Zonal Wave Number Diagnosis of Rossby Wave‐Like Oscillations Using Paired Ground‐Based Radars

Abstract. In this paper we present a simple analytical model for low frequency and large scale variability of the Antarctic Circumpolar Current (ACC). The physical mechanism of the variability is related to temporal and spatial variations of the cyclonic mean flow (ACC) due to circularly propagating nonlinear barotropic Rossby wave trains. It is shown that the Rossby wave train is a fundamental mode, trapped between the major fronts in the ACC. The Rossby waves are predicted to rotate with a particular angular velocity that depends on the magnitude and width of the mean current. The spatial structure of the rotating pattern, including its zonal wave number, is defined by the specific form of the stream function-vorticity relation. The similarity between the simulated patterns and the Antarctic Circumpolar Wave (ACW) is highlighted. The model can predict the observed sequence of warm and cold patches in the ACW as well as its zonal number.

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Investigation of dominant traveling 10-day wave components using long-term MERRA-2 database

Earth Planets and Space ◽

10.1186/s40623-021-01410-7 ◽

2021 ◽

Vol 73 (1) ◽

Author(s):

Chunming Huang ◽

Wei Li ◽

Shaodong Zhang ◽

Gang Chen ◽

Kaiming Huang ◽

...

Keyword(s):

Flow Instability ◽

Transmission Condition ◽

Wave Number ◽

Mean Flow ◽

Excited Wave ◽

Propagating Waves ◽

Zonal Wave Number ◽

The Mean

AbstractThe eastward- and westward-traveling 10-day waves with zonal wavenumbers up to 6 from surface to the middle mesosphere during the recent 12 years from 2007 to 2018 are deduced from MERRA-2 data. On the basis of climatology study, the westward-propagating wave with zonal wave number 1 (W1) and eastward-propagating waves with zonal wave numbers 1 (E1) and 2 (E2) are identified as the dominant traveling ones. They are all active at mid- and high-latitudes above the troposphere and display notable month-to-month variations. The W1 and E2 waves are strong in the NH from December to March and in the SH from June to October, respectively, while the E1 wave is active in the SH from August to October and also in the NH from December to February. Further case study on E1 and E2 waves shows that their latitude–altitude structures are dependent on the transmission condition of the background atmosphere. The presence of these two waves in the stratosphere and mesosphere might have originated from the downward-propagating wave excited in the mesosphere by the mean flow instability, the upward-propagating wave from the troposphere, and/or in situ excited wave in the stratosphere. The two eastward waves can exert strong zonal forcing on the mean flow in the stratosphere and mesosphere in specific periods. Compared with E2 wave, the dramatic forcing from the E1 waves is located in the poleward regions.

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Comparison of Key Characteristics of Remarkable SSW Events in the Southern and Northern Hemisphere

10.5194/egusphere-egu21-7702 ◽

2021 ◽

Author(s):

Michal Kozubek ◽

Peter Krizan

Keyword(s):

Northern Hemisphere ◽

Planetary Wave ◽

Polar Vortex ◽

Wave Number ◽

Strong Activity ◽

Key Characteristics ◽

Zonal Wave Number ◽

Show Difference ◽

Temperature Enhancement ◽

Stationary Planetary Wave

<p>An exceptionally strong sudden stratospheric warming (SSW) in the Southern Hemisphere (SH) during September 2019 was observed. Because SSW in the SH is very rare, comparison with the only recorded major SH SSW is done. According to World Meteorological Organization (WMO) definition, the SSW in 2019 has to be classified as minor. The cause of SSW in 2002 was very strong activity of stationary planetary wave with zonal wave-number (ZW) 2, which reached its maximum when the polar vortex split into two circulations with polar temperature enhancement by 30 K/week and it penetrated deeply to the lower stratosphere and upper troposphere. On the other hand, the minor SSW in 2019 involved an exceptionally strong wave-1 planetary wave and a large polar temperature enhancement by 50.8 K/week, but it affected mainly the middle and upper stratosphere. The strongest SSW in the Northern Hemisphere was observed in 2009. This study provides comparison of two strongest SSW in the SH and the strongest SSW in the NH to show difference between two hemispheres and possible impact to the lower or higher layers.</p>

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Investigation of the Occurrence of Nighttime Topside Ionospheric Irregularities in Low-Latitude and Equatorial Regions Using CYGNSS Satellites

Sensors ◽

10.3390/s20030708 ◽

2020 ◽

Vol 20 (3) ◽

pp. 708 ◽

Cited By ~ 1

Author(s):

Liang Huang ◽

Yi Liu ◽

Qiong Tang ◽

Guanyi Chen ◽

Zhuangkai Wang ◽

...

Keyword(s):

Signal To Noise Ratio ◽

Global Analysis ◽

Satellite System ◽

Ionospheric Irregularities ◽

Wave Number ◽

Significant Finding ◽

Low Latitude ◽

Zonal Wave Number ◽

Global Navigation Satellite ◽

Maximum Occurrence

By using multi-satellite observations of the L1 signal-to-noise ratio (SNR) from the Cyclone Global Navigation Satellite System (CYGNSS) taken in 2017, we present the occurrence of nighttime topside ionospheric irregularities in low-latitude and equatorial regions. The most significant finding of this study is the existence of longitudinal structures with a wavenumber 4 pattern in the topside irregularities. This suggests that lower atmospheric waves, especially a daytime diurnal eastward-propagating zonal wave number-3 nonmigrating tide (DE3), might play an important role in the generation of topside plasma bubbles during the low solar minimum. Observations of scintillation events indicate that the maximum occurrence of nighttime topside ionospheric irregularities occurs on the magnetic equator during the equinoxes. The current work, which could be regarded as an important update of the previous investigations, would be readily for the further global analysis of the topside ionospheric irregularities.

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Propagation properties of Rossby waves for latitudinal β-plane variations of <I>f</I> and zonal variations of the shallow water speed

Annales Geophysicae ◽

10.5194/angeo-30-849-2012 ◽

2012 ◽

Vol 30 (5) ◽

pp. 849-855 ◽

Cited By ~ 5

Author(s):

C. T. Duba ◽

J. F. McKenzie

Keyword(s):

Shallow Water ◽

Group Velocity ◽

Rossby Wave ◽

Rossby Waves ◽

Low Frequency ◽

Wave Number ◽

Coriolis Parameter ◽

Propagation Properties ◽

Wave Normal ◽

Water Speed

Abstract. Using the shallow water equations for a rotating layer of fluid, the wave and dispersion equations for Rossby waves are developed for the cases of both the standard β-plane approximation for the latitudinal variation of the Coriolis parameter f and a zonal variation of the shallow water speed. It is well known that the wave normal diagram for the standard (mid-latitude) Rossby wave on a β-plane is a circle in wave number (ky,kx) space, whose centre is displaced −β/2 ω units along the negative kx axis, and whose radius is less than this displacement, which means that phase propagation is entirely westward. This form of anisotropy (arising from the latitudinal y variation of f), combined with the highly dispersive nature of the wave, gives rise to a group velocity diagram which permits eastward as well as westward propagation. It is shown that the group velocity diagram is an ellipse, whose centre is displaced westward, and whose major and minor axes give the maximum westward, eastward and northward (southward) group speeds as functions of the frequency and a parameter m which measures the ratio of the low frequency-long wavelength Rossby wave speed to the shallow water speed. We believe these properties of group velocity diagram have not been elucidated in this way before. We present a similar derivation of the wave normal diagram and its associated group velocity curve for the case of a zonal (x) variation of the shallow water speed, which may arise when the depth of an ocean varies zonally from a continental shelf.

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The quasi-two-day wave studied using the Northern Hemisphere SuperDARN HF radars

Annales Geophysicae ◽

10.5194/angeo-25-1767-2007 ◽

2007 ◽

Vol 25 (8) ◽

pp. 1767-1778 ◽

Cited By ~ 17

Author(s):

S. B. Malinga ◽

J. M. Ruohoniemi

Keyword(s):

Northern Hemisphere ◽

Spectral Power ◽

Auroral Zone ◽

Meridional Flow ◽

Wave Activity ◽

Wave Number ◽

Strongly Correlated ◽

Mean Flow ◽

Abstract Data ◽

Zonal Wave Number

Abstract. Data from the Super Dual Radar Network (SuperDARN) radars for 2002 were used to study the behaviour of the quasi-two-day wave (QTDW) in the Northern Hemisphere auroral zone. The period of the QTDW is observed to vary in the range of ~42–56 h, with the most dominant period being ~48 h and secondary peaks at ~42- and ~52-h. The spectral power shows a seasonal variation with a peak power (max~70) in summer. The power shows variations of several days and there is also evidence of changes in wave strength with longitude. The 42-h and the 48-h components tend to be strongly correlated in summer. The onset of enhanced wave activity tends to coincide with the westward acceleration of the zonal mean flow and occurs at a time of strong southward meridional flow. The most frequent instantaneous hourly period is in the 40 to 50 h period band, in line with the simultaneous dominance of the 42-h and the 48-h components. The wave numbers are less variable and are around −2 to −4 during times of strong wave activity. For a period of ~48 h, the zonal wave number is about −3 to −4, using a negative value to indicate westward propagating waves. The 42-h and the 52-h components cover a wider band in the −4 to 1 range. The wide zonal wave number spectrum in our results may account for the observed longitudinal variation in the spectral power of the wave.

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Influence of the sudden stratospheric warming on quasi-2-day waves

Atmospheric Chemistry and Physics ◽

10.5194/acp-16-4885-2016 ◽

2016 ◽

Vol 16 (8) ◽

pp. 4885-4896 ◽

Cited By ~ 10

Author(s):

Sheng-Yang Gu ◽

Han-Li Liu ◽

Xiankang Dou ◽

Tao Li

Keyword(s):

General Circulation ◽

Phase Speed ◽

Circulation Model ◽

Meridional Wind ◽

Equatorial Region ◽

Wave Number ◽

Stratospheric Warming ◽

Sudden Stratospheric Warming ◽

Middle Latitudes ◽

Zonal Wave Number

Abstract. The influence of the sudden stratospheric warming (SSW) on a quasi-2-day wave (QTDW) with westward zonal wave number 3 (W3) is investigated using the Thermosphere–Ionosphere–Mesosphere Electrodynamics General Circulation Model (TIME-GCM). The summer easterly jet below 90 km is strengthened during an SSW, which results in a larger refractive index and thus more favorable conditions for the propagation of W3. In the winter hemisphere, the Eliassen–Palm (EP) flux diagnostics indicate that the strong instabilities at middle and high latitudes in the mesopause region are important for the amplification of W3, which is weakened during SSW periods due to the deceleration or even reversal of the winter westerly winds. Nonlinear interactions between the W3 and the wave number 1 stationary planetary wave produce QTDW with westward zonal wave number 2 (W2). The meridional wind perturbations of the W2 peak in the equatorial region, while the zonal wind and temperature components maximize at middle latitudes. The EP flux diagnostics indicate that the W2 is capable of propagating upward in both winter and summer hemispheres, whereas the propagation of W3 is mostly confined to the summer hemisphere. This characteristic is likely due to the fact that the phase speed of W2 is larger, and therefore its waveguide has a broader latitudinal extension. The larger phase speed also makes W2 less vulnerable to dissipation and critical layer filtering by the background wind when propagating upward.

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Investigation on the abnormal quasi-two day wave activities during sudden stratospheric warming period of January 2006

10.5194/acp-2017-563 ◽

2017 ◽

Cited By ~ 2

Author(s):

Sheng-Yang Gu ◽

Xiankang Dou ◽

Dora Pancheva

Keyword(s):

Planetary Wave ◽

Phase Speed ◽

Dominant Mode ◽

Wave Number ◽

Stratospheric Warming ◽

Mean Flow ◽

Sudden Stratospheric Warming ◽

Reanalysis Dataset ◽

Short Period ◽

Zonal Wave Number

Abstract. The quasi-two day wave (QTDW) during austral summer period usually coincides with sudden stratospheric warming (SSW) event in the winter hemisphere, while the influences of SSW on QTDW are not totally understood. In this work, the anomalous QTDW activities during the major SSW period of January 2006 are further investigated on the basis of hourly Navy Operational Global Atmospheric Prediction System-Advanced Level Physics High Altitude (NOGAPS-ALPHA) reanalysis dataset. Strong westward QTDW with zonal wave number 2 (W2) is identified besides the conventionally dominant mode of zonal wave number 3 (W3). Meanwhile, the W3 peaks with an extremely short period of ~ 42 hours. Compared with January 2005 with no evident SSW, we found that the zonal mean zonal wind in the summer mesosphere is enhanced during 2006. The enhanced summer easterly sustains critical layers for W2 and short-period W3 QTDWs with larger phase speed, which facilitate their amplification through wave-mean flow interaction. The stronger summer easterly also provides stronger barotropic/baroclinic instabilities and thus larger forcing for the amplification of QTDW. The inter-hemispheric coupling induced by strong winter stratospheric planetary wave activities during SSW period is most likely responsible for the enhancement of summer easterly. Besides, we found that the nonlinear interaction between W3 QTDW and the wave number 1 stationary planetary wave (SPW1) may also contribute to the source of W2 at middle and low latitudes in the mesosphere.

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Comparison of Key Characteristics of Remarkable SSW Events in the Southern and Northern Hemisphere

Atmosphere ◽

10.3390/atmos11101063 ◽

2020 ◽

Vol 11 (10) ◽

pp. 1063

Author(s):

Michal Kozubek ◽

Jan Lastovicka ◽

Peter Krizan

Keyword(s):

Northern Hemisphere ◽

Planetary Wave ◽

Polar Vortex ◽

Wave Number ◽

Strong Activity ◽

Key Characteristics ◽

Zonal Wave Number ◽

Show Difference ◽

Temperature Enhancement ◽

Stationary Planetary Wave

An exceptionally strong sudden stratospheric warming (SSW) in the Southern Hemisphere (SH) during September 2019 was observed. Because SSW in the SH is very rare, comparison with the only recorded major SH SSW is done. According to World Meteorological Organization (WMO) definition, the SSW in 2019 has to be classified as minor. The cause of SSW in 2002 was very strong activity of stationary planetary wave with zonal wave-number (ZW) 2, which reached its maximum when the polar vortex split into two circulations with polar temperature enhancement by 30 K/week and it penetrated deeply to the lower stratosphere and upper troposphere. On the other hand, the minor SSW in 2019 involved an exceptionally strong wave-1 planetary wave and a large polar temperature enhancement by 50.8 K/week, but it affected mainly the middle and upper stratosphere. The strongest SSW in the Northern Hemisphere was observed in 2009. This study provides comparison of two strongest SSW in the SH and the strongest SSW in the NH to show difference between two hemispheres and possible impact to the lower or higher layers.

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Evidence of global-scale waves with zonal wave number zero in the stratosphere

Pure and Applied Geophysics ◽

10.1007/bf00878982 ◽

1978 ◽

Vol 116 (1) ◽

pp. 8-31 ◽

Cited By ~ 4

Author(s):

A. Ebel ◽

A. Ghazi ◽

W. B�tz

Keyword(s):

Global Scale ◽

Wave Number ◽

Zonal Wave Number

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