Reconstructing gap data between GRACE and GRACE-FO based on multi-layer perceptron and analyzing terrestrial water storage changes in the Yellow River basin

Abstract

The GRACE gravity satellite ended in June 2017, and the GRACE-Follow On mission was launched in May 2018, resulting in about a year of missing data. In order to study the changes in terrestrial water storage over a long time series, it is necessary to fill in the data between the two generations of gravity satellites. This paper is based on the multi-layer perceptron (MLP), which is trained by soil moisture, soil temperature, evapotranspiration and precipitation of GLDAS and CPC as input parameters, and GRACE-derived equivalent water height (EWH) as output parameters to train the neural network. Taking the Yellow River basin as the study area, the missing EWH was obtained. By analyzing the time series of the EWH in the Yellow River basin, it is concluded that the terrestrial water storage in the study area from 2002 to 2020 shows a trend of decreasing at a rate of -0.51±0.03 cm·a-1. GRACE-derived EWH has a lag time of 2 to 3 months relative to precipitation, evapotranspiration and soil temperature. Wavelet analysis verifies that the EWHs calculated by GRACE, GLDAS and CPC have a strong correlation, and have obvious annual resonance periods.