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Global warming is amplified in the Arctic. However, numerical models struggle to represent key processes that determine Arctic weather and climate. To collect data that help to constrain the models, the HALO–(𝒜𝒞)3 aircraft campaign was conducted over the Norwegian and Greenland seas, the Fram Strait, and the central Arctic Ocean in March and April 2022. The campaign focused on one specific challenge posed by the models, namely the reasonable representation of transformations of air masses during their meridional transport into and out of the Arctic via northward moist- and warm-air intrusions (WAIs) and southward marine cold-air outbreaks (CAOs). Observations were made over areas of open ocean, the marginal sea ice zone, and the central Arctic sea ice. Two low-flying and one long-range, high-altitude research aircraft were flown in colocated formation whenever possible. To follow the air mass transformations, a quasi-Lagrangian flight strategy using trajectory calculations was realized, enabling us to sample the same moving-air parcels twice along their trajectories. Seven distinct WAI and 12 CAO cases were probed. From the quasi-Lagrangian measurements, we have quantified the diabatic heating/cooling and moistening/drying of the transported air masses. During CAOs, maximum values of 3 K h−1 warming and 0.3 g kg−1 h−1 moistening were obtained below 1 km altitude. From the observations of WAIs, diabatic cooling rates of up to 0.4 K h−1 and a moisture loss of up to 0.1 g kg−1 h−1 from the ground to about 5.5 km altitude were derived. Furthermore, the development of cloud macrophysical (cloud-top height and horizontal cloud cover) and microphysical (liquid water path, precipitation, and ice index) properties along the southward pathways of the air masses were documented during CAOs, and the moisture budget during a specific WAI event was estimated. In addition, we discuss the statistical frequency of occurrence of the different thermodynamic phases of Arctic low-level clouds, the interaction of Arctic cirrus clouds with sea ice and water vapor, and the characteristics of microphysical and chemical properties of Arctic aerosol particles. Finally, we provide a proof of concept to measure mesoscale divergence and subsidence in the Arctic using data from dropsondes released during the flights.

Comparing the output of general circulation models to observations is essential for assessing and improving the quality of models. While numerical weather prediction models are routinely assessed against a large array of observations, comparing climate models and observations usually requires long time series to build robust statistics. Here, we show that by nudging the large-scale atmospheric circulation in coupled climate models, model output can be compared to local observations for individual days. We illustrate this for three climate models during a period in April 2020 when a warm air intrusion reached the MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) expedition in the central Arctic. Radiosondes, cloud remote sensing and surface flux observations from the MOSAiC expedition serve as reference observations. The climate models AWI-CM1/ECHAM and AWI-CM3/IFS miss the diurnal cycle of surface temperature in spring, likely because both models assume the snowpack on ice to have a uniform temperature. CAM6, a model that uses three layers to represent snow temperature, represents the diurnal cycle more realistically. During a cold and dry period with pervasive thin mixed-phase clouds, AWI-CM1/ECHAM only produces partial cloud cover and overestimates downwelling shortwave radiation at the surface. AWI-CM3/IFS produces a closed cloud cover but misses cloud liquid water. Our results show that nudging the large-scale circulation to the observed state allows a meaningful comparison of climate model output even to short-term observational campaigns. We suggest that nudging can simplify and accelerate the pathway from observations to climate model improvements and substantially extends the range of observations suitable for model evaluation.

Abstract Climate models have substantial biases in the climatological latitude of the Southern Hemisphere eddy‐driven jet and the time scale of annular mode variability and disagree on the jet response to climate change. Zonally symmetric dry dynamical cores are often used for idealized modeling of the jet response to forcing and its sensitivity to model setup changes. The limits to which these models represent the key mechanisms that control the jet in complex models or the real world have not been systematically investigated. Here we show that substantial intermodel differences in jet latitude and strength can arise from differences in dynamical cores and resolved topography. Including topography and a more realistic surface drag in a dry model substantially alters the jet response to changes in drag strength. Using real‐world maps, enhanced drag over land shifts the jet poleward, whereas enhanced drag over the ocean leads to an equatorward shift. No universal relationship between annular mode time scale and forced response emerges in the dry model with topography. These results suggest that zonally symmetric models with Rayleigh drag lack important mechanisms that control the behavior of the midlatitude jet in coupled climate models. A dry model with topography and quadratic surface drag can fill this gap in the model hierarchy.

The concept of feedback is key in assessing whether a perturbation to a system is amplified or damped by mechanisms internal to the system. In polar regions, climate dynamics are controlled by both radiative and non-radiative interactions between the atmosphere, ocean, sea ice, ice sheets and land surfaces. Precisely quantifying polar feedbacks is required for a process-oriented evaluation of climate models, a clear understanding of the processes responsible for polar climate changes, and a reduction in uncertainty associated with model projections. This quantification can be performed using a simple and consistent approach that is valid for a wide range of feedbacks, offering the opportunity for more systematic feedback analyses and a better understanding of polar climate changes.

Previous single-model experiments have found that Arctic sea ice loss can influence the atmospheric circulation. To evaluate this process in a multimodel ensemble, a novel methodology is here presented and applied to infer the influence of Arctic sea ice loss in the CMIP5 future projections. Sea ice influence is estimated by comparing the circulation response in the RCP8.5 scenario against the circulation response to sea surface warming and CO 2 increase inferred from the AMIPFuture and AMIP4xCO2 experiments, where sea ice is unperturbed. Multimodel evidence of the impact of sea ice loss on midlatitude atmospheric circulation is identified in late winter (January-March), when the sea ice-related surface heat flux perturbation is largest. Sea ice loss acts to suppress the projected poleward shift of the North Atlantic jet, to increase surface pressure in northern Siberia, and to lower it in North America. These features are consistent with previous single-model studies, and the present results indicate that they are robust to model formulation.

Weather and climate models struggle to represent lower tropospheric temperature and moisture profiles and surface fluxes in Arctic winter, partly because they lack or misrepresent physical processes that are specific to high latitudes. Observations have revealed two preferred states of the Arctic winter boundary layer. In the cloudy state, cloud liquid water limits surface radiative cooling, and temperature inversions are weak and elevated. In the radiatively clear state, strong surface radiative cooling leads to the build-up of surface-based temperature inversions. Many large-scale models lack the cloudy state, and some substantially underestimate inversion strength in the clear state. Here, the transformation from a moist to a cold dry air mass is modelled using an idealized Lagrangian perspective. The trajectory includes both boundary layer states, and the single-column experiment is the first L agrangian Arc tic air form ation experiment (Larcform 1) organized within GEWEX GASS (Global atmospheric system studies). The intercomparison reproduces the typical biases of large-scale models: Some models lack the cloudy state of the boundary layer due to the representation of mixed-phase micro-physics or to the interaction between micro-and macrophysics. In some models, high emissivities of ice clouds or the lack of an insulating snow layer prevent the build-up of surface-based inversions in the radiatively clear state. Models substantially disagree on the amount of cloud liquid water in the cloudy state and on turbulent heat fluxes under clear skies. Observations of air mass transformations including both boundary layer states would allow for a tighter constraint of model behaviour.

A recent intercomparison exercise proposed by the Working Group for Numerical Experimentation (WGNE) revealed that the parameterized, or unresolved, surface stress in weather forecast models is highly model-dependent, especially over orography. Models of comparable resolution differ over land by as much as 20% in zonal mean total subgrid surface stress ( τ tot ). The way τ tot is partitioned between the different parameterizations is also model-dependent. In this study, we simulated in a particular model an increase in τ tot comparable with the spread found in the WGNE intercomparison. This increase was simulated in two ways, namely by increasing independently the contributions to τ tot of the turbulent orographic form drag scheme (TOFD) and of the orographic low-level blocking scheme (BLOCK). Increasing the parameterized orographic drag leads to significant changes in surface pressure, zonal wind and temperature in the Northern Hemisphere during winter both in 10 day weather forecasts and in seasonal integrations. However, the magnitude of these changes in circulation strongly depends on which scheme is modified. In 10 day forecasts, stronger changes are found when the TOFD stress is increased, while on seasonal time scales the effects are of comparable magnitude, although different in detail. At these time scales, the BLOCK scheme affects the lower stratosphere winds through changes in the resolved planetary waves which are associated with surface impacts, while the TOFD effects are mostly limited to the lower troposphere. The partitioning of τ tot between the two schemes appears to play an important role at all time scales.

With the increased brilliance of state-of-the-art synchrotron radiation sources and the advent of free-electron lasers (FELs) enabling revolutionary science with EUV to X-ray photons comes an urgent need for suitable photon imaging detectors. Requirements include high frame rates, very large dynamic range, single-photon sensitivity with low probability of false positives and (multi)-megapixels. At DESY, one ongoing development project - in collaboration with RAL/STFC, Elettra Sincrotrone Trieste, Diamond, and Pohang Accelerator Laboratory - is the CMOS-based soft X-ray imager PERCIVAL. PERCIVAL is a monolithic active-pixel sensor back-thinned to access its primary energy range of 250 eV to 1 keV with target efficiencies above 90%. According to preliminary specifications, the roughly 10 cm × 10 cm, 3.5k × 3.7k monolithic sensor will operate at frame rates up to 120 Hz (commensurate with most FELs) and use multiple gains within 27 µm pixels to measure 1 to ∼100000 (500 eV) simultaneously arriving photons. DESY is also leading the development of the AGIPD, a high-speed detector based on hybrid pixel technology intended for use at the European XFEL. This system is being developed in collaboration with PSI, University of Hamburg, and University of Bonn. The AGIPD allows single-pulse imaging at 4.5 MHz frame rate into a 352-frame buffer, with a dynamic range allowing single-photon detection and detection of more than 10000 photons at 12.4 keV in the same image. Modules of 65k pixels each are configured to make up (multi)megapixel cameras. This review describes the AGIPD and the PERCIVAL concepts and systems, including some recent results and a summary of their current status. It also gives a short overview over other FEL-relevant developments where the Photon Science Detector Group at DESY is involved.

Introduction: The Informed Consent allows the person invited to participate of a research project to understand the procedures, risks, discomforts, benefits and rights involved; determining an autonomic decision. We want to verify in the informed consent process the adequacy of given information to research subjects in a collective way., Methods: A research project was chosen from the gynecologic area. The collective obtainment consisted of an oral presentation. After that, The Consent form was shown. Forty-five patients were interviewed, immediately after the consent obtainment., Results: Remembrance capacity of information about procedures, risks and benefits explained were verified. All participants (100%) remembered the procedures, 54% of them remembered the risks and 96% the probable benefits. Comparing these data with others from a similar study using conventional informed consent process (individual information transmission) the subjects remember more information in the present study., Conclusion: These results evidence the possibility to inform collectively the research subjects when getting the Informed Consent in those projects where this choice is available.

The effectiveness of different copolyimide membranes in the process of recovering phenol from water by pervaporation has been investigated. The polyimides were obtained by the polycondensation of 6FDA (4,4'-hexafluoro-isopropylidene diphthalic anhydride) with different diamines. The diamines 4 MPD (2,3,5,6-tetramethyl-1,4-phenylene diamine), 6FpDA (4,4'-hexafluoro-isopropylidene dianiline), 6FpODA (4,4'-bis-(4'-aminophenoxyphenyl)-hexafluoropropane), and DABA (3,5-diaminobenzoic acid) as a monomer providing a crosslinkable group, were used. In order to reach chemical stability at high phenol concentrations, the polymer structures were crosslinked with 1,10-decanediol and OFHD (2,2,3,3,4,4,5,5-octafluorohexanediol). Pervaporation experiments were performed at 60 degrees C, covering a concentration range of phenol between 2 and 11 wt.%. The best separation characteristics were obtained with a 6FDA-6FpDA/DABA 2:1 membrane crosslinked with 1,10-decanediol. Using a 7.8 wt.% phenol feed mixture, a total flux of 14 kg microns m-2 h-1 was reached with an enrichment of 40 wt.% phenol in the permeate. It was found that conditioning the membrane using high phenol concentrations (between 8 and 11 wt.%) is a necessary pretreatment in order to enhance the flux and improve enrichment, especially if process water with low phenol concentrations is to be treated. In addition to the experimental results, a comparison with rubbery membrane materials is presented in the discussion.

For the membrane-based separation of benzene/cyclohexane mixtures, the pervaporation properties of different 6FDA (4,4'-hexafluoroisopropylidene diphthalic anhydride) based copolyimide membranes have been investigated. In order to obtain high permeability as well as high selectivity copolyimides were synthesised using a combination of 4MPD (2,3,5,6-tetramethyl-1,4-phenylene diamine) and 6FpDA (4,4'-hexafluoro-isopropylidene dianiline) as well as DABA (3,5-diaminobenzoic acid) as monomers. Cross-linking is possible with this type of copolyimides and necessary to reduce swelling effects, which often occur with polymeric membranes and lead to a deterioration of the separation characteristics in aromatic/aliphatic separation processes. In order to find the most suitable membrane material, the polymer structure, the crosslinking agents, as well as the crosslinking methods have been varied. The separation characteristics have been determined by sorption and pervaporation experiments. Sorption experiments have been carried out at 60 degrees C using benzene, toluene and ethylbenzene as aromatic components and cyclohexane, cyclohexene, hexane and heptane as aliphatic solvents. Pervaporation experiments have been performed at 60 degrees C using benzene/cyclohexane mixtures with benzene concentrations covering the whole concentration range. It has been found that crosslinked copolyimide membranes show excellent chemical resistance, strongly reduced swelling behaviour and higher selectivity in aromatic/aliphatic separation compared to conventional membrane materials.