On the radiative impact of aerosols on photolysis rates: comparison of simulations and observations in the Lampedusa island during the ChArMEx/ADRIMED campaign

Abstract

Abstract. The Mediterranean basin is characterized by large concentrations of aerosols from both natural and anthropogenic sources. These aerosols change the optical properties of the atmosphere, therefore affecting tropospheric photochemistry through the photolytic rates. Two simulations of the atmospheric composition at basin-scale have been performed with the CHIMERE chemistry-transport model for the period from 1 June to 15 July 2013 covered by the ADRIMED campaign, a campaign of intense measurements in the western Mediterranean basin. One simulation takes into account the radiative effect of the aerosols on photochemistry, the other one does not. These simulations are compared to satellite and ground-based measurements, with a particular focus on the area of Lampedusa. Values of the Aerosol Optical Depth (AOD) are obtained from the MODIS instrument on the AQUA and TERRA satellites as well as from stations in the AERONET network and from the MFRSR sun photometer deployed at Lampedusa. Additional measurements from instruments deployed at Lampedusa either permanently or exceptionnally are used for other variables: MFRSR sun photometer for AOD, diode array spectrometer for actinic fluxes, LIDAR for the aerosol backscatter, sequential sampler for speciation of aerosol and Brewer spectrophotometer for the total ozone column. It is shown that CHIMERE has a significant ability to reproduce observed peaks in the AOD, which in Lampedusa are mainly due to dust outbreaks during the ADRIMED period, and that taking into account the radiative effect of the aerosols in CHIMERE improves considerably the ability of the model to reproduce the observed day-to-day variations of J(O1D) and J(NO2). While in the case of J(O1D) other variation factors such as the stratospheric ozone column are very important in representing correctly the day-to-day variations, the day-to-day variations of J(NO2) are captured almost completely by the model when the optical effects of the aerosols are taken into account. Finally, it is shown that the inclusion of the direct radiative effect of the aerosols in the CHIMERE model leads to reduced J(O1D) and J(NO2) values over all the simulation domain, which ranges from a few percents over continental Europe and the northeast Atlantic Ocean to about 20% close to and downwind from saharan dust sources. The effect on the modelled ozone concentration is twofold, with the effect of aerosols leading to reduced ozone concentrations over the Mediterranean Sea and continental Europe, close to the sources of NOx, and on the contrary to increased ozone concentrations over remote areas such the Sahara and the tropical Atlantic Ocean.

Impacts of aerosol-radiation feedback on local air quality during a severe haze episode in Nanjing megacity, eastern China

“…11) finds that this haze event produces evident impacts on J [NO2] and J [O(1D)] profiles. The simulated aerosol impacts on photolysis frequencies are in accordance with Mailler et al (2016). The radiation feedback by anthropogenic haze aerosols inhibits the NO 2 photolysis frequency by −2.5% at the ground, whereas accelerates it by 3.2% in the boundary layer (Fig.…”

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

“…Local studies previously mentioned Saha et al, 2008;Pace et al, 2005;Péré et al, 2011;Meloni et al, 2015) clearly report significant SW heating rate due to absorbing particles with values reaching up to 2-3 K per day, depending on the aerosol types. Finally, aerosols also have a significant effect on photolysis rates that may affect tropospheric chemistry and ozone production over the basin (Casasanta et al, 2011;Mailler et al, 2015).…”

Ozone and aerosol tropospheric concentrations variability analyzed using the ADRIMED measurements and the WRF and CHIMERE models

“…Many experimental research programs were recently conducted to characterize the aerosol properties using surface measurements (Querol et al, 2009), airborne measurements (Dulac and Chazette, 2003), optical depths measured by sunphotometers (Kubilay et al, 2003), lidar measurements including EARLINET (European Aerosol Research LIdar Network to Establish an Aerosol Climatology; Papayannis et al, 2008;Pappalardo et al, 2014) or satellite data (Barnaba and Gobbi, 2004). Remotely sensed surface measurements are also used to better quantify the dust optical properties and direct radiative forcing as in Bergamo et al (2008), Basart et al (2009), Mallet et al (2013), and di Sarra et al (2008). The integrated project EUCAARI (dedicated to the Aerosol Climate Air Quality Interactions; Kulmala et al, 2011) was conducted to better characterize the aerosol life cycle and composition in Europe, integrating many types of aerosol studies, from the nano to the global scales, with a large scientific community.…”