Airborne measurements of the cloud impact on the surface radiative energy budget in the Fram Strait

Clouds play an important role in the climate system of the Arctic. The interaction of clouds with atmospheric radiation has a significant influence on the radiative energy budget (REB) of the Arctic surface, which is quantified by the surface cloud radiative effect (CRE). Due to the counteraction of the cooling effect of clouds in the solar and their warming effect in the thermal-infrared spectral range, the total CRE depends on a complex interplay of the illumination, surface, thermodynamic, and cloud conditions.

To characterize the CRE for a variety of environmental conditions, broadband radiation measurements were performed during three seasonally distinct airborne campaigns. The flights were conducted over sea ice and open ocean surfaces in the eastern Fram Strait. The analysis focusses on the differences of the CRE with respect to the different campaigns and surface types. It was found that clouds cool the open ocean surface during all campaigns. In contrast, clouds mostly have a warming effect on sea ice–covered surfaces, which neutralizes during mid-summer. Given the seasonal cycle of the sea ice distribution, these results imply a cooling effect of clouds on the surface during the sea ice minimum in late summer and a warming effect during the sea ice maximum in spring in the Fram Strait region. The variability of, e. g., cloud and synoptic conditions causes deviations of the CRE from these statistics. In particular, the study presents the evolution of the CRE during selected cases of warm air intrusions and marine cold air outbreaks.