Disentangling Cloud Microphysical Properties from Lidar Backscatter and Depolarization Measurements in Winter Storms During the IMPACTS Field Campaign

Airborne measurements of the backscatter coefficient (𝛽) and depolarization ratio (𝛿) from airborne lidar are instrumental in providing information on the cloud phase, and to some degree ice particle habit, through the vertical column of clouds. Observations of in-situ cloud microphysical properties such as the distribution of particle sizes, presence of supercooled liquid water, and ice water content are key in relating lidar measurements to microphysical processes and validating retrievals of cloud properties.

The NASA-sponsored Investigation of Microphysics and Precipitation for Atlantic Coast-Threatening Snowstorms (IMPACTS) field campaign provided high spatiotemporal measurements of remote sensing and cloud microphysical properties using a “satellite-simulating” ER-2 aircraft flying above winter snowstorms and a “storm-penetrating” P-3 aircraft sampling within clouds during the 2020, 2022, and 2023 winters. Vertical profiles of 𝛽 and 𝛿 from the Cloud Physics Lidar provided scattering properties at various temperatures while coordination between the aircraft allowed for these measurements to be compared with data collected by in-situ instruments at different altitudes within the cloud.

Among the 23 coordinated flights, two snowstorms with different 𝛽, 𝛿, and temperature range both in the vertical and along the P-3 flight track are contrasted. An Alberta clipper system over Québec, Canada on 19 January 2022 exhibited low median 𝛽 (= 0.01 km^-1 sr^-1), high median 𝛿 (= 0.3), and cold cloud tops (-60℃) associated with more columnar crystals and bullet rosettes between -30° and -15℃. A redeveloping Mid-Atlantic cyclone on 28 February 2023 featured a higher median 𝛽 of 0.11 km^-1 sr^-1 and lower median 𝛿 of 0.1 with warmer cloud tops (-30℃) and a greater presence of supercooled liquid drops between -15° and -5℃. These cases are further placed into the broader context of snowstorms sampled during IMPACTS, and implications for developing a new cloud phase and particle habit algorithm using CPL data are discussed.