States of Maximum Entropy Production In One-dimensional Vertical Climate Models
Abstract
Although the maximum entropy principle (MEP) has been examined by several au- thors in a variety of climate models, only Ozawa and Ohmura (1997) have explicitly analysed the MEP in a one-dimensional (1-D) radiative-convective model (RCM). Here we extend Ozawa and Ohmura's analyses by using two different 1-D RCMs. The first model parameterises the convective fluxes following the mixing length the- ory, from which the eddy thermal diffusion coefficient is chosen to produce the max- imum entropy generation. The value for the eddy thermal diffusion coefficient for a fixed vertical profile of specific humidity (as in Ozawa and Ohmura, 1997) agrees well with that expected for air in stirred conditions. However, the MEP fails when the vertical profile of relative humidity is fixed (i.e., when the water vapor - temperature feedback is included). The second model is much more realistic since we assume that convective processes sustain a critical lapse rate in the troposphere. Thus, the atmo- sphere is divided into a lower convective region with a prescribed lapse rate and an upper radiative-equilibrium region. The surface boundary layer velocity predicted by the MEP appears reasonable. However the discontinuity of temperatures at the surface is too large (10 K). In addition, the convective flux reaches a maximum value for an optical thickness similar to current conditions. This additional result may support the maximum convection hypothesis suggested by Paltridge (1978).
- Publication:
-
EGS General Assembly Conference Abstracts
- Pub Date:
- 2002
- Bibcode:
- 2002EGSGA..27....5P