Seasons

The seasonal scale is the grid’s second scale, built by the same machinery as the monthly one. A season is judged against the same season of other years, exactly as a July is judged against Julys.

You name only the first season. The rest follow by stepping through the year in blocks of the same length.

fluxatlas record.csv -o atlas.html --seasons DJF      # the default: the usual four
fluxatlas record.csv -o atlas.html --seasons JJA      # the same four, named from summer
fluxatlas record.csv -o atlas.html --seasons DJFMAM   # two half-years
fluxatlas record.csv -o atlas.html --seasons 12,1,2   # the same as DJF
fluxatlas record.csv -o atlas.html --seasons none     # no seasonal scale at all

fa.build_atlas("record.csv", "atlas.html", variables=["TA"], seasons="DJFMAM")

What the specification accepts

Month initials. Read as a run of consecutive months rather than letter by letter, because three initials name two months each. JJA is June, July and August, since those three are consecutive and no other reading is. DFJ is refused.

Month numbers. 12,1,2, separated by commas or whitespace.

none, and also off, no, or empty. The scale is dropped, for a site whose year has no seasons.

A season has to be 1, 2, 3, 4, 6 or 12 months long, so that the derived seasons tile the year exactly once. Five months would leave a remainder with nowhere to go, and is refused with that explanation. The value is validated before the file is opened.

Naming, and what the page states

The four meteorological seasons have English names and are labelled with them. Anything else is named by its months, which is the honest label for a division the page made at your request, and the page states the scheme in a sentence:

2 seasons of 6 months, derived from the first one this atlas was built with: DJFMAM, JJASON. This is not the usual four-season division; every figure on this scale is taken over the months named.

Nothing about a tile labelled JJASON tells a reader it is half a year rather than a quarter, so the page says it.

A one-month scheme cannot key on initials, since March and May are both M. The key identifies the span in the payload, so such a scheme is keyed and labelled by the month abbreviation instead.

The year a season belongs to

A season that crosses the new year is labelled by the year of its last month. A winter is the winter of its January, which is the usual convention. season_shift derives which of a season’s months fall in the previous calendar year, so nothing hard-codes December.

Spans are grouped by season_ids, an integer year * 100 + slot built from the month.

Which badges travel to the seasonal scale

Badges defined on a z-score, a percentage of normal or a rank travel, because they mean the same thing over three months as over one.

Badges defined on a count of days, or on a run of them, do not. Five frost days is a remarkable January and an unremarkable winter. The counts still appear on a season’s page as numbers, not as claims.

What this replaced

SEASON_FREQ = "Q-NOV", which borrowed pandas’ quarters and could only ever express four equal seasons.