EOF analysis of the monthly gravity fields from GRACE and GRACE-FO 

<p>Empirical Orthogonal Function (EOF) analysis is applied to study the spatial structure and temporal feature of the time series of the global EWH from GRACE/GRACE-FO-derived gravity fields. The scaled PC time series for the corresponding trend spatial structure of GRACE appears to change from initially linearly decreasing to increasing around June 2013, while the trend is continuously increasing for GRACE-FO. The EOF spatial structure from the GRACE or GRACE-FO derived SHC (spherical harmonic coefficients) with size of 6x6 can improve recovering the time series of C30/C50 from the SLR data over the period prior to March 2012 when the LARES data were not available. With the EOF technique and a time variable gravity model applied for the higher degrees, a new time series of C20 and C30 is determined based on the temporal feature from SLR and the better EOF spatial structure determined from the SHC in GRACE (or GRACE-FO) solutions, which are less influenced by the higher-degree aliasing. The EOF-based estimates of C20 andC30 may provide an estimate better unified with the higher-degree part of the GRACE (for C20) and GRACE-FO gravity fields.</p>