Analysis of Arctic clouds by means of hyper-spectral satellite

Polar satellite measurements provide frequent overpass on the Arctic area and high spatial resolution, but the cloud parameter retrieval and their detection is very difficult at high latitudes. In great part the Arctic surface is covered by snow and ice, reducing the visible contrast between clouds and the surface. Also, often there are strong surface temperature inversions and during the winter there is no solar contribution, then the techniques based on reflectance in the visible and near infrared (e.g. 1.6 μm channel) are not applicable. Moreover, Arctic clouds are often low and thin and composed of mixtures of ice and water (Curry et al., 1996). The main objective of this study is to understand if the new generation of infrared high spectral resolution satellite instruments offer an opportunity to improve the detection of clouds in the Arctic. The paper shows the effect of sea/ice/snow emissivity spectra on simulated radiances in the IR wavenumber range often used for cloud detection (700-1000 cm-1), and the impact of surface emissivity uncertainties on the performances of current polar night-time cloud detection techniques based on hyper-spectral observations. Finally, a possible improvement to the polar cloud detection is presented and validated on the basis of the Cloud Profiling Radar (CPR) data.