Nong et al. 
Argo Data 1999-2019 
Argo Float Mission 
Profiling 
Float 
| 
Ja 
FIGURE 1 | A schematic illustration of the standard Argo “park-and-profile” mission. The surface interval of —20 min is applicable to floats that use Iridium satellite 
communication; floats that use ARGOS satellite communication require surface interval of several hours for data telemetrv. Source: Woods Hole Oceanographic 
Institution]. 
TABLE 1 | The various float types and their primary vertical sampling schemes as 
a percentage of the total number of primary profiles in Arao, as of April 2019 
\ 
Primary Discrete Bin-averaged Mixed 
vertical mode continuous mode 
sampling mode 
scheme 
Float 
ype N 
APEX 
>ROVOR/ARVOR 
SOLO-I/SOLO-I/S2A 
NAVIS 
NEMO 
NOVA 
NINJA 
TOTAI 
46% 
<1% 
<1% 
<1% 
<1% 
<1% 
<1% 
4 7: 
3% 
15% 
19% 
4% 
14 
1% 
„1%, 
AR 
<1% 
Se 
directly. From temperature, pressure, and conductivity, salinity 
(in PSS-78) can be computed by using the equation of state for 
seawater (Fofonoff and Millard, 1983). 
Sea-Bird Scientific has supplied two main CTD models for 
Argo floats: the SBE-41 and the SBE-41CP. The SBE-41 operates 
rontiers in Marine Science | www.frontiersin.orı 
in the spot-sampling mode only and collects discrete samples 
according to a pre-set pressure table, with the CTD pump turned 
off between samples. The SBE-41CP has the capability to operate 
in both the spot-sampling mode and the continuous-profiling 
(CP) mode. When used in the CP mode, the CTD pump remains 
on and samples are collected at nominally 1 Hz. These continuous 
data are then bin-averaged onboard the float before they are 
transmitted by satellite. 
The manufacturer-quoted initial accuracies for the SBE- 
11/41CP, as of 2019, are 2 dbar for pressure*, 0.002°C for 
temperature, and 0.0035 PSS-78 for salinity. Some float- 
providing groups conduct independent CTD accuracy checks to 
ensure that the sensor calibrations are within the manufacturer’s 
specifications before float deployment. The Euro-Argo group 
performs systematic tests of profiling floats in Ifremer’s 20 m- 
depth seawater pool. Floats are tested simultaneously in batches 
of 10-40, and multiple test cycles (typically 6) are conducted over 
a 3-day period. The 20 m-depth profiles and park-phase data 
at pool depth are compared at sensor resolution level. As the 
test pool is a stable seawater environment, float sensors whose 
*The pressure accuracy specification for the SBE-41/41CP was changed from 2.4 
dbar to 2 dbar in 2011 by Sea-Bird Scientific 
Qanteambear 2020 1 Valııme 7 1 Article 701