1-D Air-Snowpack Photochemical Model PHANTAS: An Update

Snowpack on sea ice and nearby land surface is an active source of reactive halogen species to the overlying atmosphere in polar regions, leading to substantial ozone depletion as observed especially during the springtime. We have been developing a one-dimensional model, PHANTAS (PHotochemistry ANd Transport between Air and Snowpack), which describes the transport of trace gases between the snowpack and the overlying atmosphere as well as their photochemical reactions in the gas phase and in the condensed phase of aerosols and snowpack. Recent updates of the model include: 1) representation of advective wind-pumping process in the snowpack by two columns (i.e. upward- and downward-flow branches) and, 2) vertical discretization of the atmosphere from viscous sublayer to stable but turbulent boundary layer. Sensitivity studies are performed to show that surface wind promotes the turbulent mixing in the boundary layer and the pumping in the snowpack and, consequently, reactive halogen release from the snowpack. Simulated vertical gradients in the snowpack and in the near-surface atmosphere are also scrutinized for bromine and chlorine chemistry, ozone loss, and nitrogen oxides and aldehydes emitted/adsorbed by the snowpack.