Datensatz

Zusammenfassung

Aerosols play an important role in the global climate system. However, their effects on the radiation budget and even their global distribution and composition are not understood satisfactorily. The objective of this study is to advance the understanding about the global tropospheric aerosol system as basis for higher accuracy estimates of the anthropogenic aerosol effects. In traditional global aerosol models, aerosol size-distribution and mixing-state are prescribed. This limits local representation and applicability to different climatic regimes. To overcome these de?ciencies, the global aerosol-climate model ECHAM5-HAM has been developed. In the aerosol module HAM, the aerosol distribution is represented by an ensemble of interacting internally and externally-mixed log-normal aerosol modes with prognostic treatment of aerosol size-distribution, mixing-state, and composition. In the current setup, the major global aerosol compounds sulfate (SU), black carbon (BC), particulate organic matter (POM), sea salt (SS), and mineral dust (DU) are included. The simulated global annual-mean aerosol burden (lifetime) for the year 2000 are for SU: 0.80 Tg(S) (3.9 days), for BC: 0.11 Tg (5.4 days), for POM: 0.99 Tg (5.4 days), for SS: 10.5 Tg (0.8 days), and for DU: 8.28 Tg (4.6 days). An extensive evaluation with in-situ and remote sensing measurements underscores that the model results are generally in good agreement with observations of the global aerosol system. The simulated global annual-mean aerosol optical depth (AOD) is at 0.14 in excellent agreement with an estimate derived from AERONET sun-photometer measurements (0.14) and a composite derived from MODIS-MISR satellite retrievals (0.16). Although on a regional basis the differences are not negligible, the main patterns of aerosol optical depth are reproduced.