Immersion freezing efficiencies of ambient particles collected from five
different regions across latitudes
This poster presents immersion freezing efficiencies of ambient
particles collected from different latitudes between 79 °N and 75 °S. We
collected particles using aerosol impactors at five different geographic
locations, including i) the Atlantic sector of the Arctic, ii) an urban
area in Europe, iii) a rural location in the U.S., iv) a mid-latitude
agricultural site in the U.S., and v) the Antarctica peninsula area
around Weddell Sea, representing unique particle episodes and
atmospheric conditions. Then, we used an offline droplet-freezing assay
instrument to measure fine-temperature-resolved ice-nucleating particle
(INP) concentrations at T > -25 °C (with a detection
capability of >0.0001 per L of air) for each region. Our
preliminary results show INP concentrations in polar regions are - as
expected - lower compared to mid-latitudes. Low concentrations of
high-latitude INPs have been reported in other previous studies (e.g.,
Bigg et al., 2001; Rogers, 1996; Fountain and Ohtake, 1985; Mason et
al., 2015; Ardon-Dryer and Levin, 2014; Belosi and Santachiara, 2014).
Another important observation is the high variability of mid-latitude
INP concentrations. A difference in the aerosol episode and properties
may be key for such a high variability in the mid-latitude region. The
composition of INPs varies, but it typically includes dust-related
minerals, pollution aerosol, biogenic nuclei and marine microlayers. It
is therefore important to comprehensively study realistic representation
of both INP concentration and composition (ultimately for model
parameterization) and their relevance to the aerosol-cloud interactions
with a better temporal resolution under different atmospheric states and
a wider spatial coverage of INP sampling sites (see Fig. 1). References:
Ardon-Dryer, K. and Levin, Z.: Atmos. Chem. Phys., 14, 5217-5231, 2014.
Belosi, F., and Santachiara, G.: Atmos. Res., 145–146, 105–111, 2014.
Bigg, E. K.: Tellus B, 48, 223–233, 1996. Fountain, A. G., and Ohtake,
T.: 1985: Climate Appl. Meteor., 24, 377–382, 1985. Mason, R. H. et
al.: Atmos. Chem. Phys., 16, 1637–1651, 2016. Rogers, D. C. et al.: J.
Atmos. Oceanic Technol., 18, 725–741, 2001.