Satellite retrieved aerosol properties for battlespace characterization and sensor performance

摘要

Sea basing operations in coastal environments require a rapid and accurate description of the physical conditions in the region. Battlespace characterization and sensor performance assist in optimizing the efficiency and safety of operations, of which the detection of targets at low level above the sea surface is all-important. The environmental conditions of the marine boundary layer (MBL) - due to weather and atmospheric effects - change continuously in space and time, which certainly holds for the aerosol make-up. Models have been developed to describe the electro-optical propagation in the boundary layer as a function of meteorological parameters. EOSTAR is such an end-to-end model suite for EO sensor performance in which the Advanced Navy Aerosol Model (ANAM) is embedded for computing the aerosol extinction. While ANAM provides favourable results in open ocean conditions, in coastal zones the model lacks accuracy due to the presence of aerosols from a variety of sources that need to be assessed. In offshore wind conditions continental aerosols of anthropogenic and natural origin mix with marine aerosols produced in the surf zone and by wave breaking further offshore. Radiometers on satellites can be used to retrieve the spatial variation over an extended area determined by the swath width, with a resolution determined by the radiometer pixel size. In this contribution we explore the potential of satellite measurements to provide information on the aerosol properties over the range of interest in order to correctly handle their influence on transmission characteristics in the coastal zone. Results from measurements of the multidisciplinary Maritime REA/Battlespace Preparation 2007 trial, held during 20 April and 5 May 2007 near the vicinity of the island Elba along the west coast of Italy, are presented in this analysis. For one particular day, the satellite retrieved aerosol optical thickness (AOT) is to be compared with hand-held sun photometer measurements for quality assessment. The AOT values are converted into aerosol extinction coefficients for a pre-defined path. For one visible wavelength channel the transmission loss is computed with these coefficients and is compared with the computed transmission loss for the path in case of a) a single extinction coefficient obtained from measurements and b) a modeled extinction coefficient obtained from ANAM.