Aerosol Influences on Ice Formation in Arctic Cold Air Outbreak Clouds during Cold-Air outbreak Experiment in the Sub-Arctic Region (CAESAR)

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Arctic climate is changing at a faster pace than anywhere on Earth. Climate projections indicate that the Arctic will continue to warm, but uncertainties arise due to questions about the future behavior of Arctic clouds. An area of primary uncertainty is the properties of clouds that form during cold-air outbreaks, where very cold airmasses over the Arctic ice move southward over the relatively warm open ocean. This award will help to provide observational data of these clouds (and precipitation) and the exchange of energy between the ocean and atmosphere during the Cold-Air outbreak Experiment in the Sub-Arctic Region (CAESAR), which will be conducted in Spring 2024 out of northern Scandinavia. The observations collected during CAESAR will be used in an effort to better understand the characteristics of the cold-air outbreak system, and the Arctic climate system more broadly, in order to inform climate models and projections. The project will also help to improve forecasting of weather hazards with significant relevance to naval operations, commercial shipping, and coastal communities. The broader field effort includes significant opportunities for students and early-career scientists, international collaboration, and public outreach. A key addition from this project is in the inclusion of early-career researchers in the role of flight scientist, providing them with an valuable training opportunity. This award will seek to constrain primary ice nucleating particle (INP) sources and concentrations associated with cold air outbreak (CAO) cloud systems, thereby supporting the understanding of the evolution of microphysical processes and their description in collaborative cloud modeling simulations. Data will be used to answer questions about the source of the INP, the primary nucleation mode, and how glaciation occurs. Real-time INP measurements will be made using the Colorado St. Univ. (CSU) Continuous Flow Diffusion Chamber (CFDC) augmented with an MSP-4240 aerosol concentrator. In addition, filter samples will be collected for offline measurements of immersion freezing INP concentrations with the CSU ice spectrometer. Primary funding for this project comes from the Physical and Dynamic Meteorology program with partial funding from the Arctic Natural Sciences program. The deployment of observational assets for CAESAR is being funded by the Facilities for Atmospheric Research and Education program.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.