MRI: Development of a Water Vapor and Temperature Mapping System to Study Cloud-turbulence Interactions in the Michigan Technological University (MTU) Pi-Chamber

Michigan Technological University, Houghton MI

Investigators

Abstract

Aerosols and clouds are among the most important factors regulating our planet's radiative balance and climate, while interacting in complex manners. Aerosols act as cloud nuclei, determining the formation and lifecycle of clouds; conversely, clouds transform and remove aerosols from the atmosphere. Turbulence plays a key role in these processes by influencing cloud droplet size distribution, aerosol nucleation, hydration and activation, and spatial segregation. For example, mixing by entrainment of dry air into saturated air at the edges of a cloud is an important and still not fully understood process that requires further laboratory and field studies. Understanding and modeling the complex interactions between aerosols and clouds is challenging due to turbulence-induced water vapor and temperature fluctuations at small spatial (<100mm) and temporal (<10s) scales. Novel analytical tools need to be developed to link these fine-structure processes to climate-relevant cloud properties. The research enabled by the new instrument will help understanding the intricacies of the interactions between aerosol, clouds and turbulence, and will thus have clear and critical broader impacts, beyond simple scientific curiosity. The project will also promote graduate and undergraduate students' career development through hands-on research and mentoring activities and contribute to growing the new generation of instrumentalists. To help filling gender and minorities gaps in STEM, the project will work with the office of institutional equity and inclusion at Michigan Technological University (MTU) and through the Michigan College/University Partnership Program to increase the outreach to students from under-represented groups. The scientific objective of this development project is to design, construct and test a new instrument for the study of the effects of turbulence on clouds and aerosols in the Michigan Technological University's turbulent multiphase cloud chamber. This instrument would significantly enhance the capability of the chamber and enable new exciting research. The chamber - a community shared facility - can generate controlled environmental and convective turbulent conditions, and form clouds (warm, cold or mixed) through different modes (e.g., by expansion or by mixing through a vertical temperature gradient). In the mixing mode, clouds can be maintained for several hours/days and therefore microphysical properties and aerosol-cloud-turbulence interactions can be studied in detail with no time constraints. To understand how turbulence shapes temperature, water vapor and liquid water fields, one needs to map their spatial and temporal distributions. To achieve this goal, the project will develop an analytical tool for imaging temperature and water (vapor and liquid) distributions inside the chamber without affecting the turbulent conditions, while providing spatial and temporal resolutions relevant to the processes of interest (~1-20 cm and ~1 s). The remote imaging system is based on Raman scattering that carries information on water concentrations and temperature. The instrument will become integral part of the cloud chamber shared facility enhancing it scientific and analytical capacity and expanding national and international collaborations. Research enabled by the new instrument will include: a) Study of the effect of homogeneous vs. inhomogeneous mixing on cloud droplet growth and size distribution, the relevant length scales and how turbulence influence the saturation ratio field. b) Small-scale details of the saturation ratio field, how it determines initial activation, cloud droplet growth and size distribution evolution, and how the droplet evolution caused by the saturation ratio fluctuations feedback into the cloud turbulence. c) Effect of centimeter-scale intermittencies on aerosol spatial segregation, humidification, activation and droplet formation.