A Study On The Acquirability Of Mid-Depth Current Information By The ARGO Float

The action of the global ARGO project not only creates the actuality to observing the temperature and salinity profiles in the mid-and upper-ocean at real time, but also provides an unique opportunity by which people can observe the absolute velocity on mid-depth within the world oceans at near real-time.Based on the principle about the operating and measuring character of the ARGO float, we analyse the main error source in estimating the mid-depth current by the floats, as follows: the first is drifting on surface before (or after) locating when float is ending ascent (or beginning descent), the second is the velocity shear between different depths when float ascending (or descending). Others include positioning errors and the real depth when float submerged drifting on. And aiming at those, propose some special quality control schemes. On the ground, we discuss three methods there are directly estimating, correcting the position on surface and correcting the velocity shear for estimating the mid-depth current by the floats, moreover resort to the reanalyzed ocean data to reckon the error with the above methods respectively. It shows that the time-lag error is predominant during the estimating the current.Then based upon the principle of least square, in this paper progress an optimum analyse method. Using a sequence of surface time-position information recorded in ARGO files, we draw out these mid-depth velocities (1000,2000db) their relative errors are less than 20% from the ARGO in tropical Pacific during 2001.11-2004.8 after these method applied. Whereafter using that velocities compares with the reanalyzed current data of NCEP and of ECCO, the results suggest that: firstly the description of the reanalyzed data about the mid-depth velocity is deficiency, on average less 2~4cm/s than the observing by the float, but the ability of NCEP is excelled ECCO's. Secondly at practice the relatively information defaulted in ARGO files is too much so that the west Pacific on 2000db is the main region, where we could reckon the credible current on mid-depth by the ARGO float.