Tropical connection to the polar stratospheric sudden warming through quasi 16-day planetary wave

Abstract

Abstract. The Planetary Waves (PWs) are believed to have significant role in generating the wintertime warming over the polar stratosphere, known as Stratospheric Sudden Warming (SSW). However, the origin, characteristics and evolution of these waves are still speculative. The possibility that the PWs over the polar stratosphere, which play an important role in the generation of SSW, could also have contribution from the tropics has been indicated through many numerical simulations in the past, but due to the paucity of global measurements it could not be established unequivocally. The earlier numerical studies also indicated the presence of a zero-wind line (more general the critical layer, where the zonal wind amplitude becomes zero) whose real counterparts were not observed in the atmosphere. The present study based on the NCEP/NCAR reanalysis of stratospheric wind and temperatures of recent years clearly shows that (i) the zero-wind line appears over the tropics ∼60 days prior to the major SSWs and progresses towards the Pole and (ii) an enhanced PW activity of quasi periodicity 16-days, which is also seen almost simultaneously with the zero-wind line, shows a propagation from equator to the Pole. This result is significant as it presents for the first time the connection between the tropics during the SSW events and the pole, through the quasi 16-day wave.

Stratospheric sudden warming effects on winds and temperature in the middle atmosphere at middle and low latitudes: a study using WACCM

“…During the easterly phase of the QBO, there is propagation of these planetary waves (originating in the high latitudes) in the stratosphere across the equator, while in the westerly phase of the QBO, the planetary waves break at ∼ 20-25 • N and there is no propagation across the equator. Hence a spectral analysis of winds at the low latitudes during the easterly phase of the QBO could indicate the presence of planetary waves with periods comparable to the ones causing the onset of the SSW as in [2005][2006] and reported on by Vineeth et al (2010). However, our analysis indicates that the planetary wave propagation is equatorward from the mid-high latitudes during the SSW events and gives no indication of poleward propagation of planetary waves in the tropics as reported by Vineeth et al (2010).…”

“…Hence a spectral analysis of winds at the low latitudes during the easterly phase of the QBO could indicate the presence of planetary waves with periods comparable to the ones causing the onset of the SSW as in [2005][2006] and reported on by Vineeth et al (2010). However, our analysis indicates that the planetary wave propagation is equatorward from the mid-high latitudes during the SSW events and gives no indication of poleward propagation of planetary waves in the tropics as reported by Vineeth et al (2010). The effects of the planetary wave propagation across the tropical stratosphere during the easterly phase of the QBO have been reported during the early winter months of November and December (Ortland, 1997;O'Sullvan, 1997).…”

“…Matthias et al (2013) find a continuous band of westward wind extending from the pole to the tropics in the stratosphere during the SSW events of 2009, 2010 and 2012, while no such band exists in 2006. Matthias et al (2013) attribute the differences between SSW events to increased planetary wave activity between 30 and 50 • N. Vineeth et al (2010) showed a latitudinal connection between low and high latitudes through the presence of a quasi-16-day wave during the 2003-2004 and 2005-2006 SSW and speculated that this might be due to the phase of the quasi-biennial oscillation (QBO). They however concluded that there was wave propagation from the equator to the pole during SSW, which modulates the zero wind line at 10 hPa.…”

Quasi-16-day periodic meridional movement of the equatorial ionization anomaly

“…Fagundes et al (2005) A series of recent reports concerning ionospheric perturbations associated with lower atmospheric forcing have focused on sudden stratospheric warming (SSW). These reports mainly discussed the features of the ionospheric variation in low-latitude region, the possible connections between the state of the atmosphere at low latitude and high latitude, and the possible connections between the ionosphere and MLT region related to SSW Goncharenko et al, 2010a, b;Mukhtarov et al, 2010;Pedatella and Forbes, 2009;Vineeth et al, 2007Vineeth et al, , 2010. Using the global reanalysis data of atmospheric temperature and wind provided by the National Centers for Environmental Prediction (NCEP) and National Center for Atmospheric Research (NCAR), Vineeth et al (2010) found an enhanced planetary wave (PW) activity of quasi-16-day periodicity in the stratosphere propagating from the Equator to the North Pole during several SSW years.…”

Variations of Kelvin waves around the TTL region during the stratospheric sudden warming events in the Northern Hemisphere winter

“…Fritz and Soules (1970) first revealed the lower temperature in the tropical stratosphere during an SSW event by satellite data. Several subsequent studies, both theoretical and observational, investigated the relationship between the tropical region and the SSW events (Garcia, 1987;Holton et al, 1995;Plumb and Eluszkiewicz, 1999;Randel et al, 2002;Vineeth et al, 2010;Yoshida and Yamazaki, 2011). These studies stated that the meridional circulation driven by the transient planetary wave forcing associated with polar SSWs can induce upwelling in the tropical region, in turn produce cooling in the stratosphere and upper troposphere in the tropical region during SSW events.…”