Water and Energy budgets on short and long timescales

We have aimed to improve the understanding of regional water and energy budgets in large catchments from observations, focusing on the period 2002-2013. To do this we have utilised new available satellite data from the Gravity Recovery and Climate Experiment (GRACE).  Despite recent improvements in remote sensing capabilities, we still see inconsistencies amongst datasets. Observed surface energy fluxes from CERES and FluxCOM indicate unrealistic increases/decreases in surface energy storage over different catchments. We also see imbalances in the water budget, suggesting inaccuracies in the measurements. In order to assess these imbalances, we introduce a flux-inferred surface storage (FIS) for both water and energy, based on integrating the flux observations. This exposes mismatches in seasonal water storage as well as important interannual variability. We have produced optimised estimates for each component of the terrestrial water and energy budgets based on observations and their relative uncertainties. Our new optimisation approach ensures that flux estimates are consistent with total water storage changes from GRACE on short (monthly) and longer timescales, while also balancing a coupled long term energy budget. Flux adjustments remain small and are evaluated using a chi squared test. By using multiple data products, the optimisation reduces formal uncertainties on the budget variables. When compared with results from previous literature, our estimates show good agreement with GRACE variability and trends on account of the multiple timescale constraints imposed during the optimisation. We next aim to extend our approach to include carbon budgets alongside the water and energy budgets to produce a truly coupled Earth system cycling analysis, with applications such as testing Earth and climate circulation models.