EGU22-2102
https://doi.org/10.5194/egusphere-egu22-2102
EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

The joint dependence of longwave feedback on surface temperature and relative humidity

Brett McKim1, Nadir Jeevanjee2, and Geoffrey Vallis1
Brett McKim et al.
  • 1University of Exeter, Mathematics, United Kingdom of Great Britain – England, Scotland, Wales (brettmckim@gmail.com)
  • 2Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey, United States

The longwave clear-sky feedback (the dependence of outgoing longwave radiation on surface temperature) is a major determinant of the climate's stability. Various studies have suggested that the feedback is largely independent of both surface temperature and relative humidity, which implies that the climate stability is also independent of surface temperature and relative humidity. However, this uniformity seems to contradict other work which shows that the subtropics are relatively stable and the deep tropics are relatively unstable, implying the feedback must vary between the two regions. We resolve this apparent contradiction by systematically computing the feedback as a function of both surface temperature and relative humidity. Above 275 K, the feedback depends significantly on relative humidity. We then show the feedback does indeed vary in the tropics and that this difference arises from regional differences in relative humidity. Finally, we estimate the effects of clouds on the feedback with a simple model and find that although clouds have a destabilizing influence, the significant dependence on relative humidity persists. Our work gives a renewed appreciation for how the feedback can vary significantly with both surface temperature and relative humidity.

How to cite: McKim, B., Jeevanjee, N., and Vallis, G.: The joint dependence of longwave feedback on surface temperature and relative humidity, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2102, https://doi.org/10.5194/egusphere-egu22-2102, 2022.

Comments on the display material

to access the discussion