Aix‐Marseille Carbon Pilot Study (AMC)

We propose to conduct a first pilot study based on a CO2 atmospheric approach. We will develop a mesoscale modelling framework to simulate the transport of atmospheric CO2 and pollutants that will be assessed against the existing datasets and AIRPACA modelled outputs. The CO2 time series collected at the OHP and Cinq Avenues sites will be analysed at the diurnal, synoptic and seasonal scales to understand the representativeness of these sites. Within an intensive campaign of 3 months, the regional CO2 network will be completed by setting‐up a CO2 analyzer at Frioul, in order to test the representativeness of this site as a coastal background and its ability to catch the urban plume. During this time, AIRPACA will move its CO2 analyser together with an O3 sensor from the Cinq Avenues site to the CLIMED one. This design will ensure the collection of in‐situ CO2 in coastal, periurban and rural sites of the PACA region on a N‐NE/S‐SW transect, and the quantification of the urban plume, which variability will be assessed at the diurnal and synoptic scales. The simultaneous observation of CO2 and O3 at CLIMED and OHP/O3HP will come on top of NEE flux measurements, allowing a first study of the impact of the urban plume on biospheric ecosystems in periurban and rural environments. The collection of pH and alkalinity together with CO2 at the Frioul site will allow, through the data analysis and modelling of a new carbonate chemistry module, the assessment of the impact of the urban plume on marine ecosystems. Additionnal 14CO2 and co‐emitted species measurements will help inferring the partitioning between fossil fuel CO2 emissions and biospheric fluxes, providing an additional assessment of the AIRPACA emission inventory.

This project aims at settling the basement for a long‐term Carbon Observatory that will rely on a denser in‐situ CO2 network, a regular 14CO2 program, Lidar observations of the urban boundary layer in the context of the urban heat island and specific meteorology of the coastal area, an operational atmospheric transport modelling framework, but also on the study of carbonaceous aerosols and other greenhouse gases such as CH4. On the long‐term, a close collaboration with socio‐economists researchers as well as societal and political institutions will also be developed, to ensure a fully integrated program that will bridge the gap between research, society and politics, and federate all the resources and knowledge existing in the different communities. 

This project will aim at the following objectives :

Obj.1‐ To assess the representativeness of the new in‐situ CO2 stations of the PACA region.

Obj.2‐ To develop a mesoscale transport modeling framework of atmospheric CO2 (and pollutants) for the PACA region, useful both for societal actors such as AIRPACA and for our research community.

Obj.3‐ To explore the intensity and variability of the urban plume emitted by the Marseille area in function of the day, of the time of the day and of synoptic conditions.

Obj.4‐ To define the atmospheric CO2 gradients upwind and downwind of the Marseille city in a marine, peri‐urban and a rural station.

Obj.5‐ To assess if the CO2 and O3 plume emitted from the Marseille city impacts the NEE flux on the peri‐urban and rural ecosystems at CLIMED and O3HP stations.

Obj.6‐ To develop a regional marine carbonate chemistry model on the coastal Mediterranean Sea area of PACA.

Obj.7‐ To assess the link between the variability of atmospheric CO2, pH and alkalinity in the coastal area of Marseille, and assess if the CO2 urban plume impacts these parameters.

Obj. 8‐ To setup discrete sampling and in situ high frequency instrumentation dedicated to the carbonate chemistry in the Bay of Marseille