AS1.11
Orals: Mon, 24 Apr | Room 0.11/12
Between March 15-19th 2022, East Antarctica experienced an unprecedented heatwave with widespread 30-45° C temperature anomalies across the ice sheet. This record-shattering event saw numerous monthly temperature records being broken including a new all-time temperature record of -9.4 °C on March 18th at Concordia station despite March typically being a transition month to the Antarctic coreless winter. The driver for these temperature extremes was an unprecedently intense atmospheric river (AR) advecting heat and moisture deep into the Antarctic interior. The scope of the temperature records spurred a large, diverse collaborative effort to study the heatwave’s meteorological drivers, impacts, and historical climate context using an array of observations, models, and analysis techniques.
From these efforts, we present the following
- Temperature observations and records
- Meteorological drivers including tropically forced Rossby wave activity along with AR and warm conveyor belt dynamics
- Radiative forcing impacts on surface temperatures and inversions
- Surface mass balance impacts
- Discussion of the AR impacts on isotope and cosmic ray measurements from Concordia station
- AR influence on the Conger Ice Shelf disintegration
- Event return time analysis
- Implications on past climate reconstructions
- Future event likelihood from IPSL-CM6 simulations
How to cite: Wille, J. and the East Antarctica heatwave project: The extraordinary March 2022 East Antarctica heatwave, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-8107, https://doi.org/10.5194/egusphere-egu23-8107, 2023.
Northern sections of the Larsen Ice Shelf, eastern Antarctic Peninsula (AP) have experienced dramatic break-up and collapse since the early 1990s due to strong summertime surface melt, linked to strengthened circumpolar westerly winds. Here we show that extreme summertime surface melt and record-high temperature events over the eastern AP and Larsen C Ice Shelf are triggered by deep convection in the central tropical Pacific (CPAC), which produces an elongated cyclonic anomaly across the South Pacific coupled with a strong high pressure anomaly over Drake Passage. Together these atmospheric circulation anomalies transport very warm and moist air to the southwest AP, often in the form of “atmospheric rivers”, producing strong foehn warming and surface melt on the eastern AP and Larsen C Ice Shelf. Therefore, variability in CPAC convection, in addition to the circumpolar westerlies, is a key driver of AP surface mass balance and the occurrence of extreme high temperatures.
How to cite: Clem, K., Bozkurt, D., Kennett, D., King, J., and Turner, J.: Central tropical Pacific convection drives extreme high temperatures and surface melt on the Larsen C Ice Shelf, Antarctic Peninsula, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-10530, https://doi.org/10.5194/egusphere-egu23-10530, 2023.
On the East Antarctic Plateau, in winter, rapid warming events originated by the advection of warm, moist air from lower latitudes, cause the disruption of the stable thermal structure of the atmosphere, and can be linked to the warming of the Plateau region itself. Continuous monitoring of these events can shed light on temperature trends in East Antarctica, trends which are still not clearly defined in terms of origin and amount.
Since the main mechanism acting in the warming events is the strong increase in cloud cover linked to the higher water content of the advected air, for a systematic monitoring of warming phenomena a simultaneous detection of water vapor vertical profile and cloud properties is needed. These two tasks can be both performed through the analysis of spectrally resolved atmospheric downwelling emitted radiances.
The REFIR (Radiation Explorer in the Far Infrared) Fourier transform spectroradiometer was installed at Concordia station, in the Dome C region of the Antarctic Plateau, in December 2011, and it has been performing continuous measurement since then. REFIR measures the downwelling atmospheric radiance in the 100-1500 cm-1 (6.7-100 µm) spectral interval, with a resolution of 0.4 cm-1, and with a repetition rate of about 10 minutes. The measured spectral interval extends from the far infrared, which includes the water vapor rotational band, to the atmospheric window region (8-14 µm), which provides information about the radiative effects of clouds.
A dedicated inversion code was developed to retrieve vertical profiles of water vapor and temperature from the measured emission spectra. The retrieved profiles allow for the monitoring of the evolution of the vertical structure of the troposphere on a 10 minutes timescale, whereas the spectral radiance itself provides, in a more direct way, information on the cloud cover. Therefore, the dataset produced by the REFIR instrument allow us to detect and obtain statistics about warming events in the Dome C region.
How to cite: Bianchini, G., Belotti, C., Di Natale, G., and Palchetti, L.: Exploiting a decadal time-series of spectrally resolved downwelling infrared radiances at Dome C, Antarctica to assess the occurrence of advective warming events, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-1528, https://doi.org/10.5194/egusphere-egu23-1528, 2023.
Observations at the surface in Antarctica have always been challenging, but cloud observations are particularly scarce due to different factors, among which the polar night and lack of instruments and observers. One way to obtain information on cloud cover, and fill the gap, is through broadband radiation measurements thanks to methods based on the effect that clouds have on solar and terrestrial radiation. In this work three different algorithms have been studied and implemented: i) Long et al.[1] method, which exploits global and diffuse shortwave radiation components; ii) Kasten and Czeplak[2], based on global shortwave component alone; iii) APCADA[3] algorithm, which requires longwave downward radiation measurements and meteorological variables data, and is specially chosen as it yields results also at (polar) night. Different methods were selected to adapt to the data available at each site and to cross-check the results. The algorithms are tested on common-time data sets from three different stations: Marambio (64°14’50’’S - 56°37’39’’W), where upward and downward components for shortwave and longwave radiation are measured along with diffuse shortwave radiation; Professor Julio Escudero (62°12’57’’S - 58°57’35’’W) where downward shortwave and longwave radiation data are available; and Concordia (75°05’59’’S - 123°19’57’’E) where data on all components of both solar and terrestrial radiation are collected. Before any computation, data quality control is executed following tests[4] recommended by the Baseline Surface Radiation Network[5], showing good quality for all three data sets. Sky conditions depend on the location of the stations: Marambio and Escudero are coastal sites located on islands on opposite sides of the Antarctic Peninsula where cloudy skies are expected to occur, while Concordia is situated on the East Antarctic Plateau where the sky should be clearer. Such expectations are confirmed by the preliminary results obtained from the tested algorithms, indicating that clouds occur very often with almost scarce clear sky periods at the coastal stations.
Bibliography
[1] Long C. N., Ackerman T. P., Gaustad K. L., and Cole J. N. S. (2006): “Estimation of fractional sky cover from broadband shortwave radiometer measurements”, J. Geophys. Res. 111, doi: 10.1029/2005JD006475
[2] Dürr B. and Philipona R. (2004): “Automatic cloud amount detection by surface longwave downward radiation measurements”, J. Geophys. Res. 109, doi: 10.1029/2003JD004182
[3] Kasten F., Czeplak G. (1980): “Solar and terrestrial radiation dependent on the amount and type of cloud”, Solar Energy 24, doi: 10.1016/0038-092X(80)90391-6
[4] Long and Shi (2008): “An automated quality assessment and control algorithm for surface radiation measurements”, Open Atm. Science J. 2, doi: 10.2174/1874282300802010023
[5] https://bsrn.awi.de/
How to cite: Frangipani, C., Cordero, R., Gulisano, A. M., Lupi, A., Ochoa, H. A., Rowe, P., and Vitale, V.: Cloud cover estimation using different methods exploiting solar radiation measurements at various sites in Antarctica, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-643, https://doi.org/10.5194/egusphere-egu23-643, 2023.
Intense moist intrusions originating from the lower latitudes of the Pacific Ocean have been found to have a significant impact on the Antarctic Peninsula (AP), including enhancement of surface melt events, increased runoff, reduction in sea-ice cover and ice shelves destabilization. Clouds play an important role in the surface energy budget during these events and in precipitation formation. Precipitation phase and amounts determine local and regional surface mass and energy budget. Our research focuses on cloud and precipitation microphysical and dynamic characteristics over the AP region, using ground based remote sensing at the Ukrainian Antarctic Station Akademic Vernadsky Moreover, an enhanced radiosonde program was launched during the austral winter at the Vernadsky station as part of the Year of Polar Prediction in the Southern Hemisphere (YOPP-SH) international initiative (May-August 2022). Here we present detailed analysis of one of the Targeted Observing Periods (TOPs) during an intense moisture and heat intrusion affecting the AP.
Although there is a lot of research on the atmospheric processes over the AP region, the local dynamic and microphysical characteristics of clouds and precipitation are still poorly understood and misrepresented in the models due to the lack of direct measurements, particularly in winter.
Further we performed Polar-WRF model simulations, forced by ERA5 reanalysis and configured with Morrison double moment cloud microphysical scheme. The simulations were run at 1-km spatial resolution with 10-minute temporal output centered over the Vernadsky region. Simulation results were verified with precipitation properties derived from Micro Rain Radar-Pro measurements and radiosonde profiles. We found that there is more snow in PolarWRF outputs in comparison to MRR-Pro measurements. Thus it does not represent mixed phased precipitation properly. At the same time Polar WRF shows warm temperature bias compared to radiosounding.
Measurements and model output are used to analyze cloud ice and water particle distribution, thickness and precipitation particle spectra over the Vernadsky station and the AP mountains during the extreme precipitation events in the Antarctic Winter. In overall there were five TOPs over the AP region. However, not all of them were associated with extreme precipitation on Vernadsky station.
Our preliminary results show the importance of the transition between dry and wet snowfall during intense moisture transport events at the AP (particularly remarkable during winter at the location of Vernadsky station). Polar-WRF shows differences in simulating the timing and intensity of such transitions probably related to the biases in temperature profiles influencing the melting layer height.
How to cite: Chyhareva, A., Krakovska, S., Gorodetskaya, I., and Palamarchuk, L.: Cloud and precipitation profiles from observations and Polar-WRF simulations over Vernadsky station (western Antarctic Peninsula) during austral winter 2022, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-667, https://doi.org/10.5194/egusphere-egu23-667, 2023.
Our limited understanding of clouds is a major source of uncertainty in climate sensitivity and climate model projections. The Southern Ocean is the largest region on Earth where climate models present large biases in short and long wave radiation fluxes which in turn affect the representation of sea surface temperatures, sea ice and ultimately large scale circulation in the Southern Hemisphere. Evidence suggests that the poor representation of mixed phase clouds at the micro- and macro scales is responsible for the model biases in this region. The Southern Ocean Clouds (SOC) project is a multi-scale, multi-platform approach with the aim of improving understanding of aerosol and cloud microphysics in this region, and their representation in numerical models.
In February 2022 we installed a suite of instruments at the Rothera research station on the Antarctic peninsula to measure the physical and chemical properties of aerosol, the number concentrations of Cloud Condensation Nuclei and Ice Nucleating Particles, and cloud height and thickness all year round. Here we will report the first observations and statistics of one full year of aerosol and cloud measurements from the Rothera research station.
How to cite: van den Heuvel, F., Lachlan-Cope, T., Witherstone, J., Dyson, J., Squires, F., Smith, D., and Flynn, M.: One year of Aerosol and Cloud measurements in Rothera on the Antarctic Peninsula, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-16007, https://doi.org/10.5194/egusphere-egu23-16007, 2023.
The remoteness of the Antarctic continent has important implications for the microphysical properties of clouds: In particular, the rare abundance of ice-nucleating particles (INP) limits the primary nucleation of ice crystals. Yet, persistent mixed-phase clouds with ice crystal number concentrations of 0.1-1l-1 are still observed in the Arctic and Antarctic. However, the ability of regional climate models to reproduce these mixed-phase clouds remains limited, much like the knowledge about their climatological effects. Thus, we added a module to the regional climate model COSMO-CLM² aimed at improving the parametrisation of the aerosol-cycle, which allows us to prescribe different concentrations of INPs. We examined the model response to different concentrations by running it in an area around the Belgian Princess Elisabeth Station in Dronning Maud Land for one month and with four different concentration settings: The first, corresponding to the low end of INP concentrations we observed at the station, the second, corresponding to the high end of INP concentrations we observed at the station, and the third and fourth, to the low and high end of continental observations. The performance was evaluated by comparing the simulation results with radar and ceilometer observations taken at the station. Finally, we analysed the differences between the four simulations to determine the overall sensitivity of the model to variability in INP concentrations, which allows us to draw conclusions about the importance of accurately simulating processes related to ice nucleation, and about the climatological implications that a change in aerosol concentrations would have.
How to cite: Sauerland, F., Souverijns, N., Possner, A., Wex, H., Van Overmeiren, P., Mangold, A., Van Weverberg, K., and van Lipzig, N.: Simulating the effects of Ice-nucleating particles in Antarctica in COSMO-CLM², EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-14418, https://doi.org/10.5194/egusphere-egu23-14418, 2023.
We do not know the exact pathways through which ice, liquid, cloud dynamics, and aerosols are interacting in clouds while forming snowfall but the involved processes can be identified by their fingerprints on snow particles. The general shape of individual crystals (dendritic, columns, plates) depends on the temperature and moisture conditions during growth from water vapor deposition. Aggregation can be identified when multiple individual particles are combined into a snowflake. Riming describes the freezing of cloud droplets onto the snow particle and can eventually form graupel. In order to exploit these unique fingerprints of cloud microphysical processes, optical in situ observations are required.
The Video In Situ Snowfall Sensor (VISSS) was specifically developed for a campaign in the high Arctic (MOSAiC) to determine particle shape and particle size distributions. Different to other sensors, the VISSS minimizes uncertainties by using two-dimensional high-resolution images, a large measurement volume, and a design limiting the impact of wind. Tracking of particles over multiple frames allows determining fall speed and particle tumbling. The instrument design and software will be released as open-source. Here, we present the design of the instrument, show how particles are detected and tracked and introduce first results from campaigns in the high Arctic (MOSAiC), in the Colorado Rocky Mountains (SAIL), and in and Hyytiälä (Finland).
How to cite: Maahn, M., Maherndl, N., and Steinke, I.: Measuring snowfall properties with the open-source Video In Situ Snowfall Sensor , EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-5075, https://doi.org/10.5194/egusphere-egu23-5075, 2023.
Antarctica, the coldest and driest continent, is home to the largest ice sheet. A common feature of polar regions is the warming associated with snowfall, as moist oceanic air and cloud cover contribute to increase the surface temperature. Consequently, the ice accumulated onto the ice sheet is deposited under unusually warm conditions. Here we use the polar-oriented atmospheric model MAR to study the statistical difference between average and snowfall-weighted temperatures. Most of Antarctica experiences a warming scaling with snowfall, although with strongest warming at sites with usually low accumulation. Heavier snowfalls in winter contribute to cool the snowfall-weighted temperature, but this effect is overwritten by the warming associated with atmospheric perturbations responsible for snowfall, which particularly contrast with the extremely cold conditions in winter. Disturbance in apparent annual temperature cycle and interannual variability may have major implications for water isotopes, which are deposited with snowfall and commonly used for paleo-temperature reconstructions.
How to cite: Servettaz, A., Agosta, C., Kittel, C., and Orsi, A.: Warm Temperature Anomalies Associated with Snowfall in Antarctica, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-901, https://doi.org/10.5194/egusphere-egu23-901, 2023.
Clear indications of the phenomenon of Arctic Amplification include the above-average increase of the near-surface air temperature and the related dramatic retreat of sea ice observed in the last decades. The mechanisms behind these features are widely discussed. Especially the role of clouds and of air mass transports into and out of the Arctic associated with related transformation processes are still poorly understood. Therefore, the HALO-(AC)3 campaign was performed to provide observations of meridional air mass transports and corresponding transformations in a quasi-Lagrangian approach. Three research aircraft equipped with state-of-the-art instrumentation performed measurements over the Arctic ocean and sea ice in March/April 2022. The German High Altitude and Long Range Research Aircraft (HALO), equipped with a comprehensive suite of active and passive remote sensing instruments and dropsondes, was operated from Kiruna, Sweden. The flight pattern covered long distances at high altitudes up to the North Pole probing air masses multiple times on their way into and out of the Arctic. The Polar 5 (remote sensing) and Polar 6 (in-situ) aircraft from the Alfred Wegener Institute operated in the lower troposphere out of Longyearbyen in the lower troposphere over Fram Strait West of Svalbard. Several coordinated flights between the three aircraft were conducted with Polar 6 sampling in-situ aerosol, cloud, and precipitation particles within the boundary layer, Polar 5 observing clouds and precipitation from above roughly at 3 km altitude, and HALO providing the large scale view on the scene following air masses.
The observations cover a major warm air intrusion event with atmospheric river embedded bringing warm and moist air far into the Arctic. Multiple cold air outbreaks were characterized in their initial stage close to the sea ice edge with Polar 5 and 6 and in a quasi-Lagrangian perspective with HALO, which allowed to quantify the air mass transformation by changes of thermodynamic profiles, large scale subsidence, and cloud properties over a period of 24 hours. Single events of high latitude Arctic cirrus and the formation of a polar low are included in the data set. The presentation reports on first results of the campaign by illustrating the capabilities of the multi-aircraft operation.
How to cite: Ehrlich, A., Wendisch, M., Klingebiel, M., Mech, M., Crewell, S., Herber, A., and Lüpkes, C. and the HALO-(AC)3 team: HALO-(AC)3: Airborne Observations of Arctic Clouds in Airmass Transformations, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-7246, https://doi.org/10.5194/egusphere-egu23-7246, 2023.
Multilayer clouds (MLCs), defined as individual, vertically overlapping clouds, are frequently occurring worldwide but have been far less studied than single layered clouds. Earlier studies have suggested a clear abundance of MLCs in the Arctic compared with the rest of the world and with data from the MOSAiC campaign in 2019-2020 we have classified multilayered clouds at a 52% frequency of occurrence. The microphysical interaction between these cloud layers is expected to be complicated, such as the seeder- feeder mechanism, and we thus employ a model to further investigate these clouds.
Cases from the MOCCHA campaign in 2018 as well as the MOSAiC campaign in 2019-2020 have been selected for MLC occurrences. These cloud systems vary from vertically distinct layers with no potential of seeding (subsaturated layer of >3km) to a doubly layered system within the boundary layer with frequent seeding events. The structure of the former can be simulated at a coarse grid spacing, provided appropriate initial conditions and aerosol concentration, whilst the latter is highly dependent on initial and boundary conditions, resolution, and parameterisation for the boundary layer.
Together with an analysis of the measurements on board of the ships, the ICON (ICOsahedral Non-hydrostatic) model was deployed. The simulations are run with refined nests down to 75 meters horizontal grid spacing in ICON-LEM. Initial and boundary data are supplied by both ICON Global and IFS. As the Arctic aerosol contribution is yet to be parameterised, we are further making use of the prognostic aerosol module ART (Aerosol and Reactive Trace gases) developed by KIT, set up specifically for cloud condensation nuclei activation for sea salt and sulfate.
Various sensitivity experiments have been performed on these case studies including (i) sensitivity to microphysical parameters, such as CCN and INP parameterisation and concentration, (ii) sensitivity to horizontal and vertical resolution as well as (iii) initial and boundary condition impacts on resolving the cloud layers. Furthermore, the aerosol concentration has been scaled, in the existing parameterisations in ICON, to represent the measurements on site as well as prognostically run using ICON-ART.
Preliminary results on the modelled multilayer cloud system highlight a high dependency on the initial and boundary data quality as well as domain resolution while the microphysics have a smaller impact on the formation and detailed structure of the multilayer cloud system.
How to cite: Wallentin, G., Hoose, C., Achtert, P., and Tesche, M.: Mixed-phase Multilayer Clouds in the Arctic: A Simulation Study using ICON , EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-5650, https://doi.org/10.5194/egusphere-egu23-5650, 2023.
Variability in the components of the Arctic surface energy budget and the atmospheric boundary layer (ABL) structure are to a large extent controlled by synoptic-scale changes and associated air mass properties. The transition of air masses between the radiatively clear and cloudy states, along with their characteristic surface impacts in radiation and ABL structure, can occur in either direction and on short time scales. In both states as well as during the transition, insufficient model representation of radiative processes and cloud microphysical properties cause biases in numerical weather prediction- and climate models. We employ observations from radiosondes, MET tower, and the ShupeTurner cloud microphysics product, which itself synthesizes a wealth of instruments, for the classification of an event of transition between low-level mixed phase cloud and clear conditions. The observed air mass properties and transition process are compared to ERA5 reanalysis data and output from a simulation of the coupled regional climate model HIRHAM-NAOSIM which applied non-spectral nudging to ERA5 in order to reproduce the observed synoptic-scale changes. The approach highlights the potential of event-based analysis of transformations of cloudy Arctic air masses by confronting models with observations.
How to cite: Dahlke, S., Solbès, A., Shupe, M. D., Cox, C. J., Maturilli, M., Rinke, A., Dorn, W., and Rex, M. D.: Transforming cloudy air masses and surface impacts: a case study confronting MOSAiC observations, reanalyses and coupled model simulations, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-5802, https://doi.org/10.5194/egusphere-egu23-5802, 2023.
Clouds play an important role in the climate system of the Arctic. The interaction of clouds with atmospheric radiation has a significant influence on the radiative energy budget (REB) of the Arctic surface, which is quantified by the surface cloud radiative effect (CRE). Due to the counteraction of the cooling effect of clouds in the solar and their warming effect in the thermal-infrared spectral range, the total CRE depends on a complex interplay of the illumination, surface, thermodynamic, and cloud conditions.
To characterize the CRE for a variety of environmental conditions, broadband radiation measurements were performed during three seasonally distinct airborne campaigns. The flights were conducted over sea ice and open ocean surfaces in the eastern Fram Strait. The analysis focusses on the differences of the CRE with respect to the different campaigns and surface types. It was found that clouds cool the open ocean surface during all campaigns. In contrast, clouds mostly have a warming effect on sea ice–covered surfaces, which neutralizes during mid-summer. Given the seasonal cycle of the sea ice distribution, these results imply a cooling effect of clouds on the surface during the sea ice minimum in late summer and a warming effect during the sea ice maximum in spring in the Fram Strait region. The variability of, e. g., cloud and synoptic conditions causes deviations of the CRE from these statistics. In particular, the study presents the evolution of the CRE during selected cases of warm air intrusions and marine cold air outbreaks.
How to cite: Becker, S., Ehrlich, A., Schäfer, M., and Wendisch, M.: Airborne measurements of the cloud impact on the surface radiative energy budget in the Fram Strait, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-5876, https://doi.org/10.5194/egusphere-egu23-5876, 2023.
The presence of clouds significantly affects Arctic boundary layer dynamics. However, the accessibility of clouds over the Arctic sea ice for in-situ observations is challenging. Measurements from tethered balloon platforms are one option to provide high-resolution data needed for model evaluation.
The tethered balloon system BELUGA (Balloon-bornE moduLar Utility for profilinG the lower Atmosphere) was deployed to profile the boundary layer at the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC), and in Ny-Alesund. A set of scientific payloads for the observation of broadband radiation, turbulence, aerosol particles, and cloud microphysics properties were operated to study the interactions in the cloudy and cloud-free boundary layer.
Measurements obtained under various cloud conditions, including single-layer and multi-layer clouds, are analyzed. Heating rates profiles are calculated to validate radiative transfer simulations and to study the temporal development of the cloud layers.
The in-situ observations display the importance of radiation-induced cloud top cooling in maintaining stratocumulus clouds over the Arctic sea ice. Case studies also indicate how the subsequent turbulent mixing can lead to the entrainment of aerosol particles into the cloud layer.
How to cite: Lonardi, M., Pilz, C., Akansu, E. F., Ehrlich, A., Shupe, M. D., Siebert, H., Wehner, B., and Wendisch, M.: The effect of cloud top cooling on the evolution of the Arctic boundary layer observed by balloon-borne measurements, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-7692, https://doi.org/10.5194/egusphere-egu23-7692, 2023.
In the last decades scientist have noticed that the average global temperature of the Earth has been increasing. Moreover, the arctic is warming significantly faster than the global average, a phenomenon labeled Arctic Amplification. Two atmospheric components contributing to the warming of the atmosphere in the arctic are water vapor and cirrus clouds. Both have an effect on the radiation budget of the atmosphere and more specifically the longwave radiation. A Warm Air Intrusion (WAI) event is defined as the meridional transport of warm, water-vapor-rich airmasses into the arctic. During such events large amounts of water vapor can be transported into the arctic, which also leads to high supersaturations aiding the formation and longevity of cirrus clouds. There is a strong hypothesis that WAI events in the high arctic are becoming more frequent, so it is important to study the effects these events have on the macrophysical and optical properties of cirrus clouds in the arctic.
The HALO-(AC)3 flight campaign was conducted in March/April 2022 with the central goal of studying WAI events in the arctic regions of the Northern Hemisphere. For this campaign the German research aircraft HALO was equipped with remote sensing instrumentation, including the airborne LIDAR system WALES which we use in this study. WALES is a combined water vapor differential absorption and high spectral resolution lidar. It provides water vapor measurements in a 2D field along the flight track. We combine these measurements with ECMWF temperature data and calculate the Relative Humidity with respect to ice (RHi) inside and in the vicinity of cirrus clouds. For each flight we studied the synoptic situation and created two groups: One containing flights were cirrus that formed in arctic airmasses were measured and another were cirrus were measured during WAI events, henceforth arctic cirrus and WAI cirrus respectively. Our main goal is to compare the humidity characteristics inside and in the vicinity of arctic cirrus clouds and WAI cirrus clouds.
For the arctic cirrus we find that 49 % of the in-cloud data points are supersaturated with RHi mostly below the lower threshold for heterogeneous nucleation (low HET). The cloud-free air around these clouds has a supersaturation percentage of 8.5 %. The WAI cirrus are measured in a wider temperature range and also have a significantly higher supersaturation percentage inside as well as in the cloud-free air, 61.7 % and 9.3 % respectively. The majority is again in the low HET regime. Additionally, WAI cirrus are on average geometrically thicker than arctic cirrus. Finally, regarding the vertical distribution of RHi within these clouds we find that WAI cirrus have their highest supersaturations near the cloud top and become gradually subsaturated towards cloud-bottom. On the other hand, arctic cirrus have their highest supersaturations near cloud-middle, with lower supersaturations at cloud-top and subsaturated cloud-bottom.
How to cite: Dekoutsidis, G., Groß, S., and Wirth, M.: The effects of warm air intrusions in the high arctic on cirrus clouds, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-8500, https://doi.org/10.5194/egusphere-egu23-8500, 2023.
Atmospheric water vapor plays an enormously important role in the water cycle and energy budget of the Arctic. Water vapor in the Arctic also participates in many important feedback mechanisms influencing the climate response to forcing agents and the Arctic amplification. In this study, we conduct analysis of atmospheric moisture transport into the Arctic based on reanalysis products and CMIP6 model simulations. We are particularly interested in the episodic atmospheric-river-like features (AR or moisture intrusion) that play an important role in delivering water to the Arctic. Based on the method of using column-integrated meridional vapor transport for characterizing AR events, we find that the mean AR frequency peaks in the Atlantic sector in all seasons except that it’s more zonally widespread in summer. An increasing trend in the Arctic AR frequency in the recent decades identified from ERA5 can be captured by few CMIP6 models. The historical Arctic AR frequency, sea ice concentration and Arctic warming are highly correlated. Atmospheric circulation patterns that drive the interannual and decadal Arctic AR variation contribute substantially to the historical Arctic warming. We also use the Community Earth System Model (CESM), equipped with a water tagging capability, to quantify contributions of surface evaporation within the Arctic versus from lower-latitude regions as a source of water to the Arctic and characterize moisture transport pathways that control the Arctic water vapor distribution.
How to cite: Wang, H., Zhang, R., Zou, Y., Ma, W., Rasch, P., and O'Brien, T.: Atmospheric moisture intrusion into the Arctic: sources, impact, and trends, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-10197, https://doi.org/10.5194/egusphere-egu23-10197, 2023.
Marine cold air outbreaks (MCAOs) are important parts of the high-latitude climate system and are characterised by strong surface fluxes generated by the air-sea temperature gradient. These fluxes promote cloud formation, which can be identified in satellite imagery by the distinct transformation of stratiform cloud 'streets' into a broken field of cumuliform clouds downwind of the outbreak. This evolution of cloud morphology changes the radiative properties of the cloud and therefore is of importance to the surface energy budget.
While the drivers of stratocumulus-to-cumulus transitions have been extensively studied for subtropical clouds, such as aerosols or the sea surface temperature gradient, the factors influencing transitions at higher latitudes are relatively poorly understood. This work uses reanalysis data to create a set of composite trajectories of cold air outbreaks moving off the Arctic ice edge and co-locates these trajectories with data from multiple satellites to generate a unique view of cloud development within cold air outbreaks.
Clouds embedded in MCAOs have distinctive properties relative to clouds following other, more stable trajectories in the region. The initial instability and aerosol environments have distinct impacts on cloud development within outbreaks. The strength of the outbreak has a lasting effect on the magnitude of cloud properties along the trajectory. However, it does not strongly affect the timing of the transition to cumuliform clouds. In contrast, the initial aerosol concentration changes the timing of cloud break-up rather than the size of the cloud response.
How to cite: Murray-Watson, R. and Gryspeerdt, E.: The evolution of clouds in Arctic marine cold air outbreaks, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-13191, https://doi.org/10.5194/egusphere-egu23-13191, 2023.
The Arctic is warming at a faster rate than the rest of the globe. There are both remote and local mechanism identified driving this process. While albedo changes and atmospheric stability happens within in the Arctic, transfer transport processes, both in the ocean and atmosphere, heat and moisture into the Arctic. These processes can be analysed in a Eulerien way, by observing the fluxes through a curtain defining the Arctic or/and by Lagrangian analysis which follows this transport processes all the way from uptake in the mid/high latitudes until the inflow into the Arctic.
We use a Lagrangian Particle Transport model FLEXPART running with ECMWF reanalysis data as well as with data from the norwegian earth system model NorESM, which represents the future climate scenarios until 2100. In this way we investigate the inflow of moisture and energy for the last 50 years, but can also project it in the future by considering the climate model output.
We find that the the transport through the 65N Latitude, defining the Arctic area is highly inhomogenious in space, but has also a distinct seasonal variability. The end of the storm tracks, especially the Northern Atlantic stormtrack show the most important region of inflow. While moisture origins over ocean areas in winter, continental areas in summer act as a source. The patterns in the reanalysis data from ECMWF and in the climate simulations are very similar. Those patterns are stable over time, but intensify in a warming climate.
How to cite: Eckhardt, S., Svendby, T., Steensen, B., Myhre, G., Germundsen, A., and Olivie, D.: Moisture transport into the Arctic in a past and future climate, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-11436, https://doi.org/10.5194/egusphere-egu23-11436, 2023.
Posters on site: Mon, 24 Apr, 14:00–15:45 | Hall X5
Precipitation is a key variable in the hydrological cycle. However, observations of precipitation are quite challenging and even more so in remote locations such as the Arctic. The Arctic is experiencing a rapidly changing climate with a strong increase in near-surface air temperature, known as Arctic Amplification. In particular, the Svalbard archipelago is located in the warmest region of the Arctic and reveals the highest temperature increase (Dahlke and Maturilli, 2017). Such changes also affect the hydrological cycle. For example, climate models reveal a strong increase in precipitation in the Arctic (McCrystall et al., 2021) with rain becoming the most dominant precipitation type (Bitanja and Andry, 2017). Continuous detailed observations, which can also be set in context to satellite products and reanalyses data, are necessary to better understand precipitation and precipitation related processes in the Arctic.
In this study, we make use of the complementary precipitation observations performed as part of the Transregional Collaborative Research Centre on Arctic Amplification TR172 (http://www.ac3-tr.de; Wendisch et al., 2017) at the Arctic research station AWIPEV at Ny-Ålesund, Svalbard, to analyze precipitation characteristics in detail. The observations include an OTT Pluvio2 weighing gauge, an OTT Parsivel2 distrometer and a METEK MRR-2 micro rain radar (MRR). While the Pluvio and the Parsivel provide information on surface precipitation amount and type, the MRR provides information on the vertical structure of precipitation up to a height of 1 km. Measurements are available since spring/summer 2017 allowing for an analysis of more than 4 years of data.
First results show that the yearly precipitation amount based on Pluvio ranges from 306 mm to 552 mm (values are uncorrected for undercatch). Using the one-minute resolved data of Parsivel, precipitation frequency is highly variable within the different months ranging from 0.4 % to 18.8 % with solid precipitation being the most dominant type typically from September to March and liquid precipitation in the months May to August. In addition to monthly and yearly statistics, we will also characterize and analyze in detail the individual precipitation events. One question to be addressed is how much of the precipitation is related to atmospheric rivers (ARs). ARs are long, narrow, and transient corridors of strong horizontal water vapor transport which account for 80-90 % of the poleward moisture transport. Although their occurrence in the Arctic is limited, they are a significant source of rain and snow in the Arctic. Understanding linkages between precipitation and weather events and using observational data to evaluate models and reanalysis in the current climate will aid developing more accurate future predictions.
How to cite: Ebell, K., Buhren, C., Gierens, R., Lauer, M., Chellini, G., Dahlke, S., and Krobot, P.: Multi-year precipitation characteristics based on in-situ and remote sensing observations at the Arctic research site Ny-Ålesund, Svalbard, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-9110, https://doi.org/10.5194/egusphere-egu23-9110, 2023.
Observations of late spring and summer time stratiform clouds over pack ice, marginal sea ice zone and open water during the ACLOUD campaign have shown that relatively high ice particle number concentrations up to 35 L-1 are observed in cases where cloud top temperatures are between -3.8 and -8.7°C. This elevation in ice crystal number can likely be linked with secondary ice production. Simultaneous measurements of ice optical properties showed that a relative low asymmetry parameter between 0.69 and 0.76 can be associated with the mixed-phase cloud ice crystals. The condensed water path is dominated by the liquid phase at the cloud top in most of the studied cases except in one case study of a system with embedded convection where ice extinction exceeded the liquid extinction. Radiative transfer simulations have shown that the ice phase in low-level mixed-phase clouds, otherwise dominated by liquid phase, can also be radiatively important in cases where ice phase contributes to the cloud top extinction. This highlights the importance of an accurate vertical information of ice extinction within Arctic low-level clouds. The results of this study provide an important basis for testing and improving cloud microphysical parameterizations in models in order to accurately predict Arctic warming.
How to cite: Järvinen, E., Nehlert, F., Xu, G., Waitz, F., Mioche, G., Dupuy, R., Jourdan, O., and Schnaiter, M.: Observations of ice optical and microphysical properties in Arctic low-level mixed-phase clouds during ACLOUD, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-9323, https://doi.org/10.5194/egusphere-egu23-9323, 2023.
Among arctic moist air intrusions, atmospheric rivers (ARs) provide substantial moisture transport over long distances poleward. Along their corridors, warm and moist air masses undergo various transformation processes and can cause regional sea ice decline, especially when they induce precipitation as rain. Quantifying the components of the atmospheric moisture budget in arctic ARs is key to elucidate their precipitation efficiency. We close the AR moisture budget by measurements of the High Altitude LOng range research aircraft (HALO) during the recent HALO-(AC)³ campaign (Spring, 2022) in the vicinity of the Fram Start and Arctic ocean.
Our analysis is based on a strong AR event that HALO observed on two consecutive days during the occurrence of a sequence of moist air intrusions mid of March 2022. Dropsondes detect the vertical atmospheric profile and therefrom quantify the integrated water vapour transport (IVT) along AR cross sections. Applying regression methods then allows calculating the divergence of IVT. Since the limited number of dropsondes may deteriorate such calculations, we estimate the arising uncertainties using the ICOsahedral Nonhydrostatic model (ICON) in a storm-resolving configuration. Retrieved moisture profiles from the microwave radiometer (HAMP) further complement the sporadic sonde-based moisture profiles. We use the nadir cloud and precipitation radar mounted aboard HALO to derive precipitation rates along the flight curtains.
As the comparison with ICON suggests, the set of dropsondes to derive the IVT divergence within a reasonable range. The advection of moisture is roughly twice as strong as mass convergence. Both components act on different heights, with convergence dominating in the boundary layer (0-1 km) near the low-level jet, whereas moisture advection is more elevated (1-4 km). The strongest moisture convergence arises in the warm prefrontal AR sector while precipitation dominates slightly westwards in the AR centre. The investigated AR event caused rain over sea-ice with a melting layer up to 1.5 km. While there was less IVT on the second observation day, mean precipitation increased from the first day. Model simulations show that evaporation makes only a small contribution to the budget. Within the ICON simulations, the comparison of precipitation purely based on the along-track radar curtain against that over the entire AR corridor indicates that the along-track curtain captures the mean precipitation intensity of the AR corridor, but misrepresents its spatial variability. However, the HALO devices outperform the ICON simulations in terms of the vertical variability of moisture conversion processes.
How to cite: Dorff, H., Konow, H., Schemann, V., Ori, D., Mech, M., and Ament, F.: Airborne Closure of Moisture Budget inside Arctic Atmospheric Rivers, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-9784, https://doi.org/10.5194/egusphere-egu23-9784, 2023.
Within the framework of (AC)3, four airborne campaigns were conducted in the vicinity of Svalbard to investigate the Arctic airmass transformations during warm air intrusions (WAI) and marine cold air outbreaks (CAO). In this study, we will take a deeper look into the development process of CAOs starting from the marginal sea-ice zone towards the open ocean, using data from active and passive remote sensing instruments. In addition, we will present data from more than 450 dropsondes launched during the HALO-(AC)3 campaign and analyze the development of the vertical profiles along WAIs and CAOs. This is done by using a Lagrangian analysis of the campaign, which delivers same-day and next-day trajectory matches of the HALO flights.
How to cite: Klingebiel, M., Monrad-Krohn, L., Kirbus, B., Mech, M., Ehrlich, A., and Wendisch, M.: Analyzing the development of cold air outbreaks and warm air intrusions based on remote sensing and dropsonde data from (AC)3 campaigns, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-11620, https://doi.org/10.5194/egusphere-egu23-11620, 2023.
The enhanced warming in the Arctic compared to the global mean – a phenomenon called Arctic Amplification - has different effects, including impacts on the hydrological cycle and thus the precipitation. In the Arctic, there are two major sources of moisture leading to increased precipitation formation: The enhanced local evaporation due to the missing insulation due to reduced sea-ice cover and the increased poleward moisture transport which is often associated with atmospheric rivers (ARs).
Previous studies have shown that ARs are a significant source for rain and snow in the Arctic. ARs are dynamically linked to the extratropical cyclones and fronts. Thus, AR-related precipitation can be not only concentrated within the AR itself, but also occur within the cyclone and frontal boundaries. Therefore, we developed a new method to distinguish precipitation within the AR shape and the precipitation related to cyclones and fronts based on ERA5 reanalysis. Thereby, we estimate how much precipitation occurs within AR, cyclone and frontal boundaries, separately and overlapping together. We applied this method for different case studies during two campaigns performed at and around Svalbard within the Collaborative Research Center “Arctic Amplification: Climate Relevant Atmospheric Surface Processes, and Feedback Mechanisms (AC)3”. Differences in the contributions of ARs, cyclones and fronts to the total precipitation could be identified comparing the both campaigns. During the early summer campaign (ACLOUD), precipitation (both rain and snow) was more confined within the AR shapes, especially in the area in which the AR is connected to fronts. In contrast, during the early spring campaign (AFLUX), precipitation (predominantly snow) was more restricted to the cyclone regions without connection to ARs and fronts. Generally, a higher precipitation intensity was found within ARs, especially when they are connected with cyclones and fronts.
In a climatological perspective, we apply this method to the ERA5 reanalysis data (1979 - 2020) to quantify the occurrence and influence of ARs and related cyclones and fronts. For this extended analysis, we consider the whole Arctic. This allows us to analyse the change of precipitation (in terms of type and frequency) related to the different weather systems during the last four decades. Furthermore, we can assess seasonal differences. In summary, we can investigate in which regions ARs, cyclones and fronts have a greater impact and if and how it also depends on different surface types (sea ice, open ocean, and land).
This work is supported by the DFG funded Transregioproject TR 172 “Arctic Amplification (AC)3“.
How to cite: Lauer, M., Rinke, A., Gorodetskaya, I., Sprenger, M., Mech, M., and Crewell, S.: Influence of atmospheric rivers, cyclones and fronts on precipitation in the Arctic – a climatological perspective, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-11951, https://doi.org/10.5194/egusphere-egu23-11951, 2023.
According to satellite-based estimations, a lot of clouds over the Arctic Ocean occur below
2 km. Most information on Arctic low-level clouds come from CloudSat radar measurements.
However, CloudSat lacks a complete representation of low-level clouds because the blind
zone masks the lowest kilometer and the coarse spatial sampling conceals cloud patterns.
Thus, higher resolved observations of cloud characteristics are needed to determine how
the cloud fraction varies close to the ground and how it depends on surface characteristics
and meteorological situation.
Our study investigates the low-level hydrometeor fraction of Arctic clouds over the ocean
using airborne remote sensing measurements by the Microwave Radar/radiometer for Arctic
Clouds (MiRAC) flown on the Polar 5 aircraft. Four campaigns have been conducted in the
vicinity of Svalbard during different seasons: ACLOUD, AFLUX, MOSAiC-ACA, and HALO-
AC3. We convolute the MiRAC radar reflectivity measurements to adapt the fine MiRAC and
coarse CloudSat resolution. The convoluted measurements are compared with the original
airborne observations over all campaigns to investigate the effects of CloudSat’s spatial res-
olution, clutter mask, and sensitivity on the low-level hydrometeor fraction. Measurements
reveal high hydrometeor fractions of up to 60% in the lowest 1.5 km, which CloudSat would
miss due to the blind zone. CloudSat would especially underestimate half of the total pre-
cipitation. During cold air outbreaks, when rolling cloud structures evolve, CloudSat over-
estimates the hydrometeor fraction most. Moreover, CloudSat does not resolve the separate
layers of multilayer clouds but rather merges them because of its coarse vertical resolution.
How to cite: Schirmacher, I., Crewell, S., Lamer, K., Mech, M., and Wendisch, M.: Assessing Arctic low-level clouds and precipitation from above - a radar perspective, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-13124, https://doi.org/10.5194/egusphere-egu23-13124, 2023.
Previous research on arctic clouds has focused on single-layer clouds. However, the occurrence of multi-layer clouds in the Arctic is of importance, since in such systems upper clouds can influence the phase of lower clouds. This is the case when ice crystals fall from above into supercooled liquid water clouds and trigger the formation of mixed-phase clouds.
The aim of our project is to investigate the occurrence of multi-layer clouds and seeding using the combination of radiosonde and cloud radar observations. The focus is on the MOSAiC campaign. In order to classify and interpret the results, previous measurements will be used as well.
During the Arctic Ocean 2018 campaign multi-layer clouds were observed 56% of the time and 48 % showed a likelihood of seeding. Previous satellite studies on multi-layer-clouds showed an occurrence of 11 %. During the MOSAiC campaign multi-layer clouds occurred around 50 % of the time and showed a latitude dependency, with more multi-layer clouds north of 84°N.
How to cite: Achtert, P., Tesche, M., Wallentin, G., and Hoose, C.: Occurrence of multilayer clouds and ice-crystal seeding during the Arctic Ocean 2018 and MOSAiC research campaign , EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-13388, https://doi.org/10.5194/egusphere-egu23-13388, 2023.
Atmospheric Rivers (ARs) are long, narrow atmospheric structures which carry anomalously warm and moist air from lower latitudes into higher latitudes. Therefore, ARs are discussed to contribute to Arctic Amplification due to water vapor feedback and cloud-radiation processes. The detailed impact on the surface energy budget (SEB), however, is not fully understood.
We analyze the impact of ARs on the SEB of an early winter and spring case study, using ERA5 reanalysis data and model output from limited area simulations of ICON (ICON-LAM). Both cases show less energy loss of the surface compared to climatology, especially due to more downward longwave radiation and less upward sensible heat. The effect depends on the surface type, open ocean or sea ice. Next, we provide a climatological perspective on the impact of Atmospheric Rivers on the SEB based on ERA5.
How to cite: Tiedeck, S., Kirbus, B., Lauer, M., Crewell, S., Gorodetskaya, I., and Rinke, A.: Impact of Atmospheric Rivers on the Arctic Surface Energy Budget, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-15022, https://doi.org/10.5194/egusphere-egu23-15022, 2023.
Posters virtual: Mon, 24 Apr, 14:00–15:45 | vHall AS
The projected increase in poleward moisture transport (PMT) towards warmer climate has mainly been linked to the larger moisture holding capacity of warmer air masses. However, the future of interannual fluctuations of PMT and associated driving mechanisms are fairly uncertain. This study demonstrates the extent to which atmospheric rivers (ARs) explain the interannual variability of PMT, as well as related variables such as temperature, precipitation and sea ice. Such linkages help to clarify if extreme precipitation or melt events over Arctic regions are dominantly caused by the occurrence of ARs. A main focus is set on the impact of ARs on Arctic sea ice on interannual timescales, which so far has been poorly studied, and varies from colder to warmer climates.
To robustly study these interannual linkages of ARs and Arctic Climate, we examine Arctic ARs in long climate runs of one present and two future climates (+2°C and +3°C), simulated by the global climate model EC-Earth 2.3. To enhance the significance of the results, three different moisture thresholds were used to detect ARs. Further, the use of additional thresholds relative to the 2°C and 3° warmer climates allowed a distinction between thermodynamic and dynamic processes that lead to changes of ARs from colder to warmer climates. It is found that most PMT variability is driven by ARs, and that the share of ARs which explain moisture transport increases towards warmer climates. We also discuss the role of the position and strength of the jet stream in driving AR variability and highlight the importance of ARs in generating interannual fluctuations of Arctic climate variables such as temperature and precipitation.
How to cite: Kolbe, M., Sonnemans, J., Bintanja, R., van der Linden, E., van der Wiel, K., Whan, K., and Benedict, I.: Impact of Atmospheric Rivers on Poleward Moisture Transport and Arctic Climate on Interannual Timescales, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-6007, https://doi.org/10.5194/egusphere-egu23-6007, 2023.
The regulation of energy transfer by clouds and fog is a key process affecting the climate of the Arctic, a region that exhibits frequent cloud cover and suffers an extreme vulnerability to climate change. Measurements were performed over a whole year at the Zeppelin station, Ny-Ålesund, Svalbard, Norway from October 2019 to October 2020 in the framework of the NASCENT campaign (Ny-Ålesund AeroSol Cloud ExperimeNT). Aiming at a better understanding of the susceptibility of cloud droplet formation, we analyzed particle number size distributions obtained from differential mobility particle sizers and chemical composition derived from filter samples and an aerosol chemical speciation monitor. Combined with updraft velocity information from a wind lidar and an ultrasonic anemometer, the data were used as input parameters for a state-of-the-art cloud droplet formation parameterization to investigate the particle sizes that can activate to cloud droplets, the levels of supersaturation as well as potential cloud droplet formation and its susceptibility to aerosol. We showed that low aerosol levels in fall and early winter led to clouds that are formed under an aerosol-limited regime, while higher particle concentrations centered around the Arctic Haze together with a drop in cloud supersaturation could be linked to periods of updraft velocity-limited cloud formation regime. In the latter case, we observed that the maximum number of cloud droplets forming - also called the limiting droplet number - and the updraft velocity follow a relationship that is universal, as proved by similar studies previously performed in different environments and cloud types. Finally, we successfully performed a droplet closure, proving, for the first time, the ability of our cloud droplet parameterization to predict cloud droplet number not only in liquid clouds but also in mixed-phase clouds with a very high degree of glaciation. This closure suggests that rime splintering may not be significant enough to affect droplet concentrations, which is consistent with previous observations and model simulations.
How to cite: Motos, G., Freitas, G., Georgakaki, P., Wieder, J., Aas, W., Lunder, C., Krejci, R., T. Pasquier, J., Henneberger, J., O. David, R., Mohr, C., Zieger, P., and Nenes, A.: Linking aerosol size distribution and hygroscopicity to cloud droplet formation at an Arctic mountain site, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-13074, https://doi.org/10.5194/egusphere-egu23-13074, 2023.
