Mechanisms for indirect effects from aerosol pollution on glaciated clouds

Poster PDF

Description

Our “aerosol-cloud model” with hybrid bin/2-moment bulk microphysics that treats ice morphology and the dependency of shape parameters on cloud-particle size was developed during this Atmospheric System Research project. A very recent upgrade, published in 2013, to our ice-nucleation scheme has been included in the model.

Earlier in the project, the model was validated for mesoscale simualations of deep convective systems in two field campaigns, Cloud Land Surface Interaction Campaign (CLASIC) and Tropical Warm Pool-International Cloud Experiment (TWP-ICE). The validation included cloud-particle number concentrations, after initialising it with aerosol conditions of loading.

Results from sensitivity tests are shown in the presentation, revealing the separate contributions to the aerosol indirect effect via cold clouds, due to their changes in lifetime and in radiative/microphysics properties. The cold-cloud indirect effect is much smaller than the warm-cloud indirect effect.

The impact on cold clouds from soluble aerosols in pollution boosting homogeneous freezing aloft and altering cirriform clouds' extent is documented for the simulations.