Particulate matter (PM) retrieval from SeaWiFS measurements

The fine particle abundance, i.e., particle matter (PM) concentration, is one of the indicators for air quality, and is therefore subject to ground-based measurements. Complementary, satellite aerosol remote sensing techniques are providing one with maps of the aerosol optical thickness (AOT) over land, which is sensitive to particle abundance. This paper investigates the problem of retrieving the PM concentration from the AOT, both on daily average values, based on a large data set where data from the air quality networks are combined with satellite based measurements of the AOTs and meteorological parameters such as wind speed, relative humidity and surface pressure. The proposed model is expressed as an additive varying-coefficient model (AVCM), which is defined as a linear model where the coefficients are additive functions of the auxiliary parameters. The model is represented using penalized smoothing splines, allowing for a proper control of the overall number of degrees of freedom via multiple smoothness parameters selection. The methodology is applied on AOTs retrieved over land from the SeaWiFS sensor and compared to data collected from air quality networks on the north of France, the Flemish part of Belgium and the Kent in England.