Experiments with EOF-based Gravity Field Reconstructions Using SLR and GRACE Data

Low order coefficients of the gravity field can be determined using satellite laser ranging (SLR), a method that extends the gravitational data record across several decades. More recently, the Gravity Recovery and Climate Experiment (GRACE) mission has contributed monthly solutions of the gravity field to degree and order 60 allowing for the extraction of mass loss signals across the cryosphere. With this information scientists are able to quantify the melting cryosphere thus improving scientists' ability to determine the long-term impact to climate change. The objective of this work is to extend mass change data beyond the nine years of the GRACE mission using SLR data that both predates the GRACE mission and is expected to continue beyond it. This work develops a technique to fuse the two data sets by applying empirical orthogonal function (EOF) analysis to the GRACE data to isolate the temporal trends and spatial maps associated with the critical modes of mass change. The EOF modes are then reconstructed using SLR data allowing for a comparison of SLR reconstructed EOF modes and GRACE data products. By identifying the critical signals and the influence of the lower order coefficients it is possible to infer long term trends in the cryosphere based on the extensive SLR data record. This work is important for extracting information on mass changes in the cryosphere beyond the timeframe of the GRACE mission.