The influence of cloud chemistry on HOx and NOx in the moderately polluted marine boundary layer: a 1-D modelling study

[摘要] A 1-D marine stratocumulus cloud model has been supplemented witha comprehensive and up-to-date aqueous phase chemical mechanism for the purpose of assessing the impact that the presence ofclouds has on gas phaseHO_x, NO_x and O₃ budgets in the marine boundary layer. The simulations presentedhere indicate that cloud may act as a heterogeneous source of HONO_g. The conversion ofHNO_4(g) at moderate pH (~ 4.5) is responsible for this, and, to a lesser extent, thephotolysis of nitrate (NO₃^-). The effect of introducingdeliquescent aerosol on the simulated increase of HONO_g is negligible. The most important consequences of this elevation inHONO_g are that, in the presence of cloud, gas phase concentrations ofNO_x species increase by a factor of 2, which minimises the simulated decrease inO_3(g), and results in a regeneration of OH_g. This partly compensatesfor the removal of OH_g by direct phase transfer into the cloud and may have important implications regarding the oxidisingcapacity of the marine boundary layer.

[学科分类] 大气科学