Different strategies to retrieve aerosol properties at night-time with the GRASP algorithm

Abstract

Abstract. This study evaluates the potential of the GRASP algorithm (Generalized Retrieval of Aerosol and Surface Properties) to retrieve continuous day-to-night aerosol properties, both column-integrated and vertically resolved. The study is focused on the evaluation of GRASP retrievals during an intense Saharan dust event that occurred during the Sierra Nevada Lidar aerOsol Profiling Experiment I (SLOPE I) field campaign. For daytime aerosol retrievals, we combined the measurements of the ground-based lidar from EARLINET (European Aerosol Research Lidar Network) station and sun–sky photometer from AERONET (Aerosol Robotic Network), both instruments co-located in Granada (Spain). However, for night-time retrievals three different combinations of active and passive remote-sensing measurements are proposed. The first scheme (N0) uses lidar night-time measurements in combination with the interpolation of sun–sky daytime measurements. The other two schemes combine lidar night-time measurements with night-time aerosol optical depth obtained by lunar photometry either using intensive properties of the aerosol retrieved during sun–sky daytime measurements (N1) or using the Moon aureole radiance obtained by sky camera images (N2). Evaluations of the columnar aerosol properties retrieved by GRASP are done versus standard AERONET retrievals. The coherence of day-to-night evolutions of the different aerosol properties retrieved by GRASP is also studied. The extinction coefficient vertical profiles retrieved by GRASP are compared with the profiles calculated by the Raman technique at night-time with differences below 30 % for all schemes at 355, 532 and 1064 nm. Finally, the volume concentration and scattering coefficient retrieved by GRASP at 2500 m a.s.l. are evaluated by in situ measurements at this height at Sierra Nevada Station. The differences between GRASP and in situ measurements are similar for the different schemes, with differences below 30 % for both volume concentration and scattering coefficient. In general, for the scattering coefficient, the GRASP N0 and N1 show better results than the GRASP N2 schemes, while for volume concentration, GRASP N2 shows the lowest differences against in situ measurements (around 10 %) for high aerosol optical depth values.

New particle formation at urban and high-altitude remote sites in the south-eastern Iberian Peninsula

“…Due to its proximity to the African continent, Granada region is frequently affected by Saharan dust intrusions, especially in summer (Mandija et al, 2017;Valenzuela et al, 2015). These African dust intrusions usually transport large mineral dust loads to our study area (e.g., Benavent-Oltra et al, 2019;Lyamani et al, 2006). During the analysed period, there was an intrusion of Saharan dust over the region of study from 24 to 27 June, as confirmed by CALIMA warning system (www.calima.ws; Fig.…”

Interaction of Dust Aerosols with Land/Sea Breezes over the Eastern Coast of the Red Sea from LIDAR Data and High-resolution WRF-Chem Simulations

“…A study that compared the GRASP retrieval scheme employed here against in situ measurements showed that the differences were less than 30 % for the different retrieval schemes (Benavent-Oltra et al, 2019).…”

“…For example, in this study, the implemented retrieval allows us to observe the variability of columnar properties during the night. In contrast, in similar retrieval realized by Benavent-Oltra et al (2019), any variability of columnar properties through the night was not considered.…”

Retrieval of aerosol properties from Airborne Hyper-Angular Rainbow Polarimeter (AirHARP) observations during ACEPOL 2017

“…The last few decades have seen unprecedented efforts to better characterize aerosol particle properties and aerosol radiative effects with in situ and remote sensing observations. For example, in situ measurements based on a wide variety of techniques, such as photoacoustic and cavity ring-down spectrometers, filter-based photometers, and polarized imaging nephelometers, have provided detailed information on size, shape, and absorption for many different regions across the world and continue to do so (Bergstrom et al, 2007;Bond et al, 1999;Dubovik et al, 2000;Espinosa et al, 2017Espinosa et al, , 2018Moosmüller et al, 2005;Petzold et al, 2005;Rocha-Lima et al, 2014;Snider et al, 2015). However, in situ measurements have limitations due to the small sampling volumes that they represent and are very limited in number and spatial coverage.…”