Abstract
The net surface energy flux is central to the climate system yet observational limitations lead to substantial uncertainty. A combination of satellite‐derived radiative fluxes at the top of atmosphere adjusted using the latest estimation of the net heat uptake of the Earth system, and the atmospheric energy tendencies and transports from the ERA‐Interim reanalysis are used to estimate surface energy flux globally. To consider snowmelt and improve regional realism, land surface fluxes are adjusted through a simple energy balance approach at each grid point. This energy adjustment is redistributed over the oceans to ensure energy conservation and maintain realistic global ocean heat uptake, using a weighting function to avoid meridional discontinuities. Calculated surface energy fluxes are evaluated through comparison to ocean reanalyses. Derived turbulent energy flux variability is compared with the Objectively Analyzed air‐sea Fluxes (OAFLUX) product, and inferred meridional energy transports in the global ocean and the Atlantic are also evaluated using observations. Uncertainties in surface fluxes are investigated using a variety of approaches including comparison with a range of atmospheric reanalysis products. Decadal changes in the global mean and the interhemispheric energy imbalances are quantified, and present day cross‐equator heat transports are reevaluated at 0.22 ± 0.15 PW (petawatts) southward by the atmosphere and 0.32 ± 0.16 PW northward by the ocean considering the observed ocean heat sinks.
Highlights
The net surface flux (Fs ) plays a key role in determining the decadal surface temperature variability [Easterling and Wehner, 2009; Knight et al, 2009; Trenberth and Fasullo, 2013; Huber and Knutti, 2014; Watanabe et al, 2014]
Liu et al [2015] found that the divergence of horizontal atmospheric energy transports over land required adjustments to remove unrealistically large implied surface energy fluxes over land based upon simple energy budget arguments
Johnson et al [2016] estimated an uncertainty of ±0.1 WmÀ2 at 95% confidence level based on consideration of ocean heating trend uncertainty, but this applies to the 2005–2015 period
Summary
The net surface flux (Fs ) plays a key role in determining the decadal surface temperature variability [Easterling and Wehner, 2009; Knight et al, 2009; Trenberth and Fasullo, 2013; Huber and Knutti, 2014; Watanabe et al, 2014]. Since homogeneity and accuracy of computed fluxes are questionable [Mayer et al, 2013], an alternative approach is to combine satellite observations of top of atmosphere radiative fluxes with atmospheric energy transports from reanalyses to estimate the global net surface energy fluxes as a residual [Trenberth and Solomon, 1994]. Applying this strategy, Liu et al [2015] found that the divergence of horizontal atmospheric energy transports (hereafter: energy divergences) over land required adjustments to remove unrealistically large implied surface energy fluxes over land based upon simple energy budget arguments. The variability in the regional energy fluxes, updated estimates of interhemispheric energy imbalances, and cross-equatorial heat transports are provided using the new reconstructed data and accounting for the observed patterns of oceanic heat accumulation
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