The general description is:
The system uses the Navy Coupled Ocean Data Assimilation (NCODA) system
(Cummings, 2005; Cummings and Smedstad, 2013) for data assimilation.
NCODA uses the 24-hour model forecast as a first guess in a 3D
variational scheme and assimilates available satellite altimeter
observations, satellite, and in-situ sea surface temperature as well as
in-situ vertical temperature and salinity profiles from XBTs, Argo
floats and moored buoys. Surface information is projected downward into
the water column using Improved Synthetic Ocean Profiles (Helber et al.,
There are tables of observation sources in the Cummings papers, and the same kinds of observations are assimilated now but the details depends on what is available in near real time and may change over time.