Cloud processes including water phase transitions need to be parameterized in global NWP models. Martinez-Alvarado and Plant (2013) investigated the importance of the large-scale precipitation parameterization (cloud microphysics parameterization) and the convection parameterization for the evolution of a WCB. They highlighted a sensitivity of the large-scale dynamics to both, the type of parameterization scheme but also the interaction of the large-scale and convection parameterization. Joos and Wernli (2012) illustrated that different microphysical processes along the WCB ascent contribute to latent heat release and PV-changes within a cyclone. A large uncertainty exists in the model representation of mixed-phase clouds; comparison of heating rates along WCB (Joos and Forbes, in preparation).
Martinez-Alvarado et al. (2014) showed that diabatic processes can determine the WCB outflow height and in turn impact the Rossby wave evolution. They demonstrate that differences in the Rossby wave structure can be attributed to differences in the parameterization schemes affecting WCBs. Interactions between cloud microphysics and small-scale dynamics such as gravity wave motions and embedded convection may also have an influence on WCB evolution. High resolution trajectories have shown that a significant fraction of air parcels in the WCB experience periods of rapid ascent, either in cold frontal line convection or mid-level embedded cells (Rasp 2015).
|Mixed phase clouds|
|Planned Observations||HALO (dropsondes, radar, in-situ, radiometer)|
|Schematic flight plan:|