Design and Characterization of a Cloud Chamber for Warm- and Cold-Cloud Microphysical Studies
Description
Cloud chambers provide controlled environments for investigating aerosol–cloud interactions and cloud microphysical processes under laboratory conditions. A cloud chamber was developed and characterized for controlled warm- and cold-cloud studies. The system consists of two interconnected chambers with nominal volumes of 2.7 and 9.0 m³; the 9.0 m³ chamber serves as the main experimental vessel for the cloud-formation experiments reported here. The facility integrates thermodynamic measurements with aerosol- and cloud-particle instrumentation and was evaluated through temperature-, pressure-, and humidity-control tests, multiple cloud-formation experiments, and analysis of the thermal response during depressurization. The measured temperature decreases were substantially smaller than the corresponding dry-adiabatic reference values, amounting to approximately 10–13 % of the theoretical dry-adiabatic cooling. A bulk energy-balance analysis yielded area-normalized apparent diabatic heating of approximately 25–27 W m⁻². Wall-temperature measurements further showed that the chamber boundaries were generally warmer than the three-level mean air temperature during much of each analysed depressurization period, while the three air-temperature levels revealed finite vertical thermal inhomogeneity. Four warm-cloud and two cold-cloud experiments produced broadly comparable droplet-size ranges and thermodynamic responses within each temperature regime under similar operating procedures. These results demonstrate the operational capability of chamber B to generate warm-cloud and cold-cloud conditions under the tested laboratory settings and highlight the importance of diabatic heat exchange in interpreting depressurization-driven cloud-chamber experiments.