Measuring meso-scale gradients in the Arctic during HALO-(AC)³

Boundary layer cloud transitions at high latitudes play a key role in Arctic climate change, and are partially controlled by large-scale dynamics such as subsidence. While measuring large- and mesoscale divergence has proven notoriously difficult, the recent NARVAL and EUREC4A airborne campaigns in the subtropics have finally achieved this goal using multiple dropsondes releases in circular patterns. If this method also works at high latitudes is still an open research question, given the considerable differences in atmospheric dynamics. Answering this question was one of the main objectives of the recent HALO-(AC)^3 field campaign near Svalbard in Spring 2022. Circular dropsonde patterns were realized during various research flights by two airplanes, independently sampling Cold Air Outbreaks (CAO) in the Fram Strait with multiple dropsondes. This study presents a first overview of the results. We find that the method indeed yields reliable estimates of mesoscale gradients in the Arctic, yeilding robust vertical profiles of both subsidence and vorticity. Sensitivity to aspects of the method is investigated, including dependence on sampling area and the divergence calculation. Ongoing work to drive targeted Lagrangian high resolution simulations of the observed CAOs exclusively with HALO-(AC)³ data will be briefly discussed.