MRI: Development of Enhanced T-Probe for Aircraft Measurement of Mixed Phase Ice-Water Cloud

Affiliation(s)PIProject periodFunded by
DAS Hallett, John 09/01/2007 - 08/31/2011 National Science Foundation

Project Description

PROJECT SUMMARY This Major Research Instrumentation development proposal seeks to significantly extend the operating characteristics of a recently developed instrument, the T probe-an instrument to measure water and ice content of clouds. In the current configuration, three collocated but separate sensors measure water, ice and water combined (the difference giving the ice content), together with reference air speed and density. The proposed improvement is based on higher power availability, leading to more than doubling the present measurement capacity of ice/water content to beyond 2g/m3. Most important, this improvement also will indicate shedding of excess water or ice beyond saturation conditions. A video microscope will be employed to visually confirm the fate of collected particles. Following completion of development and initial testing, the modified T probe will need to be field tested; separate funding will be sought. This project will be a collaboration of discipline scientists, engineers, and the private sector. The mix of ice particles and water drops occurs on different scales. One scale is when ice crystals are mixed irregularly throughout the volume of supercooled drops fallen from above or nucleated in situ. Alternatively, regions of ice crystals and supercooled drops may be brought into close proximity by different processes leading to mixed-phase of varying composition. Intellectual merit: Mixed-phase cloud and precipitation-as water and ice in the atmosphere and their transformation-lead to ice-phase precipitation, electric-charge separation, enhanced chemical reactivity, and an environment conducive to aircraft structure and engine icing. The interface between all water and all ice in the atmosphere may transition continually in the horizontal from all ice to all water with a mixed phase of differing composition between. Consequences of the mix of ice/water ratio include sensible and latent heat and moisture transport, radiative transfer and spatial distribution of precipitation. Measurement of cloud properties is possible by remote sensing from satellites, providing information on 10 km scales. High resolution measurements using the T probe are critical to verify cloud composition. Improved resolution to less than 10 meters can be achieved by the proposed modifications. The improvement in T probe measurement capability is critical for enhanced understanding of cloud processes. At concentrations more than 2g/m3, instrument saturation occurs leading to shedding of the excess-itself indicative of enhanced rate processes. An airborne instrument having such improved characteristics will provide diagnostics of where and why in any cloud system physical and chemical processes are likely to occur, leading to much improved insight in interpreting remote signals such as lidar and radar backscatter as well as modeling of chemical processes. The proposed instrument improvements will further understanding of the importance of mixed-phase cloud in aircraft icing and cloud electrification, heretofore beyond measurement capability. Broader impacts: Development and use of this instrument is ideally suited for graduate student training in an instrument class at both advanced undergraduate and graduate levels. Advances made under this proposed project will be employed in a University of Nevada, Reno course regularly taught by the PI (ATMS 748) to 10-15 students per semester. T probe development, as a new instrument, and the complete process of developing the rationale for applications in cloud microphysics as well as many aspects of atmospheric science including influence of clouds on climate through radiation and precipitation processes will provide opportunities for students to follow an idea through construction, testing, aircraft deployment, and new exploration. The development process will include modifications necessary as flight and laboratory results indicate design changes for improving the practical and scientific outcome of measurements and the value of measurements on a broader scale. As an example, results may guide wind tunnel design for simulation of both cloud processes as well as testing of aircraft for icing. Improved understanding of aircraft icing will contribute to increased aviation safety.