Release note: Hydrionis Derived Climatology v1.0
The first release of the governed derivation layer: reference normals and decadal means computed from the long records Hydrionis holds, each carrying its method, method version, input observation identifiers and inherited rights. It also records a correction — computed rainfall normals differ from the hand-transcribed values previously published by up to 3.8 per cent.
What was released
Version 1.0 of the Hydrionis derivation layer: reference normals over the WMO 1991–2020 period, and decadal means over every sufficiently complete long record the platform holds.
| Family | Values produced | Refused |
|---|---|---|
| Reference normals (1991–2020) | 34 | 0 |
| Decadal means | 22,647 | 0 |
A correction
Methods in this release
| Method | Version | What it must not be read as saying |
|---|---|---|
| Mean over a period | 1.0.0 | A mean over a fixed reference period, not a measurement of any single period within it. Requires the whole span: a mean of a partial span is a different statistic wearing the same name. |
| Anomaly against a reference normal | 1.0.0 | Compares a subject with its own history, never with another subject. A wetter-than-normal desert is still a desert. Meaningless unless a full reference-period normal exists for the same subject and metric. |
| Centred rolling mean | 1.0.0 | A smoothed line is not the data. Values near the ends of a series have no complete window and are not produced rather than being computed from a partial one, because a trend drawn from a half-window is an artefact of the edge. |
| Change between two periods | 1.0.0 | Two endpoints are not a trend. A change computed between two years says nothing about the path between them, and is highly sensitive to whether either endpoint was unusual. Not valid where the series has a documented break. |
| Record extremes of a series | 1.0.0 | An extreme within the record Hydrionis holds, which is not necessarily an extreme within the record that exists. Says nothing about periods before the series begins. |
| Percentile rank within a series | 1.0.0 | A rank against this subject’s own history only. The percentile shifts as the record lengthens, so it is stated together with the span it was computed over. |
| Monthly reference normal | 1.0.0 | Twelve separate statistics, not one: a January normal describes Januaries and says nothing about July. Valid only where the reference period is substantially complete for that month, and only for quantities with a genuine annual cycle. It describes the reference period, not the present — a normal computed over a period that was itself unusual carries that through to every anomaly measured against it. |
| Anomaly against the same month’s normal | 1.0.0 | Compares a month with the same month in the subject’s own reference period, never with another subject and never with a different month. For a managed quantity such as reservoir storage, a negative anomaly may record an operating decision — a flood-control drawdown, a scheduled release — rather than a shortage, and this statistic cannot distinguish the two. |
| Ratio of two metrics | 1.0.0 | Only valid where both inputs cover the same subject and the same period, and where the two metrics are actually commensurable. A ratio of figures collected on different bases is arithmetic, not information. |
Rights
Derived values inherit the rights of every observation that fed them. A computed figure is never more freely usable than its most restrictive input: doing arithmetic on someone else’s data does not change whose data it is. Each value records the identifiers of its inputs and of their sources, so the inheritance can be checked rather than trusted.
Data behind this
Every figure above is computed from these datasets at build time rather than written into the text. If the underlying record changes, this page changes with it.
Citation
Hydrionis (2026), Release note: Hydrionis Derived Climatology v1.0, version 1.0. Retrieved from https://hydrionis.com/research/derived-climatology-v1-release-note/