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Science Meetings

Validation of Aquarius Salinity with Argo: Errors Due to Collocation and Vertical Salinity Stratification
Riser, S. and Drucker, R. (13-Nov-13)

We validate Aquarius v2.0 level-2 sea surface salinities against Argo near-surface (nominal 5 m) salinities for the period 27 Aug 2011 through 31 Jul 2013, a period of 23 months. The validation consists of comparison of 16,625 collocated Argo/Aquarius data pairs. The global mean of the salinity difference is +0.003 PSU, with latitudinal variations of less than ±0.1 PSU within 60° of the equator. Low temperatures, high winds, and rain affect 37% of the data and account for about 40% of the standard deviation. Low-pass filtering can reduce the error by about 15%. We discuss three potential collocation errors due to horizontal, temporal and vertical displacements of measurement and show that none of these are significant for global validation of Aquarius. We use NASA's TRMM data to analyze the contribution of salinity stratification to validation error. There is evidence of strong vertical stratifications >0.1 PSU lasting ~3-6 hours, but these events occur infrequently and contribute less than 0.03 PSU bias in the tropics and 0.02 PSU globally.