Tuesday, June 20, 2017

Please be informed that PO.DAAC has released two important statements for the JPL GRACE Tellus Level-3 ocean-mass product (ftp//podaac-ftp.jpl.nasa.gov/allData/tellus/L3/ocean_mass/RL05/ascii/).

1.  The monthly solutions 11/2017 and 12/2017 were produced off of GRACE Level-2 fields with only a single spacecraft (GRACE-1) accelerometer due to the persisting battery issues in GRACE-2. This “ACC-transplant” approach results in significantly higher noise in the Level-2 data fields and is also affecting Level-3 grids. While a detailed analysis is ongoing and future improvements might increase the S/N ratio, we recommend that users use these data as preliminary and with caution, and apply conservative uncertainty estimates that are at least 3x (factor 3) larger than described in [Chambers & Bonin, 2015]. See https://grace.jpl.nasa.gov/data/get-data/monthly-mass-grids-ocean/ for more details.

2.  We recently discovered a bug in the post-processing GRCTellus OCN fields from 06/2013 onwards.  This bug occurred in the “land leakage correction” procedure, and consequently mainly affected near-coastal ocean regions; interior ocean grids points (more than about 1000 km away from coastlines) where only minimally impacted.

The PO.DAAC has updated and replaced all ocean data grids from 06/2013 onwards and recommends that users download the new data fields for consistency.

For more information, please see the readme.txt file at:  ftp//podaac-ftp.jpl.nasa.gov/allData/tellus/L3/ocean_mass/RL05/README.txt.