A. Valente et al.: A compilation of global bio-optical in situ data 
TI TTTTITT — tt tt TtT7 
NOMAD (N=2921) 
MERMAID (N=337) 
BOUSSOLE (N=12) 
SeaBASS (N=125) 
AWI (N=12) 
SOASTCOLOUR (N=227 
TARA (N=11) * 
— NASA 0C4 - 
= NASA OC4E 
X 
0.1- 
0.001 
0.01 0.1 1 10 100 
chlorophyll-a concentration (mg 0) 
Figure 11. A remote-sensing reflectance maximum band ratio (as 
defined in text) ([443,490,510]/555 or [443,490,510]/560 if 555 
not available) as a function of chlorophyll-@ concentration. All 
chlorophyll data were considered, but for a given station, HPLC 
data were selected if available. Data within 2nm of the wave- 
lengths were used. For reference, the solid and dotted lines show 
the NASA OC4 and OC4E v6 standard algorithms, respectively 
(https://oceancolor.gsfc.nasa.gov/atbd/chlor_a/, last access: 18 De- 
cember 2022). The total number of points was 3645, of which 80 % 
were from NOMAD. 
are mainly from recent years (2019-2021) and from updates 
of AERONET-OC, BOUSSOLE, MOBY, MERMAID, and 
AWTI. The new data extended the temporal coverage towards 
more recent years, but the statistical distribution of values 
and the spatial coverages (discussed below) have essentially 
remained the same when compared to the previous version 
(Valente et al., 2019). This is explained by most of the new 
observations coming from continuous time series at fixed the 
locations (AERONET-OC, BOUSSOLE, MOBY). 
The distribution of the remote sensing reflectances at 
44Xnm and 55Xnm is provided in Fig. 2a and b, re- 
spectively. Data were first searched at 445 and 555nm, 
and then with a search window up to 8nm, to include 
also data at 547nm. Median values at 44Xnm ranged 
from 0.003 m7! (AERONET-OC) and 0.009 m7! (MOBY), 
whereas at 55X nm the median values lie between 0.001 m! 
(AWD) and 0.007 m 7! (COASTCOLOUR). The observations 
remain unevenly distributed between each month of the year 
in both hemispheres, with the summer months having higher 
data representation (Fig. 3). The Northern Hemisphere has 
also more data than the Southern Hemisphere (Fig. 3). As a 
quality control indicator, reflectance band ratios were plot- 
:ed against each other (490 : 555 versus 412 : 443, Fig. 4). 
Most points are within the boundaries of the NOMAD data 
set, but some scattered points were found. These points were 
retained to allow further manipulation with different quality 
control criteria. The geographic distribution of the remote- 
sensing reflectance stations (Fig. 5) still show a higher num- 
ber of observations in some coastal regions. such as those of 
attos://doi.org/10.5194/essd-14-573 /-20U2, 
5757 
North America and Northern Europe. Away from continental 
margins, the Atlantic Ocean has the highest density of ob- 
servations. Best geographic coverage is provided by the NO- 
MAD database. Data from SeaBASS is also well dispersed in 
space but fewer in number. Data from MERMAID are mainly 
located along the coasts of Europe, North America, and the 
central region of the North Atlantic Ocean. The observations 
from AERONET-OC, BOUSSOLE, COASTCOLOUR, and 
MOBY are concentrated in specific sites around the world, 
while AWT data are available for the Atlantic and Arctic 
Oceans. TARA data are spread across several regions, with 
highest data density in the Mediterranean Sea. 
Observations of chlorophyll-a concentration were divided 
ınto those measured by fluorometric or spectrophotometric 
methods (“chla_fluor””), and HPLC methods (“chla_hple’”). 
A comparison of the two types of measurements, when 
available at the same station (Fig. 6), shows good agree- 
ment (Trees et al., 1985). No data were filtered for this 
analysis and the good correlation can be explained in part 
by the quality control measures implemented by the data 
providers and curators of repositories such as NOMAD 
and SeaBASS (Werdell and Bailey, 2005). The total num- 
ber of stations with concurrent observations of “chla_fluor” 
and “chla_hple” is 5953, with contributions from SeaBASS 
(39 %), TPSS (16 %), PALMER (14 %), NOMAD (11 %), 
BATS (5%), COASTCOLOUR (4 %), MERMAID (4 %), 
HOT (4 %), and AMT + GeP&CO + BODC + CCELTER + 
CALCOFI (3 %). The “chla_fluor” observations are available 
in 61 317 stations (rows), with values limited to the range be- 
tween 0.001 to 100 mg m”* (Fig. 7). They are from NOMAD 
(2350), SeaBASS (18 575), MERMAID (480), ICES (5421), 
HOT (755), AMT (396), ARCSSPP (189), BARENTSSEA 
(7188), BATS (356), BIOCHEM (4592), BODC (895), CAL- 
COFI (5396), COASTCOLOUR (3322), CCELTER (468), 
CIMT (204.), ESTOC (100), GEPCO (56), IMOS (1136), 
PALMER (3237), SEADATANET (5403), and TPSS (1000). 
The total number of “chla_hple” observations is 27215, 
ranging from 0.002 to 99.8 mg m”? (Fig. 7), with contribu- 
tions from NOMAD (1309), SeaBASS (10257), MERMAID 
(707), ICES (2994), HOT (222), GeP&CO (1536), BOUS- 
SOLE (577), AMT (1359), AWI (2343), BATS (334), BODC 
(735), COASTCOLOUR (848), IMOS (340), MAREDAT 
(1024), PALMER (1525), TPSS (1002), and TARA (161). 
Compared to the previous version (Valente et al., 2019), the 
“Chla_hple” observations increased by — 16% (23550 to 
27215). As for the “chla_fluor” observations, they have de- 
creased (from 61 525 to 61317), which is explained by the 
added observations (N = 3033) being less than the removed 
stations due to quality control (N = 3241; see Sect. 2.2.6). 
The new data points come from updates of BOUSSOLE, 
MVERMAID, SeaBASS, HOT, AMT, PALMER, CCELTER. 
CALCOFI, AWI, and IMOS. 
The combined chlorophyll data set (all chlorophyll data 
considered, but for a given station, HPLC data were selected 
if available), has a total of 82 543 observations. which repre- 
Earth Syst. Sei. Data, 14. 5737-5770. 2022