Long-term deposition and condensation ice-nucleating particle measurements from four stations across the globe

Abstract

Abstract. Ice particle activation and evolution have important atmospheric implications for cloud formation, initiation of precipitation and radiative interactions. The initial formation of atmospheric ice by heterogeneous ice nucleation requires the presence of a nucleating seed, an ice-nucleating particle (INP), to facilitate its first emergence. Unfortunately, only a few long-term measurements of INPs exist, and as a result, knowledge about geographic and seasonal variations of INP concentrations is sparse. Here we present data from nearly 2 years of INP measurements from four stations in different regions of the world: the Amazon (Brazil), the Caribbean (Martinique), central Europe (Germany) and the Arctic (Svalbard). The sites feature diverse geographical climates and ecosystems that are associated with dissimilar transport patterns, aerosol characteristics and levels of anthropogenic impact (ranging from near pristine to mostly rural). Interestingly, observed INP concentrations, which represent measurements in the deposition and condensation freezing modes, do not differ greatly from site to site but usually fall well within the same order of magnitude. Moreover, short-term variability overwhelms all long-term trends and/or seasonality in the INP concentration at all locations. An analysis of the frequency distributions of INP concentrations suggests that INPs tend to be well mixed and reflective of large-scale air mass movements. No universal physical or chemical parameter could be identified to be a causal link driving INP climatology, highlighting the complex nature of the ice nucleation process. Amazonian INP concentrations were mostly unaffected by the biomass burning season, even though aerosol concentrations increase by a factor of 10 from the wet to dry season. Caribbean INPs were positively correlated to parameters related to transported mineral dust, which is known to increase during the Northern Hemisphere summer. A wind sector analysis revealed the absence of an anthropogenic impact on average INP concentrations at the site in central Europe. Likewise, no Arctic haze influence was observed on INPs at the Arctic site, where low concentrations were generally measured. We consider the collected data to be a unique resource for the community that illustrates some of the challenges and knowledge gaps of the field in general, while specifically highlighting the need for more long-term observations of INPs worldwide.

Bioaerosols in the Amazon rain forest: temporal variations and vertical profiles of Eukarya, Bacteria, and Archaea

“…For instance, the measured N BAC values fall within the estimated range of bacterial cell concentrations for forest ecosystems (i.e., 3.3-8.8 × 10 4 m −3 ) according to Burrows et al (2009a). Furthermore, a predominance of Eukaryotes in the Amazon was shown by Souza et al (2019) and Elbert et al (2007), which is consistent with our results. Of further atmospheric relevance is the number concentration of all airborne cells that were determined by staining the intracellular DNA with the fluorescent dye DAPI 1 (N DAPI ).…”

“…The genome sizes were determined as follows. Souza et al (2019) found Proteobacteria and Actinobacteria to be the dominant phyla within the airborne Amazonian bacterial population. The median genome sizes found in the National Center for Biotechnology Information (NCBI) database were ∼ 4.8 and ∼ 4.3 Mb for Proteobacteria and Actinobacteria, respectively (https://www.ncbi.nlm.nih.…”

The contribution of Saharan dust to the ice nucleating particle concentrations at the High Altitude Station Jungfraujoch (3580 m a.s.l.), Switzerland

“…SDE tracers, this is specially relevant for sites where the presence of dust events is inferred from the α SSA alone, as has been done in previous studies at the JFJ (Chou et al, 2011;Boose et al, 2016a;Lacher et al, 2018a). INP concentrations shows a leptokurtic log-normal distribution, which is consistent with the theory by Ott (1990) and other studies (e.g., Welti et al, 2018;Schrod et al, 2020 Since SDEs consist only of the high concentration tail of the log-normal distribution of dust in the atmosphere after successive random dilution by large and small scale dynamics, also visible in the dust CAMS frequency distribution in Figure 6b, it is likely that ice-active dust is also present outside of SDE periods, however in smaller concentrations. For the following assessment, we assume that a constant mass-fraction of all dust carried to the JFJ will act as INPs.…”

“…To capture and study this effect, design adaptations need to be implemented in our sampling equipment in upcoming studies, as the pore ice sublimates or melts in the heated and dried sampling lines upstream of the INP counter used here. studies (e.g., Welti et al, 2018;Schrod et al, 2020). We found dust to be the main contributor to the INP population at 243.15 K and S w = 1.04 at the JFJ, with 74.7 ± 0.2% of all INPs observed during SDEs.…”

Occurrence and growth of sub-50 nm aerosol particles in the Amazonian boundary layer

“…At the ATTO site, the first aerosol measurements were initiated in 2011 (e.g., Pöhlker et al, 2012;Saturno et al, 2018b). Since 2014, multiple continuous measurements of physical and chemical particle properties have been established and gradually extended (e.g., Pöhlker et al, 2016Pöhlker et al, , 2018Holanda et al, 2020;Saturno et al, 2018a;Schrod et al, 2020).…”