Measuring the elusive particles that form ice in clouds

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Summary and aimThe formation of ice in clouds is one of the least well understood aspects of the planet's climate system. Special aerosol particles, known as ice-nucleating particles, are needed to trigger ice formation but their sources, characteristics and distribution around the globe are very poorly defined. Once ice crystals form, there can be a cascade of processes leading to changes in precipitation, cirrus cloud coverage and cloud reflectivity. All of these changes are important for climate change. A major limitation in this field is the lack of instrumentation which can be used to measure INP concentrations on a semi-autonomous basis. In this project you will play a direct role in breaking this deadlock and revolutionising the field.As part of a collaboration between Leeds, Karlsruhe Institute of Technology (KIT) and Bilfinger Noell GmbH, a new concept instrument for quantifying atmospheric ice nucleating particles has been developed. This new instrument, the Portable expansion chamber for Ice Nucleating particles mEasurement (PINE), has been developed to work at conditions relevant for mixed-phase cloud conditions and is in the process of commercialization. The aim of this PhD project is expand the use of the PINE chamber to temperatures and conditions relevant for cirrus clouds. This will involve taking a working instrument and adapting it for use at lower temperatures.The project will involve working closely with the CASE partner (Bilfinger Noell GmbH) as well as Karlsruhe Institute of Technology. It will largely be a lab based project involving extended visits to Germany. Hence, it offers a fantastic opportunity to work in both academic and industrial settings in different countries. The experience gained will place you in an enviable position for future employment in either the industrial or academic sectors.ObjectivesThe project will involve:i) Adapting the PINE chamber to operate at cirrus relevant temperatures below water saturation. This will involve first learning how to use the instrument in its current configuration in Leeds before adapting it to work at lower temperatures and cirrus conditions. You will work closely with Dr Boffo at Bilfinger Noel to adapt the chamber for use at low temperatures. You will then work at Karlsruhe institute of technology where you will use the well-established AIDA cloud simulation chamber to calibrate the production of ice crystals in the PINE chamber below water saturation. ii) Studying the effects of aging of dust aerosol under conditions relevant for cirrus in a set of laboratory experiments. This will be conducted in Leeds where aerosol will be generated in a chamber, processed in a controlled way to mimic atmospheric aging, and then sampled into the PINE chamber. iii) Conducting some of the first long-term measurements of INP under cirrus conditions in the atmosphere. We are just starting to produce the first long-term (months long) datasets for INP concentrations relevant for mixed-phase clouds. You will make what might be the first ever long term measurements under cirrus conditions. For this, you will make use of the new Leeds Atmospheric Observatory, which is located in the countryside east of Leeds.