4.3
The use of radar and lidar to study the microphysical processes in water clouds
Herman Russchenberg, Delft Univ. of Technology, Delft, Netherlands; and O. Krasnov, A. Khain, and M. Pinsky
Over the last decade much effort has been put into the development of the retrieval techniques that combine radar, lidar and microwave radiometry to obtain cloud parameters. This has resulted in a range of techniques, often with a different range of applicability. Methods have been developed for adiabatic as well as non-adiabatic water clouds, for clouds that produce drizzle and for the drizzle falling out of the clouds. These techniques are very useful, and when they are combined, they can give a quite complete picture of the cloud's micro-physical properties. Now that these techniques are reaching a sufficient degree of maturity the time has come to see how they can be used to understand cloud microphysical processes: how are droplets formed, and how is drizzle? What is the link with cloud dynamics? A combined approach of cloud modeling and remote sensing can do this. The key to such an approach is the link between remote sensing observables and cloud microphysics, like for instance the Z-LWC relationship between the radar reflectivity and cloud liquid water content, or lidar extinction and cloud droplet radii, and combinations thereof. Analyses of in situ observations of cloud dropsize distribution, and derived from those: expected radar and lidar observables, shows that the relationships between observables and microphysics are ambiguous. And also, that only a combination of radar, lidar and/or microwave radiometry will be of use here. The question arises: how is the complex relationship between observables and microphysics linked to cloud processes, like drop formation and growth. The answer lies in using cloud microphysical models. We have used the advanced Khain/Pinksy to simulate the radar/lidar observables in different stages of cloud development and related to the observed values. This approach revealed that it is possible to use combined radar/lidar observations to trace the cloud evolution process. We will present the combined model/observation approach and how it can be used to identify different stages in cloud formation, ranging from the early stage of droplet growth until drizzle formation. We will illustrate the concept with data obtained at CESAR Observatory in The Netherlands.
Session 4, Radar-Lidar observations and applications
Wednesday, 23 January 2008, 8:30 AM-10:00 AM, 210
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