Equatorial stratospheric thermal structure and ozone variations during the sudden stratospheric warming of 2013

Nath, Oindrila; Sridharan, S.; Gadhavi, Harish

doi:10.1016/j.jastp.2014.11.003

Cited by 9 publications

(10 citation statements)

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“…Previous studies showed that large eastward wave activity with various periods preconditioned the stratospheric circulation prior to the stratospheric warming events and the amplitudes of these waves got reduced imme- diately prior to the onset of the SSW events (Labitzke, 1981;Limpasuvan et al, 2004;Hoffmann et al, 2007;Pancheva et al, 2008). However, the present study indicates that the wave of k = 5 amplifies during and after the SSW event of 2013, which occurs during January 2013 (Nath et al, 2015). Shepherd and Tsuda (2008) observed eastward propagating 10, 16 and 23 day periodicities with k = 1 and k = 2 in at high latitude Southern Hemisphere (60-75 • S).…”

Section: Discussioncontrasting

confidence: 73%

Tropical response to extratropical eastward propagating waves

Sridharan

Sandhya

2015

Preprint

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Abstract. Space–time spectral analysis of ERA-interim winds and temperature at 200 hPa for December 2012–February 2013 shows the presence of eastward propagating waves with period near 18 days in mid-latitude meridional winds at 200 hPa. The 18 day waves of k = 1–2 are dominantly present at latitudes greater than 80°, whereas the waves of k = 3–4 are dominant at 60° of both Northern and Southern Hemispheres. Though the 18 day wave of smaller zonal wavenumbers (k = 1–2) are confined to high latitudes, there is an equatorward propagation of the 18 day wave of k = 4 and 5. The wave amplitude of k = 5 is dominant than that of k = 4 at tropical latitudes. In the Northern Hemisphere (NH), there is a poleward tilt in the phase of the wave of k = 5 at mid-latitudes, as height increases indicating the baroclinic nature of the wave, whereas in the Southern Hemisphere (SH), the wave has barotropic structure as there is no significant phase variation with height. At the NH subtropics, the wave activity is confined to 500–70 hPa with moderate amplitudes. It is reported for the first time that the wave of similar periodicity (18 day) and zonal structure (k = 5) as that of extratropical wave disturbance has been observed in tropical OLR, a proxy for tropical convection. We suggest that the selective response of the tropical wave forcing may be due to the lateral forcing of the eastward propagating extratropical wave of similar periodicity and zonal structure.

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Section: Discussioncontrasting

confidence: 73%

Tropical response to extratropical eastward propagating waves

Sridharan

Sandhya

2015

Preprint

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“…Because SSWs originate in a layer of the atmosphere where ozone heating is important (e.g., Nath et al, 2015), it has been suggested that changes in the migrating semidiurnal tide (SW2) could be responsible for some of the changes seen at higher altitudes (e.g., Goncharenko et al, 2012; Jin et al, 2012; Pedatella & Forbes, 2010; Siddiqui et al, 2019). Thus, it is important to assess to what extent SW2 changes might be responsible for the remaining SSW/MC light species depletions seen in our TIME‐GCM simulation excluding small‐scale GW forcing.…”

Section: Resultsmentioning

confidence: 99%

Coupling From the Middle Atmosphere to the Exobase: Dynamical Disturbance Effects on Light Chemical Species

et al. 2020

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This paper characterizes the impacts of sudden stratospheric warmings (SSWs) and mesospheric coolings (MCs) on the light species distribution (i.e., helium [He], and atomic hydrogen [H]) of the thermosphere using a combined data-modeling approach. Performing a set of numerical experiments with a general circulation model whose middle atmospheric dynamical and thermodynamical fields were constrained using a numerical weather prediction system, we simulate the effects of SSWs and MCs on light chemical species, and via comparisons with two data sets taken from the mesosphere and thermosphere, we quantify the associated variability in light species abundances and mass density. Large depletions in the observed and modeled polar H abundance in the mesosphere and lower thermosphere (MLT) occur with MC onset, as opposed to SSW onset. Depletions in all light thermospheric species at high northern latitudes extend up to the exobase in our model simulations during the January 2013 SSW/MC period, with the largest depletions simulated for the lightest species. Further, our modeling work substantiates the paradigm of increased mixing in the MLT driven by a meridional residual circulation during SSWs resulting from enhanced small-scale gravity wave and migrating semidiurnal tidal forcing; the former being the primary driver and the latter of secondary but notable importance in our model simulations. SSW/MC induced light species variability then gets projected upward into the thermosphere through molecular diffusion. Modeled light species variability during the January 2013 SSW/MC event suggests SSW/MC signatures could be present in the topside ionosphere and plasmasphere. Plain Language Summary Sudden stratospheric warmings (SSWs) and mesospheric coolings (MCs) are episodic polar middle atmospheric (∼12-80 km or ∼7-50 miles altitude) dynamical weather events driven by increased wave forcing from the troposphere. These events are known to have global effects on the meteorology of the upper atmosphere (i.e., the thermosphere and ionosphere). Observational and modeling evidence presented in this study demonstrate that SSWs and MCs in the middle atmosphere act to drive changes in the chemical composition of the upper atmosphere through an intricate series of processes, set in motion by SSW/MC enhancements in lower and middle atmospheric wave forcing. Our results show that SSW/MC driven changes in particularly light species like hydrogen extend well into the transition region between Earth's atmosphere and outer space. This implies that middle atmospheric weather may have an impact on the plasma populations several Earth radii above Earth's surface (∼10,000 miles or more away).

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“…The high‐latitude PW propagates toward the equator, and there is a convergence of PW activity toward equatorial region. The semidiurnal tide largely generated due to the accumulation of ozone molecules over equator gets interacted with planetary waves to generate the secondary waves (Goncharenko et al, ; Nath et al, ; Sridharan et al, ). Though the secondary waves are generated, their amplitudes are less when compared to the migrating SW2 tide.…”

Section: Discussionmentioning

confidence: 99%

Variabilities of Low‐Latitude Migrating and Nonmigrating Tides in GPS‐TEC and TIMED‐SABER Temperature During the Sudden Stratospheric Warming Event of 2013

Sridharan

2017

JGR Space Physics

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The Global Positioning System deduced total electron content (TEC) data at 15°N (geomagnetic), which is the crest region of equatorial ionization anomaly, are used to study tidal variabilities during the 2013 sudden stratospheric warming (SSW) event. The results from space‐time spectral analysis reveal that the amplitudes of migrating diurnal (DW1) and semidiurnal (SW2) tides are larger than those of nonmigrating tides. After the SSW onset, the amplitudes of DW1, SW2, SW1, and DS0 increase. Moreover, they show 16 day variations similar to the periodicity of the high‐latitude stratospheric planetary wave (PW), suggesting that the nonmigrating tides (SW1 and DS0) are possibly generated due to nonlinear interaction of migrating tides with PW. Similar spectral analysis on temperature at 10°N obtained from the Sounding of Atmosphere by Broadband Emission Radiometry (SABER) shows that the SW2 enhances at stratospheric heights and the SW2 is more dominant at 80–90 km, but its amplitude decreases around 100 km. The amplitudes of nonmigrating tides become comparable to those of SW2 around 100 km, and their contribution becomes increasingly important at higher heights. This suggests that the nonlinear interaction between migrating tides and PW occurs at low‐latitude upper mesospheric heights, as SW2 exhibits 16 day periodicity in SABER temperature at 100 km as observed in TEC. Besides, it is observed that the eastward propagating tides are less dominant than westward propagating tides in both TEC and SABER temperatures.

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Equatorial stratospheric thermal structure and ozone variations during the sudden stratospheric warming of 2013

Cited by 9 publications

References 34 publications

Tropical response to extratropical eastward propagating waves

Tropical response to extratropical eastward propagating waves

Coupling From the Middle Atmosphere to the Exobase: Dynamical Disturbance Effects on Light Chemical Species

Variabilities of Low‐Latitude Migrating and Nonmigrating Tides in GPS‐TEC and TIMED‐SABER Temperature During the Sudden Stratospheric Warming Event of 2013

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