Markus Hartmann

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.

In this study, a new laboratory-based experimental setup, the Optical Lab for Lidar Applications (OLALA), was developed and characterized to measure the polarization properties of size-resolved aerosol particles in the exact backscattering direction. The linear depolarization ratio was measured at 532 nm wavelength at a scattering angle of 180 ± 0.2° to be comparable to lidar observations. To realize exact backscattering measurements, a 50:50 beam splitter was used to establish a coaxial transmit-receive optical configuration. Aerosols were generated using an atomizer and size-selected with a differential mobility analyzer, which allowed to measure particle size distributions in the fine mode (mostly below 1 μm). Polystyrene latex (PSL) beads, ammonium sulfate, sodium chloride, Arizona Test Dust (ATD), and Saxonian soil dust were used as test aerosols to evaluate the performance of the system. PSL particles of diameter 1 μm exhibited the lowest depolarization ratio of 0.017 ± 0.002, which agrees with theoretical values for spherical particles. Arizona Test Dust, which is characterized by an irregular particle shape, produced the highest depolarization ratio of 0.168 ± 0.048 for particles having a median diameter of 766 nm. For the non-spherical particles like sodium chloride, ATD, and Saxonian soil dust, an increase in the depolarization ratio with increasing size was observed.

In this study, a new laboratory-based experimental setup, the Optical Lab for Lidar Applications (OLALA), was developed and characterized to measure the polarization properties of size-resolved aerosol particles in the exact backscattering direction. The linear depolarization ratio was measured at 532 nm wavelength at a scattering angle of 180 ± 0.2° to be comparable to lidar observations. To realize exact backscattering measurements, a 50:50 beam splitter was used to establish a coaxial transmit-receive optical configuration. Aerosols were generated using an atomizer and size-selected with a differential mobility analyzer, which allowed to measure particle size distributions in the fine mode (mostly below 1 μm). Polystyrene latex (PSL) beads, ammonium sulfate, sodium chloride, Arizona Test Dust (ATD), and Saxonian soil dust were used as test aerosols to evaluate the performance of the system. PSL particles of diameter 1 μm exhibited the lowest depolarization ratio of 0.017 ± 0.002, which agrees with theoretical values for spherical particles. Arizona Test Dust, which is characterized by an irregular particle shape, produced the highest depolarization ratio of 0.168 ± 0.048 for particles having a median diameter of 766 nm. For the non-spherical particles like sodium chloride, ATD, and Saxonian soil dust, an increase in the depolarization ratio with increasing size was observed.

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.

In this study, a new laboratory-based experimental setup, the Optical Lab for Lidar Applications (OLALA), was developed and characterized to measure the polarization properties of size-resolved aerosol particles in the exact backscattering direction. The linear depolarization ratio was measured at 532 nm wavelength at a scattering angle of 180 ± 0.2° to be comparable to lidar observations. To realize exact backscattering measurements, a 50:50 beam splitter was used to establish a coaxial transmit-receive optical configuration. Aerosols were generated using an atomizer and size-selected with a differential mobility analyzer, which allowed to measure particle size distributions in the fine mode (mostly below 1 μm). Polystyrene latex (PSL) beads, ammonium sulfate, sodium chloride, Arizona Test Dust (ATD), and Saxonian soil dust were used as test aerosols to evaluate the performance of the system. PSL particles of diameter 1 μm exhibited the lowest depolarization ratio of 0.017 ± 0.002, which agrees with theoretical values for spherical particles. Arizona Test Dust, which is characterized by an irregular particle shape, produced the highest depolarization ratio of 0.168 ± 0.048 for particles having a median diameter of 766 nm. For the non-spherical particles like sodium chloride, ATD, and Saxonian soil dust, an increase in the depolarization ratio with increasing size was observed.

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.