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- Title
Structures and Backscattering Characteristics of CUSAT 205 MHz Stratosphere‐Troposphere Radar at Cochin (10.04°N, 76.3°E)—First Results.
- Authors
Poddar, Nabarun; Das, Siddarth Shankar; Venugopal, Veenus; Abhilash, S.; Rakesh, V.
- Abstract
This paper presents the first ever observations on aspect‐sensitive characteristics of 205 MHz stratosphere–troposphere (ST) radar located at a tropical station Cochin (10.04°N, 76.3°E) using volume scanning. The most significant and new observation is that the signal‐to‐noise ratio in zenith and off‐zenith beams are nearly equal in some height region, indicating the presence of isotropic turbulence. Signal strength decreases by 0.75 dB per degree from 0 to 10 degree off‐zenith, 0.9 dB per degree from 10 to 20 degree off‐zenith and 0.3 dB per degree beyond 20 degree off‐zenith. Different causative mechanisms are discussed on the basis of various estimated parameters associated with aspect sensitivity. Maximum aspect sensitivity is observed between 12 and 17 km, indicating the presence of dynamic instability arising due to strong wind shear and atmospheric stability. When both the square of wind shear and stability parameters are above 0.25 × 10−3 s−2, the scatterers become mostly isotropic. The study also shows a power difference in the symmetric beams as well as azimuth angle dependency. Analysis suggests that this asymmetry is due to the tilting of layers by the action of atmospheric gravity waves generated through Kelvin‐Helmholtz instability. The present configuration of radar can provide a better understanding of three‐dimensional structures of turbulence and instabilities. Plain Language Summary: Radar backscatter from the atmosphere depends directly on the turbulent scale sizes present and the probing frequency. When the backscatter echo strength decays with the radar viewing zenith angle, the signals are said to be aspect sensitive that is, dependent on the viewing angle. There can be few circumstances under which such characteristics are observed, all primarily being anisotropic scattering processes which are caused due to various processes in the atmosphere. Such aspect sensitivity must be quantified for realizing the accurate operation of a radar which would otherwise result in underestimation of winds and other parameters obtained from the radar. Here the aspect sensitivity characteristics of the 205 MHz stratosphere‐troposphere (ST) radar installed at Cochin (10.04°N, 76.33°E) are studied using a detailed experiment using various probing techniques during Indian Summer Monsoon season and the characteristics of the atmosphere during that period are probed to explain the aspect sensitivity. Key Points: First observations of aspect‐sensitivity characteristics at 205 MHz stratosphere–troposphere radarMechanisms for the formation of isotropic and anisotropic turbulenceModulation of aspect sensitivity by wind shear and atmospheric stability
- Subjects
COCHIN (India); HELMHOLTZ, Hermann von, 1821-1894; KELVIN-Helmholtz instability; ECHO; RADAR; WIND shear; BACKSCATTERING; GRAVITY waves; PERIODONTAL probe
- Publication
Radio Science, 2024, Vol 59, Issue 6, p1
- ISSN
0048-6604
- Publication type
Article
- DOI
10.1029/2023RS007894