How do synoptic conditions affect Liquid Water Path over the sea-ice-free Arctic Ocean during ACLOUD?

Despite the strong influence of cloud liquid water on the radiative budget, the knowledge of its amount and variability in the Arctic is rather limited. The Arctic CLoud Observations Using airborne measurements during polar Day (ACLOUD) campaign took place from May 22 to June 28, 2017 and offers the possibility to investigate the Liquid Water Path (LWP) during various environmental conditions. In this period synoptic conditions were characterized as a cold air outbreak, warm air advection resulting in a period of warm conditions, and a normal period with conditions in between the cold and warm period. Deployed on the research aircraft Polar 5, the Microwave Radar/radiometer for Arctic Clouds (MiRAC) collected downward observations of radar reflectivity and Brightness Temperatures (T_b) over sea-ice-free ocean from aircraft altitudes above 2.8 km. From T_b a unique high-resolution data set of cloud LWP over remote sea-ice-free Arctic ocean is retrieved. The airborne microwave retrieved LWP is compared with LWP retrieved from visible/near-infrared techniques taken on board the aircraft as well as with two different satellite products. The respective uncertainties and the agreement among the different techniques are discussed.  

The different cloud situations observed during the three ACLOUD periods are investigated to identify differences in LWP distribution from the airborne measurements. To analyze the representativity of the limitation to specific flight tracks, continuous ground-based observations at Ny-Ålesund, ERA5 reanalysis, and simulations with the ICON model are used. While in general the airborne sampling seems to be representative for the larger region systematic difference in LWP amount between the different products occurs which will be discussed in this presentation.