Status report on the key climate variables technical supplement to the
Significant data management issues
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Significant data management issuesThe GAW aerosol programme deals with a wide variety of global issues that are quite different from those that concern classical meteorology. Observations of chemical composition require additional sophistication in measuring techniques including awareness of data quality. A number of calibration centres are directly related to the aerosol issue. A World Calibration Centre for Physical Aerosol Parameters has recently been established at the Institute for Tropospheric Research, Leipzig Germany, a World Calibration Center for Chemical Aerosol Parameters remains to be assigned. The World Optical Depth Research and Calibration Centre (WORCC), at Physikalisch-Meteorologisches Observatorium, Davos, Switzerland, is responsible for the precision filter radiometer (PFR) measurements of aerosol optical depth within GAW, see http://www.pmodwrc.ch/. The establishment of the World Data Centre for Aerosols (WDCA) at the Joint Research Centre (JRC), European Commission, Ispra, Italy, see http://www.ei.jrc.it/wdca/, has provided a central archive for research data and a portal to regional monitoring network archives. However, confident integration of global data on specific aerosol compositional parameters, e.g. sulphate, may not be possible due to the absence of metadata on operational and analysis procedures as well as ongoing inter-comparisons/validation exercises. This is also the situation for regional monitoring networks. Publication sensitivities can make data access difficult for research sites and research projects. No global infrastructure exists to facilitate the necessary access and transfer processes, although a GAW information system (GAWSIS) has been established where station data and measured parameters can be found, see http://www.empa.ch/gaw/gawsis. Analysis productsClimatologies of aerosol properties, and in particular time histories of these characteristics, are useful to document changes in climate, as well as to evaluate possible causal links with specific effects. Aerosol properties and distributions are also useful for atmospheric chemistry studies and impact assessments. To date standard products for GAW sites are very limited. The WDCA produces time series data that have been subject to QC analysis. These include time series for individual stations as well as regional averages; indices of trends, means, and seasonal cycles. Monitoring networks produce statistical and trend data. Current Capability Very few stations having a strong link to aerosol research groups are performing more than half of the measurements listed above, and none of them perform the full suite of measurements. Globally the current observational capacity is severely limited and significantly reduced by comparison with earlier decades. This is largely due to the closure of research sites operated in remote areas and maritime locations. There is an urgent need to re-establish key sites and develop new sites that will provide data for remote and developing areas. The GAW network needs to be expanded to meet global aerosol measurement requirements. The estimation of aerosol amount from satellite data is rather well understood over oceanic surfaces, in large part due to the relative simplicity and homogeneity of the underlying dark sea surface. Similar approaches have been proposed to derive their properties over dense dark vegetated surfaces. However, the characterization of aerosols over bright land areas is generally complex and fraught with difficulties, because the corresponding inversion problem is particularly ill conditioned. Significant attempts to document the spatial and temporal distributions of aerosol properties are underway under the leadership of space agencies. Issues and priorities
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