[P-EM05_2AM2] Characteristics of atmospheric waves in the mesosphere-lower thermosphere (MLT)

[PEM05-12] Vertical and lateral wave coupling observed with network of MLT/MST Radars over Indian region

*Venkat ratnam M¹, Eswariah S.², Venkateswara rao N.¹, Vijayabhaskar rao S.², Kishore kumar K.³, Sathish kumar S.⁴, Gurubaran S.⁴ (1.National Atmospheric Research Laboratory, 2.Sri Venkateswara University, 3.Space Physical Laboratory, 4.Indian Institute of Geomagnetism)

Keywords:Coupling, Meteor/MF radars, Tropical MLT region

It is well known that gravity waves and tides play an important role in delineating the middle atmospheric structure and dynamics. There have been several studies in recent years, using different measurement techniques, to understand significant roles played by gravity waves and tides in the lower, middle and upper atmospheres. However, only a few studies addressed this problem with simultaneous observations of all the three regions. Moreover, no efforts have been made so far to understand the lateral forcing of these waves and tides since such a study needs a network of radars located nearby which was missing. With the establishment of an advanced meteor radar at Sri Venkateswara University, Tirupati (13.63oN, 79.4oE), India, and up gradation of MF radar at Kolhapur (16.8oN, 74.2oE) together with MST radar at Gadanki (13.5oN, 79.2oE), Meteor radar at Thumba (8.5oN, 77oE) and MF radar at Tirunalveli (8.7oN, 77.8oE) forms a unique network of radars in the tropical region. Importantly, all these radars are located within 1000 km distance. Accordingly, this network is suitable to study the lower atmospheric forcing and its impacts on middle and upper atmospheric structure and dynamics. For the present study, all these radars were simultaneously operated for a few days in September 2013. These observations show the presence of short period gravity waves and tides (diurnal, semi-diurnal and ter-diurnal) at all locations. Large day-to-day day variability in gravity waves and tides is observed within a station and among different stations providing insight on lateral coupling. Phase propagations of the three tidal components at different stations is used to further understand the lateral coupling. Using simultaneous MST radar, Rayleigh lidar and SVU meteor radar (which are nearly co-located), lower atmospheric forcing and its impacts on the mesosphere and lower thermosphere are investigated. This study showed need for long-term measurements, with simultaneous operation of all the above mentioned network of radars, to effectively address the problem of vertical and latitudinal wave forcing.