Satellite-Derived Aerosol Variability over China

Abstract:

The main objective of the MarcoPolo project is to improve air quality monitoring, modelling and forecasting over China using satellite-retrieved observations of aerosols, NO_x, SO₂, and biogenic gases. This information will be used to derive emission estimates which will be used together with known information from the ground, to construct a new emission database for use with regional and local air quality models. In this contribution we report on the use of satellite data to obtain information on the occurrence of aerosols over China. Several different instruments, in particular MODIS and AATSR, are used to provide the spatial AOD since 2002 as well as a merged AOD product providing improved coverage. CALIOP is used to provide information on the vertical structure of aerosols, including aerosol type information. The AOD data sets are validated and evaluated versus sun photometer data from AERONET and the Chinese network CARSNET. This is particularly valuable because aerosol retrieval algorithms are developed and validated over areas where many independent ground-based observations are available, such as over the eastern USA and Europe. However, over these areas the AOD levels are generally much lower than over China, and the occurrence of such high AOD, combined with the variation in aerosol type and surface characteristics, poses particular problems as regards data selection and discrimination between high AOD and the occurrence of clouds. An initial analysis of the spatial and vertical variability of the AOD is provided and time series showing the variation over representative areas are presented, combining the various information sources indicated above. AOD time series will be compared with those from precursor gases and model estimates.