On Tide Aliasing in GRACE Time-Variable Gravity Observations

Aliasing error induced by tide-related high frequency mass variations is one of the most significant errors in the Gravity Recovery and Climate Experiment (GRACE). In the present work, we evaluated the 161.0-day S-2, 171.2-day P-1, and 322.1-day S-1 ocean tide aliasing in GRACE latest RL06 data based on nearly 15 years of observation from 2002 to 2017. Tide aliasing was still obvious for current GRACE observations, especially for S-2 and P-1 aliasing. S-2 aliasing was mostly evident over West Antarctica, and was a clearly eastward propagation that travelled around Antarctica in about 2 years, while P-1 showed strongest aliasing over South Greenland. More seriously, we found that GRACE mascon data showed an extremely large aliasing error. The mascon data may have unintentionally amplified the aliasing error on land due to the regularization (or constraint) applied for reducing signal leakage. Enough attention must be paid to tide aliasing when using GRACE for assessing mass variations at high latitudes (e.g., glaciers in polar regions) which can cause potential obstacles to estimation of actual seasonality.