S2I       Historical Solar Variability 

Over the past half-century the satellite era has yielded increasingly detailed datasets of light and particles emanating from the Sun, allowing investigations into solar variability and its impact on the Earth system. Ground-based measurements from neutron monitors, magnetometer observations and sunspot records provide insight before this time. However, beyond 400 years, the knowledge of solar variability relies on the interpretation of paleoclimate archives, most significantly cosmogenic radionuclides such as carbon-14 (14C) in tree rings and beryllium-10 (10Be) in polar ice cores.  Global climate models simulations are needed to understand the path from production of these radioisotopes in the upper atmosphere to sequestration in paleoarchives, with the hope of providing reconstructions of solar activity needed to predict the frequency and strength of solar storms as well as solar influences on global and regional climate


SEP     Energetic Particle Precipitation

Solar energetic particles (SEPs), galactic cosmic rays (GCRs), and electrons precipitating from the Van Allen radiation belts can enhance hydrogen oxides (HOx) and odd nitrogen (NOy) in the upper atmosphere, leading to the destruction of stratospheric ozone.  Simulations using NCAR's Whole Atmosphere Community Climate Model (WACCM-CESM) combined with observations from spacecraft and ground-based monitors allow us to quantify these atmospheric impact.  Initial model results, combined with surface snow and ice core measurements have also put to rest a 30-year controversy, warning against the use of nitrate ion spikes as a proxy for SEP events.


O3     Ozone Photochemistry and Transport 

By controlling levels of the hydroxyl radical (OH), ozone regulates the oxidation capacity of the troposphere, influencing background levels of trace chemical species.  Oxidation properties within the atmospheric planetary boundary layer in particular influence the fate of pollutants emitted from the surface as well as the amount of chemical deposition to the biosphere.  Polluted plumes coming from industrial regions along with biomass burning plumes from wildfires can affect ozone production and loss rates in remote regions, impacting background ozone levels in the global atmosphere.  While large amounts of progress have been made in past decades regarding the photochemistry of ozone and its precursors, questions still remain with respect to the fate and impact of polluted continental plumes on the global atmosphere.