Beam attenuation
Beam attenuation coefficient
1/mkey beam_attenuationNERC P01 ATTNXXZZP06 units UPRMseries beam_attenuation
CalCOFI holds 619,045 values of it from 8,588 sampling events in one dataset, 1993–2026, from the surface to 3,630 m. At 200–500 m it has fallen 5.70 per decade since 1993.R How far light travels through the water is set by the particles in it, most of them living or lately alive, so a clear cast and a turbid one are a statement about the plankton as much as about the light.C
- 619,045
- values
- 0
- flagged
- 1993–2026
- years
- 1
- dataset
- 1–3,630 m
- depth
- 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
beam_attenuation· source columnbat· flag columnbatqno bound declared
Explorera depth section vs normaldb-queryERDDAPThis page as JSON R · Python · Parquet
Every way in 8 ways · ERDDAP · Parquet · R · Python · JSON
Read from measurements.json of release v2026.11.05, 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.
ExplorerExplorer · a depth section vs normaldb-querySELECT * FROM read_json('…/v2026.11.05/catalog.json')
-- objects[] WHERE table = 'obs_env'
-- AND partition_value = 'beam_attenuation'library(calcofi4r)
con <- cc_get_db() # the promoted release
tbl(con, "obs_env") |> filter(measurement_type %in% c("beam_attenuation"))import calcofi4py as cc
con = cc.cc_get_db()
con.sql("SELECT * FROM obs_env WHERE measurement_type IN ('beam_attenuation')").df()How it is measured CTD-mounted transmissometer
A transmissometer on the CTD; its light-path voltage is calibrated daily (in-air 100% and blocked 0% readings) and converted to percent transmission and a beam attenuation coefficient. (calcofi.org CTD FAQ circa 2020)
CTD FAQ circa 2020 on calcofi.org ↗Why it matters 3 ways to say it
other ways to say why · 2
- Beam attenuation is used as a stand-in for the particles the water carries, including the ones sinking out of the sunlit layer. needs a citation before it can be the pick
- Wikipedia A transmissometer or transmissiometer is an instrument for measuring the extinction coefficient of the atmosphere and sea water, and for the determination of visual range. It operates by sending a narrow, collimated beam of energy through the propagation medium. Transmissometer · CC BY-SA 4.0 · rev. 1328380936
The record’s own history 7 depth bands against the 1993–2013 normal
Each year against the normal i
Deeper than the climatology reaches: 3,237 values at 2000+ m have no
normal to depart from, because the release’s climatology stops at its
deepest built bin. Carrying it to the bottom is one argument of
build_climatology() and puts these bands on the page too.
i
Deeper than the climatology reaches: 3,237 values at 2000+ m have no
normal to depart from, because the release’s climatology stops at its
deepest built bin. Carrying it to the bottom is one argument of
build_climatology() and puts these bands on the page too.
Units and range 1/m · no bound declared declared · 0 flagged
1/m · P06 units UPRM
details
- bounds
- No physical bound is declared for this series in metadata/measurement_type.csv, so nothing is enforced at the ingest and the range below is simply what the release carries.
- observed
- CTD Cast Files
beam_attenuation-12.29 · median 0.5899 · 75.64 1/m (5th–95th percentile 0.2835–30.63) - flags
- CTD Cast Files
beam_attenuationbatqon 402 of 619,045 rows:0402; qual_ok keeps 619,045. The codes are this dataset's own vocabulary, uninterpreted. - 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.
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 depth · by month 1–3,630 m · every month
By depth i
Values per depth band at the release grain, one thin bar per series. The bands are the
record's own (0-10 … 2000+ m).
i
Values per depth band at the release grain, one thin bar per series. The bands are the record's own (0-10 … 2000+ m).
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, v2026.11.05
Cite the release; each dataset's own citation, licence and DOI are on its page — CTD Cast Files. The Explorer's Share → Cite writes it for the view you make.