Estimation of turbulence parameters using ARIES ST Radar and GPS radiosonde measurements: First results from the Central Himalayan region

Turbulence in the atmosphere plays a vital role in controlling the surface, lower and upper tropospheric dynamics. Here, we have utilized a newly installed Aryabhatta Research Institute of Observational Sciences (ARIES) Stratosphere Troposphere (ST) radar at the high-altitude subtropical site in the central Himalayan region (Nainital, 29.4°N, 79.5°E, 1793 m above mean sea level) for the first ever estimation of turbulence parameters from this unique location. We have used radar observations made in years 2017 and 2019 with simultaneous and colocated global positioning system (GPS) radiosonde observations. In this context, turbulence parameters like turbulent kinetic energy dissipation rate, and eddy diffusion coefficient due to thermal and momentum fluctuations, have been determined by using (i) wind variance, (ii) Doppler spectral width, and (iii) backscatter signal power methods as well as synergistic radiosonde measurements using Thorpe length scale method. The kinetic energy dissipation rate and eddy diffusivity coefficients were found to be as high as 10 −2 m 2 /s 3 and 10 2.6 m 2 /s, respectively. Statistical distribution of turbulence parameters derived from radar and radiosonde was found to agree reasonably well in terms of measures of central tendency. The refractive index structure constant (C n 2 ) shows a decreasing tendency with height, and it is found to vary as large as 10 −14 to as small as 10 −19 m −2/3 . Range and temporal variation of signal-to-noise ratio (SNR) indicated the existence of a stable layer around 8 km height. It is also evident from the present study that the turbulence parameters at this central Himalayan region of complex terrain are higher by 1 order of magnitude than those reported from the southern part of India.