An interactive pmc parameterization in a two-dimensional chemical/dynamical model
Abstract
We have developed a parameterization for mesospheric clouds that can be used in our two-dimensional chemical/dynamical model (CHEM2D). CHEM2D is a global model with fully coupled chemistry, dynamics and radiation. Our parameterization uses the CHEM2D-calculated temperature and H2O fields to quantify the saturation conditions in the high latitude summer mesopause region. For saturation ratios, S, greater than 10, we convert a specified fraction of the water vapor to ice particles of a given radius. For S < 1, all the ice is assumed to sublimate back to water vapor. For S values between 1 and 10, neither condensation nor sublimation is assumed to occur. Instead we assume that any existing ice is passively transported by the mean meridianal circulation, diffused by breaking gravity waves, or sedimented at the fall-speed appropriate for the assumed particle size. The resulting perturbed H2O shows regions of dehydration and enhancement which are similar to those obtained from more detailed microphysical models. With our approach, we can simulate the life cycle of mesospheric clouds and their perturbations on the mesospheric H2O, ozone and temperature and also on atomic hydrogen in the lower thermosphere. These results will be presented and their dependence upon free parameters such as particle size and the parameterized ice formation rate will be discussed.
- Publication:
-
35th COSPAR Scientific Assembly
- Pub Date:
- 2004
- Bibcode:
- 2004cosp...35.1878S