Modeling wet deposition and concentration of inorganics over Northeast Asia with MRI-PM/c

Abstract

We conducted a regional-scale simulation over Northeast Asia for the year 2006 using an aerosol chemical transport model, with time-varying lateral and upper boundary concentrations of gaseous species predicted by a global stratospheric and tropospheric chemistry-climate model. The present one-way nested global-through-regional-scale model is named the Meteorological Research Institute–Passive-tracers Model system for atmospheric Chemistry (MRI-PM/c). We evaluated the model's performance with respect to the major anthropogenic and natural inorganic components, SO₄^2&minus;, NH₄⁺, NO₃^&minus;, Na⁺ and Ca²⁺ in the air, rain and snow measured at the Acid Deposition Monitoring Network in East Asia (EANET) stations. Statistical analysis showed that approximately 40–50 % and 70–80 % of simulated concentration and wet deposition of SO₄^2&minus;, NH₄⁺, NO₃^&minus;and Ca²⁺ are within factors of 2 and 5 of the observations, respectively. The prediction of the sea-salt originated component Na⁺ was not successful at near-coastal stations (where the distance from the coast ranged from 150 to 700 m), because the model grid resolution (&Delta;<i>x</i>=60 km) is too coarse to resolve it. The simulated Na⁺ in precipitation was significantly underestimated by up to a factor of 30.