Modeling urban microclimate : development, implementation and evaluation of new and improved calculation methods for the urban microclimate model ENVI-met

In this dissertation, major developments of the scientifically well-established microclimate model ENVI-met are presented. The new developments are evaluated based on proof-of-concept scenarios as well as by comparisons against measurements. Improvements in the modeling of plants have been undertaken that allow the simulation of the microclimatic benefits and the vitality of plants as an organism. Proof-of-concept simulations and a comparison with measured data showed that due to the improvements of the vegetation model ENVI-met is now capable to accurately model plant-based parameters such as transpiration and leaf area temperatures. Based on the implementation of an isoprene emission model ENVI-met's chemistry model has been extended by isoprene-induced reactions, which lead to changes in the concentration of tropospheric ozone. Proof-of-concept simulations have confirmed the validity of the model. ENVI-met's wall and roof model has been extended by multiple computation nodes, which enable the construction of more complex walls and roofs consisting of different materials. This allows a more accurate calculation of the interior temperature as well as the facade temperatures. Proof-of-concept simulations as well as a comparison of modeled facade temperatures with measurement data from the Fraunhofer Institute for Building Physics Holzkirchen showed very high agreement. The coupling of the larger scale climate model MUKLIMO_3 of the German Meteorological Service with the microscale model ENVI-met has been improved. Simulation results of coupled model runs in simplified model areas showed very promising results. In more complex model areas, however, the discrepancies in the near-ground surface temperatures do not seem to be fully resolved yet.In der Dissertation werden entscheidende Neuerungen des im wissenschaftlichen Bereich etablierten Mikroklimamodells ENVI-met vorgestellt und anhand von Proof-of-Concept-Szenarien sowie mittels von Vergleichen zwischen Messungen und Modellergebnissen evaluiert. Es wurden Verbesserungen bei der Modellierung von Pflanzen vorgenommen, die es erlauben Aussagen über den mikroklimatischen Nutzen sowie die Vitalität von Pflanzen als Organismus zu treffen. Evaluationen im Rahmen von Proof-of-Concept-Simulationen und Vergleiche zu Messdaten konnten zeigen, dass ENVI-met durch die Weiterentwicklungen des Vegetationsmodells im Stande ist pflanzenbasierte Parameter wie Transpirationsraten sowie Blattflächentemperaturen genau zu modellieren. Auf Basis eines neu implementieren Isoprenemissionsmodells wurde ENVI-mets Chemiemodell um isopren-induzierte Reaktionen erweitert, die zu einer Veränderung der Konzentration von troposphärischem Ozon führen. Proof-of-Concept-Simulationen bestätigten die Validität des Modells. ENVI-mets Gebäudemodell wurde um weitere Berechnungsknoten erweitert, die es erlauben, Wände und Dächer aus einer Abfolge verschiedener Materialen zu erstellen. Dies ermöglicht eine exaktere Berechnung der Innenraumtemperatur sowie der Fassadentemperaturen. Proof-of-Concept-Simulationen sowie ein Vergleich mit Messdaten des Fraunhofer Instituts für Bauphysik Holzkirchen zeigten sehr hohe Übereinstimmung. Die Kopplung des größerskaligen Klimamodells MUKLIMO_3 des Deutschen Wetterdienstes mit dem mikroskaligen ENVI-met wurde verbessert. Simulationsergebnisse von gekoppelten Modellläufen in einfachen Modellgebieten zeigten sehr viel versprechende Ergebnisse. In komplexeren Modellgebieten hingegen scheint die Diskrepanz in den bodennahen Temperaturfeldern noch nicht vollends behoben.218 S

Cantor polynomials and some related classes of OPRL

We explore the spectral theory of the orthogonal polynomials associated to the classical Cantor measure and similar singular continuous measures. We prove regularity in the sense of Stahl–Totik with polynomial bounds on the transfer matrix. We present numerical evidence that the Jacobi parameters for this problem are asymptotically almost periodic and discuss the possible meaning of the isospectral torus and the Szegő class in this context

Predictability of Arctic sea ice drift in coupled climate models

Abstract. Skillful sea ice drift forecasts are crucial for scientific mission planning and marine safety. Wind is the dominant driver of ice motion variability, but more slowly varying components of the climate system, in particular ice thickness and ocean currents, bear the potential to render ice drift more predictable than the wind. In this study, we provide the first assessment of Arctic sea ice drift predictability in four coupled general circulation models (GCMs), using a suite of “perfect-model” ensemble simulations. We find the position vector from Lagrangian trajectories of virtual buoys to remain predictable for at least a 90 (45) d lead time for initializations in January (July), reaching about 80 % of the position uncertainty of a climatological reference forecast. In contrast, the uncertainty in Eulerian drift vector predictions reaches the level of the climatological uncertainty within 4 weeks. Spatial patterns of uncertainty, varying with season and across models, develop in all investigated GCMs. For two models providing near-surface wind data (AWI-CM1 and HadGEM1.2), we find spatial patterns and large fractions of the variance to be explained by wind vector uncertainty. The latter implies that sea ice drift is only marginally more predictable than wind. Nevertheless, particularly one of the four models (GFDL-CM3) shows a significant correlation of up to −0.85 between initial ice thickness and target position uncertainty in large parts of the Arctic. Our results provide a first assessment of the inherent predictability of ice motion in coupled climate models; they can be used to put current real-world forecast skill into perspective and highlight the model diversity of sea ice drift predictability. </jats:p

Seasonal changes in urban PM2.5 hotspots and sources from low-cost sensors

PM2.5 concentrations in urban areas are highly variable, both spatially and seasonally. To assess these patterns and the underlying sources, we conducted PM2.5 exposure measurements at the adult breath level (1.6 m) along three ~5 km routes in urban districts of Mainz (Germany) using portable low-cost Alphasense OPC-N3 sensors. The survey took place on five consecutive days including four runs each day (38 in total) in September 2020 and March 2021. While the between sensor accuracy was tested to be good (R2 = 0.98), the recorded PM2.5 values underestimated the official measurement station data by up to 25 µg/m3. The collected data showed no consistent PM2.5 hotspots between September and March. Whereas during the fall, the pedestrian and park areas appeared as hotspots in >60% of the runs, construction sites and a bridge with high traffic intensity stuck out in spring. We considered PM2.5/PM10 ratios to assign anthropogenic emission sources with high apportionment of PM2.5 in PM10 (>0.6), except for the parks (0.24) where fine particles likely originated from unpaved surfaces. The spatial PM2.5 apportionment in PM10 increased from September (0.56) to March (0.76) because of a pronounced cooler thermal inversion accumulating fine particles near ground. Our results showed that highly resolved low-cost measurements can help to identify PM2.5 hotspots and be used to differentiate types of particle sources via PM2.5/PM10 ratios

Best of SIDFEx applications, with a focus on deformation forecasts

Talk at IIICWG-DA workshop in Oslo, presenting the SIDFEx database and selevted highlights, focusing on sea-ice deformation forecast

Availability of vitamin B12 and its lower ligand intermediate α-ribazole impact prokaryotic and protist communities in oceanic systems

Genome analyses predict that the cofactor cobalamin (vitamin B12, called B12 herein) is produced by only one-third of all prokaryotes but almost all encode at least one B12-dependent enzyme, in most cases methionine synthase. This implies that the majority of prokaryotes relies on exogenous B12 supply and interacts with producers. B12 consists of a corrin ring centred around a cobalt ion and the lower ligand 5’6-dimethylbenzimidazole (DMB). It has never been tested whether availability of this pivotal cofactor, DMB or its intermediate α-ribazole affect growth and composition of prokaryotic microbial communities. Here we show that in the subtropical, equatorial and polar frontal Pacific Ocean supply of B12 and α-ribazole enhances heterotrophic prokaryotic production and alters the composition of prokaryotic and heterotrophic protist communities. In the polar frontal Pacific, the SAR11 clade and Oceanospirillales increased their relative abundances upon B12 supply. In the subtropical Pacific, Oceanospirillales increased their relative abundance upon B12 supply as well but also downregulated the transcription of the btuB gene, encoding the outer membrane permease for B12. Surprisingly, Prochlorococcus, known to produce pseudo-B12 and not B12, exhibited significant upregulation of genes encoding key proteins of photosystem I + II, carbon fixation and nitrate reduction upon B12 supply in the subtropical Pacific. These findings show that availability of B12 and α-ribazole affect growth and composition of prokaryotic and protist communities in oceanic systems thus revealing far-reaching consequences of methionine biosynthesis and other B12-dependent enzymatic reactions on a community level

Resource recovery and life cycle assessment in co‐treatment of organic waste substrates for biogas versus incineration value chains in Poland and Norway

Present waste management policies are characterized by some main shifts compared to previous practices; such as increased focus on resources recovery, banning of landfilling of organic waste fractions, waste-to-energy value chains optimization, and environmental life cycle impact optimization. In order to comply with such new policies there is a need for research on methodological and empirical aspects of LCA for value chains for co-treatment and resource recovery from organic waste substrates; including processes from generation, treatment, energy conversion and final use of products and byproducts. This study examines two generic value chains (aiming at what are common solutions) for co-treatment of selected organic waste substrates, converted to energy, in Norway and Poland. The waste substrates that are studied are sewage sludge (46% dry matter), organic fractions of municipal solid waste (27.1%), and fat (26.9), in different combinations of quantity mix. Chemical properties for these substrates are gathered from a newly executed state-of-the-art analysis in addition to comprehensive laboratory experiments to find methane yield characteristics of different co-treatment substrate mix situations. Technologies examined in this study include pretreatment, anaerobic digestion, biogas upgrading to CHP-generation or to biofuel for use in transport, bioresiduals separation or upgrading to compost for use in agriculture or as soil amendment, all as part of an anaerobic route, compared to waste incineration with energy recovery to CHP-generation as alternative to the anaerobic route. Products and byproducts of both treatment options are substituting mineral fertilizers, fossil fuels and electricity grid mixes common of today, by system expansion, to determine possible avoided impacts when comparing alternative technologies. The LCA model is based on input from a feedstock-driven and mass-balance consistent MFA model that estimates the life cycle inventory. This provides increased flexibility and accuracy regarding system and technology assumptions, on the basis of a given set of transfer coefficients and parameters that can be altered according to what value chain and technologies are to be examined. This study presents LCA results from two defined and alternative value chains, based on what are typical assumptions and input variable values for applications in a Norwegian and in a Polish setting. The study account for the differences in technologies and practices in the typical waste systems, the typical energy systems and the typical transportation systems in each country, where the main differences between the two systems are that bioresidual is used as fertilizer in Norway and not in Poland additional to the different electricity mixes. LCA calculations are performed using different mix ratios of incoming waste substrates (sewage sludge, organic waste, fat), and assessing the corresponding energy recovery efficiency, nutrient recovery efficiency, and the associated impacts affected by applied technologies, transport distances, carbon capture potential, as well as estimating direct emissions for CH4, N2O and NH3, according to chosen end-use practices within the systems. The study shows what are the main important system processes and elements and what turn to be the critical variables and assumptions in the LCA modeling. It also gives recommendations for what factors to focus when trying to improve the resource recovery for energy and nutrients and the life-cycle environmental impacts of organic waste-to-energy value chains

Biodegradability of hydrothermally altered deep-sea dissolved organic matter

Deep-sea dissolved organic matter (DOM) constitutes a huge carbon reservoir in the worlds' oceans that – despite its abundance – is virtually unused as a substrate by marine heterotrophs. Heating within hydrothermal systems induces major molecular modifications of deep-sea DOM. Here, we tested the hypothesis that hydrothermal heating of deep-sea DOM enhances bioavailability. Aliquots of DOM extracted from the deep North Pacific (North Equatorial Pacific Intermediate Water; NEqPIW) were re-dissolved in artificial seawater and subjected to temperatures of 100 and 200 °C (40 MPa) using Dickson-type reactors. In agreement with earlier findings we observed a temperature-related drop in dissolved organic carbon (DOC) concentration (−6.1% at 100 °C, −21.0% at 200 °C) that predominantly affected the solid-phase extractable (SPE-DOC) fraction (−18.2% at 100 °C, −51.4% at 200 °C). Fourier-transform ion cyclotron resonance mass spectrometric (FT-ICR-MS) analysis confirmed a temperature-related reduction of average molecular mass, O/C ratios, double bond equivalents (DBE) and a relative increase in aromaticity (AImod). This thermally altered DOM was added (25 μmol L−1 DOC) to deep-water samples from the South West Pacific (Kermadec Arc, RV Sonne / SO253, 32° 37.706′ S | 179° 38.728′ W) and incubated with the prevailing natural microbial community. After 16 days at 4 °C in the dark, prokaryotic cell counts in incubations containing the full spectrum of thermally-degraded DOM (extractable and non-extractable compounds) had increased considerably (on average 21× for DOM100°C and 27× for DOM200°C). In contrast, prokaryotic growth in incubations to which only solid-phase extractable thermally-altered DOM was added was not enhanced compared to control incubations. The experiments demonstrate that temperature-driven degradation of deep-sea recalcitrant DOM within hydrothermal systems turns fractions of it accessible to microbes. The thermally-produced DOM compounds that stimulate microbial growth are not retained on reversed-phase resins (SPE-DOM) and are likely low-molecular mass organic acids. Despite the comprehensive compositional modifications of the solid-phase extractable (SPE-DOM) fraction through heating, it remains inaccessible to microbes at the investigated concentration levels. The microbial incubation resulted in only minor and mostly insignificant overall changes in SPE-DOM molecular composition and concentration