Abstract
Abstract. Temporal variation of mean winds between the 65 to 85 km height region from the data collected over the course of approximately four years (1995–99), using the Indian MST radar located at Gadanki (13.5° N, 79.2° E), India is presented in this paper. Mesospheric mean winds and their seasonal variation in the horizontal and vertical components are presented in detail. Westward flows during each of the equinoxes and eastward flows during the solstices are observed in the zonal component. The features of the semi-annual oscillation (SAO) and the quasi-biennial oscillation (QBO) in the zonal component are noted. In the meridional component, contours reveal a northward motion during the winter and a southward motion during the summer. Large inter-annual variability is found in the vertical component with magnitudes of the order of ± 2 ms-1 . The MST observed winds are also compared with the winds observed by the MF radar located at Tirunelveli (8.7° N, 77.8° E), India, the High Resolution Doppler Imager (HRDI) onboard the Upper Atmospheric Research Satellite (UARS), and with the CIRA-86 model. A very good agreement is found between both the ground-based instruments (MST radar and MF radar) in the zonal component and there are few discrepancies in the meridional component. UARS/HRDI observed winds usually have larger magnitudes than the ground-based mean winds. Comparison of the MST derived winds with the CIRA-86 model in the zonal component shows that during the spring equinox and the summer, the winds agree fairly well, but there are a lot of discrepancies in the other seasons and the observed winds with the MST radar are less in magnitude, though the direction is same. The strengths and limitations in estimating reliable mesospheric mean winds using the MST radar are also discussed.Key words. Meteorology and atmospheric dynamics (general circulation; middle atmosphere dynamics; waves and tides)
Highlights
During the past decade remarkable advances have been made in our understanding of the dynamics of the equatorial mesosphere
Winds observed by MF radar located at Tirunelveli are used to compare winds observed with MST radar
Excellent agreement can be seen in the zonal component for all the days, whereas some discrepancies are seen in the meridional component, especially during equinoxes
Summary
During the past decade remarkable advances have been made in our understanding of the dynamics of the equatorial mesosphere. The mesosphere for their better temporal and altitude resolution (Woodman and Guillen, 1974) Both Meteor and MF radars are widely used to measure the mesospheric and lower thermospheric motions (Vincent, 1993; Raghava Reddi and Ramkumar, 1997; Rajaram and Gurubaran, 1998). The network of point observations would be highly complementary for the existing satellite and model database, which provides gross features of the geostropic wind field and other parameters on a global scale In this regard, MST radar observations can provide valuable complementary information on winds at these lower heights (Rottger et al, 1983). The off-line data processing for the parameterization of the Doppler spectrum involves removal of dc, estimation of average noise level, incoherent integration and computation of the three low radar moments. The echoes due to meteor trails, which were detected less frequently, have been removed and the radial wind velocities are esti-
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
