Makoto Koike

Aerosol composition and mixing state influence its ability to form cloud droplets and ice crystals and to scatter and absorb sunlight, all of which affect its impact on climate. In this study, aerosol samples were collected from different altitudes, ranging from the sea surface to ∼ 8000 m, over the ocean in the western North Pacific in the summer of 2022 using an aircraft and a research vessel. The samples were classified into three periods based on the sampled air parcel sources: ocean and desert (period 1), Siberian Forest biomass burning event (period 2), and their mixtures (period 3). Measurements of particle composition using transmission electron microscopy with energy-dispersive X-ray spectrometry revealed that samples from period 1 had high sea salt and mineral dust fractions, whereas samples from period 2 had high fractions of potassium-bearing particles with organics and black carbon. Samples from period 3 showed influences of both sea spray and biomass burning. During periods 1 and 3, the sea salt fractions increased as the samples were collected at lower altitudes. The compositions of biomass burning and sea spray were mixed at individual particles, with higher fractions of Na and K during period 1 and period 2, respectively, than in other periods. Our analysis of individual particles revealed a wide range of compositions and mixing states of particles, which depend on the aerosol source, size, and altitude. These factors need to be considered when evaluating aerosol composition and mixing state, both of which affect aerosol climate effects.

Aerosol composition and mixing state influence its ability to form cloud droplets and ice crystals and to scatter and absorb sunlight, all of which affect its impact on climate. In this study, aerosol samples were collected over the ocean in the western North Pacific at different altitudes from the sea surface to ~8000 m using an aircraft and a research vessel in the summer of 2022. During the campaign, we had samples originating over the ocean, desert, Siberian Forest biomass burning event, and other sources in East Asia. These samples were classified into three periods based on the sampled air parcel sources and particle compositions measured using transmission electron microscopy. Samples from period 1 had high sea salt and mineral dust fractions, while in period 2, the samples had high fractions of potassium-bearing particles with organics and black carbon concentrations, indicating that they originated from a Siberian Forest biomass burning event. The samples from period 3 showed influences of both sea spray and biomass burning. The number fractions of aerosol types also varied depending on particle size and sampling altitude. Compositions of biomass burning and sea spray were mixed at individual particles and the extent of their mixtures depended on the sampling periods and altitudes. Our results showed a wide range of particle compositions and mixing states, which vary with aerosol source, size, and altitude. These factors need to be considered when evaluating aerosol composition and mixing state, both of which affect aerosol climate effects.

An integrated observational study of aerosols and clouds was carried out in summer 2022 over the western North Pacific (off the eastern coast of Hokkaido, Japan) using both an aircraft and a research vessel for the first time in this area. The aim of this experiment was to characterize the physical and chemical properties of aerosols and to evaluate the contributions of anthropogenic and natural emissions to cloud condensation nuclei (CCN) and ice-nucleating particle (INP) concentrations. The experiment also aims to examine the vertical structure of low-level clouds, which have high radiative effects, over this region. Here, we present an overview of the experiment and some preliminary results. Onboard the research vessel, suspended particulate matter in seawater was sampled, and the size distributions of dominant particle types (e.g., diatom fragments and organic matter) were determined. By analyzing atmospheric aerosols sampled from aircraft, we derived the number size distributions of dust-like particles in the air far from source regions. The aerosol size distributions, as measured from both the vessel and aircraft, suggested that most of the aerosols that could act as CCN were of anthropogenic origin: The upper-bound estimate of the sea spray aerosol (SSA) contribution to the CCN concentration at altitudes below 1200 m was 23%. Numerical model simulations generally reproduced the observed aerosol number concentrations. The simulations supported the inference from the observation that most CCN over the study area were of anthropogenic origin. Using this model, SSA emissions were estimated to account for 9% of the cloud radiative effect. Cloud observations from aircraft revealed that low-level clouds tended to have an adiabatic vertical structure under cold air advection, whereas under warm air advection, they occasionally had a layered structure. Such diverse vertical structures of low-level clouds are not generally seen in the subtropics. The integrated observations carried out in this study provided a basic picture of aerosols and clouds over the study area in summer. Further research is needed to elucidate the roles of aerosols in cloud formation and the radiation budget under various meteorological conditions within the framework of atmosphere–ocean interactions.

Aerosol composition and mixing state influence its ability to form cloud droplets and ice crystals and to scatter and absorb sunlight, all of which affect its impact on climate. In this study, aerosol samples were collected over the ocean in the western North Pacific at different altitudes from the sea surface to ~8000 m using an aircraft and a research vessel in the summer of 2022. During the campaign, we had samples originating over the ocean, desert, Siberian Forest biomass burning event, and other sources in East Asia. These samples were classified into three periods based on the sampled air parcel sources and particle compositions measured using transmission electron microscopy. Samples from period 1 had high sea salt and mineral dust fractions, while in period 2, the samples had high fractions of potassium-bearing particles with organics and black carbon concentrations, indicating that they originated from a Siberian Forest biomass burning event. The samples from period 3 showed influences of both sea spray and biomass burning. The number fractions of aerosol types also varied depending on particle size and sampling altitude. Compositions of biomass burning and sea spray were mixed at individual particles and the extent of their mixtures depended on the sampling periods and altitudes. Our results showed a wide range of particle compositions and mixing states, which vary with aerosol source, size, and altitude. These factors need to be considered when evaluating aerosol composition and mixing state, both of which affect aerosol climate effects.

Aerosol composition and mixing state influence its ability to form cloud droplets and ice crystals and to scatter and absorb sunlight, all of which affect its impact on climate. In this study, aerosol samples were collected over the ocean in the western North Pacific at different altitudes from the sea surface to ~8000 m using an aircraft and a research vessel in the summer of 2022. During the campaign, we had samples originating over the ocean, desert, Siberian Forest biomass burning event, and other sources in East Asia. These samples were classified into three periods based on the sampled air parcel sources and particle compositions measured using transmission electron microscopy. Samples from period 1 had high sea salt and mineral dust fractions, while in period 2, the samples had high fractions of potassium-bearing particles with organics and black carbon concentrations, indicating that they originated from a Siberian Forest biomass burning event. The samples from period 3 showed influences of both sea spray and biomass burning. The number fractions of aerosol types also varied depending on particle size and sampling altitude. Compositions of biomass burning and sea spray were mixed at individual particles and the extent of their mixtures depended on the sampling periods and altitudes. Our results showed a wide range of particle compositions and mixing states, which vary with aerosol source, size, and altitude. These factors need to be considered when evaluating aerosol composition and mixing state, both of which affect aerosol climate effects.

Aerosol composition and mixing state influence its ability to form cloud droplets and ice crystals and to scatter and absorb sunlight, all of which affect its impact on climate. In this study, aerosol samples were collected over the ocean in the western North Pacific at different altitudes from the sea surface to ~8000 m using an aircraft and a research vessel in the summer of 2022. During the campaign, we had samples originating over the ocean, desert, Siberian Forest biomass burning event, and other sources in East Asia. These samples were classified into three periods based on the sampled air parcel sources and particle compositions measured using transmission electron microscopy. Samples from period 1 had high sea salt and mineral dust fractions, while in period 2, the samples had high fractions of potassium-bearing particles with organics and black carbon concentrations, indicating that they originated from a Siberian Forest biomass burning event. The samples from period 3 showed influences of both sea spray and biomass burning. The number fractions of aerosol types also varied depending on particle size and sampling altitude. Compositions of biomass burning and sea spray were mixed at individual particles and the extent of their mixtures depended on the sampling periods and altitudes. Our results showed a wide range of particle compositions and mixing states, which vary with aerosol source, size, and altitude. These factors need to be considered when evaluating aerosol composition and mixing state, both of which affect aerosol climate effects.

Aerosol composition and mixing state influence its ability to form cloud droplets and ice crystals and to scatter and absorb sunlight, all of which affect its impact on climate. In this study, aerosol samples were collected over the ocean in the western North Pacific at different altitudes from the sea surface to ~8000 m using an aircraft and a research vessel in the summer of 2022. During the campaign, we had samples originating over the ocean, desert, Siberian Forest biomass burning event, and other sources in East Asia. These samples were classified into three periods based on the sampled air parcel sources and particle compositions measured using transmission electron microscopy. Samples from period 1 had high sea salt and mineral dust fractions, while in period 2, the samples had high fractions of potassium-bearing particles with organics and black carbon concentrations, indicating that they originated from a Siberian Forest biomass burning event. The samples from period 3 showed influences of both sea spray and biomass burning. The number fractions of aerosol types also varied depending on particle size and sampling altitude. Compositions of biomass burning and sea spray were mixed at individual particles and the extent of their mixtures depended on the sampling periods and altitudes. Our results showed a wide range of particle compositions and mixing states, which vary with aerosol source, size, and altitude. These factors need to be considered when evaluating aerosol composition and mixing state, both of which affect aerosol climate effects.