New Insights into the Vertical Structure of Clouds in Polar Lows, using Radar‐Lidar Satellite Observations

Abstract : For the first time, we characterize the vertical distribution of cloud microphysical properties in polar lows (PLs). We base our investigation on colocations found between A-Train satellites overpasses and 82 PL occurrences evidenced from AVHRR observations in the Nordic Seas. We use the raDAR/liDAR DARDAR satellite cloud products to retrieve the thermodynamic phase and ice microphysical properties of clouds (ice water content [IWC] and ice crystal effective radius [r eff ]). Two thirds of the investigated PLs show cloud tops higher than commonly documented (5 km), and up to 9 km. PLs are largely dominated by the ice phase, with more supercooled liquid occurrences in the eye. We also show that spiraliform clouds have larger average IWC in the few kilometers below cloud top, by up to a factor of 2, compared to comma-shaped PLs. Plain Language Summary Polar lows are intense maritime cyclones posing serious threats to mariners and coastal populations. Due to their limited size and sudden development, operational forecast struggles to correctly predict them. Additionally, the limited amount of observational constraints renders improvements of simulations difficult. We provide the first statistical analyses of cloud microphysical properties of these storms using radar and lidar satellite observations. We demonstrate much higher cloud tops than usually assumed. We highlight the cloud phase, describe the vertical distribution of ice mass and crystal size, and stress some differences between spiraliform and comma-shaped cyclones. These new constraints can be readily used to improve polar lows' simulations.