Observing cloud microphysics using (ultra) high resolution radar and lidar system

Cloud microphysical processes, such as droplet activation, condensational, and collisional growth, play a crucial role in the evolution of clouds and precipitation. Accurate representations of these processes in numerical models, which are essential to weather and climate models predictions, are challenging partially due to incomplete understanding of those processes at the process level arising from limited observations. Specifically, typical cloud radars have a resolution on the order of tens of meters. This resolution is insufficient to resolve critical microphysical processes that manifest at finer scales (meter and sub-meter). To mitigate this observational gap, we introduce three novel remote sensing systems with high range resolution capability: 1) The first system is a W-band (94GHz) radar with a range resolution down to 3 m, which is a factor of 10 finer than the typical cloud radar. The radar observations reveal detailed cloud structures that conventional sensors could only perceive in a bulk sense, providing new avenues to investigate cloud microphysical processes and their impact on climate system; 2) The second instrument is a lidar system with resolution down to decimeter scales. The observed distributions of the first-arriving photons from lidar reflect vertical development of a cloud, including droplet activation and condensational growth; 3) The third instrument is a THz (680 GHz) radar system operating with centimeter scale resolution. An novel experiment is conducted by applying the THz radar to measure the hydrometeors generated in a spray chamber, results show great consistency with the in-situ measurements. Notably, the high-resolution capability allows the THz radar to detect a single particle with a diameter around 50 micrometers, paving the foundation for using THz radar to observe cloud microphysics. The theoretical foundation of this particle detection concept is discussed followed by a validation from the Pi Cloud Chamber observation.