UTLS wildfire smoke over the North Pole region, Arctic haze, and aerosol-cloud interaction during MOSAiC 2019/20: An introductory

Abstract

Abstract. An advanced multiwavelength polarization Raman lidar was operated aboard the icebreaker Polarstern during the MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) expedition, lasting from September 2019 to October 2020, to contiuously monitor aerosol and cloud layers in the Central Arctic up to 30 km height at latitudes mostly between 85° N and 88.5° N. The lidar was integrated in a complex remote sensing infrastructure aboard Polarstern. Modern aerosol lidar methods and new lidar techniques and concepts to explore aerosol-cloud interaction were applied for the first time in the Central Arctic. Aim of the introductory article is to provide an overview of the observational spectrum of the lidar products for representative measurement cases. Highlight of the lidar measurements was the detection of a 10 km deep wildfire smoke layer over the North Pole area from, on average, 7 km to 17 km height with an aerosol optical thickness (AOT) at 532 nm around 0.1 (in October–November 2019) and 0.05 from December to mid of March 2020. The wildfire smoke was trapped within the extraordinarily strong polar vortex and remained detectable until the beginning of May 2020. Arctic haze was also monitored and characterized in terms of backscatter, extinction, and extinction-to-backscatter ratio at 355 and 532 nm. High lidar ratios from 60–100 sr in lofted mixed haze and smoke plumes are indicative for the presence of strongly light-absorbing fine-mode particles. The AOT at 532 nm was of the order of 0.025 for the tropospheric haze layers. In addition, so-called cloud closure experiments were applied to Arctic mixed-phase cloud and cirrus observations. The good match between cloud condensation nucleus concentration (CCNC) and cloud droplet number concentration (CDNC) and, on the other hand, between ice-nucleating particle concentration (INPC) and ice crystal number concentration (ICNC) indicated a clear influence of aerosol particles on the evolution of the cloud systems. CDNC was mostly between 20 and 100 cm−3 in the liquid-water dominated cloud top layer. ICNC was of the order of 0.1–1 L−1. The study of the impact of wildfire smoke particles on cirrus formation revealed that heterogeneous ice formation with smoke particles (organic aerosol particles) as INPs may have prevailed. ICNC values of 10–40 L−1 were clearly below ICNC levels that would indicate homogeneous freezing.

Tropospheric and stratospheric wildfire smoke profiling with lidar: mass, surface area, CCN, and INP retrieval

“…In the upcoming years, strong field activities are required, including comparisons of airborne in situ with lidar observations of smoke INP concentrations as successfully performed in the case of Saharan dust (Schrod et al, 2017;Marinou et al, 2019) and so-called cirrus closure experiments as realized in the case of cirrus formation in pronounced Saharan dust layers (Ansmann et al, 2019b) in order to check the applicability of developed smoke INP parameterizations and to quantify the uncertainties in the INP estimates under real-world meteorological, cloud, and aerosol conditions. A first closure study with respect to smoke-cirrus interaction was recently presented by Engelmann et al (2020).…”

“…The AERONET smoke studies are supplemented by multiwavelength lidar observations of smoke conversion parameters. These vertically resolved observations were performed at Punta Arenas, Chile (Ohneiser et al, 2020); Manaus, Brazil (Baars et al, 2012); near Washington, DC (Veselovskii et al, 2015); at Cabo Verde; in the outflow regime of central western African smoke (Tesche et al, 2011), at Leipzig and Lindenberg, Germany (Wandinger et al, 2002;Haarig et al, 2018); and on the German icebreaker Polarstern drifting through the high Arctic close to the North Pole during the winter half year of 2019-2020 (Engelmann et al, 2020;Ohneiser et al, 2021). The lidar results are shown in Sect.…”

First triple-wavelength lidar observations of depolarization and extinction-to-backscatter ratios of Saharan dust

“…The Arielle lidar was operated several meters apart from the BERTHA instrument. The Arielle lidar has been recently deployed on the research vessel Polarstern in the central Arctic (Engelmann et al, 2020).…”