Abstract
Abstract. The western Mediterranean atmosphere is impacted by a variety of aerosol sources, producing a complex and variable mixture of natural and anthropogenic particles, with different chemical and physical properties. Satellite sensors provide a useful global coverage of aerosol parameters but through indirect measurements that require careful validation. Here we present the results of a long-term regional scale analysis of the full dataset (March 2005 and October 2013) of POLDER-3/PARASOL ocean operational retrievals of the total, fine, and coarse aerosol optical depth (AOD, AODF, and AODC), Ångström exponent (AE), and the spherical or non-spherical partition of coarse-mode AOD (AODCS and AODCNS), respectively. The evaluation is performed using data from 17 coastal and insular ground-based AERONET sites on one side, and airborne vertical profiles of aerosol extinction and number size distribution obtained by the SAFIRE ATR-42 aircraft operated in the area during summer 2012 and 2013 on the other side. This study provides the first regional evaluation of uncertainties of the POLDER-3 products, and highlights their quality. The POLDER-3 Ångström exponent, representing AOD spectral dependence in link with the aerosol particle size distribution, is biased towards small values. This bias, however, does not prevent using AE for classifying the regional aerosol laden air masses. AODF corresponds to particles smaller than 0.6–0.8 µm in diameter and appears suitable to monitor the aerosol submicron fraction from space. We also provide an original validation of POLDER-3 AODC and its spherical or non-spherical partition, which shows agreement within 25 % with AERONET shape retrievals when the aerosol coarse fraction dominates.
Highlights
IntroductionAerosols include a large variety of particles (mineral dust, sea salt, soot carbon and organic species, sulfates, nitrates, etc.) emitted by natural and anthropogenic sources and different mechanisms (combustion, wind erosion, gas-to-particle conversion, etc.)
Aerosols include a large variety of particles emitted by natural and anthropogenic sources and different mechanisms
We present a first comprehensive qualityassessment study of the advanced dataset provided by the operational ocean retrieval algorithm of the third multi-spectral, multi-directional and polarised POLDER-3 (POLarization and Directionality of the Earth’s Reflectances) radiometer on PARASOL (Polarization & Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar) satellite (Herman et al, 2005; Tanré et al, 2011) over the western Mediterranean basin
Summary
Aerosols include a large variety of particles (mineral dust, sea salt, soot carbon and organic species, sulfates, nitrates, etc.) emitted by natural and anthropogenic sources and different mechanisms (combustion, wind erosion, gas-to-particle conversion, etc.). The apportionment of aerosols to anthropogenic and natural sources is critical to the evaluation of the perturbative forcing of human activities on the Earth radiative budget and the climate (Myhre et al, 2013; Shindell et al, 2013; Kim et al, 2014; Pan et al, 2015). In this general context, the Mediterranean basin is a region of great interest. Submitted to demographic pressure and experiencing bad air quality (Monks et al, 2009; Kovats et al, 2014), the Mediterranean is a high emission and transport region of all kinds of anthropogenic and natural aerosols (e.g. Moulin et al, 1998; Lelieveld et al, 2002; Pace et al, 2005, 2006; Querol et al, 2009; Pey et al, 2013; Becagli et al, 2017), as well as one of the most vulnerable areas to climate change (Giorgi, 2006), with severe future warming leading to a reduction in precipitation and soil moisture, and a significant water stress towards the end of the century (Giorgi and Lionello, 2008; García-Ruiz et al, 2011; Christensen et al, 2013) and likely positive feedbacks on the aerosol load
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