ARIES ST Radar: The First Central Himalayan Wind Profiler

Abstract

Recently, a 206.5 MHz Stratosphere Troposphere (ST) Radar system was successfully installed and made operationalized at Aryabhatta Research Institute of Observational Sciences (ARIES) (29.4N, 79.2E, 1793 m amsl), Nainital, India. It is the ¯rst such unique observational facility located in the central Himalayan region and will play an important role in understanding the meteorological conditions of the region that has a vital role in atmospheric studies in South Asia. The entire ST radar system is indigenously built and installed in a compact 30 m 30 m two-storey building, making maximum use of the available space in the hilly terrain. A metal fence of 3.5–4 m height was designed and installed along the perimeter of the array to attenuate the clutter returns from the nearby mountains with the shielding e±ciency 22–25 dB. Since its operation, the radar has obtained useful data of neutral atmosphere, precipitation, convection, and hailstorm events for scienti¯c research. The technical details of di®erent sub-systems, radar integration and calibration methodology are presented here. A dedicated o®-line GUI based data processing tool has been developed and is being used for the data analysis. A comparison of wind components derived from ARIES ST Radar with collocated GPS-radiosonde observations indicates a good agreement with correlation coe±cients for zonal (0.92), meridional (0.76), wind speed (0.86), and wind direction (0.7). The change in wind patterns is demonstrated up to a height of about 31 km amsl and the tropopause was marked to be at 16–17 km on 2020 June 20. A dramatic reversal of winds from westerly (below the tropopause) to easterly (above the tropopause) was also observed. ARIES ST Radar could capture the signature of the precipi tation in addition to neutral air in the same Doppler spectrum and the height of the starting point of precipitation is identified to be 6 km. This ability to detect atmospheric scattering from both neutral wind (Bragg) and precipitation (Rayleigh) in the same spectrum makes the 200 MHz band radar a unique instrument in the wind pro¯ler application for atmospheric research.