Uncovered spurious jumps in the GRACE atmospheric de-aliasing data: potential contamination of GRACE observed mass change

Abstract

In Gravity Recovery and Climate Experiment (GRACE) data processing, the effect of high-frequency mass variations in the atmosphere and ocean is taken into account during temporal gravity field modelling to minimize temporal and spatial signal aliasing. We find two spurious jumps in the atmosphere and ocean de-aliasing level-1b (AOD1B) data product, which occurred from January to February in both 2006 and 2010. These jumps attain about 7 cm of equivalent water thickness (EWT) change in some regions including the Qinghai-Tibetan Plateau and South America, and appear to be spurious biases caused by the resolution change in the European Centre for Medium-Range Weather Forecasts (ECMWF) model at the beginning of 2006 and 2010, respectively. These uncovered jumps are unlikely to be real atmospheric signals primarily because they are absent in the ECMWF Re-Analysis (ERA-Interim) model. Here, we show that these spurious jumps, uncovered in both the Release 04 (RL04) and the Release 05 (RL05) AOD1B data, would produce jumps of the same magnitude with opposite signs, thus may contaminate the GRACE data products in specific regions of the world. As a consequence, estimates of regional mass changes including glacier mass balance could potentially have an error at the same level of these jumps.