Oral

IAMAS

JMC14 - Climate Change in the Polar Regions: Observing, Modelling and Predicting High Impact Transitions

Dependence of High Latitude Boundary Layer Properties on Environmental Conditions over the North Atlantic and Southern Ocean: Results from Recent Field Campaigns

A previous study showed that the dependence of boundary layer (BL) cloud properties on environmental conditions differs between the Southern Ocean (SO) and the North Atlantic (NA), even when the cold air outbreak intensity, lower tropospheric stability, and BL inversion strength were the same. The competing roles of how synoptic dynamics, cloud-scale dynamics, aerosols, precipitation, and radiative transfer processes affect the dependence of cloud properties on environmental conditions remain unclear. The Cloud And Precipitation Experiment at kennaook (CAPE-k) enhances existing observations at the kennaook/Cape Grim Baseline Air Pollution Station (KCGBAPS) by acquiring observations using the second Atmospheric Research Measurement (ARM) Mobile Facility (AMF2). It is providing cloud and precipitation observations using ground-based remote sensors, starting in mid-April 2024 and continuing through September 2025. These unique observations will help further examine the environmental factors that influence BL cloud properties over the SO. This study aims to characterize differences in how the macrophysical and microphysical properties of BL clouds vary with environmental conditions and geographic location by comparing CAPE-k data with data from the Cold-air Outbreaks in the Marine Boundary Layer Experiment (COMBLE) over the NA and from the Measurements of Aerosols Radiation and CloUds over the Southern ocean (MARCUS) campaign. To achieve this, analysis previously used to compute the cold air outbreak intensity index, lower tropospheric stability, BL inversion strength, convective available potential energy, sea surface temperature, wind speed and direction, coupling of clouds to BL, presence of open or closed cells, 700 hPa relative humidity, and whether precipitating are applied to the CAPE-k data to compute environmental conditions. BL cloud boundaries and occurrences, cloud top and base temperatures, cloud base phase partition, and vertical profiles of effective radius and liquid water content are computed from the remote sensing data to determine the cloud properties. Then, a statistical analysis is performed to determine how the cloud properties vary with environmental conditions for the three campaigns across seasonal cycles. This analysis will ultimately help better determine the controls of cloud properties using a more comprehensive multi-campaign dataset than has previously been used.