The invitation to Chandrasekaran Venkatachalam to visit the Leipzig Institute for Meteorology was based on the idea of getting to know each other, exchanging knowledge and ideas, and initiating a cooperation within SPP-PROM.

Chandrasekaran Venkatachalam (Chandra) is a pioneer and renowned scientist in the field of radar polarimetry. He has made significant contributions to the development and application of radar polarimetric techniques. His work focuses on analysing the polarisation properties of radar waves to obtain information about surface structures, atmospheric phenomena and other geophysical properties.

During Chandra’s stay in Leipzig, we showed him our institute (LIM), instruments and laboratories. He also visited the Leibniz Institute for Tropospheric Research (TROPOS) where he was given a tour of the institute and its laboratories and met some of the scientists there (see Fig. 1). At LIM, Chandra gave a very inspiring seminar talk entitled “From raindrops to floods” (see Fig. 2). This talk was hybrid and several SPP-PROM members participated online.

A potential collaboration is envisioned to develop in the context of the extensive measurements of the Atmospheric Radiation Measurement (ARM) Surface Atmosphere Integrated Field Laboratory (SAIL) campaign, which focuses on how the Upper Colorado River watershed interacts with the atmosphere (Feldman et al. 2021). During the SAIL-CORSIPP campaign, in the winter 2022-2023 in the Colorado Rocky Mountains, Chandra’s X-band radar, our W-band radar, and our in-situ video snowfall sensor measured simultaneously (see Fig. 3). We discussed special measurement days, e.g. snowfall events with the occurrence of conical graupel and ideas for further evaluation. Anton Kötsche and Chandrasekaran Venkatachala agreed on a closer cooperation for the dual-wavelength observations, with a potential visit of Anton to Colorado State University in 2024 for a joint analysis of the dual-wavelength radar signals during the SAIL-CORSIPP campaign. Veronika Ettrichrätz is now testing a snowflake particle shape classification based on Chandrasekaran Venkatachalam's FFT algorithm (Chandrasekar, V., et al. 1989).

Overall, we learned a lot from Chandrasekaran Venkatachalam's knowledge and advice and look forward to further possible collaborations.