interactions ◽  
Winter Hemisphere

Abstract. FORMOSAT-3/COSMIC temperature data during 2009 to 2010 are analysed for tides in the middle atmosphere from ~ 10 to 50 km. COSMIC is a set of six micro satellites in near sun synchronous orbits with 30° orbital separations and provides good phase space sampling of tides. Short term tidal variability is deduced by considering ± 10 days' data together. The DW1 tide is found to peak over the equator at 30 km. It maximises and slightly shifts poleward during winters and thus is attributed to ozone absorption. Over mid and high latitudes, DW1 and the non-migrating tides DS0 and DW2 are intermittent in nature. Numerical experiments in the current study show that these could be a result of aliasing as they are found to occur at times of steep rise or fall in the mean temperature, particularly during the SSW of 2010. Further, stationary planetary wave components are found to be of very large amplitudes in the northern hemispheres reaching 18 K at 30 km over 65° N. By using data from COSMIC over shorter durations, aliasing between SPW and non-migrating tides is reduced and thus results in the large amplitudes of the former. This study clearly indicates that non-linear interactions are not a very important source of generation of the non migrating tides in the high latitude winter hemisphere. There is also a modulation of SPW1 by ~ 60 days in the high latitudes, which was not seen earlier.

scholarly journals Modelling the residual mean meridional circulation at different stages of sudden stratospheric warming events

2021 ◽  
Vol 39 (2) ◽  
pp. 357-368
Author(s):  
Andrey V. Koval ◽  
Wen Chen ◽  
Ksenia A. Didenko ◽  
Tatiana S. Ermakova ◽  
Nikolai M. Gavrilov ◽  
...  
Keyword(s):  
Planetary Wave ◽  
Polar Region ◽  
Meridional Circulation ◽  
Lower Thermosphere ◽  
High Latitudes ◽  
Sudden Stratospheric Warming ◽  
The North ◽  
Mean Meridional Circulation ◽  
The Mean ◽  
Wave Induced

Abstract. Ensemble simulation of the atmospheric general circulation at altitudes up to the lower thermosphere is performed using the 3-D nonlinear mechanistic numerical model MUAM. The residual mean meridional circulation (RMC), which is the superposition of the mean Eulerian and wave-induced eddy components, is calculated for the boreal winter. Changes in the vertical and meridional RMC velocity components are analysed at different stages of a simulated composite sudden stratospheric warming (SSW) event averaged over 19 model runs. The simulation results show a general decrease in RMC velocity components up to 30 % during and after SSW in the mesosphere and lower thermosphere of the Northern Hemisphere. There are also increases in the downward and northward velocities at altitudes of 20–50 km at the northern polar latitudes during SSW. Associated vertical transport and adiabatic heating can contribute to warming the stratosphere and downward shifting of the stratopause during the composite SSW. The residual mean and eddy mass fluxes are calculated for different SSW stages. It is shown that before the SSW, planetary wave activity creates wave-induced eddy circulation cells in the northern upper stratosphere, which are directed upwards at middle latitudes, northward at high latitudes and downwards near the North Pole. These cells increase heat transport and adiabatic heating in the polar region. During SSW, the region of upward eddy vertical velocity is shifted to high latitudes, but the velocity is still downward near the North Pole. After SSW, upward eddy-induced fluxes span the entire polar region, producing upward transport and adiabatic cooling of the stratosphere and providing the return of the stratopause to higher altitudes. The obtained statistically significant results on the evolution of RMC and eddy circulation at different SSW stages at altitudes up to the lower thermosphere can be useful for a better understanding the mechanisms of planetary wave impacts on the mean flow and for the diagnostics of the transport of conservative tracers in the atmosphere.

scholarly journals Statistics on Nonmigrating Diurnal Tides Generated by Tide-Planetary Wave Interaction and Their Relationship to Sudden Stratospheric Warming

Atmosphere ◽  
2018 ◽  
Vol 9 (11) ◽  
pp. 416 ◽  
Author(s):  
Xiaojuan Niu ◽  
Jian Du ◽  
Xuwen Zhu
Keyword(s):  
Planetary Wave ◽  
Middle Atmosphere ◽  
Wave Interaction ◽  
Diurnal Tide ◽  
Stratospheric Warming ◽  
Sudden Stratospheric Warming ◽  
Significant Difference ◽  
Polar Stratosphere ◽  
Stationary Planetary Wave ◽  
The Relationship

The nonmigrating diurnal tide, DW2, is known to have a source from the stationary planetary wave with wavenumber 1 (SPW1) and the migrating diurnal tide (DW1) interaction. Recent research has shown that DW2 time evolution in the equatorial mesopause tracks very well with SPW1 in the polar stratosphere for the winter of 2009–2010, which contains a sudden stratospheric warming (SSW) vortex split event. This paper extends previous research and investigates the relationship between these two waves for 31 winters from 1979 to 2010 with the extended Canadian Middle Atmosphere Model (eCMAM) through correlation and composite analysis. Significant correlations are present between the two waves in 20 out of 31 winters (65%). We separate the 31 winters into four categories: SSW-displacement, SSW-split, minor-SSW, and no-SSW. Our results show that there is no significant difference among the four categories in terms of correlations between the two waves. Although SPW1 is usually stronger during a SSW-D winter, this does not warrant a stronger interaction with DW2.

scholarly journals Characterizing the Variability and Extremes of the Stratospheric Polar Vortices Using 2D Moment Analysis

2011 ◽  
Vol 68 (6) ◽  
pp. 1194-1213 ◽  
Author(s):  
Daniel M. Mitchell ◽  
Andrew J. Charlton-Perez ◽  
Lesley J. Gray
Keyword(s):  
Extreme Value Theory ◽  
Planetary Wave ◽  
Value Theory ◽  
Extreme Value ◽  
Moment Analysis ◽  
Analysis Tool ◽  
Sudden Stratospheric Warming ◽  
Extreme Variability ◽  
The Mean ◽  
The Moment

Abstract The mean state, variability, and extreme variability of the stratospheric polar vortices, with an emphasis on the Northern Hemisphere (NH) vortex, are examined using two-dimensional moment analysis and extreme value theory (EVT). The use of moments as an analysis tool gives rise to information about the vortex area, centroid latitude, aspect ratio, and kurtosis. The application of EVT to these moment-derived quantities allows the extreme variability of the vortex to be assessed. The data used for this study are 40-yr ECMWF Re-Analysis (ERA-40) potential vorticity fields on interpolated isentropic surfaces that range from 450 to 1450 K. Analyses show that the most extreme vortex variability occurs most commonly in late January and early February, consistent with when most planetary wave driving from the troposphere is observed. Composites around sudden stratospheric warming (SSW) events reveal that the moment diagnostics evolve in statistically different ways between vortex splitting events and vortex displacement events, in contrast to the traditional diagnostics. Histograms of the vortex diagnostics on the 850-K (~10 hPa) surface over the 1958–2001 period are fitted with parametric distributions and show that SSW events constitute the majority of data in the tails of the distributions. The distribution of each diagnostic is computed on various surfaces throughout the depth of the stratosphere; it shows that in general the vortex becomes more circular with higher filamentation at the upper levels. The Northern and Southern Hemisphere (SH) vortices are also compared through the analysis of their respective vortex diagnostics, confirming that the SH vortex is less variable and lacks extreme events compared to the NH vortex. Finally, extreme value theory is used to statistically model the vortex diagnostics and make inferences about the underlying dynamics of the polar vortices.

QBO, ENSO and Solar Cycle Effects in Short-term Nonmigrating Tidal Variability on Planetary Wave Timescales from SABER - An Information-Theoretic Approach

2020 ◽  
Author(s):  
Komal Kumari ◽  
Jens Oberheide
Keyword(s):  
Solar Cycle ◽  
Planetary Wave ◽  
Wave Number ◽  
Atmospheric Tides ◽  
Theoretic Approach ◽  
Short Term ◽  
Quasi Biennial Oscillation ◽  
Information Theoretic ◽  
Leibler Divergence ◽  
Tidal Variability

<p>Earth’s atmosphere supports a variety of internal wave motion which are responsible for spatio-temporal changes in temperature, winds, density, and chemical constituents. One of the most striking dynamical features of the upper atmosphere (i.e. mesosphere and lower thermosphere [MLT], 50-120 km) are atmospheric tides. In particular, the eastward-propagating nonmigrating diurnal tide with zonal wave number 3 (DE3), originating from tropical deep convection, introduces a large longitudinal and local time variability in temperature, wind and density in the MLT region. The DE3 is thus key to understanding how tropospheric weather influences space weather. However, DE3 short-term tidal variability is not well understood and part of the motivation for constellation missions. Single satellites such as TIMED nevertheless provide a pathway to identify multi-timescale tidal variability from days to years. We utilize 16 years of SABER (an instrument onboard the TIMED satellite) DE3 “tidal deconvolution” diagnostic that provides a unique opportunity to investigate interannual changes in short-term (days to weeks) tidal variability on various planetary wave time scales. The approach is based on information-theoretic techniques using Bayesian statistics, time dependent probability density functions and Kullback-Leibler divergence followed by multiple linear regression analysis. In this presentation, we focus on interannual changes in short-term DE3 variability on a 10-day planetary wave timescale and how it changes as a function of the quasi-biennial oscillation (QBO), El Niño-Southern Oscillation (ENSO) and the solar cycle.</p>

Short term tidal variability in stratosphere using ERA-interim and CMAM temperature data and comparison with satellite retrievals

2021 ◽  
Author(s):  
Subhajit Debnath ◽  
Uma Das
Keyword(s):  
Middle Atmosphere ◽  
Window Size ◽  
Temperature Data ◽  
Short Term ◽  
Transform Method ◽  
Data Set ◽  
Linear Interaction ◽  
Non Linear ◽  
Tidal Variability ◽  
Short Term Variability

<p>A short term variability of migrating and non migrating tide is investigated in the stratosphere from the regular Canadian Middle Atmosphere Model (CMAM) and reanalysis ERA-interim temperature and wind dataset during winter of 2006 to 2010. Short term variability of tides is examined by ±10 day’s window size from Earth’s surface to 1hPa pressure level. To examine the short term variability of migrating and non migrating tide in stratosphere, we applied the fast fourier transform method to the CMAM30 and ERA-interim observation. The results reveal that tide changes with amplitude of 1-2K regularly on short timescales (21days) in stratosphere. Similar variability occurs in ERA-interim reanalysis observation. Non-migrating tide DS0 shows strong winter features with finer variation during 2009 and 2010 at 65°N. The short term variability of DE3 tide in stratosphere during 2008 and 2010 may be driven by zonal mean wind and non linear interaction with planetary wave. Amplitude of DW1 shows day to day variabilities clearly during winter of 2006, 2008 and 2009 at 0.7hPa over the equator and mid-latitude while the peak of DW1 is absent at 1hPa and 10hPa from CMAM temperature data set. Short term tidal variability in the stratosphere is not related to a single source. It depends on ozone density, zonal mean wind, and wave-wave non linear interactions. By using smaller window size, short term variabilities and finer variation of non migrating tides and SPW1 are understood. These results will be compared to results from satellite temperature data set, particularly FORMOSAT-3/COMSIC, for investigating short term tidal variability in the stratosphere.</p>

scholarly journals Interhemispheric structure and variability of the 5-day planetary wave from meteor radar wind measurements

2015 ◽  
Vol 33 (11) ◽  
pp. 1349-1359 ◽  
Author(s):  
H. Iimura ◽  
D. C. Fritts ◽  
D. Janches ◽  
W. Singer ◽  
N. J. Mitchell
Keyword(s):  
Interannual Variability ◽  
Southern Hemisphere ◽  
Planetary Wave ◽  
Tierra Del Fuego ◽  
Meteor Radar ◽  
Short Term ◽  
Simultaneous Measurements ◽  
Wind Measurements ◽  
Using Data ◽  
Northern And Southern Hemispheres

Abstract. A study of the quasi-5-day wave (5DW) was performed using meteor radars at conjugate latitudes in the Northern and Southern hemispheres. These radars are located at Esrange, Sweden (68° N) and Juliusruh, Germany (55° N) in the Northern Hemisphere, and at Tierra del Fuego, Argentina (54° S) and Rothera Station, Antarctica (68° S) in the Southern Hemisphere. The analysis was performed using data collected during simultaneous measurements by the four radars from June 2010 to December 2012 at altitudes from 84 to 96 km. The 5DW was found to exhibit significant short-term, seasonal, and interannual variability at all sites. Typical events had planetary wave periods that ranged between 4 and 7 days, durations of only a few cycles, and infrequent strongly peaked variances and covariances. Winds exhibited rotary structures that varied strongly among sites and between events, and maximum amplitudes up to ~ 20 m s−1. Mean horizontal velocity covariances tended to be largely negative at all sites throughout the interval studied.

Equatorial Superrotation and the Factors Controlling the Zonal-Mean Zonal Winds in the Tropical Upper Troposphere

2005 ◽  
Vol 62 (2) ◽  
pp. 371-389 ◽  
Author(s):  
Ian Kraucunas ◽  
Dennis L. Hartmann
Keyword(s):  
General Circulation ◽  
Planetary Wave ◽  
Upper Troposphere ◽  
Vertical Advection ◽  
Zonal Winds ◽  
Wave Response ◽  
Momentum Fluxes ◽  
The Mean ◽  
Stationary Planetary Wave ◽  
Tropical Upper Troposphere

Abstract The response of the zonal-mean zonal winds in the tropical upper troposphere to thermal forcing in the Tropics is studied using an idealized general circulation model with 18 vertical levels and simplified atmospheric physics. The model produces a conventional general circulation, with deep easterly flow over the equator, when integrated using zonally invariant and hemispherically symmetric boundary conditions, but persistent equatorial superrotation (westerly zonal-mean flow over the equator) is obtained when steady longitudinal variations in diabatic heating are imposed at low latitudes. The superrotation is driven by horizontal eddy momentum fluxes associated with the stationary planetary wave response to the applied tropical heating. The strength of the equatorial westerlies is ultimately limited by vertical steady eddy momentum fluxes, which are downward in the tropical upper troposphere, and by the zonally averaged circulation in the meridional plane, which erodes the mean westerly shear via vertical advection. The transition to superrotation can be prevented by specifying offsetting zonally invariant heating and cooling anomalies on either side of the equator to create a “solstitial” basic state with a single dominant Hadley cell straddling the equator. Superrotation is restricted in the solstitial climate because the strength of the mean meridional overturning is enhanced, which increases the efficiency of vertical advection, and because the cross-equatorial flow in the upper troposphere provides an easterly zonal acceleration that offsets some of the momentum flux convergence associated with tropical eddy heating. The cross-equatorial flow aloft also reduces the stationary planetary wave response in the summer hemisphere. These results suggest that hemispheric asymmetry in the mean meridional circulation is responsible for maintaining the observed mean easterly flow in the tropical upper troposphere against the westerly torques associated with tropical wave sources.

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