Meteor radar measurements of MLT winds near the equatorial electro jet region over Thumba (8.5° N, 77° E): comparison with TIDI observations

S R John,K V Subrahmanyam,Q Wu,G Manju

doi:10.5194/angeo-29-1209-2011

S R John, K V Subrahmanyam + Show 2 more

Open Access

https://doi.org/10.5194/angeo-29-1209-2011

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Abstract

Abstract. The All-Sky interferometric meteor (SKYiMET) radar (MR) derived winds in the vicinity of the equatorial electrojet (EEJ) are discussed. As Thumba (8.5° N, 77° E; dip lat. 0.5° N) is under the EEJ belt, there has been some debate on the reliability of the meteor radar derived winds near the EEJ height region. In this regard, the composite diurnal variations of zonal wind profiles in the mesosphere-lower thermosphere (MLT) region derived from TIMED Doppler Interferometer (TIDI) and ground based meteor radar at Thumba are compared. In this study, emphasis is given to verify the meteor radar observations at 98 km height region, especially during the EEJ peaking time (11:00 to 14:00 LT). The composite diurnal cycles of zonal winds over Thumba are constructed during four seasons of the year 2006 using TIDI and meteor radar observations, which showed good agreement especially during the peak EEJ hours, thus assuring the reliability of meteor radar measurements of neutral winds close to the EEJ height region. It is evident from the present study that on seasonal scales, the radar measurements are not biased by the EEJ. The day-time variations of HF radar measured E-region drifts at the EEJ region are also compared with MR measurements to show there are large differences between ionospheric drifts and MR measurements. The significance of the present study lies in validating the meteor radar technique over Thumba located at magnetic equator by comparing with other than the radio technique for the first time.

Highlights

The understanding of Earth’s atmosphere to a great extent depends on understanding the energetics and dynamics of the middle and upper atmosphere (McLandress and Ward, 1994; Clemesha, 2002)
The Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) Doppler Interferometer (TIDI) and ground based meteor wind radar measured composite diurnal variations of zonal winds at 98 km region over Thumba are compared during the year 2006
The composite diurnal variation of meteor (SKYiMET) radar (MR) measured zonal winds at 98 km, which is the focus of the present study, show remarkably good agreement with TIDI measurements

Summary

Introduction

The understanding of Earth’s atmosphere to a great extent depends on understanding the energetics and dynamics of the middle and upper atmosphere (McLandress and Ward, 1994; Clemesha, 2002). Evidences for non-linear wave-wave interactions and the signature of lower atmospheric processes are observed in this region (Beard et al, 1996; Kumar et al, 2008, 2007a; Eckermann and Vincent, 1994). To study these interactions in depth, we need to have reliable long term wind and temperature measurements in the MLT region as most of these phenomena are exhibited in the form of wind/temperature fluctuations. Long term wind observations have been made across the globe and studies have been carried out in this regard using various instruments (Manson et al, 1992; Middleton et al, 2002, Kishore Kumar et al, 2008). Wind measurements in the MLT region are primarily obtained from rocket soundings, radars like MF, MST and meteor wind radars (Vincent, 1984; Manson et al, 1991; Kumar et al, 2007b), and satellites (Huang et al, 2006)

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