The Impact of Lead Patterns on Mean Profiles of Wind, Temperature, and Turbulent Fluxes in the Atmospheric Boundary Layer over Sea Ice

In the polar regions, the atmospheric boundary layer (ABL) characteristics are strongly influenced by convection over leads, which are elongated channels in the sea ice covered ocean. The effects on the ABL depend on meteorological forcing and lead geometry. In non-convection-resolving models, in which several leads of potentially different characteristics might be present in a single grid cell, such surface characteristics and the corresponding ABL patterns are not resolved. Our main goal is to investigate potential implications for such models when these subgrid-scale patterns are not considered appropriately. We performed non-eddy-resolving microscale simulations over five different domains with leads of different widths separated by 100% sea ice. We also performed coarser-resolved simulations over a domain representing a few grid cells of a regional climate model, wherein leads were not resolved but accounted for via a fractional sea ice cover of 91% in each cell. Domain size and mean sea ice concentration were the same in all simulations. Differences in the domain-averaged ABL profiles and patterns of wind, temperature, and turbulent fluxes indicate a strong impact of both the leads and their geometry. Additional evaluations of different turbulence parameterizations show large effects by both gradient-independent heat transport and vertical entrainment

Building a participatory national consensus on wastewater reclamation and reuse in Palestine

Water scarcity is a major constraint for economic and social development and sustainability of the agricultural sector in Palestine. Rapid population growth and increasing dominance of Israeli occupation over the Palestinian water and land resources exacerbate this problem. Wastewater reuse in agriculture is a potential non-conventional water resource that needs better utilization. Our research studied the enabling environment and the political economy of wastewater reclamation and reuse in Palestine. The research team adopted participatory approach that was based on active involvement of all stakeholders in the various phases and activities of this project. The team organized large number of public meetings and national workshops that gathered policy makers as well as representatives of the stakeholder community. The team also implemented a questionnaire survey to study the public perceptions toward wastewater reuse. The research was concluded by a national symposium that gathered more than 200 persons from this community. The major research findings show a national consensus on the importance of wastewater reclamation and reuse in irrigated agriculture. The results show positive knowledge and perceptions of all stakeholders towards reuse of reclaimed wastewater. It also shows that there is a big gap between various institutions related to the subject. It also shows poor collaboration between the academic/research institutions and policy making. The research also emphasizes the importance of onsite systems, especially grey water, for wastewater treatment and reuse as they are low cost and do not require permission of Israeli occupation. The research has a substantial policy impact as it opened opportunities for participatory approaches and dialogue between policy makers and the entire stakeholders’ communit

Parametrization of Turbulent Fluxes over Leads in Sea Ice in a Non-Eddy-Resolving Small-Scale Atmosphere Model

Leads (open-water channels in sea ice) play an important role for surface-atmosphere interactions in the polar regions. Due to large temperature differences between the surface of leads and the near-surface atmosphere, strong turbulent convective plumes are generated with a large impact on the atmospheric boundary layer (ABL). Here, we focus on the effect of lead width on those processes, by means of numerical modeling and turbulence parametrization. We use a microscale atmosphere model in a 2D version resolving the entire convective plume with grid sizes in the range of L/5 where L is the lead width. For the sub-grid scale turbulence, we developed a modified version of an already existing nonlocal parametrization of the lead-generated sensible heat flux including L as parameter. All our simulations represent measured springtime conditions with a neutrally stratified ABL capped by a strong temperature inversion at 300 m height, where the initial temperature difference between the lead surface and the near-surface atmosphere amounts to 20 K. We found that our simulation results obtained with the new approach agree very well with time-averaged results of a large eddy simulation (LES) model for variable lead widths with L ≥ 1 km and different upstream wind speeds. This is a considerable improvement since results obtained with the previous nonlocal approach clearly disagree with the LES results for leads wider than 2 km. In conclusion, considering L as parameter in a nonlocal turbulence parametrization seems to be necessary to study the effect of leads on the polar ABL in non-eddy-resolving small-scale atmosphere models

Unmanned Aerial Systems for Investigating the Polar Atmospheric Boundary Layer—Technical Challenges and Examples of Applications

Unmanned aerial systems (UAS) fill a gap in high-resolution observations of meteorological parameters on small scales in the atmospheric boundary layer (ABL). Especially in the remote polar areas, there is a strong need for such detailed observations with different research foci. In this study, three systems are presented which have been adapted to the particular needs for operating in harsh polar environments: The fixed-wing aircraft M^2AV with a mass of 6 kg, the quadrocopter ALICE with a mass of 19 kg, and the fixed-wing aircraft ALADINA with a mass of almost 25 kg. For all three systems, their particular modifications for polar operations are documented, in particular the insulation and heating requirements for low temperatures. Each system has completed meteorological observations under challenging conditions, including take-off and landing on the ice surface, low temperatures (down to −28 °C), icing, and, for the quadrocopter, under the impact of the rotor downwash. The influence on the measured parameters is addressed here in the form of numerical simulations and spectral data analysis. Furthermore, results from several case studies are discussed: With the M^2AV, low-level flights above leads in Antarctic sea ice were performed to study the impact of areas of open water within ice surfaces on the ABL, and a comparison with simulations was performed. ALICE was used to study the small-scale structure and short-term variability of the ABL during a cruise of RV Polarstern to the 79°N glacier in Greenland. With ALADINA, aerosol measurements of different size classes were performed in Ny-Ålesund, Svalbard, in highly complex terrain. In particular, very small, freshly formed particles are difficult to monitor and require the active control of temperature inside the instruments. The main aim of the article is to demonstrate the potential of UAS for ABL studies in polar environments, and to provide practical advice for future research activities with similar systems

Unmanned Aerial Systems for Investigating the Polar Atmospheric Boundary Layer—Technical Challenges and Examples of Applications

Unmanned aerial systems (UAS) fill a gap in high-resolution observations of meteorological parameters on small scales in the atmospheric boundary layer (ABL). Especially in the remote polar areas, there is a strong need for such detailed observations with different research foci. In this study, three systems are presented which have been adapted to the particular needs for operating in harsh polar environments: The fixed-wing aircraft M2AV with a mass of 6 kg, the quadrocopter ALICE with a mass of 19 kg, and the fixed-wing aircraft ALADINA with a mass of almost 25 kg. For all three systems, their particular modifications for polar operations are documented, in particular the insulation and heating requirements for low temperatures. Each system has completed meteorological observations under challenging conditions, including take-offand landing on the ice surface, low temperatures (down to-28 °C), icing, and, for the quadrocopter, under the impact of the rotor downwash. The influence on the measured parameters is addressed here in the form of numerical simulations and spectral data analysis. Furthermore, results from several case studies are discussed: With the M2AV, low-level flights above leads in Antarctic sea ice were performed to study the impact of areas of open water within ice surfaces on the ABL, and a comparison with simulations was performed. ALICE was used to study the small-scale structure and short-term variability of the ABL during a cruise of RV Polarstern to the 79° N glacier in Greenland. With ALADINA, aerosol measurements of different size classes were performed in Ny-Alesund, Svalbard, in highly complex terrain. In particular, very small, freshly formed particles are difficult to monitor and require the active control of temperature inside the instruments. The main aim of the article is to demonstrate the potential of UAS for ABL studies in polar environments, and to provide practical advice for future research activities with similar systems. © 2020 by the authors

Modelling and parametrization of turbulent convective processes over leads in sea ice

Im Nord- und Südpolarmeer ist das Klimasystem der Erde durch viele unterschiedliche Wechselwirkungsprozesse zwischen Atmosphäre, Ozean und Meereis geprägt. Die Meereisbedeckung spielt dabei durch ihren isolierenden Effekt und dem folglich minimierten Austausch zwischen Ozean und Atmosphäre eine wichtige Rolle. Nichtsdestotrotz, auch in der kalten Jahreszeit mit großflächiger Meereisbedeckung ist ein starker turbulenter Transport von Wärme und Feuchte zwischen dem relativ warmen Ozean hinein in die kalte Atmosphäre möglich, zum Beispiel durch längliche Öffnungen (Rinnen) im Meereis. Der konvektive Transport über Rinnen wird durch starke Temperaturunterschiede verursacht, was zu konvektiven Plumes mit verstärkter Turbulenz und einem starken Einfluss auf die Charakteristika der atmosphärischen Grenzschicht führt. Dieser Einfluss hängt wiederum von der Rinnengeometrie und den meteorologischen Bedingungen ab. Verständnis und Quantifizierung dieser eher kleinskaligen Prozesse sind entscheidend, um Modellergebnisse zu verbessern, was auch die Ergebnisse großskaliger (Klima-)Modelle betrifft. Diese Dissertation beinhaltet eine detaillierte Untersuchung der Strömung über Rinnen, vornehmlich mithilfe von kleinskaliger numerischer Modellierung. Durch die im Modell verwendete Gittergröße können konvektive Plumes aufgelöst werden, nicht jedoch einzelne turbulente Wirbel, was eine Parametrisierung turbulenter Flüsse sowie eine Validierung der zugehörigen Ergebnisse vonnöten macht. Hauptsächlich geht es in dieser Arbeit um die Herleitung einer verbesserten Parametrisierung der turbulenten Flüsse über Rinnen mit verschiedener Breite. Idealisierte und beobachtete Fälle werden unter Verwendung der neuen und bereits existierender Parametrisierungen simuliert und mithilfe von Referenzdaten evaluiert. Des weiteren wird eine vorläufige Studie durchgeführt, mit der mögliche Auswirkungen von kleinskaligen, rinnengenerierten atmosphärischen Prozessen auf größeren Skalen gezeigt werden

Simulations of the boundary layer flow over idealised patterns of leads in sea ice with (non-)lead-resolving applications

The data set consists of model data from simulations of the atmospheric flow over different configurations of leads in sea ice. Leads are elongated channels in sea ice over which strong convection can develop, especially between late autumn and spring due to large spatial temperature differences in that season. Lead-generated convection can considerably influence the structure of the atmospheric boundary layer (ABL), not only on a local but also on a more regional scale. All simulations (18 in total, see Table 1) were carried out with the non-eddy-resolving MEsoscale TRansport And Stream model (METRAS, Schlünzen et al., 2018a, b). Every simulation was forced with the same idealised initial inflow conditions of a springtime ABL typically observed in the polar ocean regions. Hence, the data is not georeferenced and the outputs are given with respect to a Cartesian coordinate system. The simulations refer to six different idealised configurations of leads in sea ice (three runs for each case). All cases consist of different domains downwind of an inflow region over 100% thick sea ice cover. In the vertical direction, the grid spacing is 20m below 350m (ABL height is 300m). The initial inflow conditions are the same in all simulations. These correspond to one of the idealised cases of Michaelis et al. (2020). The latter carried out similar simulations for the flow over individual leads, with METRAS and also with an LES model (LES data: Zhou & Gryschka, 2019). In five cases, the simulations are carried out on a microscale, lead- and convection-resolving grid with 200m horizontal grid spacing. The domains all consist of idealised series of leads, which differ by the width of the leads L (with L = {1, 2, 5, 10}km) and by the distance between the leads. These cases are abbreviated by ENS-1km, ENS-2km, ENS-5km-d20km, ENS-5km-d40km, and ENS-10km (see Table 1 in the data description file and Figure 2 in Michaelis and Lüpkes (2022)). Between the leads, which all have a surface temperature of 270K to represent leads covered by thin, new ice, 100% thick sea ice cover is assumed (250K surface temperature). All configurations in the five cases have been chosen in a way that the domain-averaged sea ice concentration is always the same (approximately 91%). The sixth case should represent a few grid cells of a regional climate model, wherein neither leads nor lead-generated convection is resolved so that the surface topography differs strongly from the previous cases. It is run on a grid with 35km horizontal grid spacing. However, the sea ice concentration prescribed in each surface grid cell is the same as the domain-averaged sea ice concentration used for the lead-resolving simulations. This case is abbreviated by ENS-C, where 'C' hints to climate models. Thus, a comparison of domain-averaged quantities is possible between the high- and coarse-resolution simulation results. For each case, different parametrizations of the subgrid-scale turbulent fluxes have been applied using local and non-local closures. These are described in detail by Michaelis and Lüpkes (2022) in their Table 1. The model output files (see Table 2) consist of results after quasi-stationary conditions had been reached. Data is shown with respect to the distance y from the inflow boundary at y = 0km (equal to the scalar grid point position of the model domains) and for 2D-variables also with respect to the height from the surface at z = 0m. In the vertical direction, two different grid variables are used. Most 2D-output variables (temperature, pressure, wind components) are available on a non-equidistant grid in vertical direction up to the model's top at approximately 9600m. The corresponding vertical coordinate is z. The remaining 2D- output variables (turbulent heat flux, turbulent momentum flux) are available on an equidistant grid in vertical direction (20m spacing) up to a height of approximately 2000m (coordinate z_uni_2000m). A scientific evaluation of the model simulations is given in the corresponding publication Michaelis and Lüpkes (2022). More details on the METRAS model are shown in the model's documentation (Schlünzen et al., 2018a, b)