Global 2-D intercomparison of sectional and modal aerosol modules

[摘要] We present an intercomparison of several aerosol modules, sectionaland modal, in a global 2-D model in order to differentiate theirbehavior for tropospheric and stratospheric applications.We modelonly binary sulfuric acid-water aerosols in this study.Threeversions of the sectional model and three versions of the modal modelare used to test the sensitivity of background aerosol mass and sizedistribution to the number of bins or modes and to the prescribedwidth of the largest mode.We find modest sensitivity to the numberof bins (40 vs. 150) used in the sectional model.Aerosol mass isfound to be reduced in a modal model if care is not taken in selectingthe width of the largest lognormal mode, reflecting differences insedimentation in the middle stratosphere.The size distributionscalculated by the sectional model can be better matched by a modalmodel with four modes rather than three modes in most but not allsituations.A simulation of aerosol decay following the 1991 eruptionof Mt. Pinatubo shows that the representation of the size distributioncan have a signficant impact on model-calculated aerosol decay ratesin the stratosphere.Between 1991 and 1995, aerosol extinction andsurface area density calculated by two versions of the modal modeladequately match results from the sectional model. Calculatedeffective radius for the same time period shows more intermodelvariability, with a 20-bin sectional model performing much better thanany of the modal models.

[学科分类] 大气科学