Overview of the Chemistry-Aerosol Mediterranean Experiment/Aerosol Direct Radiative Forcing on the Mediterranean Climate (ChArMEx/ADRIMED) summer 2013 campaign

Abstract

Abstract. The Chemistry-Aerosol Mediterranean Experiment (ChArMEx; http://charmex.lsce.ipsl.fr) is a collaborative research program federating international activities to investigate Mediterranean regional chemistry-climate interactions. A special observing period (SOP-1a) including intensive airborne measurements was performed in the framework of the Aerosol Direct Radiative Forcing on the Mediterranean Climate (ADRIMED) project during the Mediterranean dry season over the western and central Mediterranean basins, with a focus on aerosol-radiation measurements and their modeling. The SOP-1a took place from 11 June to 5 July 2013. Airborne measurements were made by both the ATR-42 and F-20 French research aircraft operated from Sardinia (Italy) and instrumented for in situ and remote-sensing measurements, respectively, and by sounding and drifting balloons, launched in Minorca. The experimental set-up also involved several ground-based measurement sites on islands including two ground-based reference stations in Corsica and Lampedusa and secondary monitoring sites in Minorca and Sicily. Additional measurements including lidar profiling were also performed on alert during aircraft operations at EARLINET/ACTRIS stations at Granada and Barcelona in Spain, and in southern Italy. Remote sensing aerosol products from satellites (MSG/SEVIRI, MODIS) and from the AERONET/PHOTONS network were also used. Dedicated meso-scale and regional modelling experiments were performed in relation to this observational effort. We provide here an overview of the different surface and aircraft observations deployed during the ChArMEx/ADRIMED period and of associated modeling studies together with an analysis of the synoptic conditions that determined the aerosol emission and transport. Meteorological conditions observed during this campaign (moderate temperatures and southern flows) were not favorable to produce high level of atmospheric pollutants nor intense biomass burning events in the region. However, numerous mineral dust plumes were observed during the campaign with main sources located in Morocco, Algeria and Tunisia, leading to aerosol optical depth (AOD) values ranging between 0.2 to 0.6 (at 440 nm) over the western and central Mediterranean basins. Associated aerosol extinction values measured on-board the ATR-42 within the dust plume show local maxima reaching up to 150 Mm−1. Non negligible aerosol extinction (about 50 Mm−1) was also been observed within the Marine Boundary Layer (MBL). By combining ATR-42 extinction, absorption and scattering measurements, a complete optical closure has been made revealing excellent agreement with estimated optical properties. Associated calculations of the dust single scattering albedo (SSA) have been conducted, which show a moderate variability (from 0.90 to 1.00 at 530 nm). In parallel, active remote-sensing observations from the surface and onboard the F-20 aircraft suggest a complex vertical structure of particles and distinct aerosol layers with sea-salt and pollution located within the MBL, and mineral dust and/or aged north American smoke particles located above (up to 6–7 km in altitude). Aircraft and balloon-borne observations show particle size distributions characterized by large aerosols (> 10 μm in diameter) within dust plumes. In terms of shortwave (SW) direct forcing, in-situ surface and aircraft observations have been merged and used as inputs in 1-D radiative transfer codes for calculating the direct radiative forcing (DRF). Results show significant surface SW instantaneous forcing (up to −90 W m−2 at noon). Associated 3-D modeling studies from regional climate (RCM) and chemistry transport (CTM) models indicate a relatively good agreement for simulated AOD compared with measurements/observations from the AERONET/PHOTONS network and satellite data, especially for long-range dust transport. Calculations of the 3-D SW (clear-sky) surface DRF indicate an average of about −10 to −20 W m−2 (for the whole period) over the Mediterranean Sea together with maxima (−50 W m−2) over northern Africa. The top of the atmosphere (TOA) DRF is shown to be highly variable within the domain, due to moderate absorbing properties of dust and changes in the surface albedo. Indeed, 3-D simulations indicate negative forcing over the Mediterranean Sea and Europe and positive forcing over northern Africa.

Contribution of EARLINET/ACTRIS to the summer 2013 Special Observing Period of the ChArMEx project: monitoring of a Saharan dust event over the western and central Mediterranean

“…Sounding/drifting balloons equipped with an ozone sonde and/or an optical particle counter were launched from Minorca. More details about the campaign can be found in Mallet et al (2016).…”

“…Most global and regional climate simulations have investigated the impact of global warming on the Mediterranean climate without detailed considerations on the possible radiative influence of the different Mediterranean aerosols. However such aerosols have a non-negligible surface, top of the atmosphere (TOA) and atmospheric radiative forcing in that region (Mallet et al 2016). …”

Interactions aérosols-rayonnement-climat en région méditerranéenne : Impact de l'effet radiatif direct sur le cycle de l'eau

“…Enfin, des mesures de flux descendants (direct et diffus) dans le spectre visible et proche infrarouge ont été effectuées sur les deux stations. L'instrumentation complète utilisée pour la campagne est détaillée dans Mallet et al (2015). (0,1 km -1 ) pour les couches atmosphé-riques chargées en poussières miné-rales.…”

Summertime surface PM<sub>1</sub> aerosol composition and size by source region at the Lampedusa island in the central Mediterranean Sea

“…The Chemistry-Aerosol Mediterranean Experiment (ChArMEx) collaborative research program, and the Aerosol Direct Radiative Impact on the regional climate in the MEDiterranean region (ADRIMED) project within, were undertaken to investigate the chemistry and climate interactions within the Mediterranean (Mallet et al, 2016). From 11 June until 5 July 2013, numerous experimental setups were deployed across the western and central Mediterranean in what is called the "Special Observation Period -1a" (SOP-1a), including intensive airborne measurements (Denjean et al, 2016).…”

“…From 11 June until 5 July 2013, numerous experimental setups were deployed across the western and central Mediterranean in what is called the "Special Observation Period -1a" (SOP-1a), including intensive airborne measurements (Denjean et al, 2016). Two super-sites were setup at Ersa (at the northern tip of Corsica Island, France) and at the Lampedusa Island (Italy), approximately 1000 km apart on a north-to-south axis in order to characterise surface aerosol chemical, physical and optical properties (Mallet et al, 2016). Numerous secondary sites were established along the Mediterranean coasts in Spain, Italy and Corsica beyond the SOP-1a have also provided valuable knowledge of the atmospheric composition in the western and central Mediterranean regions (Chrit et al, 2017;Chrit et al, 2018;Becagli et al, 2017).…”