Explain the 17.5-Minute Measurement Period

Educational function explaining why wave measurements use specific time periods for statistical validity.

Usage

explain_measurement_period()

Value

Character string with explanation

Examples

cat(explain_measurement_period())
#> 
#> WAVE MEASUREMENT PERIOD: WHY 17.5 MINUTES?
#> ==========================================
#> 
#> STATISTICAL REQUIREMENT
#> -----------------------
#> The significant wave height (Hs) is defined as the mean of the highest
#> 1/3 of all waves in a measurement period. For this statistic to be
#> reliable, you need a sufficient sample size.
#> 
#> TYPICAL WAVE PERIODS
#> --------------------
#> - Wind waves: 3-10 seconds
#> - Swell: 10-25 seconds
#> - Average ocean: ~8 seconds
#> 
#> NUMBER OF WAVES NEEDED
#> ----------------------
#> For statistical validity of H_1/3, you need approximately 100-200 waves.
#> 
#> With average period of 8 seconds:
#> - 100 waves = 800 seconds = 13.3 minutes (minimum)
#> - 200 waves = 1600 seconds = 26.7 minutes (ideal)
#> 
#> WMO RECOMMENDATIONS
#> -------------------
#> The World Meteorological Organization recommends:
#> - Standard period: 20-30 minutes
#> - Minimum acceptable: 17 minutes
#> - Marine Institute uses: 17.5 minutes (lower bound)
#> 
#> TRADE-OFFS
#> ----------
#> Longer period:
#>   + Better statistics (more waves sampled)
#>   + More stable Hs estimates
#>   - Less temporal resolution
#>   - May miss rapid changes in sea state
#> 
#> Shorter period:
#>   + Better temporal resolution
#>   + Captures rapid changes
#>   - Higher uncertainty in Hs
#>   - May not capture full wave variability
#> 
#> 17.5 MINUTES RATIONALE
#> ----------------------
#> The Marine Institute buoys use 17.5 minutes as a pragmatic choice:
#> - Meets minimum statistical requirements (~100+ waves)
#> - Provides hourly data with multiple samples
#> - Standard practice for operational wave buoys
#> - Consistent with international data sharing protocols