Measurements of natural deposition ice nuclei in Cordoba, Argentina

Ice nucleation in the atmosphere is of practical and fundamental importance since ice crystals influence the release of snow, rain and hail. Suspended aerosols in the atmosphere typically initiate freezing at temperatures below -15 degrees C; although occasionally freezing occurs at higher temperatures. In this work we describe an experimental device designed to measure the concentration of natural ice nuclei under controlled temperature and supersaturation conditions. The measurements were performed at Cordoba City, for temperatures between -15 degrees C and -30 degrees C and the sampled air was supersaturated with respect to ice and subsaturated with respect to liquid water; under these conditions the deposition ice nuclei were quantified. There are few studies reported in the literature regarding measurements of deposition ice nuclei concentration and, to our knowledge, there are no previous laboratory data of this kind of ice nuclei for T < -20 degrees C. The results show that the number of deposition ice nuclei increases at colder temperatures and higher super-saturations. These results are in general in good agreement with results previously reported by other authors. A fitting function which depends on temperature and supersaturation is proposed to parameterize the results obtained in the present work.