Monitoring of aerosol properties from space for air quality studies

摘要

In March 2002 the launch of the European environmental satellite ENVISAT is planned. ENVISAT carries several instruments to observe atmospheric and ground features. By exploiting the synergy of the spectrometer SCIAMACHY (Scanning Imaging Absorption Spectrometer for Atmospheric Cartography) and the radiometer AATSR (Advanced Along Track Scanning Radiometer), both onboard ENVISAT, the spectral aerosol optical thickness (AOT) and through the spectral dependence the type of the aerosol mixture can be retrieved. As a result of the synergetic aerosol retrieval (SYNAER) AOT maps of 1 km horizontal resolution can be produced. This was demonstrated by exploiting a similar sensor pair, namely GOME (Global Ozone Monitoring Experiment) and ATSR-2 (Along Track Scanning Radiometer number 2), which are both still operational on the ERS-2 platform. These AOT maps can be used as an indicator of the load of particles in the air. The retrieved aerosol type contains information on chemical characteristics and the size distribution of particles in as far as the optical properties are altered by these microphysical properties. However, AOT values are integral results of all particles in the total column. For direct use of satellite-based aerosol measurements in air quality monitoring these remote sensing results have to be converted into near-surface particle mass concentration values for particles of different size ranges (e.g. PM10, PM2.5 or additionally PM0.5). This paper investigates several steps to solve this task. The accuracy of the conversion of AOT results into PM values depends on knowledge of the type of aerosols (which is estimated by SYNAER) and the vertical profile. It is shown that the UV part of the SCIAMACHY/GOME spectra contains information on the height of the boundary layer of absorbing aerosols and the stratospheric aerosol loading. Furthermore, a significant correlation was found between AOT values at 550 and 1000 nm and the mass concentrations of fine particles (PM0.5) and coarse particles (PM10-PM0.5), respectively.