Correcting radar Doppler spectra for atmospheric dynamics to study microphysics within mixed phase clouds

Within mixed-phase clouds the interaction of ice crystals with super-cooled liquid water leads to an enhanced growth of the ice particles. The growth of ice particles during the interaction is an important processes for precipitation formation in the mid-latitudes. Nowadays the interaction is still not clearly understood.

To understand the ice particle growth within such clouds the microphysical changes of a single particle population along its way through the cloud have to be analysed.

A way to study changes in ice particle micro-physic is to analyse radar Doppler spectra. Using the 3 beam configuration of the Atmospheric Transportable Radar (TARA) we retrieve the full 3-D Doppler velocity vector. This retrieved dynamical information is first used to retrieve the back trajectory of the measured particle population. Second it is used to remove the horizontal wind component from the spectrograms along the trajectories. So the relationship between of the particle population and its change in vertical motions can be identified.

Therefore, the corrected spectrograms offer a new perspective for cloud microphysical studies. Microphysical changes along the path of a population of particles through a cloud are represented in the retrieved spectrograms. With the wind correction information about vertical velocity changes of the tacked particle volume can be given and related to particle growth. The instrumental synergy during the ACCEPT campaign (Analysis of the Composition of Clouds with Extended Polarization Techniques campaign), fall 2014, Cabauw the Netherlands, make it also possible to retrieve liquid water layers within mixed-phase clouds. Therefore, identified changes within the retrieved spectrograms can be linked to the presence of super-cooled liquid layers.

So ice particle growth processes within mixed-phase clouds can be studied from a new perspective.