Publication Date:
2017-05-29
Description:
Earth surface temperature changes induced by added thin cirrus or contrails are investigated with a radiative-convective-diffusive model, basically without climate system changes, with relaxation of the temperature profile by radiation and mixing. The conceptual study shows that the surface temperature sensitivity to cirrus depends strongly on the ratio of the time scales of energy transport by mixing and radiation, where mixing may include turbulent diffusion, convection and transports by the large-scale circulation. The time scales are derived for steady layered heating (ghost-forcing) and for a transient cirrus case. The time scales are shortest at the surface and shorter in the troposphere than in the mid-stratosphere. Heat induced by cirrus in the upper troposphere reaches the surface only for strong vertical mixing. The local surface-temperature sensitivity to adjusted radiative forcing (RF) is larger for the shortwave (SW) than the longwave (LW) cirrus forcing. For weak mixing, cirrus may cool the surface even if the cirrus causes a positive instantaneous or stratosphere-adjusted radiative forcing (RF) at the tropopause. The shorter time scales near the surface indicate a potential for dominant SW surface cooling regionally where cirrus or contrails form, while weak LW warming may dominate at larger distances.
Electronic ISSN:
1680-7375
Topics:
Geosciences
