Predicting atmospheric background number concentration of ice-nucleating particles in the Arctic

Abstract

Abstract. Mixed-phase clouds (MPCs) can have a net warming or cooling radiative effect on Earth's climate influenced by the phase and concentration of cloud particles. They have received considerable attention due to high spatial coverage and occurrence frequency in the Arctic. To initiate ice formation in MPCs at temperatures above −38 ∘C, ice-nucleating particles (INPs) are required, which therefore have important implications on the radiative properties of MPCs by altering the ice-to-liquid ratio of hydrometeors. As a result, constraining ambient INP concentrations could promote accurate representation of cloud microphysical processes and reduce the uncertainties in estimating the cloud-phase-related climate feedback in climate models. Currently, INP parameterizations are lacking for remote Arctic environments. Here we present INP number concentrations and their variability measured in Ny-Ålesund (Svalbard) at temperatures between 0 and −30 ∘C. No distinguishable seasonal difference was observed from 12 weeks of field measurements during October and November 2019 and March and April 2020. Compared to existing studies, the absence of a seasonal difference is not surprising, as most seasonal differences are reported for summer versus winter time INP concentrations. In addition, correlating INP concentrations to aerosol physical properties was not successful. Therefore, we propose a lognormal-distribution-based parameterization to predict Arctic INP concentration solely as a function of temperature, specifically for the transition seasons autumn and spring to fill in the data gap in the literature pertaining to these seasons. In practice, the parameterized variables allow for (i) the prediction of the most likely INP concentrations and (ii) the retrieval of the governing distribution of INP concentrations at given temperatures in the Arctic.

Ice-nucleating particles in northern Greenland: annual cycles, biological contribution and parameterizations

“…The parameterization from Li et al ( 2022) compares very well with the parameterization suggested for the mix type in our study, with both sharing a very similar slope and the concentration of the latter being only a factor of ≈ 3 lower. This is not surprising, as the parameterization by Li et al (2022) was derived from measurements taking place in October and November 2019 and in March and April 2020, but further south on Svalbard. These months largely overlap with those that were found to be dominated by the mix type in our study (November) or not having a clearly dominating type (April and May), which clearly highlights the need to carry out long-term measurements as done in the present paper in order to get the right understanding of the dynamics and processes of environmental parameters such as INPs.…”

“…This analysis was done based on Ott (1990), who suggested that log-normal distributions occur for atmospheric parameters, arising from successive random dilutions by different atmospheric processes during transportation from sources to measurement sites (as, e.g., VRS). This has been adopted for INP concentrations at different temperatures by studies such as Schrod et al (2020), Welti et al (2018) and recently Li et al (2022). Figure 4 shows the frequency distributions as well as their respective log-normal fits for the same three temperatures that were selected for the N INP time series (−12, −16 and −20 • C).…”

“…The INP parameterizations are shown as solid lines, while the fixed slope fits are shown as dashed lines. Parameterizations from Cooper (1986), Fletcher (1962 and Li et al (2022) were also plotted for comparison. All parameterizations in this study predict INP concentration up to 3 orders of magnitude lower than Cooper (1986) and Fletcher (1962), which were not based on Arctic data.…”

“…The ability of aerosol particles acting as INPs largely depends on their size, morphology, composition and source (Hoose and Möhler, 2012). However, correlating INP concentration with physical properties of the bulk aerosol was shown to be difficult (Welti et al, 2018;Li et al, 2022). Aerosol particles from materials such as mineral dust, sea salt, volcanic ash, soot and biological sources have been shown to serve as INPs in different temperature regimes (Petters et al, 2009;Murray et al, 2012;DeMott et al, 2015;Maters et al, 2019;O'Sullivan et al, 2018;Szyrmer and Zawadzki, 1997).…”

Annual cycle of aerosol properties over the central Arctic during MOSAiC 2019–2020 — light-extinction, CCN, and INP levels from the boundary layer to the tropopause

“…Significant progress has been made during the last years regarding the characterization of local Arctic ice-nucleating particles (INPs) (Creamean et al, 2018(Creamean et al, , 2019(Creamean et al, , 2022Zeppenfeld et al, 2019;Wex et al, 2019;Hartmann et al, 2021;Li et al, 2022;Sze et al, 2022). In a remote environment such as the Arctic where particle concentrations are generally low, local production of biogenic INPs contributes significantly to the INP population in summer (Creamean et al, 2018;Wex et al, 2019) and influence ice nucleation in the lower troposphere.…”