Parametric sensitivity and uncertainty analysis of dimethylsulfide oxidation in the clear-sky remote marine boundary layer

[摘要] Local and global sensitivity and uncertainty methods are applied to a box model of thedimethylsulfide (DMS) oxidation cycle in the remote marine boundary layer in order todetermine the key physical and chemical parameters and sources of uncertainty. The modelconsiders 58 uncertain parameters, and simulates the diurnal gas-phase cycles of DMS,SO₂, methanesulfonic acid (MSA), and H₂SO₄ for clear-sky summertime conditionsobserved over the Southern Ocean. The results of this study depend on many underlyingassumptions, including the DMS mechanism, simulation conditions, and probabilitydistribution functions of the uncertain parameters. A local direct integration method isused to calculate first-order local sensitivity coefficients for infinitesimal perturbationsabout the parameter means. Key parameters identified by this analysis are related to DMSemissions, vertical mixing, heterogeneous removal, and the DMS+OH abstraction and additionreactions. MSA and H₂SO₄ are also sensitive to numerous rate constants, which limitsthe ability of using parameterized mechanisms to predict their concentrations. Of thechemistry, H₂SO₄ is highly sensitive to the rate constants for a set of nighttimereactions that lead to its production through a non-SO₂ path initiated by the oxidationof DMS by NO₃. For the global analysis, the probabilistic collocation method is usedto propagate the uncertain parameters through the model. The concentrations of DMS andSO₂ are uncertain (1-σ) by factors of 3.5 and 2.5, respectively, while MSA andH₂SO₄ have uncertainty factors that range between 4.1 and 8.6. The main sources ofuncertainty in the four species are from DMS emissions and heterogeneous scavenging, butthe uncertain rate constants collectively account for up to 59% of the total uncertaintyin MSA and 43% in H₂SO₄. Of the uncertain DMS chemistry, reactions that form anddestroy CH₃S(O)OO and CH₃SO₃ are identified as important targets for reducing theuncertainties.

[学科分类] 大气科学