CHEM2D-OPP: A new linearized gas-phase ozone photochemistry parameterization for high-altitude NWP and climate models

摘要

The new CHEM2D-Ozone Photochemistry Parameterization (CHEM2D-OPP) forhigh-altitude numerical weather prediction (NWP) systems and climate modelsspecifies the net ozone photochemical tendency and its sensitivity tochanges in ozone mixing ratio, temperature and overhead ozone columnbased on calculations from the CHEM2D interactive middle atmosphericphotochemical transport model.We evaluate CHEM2D-OPP performance using both short-term (6-day) and long-term (1-year)stratospheric ozone simulations with the prototype high-altitudeNOGAPS-ALPHA forecast model. An inter-comparison of NOGAPS-ALPHA 6-day ozone hindcasts for7 February 2005 with ozone photochemistry parameterizations currently used in operationalNWP systems shows that CHEM2D-OPP yields the best overall agreement withboth individual Aura Microwave Limb Sounder ozone profile measurementsand independent hemispheric (10°–90° N) ozone analysis fields.A 1-year free-running NOGAPS-ALPHA simulation using CHEM2D-OPPproduces a realistic seasonal cycle in zonal mean ozone throughoutthe stratosphere. We find that the combination ofa model cold temperature bias at high latitudes in winter anda warm bias in the CHEM2D-OPP temperature climatologycan degrade the performance of the linearized ozonephotochemistry parameterization over seasonal time scalesdespite the fact that the parameterized temperature dependence is weakin these regions.