VHF radar observation of atmospheric winds, associated shears and &amp;lt;b&amp;gt;C&amp;lt;sup&amp;gt;2&amp;lt;/sup&amp;gt;&amp;lt;/b&amp;gt;&amp;lt;b&amp;gt;&amp;lt;sub&amp;gt;n&amp;lt;/sub&amp;gt;&amp;lt;/b&amp;gt; at a tropical location: interdependence and seasonal pattern

Ghosh, Apurna; Kumar, Vive; Kumar, K. Kishore; Jain, A. R.

doi:10.5194/angeo-19-965-2001

Cited by 13 publications

(8 citation statements)

References 18 publications

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“…Mesosphere‐stratosphere‐troposphere (MST) radar provides an opportunity to observe the monsoon features like the TEJ with high vertical resolution. Little work has been carried out to explore the monsoon features using MST radar with studies limited to 1–3 year periods [ Narayana Rao et al , 2000; Ghosh et al , 2001; Vasantha et al , 2002]. Detailed characteristics of vertical wind [ Jagannadha Rao et al , 2002, 2003] and turbulence [ Vasantha et al , 2002] in and around the jet core are also studied using limited data sets.…”

Section: Introductionmentioning

confidence: 99%

Characteristics of the Tropical Easterly Jet: Long‐term trends and their features during active and break monsoon phases

Raman¹,

Rao²,

Ratnam³

et al. 2009

J. Geophys. Res.

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[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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Section: Introductionmentioning

confidence: 99%

Characteristics of the Tropical Easterly Jet: Long‐term trends and their features during active and break monsoon phases

Raman¹,

Rao²,

Ratnam³

et al. 2009

J. Geophys. Res.

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“…An adaptive method of analysis has been used [Anandan et al, 1997]. Radar volume reflectivity (h) can be expressed in terms of signal-to-noise ratio (S/N), by assuming that the observed volume is uniformly filled with scatterers [Ghosh et al, 2001]…”

Section: Discussionmentioning

confidence: 99%

“…An adaptive method of analysis has been used [ Anandan et al , 1997]. Radar volume reflectivity (η) can be expressed in terms of signal‐to‐noise ratio (S/N), by assuming that the observed volume is uniformly filled with scatterers [ Ghosh et al , 2001] where r is the range of backscatter and Δr is the range resolution. The description of various parameters and their magnitudes are given in Table 2.…”

Section: Experimental Methods and Observationsmentioning

confidence: 99%

Observations of trapped humidity layer and Kelvin‐Helmholtz instability using UHF radar and GPS sonde

et al. 2004

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[1] UHF radar observations at Gadanki (13.47°N, 79.18°E) and Vaisala type GPS sonde measurements of atmospheric thermodynamic parameters (temperature, pressure, relative humidity, wind speed, and wind direction) from Tirupati (13.63°N, 79.40°E) have shown two distinct features of the lower troposphere over this region. One of the features is the observation of trapped humidity layer just above the boundary layer. These trapped humidity layers and associated gradients are observed to contribute significantly to the UHF radar backscattering, especially at the edges of the humidity layer. The second phenomenon is the observation of a long-lasting Kelvin-Helmholtz instability (KHI), at the height of $3 km, which lasted for about $210 min. The UHF radar vertical beam echo power has shown the characteristic power bursts pattern associated with KHI. The characteristic wavelength and time period of KHI waves are found to be 3.78 km and 18.4 min, respectively. Thus these results illustrate two important processes in the lower tropical troposphere, which are very important in UHF radar backscattering.

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“…Most of the measurements of turbulence characteristics are, however, confined to midlatitudes and high latitudes [ Gage et al , 1980; Hocking , 1983, 1985; Nastrom et al , 1986; Fukao et al , 1994; Nastrom and Eaton , 1997a, 1997b], and only a few measurements are available for tropical latitudes [ Sato and Woodman , 1982; Jain et al , 1995; Rao et al , 1997, 2001; Satheesan and Murthy , 2002; Ghosh et al , 2003]. The Indian tropical region shows a distinct seasonal variation in wind and associated vertical shear, and the year is divided into four seasons, namely, winter (December, January, and February), premonsoon (March, April, and May), monsoon (June, July, and August), and postmonsoon (September, October, and November) [ Ghosh et al , 2001; Rao et al , 2008]. Out of these four seasons, monsoon and winter seasons are totally different in their characteristics.…”

Section: Introductionmentioning

confidence: 99%

Characteristics of atmospheric turbulence in terms of background atmospheric parameters inferred using MST radar at Gadanki (13.5°N, 79.2°E)

Das

Ghosh²,

Satheesan

et al. 2010

Radio Sci.

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[I] Indian mesosphere-stratosphere-troposphere (MST) radar is located at Gadanki (B.soN, 79.2°E) in a tropical zone ofIndia. In this region the background atmospheric parameters such as atmospheric winds, temperature, and humidity show a distinct change from monsoon to winter season. For example, the monsoon season is dominated by tropical easterly jet winds in the upper troposphere (i.e., 14-17 km), and the winter season is dominated by westerly winds with peak value at about 12-14 km. The basic wind patterns in the two seasons differ significantly, and this is expected to give rise to differences in the characteristics of atmospheric turbulence parameters in the two seasons. In this paper, various atmospheric turbulence parameters such as eddy dissipation rate (E), eddy diffusivity (K h ), and horizontal scale length (10 and L s ) are obtained for the first time for the monsoon and winter seasons by using the available data sets from MST radar. An attempt is made to understand and explain the seasonal variability of these turbulence parameters in terms of the observed changes in the background atmospheric conditions.

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VHF radar observation of atmospheric winds, associated shears and <b>C<sup>2</sup></b><b><sub>n</sub></b> at a tropical location: interdependence and seasonal pattern

Cited by 13 publications

References 18 publications

Characteristics of the Tropical Easterly Jet: Long‐term trends and their features during active and break monsoon phases

Characteristics of the Tropical Easterly Jet: Long‐term trends and their features during active and break monsoon phases

Observations of trapped humidity layer and Kelvin‐Helmholtz instability using UHF radar and GPS sonde

Characteristics of atmospheric turbulence in terms of background atmospheric parameters inferred using MST radar at Gadanki (13.5°N, 79.2°E)

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