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About Qnet and related budget imbalance


Net heat flux, Qnet, is computed as:

Net Heat Flux

Qnet = QSW - QLW - QLH - QSH.

where QSW denotes net downward shortwave radiation, QLW net upward longwave radiation, QLH latent heat flux, and QSH sensible heat flux. The unit is W/m2.


Please pay attention to the following issues when using Qnet constructed from combining ISCCP with OAFlux-1° products.

  • Currently, the combined ISCCP+OAFlux Qnet data set is capable of depicting flux variability on synoptic –seasonal-interannual timescales (see Yu et al. 2006; Yu et al. 2007). However, Qnet is not balanced; there is a net residual of O(30W/m2) when averaged over the global oceans.
  • The cause of the imbalanced surface heat budget is multifaceted. There are large uncertainties in surface radiation, flux-related variables, and turbulent exchange coefficients in bulk flux parameterizations, which all contribute to the budget imbalance. See Yu 2019.