Abstract. Aerosol-Cloud interactions (ACI) result in the largest uncertainties in the global radiation budget so far. To improve the current consideration of ACI in global circulation models, it is necessary to characterize the 3-D distribution of dust-related Cloud Condensation Nuclei Concentration (CCNC) and Ice Nucleating Particle Concentration (INPC) globally. This can potentially be realized using the POLIPHON (POlarization LIdar PHOtometer Networking) method together with spaceborne lidar observations. However, dust-related conversion factors to convert bulk aerosol optical properties from lidar measurements to aerosol microphysical properties, are still less constrained in many regions, which limits the applications of POLIPHON method. Here we retrieve the essential dust-related conversion factors at the remote oceanic/coast sites using the historical AERONET (AErosol RObotic NETwork) databases. Depolarization-ratio-based dust ratios Rd at 1020 nm are applied to identify the dust-occurring cases so that it can be possible to contain fine-mode dust dominated cases (after the preferential removal of large-size dust particles during transport), study the evolution of dust microphysical properties along the transoceanic pathway, and mitigate occasional interference of large-size marine aerosols. The newly proposed scheme is proven to be valid and feasible by intercomparisons with previous studies at nine sites in/near the deserts. The dust-related conversion factors are calculated at 20 oceanic/coast sites using both PD (pure dust) and PD+DDM (dust-dominated mixture) datasets. At nearly half sites, the conversion factors are solely calculated using the PD data sets; while at the rest sites, the participation of DDM datasets is required to ensure enough data points in the calculation. Evident variation trends in conversion factors are found for cv,d (extinction-to-volume, gradually decrease), c250,d (extinction-to-particle (with radius >250 nm) number concentration, gradually increase) and cs,d (extinction-to-surface area concentration, plunge of decrease) along both the transpacific and transatlantic dust transport pathways. The retrieved dust-related conversion factors are anticipated in inversing 3-D dust-related CCNC and INPC distribution globally to improve the understanding of ACI in atmospheric circulation models.

<p>The Raikoke volcano erupted on 21-22 June 2019 and emitted ~1.5 Tg volcanic ash into the atmosphere. Several previous studies have focused on the large-scale dispersion of volcanic aerosol plumes with space-borne observations and dispersion models. However, height-resolved ground-based observations are still necessary to trace and cross-check the 3-D evolution of aerosol plumes due to their complicated structures. Here, we present a rare ground-based lidar observation of Raikoke aerosol plumes in the mid-latitudes of the Northern Hemisphere (site: Wuhan; location: 30.5°N, 114.4°E) from 25 July to 30 September 2019. Two types of volcanic aerosol plumes were observed, including the main aerosol plume and a single impacted aerosol cloud (referred to as ‘CCC’, or coherent circular clouds). The main aerosol plume first arrived at Wuhan on 25 July and was intermittently observed during the following two months at altitudes of 15.0-20.5 km, with layer-integrated AODs (aerosol optical depths) of 0.001-0.017. From 22 August to 23 September, this aerosol plume underwent two quasi-elliptical transport pathways in East Asia driven by an Asian monsoon anticyclone. The CCC arrived at Wuhan twice at 20.2-21.7 km on 30 July and at 23.2-25.0 km on 24-26 August after self-lofting, corresponding to the former two circles of their transport around the Northern Hemisphere. Both arrivals of the CCC were closely followed by a thin and horizontally extended aerosol plume (named ‘trail’) with a duration of several days. The unique observation location provided us with an opportunity to study the evolution of the vertical distribution and optical properties of volcanic aerosols, which is anticipated to be a crucial supplement/reference for dispersion model simulation, data assimilation, and forecasting refinement.</p>

Abstract. Aerosol–cloud interactions (ACIs) are the largest contributor to the uncertainty in the global radiation budget. To improve the current consideration of ACIs in global circulation models, it is necessary to characterize the 3-D distribution of dust-related cloud condensation nuclei concentration (CCNC) and ice-nucleating particle concentration (INPC) globally. This can potentially be realized using the POlarization LIdar PHOtometer Networking (POLIPHON) method together with spaceborne lidar observations. However, dust-related conversion factors that convert bulk aerosol optical properties from lidar measurements to aerosol microphysical properties are still less constrained in many regions, which limits the applications of the POLIPHON method. Here we retrieve the essential dust-related conversion factors at remote oceanic and coastal sites using the historical AErosol RObotic NETwork (AERONET) database. Depolarization-ratio-based dust ratios Rd at 1020 nm are applied to identify the dust-occurring cases, thus enabling us to contain fine-mode dust-dominated cases (after the preferential removal of large-sized dust particles during transport), study the evolution of dust microphysical properties along the transoceanic pathway, and mitigate occasional interference of large-sized marine aerosols. The newly proposed scheme is proven to be valid and feasible by intercomparisons with previous studies at nine sites in/near deserts. The dust-related conversion factors are calculated at 20 oceanic and coastal sites using both pure dust (PD) and PD plus dust-dominated mixture (PD+DDM) datasets. At nearly half of the sites, the conversion factors are solely calculated using the PD datasets, while at the remaining sites, the participation of DDM datasets is required to ensure a sufficient number of data for the calculation. Evident variation trends in conversion factors are found for cv,d (extinction-to-volume concentration, gradually decreasing), c250,d (extinction-to-particle (with a radius > 250 nm) number concentration, gradually increasing), and cs,d (extinction-to-surface-area concentration, gradually decreasing) along both the transpacific and transatlantic dust transport pathways. The retrieved dust-related conversion factors are anticipated to inverse 3-D dust-related CCNC and INPC distributions globally, thereby improving the understanding of ACIs in atmospheric circulation models.

No abstract