Significant continental source of ice-nucleating particles at the tip of Chile's southernmost Patagonia region

Abstract

Abstract. The sources and abundance of ice-nucleating particles (INPs) that initiate cloud ice formation remain understudied, especially in the Southern Hemisphere. In this study, we present INP measurements taken close to Punta Arenas, Chile, at the southernmost tip of South America from May 2019 to March 2020, during the Dynamics, Aerosol, Cloud, And Precipitation Observations in the Pristine Environment of the Southern Ocean (DACAPO-PESO) campaign. The highest ice nucleation temperature was observed at −3 ∘C, and from this temperature down to ∼-10 ∘C, a sharp increase of INP number concentration (NINP) was observed. Heating of the samples revealed that roughly 90 % and 80 % of INPs are proteinaceous-based biogenic particles at >-10 and −15 ∘C, respectively. The NINP at Punta Arenas is much higher than that in the Southern Ocean, but it is comparable with an agricultural area in Argentina and forestry environment in the US. Ice active surface site density (ns) is much higher than that for marine aerosol in the Southern Ocean, but comparable to English fertile soil dust. Parameterization based on particle number concentration in the size range larger than 500 nm (N>500 nm) from the global average (DeMott et al., 2010) overestimates the measured INP, but the parameterization representing biological particles from a forestry environment (Tobo et al., 2013) yields NINP comparable to this study. No clear seasonal variation of NINP was observed. High precipitation is one of the most important meteorological parameters to enhance the NINP in both cold and warm seasons. A comparison of data from in situ and lidar measurements showed good agreement for concentrations of large aerosol particles (>500 nm) when assuming continental conditions for retrieval of the lidar data, suggesting that these particles were well mixed within the planetary boundary layer (PBL). This corroborates the continental origin of these particles, consistent with the results from our INP source analysis. Overall, we suggest that a high NINP of biogenic INPs originated from terrestrial sources and were added to the marine air masses during the overflow of a maximum of roughly 150 km of land before arriving at the measurement station.

Bioaerosols are the dominant source of warm-temperature immersion-mode INPs and drive uncertainties in INP predictability

“…Dust particles were a minor INP source at −12°C, but increased in importance at colder temperatures, contributing 10 to 40% of the INPs active at −19°C. These results are consistent with previous literature showing that bio-INPs make up a greater fraction of continental boundary layer INPs at warmer temperatures than at colder temperatures ( 19 , 25 , 36 ).…”

“…S6), environmental factors driving variability in bioaerosol emissions and concentrations are likely not fully captured by current models. For example, models currently do not represent the previously noted increases in bio-INP concentrations that frequently follow rainfall ( 25 , 33 , 34 , 36 , 37 ). Likewise, our simulations did not predict the increase in bio-INPs following precipitation (fig.…”

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

“…The number of heat-labile INPs can be seen as a proxy for the number of biological INPs in a sample. In order to quantify the presence of heat-labile INPs in the samples, a similar analysis was conducted as in Gong et al (2022). The atmospheric INP number concentration of the heated samples (N heated INP,air ) and its corresponding unheated samples (i.e., the full spectrum, see Sect.…”

Characterization of Southern Ocean Boundary Layer Clouds Using Airborne Radar, Lidar, and In Situ Cloud Data: Results From SOCRATES

“…Past studies have shown that supercooled liquid water (SLW; liquid water at subfreezing temperatures) is especially common in SO clouds, and more prevalent than at similar latitudes in the Northern Hemisphere (NH), likely due to the lack of ice nucleating particles, which tend to increase glaciation rates, over the SO (Gong et al., 2022; Kanitz et al., 2011; Radenz et al., 2021; Vergara‐Temprado et al., 2018). SLW is particularly common within low clouds, although the ice phase becomes more prevalent at higher latitudes (Haynes et al., 2011; Huang et al., 2012).…”