| Summary: | This study investigates trend and variability of cloud liquid water path (LWP) over both the North Pole (NP) and the South Pole (SP). The period of analysis covers 34 years, from 1982 to 2015. Because of some main limitations of the LWP retrieval (availability of daylight and the problems with LWP retrieval over ice and snow) the study is focused on the summer seasons of the respective region that is June- July-August for the NP, and December-January-February for the SP). These summer seasons are those of sea ice melting whose trends have a signi cant importance in the study of climate change. Seasonal data were computed from monthly LWP, which is part of the cloud products of the CLARA-A2 archive, available from the EUMETSAT SAF on Climate Monitoring (CM SAF), derived from AVHRR observations of NOAA and EUMETSAT MetOp satellites. Observations for the Arctic and Antarctic regions are available on two equal-area polar grids at 25 km resolution and covers an area of 1000km 1000km. Linear trend in liquid water path during the analysed period sum- mer seasons are positive for both (about 1:0 kgm2=dec and 0:5 kgm2=dec for SP and NP, respectively), but the trend is statistical signi cant (at = 0:05) only for SP. At a ner spatial resolution, substantial differences are observed: i) in the Arctic, a signi cant increase over Greenland and a decrease over the Arctic Ocean; ii) in Antarctica, a signi cant increase over all the continent, apart a modest decrease around the pole, over the Ross Sea and near the western Antarctic coast. Spatial variability was tested by means of EOF technique. For both the Arctic and Antarctica, only the rst main eigenvector seems signi cant, in both cases explaining about the 20% of the variance. For the Arctic, the higher variability is noted near the pole and in the south-east of Greenland, while, for Antarctica, over the Ross Sea and its surrounding areas and near the opposite coastlines.
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