Microphysical properties of precipitating hydrometeors, such as size, concentration, or shape, can be retrieved by vertically-resolved remote-sensing measurements. For a thorough quality assessment, a direct evaluation of those retrievals is required. Surface in-situ observations of precipitation particles are one possible approach. In the framework of the Master’s thesis presented in here, the two-dimensional video disdrometer (2DVD), a ground-based precipitation sensor was applied for this purpose. The 2DVD provides horizontal line scans of two orthogonally aligned cameras so that hydrometeors in a well-defined measurement area are detected. This allows the derivation of single-particle properties as well as precipitation rates, particle number concentrations, or particle size distributions. In this thesis defense, the 2DVD including its measurement and calibration principle, the data processing chain, as well as former 2DVD-related research is presented. Further, the successful instrument evaluation of the 2DVD against other precipitation in-situ sensors and its capabilities to distinguish different ice crystal shapes will be elaborated on. Additionally, case studies about combined 2DVD and remote-sensing observations of cloud seeding experiments will be shown to demonstrate that the 2DVD can contribute to the investigation of clouds and precipitation processes. Data used in this thesis were collected during the PolarCAP / CLOUDLAB campaign near Eriswil, Switzerland between 12/2022 and 02/2023.:1 Introduction 2 Measurement campaign and operating instruments 2.1 Cloudlab and PolarCAP 2.2 Instrument overview 2.3 Two-dimensional video disdrometer (2DVD) 2.3.1 Measurement principle and data processing 2.3.2 Calibration procedure 2.3.3 Former 2DVD research 2.4 HOLIMO 3 2DVD – deducible hydrometeor and precipitation properties 3.1 Properties of single particles 3.2 Precipitation properties 3.2.1 Precipitation rate 3.2.2 Particle size distribution 3.2.3 Relations of particle properties 3.2.4 Particle number concentration 4 Measurement results 4.1 2DVD calibration and evaluation 4.1.1 Calibration procedure on 12 December 2022 4.1.2 Comparison of precipitation rates of different instruments 4.2 Detection of different ice crystal shapes 4.2.1 17 January 2023, 11:30 – 11:35 UTC: irregular crystals and aggregates 4.2.2 17 January 2023, 13:50 – 13:54 UTC: dendrites, strongly rimed particles, irregular crystals 4.2.3 17 January 2023, 14:07 – 14:11 UTC: dendrites 4.2.4 18 January 2023, 09:44 – 09:48 UTC: needles / columns 4.3 Case studies: Precipitation monitoring during cloud seeding experiments 5 Discussion 6 Summary, Conclusions, and Outlook Appendix A 2DVD data processing chain Appendix B Calibration offset between Mira-35 and RPG94 LACROS Appendix C Unrealistic particles not filtered by the 2DVD sno-algorithm Bibliography

From the Proceedings of the 1972 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - May 5-6, 1972, Prescott, Arizona / There have been many efforts in recent years to modify thunderstorms through cloud seeding. Collective cloud seeding efforts in Arizona before 1971 are reviewed and an operational convective cloud seeding program carried out in Arizona in the summer of 1971 is analyzed. The comprehensive Santa Catalina cloud seeding experiment (1957 to 1964) was a randomized seeding using silver iodide. Results of this experiment are uncertain as numerous interpretations are possible. Numerous individual experiments from 1966 to 1970 at flagstaff were conducted, with uncertain results. An intensive program of seeding individual cumulus clouds with silver iodide was carried out in the summer of 1971 in central and eastern Arizona. No statistically significant changes were noted. Results of the Catalina experiment imply that seeding decreased rainfall on and downwind from the target. Two other experiments were inconclusive. Nine figures show precipitation patterns.