57
4>)
were applied per wavelength, which resulted in some obser-
vations with an incomplete spectrum.
2.2.3 AErosol RObotic NE Twork-Ocean Color
'AERONET-OC)
AERONET-OC is a component of AERONET, including
sites where sun photometers operate with a modified mea-
surement protocol leading to the determination of the fully-
normalized water-leaving radiance (Zibordi et al., 2006,
2009). As a result of a collaboration between the Joint
Research Centre (JRC) and NASA to develop (Hooker et
al., 2000) and exploit (Zibordi et al., 2002) the technol-
0gy, this component has been specifically developed for
che validation of ocean colour radiometric products. The
strength of AERONET-OC is “the production of standard-
ızed measurements that are performed at different sites
with identical measuring systems and protocols, calibrated
using a single reference source and method, and pro-
cessed with the same codes” (Zibordi et al., 2006, 2009).
All high quality data (“Level-2”) were acquired from the
project website for 1l sites: Abu_Al_Bukhoosh (—25°N,
53° E), COVE_SEAPRISM (—-36°N, —75° W), Glo-
ria (44° N, — 29° E), Gustav_Dalen_Tower (—58°N, —
17° E), Helsinki Lighthouse (— 59° N, — 24° E), LISCO (—
40°N, — 73° W), Lucinda (— 18° S, — 146° E), MVCO (—-
41° N, — 70° W), Palgrunden (—58°N, — 13° E; Philipson
et al., 2016), Venice (- 45° N, — 12° E), and WaveCIS_Site_
CSIL6(—-28° N, — 90° W). The compiled variable was “rrs”.
Remote-sensing reflectance was computed from the original
‘fully-normalized” water-leaving radiance (see Sect. 2.2.2
for definition). The solar irradiance (“Fo”), which is not part
of the AERONET-OC data, was computed from the Thuil-
lier et al. (2003) solar spectrum irradiance by averaging “Fo”
over a wavelength-centred 10nm window. Data were com-
piled for the exact wavelengths of each record, which can
change over time for a given site depending on the specific
instrument deployed. In comparison with the previous ver-
sion of the compilation, the present OC-CCI data set version
3, now uses the “version 3” reprocessing of AERONET-OC
data (Zibordi et al., 2021).
2.2.4 SeaWIiFS Bio-optical Archive and Storage System
‘QeaBASS})
SeaBASS is one of the largest archives of in situ marine bio-
optical data (Werdell et al., 2003) with a long-established in-
ventory (Hooker et al., 1994). It is maintained by NASA’s
Ocean Biology Processing Group (OBPG) and includes mea-
surements of optical properties, phytoplankton pigment con-
centrations, and other related oceanographic and atmospheric
data. The SeaBASS database consists of in situ data from
multiple contributors, collected using a variety of measure-
ment instruments with consistent, community-vetted proto-
cols, from several marine platforms such as fixed buoys,
zarth Syst. Sci. Data. 14. 5737-5770. 202,
A. Valente et al.: A compilation of global bio-optical in situ data
handheld radiometers, and profiling instruments. Quality
control of the received data includes a rigorous series of pro-
tocols that range from file format verification to inspection
of the geophysical data values (Werdell et al., 2003). Radio-
metric data were mostly acquired through the “validation”
search tool, which provided in situ data with matchups for
particular ocean colour sensors (Bailey and Werdell, 2006).
The criterion in the search-query was defined to have the
minimal flag conditions in the satellite data, to retrieve a
greater number of matchups, and therefore in situ data. Re-
garding phytoplankton pigment data, the majority were ac-
quired through the “pigment” search tool, which provided
pigment data directly from the archives. As was stated in
the SeaBASS website, the “pigment” search tool was orig-
inally designed to return only in vitro fluorometric measure-
ments, which is consistent with our approach, but over time
chlorophyll-a measurements made using other methods (e.g.
in vivo fluorometry) were included in the retrieved pigment
data. In the pigment data used in this work, a large number
of in situ fluorometric measurements from continuous under-
way instruments were identified and discarded. These data
were initially identified from cruises with more than 50 ob-
servations per day and then re-checked in the SeaBASS web-
site to confirm whether indeed they were continuous under-
way measurements. A total of 120412 such measurements
were identified and discarded. Given the large volume of this
group of data, it is possible that some chlorophyll-a obser-
vations from in vivo methods may have escaped the scrutiny
and persisted into the final merged data set. The “pigment”
search tool was recently discontinued, and instead the “file”
search tool can be used, which was also used here to acquire
chlorophyll, as well as radiometric observations, for more
recent years. The remote sensing reflectance acquired from
the “file” search tool was corrected for the bidirectional ef-
fects (Morel and Gentili, 1996; Morel et al., 2002). The com-
piled variables from SeaBASS data were “rrs”, “chla_hplc”.
“Chla_fluor”, “aph”, “adg”, “bbp”, and “kd”.
2.2.5 NASA bio-Optical Marine Algorithm Data set
({(NOMAD)
NOMAD is a publicly-available data set compiled by the
NASA OBPCG at the Goddard Space Flight Center. It is a
high-quality global data set of coincident radiometric and
phytoplankton pigment observations for use in ocean colour
algorithm development and satellite-data product-validation
activities (Werdell and Bailey, 2005). The source bio-optical
data is the SeaBASS archive; therefore, many dependencies
axist between these two data sets, which were addressed dur-
ing the merging. The current version (Version 2.0 ALPHA,
2008) includes data from 1991 to 2007 and an additional
set of observations of inherent optical properties. The cur-
tent version was used in this work, but with an additional
set of columns of remote-sensing reflectance corrected for
the bidirectional effects (Morel and Gentili. 1996; Morel et
nttos://dol.org/10.5194/essd-14-5737-2022
