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WACCM‐D—Improved modeling of nitric acid and active chlorine during energetic particle precipitation
Author(s) -
Andersson M. E.,
Verronen P. T.,
Marsh D. R.,
Päivärinta S.M.,
Plane J. M. C.
Publication year - 2016
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2015jd024173
Subject(s) - mesopause , precipitation , atmospheric sciences , mesosphere , atmosphere (unit) , nitric acid , environmental science , climatology , chemistry , meteorology , stratosphere , geography , physics , geology , inorganic chemistry
Observations have shown that a number of neutral minor species are affected by energetic particle precipitation (EPP) and ion chemistry (IC) in the polar regions. However, to date the complexity of the ion chemistry below the mesopause (i.e., in the D region ionosphere) has restricted global models to simplified EEP/IC parameterizations which are unable to reproduce some important effects, e.g., the increase of mesospheric nitric acid (HNO 3 ). Here we use WACCM‐D, a variant of the Whole Atmosphere Community Climate Model which includes a selected set of D region ion chemistry designed to produce the observed effects of EPP/IC. We evaluate the performance of EPP/IC modeling by comparing WACCM‐D results for the January 2005 solar proton event (SPE) to those from the standard WACCM and Aura/Microwave Limb Sounder (MLS) and SCISAT/Atmospheric Chemistry Experiment‐Fourier Transform Spectrometer (ACE‐FTS) observations. The results indicate that WACCM‐D improves the modeling of HNO 3 , HCl, ClO, OH, and NO x during the SPE. Northern Hemispheric HNO 3 from WACCM‐D shows an increase by 2 orders of magnitude at 40–70 km compared to WACCM, reaching 2.6 ppbv, in agreement with the observations. For HCl and ClO, the improvement is most pronounced in the Southern Hemisphere at 40–50 km where WACCM‐D predicts a decrease of HCl and increase of ClO by 1.6% and 10%, respectively, similar to MLS data. Compared to WACCM, WACCM‐D produces 25–50% less OH and 30–130% more NO x at 70–85 km which leads to better agreement with the observations. Although not addressed here, longer‐term NO x impact of ion chemistry could be important for polar stratospheric ozone and middle atmospheric dynamics.