The seasons every CalCOFI anomaly and season filter use: DJF, MAM, JJA, SON

Since calcofi4db 4.34.0 (Rasmus Swalethorp, 2026-10-16: "keep the quarters matching seasons, so quarter 1 would be Dec-Feb"; agreed 2026-10-27) a season is three calendar months starting in December — winter DJF, spring MAM, summer JJA, fall SON — and December counts toward the following year's winter (Dec 2025 + Jan-Feb 2026 = winter 2026, the climatology convention, so a winter is never split across two years). The quarter column the release carries on climatology, obs_env and obs_bio keeps its 1-4 vocabulary with this meaning: 1 = DJF, 2 = MAM, 3 = JJA, 4 = SON (through v2026.10.30 it was Q1 Jan-Mar ... Q4 Oct-Dec).

Usage

cruise_quarter_sql(month_expr)

cruise_season_sql(month_expr)

cruise_season_year_sql(month_expr, year_expr)

cruise_quarter(month)

CC_SEASONS

Arguments

month_expr: SQL expression giving the cruise's month (1-12).
year_expr: SQL expression giving the calendar year of that month.
month: integer month (1-12), vectorised.

Value

a character SQL fragment.

Details

cruise_quarter_sql() / cruise_season_sql() / cruise_season_year_sql() are the one rule as DuckDB SQL over a month (and year) expression, so the release, the Explorer's slices and a notebook cannot disagree; cruise_quarter() is the vectorised R twin.

Examples

cruise_quarter_sql("month")
#> (CASE WHEN (month) IN (12, 1, 2) THEN 1 WHEN (month) IN (3, 4, 5) THEN 2 WHEN (month) IN (6, 7, 8) THEN 3 WHEN (month) IN (9, 10, 11) THEN 4 END)
cruise_season_year_sql("month_median", "year(date_median)")
#> (CASE WHEN (month_median) = 12 THEN (year(date_median)) + 1 ELSE (year(date_median)) END)::SMALLINT