Planetary wave coupling (5–6-day waves) in the low-latitude atmosphere–ionosphere system

Abstract

Vertical coupling in the low-latitude atmosphere-ionosphere system driven by the 5-day Rossby W1 and 6-day Kelvin E1 waves in the low-latitude MLT region has been investigated. Three different types of data were analysed in order to detect and extract the $6-day wave signals. The National Centres for Environmental Prediction (NCEP) geopotential height and zonal wind data at two pressure levels, 30 and 10 hPa, were used to explore the features of the $6-day waves present in the stratosphere during the period from 1 July to 31 December 2004. The $6-day wave activity was identified in the neutral MLT winds by radar measurements located at four equatorial and three tropical stations. The $6-day variations in the ionospheric electric currents (registered by perturbations in the geomagnetic field) were detected in the data from 26 magnetometer stations situated at low latitudes. The analysis shows that the global $6-day Kelvin E1 and $6-day Rossby W1 waves observed in the low-latitude MLT region are most probably vertically propagating from the stratosphere. The global $6-day W1 and E1 waves seen in the ionospheric electric currents are caused by the simultaneous $6-day wave activity in the MLT region. The main forcing agent in the equatorial MLT region seems to be the waves themselves, whereas in the tropical MLT region the modulated tides are also of importance. r

Influence of temperature on the infradian growth rhythm inUlva lactuca(Chlorophyta)

“…1) (Pancheva et al, 2006(Pancheva et al, , 2008. In the MLT region, the 6-day Rossby wave reaches maxima just before and just after the equinoxes (Talaat et al, 2001;Pancheva et al, 2008) and minimizes at solstices (Talaat et al, 2001). The wave amplitudes at the equinoxes are smaller than the peaks before and after, but are still larger than the wave amplitudes at solstices (Liu et al, 2004).…”

“…Only the 2-and 6-day waves propagate vertically from the stratosphere to the mesosphere/lower thermosphere (MLT) region and reach the ionosphere (Fig. 1) (Pancheva et al, 2006(Pancheva et al, , 2008. In the MLT region, the 6-day Rossby wave reaches maxima just before and just after the equinoxes (Talaat et al, 2001;Pancheva et al, 2008) and minimizes at solstices (Talaat et al, 2001).…”

“…The atmospheric Kelvin waves are usually classified as follows: 'slow' waves with periods of 10-20 days, 'fast' waves with periods of 6-10 days, and 'ultra-fast' waves with periods of 3-4 days (Pancheva et al, 2008). Like Rossby waves, Kelvin waves originate in the troposphere and propagate through the stratosphere to the MLT region.…”

Signatures of 2-day wave in the E-region electric fields and their relationship to winds and ionospheric currents

“…These waves are forced by large-scale unsteady convective clusters in the tropical troposphere and accompanying latent heat release. They propagate horizontally and vertically carrying momentum to the middle and upper atmosphere (Pancheva et al, 2008). Forbes and Leveroni (1992) found a quasi 16-day oscillation in the the equatorial ionosphere likely connected with the upward penetration of a free Rossby mode.…”

The ultra-fast Kelvin waves in the equatorial ionosphere: observations and modeling

“…It is believed that they are excited by tropical convection systems (Holton, 1972;Salby and Garcia, 1987;Bergman and Salby, 1994;Pancheva et al, 2008).…”