| Abstrakt: |
A chemistry model of the global troposphere is presented which focuses on the hydroxyl radical, OH. Global distributions of OH are calculated based on known chemical reaction pathways, experimentally measured values of precursor species O3, H2O, NOx (defined as NO + NO2), CO, CH4, and actinic flux (which includes the effects of cloud cover and O3 column absorption). Model grid resolution is 1 km in altitude by 10° latitude, and zonally divided into land or ocean. Species are calculated as seasonal averages. Global annual mean OH in the troposphere (up to 14 km altitude) is calculated to be 9.2 × 105 mol cm−3 with averages of 9.8 × 105 in the northern hemisphere, and 8.5 × 105 in the southern hemisphere. Global CO and CH4 oxidation rates by OH are calculated to be 1840 Tg year−1 and 580 Tg year−1, respectively. OH is found to be most sensitive to O3 and H2O concentrations, as well as to the photolysis rate of O3 to O(1D). Sensitivity of CO and CH4 oxidation rates to cloud presence shows an inverse relationship to cloud amount and optical depth. Model results are shown to be consistent with results from two other published models. [Copyright &y& Elsevier] |
Full Text from ScienceDirect