Recent updates to the NCEP SST analysis and comparison with OSTIA and CMC products

Presented at the GHRSST XXIII international science team meeting, 27 June-1 July 2022, online and in-person (Barcelona). #GHRSST23 

Short abstract

The NCEP Near-Surface Sea Surface Temperature (NSST) has been operational since 2017. It has been integrated within the operational Global Data Assimilation System, utilizing foundation temperature as the analysis variable. Products from OSTIC and CMC similarly use foundation temperature, but integrate more observation into the production of their SST analyses.

An upgrade to NSST has been prepared that targets expanded observational coverage by including additional satellites and reducing the thinning mesh utilized for data selection for SST-sensitive satellite data. Additional changes to the background error correlations have been tested to further constrain data impacts locally.  A tighter quality control for AVHRR radiance with cloud flag in the data set is included in this update as well. The combined upgrade package shows better fit to both in situ and satellite observations. As expected, the changes have also resulted in resolving higher resolution spatial structures and improved the representation of the diurnal variability of the foundation temperature for related areas. 

An inter-comparison among L4 products from NCEP NSST, OSTIO, and CMC has been performed and includes calculation of RMS and bias relative to OSTIA for specific areas. Overall, OSTIA and CMC products are closer to each other than to NSST. However, for some local areas, any of the three can be the outlier.  The evaluation suggests that the individual analysis can be improved by exploring root causes for the differences among products.