Combining model-based quasi-Lagrange tracking of air mass intrusions into the Arctic with airborne observations

Large-scale air mass exchanges between lower latitudes and the inner Arctic are one key aspect in understanding Arctic climate change. Of particular interest are Warm and Moist Air Intrusions (WMAI). These events, albeit covering only 10 % of the time, drive >60 % of the overall moisture flux into the Arctic. Conveyed by surging downward longwave radiation, WMAI can trigger pronounced sea-ice melt and alter local atmospheric conditions for weeks.

However, many models struggle with a correct representation of air mass transformations during these events. Thus, a Lagrangian approach is suggested to perform airborne measurement campaigns and to analyze numerical weather forecast and reanalysis data. Here, we present a combination of the Lagrangian analysis tool Lagranto with ECMWF forecast datasets and the atmospheric flight planning tool MSS. This approach was applied during the September 2020 MOSAiC airborne campaign. Additionally, five-day forward and backward trajectories were calculated to identify air masses linking the airborne observations with ground-based observations at the MOSAiC camp. A first analysis of the air mass characteristics and their change along the trajectories is presented.

Due to vertical wind shear, such an air mass analysis is not trivial. It requires a detailed flight planning in order to sample the temporal and spatial (horizontal and vertical) development of the air masses. As an outlook for the upcoming spring 2022 HALO-(AC)³ campaign, the potential of combining Lagranto with MSS in predicting the most effective flight track is therefore demonstrated.