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Assessment of spatial and temporal variation of aerosols optical properties in maritime and coastal environment – POAEMM

French Navy vessels optronic sensors performances

Within the frame of a given operation theatre, Navy vessels need to evaluate their optronic sensors detection range. Taking into account the marine aerosols spatial variation will allow for an appropriate estimation of the involved sensors performances.

Impact of marine aerosols on infrared propagation in maritime and coastal environment

In the atmosphere, aerosols particles play a fundamental role in numerous natural processes. Through their capacity to interfere with electro-magnetic radiations, they will impige the radiative balance and contribute to attenuate the detection performances of electro-optical systems on-board <br />The aim of the POAEMM project is to create un mock-up, using the MEDEX parametric model (LSEET/MIO) and meteorological forecast (AROME, Météo-France) to provide horizontal repartition maps for aerosols optical properties, in low atmospheric layers maritime coastal environment. <br />This coupling, associated with a radiative transfer calculation tool (MATISSE or MODTRAN type) will be able to improve the estimation of atmospheric effects on infrared propagation, and, thereby, optronic sensors performances processing. <br />This approach could be used in a fast and operational way by the French Navy on operation sites to obtain short term forecast.

The project consists in the development of a feasibility mock-up to predict optical properties spatiotemporal variation of marine aerosols in coastal environment.
Taking into account the evolution of these environmental effects on atmospheric infrared propagation, as created by wind effects on sea surface, is realised through coupling the MEDEX model (LSEET/MIO) and the fine mesh model AROME, from météo-France.
MEDEX calculates a marine aerosol local granulometric density, as a function of wind speed, relative humidity and fetch (propagation distance of wind above the sea).
AROME outputs the wind field spatiotemporal variation in maritime and coastal zones.
The POAEMM project logic is based on three steps:
• Semi-automatisation of the Porquerolles Island marine aerosols measuring station (capacity of remote trigger of granulometrical and meteorological measures in appropriate environmental situations)
• MEDEX model improvement for marine aerosols density (based on a great amount of locally measured data, semi-empirical MEDEX formulations are revised to better take into account environmental conditions)
• Feasibility mock-up integrating and coupling MEDEX and AROME outputs, with experimental validations, based on a black body luminance measurement campaign.

The project experimental aspect will allow to set up a permanent semi-automatic measurement station in the Mediterranean sea, dedicated to marine aerosols knowledge.
Collected data will allow to consolidate and refine the MEDEX model (LSEET/MIO).
AROME, Météo-France forecast tool, provides environmental spatiotemporal variations. Take by MEDEX as input, this variation will give access to the marine aerosols granulometric spatial variation, and thereby their optical properties.
In a more global problematic, coastal infrastructures protection imposes the knowledge of threat analysis and detection means which must integrate their performances evaluation system as a function of the triplet detection system/environment/threat.
Optronic sensors performance estimation must take in account the aspect. The final study results will demonstrate the necessity, in some environmental situations, to take in account marine aerosols spatial variation and its impact on atmospheric attenuation, which is a critical component in performances evaluation.

The project is part of a specification and development axis for an optronic systems performance prediction tool integrating horizontal non-homogeneities of marine aerosols.

The obtained results within the MEDEX new version, and the validation of the AROME output coupling through optronic measurements wil be published in ITBMS type conferences (ONERA, FGAN).
Scientific results will be presented in an international congress. The “International Aerosol Conference”, whose last session was held in Helsinki in septembre 2010, is an appropriate contect for the matter.
A paper in a peer reviewed international magazine (JGR or Atm. Res.) is also scheduled.

The project is to develop a feasibility model for predicting the spatial and temporal variation of aerosols optical properties in marine coastal environment. Taking into account the evolution of this environmental phenomenon created by the effect of wind on the sea surface is achieved by coupling the MEDEX model (LSEET) and the fine mesh model AROME developed by Meteo-France.

MEDEX estimates the concentration of marine aerosol particle size depending on wind speed, relative humidity and "fetch". "Fetch" represents the distance the wind has spread over the sea. AROME provides spatial and temporal variation of the wind field in coastal environment

The project is divided in three parts. The first step is to make the semi-automation of the marine aerosols measuring station on the Porquerolles Island . The modification of the LSEET's experimental station offers a remote capacity for size concentration measurements. The choice of the measurement period will be made according to environmental and weather conditions provided by AROME.

This approach allows to improve the marine aerosol modeling in the second step of the project. Based on a large number of local measurements, semi-empirical formulations of MEDEX are revised in order to take better account of oceanographic and meteorologic conditions.

The final step is the realization of the feasibility model, integrating MEDEX and AROME. From the spatial and temporal variation of different meteorological fields provided by AROME and aerosols granulometric spectrum from MEDEX, the horizontal distribution of marine aerosols optical properties is estimated. An experimental validation based on radiance measurements of a black body is conducted to demonstrate the need to take into account precisely the marine aerosols mapping in tools for predicting optoelectronic sensors performances.

Project coordinator

Monsieur André FOUSSAT (CS SYSTEMES D INFORMATION) – andre.foussat@c-s.fr

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

MF METEO FRANCE
CS SI CS SYSTEMES D INFORMATION
LSEET UNIVERSITE DE TOULON ET DU VAR

Help of the ANR 281,298 euros
Beginning and duration of the scientific project: November 2011 - 24 Months

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