Spatio-temporal monitoring by ground-based and air- and space-borne lidars of a moderate Saharan dust event affecting southern Europe in June 2013 in the framework of the ADRIMED/ChArMEx campaign

Abstract

International audienceDuring the ADRIMED (Aerosol Direct Radiative Impact on the regional climate in the Mediterranean region) special observation period (SOP-1a), conducted in June 2013 in the framework of the ChArMEx (Chemistry-Aerosol Mediterranean Experiment) project, a moderate Saharan dust event swept the Western and Central Mediterranean Basin (WCMB) from west to east during a 9-day period between 16 and 24 June. This event was monitored from the ground by six EARLINET/ACTRIS (European Aerosol Research Lidar Network/Aerosols, Clouds, and Trace gases Research Infrastructure Network) lidar stations (Granada, Barcelona, Naples, Potenza, Lecce and Serra la Nave) and two ADRIMED/ChArMEx lidar stations specially deployed for the field campaign in Cap d’en Font and Ersa, in Minorca and Corsica Islands, respectively. The first part of the study shows the spatio-temporal monitoring of the dust event during its transport over the WCMB with ground-based lidar and co-located AERONET (Aerosol Robotic Network) Sun-photometer measurements. Dust layer optical depths, Ångström exponents, coarse mode fractions, linear particle depolarization ratios (LPDRs), dust layer heights and the dust radiative forcing estimated in the shortwave (SW) and longwave (LW) spectral ranges at the bottom of the atmosphere (BOA) and at the top of the atmosphere (TOA) with the Global Atmospheric Model (GAME), have been used to characterize the dust event. Peak values of the AERONET aerosol optical depth (AOD) at 440 nm ranged between 0.16 in Potenza and 0.37 in Cap d’en Font. The associated Ångström exponent and coarse mode fraction mean values ranged from 0.43 to 1.26 and from 0.25 to 0.51, respectively. The mineral dust produced a negative SW direct radiative forcing at the BOA ranging from −56.9 to −3.5 W m⁻². The LW radiative forcing at the BOA was positive, ranging between +0.3 and +17.7 W m^-2. The BOA radiative forcing estimates agree with the ones reported in the literature. At the TOA, the SW forcing varied between −34.5 and +7.5 W m⁻². In seven cases, the forcing at the TOA resulted positive because of the aerosol strong absorbing properties (0.83 < single-scattering albedo (SSA) < 0.96). The multi-intrusion aspect of the event is examined by means of air- and space-borne lidar measurements, satellite images and back trajectories. The analysis reported in this paper underline the arrival of a second different intrusion of mineral dust observed over southern Italy at the end of the considered period which probably results in the observed heterogeneity in the dust properties

Response to Anonymous Referee #2

“…Nonetheless, the values obtained for this case are very similar to the regional summer mean value obtained by Papadimas et al, (2012) at the surface (-26.5 W•m -2 ) and the TOA (-6.3 W•m -2 ) and are within the range of previous values observed in the western Mediterranean region for similar values of SZA , which varied from −93.1 to −0.5 W•m −2 at the BOA and -34.5 to +8.5 W•m −2 at the TOA (e.g. Gomez-Amo et al, 2011;Sicard et al, 2014a,b;Barragan et al, 2017).…”

“…Anthropogenic sources such as pollution from Europe, the Iberian Peninsula and the Mediterranean Sea (Pérez-Ramírez et al, 2016) also affect the station. Local sources are mainly road traffic and central heating systems (Titos et al, 2017).…”

Impact of mineral dust on shortwave and longwave radiation: evaluation of different vertically resolved parameterizations in 1-D radiative transfer computations

“…The values of the ARE SW and the FE SW are highly dependent on the SZA and a straightforward comparison with previous studies is not simple. Nonetheless, the values obtained for this case are within the range of previous values observed in the western Mediterranean region for similar values of SZA, e.g., FE between −263.4 and −157.1 W m −2 at the BOA and −23.8 and −86.2 W m −2 for SZA = 60 • or ARE values ranging between −93.1 and −0.5 W m −2 at the BOA and between −34.5 and +8.5 W m −2 at the TOA for different SZA values (e.g., Gómez-Amo et al, 2011;Sicard et al, 2014a, b;Barragan et al, 2017). Table 6.…”

Two-dimensional mineral dust radiative effect calculations from CALIPSO observations over Europe

“…There is a need for ground-based stations to coordinate efforts and establish adequate measurement protocols within scientific networks such as the European Aerosol Research Lidar Network (EARLINET; Pappalardo et al, 2014) in order to provide a more regional coverage, which is crucial for the analysis of mineral dust properties from the ground (Binietoglou et al, 2015;Granados-Muñoz et al, 2016;Sicard et al, 2016a, b;Barragan et al, 2017). Designated aerosol satellite sensors, even though less accurate, are still a key aspect with respect to increasing the temporal and spatial coverage for the study of aerosol properties.…”

“…As a consequence, there is still a gap between the experimental retrieval of the aerosol radiative properties and the modeled estimations used to feed global climate models. The use of satellite measurements such as those performed by CALIPSO provide suitable spatial coverage and temporal resolution that may help to improve the determination of aerosol radiative effects at regional (Huang et al, 2009;Lemaître et al, 2010;Mallet et al, 2016;Bhawar et al, 2016) or global scales (Oikawa et al, 2013(Oikawa et al, , 2018.…”