MATRAC - Optical properties in coastal areas
Atmospheric model to assess the EO transmission in coastal areas
Principal Investigator : J. Piazzola (MIO UMR 7294)
Partners : LHEEA (UMR 6598), CINaM (UMR 7325) et CNRM (UMR (3589)
The aim of the present study is to develop a numerical modeling framework for the aerosol concentrations and composition in a complex coastal environment, based on a multi-scale approach using grid-nesting models.
This framework serves to test the performance of semi-operational modeling tools that assess aerosol radiative forcing and propagation of electro-optical radiation through the Marine Atmospheric Boundary Layer (MABL), and to assess the feasibility of improving these tools in the near-future.
Among the large number of aerosol sources present in coastal areas, sea-spray aerosols formed by the interaction of air and water represent a major component of the natural aerosol mass (Fig. 1).
Fig. 1: Size spectrum measured in maritime environment. Arrows globally point to typical diameters for the processes mentioned
MATRAC proposes a multi-scale, nested approach. Starting from the model with the largest domain and coarsest resolution, each subsequent model treats a smaller, inner domain with a higher resolution. In this process, each “parent” model provides the boundary conditions to its “child”, thereby transferring the larger-scale information to the inner, highest-resolution domain (see Fig.2).
Fig. 2: Multi-scale, nested approach for the Mediterranean region
The objective is to provide a relevant numerical modeling of the aerosols generated at the air-sea interface and their atmospheric dynamics in coastal area at local scale. This will be useful to refine on the one hand, estimates of radiative forcing of aerosols, necessary for the reliability of climate scenarios and secondly to validate a quenching model operating from a reduced number of inputs.
These will consist of easily accessible environmental data (wind speed, air temperature, humidity ...) 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 used in the project, the MEDEX code, but also by a precise description of the environment, will allow the relevant tests needed to improve its performance.
In the end, the response of these aerosols to electromagnetic radiation will be finely studied 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.