Developing and deploying new sensors for in-situ monitoring of clouds

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Clouds interact with solar and terrestrial radiation, which contributes to competing heating and cooling effects on the climate system. Clouds generate precipitation, and so impact on the spatial distribution of water on the Earths surface. Clouds also facilitate complex chemical reactions and remove pollutants from the air. Datasets are required to capture the microphysical properties of clouds, namely the number, size and shape of the constituent particles, in order to correctly assess the impact and potential sensitivities of clouds on the Earth System. New networks are being established to monitor clouds. Whilst there are numerous options for instrumentation for measuring aerosol particles and much larger drizzle/precipitation particles, there is lack of suitable instrumentation for surface-based monitoring of liquid droplets which constitute the majority of clouds near the Earth's surface. PhD Project Methodology Cloud particles have been measured using a variety of techniques over the past 50 years, including bulk sampling of populations, and detailed single particle measurements. However, these existing instruments have generally been developed for operation from research aircraft travelling at high speed, with aspiration provided by the motion of the aircraft through the air. This makes many of these systems unsuitable for ground-based monitoring. Some ground-based fog monitoring systems have been developed, but there are issues over data quality and sampling artefacts resulting from aspiration. This project will develop and test new prototype sensors for surface-based cloud monitoring. Rapid prototyping will be conducted using 3-d printing and off-the-shelf optoelectronic components (diode lasers, laser drivers, optics, mounts) and Arduino-type microprocessors. The new sensors will be tested in the laboratory using certified glass calibration micro-spheres, Drop-on-Demand particle generators, and polydisperse particle suspensions using a nebuliser system. The sensors will be operated from the Holme Moss atmospheric observatory to monitor ambient clouds. Numerical simulations using Mie scattering code will be conducted to understand the response of the new sensors.PhD Project Description & Objectives This project will focus on the design, construction, and evaluation of new prototype sensors suitable for long term monitoring of the droplet size distribution in ambient clouds (diameter ~2-50). Objective 1: Financial and operational assessment of potential sensors. Assess various sensor configurations including bulk vs single particle, illumination wavelength(s), geometry, measurement principle e.g. scattering/diffraction, aspiration.Objective 2: Design and Construction of prototype sensor(s). Design and construct the optical, electrical, mechanical and data system for the prototype sensor. This includes construction of a numerical model to describe the theoretical operation of the sensor.Objective 3: Characterisation of prototype sensor(s). Use a variety of systems such as calibration microspheres, nano-litre Drop-on-Demand systems, intercomparison Mie scattering OPCs such as the DMT Cloud Droplet Probe available from the University of Manchester. Objective 4: Deployment of prototype sensor(s). Install and operate the prototype sensor(s) from the Holme Moss Hilltop Atmospheric Observatory, operated by the University of Manchester, to obtain data from ambient clouds in real-world conditions. Additional deployments may also be possible.Objective 5: Evaluation of sensor performance. Data analysis to establish if the real-world performance of the sensor fulfils design criteria. Are the measurement principles sound? Do data appear consistent with broader knowledge of cloud microphysical properties? Are ambient data consistent with calibrations and other datasets? Identify future improvements to the design.