Aerosol particles in the Mexican East Pacific Part I: processing and vertical redistribution by clouds

[摘要] Airborne measurements of aerosol particle size distributions were made inthe Mexican Intertropical Convergence Zone. The volume concentrations of submicronand super micron particles at cloud base were compared with those in near-cloud regions over a range of altitudes. Of78 near-cloud regions analyzed, 68% and 45% had enhanced volumes ofsubmicron particles and supermicron particles, respectively. In addition,35% of these regions had supermicron particles removed, presumably byprecipitation. In 61% of the cases the enhancement in volume occurredover the size range from 0.1 to 50 μm whereas only submicron volumeswere enhanced in 35% of the cases. In regions near clouds that wereformed in air of maritime origin the frequency of volume enhancementdecreased with increasing altitude and was twice as frequent on the dissipatingside of clouds compared to the growing side. No such differences were found in theregions near clouds formed in air originating from the land. The frequencyand average magnitude of volume enhancement are in qualitative andquantitative agreement with previous observational and theoretical studiesthat relate enhancements in particle mass to the uptake by cloud droplets ofSO₂ accompanied by additional growth by droplet coalescence.

[学科分类] 大气科学