The project is to develop a feasibility model for predicting the spatio-temporal variation of Aerosol Optical Properties in marine and coastal Maritime Environment.
Taking into account the evolution of this environmental phenomenon created by the wind on the sea surface is performed using the coupling model MEDEX (LSEET / MIO) and the fine mesh forecast model AROME developed by METEO-FRANCE.
MEDEX estimates the marine aerosol particle size concentration as a function of wind speed, relative humidity and fetch, representing the distance over which the wind has spread over the sea. AROME provides the spatio-temporal variation of wind field in coastal areas.
The project is divided into three parts. We proceed first to semi automation of the marine aerosol measurement station from the island of Porquerolles. Modifying the MIO experimental station offers the possibility to remotely trigger particle concentration measures, without the need for daily human presence on the island. The choice of measurement periods is made according to weather and environmental conditions provided by Météo France and relevant to the study.
This approach allows to update the marine aerosol MEDEX model. Based on a significant number of local measurements, semi-empirical formulations of the model are evaluated and consolidated.
Finally, the software feasibility model coupling Medex and AROME is introduced.
From the spatial variation of different meteorological fields evaluated by AROME and particle size spectra provided by MEDEX, the horizontal distribution of marine aerosol optical properties is estimated. The fetch processing is revised to take into account the wind lines over the aerosol evaluation area. An experimental validation based on blackbody radiance measurements is used to show the need to take into account precisely mapping marine aerosols in tools for predicting optronic sensors performance.
The map below shows an example of the spatial distribution in the region of Toulon (south of France) of the 10-micron particle size concentration and wind fields (speed and direction).
The aerosol spatial variation has an impact on the azimuthal distribution of atmospheric attenuation (see POAEMM logo) and therefore on the capabilities of an IRST system, to detect and identify a target. The following figure shows for a long fetch, the influence of wind speed on the DRI distance for a ship as tracking by a mid-infrared sensor.
The project is funded by the National Research Agency (ANR) in the 2011 ASTRID program (Specific Coaching for Works Research and Innovation Defence).