Chlorophyll maximum depth
Depth of the chlorophyll-a maximum (DCM): the highest value of a 3 m running mean
mkey chl_max_depthP06 units ULAAseries chl_max_depth
one value per cast One value per cast. This measurement is worked out once for each cast rather than read at every depth, so it has no depth profile and no anomaly against a normal; its values are rows of sample_measurement, not of obs_env.
CalCOFI holds 9,255 values of it from 9,255 sampling events in one dataset, 1993–2026, one per cast.R Chlorophyll is highest at a depth, not at the surface; where that depth lies marks where light and nutrients meet, and a surface-only reading, which is all ocean colour sees, misses it.C
- 9,255
- values
- 0
- flagged
- 1993–2026
- years
- 1
- dataset
- every month
- months
Measured in
1 dataset
i
One row per series, one cell per year, darker with more values — the same strip the front
door draws per dataset and a species page draws per taxon. Each row is one dataset's own
measurement_type; the label is written once, in the title above.
i
One row per series, one cell per year, darker with more values — the same strip the front door draws per dataset and a species page draws per taxon. Each row is one dataset's own measurement_type; the label is written once, in the title above.
-
series
chl_max_depth· source columnest_chlorophyll_a_sta_corrone value per cast no flag at this grain no P01 concept
Explorerdb-queryThis page as JSON R · Python · Parquet
Every way in 6 ways · Parquet · R · Python · JSON
Read from measurements.json of release v2026.10.21, written at release by calcofi4db::build_measurements_catalog() beside taxa.json. The catalog's index is /measurements/; the JSON-LD on this page is a schema.org/DefinedTerm in the NERC P01 term set with a PropertyValue per series.
Explorerdb-querySELECT * FROM read_json('…/v2026.10.21/catalog.json')
-- objects[] WHERE table = 'sample_measurement'
-- then filter the rows:
-- measurement_type IN ('chl_max_depth')library(calcofi4r)
con <- cc_get_db() # the promoted release
tbl(con, "sample_measurement") |> filter(measurement_type %in% c("chl_max_depth"))import calcofi4py as cc
con = cc.cc_get_db()
con.sql("SELECT * FROM sample_measurement WHERE measurement_type IN ('chl_max_depth')").df()How it is measured Computed from the CTD fluorometer profile (corrected to bottle chlorophyll-a)
The depth of the chlorophyll-a maximum: the depth of the highest value of a 3 m running mean of the station-corrected CTD chlorophyll-a profile, so one narrow spike is not taken for the peak. (the record's own derivation (measurement_type.csv); questions Q02 (Rasmus Swalethorp, 2026-09-23))
- smooth the 1 m profile with a 3 m running mean
- take the depth of the highest smoothed value
Why it matters 4 ways to say it · EOV Phytoplankton biomass and diversity
the GOOS specification sheet for this Essential Ocean Variable lists it
other ways to say why · 3
- It is the depth of the highest value after the CTD fluorometer profile is smoothed, so a single narrow spike is not taken for the maximum. needs a citation before it can be the pick
- Wikipedia Chlorophyll a source
- Wikipedia The deep chlorophyll maximum (DCM), also called the subsurface chlorophyll maximum, is the region below the surface of water with the maximum concentration of chlorophyll. The DCM generally exists at the same depth as the nutricline, the region of the ocean where the greatest change in the nutrient concentration occurs with depth. Deep chlorophyll maximum · CC BY-SA 4.0 · rev. 1374126571
Units and range m · 0 … 200 declared · 0 flagged
m · P06 units ULAA
details
- bounds
- The registry declares
0 … 200 mforchl_max_depth; a value outside it is dropped at the ingest (drop_out_of_bounds()). - observed
- CTD Derived Products
chl_max_depth1 · median 34 · 195 m (5th–95th percentile 3–100) - flags
- CTD Derived Products
chl_max_depthcarries no quality code at the release grain; qual_ok keeps all 9,255. - baseline
- A monthly climatology exists for this measurement (the release's climatology table: 1993–2013, dataset × station × the cruise's month × 10 m bin), so the Explorer can draw anomalies against it rather than values.
- derivation
- calcofi4db::ctd_chl_max(window_m = 3) on est_chlorophyll_a_sta_corr: the depth of the highest value of a 3 m running mean (each 1 m bin with its neighbours, truncated at the ends of the profile); the provider's definition (Rasmus Swalethorp 2026-09-23, questions Q02)
The familiar scale i
Bars are each series' 5th–95th percentile, the line its minimum to maximum, the ring its median;
the marks are metadata/measurement_scale.csv's, each hovering to its own source.
i
Bars are each series' 5th–95th percentile, the line its minimum to maximum, the ring its median;
the marks are metadata/measurement_scale.csv's, each hovering to its own source.
By month every month
By month i
Values per calendar month, one row per series: CalCOFI's quarterly cruises show as peaks in
the months the ships sail.
i
Values per calendar month, one row per series: CalCOFI's quarterly cruises show as peaks in the months the ships sail.
Cite the release, v2026.10.21
Cite the release; each dataset's own citation, licence and DOI are on its page — CTD Derived Products. The Explorer's Share → Cite writes it for the view you make.