[P-EM05_2PO1] Characteristics of atmospheric waves in the mesosphere-lower thermosphere (MLT)

[PEM05-P01] Diurnal tide and QTD wave in the tropical stratosphere and MLT region: Long-term trends and solar cycle influence

*Venkateswara rao NARUKULL¹, Venkat ratnam M.¹, Vedavathi C.², Gurubaran S.³, Krishna murthy B.V.⁴, Vijaya bhaskara rao S.² (1.National Atmospheric Research Laboratory, 2.Sri Venkateswara University, 3.Indian Institute of Geomagnetism, 4.B1, CEEBROS, 47/20, IIIrd Main Road, Chennai)

Keywords:Diurnal Tide, Quasi-two day wave, Long-term trends, Solar cycle, Extended minimum

In the present study, long-term trends and solar cycle influence on the diurnal tide (DT) and quasi two day wave (QTDW) in the stratosphere, mesosphere and lower thermosphere (MLT) region over a tropical station Tirununveli (8.7oN, 77.7oE) are investigated using ERA-Interim datasets and MF radar observations available since 1993. As no ground truth is available over Tirununveli, suitability of the ERA-Interim data for the present study is ascertained using simultaneous radiosonde and MST radar observations over Gadanki (13.5oN, 79.2oE) and good consistency is found between the two. Amplitudes of the DT and QTDW over Tirununveli show a long-term linear increasing trend, which becomes prominent in the MLT region. Role of solar cycle on the DT and the QTDW is investigated by separating them with respect to the solar activity (minimum and maximum of solar cycles). Both the DT and QTDW show higher amplitudes during solar minimum and vice versa. Significant higher amplitudes in the recent extended solar minimum are noticed in the MLT region. However, no consistent relation is found between solar activity and DT in the stratosphere although increasing trend is clearly observed. Though increasing trend in the tropical convection is noticed at nearby locations, similar to the DT, it varies from location to location which may be due to large scale circulation effects. This demands data from network of radars located across the globe to see the combined effects of lower atmospheric forcing, circulation and their effects on MLT region.