Tuesday, 11 January 2005: 2:30 PM
Saharan dust and optical properties of anvil-cirrus clouds
High concentrations of Saharan dust have been observed over the peninsula of Florida during CRYSTAL-FACE field campaign held during July2002. In another study, we analyzed the impact of the enhanced concentrations of cloud condensation and ice forming nuclei (CCN and IFN) on the characteristics of convective storms. This study examines the effects of Saharan dust intrusions on the microphysical structure and optical properties of anvil-cirrus clouds. For that purpose, we performed a series on Large Eddy Simulations (LES) based on the mesoscale sensitivity experiments. The effects of IFN and CCN enhancement on ice-particle size distributions as well as different moments were analyzed as the LES model domain followed the trajectory of the cirrus cloud. These numerical experiments were initialized using the microphysical and thermodynamic profiles provided by the fine grid of the mesoscale simulations for the time the cirrus-anvil cloud detached from the storm outflow. Wider size distributions and increased values of effective diameter, number concentration, and optical depth were obtained for numerical experiments that assumed polluted enviromments. Both IFN and CCN enhancements show important effects, however, results suggest a more important CCN effect.