Laboratory measurements of ice nuclei particle concentration in the range of − 29 to − 48 °C

Abstract

This work quantifies the natural ice nuclei particle (INP) concentration activated at temperatures (T) lower than −29 °C in Córdoba, a city located in a semiarid region in the center of Argentina. Laboratory INP concentration measurements were performed in a cloud chamber where water supersaturation was reached by an adiabatic isobaric mixture of two air masses with different relative humidities. Once the activated INPs grew up to form ice crystals, these crystals were detected and quantified due to the sparkles they produce when they reflect the light incident on them. Following this methodology, a total of 123 ice crystal (i.e. INP) concentration measurements were performed at a T range of −29 °C to −48 °C.From these measurements it was found that the values of the INP concentration increased with T between −29 °C and approximately −38 °C, but they remained almost constant with T between −38 °C and − 48 °C. This behavior could be related to the dependence of the number of active sites with T. The INP concentration measurements obtained in this work were compared with those reported in recent studies. In addition, considering the elemental composition of the particulate matter in the site of study, we hypothesized that aluminosilicate minerals could be responsible for the INP measurements presented. This assumption was also made by comparing the obtained measurements with different parameterizations reported in the literature. Even though this hypothesis deserves to be tested, this study reports the first INP concentration measurements at temperatures lower than −30 °C in Argentina being one of the few works reporting such measures in the Southern Hemisphere.