Balloon-borne measurements and off-line analyses to improve constraints on ice nucleating particles in the cirrus regime. 

Measurements of ambient ice nucleating particle (INP) composition, concentration, and ice activation properties in the cirrus regime are extremely sparse. However, such measurements are fundamental to advancing understanding of cirrus extent and sensitivities to varied sources, as well as the impacts from perturbations of natural and/or anthropogenic origin. Here we present a potential approach to providing cirrus-relevant INP observations in both fast-response and systematic measurement scenarios. We will leverage experience with an existing upper-tropospheric sampling network relying on small weather balloons to enable collection of INP for off-line analysis. We will present an overview of our scheme, provide status of new instrumentation, and identify the significant technical challenges to be overcome. Finally, we will discuss how we plan to use these measurements to improve cirrus modeling, including better capturing the effects of anthropogenic aerosols on cirrus properties, distribution, and overall radiative effect.