Abstract. This study proposes an aerosol-type classification based on the particle linear depolarization ratio (PLDR) and single-scattering albedo (SSA) provided in the AErosol RObotic NETwork (AERONET) version 3 level 2.0 inversion product. We compare our aerosol-type classification with an earlier method that uses fine-mode fraction (FMF) and SSA. Our new method allows for a refined classification of mineral dust that occurs as a mixture with other absorbing aerosols: pure dust (PD), dust-dominated mixed plume (DDM), and pollutant-dominated mixed plume (PDM). We test the aerosol classification at AERONET sites in East Asia that are frequently affected by mixtures of Asian dust and biomass-burning smoke or anthropogenic pollution. We find that East Asia is strongly affected by pollution particles with high occurrence frequencies of 50 % to 67 %. The distribution and types of pollution particles vary with location and season. The frequency of PD and dusty aerosol mixture (DDM+PDM) is slightly lower (34 % to 49 %) than pollution-dominated mixtures. Pure dust particles have been detected in only 1 % of observations. This suggests that East Asian dust plumes generally exist in a mixture with pollution aerosols rather than in pure form. In this study, we have also considered data from selected AERONET sites that are representative of anthropogenic pollution, biomass-burning smoke, and mineral dust. We find that average aerosol properties obtained for aerosol types in our PLDR–SSA-based classification agree reasonably well with those obtained at AERONET sites representative for different aerosol types.

Abstract. Knowledge of the particle lidar ratio (Sλ) and the particle linear depolarisation ratio (δλ) for different aerosol types allows for aerosol typing and aerosol-type separation in lidar measurements. Reference values generally originate from dedicated lidar observations but might also be obtained from the inversion of AErosol RObotic NETwork (AERONET) sun/sky radiometer measurements. This study investigates the consistency of spectral Sλ and δλ provided in the recently released AERONET version 3 inversion product for observations of undiluted mineral dust in the vicinity of the following major deserts: Gobi, Sahara, Arabian, Great Basin, and Great Victoria. Pure dust conditions are identified by an Ångström exponent <0.4 and a fine-mode fraction <0.1. The values of spectral Sλ are found to vary for the different source regions but generally show an increase with decreasing wavelength. The feature correlates to AERONET, retrieving an increase in the imaginary part of the refractive index with decreasing wavelength. The smallest values of Sλ=35–45 sr are found for mineral dust from the Great Basin desert, while the highest values of 50–70 sr have been inferred from AERONET observations of Saharan dust. Values of Sλ at 675, 870, and 1020 nm seem to be in reasonable agreement with available lidar observations, while those at 440 nm are up to 10 sr higher than the lidar reference. The spectrum of δλ shows a maximum of 0.26–0.31 at 1020 nm and decreasing values as wavelength decreases. AERONET-derived δλ values at 870 and 1020 nm are in line with the lidar reference, while values of 0.19–0.24 at 440 nm are smaller than the independent lidar observations by a difference of 0.03 to 0.08. This general behaviour is consistent with earlier studies based on AERONET version 2 products.

Abstract. This study focused on the contribution of ammonium nitrate (NH4NO3) to aerosol optical depth (AOD) and direct radiative forcing (DRF) by aerosols over an East Asian domain. In order to evaluate the contribution, chemistry-transport model (CTM)-estimated AOD was combined with satellite-retrieved AOD, utilizing a data assimilation technique, over East Asia for the entire year of 2006. Using the assimilated AOD and CTM-estimated aerosol optical properties, the DRF by aerosols was estimated over East Asia via a radiative transfer model (RTM). Both assimilated AOD and estimated DRF values showed relatively good agreements with AOD and DRF by aerosols from AERONET. Based on these results, the contributions of NH4NO3 to AOD and DRF by aerosols (ΦAOD and ΦDRF) were estimated for the four seasons of 2006 over East Asia. Both ΦAOD and ΦDRF showed seasonal variations over East Asia within the ranges between 4.7% (summer) and 31.3% (winter) and between 4.7% (summer) and 30.7% (winter), respectively, under clear-sky conditions, showing annual average contributions of 15.6% and 15.3%. Under all-sky conditions, ΦDRF varied between 3.6% (summer) and 24.5% (winter), showing annual average contribution of 12.1% over East Asia. These annual average contributions of NH4NO3 to AOD and DRF are almost comparable to the annual average mass fractions of NH4NO3 in PM2.5 and PM10 (17.0% and 14.0%, respectively). ΦAOD and ΦDRF were even larger in the locations where NH3 and NOx emission rates are strong, such as the central East China (CEC) region and Sichuan Basin. For example, under clear-sky conditions, both ΦAOD and ΦDRF over the CEC region range between 6.9% (summer) and 47.9% (winter) and between 6.7% (summer) and 47.5% (winter), respectively. Based on this analysis, it was concluded that both ΦAOD and ΦDRF cannot be ignored in East Asian air quality and radiative forcing studies, particularly during winter.

Abstract. Absorption aerosol optical depth (AAOD) as obtained from sun–sky photometer measurements provides a measure of the light-absorbing properties of the columnar aerosol loading. However, it is not an unambiguous aerosol-type-specific parameter, particularly if several types of absorbing aerosols, for instance black carbon (BC) and mineral dust, are present in a mixed aerosol plume. The contribution of mineral dust to total aerosol light absorption is particularly important at UV wavelengths. In this study we refine a lidar-based technique applied to the separation of dust and non-dust aerosol types for the use with Aerosol Robotic Network (AERONET) direct sun and inversion products. We extend the methodology to retrieve AAOD related to non-dust aerosol (AAODnd) and BC (AAODBC). We test the method at selected AERONET sites that are frequently affected by aerosol plumes that contain a mixture of Saharan or Asian mineral dust and biomass-burning smoke or anthropogenic pollution, respectively. We find that aerosol optical depth (AOD) related to mineral dust as obtained with our methodology is frequently smaller than coarse-mode AOD. This suggests that the latter is not an ideal proxy for estimating the contribution of mineral dust to mixed dust plumes. We present the results of the AAODBC retrieval for the selected AERONET sites and compare them to coincident values provided in the Copernicus Atmosphere Monitoring System aerosol reanalysis. We find that modelled and AERONET AAODBC are most consistent for Asian sites or at Saharan sites with strong local anthropogenic sources.

&lt;p&gt;&lt;strong&gt;Abstract.&lt;/strong&gt; Knowledge of the particle lidar ratio (S&lt;sub&gt;&amp;#955;&lt;/sub&gt;) and the particle linear depolarisation ratio (&amp;#948;&lt;sub&gt;&amp;#955;&lt;/sub&gt;) for different aerosol types allows for aerosol typing and aerosol-type separation in lidar measurements. Reference values generally originate from dedicated lidar observations but might also be obtained from the inversion of AERONET sun/sky radiometer measurements. This study investigates the consistency of spectral S&lt;sub&gt;&amp;#955;&lt;/sub&gt; and &amp;#948;&lt;sub&gt;&amp;#955;&lt;/sub&gt; provided in the recently released AERONET version 3 inversion product for observations of undiluted mineral dust in the vicinity of major deserts: Gobi, Sahara, Arabian, Great Basin and Great Victoria deserts. Pure dust conditions are identified by an &amp;#197;ngst&amp;#246;m exponent &lt;&amp;#8201;0.4 and a fine-mode fraction &lt;&amp;#8201;0.1. &lt;br&gt;&lt;br&gt; The values of spectral S&lt;sub&gt;&amp;#955;&lt;/sub&gt; are found to vary for the different source regions but generally show an increase with decreasing wavelength. The feature correlates to AERONET retrieving an increase in the imaginary part of the refractive index with decreasing wavelength. The smallest values of S&lt;sub&gt;&amp;#955;&lt;/sub&gt;&amp;#8201;=&amp;#8201;35&amp;#8211;45&amp;#8201;sr are found for mineral dust from the Great Basin desert while the highest values of 50&amp;#8211;70&amp;#8201;sr have been inferred from AERONET observations of Saharan dust. Values of S&lt;sub&gt;&amp;#955;&lt;/sub&gt; at 675, 870, and 1020&amp;#8201;nm seem to be in reasonable agreement with available lidar observations while those at 440&amp;#8201;nm are up to 10&amp;#8201;sr higher than the lidar reference. The spectrum of &amp;#948;&lt;sub&gt;&amp;#955;&lt;/sub&gt; shows a maximum of 0.26&amp;#8211;0.31 at 1020&amp;#8201;nm and decreasing values as wavelength decreases. AERONET-derived &amp;#948;&lt;sub&gt;&amp;#955;&lt;/sub&gt; at 870 and 1020&amp;#8201;nm are close to the lidar reference while values of 0.19&amp;#8211;0.24 at 440&amp;#8201;nm are smaller than the independent lidar observations. This general behaviour is consistent with earlier studies based on AERONET version 2 products.&lt;/p&gt;