return_period

Derive empirical return-period thresholds from a 1-D timeseries using plotting-position rank statistics over the annual-maxima series. Hazard-agnostic — commonly applied to river discharge for flood-trigger threshold derivation in anticipatory-action recipes, but the same op is valid for precipitation, wind speed, surge height, or any positive extreme variable. Empirical (non-parametric) quantile only; GEV/Gumbel fitting and confidence intervals are out of scope for v0 (see .tickets/impl/eap-recipe-bangladesh-floods/02-op-return-period.md).

ID	temporal_return_period
Domain	temporal
Category	aggregate
Type	timeseries-to-mapping
Version	1.0.0

view yaml ◦view github ◦

Parameters

return_periods: array · default 2,5,10,25,50,100 · Return periods in years to derive thresholds for. Values <= 1.0 are rejected (return period < 1 year has no physical meaning for annual maxima).
plotting_position: select · default weibull · Plotting-position formula. Weibull = i/(n+1) — operational hydrology default. Gringorten = (i-0.44)/(n+0.12) — closer to unbiased for Gumbel-distributed extremes. Hazen = (i-0.5)/n — US Weather Service historical convention. Rank i ascending of n annual maxima.
water_year_start: select · default jan · Calendar month at which the water year begins. `jan` = calendar year (default; matches GloFAS reanalysis convention). `oct` = US water-year convention. `jul` = austral water year convention used in some southern-hemisphere monsoon basins.