Atmospheric Modeling for Electromagnetic Transmission Radiations in the Coastal Atmosphere – MATRAC

The "MATRAC" project proposes a detailed study of the source terms, dynamics and optical properties of the marine aerosol in the littoral zone in order to obtain a better understanding of the spatio-temporal variations of the particulate extinction coefficient. The expected results are part of an improvement in the range prediction of the operational tools of the French Navy in the visible and infrared domains and climate models via a better estimate of the radiative forcing of aerosol in the maritime area.

To do this, we propose an original methodology based on a physicochemical analysis of the aerosol in marine atmosphere and an innovative modeling approach. The objective is to provide a relevant numerical modeling of aerosols generated at the air-sea interface and their atmospheric dynamics in coastal areas at local scale in the double interest of refining on the one hand, estimates of radiative forcing of aerosols , which is necessary for the reliability of climate scenarios and, secondly, to validate an extinction model operating from a small number of inputs. These will consist of easily accessible environmental data (wind speed, air temperature and humidity etc.) so that the model is able to instantly calculate the extinction coefficient in the infrared and visible domains. . The scientific approach adopted will have the dual benefit of providing the forcings relevant to the extinction model, but also by a precise description of the environment, will allow the relevant tests necessary to improve the performance of the latter.
In this context, we propose a multi-scale approach based on a strategy of nested models and validated by experimental measurements. Special work will be done to determine the source terms of the marine aerosol and its atmospheric fate. The response of these aerosols to electromagnetic radiation will be studied in detail using innovative chemical analysis techniques. This should allow us to refine our knowledge of the optical properties of marine aerosol in coastal zone and thus improve the performance of extinction calculations based on Mie theory.

The results will be validated from the implementation of a first series of measurements in the Mediterranean coastal zone at the MIO laboratory station on the island of Porquerolles and a second taking place on the Atlantic coast. In addition, the acquired data will be compared to those previously recorded on other sites in various geographical regions of the world. This analysis will identify the generalizable properties of the MEDEX extinction model.

The objective of the modeling obtained will be to eventually increase the performance of the semi-operational modeling tools used to evaluate the propagation of electro-optical radiation in the marine atmospheric boundary layer (CLAM) and the radiative forcing calculations of the aerosols at the same time. using regional models. Finally, we will evaluate the consequences of the extinction coefficients provided by the new model on the performances of the MATISSE scene generator code developed by ONERA [Labarre et al. 2010]