Description
Calculate a supplied single-PRF Doppler Nyquist velocity interval.
Atmospheric scalar terms require explicit averaging, spectral, geometric and propagation conventions. One fluctuation product is not a time-averaged flux, a squared deviation is not a full scintillation index, and a Nyquist interval does not de-alias radar velocity. Layer terms require compatible units and model assumptions.
Calculate a supplied single-PRF Doppler Nyquist velocity interval.
When to use this tool
Use Radar Nyquist Velocity Interval when you already have wavelength, pulseRepetitionFrequency and need to calculate a supplied single-PRF Doppler Nyquist velocity interval.
How to use the tool and how it works
- Enter wavelength, pulseRepetitionFrequency. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read nyquistSpeed, lowerInclusive, upperExclusive. Use the output convention below.
Require wavelength and pulse repetition frequency positive; speed=wavelength*PRF/4, interval=[-speed,+speed).1
For the specified pulse-Doppler convention, the unambiguous velocity magnitude is wavelength times pulse repetition frequency divided by four. Velocities outside the interval can alias; computing its endpoints does not correct that ambiguity.2
| Input field | Meaning and units | Accepted input |
|---|---|---|
| wavelength | Wavelength | Required. Finite number; strictly above 0. |
| pulseRepetitionFrequency | Pulse Repetition Frequency | Required. Finite number; strictly above 0. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| nyquistSpeed | wavelength*pulseRepetitionFrequency/4; m/s for meters and Hz. | Required. Finite number. |
| lowerInclusive | Lower Inclusive | Required. Finite number. |
| upperExclusive | Positive endpoint excluded from the selected [-speed,+speed) interval. | Required. Finite number. |
{
"input": {
"wavelength": 0.1,
"pulseRepetitionFrequency": 1000
},
"output": {
"nyquistSpeed": 25,
"lowerInclusive": -25,
"upperExclusive": 25
}
}Limitations and assumptions
- Wavelength in meters and PRF in Hz give m/s. This states one unambiguous-velocity convention, not de-aliasing, an observed velocity or a complete radar mode.
- Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
- Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.
Alternative or Complementary methods
Use the complete measurement and physical retrieval model. Include calibration, averaging, source geometry, spectral response and relevant transfer or flow effects when local weights and signal factors cannot establish the desired atmospheric quantity.
References
-
Calculation and input contract: atmospheric-physics/radar-nyquist-velocity-interval — tool.io
-
A Guide for Interpreting Doppler Velocity Patterns: Background — NOAA National Severe Storms Laboratory
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