Improved Method for Simulating Clouds in an Atmospheric Column
Clouds are among the most important and uncertain aspects of the climate system. As climate changes, clouds respond in many ways (e.g., changes in altitude, phase (liquid or frozen water), and persistence). Each of these changes has a major influence on the planet’s radiative balance and on temperature and conditions at Earth’s surface. Therefore, it is critical to improve climate model simulations of clouds and their effects on climate by studying local cloud behavior without utilizing costly full Global Climate Model (GCM) runs. A newer and more promising approach is to work with pressure gradients (related to the changes in winds). This approach is called the weak-pressure-gradient (WPG) approximation and has been greatly improved by researchers at Lawrence Berkeley National Laboratory (LBNL). WPG is more successful, because it more smoothly connects the dynamics of convection and the large-scale environment. In a new study, LBNL researchers show that the standard WPG approach suffers from a long-wave resonance effect that is undesirable for single-column modeling, and they present a new WPG scheme that does not have this resonance. This study should greatly improve the utility of Single Column Models for the cloud and climate communities.
Edman, J. P., and D. M. Romps. 2014. “An Improved Weak-Pressure-Gradient Scheme for Single-Column Modeling,” Journal of the Atmospheric Sciences 71, 2415-29. DOI: 10.1175/JAS-D-13-0327.1.