Phys.org  July 12, 2024 New particle formation in the free troposphere is a major source of cloud condensation nuclei globally. The prevailing view is that in the free troposphere, new particles are formed predominantly in convective cloud outflows. An international team of researchers (USA -Washington University, NASA Langley Research Center (VA), University of Colorado, NOAA (Boulder), National Center for Atmospheric Research, Boulder, Washington University in St. Louis, Austria) presented another mechanism using global observations. They found that during stratospheric air intrusion events, the mixing of descending ozone-rich stratospheric air with more moist free tropospheric background resulted in elevated hydroxyl radical […]