ALBERT

Description: This data set unites the individual data of the MOSAiC Airborne observations in the Central Arctic (MOSAiC-ACA) campaign, carried out in late summer 2020 northwest of Svalbard (Norway). The objective of MOSAiC-ACA was to study turbulent fluxes of energy and momentum in the Arctic boundary layer and low- and mid-level mixed-phase clouds and their role in Arctic amplification in the exit area of the research vessel Polarstern during the MOSAiC expedition. The research aircraft Polar 5 was equipped with active and passive remote sensing instruments, measurements for turbulent and radiative energy fluxes, insitu probes for cloud and aerosol particles, and dropsondes. In total, 10 research flights with 44 flight hours over the open ocean and the marginal sea ice zone have been performed between 30 August and 13 September 2020.

Description: This data set unites the individual data of the Airborne measurements of radiative and turbulent FLUXes of energy and momentum in the Arctic boundary layer (AFLUX) campaign, carried out in spring northwest of Svalbard (Norway). The objective of AFLUX was to study turbulent fluxes of energy and momentum in the Arctic boundary layer and low- and mid-level mixed-phase clouds and their role in Arctic amplification. The research aircraft Polar 5 was equipped with active and passive remote sensing instruments, measurements for turbulent and radiative energy fluxes, insitu probes for cloud and aerosol particles, and dropsondes. In total, 14 research flights with 67 flight hours over the open ocean and the marginal sea ice zone have been performed between 19 March and 11 April 2019.

Description: This data set unites the individual data of the Arctic CLoud Observations Using airborne measurements during polar Day (ACLOUD) campaign, which was carried out north-west of Svalbard (Norway) between 23 May and 6 June 2017. The objective of ACLOUD was to study Arctic boundary layer and mid-level clouds and their role in Arctic amplification. Two research aircraft (Polar 5 and 6) jointly performed 22 research flights over the transition zone between open ocean and closed sea ice. Both aircraft were equipped with identical instrumentation for measurements of basic meteorological parameters, as well as for turbulent and radiative energy fluxes. In addition, on Polar 5 active and passive remote sensing instruments were installed, while Polar 6 operated in situ instruments to characterize cloud and aerosol particles as well as trace gases.

Description: This data set is composed of in-situ measurement of arctic cloud microphysical properties observed during the ACLOUD-AC3 campaign which occurred during June 2017. These measurements were made using the CDP, CIP and PIP probes from the airborne measurement platform of the Laboratoire de Météorologie Physique (CNRS/UCA, Aubière, France). There is one file per flight. All files are in NetCDF format with a complete description of the parameters inside. A detailed description of the data processing will be done in an upcoming data paper.

Description: This data set is composed of in-situ measurement of arctic cloud microphysical properties (particle size distribution and volumic cloud particle diffusion properties) observed during the MOSAIC-ACA campaign, which occurred between August 30th and September 13th 2020. These measurements were made using the 2D stereoscopic (2D-S, SPEC Inc.) and Polar Nephelometer (Gayet et al., 1997) probes from the airborne measurement platform of the Laboratoire de Météorologie Physique (CNRS/UCA, Aubière, France). There is one file per flight. All files are in NetCDF format, with a complete description of the parameters inside. A detailed list of the parameters present in the data set is added in a separate document.

Description: This data set is composed of in-situ measurement of arctic cloud microphysical properties (particle size distribution and volumic cloud particle scattering properties) observed during the HALO-AC3 campaign, which occurred between March 20th and April 10th 2022. These measurements were made using the 2D stereoscopic (2D-S, SPEC Inc.) and Polar Nephelometer (Gayet et al., 1997) probes from the airborne measurement platform of the Laboratoire de Météorologie Physique (CNRS/UCA, Aubière, France). There is one file per flight. All files are in NetCDF format, with a complete description of the parameters inside. A detailed list of the parameters present in the data set is added in a separate document (see "Further details" link).

Description: This data set is composed of in-situ measurement of arctic cloud microphysical properties (particle size distribution and volumic cloud particle diffusion properties) observed during the AFLUX-AC3 campaign, which occurred between 19 March and 11 April 2019. These measurements were made using the 2D stereoscopic (2D-S, SPEC Inc.) and Polar Nephelometer (Gayet et al., 1997) probes from the airborne measurement platform of the Laboratoire de Météorologie Physique (CNRS/UCA, Aubière, France). There is one file per flight. All files are in NetCDF format, with a complete description of the parameters inside. A detailed list of the parameters present in the data set is added in a separate document.

Description: Clouds play an important role in Arctic amplification. This term represents the recently observed enhanced warming of the Arctic relative to the global increase of near-surface air temperature. However, there are still important knowledge gaps regarding the interplay between Arctic clouds and aerosol particles, and surface properties, as well as turbulent and radiative fluxes that inhibit accurate model simulations of clouds in the Arctic climate system. In an attempt to resolve this so-called Arctic cloud puzzle, two comprehensive and closely coordinated field studies were conducted: the Arctic Cloud Observations Using Airborne Measurements during Polar Day (ACLOUD) aircraft campaign and the Physical Feedbacks of Arctic Boundary Layer, Sea Ice, Cloud and Aerosol (PASCAL) ice breaker expedition. Both observational studies were performed in the framework of the German Arctic Amplification: Climate Relevant Atmospheric and Surface Processes, and Feedback Mechanisms (AC)3 project. They took place in the vicinity of Svalbard, Norway, in May and June 2017. ACLOUD and PASCAL explored four pieces of the Arctic cloud puzzle: cloud properties, aerosol impact on clouds, atmospheric radiation, and turbulent dynamical processes. The two instrumented Polar 5 and Polar 6 aircraft; the icebreaker Research Vessel (R/V) Polarstern; an ice floe camp including an instrumented tethered balloon; and the permanent ground-based measurement station at Ny-Ålesund, Svalbard, were employed to observe Arctic low- and mid-level mixed-phase clouds and to investigate related atmospheric and surface processes. The Polar 5 aircraft served as a remote sensing observatory examining the clouds from above by downward-looking sensors; the Polar 6 aircraft operated as a flying in situ measurement laboratory sampling inside and below the clouds. Most of the collocated Polar 5/6 flights were conducted either above the R/V Polarstern or over the Ny-Ålesund station, both of which monitored the clouds from below using similar but upward-looking remote sensing techniques as the Polar 5 aircraft. Several of the flights were carried out underneath collocated satellite tracks. The paper motivates the scientific objectives of the ACLOUD/PASCAL observations and describes the measured quantities, retrieved parameters, and the applied complementary instrumentation. Furthermore, it discusses selected measurement results and poses critical research questions to be answered in future papers analyzing the data from the two field campaigns.

Description: Two airborne campaigns (AFLUX and MOSAiC-ACA) were conducted in spring 2019 and late summer 2020 to investigate low- and midlevel clouds and related atmospheric parameters in the central Arctic. The measurements aim at better understanding the role of Arctic clouds and their interactions with the surface - open ocean or sea ice - in light of amplified climate change in the Arctic. During the campaigns the Basler BT-67 research aircraft Polar 5 based in Svalbard (78.24 N, 15.49 E) equipped with a comprehensive in-situ cloud payload performed in total 24 flights over the Arctic ocean and in the Fram Strait. A combination of size spectrometers (CDP and CAS) and 2-dimensional imaging probes (CIP and PIP) covering the size range of Arctic cloud hydrometeors from 0.5µm to 6.2mm measured the total particle number concentration, the particle size distribution and the median volume diameter. Liquid water content and ice water content were measured with the Nevzorov bulk probe. The cloud water content (liquid and ice water content) from the Nevzorov probe is compared to the cloud water content derived from particle size measurements using consistent mass-dimension relationships. Here we give an overview of the microphysical cloud properties measured in spring and late summer in high northern latitudes at altitudes up to 4 km. We derive the temperature and altitude dependence of liquid, mixed phase and ice cloud properties and investigate their seasonal variability. Differences in cloud properties above the sea ice and the open ocean are examined, supporting the hypothesis of an enhanced median volume diameter over open ocean compared to clouds formed over the sea ice. The comprehensive data set on microphysical cloud properties enhances our understanding of cloud formation and mixed phase cloud processes over the Arctic ocean, it can be used to validate remote sensing retrievals and models and helps to assess the role of clouds for stronger impact of climate change in the Arctic.

Description: Two airborne field campaigns focusing on observations of Arctic mixed-phase clouds and boundary layer processes and their role with respect to Arctic amplification have been carried out in spring 2019 and late summer 2020 over the Fram Strait northwest of Svalbard. The latter campaign was closely connected to the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition. Comprehensive datasets of the cloudy Arctic atmosphere have been collected by operating remote sensing instruments, in-situ probes, instruments for the measurement of turbulent fluxes of energy and momentum, and dropsondes on board the AWI research aircraft Polar 5. In total, 24 flights with 111 flight hours have been performed over open ocean, the marginal sea ice zone, and sea ice. The datasets follow documented methods and quality assurance and are suited for studies on Arctic mixedphase clouds and their transformation processes, for studies with a focus on Arctic boundary layer processes, and for satellite validation applications. All datasets are freely available via the world data center PANGAEA.