Aquarius SSS Space/Time Biases With Respect to Argo Data
[12-Nov-2014] Hacker, P., Melnichenko, O., Maximenko, N., and Potemra, J.
Presented at the 2014 Aquarius/SAC-D Science Team Meeting
The Aquarius/SAC-D satellite provides an opportunity to observe near-global sea surface salinity (SSS) with unprecedented space and time resolution not available by other components of the Global Ocean Observing System. In order to evaluate and quantify the potential utility of the SSS data for global and regional studies of SSS variability, our research group has been using the Level-2, three-beam swath data and Argo data to characterize and quantify systematic space/time biases and random errors on a global grid. Despite continuing Level-2 product improvement of Aquarius data over the past three years, significant ascending/descending and inter-beam space/time biases with respect to Argo data persist. Time-mean and annual biases are particularly significant. For the present version 3.0 data, our analyses include quantifying the mean spatial biases for ascending and descending data for each of the three beams (typical range of +/- 0.25 psu), and 3-year mean and time-varying biases for the standard Aquarius and SST-adjusted SSS products from September 2011 to August 2014 (typical range of =/- 0.25 psu). An EOF analysis provides the amplitude and spatial structure for the first three significant components, which account for ~50% of the time-varying Aquarius minus Argo SSS bias. The first two components are annually varying with a 3-month lag; the third component is primarily semi-annual. The amplitude of the annual cycle in the bias field varies spatially from 0-0.2 psu and can be a significant bias compared to the Argo-derived annual cycle regionally.