Stabilization of the Atmospheric Boundary Layer and the Muted Global Hydrological Cycle Response to Global Warming

Abstract

Both the global precipitation and evaporation in global warming simulations increase at 1%?3% K?1, much smaller than the rate suggested from the Clausius?Clapeyron (C?C) relation (6%?6.5% K?1). However, the reduction of surface sensible heat flux over the global ocean (5.2% K?1) matches the difference between the fractional increase of evaporation and the C?C relation, implying that the fractional decrease of the Bowen ratio over the global ocean follows the C?C relation closely. The analysis suggests that the stabilization of the atmospheric boundary layer (ABL) in response to global warming is the main factor responsible for the simultaneous reduction of the surface sensible flux and the muted increase in the surface latent heat. Because the stabilization of the ABL causes the same amount of fractional change in both the sensible and latent heat fluxes, the fractional decrease of the Bowen ratio closely follows the C?C relation. The ABL stabilization mechanism for the muted increase in the global hydrological cycle in response to global warming is physically consistent with two other proposed mechanisms, namely, the atmospheric energy constraint and the reduction of convective mass flux.