Jonas Schaefer

New particle formation (NPF) can impact the Arctic radiative energy budget since this region is particularly sensitive to changes in aerosol particle and cloud condensation nuclei concentrations. Prior measurements have predominantly investigated NPF in the Arctic atmospheric boundary layer (ABL), while vertically-resolved studies on newly formed aerosol particles remain scarce. Here, we present an analysis which suggests that NPF may take place throughout the entire lower Arctic troposphere. We have reached this conclusion by analyzing aerosol particle number size distribution data collected during a springtime aircraft campaign (BACSAM II) in the vicinity of Svalbard, the Fram Strait, and northern Greenland. We detected newly formed aerosol particles over distances of hundreds of kilometers, at various altitudes ranging from about 60 to 3900 m, and identified four atmospheric scenarios for their occurrence: newly formed particles in the free troposphere, in the ABL over sea ice, in the vicinity of clouds, and in the ABL over ocean with sea ice floes. Our results indicate that regional Arctic atmospheric processes as well as long-range transport may play key roles in the formation of new particles. In particular, we deduce that one possible mechanism leading to free tropospheric NPF could be associated with warm-air intrusions.

New particle formation (NPF) can impact the Arctic radiative energy budget since this region is particularly sensitive to changes in aerosol particle and cloud condensation nuclei concentrations. Prior studies have predominantly investigated NPF in the Arctic atmospheric boundary layer (ABL), concluding that this phenomenon primarily takes place close to the surface. However, this study shows that NPF may take place throughout the entire lower Arctic troposphere. We have reached this conclusion by analyzing particle number size distribution data collected during a springtime aircraft campaign in the vicinity of Svalbard, the Fram Strait, and northern Greenland. We detected newly formed aerosol particles at various altitudes ranging from about 60 m to 3900 m and identified three atmospheric scenarios for their occurrence: newly formed particles in the free troposphere, in the ABL over sea ice, and in the vicinity of clouds. Our results suggest that regional Arctic atmospheric processes as well as long-range transport play key roles in the formation of new particles. Based on our data, we furthermore conclude that NPF may be a frequent and geographically extended phenomenon in the Arctic free troposphere.

New particle formation (NPF) can impact the Arctic radiative energy budget since this region is particularly sensitive to changes in aerosol particle and cloud condensation nuclei concentrations. Prior studies have predominantly investigated NPF in the Arctic atmospheric boundary layer (ABL), concluding that this phenomenon primarily takes place close to the surface. However, this study shows that NPF may take place throughout the entire lower Arctic troposphere. We have reached this conclusion by analyzing particle number size distribution data collected during a springtime aircraft campaign in the vicinity of Svalbard, the Fram Strait, and northern Greenland. We detected newly formed aerosol particles at various altitudes ranging from about 60 m to 3900 m and identified three atmospheric scenarios for their occurrence: newly formed particles in the free troposphere, in the ABL over sea ice, and in the vicinity of clouds. Our results suggest that regional Arctic atmospheric processes as well as long-range transport play key roles in the formation of new particles. Based on our data, we furthermore conclude that NPF may be a frequent and geographically extended phenomenon in the Arctic free troposphere.

New particle formation (NPF) can impact the Arctic radiative energy budget since this region is particularly sensitive to changes in aerosol particle and cloud condensation nuclei concentrations. Prior studies have predominantly investigated NPF in the Arctic atmospheric boundary layer (ABL), concluding that this phenomenon primarily takes place close to the surface. However, this study shows that NPF may take place throughout the entire lower Arctic troposphere. We have reached this conclusion by analyzing particle number size distribution data collected during a springtime aircraft campaign in the vicinity of Svalbard, the Fram Strait, and northern Greenland. We detected newly formed aerosol particles at various altitudes ranging from about 60 m to 3900 m and identified three atmospheric scenarios for their occurrence: newly formed particles in the free troposphere, in the ABL over sea ice, and in the vicinity of clouds. Our results suggest that regional Arctic atmospheric processes as well as long-range transport play key roles in the formation of new particles. Based on our data, we furthermore conclude that NPF may be a frequent and geographically extended phenomenon in the Arctic free troposphere.

New particle formation (NPF) can impact the Arctic radiative energy budget since this region is particularly sensitive to changes in aerosol particle and cloud condensation nuclei concentrations. Prior studies have predominantly investigated NPF in the Arctic atmospheric boundary layer (ABL), concluding that this phenomenon primarily takes place close to the surface. However, this study shows that NPF may take place throughout the entire lower Arctic troposphere. We have reached this conclusion by analyzing particle number size distribution data collected during a springtime aircraft campaign in the vicinity of Svalbard, the Fram Strait, and northern Greenland. We detected newly formed aerosol particles at various altitudes ranging from about 60 m to 3900 m and identified three atmospheric scenarios for their occurrence: newly formed particles in the free troposphere, in the ABL over sea ice, and in the vicinity of clouds. Our results suggest that regional Arctic atmospheric processes as well as long-range transport play key roles in the formation of new particles. Based on our data, we furthermore conclude that NPF may be a frequent and geographically extended phenomenon in the Arctic free troposphere.

Ice-nucleating particles (INPs) play a crucial role in Earth's weather and climate by influencing cloud properties and precipitation. However, their abundance in the free troposphere, vertical distribution, and transport mechanisms are not well-characterized. This study presents immersion INP measurements from filter samples collected aboard the High Altitude and LOng range research aircraft (HALO) in the troposphere and the lower stratosphere (up to 14.5 km) over Europe during the CIRRUS-HL (Cirrus in High Latitudes) campaign in summer 2021. By sampling cloud particle residuals and aerosol particles in the inflow and outflow of deep convective clouds (DCCs), and performing offline INP analysis, we shed light on the vertical transport and segregation of INPs in DCCs. INP-temperature spectra of convective inflow included both INPs active at high ( T > −15 °C) and low temperatures ( T < −20 °C). In contrast the outflow spectra only featured INPs active at low temperatures. We explain the observed INP segregation in the updraft with precipitation scavenging of INPs active at high temperatures. INPs active at lower temperatures ( T < −20 °C), however, are efficiently transported upwards into the free troposphere. There, ambient temperatures are below −40 °C, i.e., temperatures far below the temperatures at which these INPs initiate immersion freezing. In the DCC outflow, INP concentrations exceed the upper tropospheric background concentration by at least two orders of magnitude. These INPs are then available for ice formation in mid and upper tropospheric clouds.

Ice-nucleating particles (INPs) play a crucial role in Earth’s weather and climate by influencing cloud properties and precipitation. However, their abundance in the free troposphere, vertical distribution, and transport mechanisms are not well-characterized. This study presents immersion INP measurements from filter samples collected aboard the HALO research aircraft in the troposphere and the lower stratosphere (up to 14.5 km) over Europe during the CIRRUS-HL (Cirrus in High Latitudes) campaign in summer 2021. By sampling cloud particle residuals and aerosol particles in the inflow and outflow of deep convective clouds (DCCs) and performing offline INP analysis, we shed light on the vertical transport and segregation of INPs in DCCs. While INP-temperature spectra of convective inflow included both INPs active at high (T > -15 °C) and low temperatures (T < -20 °C), the in-cloud and outflow spectra only featured INPs active at low temperatures. We explain the observed INP segregation in the updraft with precipitation scavenging of INPs active at high temperatures. In contrast, INPs active at lower temperatures (T < -20 °C) are efficiently transported upwards into the free troposphere with ambient temperatures below -40 °C, i.e., temperatures far below the temperatures at which these INPs initiate immersion freezing. In the DCC outflow, INP concentrations exceed the upper tropospheric background concentration by at least two orders of magnitude. These INPs are then available for ice formation in mid and upper tropospheric clouds.

New particle formation (NPF) can impact the Arctic radiative energy budget since this region is particularly sensitive to changes in aerosol particle and cloud condensation nuclei concentrations. Prior studies have predominantly investigated NPF in the Arctic atmospheric boundary layer (ABL), concluding that this phenomenon primarily takes place close to the surface. However, this study shows that NPF may take place throughout the entire lower Arctic troposphere. We have reached this conclusion by analyzing particle number size distribution data collected during a springtime aircraft campaign in the vicinity of Svalbard, the Fram Strait, and northern Greenland. We detected newly formed aerosol particles at various altitudes ranging from about 60 m to 3900 m and identified three atmospheric scenarios for their occurrence: newly formed particles in the free troposphere, in the ABL over sea ice, and in the vicinity of clouds. Our results suggest that regional Arctic atmospheric processes as well as long-range transport play key roles in the formation of new particles. Based on our data, we furthermore conclude that NPF may be a frequent and geographically extended phenomenon in the Arctic free troposphere.

New particle formation (NPF) can impact the Arctic radiative energy budget since this region is particularly sensitive to changes in aerosol particle and cloud condensation nuclei concentrations. Prior studies have predominantly investigated NPF in the Arctic atmospheric boundary layer (ABL), concluding that this phenomenon primarily takes place close to the surface. However, this study shows that NPF may take place throughout the entire lower Arctic troposphere. We have reached this conclusion by analyzing particle number size distribution data collected during a springtime aircraft campaign in the vicinity of Svalbard, the Fram Strait, and northern Greenland. We detected newly formed aerosol particles at various altitudes ranging from about 60 m to 3900 m and identified three atmospheric scenarios for their occurrence: newly formed particles in the free troposphere, in the ABL over sea ice, and in the vicinity of clouds. Our results suggest that regional Arctic atmospheric processes as well as long-range transport play key roles in the formation of new particles. Based on our data, we furthermore conclude that NPF may be a frequent and geographically extended phenomenon in the Arctic free troposphere.

Ice-nucleating particles (INPs) play a crucial role in Earth’s weather and climate by influencing cloud properties and precipitation. However, their abundance in the free troposphere, vertical distribution, and transport mechanisms are not well-characterized. This study presents immersion INP measurements from filter samples collected aboard the HALO research aircraft in the troposphere and the lower stratosphere (up to 14.5 km) over Europe during the CIRRUS-HL (Cirrus in High Latitudes) campaign in summer 2021. By sampling cloud particle residuals and aerosol particles in the inflow and outflow of deep convective clouds (DCCs) and performing offline INP analysis, we shed light on the vertical transport and segregation of INPs in DCCs. While INP-temperature spectra of convective inflow included both INPs active at high (T > -15 °C) and low temperatures (T < -20 °C), the in-cloud and outflow spectra only featured INPs active at low temperatures. We explain the observed INP segregation in the updraft with precipitation scavenging of INPs active at high temperatures. In contrast, INPs active at lower temperatures (T < -20 °C) are efficiently transported upwards into the free troposphere with ambient temperatures below -40 °C, i.e., temperatures far below the temperatures at which these INPs initiate immersion freezing. In the DCC outflow, INP concentrations exceed the upper tropospheric background concentration by at least two orders of magnitude. These INPs are then available for ice formation in mid and upper tropospheric clouds.