Aerosol Retrieval and Assimilation (ARIA) - final report

Climate assessments are hampered by the large uncertainties involved in the estimation of the effect of atmospheric aerosol. These uncertainties are caused partly because sources and sinks as well as atmospheric processing of the different types of aerosol are not accurately known.Moreover, the climate impact (especially the indirect effect) of a certain aerosol distribution is hard to quantify. There have been different approaches to reduce these uncertainties. In recent years intensive observational campaigns like ACE and INDOEX have been carried out,aiming to increase our knowledge of atmospheric processes that determine the fate of atmospheric aerosol and to quantify the radiationeffects. With the new satellite instruments, such as SCIAMACHY and OMI it will be possible in the near future to derive the geographical distribution of the aerosol optical depths (AOD) and perhaps additional information on the occurrence of different types of aerosol. With the assimilation of optical depth observations into an aerosol chemistry transport model it is in principle possible to obtain global 3-dimensional fields of aerosol, which are needed for the estimation of radiative forcing. Although the retrieval, assimilation, and aerosol modeling techniques are still under development, it is believed that the combination of satellite observations and modeling can lead to major improvements of the assessment of the effect of atmospheric aerosols on climate.

This report describes the work that has been done in phase 1 (from 15/9/2001 to 31/4/2002) of the project ARIA, Aerosol Retrieval and Assimilation. Partners in this project are KNMI and TNO-FEL. The project aims to improve the retrieval of aerosol optical depths from satellite instruments such as SCIAMACHY and OMI, and to develop an aerosol chemistry transport model as well as scheme for the assimilation of optical depth observations. Goal of phase 1 was to develop a working prototype of a complete retrieval-assimilation system.