Climatology of clouds containing supercooled liquid in the Western and
Central Arctic
Abstract
Long-term measurements at the U.S. Department of Energy (DOE)
Atmospheric Radiation Measurement (ARM) at the North Slope Alaska (NSA)
site in Utqiagvik, Alaska and from the Multidisciplinary drifting
Observatory for the study of the Arctic Climate (MOSAiC) expedition are
being used to study the climatology of clouds containing supercooled
liquid (SCL) in the Western and Central Arctic. Classification of cloud
hydrometeors in the liquid, ice or mixed phase of the cloud is
determined by using the Cloudnet algorithm developed by the Finish
Meteorological Institute. We apply the Cloudnet processing chain to a
set of ground-based remote sensing measurements from the NSA site and
the ARM mobile facility and the TROPOS shipborne atmosphere observation
suite (OCEANET) on board of the RV Polarstern research vessel during
MOSAiC. In order to accurately detect cloud droplets and SCL layers
within mixed-phase clouds, Cloudnet relies on lidar observations. Lidars
however suffer from total signal attenuation at a penetration optical
depth of about three. Conversely cloud radars with their capability to
penetrate multiple liquid layers can be used to expand the
identification of cloud phase to the entire vertical column beyond the
lidar signal attenuation height by using information of the cloud radar
Doppler spectrum. The Leipzig Institute for Meteorology (LIM) recently
developed a deep learning approach for reVealing supercOOled liquiD
beyOnd lidar attenuatiOn (VOODOO) which benefits from the morphological
features in cloud radar Doppler spectra to extract further information
related to the existence of SCL using Cloudnet’s target classification
as supervisor. The current contribution presents a SCL climatology
obtained using Cloudnet for the NSA site along with case-studies for
MOSAiC where VOODOO results are contrasted with the standard Cloudnet
outputs. Advantages and limitations of both methods will be presented to
the scientific community.