Quantification of energy flows through the climate system using a new generation of reanalysis products

Abstract:

The degree of consistency between the variability of energy storage and energy fluxes through the climate system on both global and regional scales are an important quality indicator for reanalyses and other climate data sets. This contribution presents various aspects of the Earth’s energy budget as evaluated from ECMWF's most recent reanalysis efforts, most notably the fifth-generation atmospheric reanalysis (ERA5) and Ocean Re-Analysis Pilot 6 (ORAP6), and will also touch upon recent advances in diagnostic methods.

We show that energy budgets evaluated from ERA5 are of improved quality compared to those from earlier reanalysis products in terms of physical consistency, temporal stability, and useful resolution. The latter mainly concerns the divergence of atmospheric energy transports, which now can be used at much higher resolution without excessive spectral noise. Thus, we can combine the divergences with satellite-based estimates of net radiation at top-of-the atmosphere (TOA) to infer fields of net surface energy flux at a reasonably high resolution of 1°. Various diagnostics reveal that the resulting surface flux estimates exhibit a low bias and rich spatial detail, making them a useful dataset also for climate model validation.

Another focus of this contribution is the consistency of inferred surface energy exchanges and TOA fluxes with ocean heat content variability from the new ocean reanalysis ORAP6. In addition to the enhanced resolution of ¼°, which has been found to be key for a more realistic representation of global OHC signals, ORAP6 uses atmospheric forcing from ERA5. The impact of this advancement on the accuracy of diagnostics of heat exchanges in the coupled climate system will be addressed.

In conclusion, this contribution highlights recent advances in observation-constrained estimates of energy flows through the Earth’s climate system, owing to improvements in both data quality and diagnostic methods.