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produce alternating periods of drought and years of heavy precipitation in California (Cayan et al., 1999) (Figure S1 in Supporting Information S1). Anthropogenic greenhouse gases have warmed Earth by 0.9°C since 1950, creating harsher droughts and fiercer flooding in the west U.S. (IPCC, 2021). Severe drought struck California from October 2011 to October 2015 (Griffin & Anchukaitis, 2014;Swain et al., 2014). Precipitation was low and temperature high during the 4 years (PRISM Climate Group, 2017). Snow accumulation in the Sierra Nevada in the winters of 2014 and 2015 was less than 1/4 of its average (NOHRSC, 2004), resulting in a shortfall of freshwater available for agriculture and urban centers.

<p>This talk will provide a status update on Level-2 data processing at JPL.  Included will be an overview of data products currently delivered to the community, including gravity fields with the updated accelerometer transplant product.  Assessments of data quality and error levels, along with detailed discussions of the solution strategy will be included.  A comparison of LRI and KBR gravity fields will be provided..  A look towards an RL07 reprocessing of GRACE and GRACE-FO will additionally be provided.  The reprocessing plans to incorporate the estimation of a full noise covariance model of the satellite observations in the gravity estimates.  Preliminary results incorporating this strategy will be shown and discussed.</p>

The Gravity Recovery and Climate Experiment (GRACE) gravitational models suffer from a dominant systematic error, usually referred to as “longitudinal stripes.” These stripes contaminate useful geophysical signals and limit the spectrum of geoscience applications that can be benefited from GRACE and GRACE‐Follow On. Analyses of the spatiotemporal structure of latitudinal stripe profiles show consistent spectral characteristics throughout three years of monthly solutions. Using an elegant combination of GRACE sampling characteristics and advanced moiré theory, we show that the GRACE stripes are sub‐Nyquist (pseudo‐moiré) artifacts arising from the oversampling of the Earth's low‐frequency static disturbing potential (geoid) along the parallels. The low‐frequency geoid modulates the total sampled gravitational signal with a frequency near mnfs, where fs is the sampling frequency of the GRACE ground track “bundles” along the parallels of latitude, and m and n are mutually prime integers, with 2m ≤ n.

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