Influence of cloud cover and cloud types on shortwave radiation flux at Mendel station, northern Antarctic Peninsula

The cloud cover is a very important factor that influences many atmospheric processes and the Earth’s systems. The Antarctic Peninsula is located in the circumpolar low-pressure trough which results in high cyclonic activity and variable cloud cover. Despite its importance in planetary systems, the lack of cloud cover observations and instrumentations in Antarctica does not allow for detailed analysis of cloud radiative feedback. The gap in our knowledge is often filled by radiative transfer modelling, although its reliability needs to be verified as these models are usually calibrated outside of Antarctica. To study the influence of cloud cover and cloud types on the shortwave radiation (SR) flux, a summer experiment was conducted in the northeastern part of the Antarctic Peninsula. Ground-based observations were carried out at the J.G. Mendel station in the period from 26 January to 7 March 2025. The station is located in a coastal ice-free area with local albedo ranging between 0.2 (bare ground) and 0.9 (continuous snow cover). The SR intensity was measured using Kipp‌&Zonen CMP-11 pyranometer at 10-min interval and was used for estimation of the highest radiative flux and daily means. Sky camera was used for estimation of the cloud cover and cloud types using multicriterial analysis and processing of hemispherical images at 10-min interval. The total cloud cover and layer cloud amount were also observed manually. Furthermore, clear-sky SR flux was estimated using Bird and Hulstrom radiative transfer model. To further analyse the cloud radiative effect, we calculated a cloud modification factor. The model results were compared with manual cloud cover observations, sky camera imagery and ERA5 reanalysis data. SR flux for different cloud layers and cloud genera was examined for the most typical clouds, such as cirrus, cirrostratus, altostratus and altocumulus. Special attention was paid to the highest SR fluxes that occurred during clear-sky conditions, high-reflectance cloud layer or days with extreme radiative flux caused by multiple reflection between cloud cover and snow surface.