Positive surface temperature feedback in the stable nocturnal boundary layer

The techniques of nonlinear analysis are used to examine the behavior of the stable nocturnal boundary layer (SNBL) when it is subjected to changes in incoming radiation or in surface characteristics. A single-column model and nonlinear bifurcation techniques are used to demonstrate that any atmospheric forcing, such as weak radiative forcing from greenhouse gases or cloud cover, can trigger a potentially significant positive feedback. Multiple solutions occur in some parameter spaces. This analysis shows that any forcing that decreases the stability, whether by increasing greenhouse gases or surface heat capacity, can cause large increases in surface temperature as the SNBL shifts from a weak turbulent regime, which allows the surface to cool, to a turbulent regime, which mixes warm air from aloft. Positive feedback may be a key factor in interpreting the long-term observed nocturnal warming trend in the SNBL.