Tuesday, 29 August 2023
Boundary Waters (Hyatt Regency Minneapolis)
Doppler weather radar systems emit pulses with a specific pulse repetition frequency (PRF). A higher PRF results in more pulses being sent per second, enabling the radar to capture smaller phase changes between samples and measure higher radial velocities. However, a higher PRF also means less time for the radar to sense a particular part of the atmosphere, and objects further from the radar may not be detected. This inverse relationship between maximum range and maximum (Nyquist) radial velocity is known as the Doppler dilemma. Radar operators must strike a balance between these factors based on current needs.
The Nyquist velocity is typically not overly high, often resulting in aliasing artifacts in the radial velocity product output. This issue is even more pronounced in C and X-band radars, as the Nyquist velocity is dependent on the radar's wavelength. Several methods exist to address aliasing during the data post-processing stage.
Stagger is a measurement method, which extends the Nyquist velocity by using two different PRFs. When an appropriate ratio of frequencies is selected, the velocity can be unfolded up to a significant multiple of the original Nyquist velocity. Common stagger ratios include 2:3, 3:4, or 4:5, which extend the Nyquist velocity by 2x, 3x, and 4x, respectively. However, selecting a more aggressive stagger ratio increases the probability of error in unfolding, leading to more catastrophic velocity errors.
Meteopress solid-state weather radar provides staggered PRT measurement and processing capability with freely selectable stagger ratio. We conducted a case study comparing very aggressive stagger ratios, such as 5:7, 7:9, and 8:9, with more common stagger ratios. The practical results are illustrated with measurements from real situations. The evaluation of catastrophic errors demonstrates the differences between each stagger ratio setup and the improvement achieved after applying error correction algorithms. This research offers valuable insights into the potential benefits and drawbacks of utilizing aggressive stagger ratios in Doppler weather radar systems, ultimately contributing to the optimization of radar performance and data quality.
The Nyquist velocity is typically not overly high, often resulting in aliasing artifacts in the radial velocity product output. This issue is even more pronounced in C and X-band radars, as the Nyquist velocity is dependent on the radar's wavelength. Several methods exist to address aliasing during the data post-processing stage.
Stagger is a measurement method, which extends the Nyquist velocity by using two different PRFs. When an appropriate ratio of frequencies is selected, the velocity can be unfolded up to a significant multiple of the original Nyquist velocity. Common stagger ratios include 2:3, 3:4, or 4:5, which extend the Nyquist velocity by 2x, 3x, and 4x, respectively. However, selecting a more aggressive stagger ratio increases the probability of error in unfolding, leading to more catastrophic velocity errors.
Meteopress solid-state weather radar provides staggered PRT measurement and processing capability with freely selectable stagger ratio. We conducted a case study comparing very aggressive stagger ratios, such as 5:7, 7:9, and 8:9, with more common stagger ratios. The practical results are illustrated with measurements from real situations. The evaluation of catastrophic errors demonstrates the differences between each stagger ratio setup and the improvement achieved after applying error correction algorithms. This research offers valuable insights into the potential benefits and drawbacks of utilizing aggressive stagger ratios in Doppler weather radar systems, ultimately contributing to the optimization of radar performance and data quality.
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