Constraints on simulated past Arctic amplification and lapse rate feedback from observations

The Arctic has warmed more rapidly than the global mean during the past few decades. The lapse rate feedback (LRF) has been identified as being a large contributor to the Arctic amplification (AA) of climate change. This particular feedback arises from the vertically non-uniform warming of the troposphere, which in the Arctic emerges as strong near-surface and muted free-tropospheric warming. Stable stratification and meridional energy transport are two characteristic processes that are evoked as causes for this vertical warming structure. Our aim is to constrain these governing processes by making use of detailed observations in combination with the large climate model ensemble of the sixth Coupled Model Intercomparison Project (CMIP6). We build on the result that CMIP6 models show a large spread in AA and Arctic LRF, which are positively correlated for the historical period of 1951–2014. Thus, we present process-oriented constraints by linking characteristics of the current climate to historical climate simulations. In particular, we compare a large consortium of present-day observations to co-located model data from subsets that show a weak and strong simulated AA and Arctic LRF in the past. Our analyses suggest that the vertical temperature structure of the Arctic boundary layer is more realistically depicted in climate models with weak (w) AA and Arctic LRF (CMIP6/w) in the past. In particular, CMIP6/w models show stronger inversions in the present climate for boreal autumn and winter and over sea ice, which is more consistent with the observations. These results are based on observations from the year-long Multidisciplinary Drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition in the central Arctic, long-term measurements at the Utqiaġvik site in Alaska, USA, and dropsonde temperature profiling from aircraft campaigns in the Fram Strait. In addition, the atmospheric energy transport from lower latitudes that can further mediate the warming structure in the free troposphere is more realistically represented by CMIP6/w models. In particular, CMIP6/w models systemically simulate a weaker Arctic atmospheric energy transport convergence in the present climate for boreal autumn and winter, which is more consistent with fifth generation reanalysis of the European Centre for Medium-Range Weather Forecasts (ERA5). We further show a positive relationship between the magnitude of the present-day transport convergence and the strength of past AA. With respect to the Arctic LRF, we find links between the changes in transport pathways that drive vertical warming structures and local differences in the LRF. This highlights the mediating influence of advection on the Arctic LRF and motivates deeper studies to explicitly link spatial patterns of Arctic feedbacks to changes in the large-scale circulation

Atmospheric and Surface Processes, and Feedback Mechanisms Determining Arctic Amplification: A Review of First Results and Prospects of the (AC)3 Project

Mechanisms behind the phenomenon of Arctic amplification are widely discussed. To contribute to this debate, the (AC)3 project has been established in 2016. It comprises modeling and data analysis efforts as well as observational elements. The project has assembled a wealth of ground-based, airborne, ship-borne, and satellite data of physical, chemical, and meteorological properties of the Arctic atmosphere, cryosphere, and upper ocean that are available for the Arctic climate research community. Short-term changes and indications of long-term trends in Arctic climate parameters have been detected using existing and new data

Tethered balloon measurements during Arctic spring conditions in Ny-Ålesund in the framework of HALO-(AC)3

The tethered balloon system BELUGA (BalloonbornE moduLar Utility for profilinG the lower Atmosphere) was operated in spring 2022 at the AWIPEV research station (Ny-Ålesund, Svalbard). In-situ profiles of thermodynamic parameters, thermalinfrared radiation, aerosol particle concentrations, and turbulence, were measured and analyzed. Additionally, samples of ice-nucleating particles were collected at various heights. In combination with previous BELUGA datasets, measurements from this campaign provide a solid base for studying the vertical profiles of the radiative energy budget and heating rates in different atmospheric states in the Arctic lower troposphere. Here, example thermal-infrared radiation profiles are presented for a period of persisting cloudless conditions related to a series of marine cold air outbreaks in late March/early April. Measurements in clouds are analyzed for a developing cloud observed on 6 May and display the impact of cloudiness on radiation profiles.Das Fesselballonsystem BELUGA (BalloonbornE moduLar Utility for profilinG the lowerAtmosphere) wurde im Frühjahr 2022 an der Forschungsstation AWIPEVStation (Ny-Ålesund, Svalbard) eingesetzt. In-situ-Profile von thermodynamischen Parametern, terrestrische Strahlung, Aerosolpartikelkonzentrationen und Turbulenz wurden gemessen und ausgewertet. Zusätzlich wurden in verschiedenen Höhen Proben von eiskeimbildenden Partikeln gesammelt. In Kombination mit früheren BELUGA Messungen zu anderen Jahreszeiten und an anderen arktischen Messstandorten bieten die Messungen in Ny-Ålesund eine Grundlage fürweitereUntersuchungen des Strahlungsenergiehaushalts und des Einflusses vonWolken auf atmosphärische Heizraten. Profile der Strahlungsbilanz werden für eine anhaltende Kälteperiode zwischen Ende März bis Anfang April 2022 vorgestellt. Über diesen Zeitraum herrschten vor allem wolkenlose Bedingungen. Weitere Beobachtungen unter einer sich entwickelnden Wolkendecke am 6. Mai 2022 zeigen den Einfluss der Bewölkung auf die Strahlungsprofile

Tethered balloon measurements during Arctic spring conditions in Ny-Ålesund in the framework of HALO-(AC)3

The tethered balloon system BELUGA (BalloonbornE moduLar Utility for profilinG the lower Atmosphere) was operated in spring 2022 at the AWIPEV research station (Ny-Ålesund, Svalbard). In-situ profiles of thermodynamic parameters, thermalinfrared radiation, aerosol particle concentrations, and turbulence, were measured and analyzed. Additionally, samples of ice-nucleating particles were collected at various heights. In combination with previous BELUGA datasets, measurements from this campaign provide a solid base for studying the vertical profiles of the radiative energy budget and heating rates in different atmospheric states in the Arctic lower troposphere. Here, example thermal-infrared radiation profiles are presented for a period of persisting cloudless conditions related to a series of marine cold air outbreaks in late March/early April. Measurements in clouds are analyzed for a developing cloud observed on 6 May and display the impact of cloudiness on radiation profiles.Das Fesselballonsystem BELUGA (BalloonbornE moduLar Utility for profilinG the lowerAtmosphere) wurde im Frühjahr 2022 an der Forschungsstation AWIPEVStation (Ny-Ålesund, Svalbard) eingesetzt. In-situ-Profile von thermodynamischen Parametern, terrestrische Strahlung, Aerosolpartikelkonzentrationen und Turbulenz wurden gemessen und ausgewertet. Zusätzlich wurden in verschiedenen Höhen Proben von eiskeimbildenden Partikeln gesammelt. In Kombination mit früheren BELUGA Messungen zu anderen Jahreszeiten und an anderen arktischen Messstandorten bieten die Messungen in Ny-Ålesund eine Grundlage fürweitereUntersuchungen des Strahlungsenergiehaushalts und des Einflusses vonWolken auf atmosphärische Heizraten. Profile der Strahlungsbilanz werden für eine anhaltende Kälteperiode zwischen Ende März bis Anfang April 2022 vorgestellt. Über diesen Zeitraum herrschten vor allem wolkenlose Bedingungen. Weitere Beobachtungen unter einer sich entwickelnden Wolkendecke am 6. Mai 2022 zeigen den Einfluss der Bewölkung auf die Strahlungsprofile

The COTUR project: remote sensing of offshore turbulence for wind energy application

The paper presents the measurement strategy and data set collected during the COTUR (COherence of TURbulence with lidars) campaign. This field experiment took place from February 2019 to April 2020 on the southwestern coast of Norway. The coherence quantifies the spatial correlation of eddies and is little known in the marine atmospheric boundary layer. The study was motivated by the need to better characterize the lateral coherence, which partly governs the dynamic wind load on multi-megawatt offshore wind turbines. During the COTUR campaign, the coherence was studied using land-based remote sensing technology. The instrument setup consisted of three long-range scanning Doppler wind lidars, one Doppler wind lidar profiler and one passive microwave radiometer. Both the WindScanner software and LidarPlanner software were used jointly to simultaneously orient the three scanner heads into the mean wind direction, which was provided by the lidar wind profiler. The radiometer instrument complemented these measurements by providing temperature and humidity profiles in the atmospheric boundary layer. The scanning beams were pointed slightly upwards to record turbulence characteristics both within and above the surface layer, providing further insight on the applicability of surface-layer scaling to model the turbulent wind load on offshore wind turbines. The preliminary results show limited variations of the lateral coherence with the scanning distance. A slight increase in the identified Davenport decay coefficient with the height is partly due to the limited pointing accuracy of the instruments. These results underline the importance of achieving pointing errors under 0.1∘ to study properly the lateral coherence of turbulence at scanning distances of several kilometres.publishedVersio