Downward longwave radiation is not independent of surface temperature

Vargas Zeppetello, L. R., Donohoe, A., & Battisti, D. S. (2019). Does surface temperature respond to or determine downwelling longwave radiation? Geophysical Research Letters, 46, 2781–2789. https://doi.org/10.1029/2019GL082220

Downward longwave radiation (DLR) is often assumed to be an independent forcing
on the surface energy budget in analyses of Arctic warming and land-atmosphere interaction. We use radiative kernels to show that the DLR response to forcing is largely determined by surface temperature perturbations. We develop a method by which vertically integrated versions of the radiative kernels are combined with surface temperature and specific humidity to estimate the surface DLR response to greenhouse forcing. Through a decomposition of the DLR response, we estimate that changes in surface temperature produce at least 63% of the clear-sky DLR response in greenhouse forcing, while the changes associated with clouds account for only 11% of the full-sky DLR response. Our results suggest that surface DLR is tightly coupled to surface temperature; therefore, it cannot be considered an independent component of the surface energy budget.

 

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