Retrieval of aerosol properties from ceilometer and photometer measurements: long-term evaluation with in situ data and statistical analysis at Montsec (southern Pyrenees)

Abstract

Abstract. Given the need for accurate knowledge of aerosol microphysical and optical properties with height resolution, various algorithms combining vertically resolved and column-integrated aerosol information have been developed in the last years. Here we present new results of vertically resolved extensive aerosol optical properties (backscattering, scattering and extinction) and volume concentrations retrieved with the GRASP (Generalized Retrieval of Aerosol and Surface Properties) algorithm over a 3-year period. The range-corrected signal (RCS) at 1064 nm measured with a ceilometer and the aerosol optical depth (AOD) and sky radiances from a sun/sky photometer have been used as input for this algorithm. We perform a detailed evaluation of GRASP retrievals with simultaneous in situ measurements performed at the same height, at the Montsec mountaintop observatory (MSA) in the Pre-Pyrenees (northeastern Spain). This is the first long-term evaluation of various outputs of this algorithm; previous evaluations focused only on the study of aerosol volume concentration for short-term periods. In general, our results show good agreement between techniques although GRASP inversions yield higher values than those measured in situ. The statistical analysis of the extinction coefficient vertical profiles shows a clear seasonality as well as significant differences depending on the air mass origin. The observed seasonal cycle is mainly modulated by a higher development of the atmospheric boundary layer (ABL) during warm months, which favors the transport of pollutants to MSA, and higher influence of regional and North African episodes. On the other hand, in winter, MSA is frequently influenced by free-troposphere conditions and venting periods and therefore lower extinction coefficients that markedly decrease with height. This study shows the potentiality of implementing GRASP in ceilometer and lidar networks for obtaining aerosol optical properties and volume concentrations at multiple sites, which will definitely contribute to enhancing the representativeness of the aerosol vertical distribution as well as to providing useful information for satellite and global model evaluation.

Overview of the SLOPE I and II campaigns: aerosol properties retrieved with lidar and sun–sky photometer measurements

“…This GRASP configuration is described in detail in Benavent-Oltra et al (2019). The data used in this study were recorded between May and July of 2016 and 2017 with 286 retrievals in 69 d that passed the filter imposed to the inversion process (relative residual < 15 %; Torres et al, 2017).…”

“…It should be noted here that GARRLiC is a branch of GRASP. The versatility of GRASP allows the retrieval of aerosol vertical and surface properties combining different types of measurements, such as sun photometers, lidar, ceilometers, satellite, sky cameras, and nephelometers (e. g. Lopatin et al, 2013;Espinosa et al, 2017;Román et al, 2017;Torres et al, 2017;Titos et al, 2019, Herreras et al, 2019Dubovik et al, 2019). The aerosol properties retrieved by GRASP have been evaluated in previous works using the volume concentration provided by the LIRIC algorithm (differences ∼ 20 %; as reference and the backscatter and extinction coefficients calculated with Klett-Fernald and Raman methods (differences below 30 %; Tsekeri et al, 2017).…”

“…This is the first longterm evaluation of GRASP that combines sun-sky photometer and multi-wavelength lidar measurements to retrieve profiles of aerosol intensive properties separately for both fine and coarse modes instead of only one mode such as when using ceilometer measurements (e.g. Román et al, 2018;Titos et al, 2019). In addition, a statistical analysis of both to-tal column and vertically resolved aerosol properties is performed, and two extreme events of desert dust and biomass burning are evaluated.…”

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

“…GRASP first demonstrated its overall capability in an aerosol retrieval test study (Kokhanovsky et al, 2010). It has gone on to prove itself in a variety of real-world applications (Chen et al, 2018(Chen et al, , 2019Frouin et al, 2019;Li et al, 2019;Schuster et al, 2019;Torres et al, 2017). GRASP has been successfully applied to measurements from many different types of instruments (Benavent-Oltra et al, 2019;Espinosa et al, 2017Espinosa et al, , 2018Román et al, 2018;Titos et al, 2019;Torres et al, 2017), but the most pertinent to AirHARP are the previous applications of GRASP to POLDER-3 on PARASOL (Chen et al, 2018(Chen et al, , 2019Dubovik et al, 2011;Frouin et al, 2019;Li et al, 2019) because of its familiar polarization, multi-wavelength, and multi-angle sampling characteristics.…”

An experimental study on light scattering matrices for Chinese loess dust with different particle size distributions

“…During aerosol characterization experiments (ACE-Asia), mass balance calculations indicated that 45 %-82 % of atmospheric aerosol mass at observation sites in China was attributed to Asian dust (Zhang et al, 2003). The Chinese Loess Plateau (CLP) is usually considered one of the main sources or an important supply site of Asian dust aerosol (Han et al, 2008;Shen et al, 2016;Tsai et al, 2014;Zhang et al, 2010). Statistical analysis of dust storms influencing the Chinese mainland from 2000 to 2002 showed that about a quarter of dust storms originated from the CLP (Zhang and Gao, 2007).…”