Rapid warming in the Arctic is highly impacting the cryosphere in the region, causing melting of the sea ice, retreat of glaciers and reduction in the snow cover. If suffering further temperature increase, the albedo of the region would reduce due to higher absorption of the solar radiation in snow-free areas. The variations in seasonal snow cover in Arctic regions can impact a lot of things including the ecosystem, biodiversity, hydrological cycle, and many other physical processes. Therefore, it is beneficial to have the knowledge of processes determining the snow distribution and to understand the trends and patterns of the seasonal snowcover.In this project, seasonal snow cover trends and patterns have been studied for a 30-year period from 1991 to 2020 using a newly developed reanalysis dataset called Copernicus Arctic Regional Reanalysis (CARRA). A validation of the CARRA data set has been done for the snow depth using point observation data from the Norwegian weather stations and a visual snow cover comparison using Sentinel-2 remote sensing data. Thereafter, interannual variability in day of snow disappearance, day of snow onset, duration of snow-free period, and maximum snow depth have been analysed and these trends are then discussed in detail.The results show that for the most non-glaciated regions in Svalbard, the snow onset is happening later in the winter season while the day of snow disappearance is arriving earlier in the spring. Consequently, the duration of snow-free period has increased in almost all regions of Svalbard except a few sites where the duration of the snow free-period has decreased most likely due to local climatic factors. These factors can be better understood by incorporating meteorological elements like precipitation, air temperature and wind speed. Overall, the CARRA reanalysis dataset is very good in determining snow cover trends in non- glaciated regions of Svalbard and with some updates and modifications, it might be able to determine snowcover for the glaciated regions in future.

Polar mesoscale cyclones (PMCs) are low-pressure systems that form in polar regions. Their small size and short lifespan pose challenges for coarse resolution models in capturing PMCs and their associated air-sea mass and energy transfer. To address the influence of resolution on PMCs, a comparison between a higher resolution dataset (CARRA with 2.5 km resolution) and a lower resolution reanalysis dataset (ERA5 with 30km resolution) over a 10-year period in the North Atlantic is conducted by employing an automatic algorithm. The results revealed that CARRA detected a greater number of PMC activities, highlighting the benefits of higher resolution data in reducing uncertainties during tracking. PMCs identified using CARRA exhibited smaller vortex sizes, but higher relative vorticity and faster movement speeds compared to ERA5 results. Notably, the typical vortex diameters derived from ERA5 and CARRA were 80 km and 120 km, respectively. Furthermore, the climatology of PMCs in the North Atlantic is presented. Monthly variations indicated that the majority of PMCs occurred during winter, with only a few cases developing in summer. The spatial distribution exhibits that the highest density of PMCs was observed in the Irminger Sea and the Norwegian Sea. It also shows that the presence of sea ice can influence the PMC density, as a significant number of cases formed near the sea ice edge. The comparison results indicate that the current coarse climate simulation may underestimate the influence of PMCs in the Arctic due to the misrepresentation of them, thus introducing uncertainties in the climate prediction.

The pamphleteers popularized the mythology of despotism by denouncing lettres de cachet and other supposed abuses of power that had little effect on most people. Historians like Funck-Brentano may be correct in arguing that the government was really moderate at this time, but it is important to show that radical propagandists were quite successful in convincing Frenchmen that thousands of innocent victims huddled miserably in <em >cachots for having inflamed the despotic passions of a minister. Moreover the prisons that were mythological for most Frenchmen had been terribly real for Brissot, Carra, Gorsas and many other writers, and this consideration also suggests the importance of the biographical approach. The Bastille may have been nearly empty, but it was a powerful symbol, effectively exploited by pamphleteers who dealt in symbols, declamation and distortions of political realities. They were highly successful in dominating public opinion, which exerted an influence on events that has been unappreciated in relation to the weak, irresolute rule of Louis XVI. The thesis attempts to develop this interprettion of the political importance of radical propaganda with reference to the scientific, financial and literary history of the period. It may seem weak on some ponts of these specialized fields, but it is hoped that it assimilates them successfully in its main attempt to contribute to an understanding of the last years of the Ancien Regime: its analysis of the character of radical propaganda in relation to the men who created it.