Slot: Percentile Reference Period Start (percentile_reference_period_start)

Start of the reference distribution used for percentile-based thresholds. Mandatory for percentile metrics: "95th percentile" over 2000-2019 gives a different threshold than 1980-2010, and this delta is real.

Tier: conditionally_core

Why this slot matters

In a warming climate a "95th percentile" computed over 1971-2000 is a materially different threshold than one over 2000-2019; leaving the baseline unstated makes percentile-based studies non-comparable and non-reproducible.

In plain terms

"Unusually hot" means hot compared to some stretch of past years. Which years you compare against changes what counts as unusual — this field records where that stretch begins.

URI: envar:slot/percentile_reference_period_start

Applicable Classes

Name	Description	Modifies Slot
DerivedHeatMetric	Methodology slots specific to derived heat metrics (WBGT, Heat Index, UTCI, a...	no

Properties

Type and Range

Property	Value
Range	Date
Domain Of	DerivedHeatMetric

Cardinality and Requirements

Property	Value

Examples

Value
1991-01-01

See Also

• https://www.ncei.noaa.gov/products/land-based-station/us-climate-normals

Identifier and Mapping Information

Annotations

property	value
tier	conditionally_core
justification	In a warming climate a "95th percentile" computed over 1971-2000 is a materially different threshold than one over 2000-2019; leaving the baseline unstated makes percentile-based studies non-comparable and non-reproducible.
explanation	"Unusually hot" means hot compared to some stretch of past years. Which years you compare against changes what counts as unusual — this field records where that stretch begins.

Schema Source

• from schema: https://w3id.org/linkml/microschemas/envar

Mappings

Mapping Type	Mapped Value
self	envar:percentile_reference_period_start
native	envar:percentile_reference_period_start

LinkML Source

name: percentile_reference_period_start
annotations:
  tier:
    tag: tier
    value: conditionally_core
  justification:
    tag: justification
    value: In a warming climate a "95th percentile" computed over 1971-2000 is a materially
      different threshold than one over 2000-2019; leaving the baseline unstated makes
      percentile-based studies non-comparable and non-reproducible.
  explanation:
    tag: explanation
    value: '"Unusually hot" means hot compared to some stretch of past years. Which
      years you compare against changes what counts as unusual — this field records
      where that stretch begins.'
description: 'Start of the reference distribution used for percentile-based thresholds.
  Mandatory for percentile metrics: "95th percentile" over 2000-2019 gives a different
  threshold than 1980-2010, and this delta is real.'
title: Percentile Reference Period Start
examples:
- value: '1991-01-01'
  description: start of the 1991-2020 climate-normal baseline
from_schema: https://w3id.org/linkml/microschemas/envar
see_also:
- https://www.ncei.noaa.gov/products/land-based-station/us-climate-normals
rank: 1000
domain_of:
- DerivedHeatMetric
range: date