Characteristics of clouds in the Arctic: Comparison of NABOS expedition data with satellite observations

Clouds play an important role in the Arctic climate system, having a significant warming effect during almost an entire year. However, the existing numerical estimates of cloud-radiative characteristics differ significantly according to various data. 

This paper analyzes the characteristics of cloud cover, radiation fluxes, and cloud-radiation effects (forcing) on the surface based on three NABOS (Nansen and Amundsen basins observation system) polar expeditions in the central regions of the Arctic Ocean. The expeditions were performed in August-September 2013, 2015, and 2018 on the scientific research vessels Akademik Fedorov and Akademik Treshnikov. The cloud-radiation characteristics obtained from the expedition observations are compared with the CERES satellite data. Cloud variables were calculated for different sea ice conditions, depending on sea ice concentration (SIC), namely, for open water (SIC<5%), transient sea ice concentration (5%≤SIC≤95%) and solid ice (SIC>95%).

We found that satellite data show more broken clouds compared to NABOS observations and almost no clear-sky episodes. This discrepancy results in a slightly weaker warming effect but a much weaker cooling effect in CERES compared to NABOS data. Consequently, the NABOS shipborne observations show that clouds contribute to surface cooling with a net CRE of -10.1 W m⁻², while the CERES satellite data for the same dates and regions show that clouds have a warming effect with a net CRE of 30.2 W m⁻².

The consistency of NABOS and CERES data depending on different external parameters (sea ice cohesion, solar altitude, cloud characteristics) was analyzed. The greatest discrepancies between the data are noted for the transient ice concentration: above the completely open or completely ice surface the agreement is higher. A multidirectional statistically significant correlation between the fluxes (different for short- and long-wave fluxes) and the cloud fraction was obtained. The dependence on the cloud phase was revealed: in general, the correspondence between fluxes is higher for ice clouds than for water clouds.