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

Abstract. Simultaneous observations made on four days using the MST radar and GPS-sonde at Gadanki (13.5 • N, 79.2 • E), a tropical station in India, are presented to address the aspect sensitivity of radar backscatters observed at different heights. The observations show that wherever stability parameter N 2 is high, vertical shear of horizontal wind is low and Richardson number (R i ) is high, the aspect sensitivity is high indicating that the aspect sensitive radar backscatters are due to thermal structures in the atmosphere. Such a case can be seen very clearly in the upper troposphere and lower stratosphere. At some heights, where N 2 is high, R i is high, but shears are relatively weak, the aspect sensitivity is found to almost disappear, indicating that some amount of shear provides favorable conditions for causing aspect sensitivity. Aspect sensitivity does not occur at all where N 2 is low or negative and R i is low in spite of wind shear being either high or low, indicating that the regions are well mixed and hence turbulent. The study also shows a power difference in the symmetric beams. A case study on this aspect suggests that this asymmetry is due to the tilting of layers by the action of atmospheric waves. There is indication that these waves are generated through Kelvin-Helmholtz-instability (KHI).

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“…5). Signatures of upward propagating atmospheric waves associated with the KHI have been seen (Das et al, 2004). At higher heights (i.e.…”

Section: Tilting Of Atmospheric Layers and Their Generation Mechanismsmentioning

confidence: 82%

Aspect sensitivity in the VHF radar backscatters studied using simultaneous observations of Gadanki MST radar and GPS sonde

et al. 2004

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“…The height resolution of the radiosonde measurements is 300-400 m. Simultaneous GPS sonde observations were carried out at Gadanki for campaign-II along with radar observations using ESF-3 (see Table 1). GPS sonde provides fine height resolution of the order of 3 -10 m [Das et al, 2004]. The ascent rate of the balloon (radiosonde/GPS sonde) was 300 -350 m/ min and it took 40 -50 min to reach the tropopause.…”

Section: Methodsmentioning

confidence: 99%

Diurnal variability of the tropical tropopause: Significance of VHF radar measurements

Das¹,

Jain

Kumar

et al. 2008

Radio Science

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[1] VHF radars have been used for the detection of atmospheric stable layers such as the tropopause for quite sometime. This opened up a possibility of using VHF radars to study the short period variability of the tropopause with a better time and height resolution as compared to conventional radiosonde measurements. In the present study, a method to determine the tropopause height using VHF radar located at Gadanki (13.5°N, 79.2°E) is discussed and the results are compared with the simultaneous balloon observations. Comparison of radar measurements of cold-point tropopause height (CPT) with simultaneous balloon ascents on 58 occasions has shown a very good agreement with a correlation coefficient of 0.85. The data collected during four different campaigns, which were carried out by employing radar and radiosonde/GPS sonde observations to study the different aspects of lower atmospheric dynamics, are used for this purpose. The radar measurements are then extensively used to study the diurnal variation of tropopause height for the first time over this latitude. The results showed that the tropopause does respond to the diurnal oscillations, which are consistent with the earlier radar studies reported from other geographical locations. During one of the campaigns, the tropopause height has also exhibited the semidiurnal oscillation, which is first of its kind. The diurnal observations clearly demonstrated the usefulness of the radar-detected tropopause. Further, the oscillations in the tropopause height showed a phase delay of $1 h and 4-6 h with zonal and meridional wind tidal oscillations, respectively. The observed diurnal/ semidiurnal oscillations in the tropopause height are interpreted as tidal manifestations. However, the diurnal variation of convective activity, which also contributes to the diurnal variation of tropopause height, is also accounted. The significance of the present study lies in showing the response of tropopause height to the propagating tides, which can provide some new insights in stratosphere-troposphere exchange processes.

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Investigation of Kelvin-Helmholtz Instability in the boundary layer using Doppler lidar and radiosonde data

Das

Saha

et al. 2018

Atmospheric Research

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

Cited by 4 publications

References 34 publications

Aspect sensitivity in the VHF radar backscatters studied using simultaneous observations of Gadanki MST radar and GPS sonde

Aspect sensitivity in the VHF radar backscatters studied using simultaneous observations of Gadanki MST radar and GPS sonde

Diurnal variability of the tropical tropopause: Significance of VHF radar measurements

Investigation of Kelvin-Helmholtz Instability in the boundary layer using Doppler lidar and radiosonde data

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