Profiles of cloud condensation nuclei, dust mass concentration, and ice-nucleating-particle-relevant aerosol properties in the Saharan Air Layer over Barbados from polarization lidar and airborne in situ measurements

Abstract

Abstract. The present study aims to evaluate lidar retrievals of cloud-relevant aerosol properties by using polarization lidar and coincident airborne in situ measurements in the Saharan Air Layer (SAL) over the Barbados region. Vertical profiles of the number concentration of cloud condensation nuclei (CCN), large particles (diameter d>500 nm), surface area, mass, and ice-nucleating particle (INP) concentration are derived from the lidar measurements and compared with CCN concentrations and the INP-relevant aerosol properties measured in situ with aircraft. The measurements were performed in the framework of the Saharan Aerosol Long-range Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE) in summer 2013. The CCN number concentrations derived from lidar observations were up to a factor of 2 higher than the ones measured in situ aboard the research aircraft Falcon. Possible reasons for the difference are discussed. The number concentration of particles with a dry radius of more than 250 nm and the surface-area concentration obtained from the lidar observations and used as input for the INP parameterizations agreed well (<30 %–50 % deviation) with the aircraft measurements. In a pronounced lofted dust layer during summer (10 July 2013), the lidar retrieval yielded 100–300 CCN per cubic centimeter at 0.2 % water supersaturation and 10–200 INPs per liter at −25 ∘C. Excellent agreement was also obtained in the comparison of mass concentration profiles. During the SALTRACE winter campaign (March 2014), the dust layer from Africa was mixed with smoke particles which dominated the CCN number concentration. This example highlights the unique lidar potential to separate smoke and dust contributions to the CCN reservoir and thus to identify the sensitive role of smoke in trade wind cumuli developments over the tropical Atlantic during the winter season.

Long-term profiling of aerosol light extinction, particle mass, cloud condensation nuclei, and ice-nucleating particle concentration over Dushanbe, Tajikistan, in Central Asia

“…During the 18-month CADEX campaign, a Polly-type multiwavelength polarization Raman lidar Engelmann et al, 2016;Hofer et al, 2017) was operated in Dushanbe, Tajikistan. The Dushanbe lidar station is part of PollyNET, a network of permanent or campaign-based Polly lidar stations and is the first outpost of the European Aerosol Research Lidar Network (EARLINET) (Pappalardo et al, 2014).…”

“…The Dushanbe lidar station is part of PollyNET, a network of permanent or campaign-based Polly lidar stations and is the first outpost of the European Aerosol Research Lidar Network (EARLINET) (Pappalardo et al, 2014). The polarization Raman lidar permits us to measure height profiles of the particle backscatter coefficient at the laser wavelengths of 355, 532, and 1064 nm; particle extinction coefficients at 355 and 532 nm by means of 387 and 607 nm nitrogen Raman signal profiling; the particle linear depolarization ratio at 355 and 532 nm by means of additional cross-polarized lidar return detection at 355 and 532 nm; and of the water-vapor-to-dry-air mixing ratio by using the Raman lidar return signals at 407 nm (water vapor channel) and 387 nm nitrogen Raman channel (e.g., Mattis et al, 2004;Baars et al, 2012;Engelmann et al, 2016;Hofer et al, 2017;Dai et al, 2018). Technical details of the lidar system are described in Engelmann et al (2016).…”

“…Technical details of the lidar system are described in Engelmann et al (2016). The specifically used Polly, the field site, and the CADEX measurement campaign, including ancillary instrumentation, are described in Hofer et al (2017).…”

“…1). Aerosol pollution and mineral dust are important components in the environmental and atmospheric system in this region, which belongs to the northern hemispheric dust belt extending from the Sahara in northern Africa to the Taklamakan and Gobi deserts in China (Ginoux et al, 2012;Ridley et al, 2016;Hofer et al, 2017). Long-range transport of desert dust from the Sahara and the Middle Eastern deserts and additional local and regional emissions of dust and aerosol pollution (anthropogenic haze, biomass burning smoke) lead to a complex aerosol mixture and complex vertical layering of aerosols in the planetary boundary layer and free troposphere over, for example, Dushanbe in Tajikistan (Hofer et al, 2017).…”

“…The lidar (Polly: POrtabLe Lidar sYstem) Baars et al, 2016) was continuously operated over a 18-month period from March 2015 to August 2016. First results were presented by Hofer et al (2017). Profiles of basic aerosol optical properties and dust mass concentration in combination with vertically resolved dust source identification for representative aerosol scenarios were discussed based on case studies.…”