Abstract:
Organic chemistry does not only occur in your round bottom flask; it is occurring all around you and all the time in the atmosphere! There are organic molecules in the gas phase, in the particle phase as well as in the aqueous phase. An organic aerosol particle has a typical lifetime of approximately one week in the atmosphere, enough time to scatter solar radiation, to form clouds and thus to impact climate. During an aerosol’s lifetime, numerous chemical reactions take place often through radical reactions initiated by photochemistry. Yet, the effect of photochemistry on the propensity of organic matter to participate in the initial cloud-forming steps is difficult to predict. My group’s research focuses on atmospheric processing of dissolved organic matter and its ability to form cloud droplets and to form ice crystals. We have identified a photomineralization mechanism which we have quantified by monitoring the loss of organic carbon and the simultaneous production of organic acids, CO and CO2. This mechanism explains and predicts the observed increase in cloud condensation nuclei and decrease in ice nucleating particle efficiencies. We are therefore putting forward that photomineralization can alter the aerosol-cloud radiative effects of organic matter by modifying the supercooled liquid water-to-ice crystal ratio in mixed-phase clouds with implications for cloud lifetime and precipitation patterns. In other words, cool cloud chemistry has a non-negligible impact on climate.