[1] Using high-vertical resolution Indian mesosphere-stratosphere-troposphere (MST) radar and GPS sonde observations from Gadanki (13.5°N, 79.2°E), an attempt has been made for the first time to delineate the characteristics of Indian summer monsoon winds with special emphasis on the Tropical Easterly Jet stream (TEJ), its day-to-day, monthly, and interannual variability using observations available for more than a decade (1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008). For comparison, data available during 1996-2008 from routine radiosonde observations from nearby India Meteorological Department (IMD) observatory located at Chennai (13.0°N, 80.1°E) and National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) reanalysis data sets have been considered. Relatively poor vertical resolution data from IMD lead to underestimation of the jet characteristics like jet width, vertical shear above and below the jet, and the wind reversal height. Although reanalysis data sets represented well the spatial variability, they underestimate the peak zonal winds by about 5 m/s when compared to Indian MST radar and GPS sonde observations. Large day-to-day variability of TEJ characteristics (peak jet speed, jet height, jet width, zonal wind reversal height, and vertical shear of zonal wind) over Gadanki is noticed. No significant trend is observed in peak jet speed using reanalysis data sets either over Gadanki grid or over jet core region in Indian summer monsoon months. However, MST radar and GPS sonde observations show increasing trend ($1 m/s/yr) in peak jet speed particularly from the year 2000. Characteristics of the TEJ during active and break phases showed quite different features. Thus, statistics generated using the long-term database from Indian MST radar and GPS sonde provide valuable information for studying the TEJ characteristics and will be useful to incorporate in the future reanalysis data sets.

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The strong cross-equatorial flow in the lower troposphere, widely known as the monsoon low-level jet (MLLJ), plays an important role in the Indian summer monsoon (ISM) rainfall during June-September. Using high-resolution GPS radiosonde observations over Gadanki (13.58N, 79.28E), some new aspects of MLLJ have been reported. In the present study it is found that, on average, the MLLJ exists at 710 hPa over southeastern peninsular India, rather than at 850 hPa as reported by earlier studies. It is observed that the ECMWF Re-Analysis (ERA)-Interim data provide better results on the spatial, temporal, and vertical variation of MLLJ. Further, the characteristics of the MLLJ during the active and break spells of ISM are also investigated; higher MLLJ core height and intensity are found during active phases of the Indian monsoon. This study emphasizes the use of high-resolution measurements for studying monsoon dynamics in detail.

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Extensive observations on various atmospheric parameters were carried out from Gadanki (13.48°N, 79.18°E), a tropical station in India, during the annular solar eclipse of 15 January 2010. In the present study, we report changes observed in temperature and ozone concentration in the lower stratosphere associated with the eclipse. Unusual enhancements in the temperature of 12.5 K and in ozone concentration of 5.5. mPa are observed around 21 km just after the eclipse. Plausible mechanisms for the observed eclipse effects are discussed using data of simultaneous vertical and horizontal winds collected through co‐located MST radar observations. From the preliminary analysis, the temperature and ozone enhancements are attributed to large subsidence and horizontal advection, respectively.