9:00 AM - 10:30 AM
[AAS07-P18] Comparison of Ice Nucleating Particles with Auto-Fluorescent Particles Observed over the Western North Pacific to the Arctic Ocean by R/V Mirai cruise
Keywords: Ice Nucleating Particle, Auto-Fluorescent Particle, ship-borne observation
At high latitudes including the Arctic region, mixed-phase clouds consisting of droplets and ice are often present and play an important role in the hydrological cycle and climate of this region. Ice nucleating particles (INPs) present in low abundance in clouds, have a significant influence on the ice formation process and affect the characteristics of mixed-phase clouds by changing cloud radiation properties and lifetimes. It is well known that the particle species that can act as INPs depend on temperature. Therefore, information on the concentration and source of INPs is important for estimating climate and hydrological cycles. However, information on INPs over the ocean at high latitude is extremely poor. In this study, we performed ship-borne observation for investigation of the INPs property and the composition (e.g. fluorescent property) of aerosol particles over the western North Pacific to the Arctic Ocean.
The observation were carried out from 22 August 2016 to 6 October 2016 by R/V Mirai. Samplings of non-size-selective ambient particles for analysis of INPs property and size-selective ambient particles (D>2.5um and <2.5um) for analysis of chemical compositions were performed using a custom-made air sampler and high-volume air sampler, respectively. After observation, we investigated the number concentrations of INPs and chemical compositions for each filter. Airborne auto-fluorescent particles were measured by a wideband integrated bioaerosol spectrometer (WIBS-4) which detects typical biological matter.
In this study, we focused on INPs active at -25°C and-15°C at relatively low and high temperatures, respectively. The number concentrations of INPs active at -25°C (NINP(T>-25°C)) in this cruise varied from 0.03 - 41 L-1. NINP(T>-25°C) over the Arctic Ocean (>70°N) was lower than those over the Bering Sea and the western North Pacific. Comparison of NINP(T>-25°C) with mass concentrations of Fe and Mn by filter analysis indicated that the variation trends were similar, suggesting that particles of terrestrial origin may be influencing observed NINP(T>-25°C). The number concentration of INPs active at -15°C (NINP(T>-15°C)) was significantly observed over the Bering Sea and western North Pacific in late September. Comparison of NINP(T>-25°C) and NINP(T>-15°C) with number concentration auto-fluorescent aerosol particles (NFAP) measured by WIBS-4 indicated that NINP(T>-15°C) shows a higher correlation with NFAP than NINP(T>-25°C), indicating that NINP(T>-15°C) may be influenced by biological materials. In addition, air masses affected by the Siberian Forest fires were also transported over the Bering Sea in this cruise period, suggesting that soil and biogenic particles from biomass burning had a significant impact on the observed NINP(T>-25°C) and NINP(T>-15°C).
The observation were carried out from 22 August 2016 to 6 October 2016 by R/V Mirai. Samplings of non-size-selective ambient particles for analysis of INPs property and size-selective ambient particles (D>2.5um and <2.5um) for analysis of chemical compositions were performed using a custom-made air sampler and high-volume air sampler, respectively. After observation, we investigated the number concentrations of INPs and chemical compositions for each filter. Airborne auto-fluorescent particles were measured by a wideband integrated bioaerosol spectrometer (WIBS-4) which detects typical biological matter.
In this study, we focused on INPs active at -25°C and-15°C at relatively low and high temperatures, respectively. The number concentrations of INPs active at -25°C (NINP(T>-25°C)) in this cruise varied from 0.03 - 41 L-1. NINP(T>-25°C) over the Arctic Ocean (>70°N) was lower than those over the Bering Sea and the western North Pacific. Comparison of NINP(T>-25°C) with mass concentrations of Fe and Mn by filter analysis indicated that the variation trends were similar, suggesting that particles of terrestrial origin may be influencing observed NINP(T>-25°C). The number concentration of INPs active at -15°C (NINP(T>-15°C)) was significantly observed over the Bering Sea and western North Pacific in late September. Comparison of NINP(T>-25°C) and NINP(T>-15°C) with number concentration auto-fluorescent aerosol particles (NFAP) measured by WIBS-4 indicated that NINP(T>-15°C) shows a higher correlation with NFAP than NINP(T>-25°C), indicating that NINP(T>-15°C) may be influenced by biological materials. In addition, air masses affected by the Siberian Forest fires were also transported over the Bering Sea in this cruise period, suggesting that soil and biogenic particles from biomass burning had a significant impact on the observed NINP(T>-25°C) and NINP(T>-15°C).