Aerosol-Cloud-Radiation Interactions in Northern regions

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Ice and mixed-phase clouds play an important role in the Arctic weather and climate system. Consequently, it is essential to understand their properties and especially their formation process. Remote sensing observations over the Arctic have revealed the existence of two types of ice clouds (TIC) during winter. The first type, TIC-1, is characterized by a high concentration of small ice crystals and is typically observed in non-polluted areas. On the other hand, TIC-2 is characterized by a low concentration of larger precipitating ice crystals. In this study, it is hypothesised that TIC-2 are linked to highly polluted environments. Past field experiments have shown that most aerosols in the accumulation mode are coated by sulphuric acid in polluted episodes in the Arctic during spring and winter. Recent laboratory experiments have shown that acid coating can alter the efficiency of ice nuclei particles (INP) to nucleate ice crystals. In this study, we hypothesize that the resulting lower IN concentration found in polluted air masses leads to the decrease of the ice crystal concentration. Since there is in less competition for the available moisture, ice crystals reach precipitating sizes leading to the formation of TIC-2. This research aims to better understand the formation process of these two types of TIC through the use of chemical transport models (WRFCHEM and GEM MACH) couple with state of the art ice microphysics.