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198 results on '"Dahlke, S"'

1. Continuous Wavelet Frames on the Sphere: The Group-Theoretic Approach Revisited

Author

Dahlke, S., De Mari, F., De Vito, E., Hansen, M., Hasannasab, M., Quellmalz, M., Steidl, G., and Teschke, G.

Subjects
Mathematics - Functional Analysis
Abstract

In \cite{AV99}, Antoine and Vandergheynst propose a group-theoretic approach to continuous wavelet frames on the sphere. The frame is constructed from a single so-called admissible function by applying the unitary operators associated to a representation of the Lorentz group, which is square-integrable modulo the nilpotent factor of the Iwasawa decomposition. We prove necessary and sufficient conditions for functions on the sphere, which ensure that the corresponding system is a frame. We strengthen a similar result in \cite{AV99} by providing a complete and detailed proof.

Published
2020
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3. Extreme drought impacts have been underestimated in grasslands and shrublands globally

Author

Smith, M.D., Wilkins, K.D., Holdrege, M.C., Wilfahrt, P., Collins, S.L., Knapp, A.K., Sala, O.E., Dukes, J.S., Phillips, R.P., Yahdjian, L., Gherardi, L.A., Ohlert, T., Beier, C., Fraser, L.H., Jentsch, A., Loik, M.E., Maestre, F.T., Power, S.A., Yu, Q., Felton, A.J., Munson, S.M., Luo, Y., Abdoli, H., Abedi, M., Alados, C.L., Alberti, J., Alon, M., An, H., Anacker, B., Anderson, M., Auge, Harald, Bachle, S., Bahalkeh, K., Bahn, M., Batbaatar, A., Bauerle, T., Beard, K.H., Behn, K., Beil, I., Biancari, L., Blindow, I., Bondaruk, V.F., Borer, E.T., Bork, E.W., Bruschetti, C.M., Byrne, K.M., Cahill jr., J.F., Calvo, D.A., Carbognani, M., Cardoni, A., Carlyle, C.N., Castillo-Garcia, M., Chang, S.X., Chieppa, J., Cianciaruso, M.V., Cohen, O., Cordeiro, A.L., Cusack, D.F., Dahlke, S., Daleo, P., D'Antonio, C.M., Dietterich, L.H., Doherty, T.S., Dubbert, M., Ebeling, A., Eisenhauer, N., Fischer, F.M., Forte, T.G.W., Gebauer, T., Gozalo, B., Greenville, A.C., Guidoni-Martins, K.G., Hannusch, H.J., Haugum, S.V., Hautier, Y., Hefting, M., Henry, H.A.L., Hoss, D., Ingrisch, J., Iribarne, O., Isbell, F., Johnson, Y., Jordan, S., Kelly, E.F., Kimmel, K., Kreyling, J., Kröel-Dulay, G., Kröpfl, A., Kübert, A., Kulmatiski, A., Lamb, E.G., Steenberg Larsen, K., Larson, J., Lawson, J., Leder, C.V., Linstädter, A., Liu, J., Liu, S., Lodge, A., Longo, G., Smith, M.D., Wilkins, K.D., Holdrege, M.C., Wilfahrt, P., Collins, S.L., Knapp, A.K., Sala, O.E., Dukes, J.S., Phillips, R.P., Yahdjian, L., Gherardi, L.A., Ohlert, T., Beier, C., Fraser, L.H., Jentsch, A., Loik, M.E., Maestre, F.T., Power, S.A., Yu, Q., Felton, A.J., Munson, S.M., Luo, Y., Abdoli, H., Abedi, M., Alados, C.L., Alberti, J., Alon, M., An, H., Anacker, B., Anderson, M., Auge, Harald, Bachle, S., Bahalkeh, K., Bahn, M., Batbaatar, A., Bauerle, T., Beard, K.H., Behn, K., Beil, I., Biancari, L., Blindow, I., Bondaruk, V.F., Borer, E.T., Bork, E.W., Bruschetti, C.M., Byrne, K.M., Cahill jr., J.F., Calvo, D.A., Carbognani, M., Cardoni, A., Carlyle, C.N., Castillo-Garcia, M., Chang, S.X., Chieppa, J., Cianciaruso, M.V., Cohen, O., Cordeiro, A.L., Cusack, D.F., Dahlke, S., Daleo, P., D'Antonio, C.M., Dietterich, L.H., Doherty, T.S., Dubbert, M., Ebeling, A., Eisenhauer, N., Fischer, F.M., Forte, T.G.W., Gebauer, T., Gozalo, B., Greenville, A.C., Guidoni-Martins, K.G., Hannusch, H.J., Haugum, S.V., Hautier, Y., Hefting, M., Henry, H.A.L., Hoss, D., Ingrisch, J., Iribarne, O., Isbell, F., Johnson, Y., Jordan, S., Kelly, E.F., Kimmel, K., Kreyling, J., Kröel-Dulay, G., Kröpfl, A., Kübert, A., Kulmatiski, A., Lamb, E.G., Steenberg Larsen, K., Larson, J., Lawson, J., Leder, C.V., Linstädter, A., Liu, J., Liu, S., Lodge, A., and Longo, G.

Abstract

Climate change is increasing the frequency and severity of short-term (~1 y) drought events—the most common duration of drought—globally. Yet the impact of this intensification of drought on ecosystem functioning remains poorly resolved. This is due in part to the widely disparate approaches ecologists have employed to study drought, variation in the severity and duration of drought studied, and differences among ecosystems in vegetation, edaphic and climatic attributes that can mediate drought impacts. To overcome these problems and better identify the factors that modulate drought responses, we used a coordinated distributed experiment to quantify the impact of short-term drought on grassland and shrubland ecosystems. With a standardized approach, we imposed ~a single year of drought at 100 sites on six continents. Here we show that loss of a foundational ecosystem function—aboveground net primary production (ANPP)—was 60% greater at sites that experienced statistically extreme drought (1-in-100-y event) vs. those sites where drought was nominal (historically more common) in magnitude (35% vs. 21%, respectively). This reduction in a key carbon cycle process with a single year of extreme drought greatly exceeds previously reported losses for grasslands and shrublands. Our global experiment also revealed high variability in drought response but that relative reductions in ANPP were greater in drier ecosystems and those with fewer plant species. Overall, our results demonstrate with unprecedented rigor that the global impacts of projected increases in drought severity have been significantly underestimated and that drier and less diverse sites are likely to be most vulnerable to extreme drought.

Published
2024

5. Induced Crystallization of Polyelectrolyte-Surfactant Complexes at the Gas-Water Interface

Author

Vaknin, D., Dahlke, S., Travesset, A., Nizri, G., and Magdassi, S.

Subjects
Condensed Matter - Soft Condensed Matter, Condensed Matter - Materials Science
Abstract

Synchrotron-X-ray and surface tension studies of a strong polyelectrolyte (PE) in the semi-dilute regime (~ 0.1M monomer-charges) with varying surfactant concentrations show that minute surfactant concentrations induce the formation of a PE-surfactant complex at the gas/solution interface. X-ray reflectivity and grazing angle X-ray diffraction (GIXD) provide detailed information of the top most layer, where it is found that the surfactant forms a two-dimensional liquid-like monolayer, with a noticeable disruption of the structure of water at the interface. With the addition of salt (NaCl) columnar-crystals with distorted-hexagonal symmetry are formed., Comment: 4 pages, 5 eps figures

Published
2004
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6. Atmospheric and Surface Processes, and Feedback Mechanisms Determining Arctic Amplification: A Review of First Results and Prospects of the (AC)3 Project

Author

Wendisch, M., Brückner, M., Crewell, Susanne, Ehrlich, A., Notholt, J., Lüpkes, C., Macke, A., Burrows, J. P., Rinke, A., Quaas, J., Maturilli, M., Schemann, V., Shupe, M. D., Akansu, E. F., Barrientos-Velasco, C., Bärfuss, K., Blechschmidt, A.-M., Block, K., Bougoudis, I., Bozem, H., Böckmann, C., Bracher, A., Bresson, H., Bretschneider, L., Buschmann, M., Chechin, D. G., Chylik, J., Dahlke, S., Deneke, H., Dethloff, K., Donth, T., Dorn, W., Dupuy, R., Ebell, K., Egerer, U., Engelmann, R., Eppers, O., Gerdes, R., Gierens, R., Gorodetskaya, I. V., Gottschalk, M., Griesche, H., Gryanik, V. M., Handorf, D., Harm-Altstädter, B., Hartmann, J., Hartmann, M., Heinold, B., Herber, A., Herrmann, H., Heygster, G., Höschel, I., Hofmann, Z., Hölemann, J., Hünerbein, A., Jafariserajehlou, S., Jäkel, E., Jacobi, C., Janout, M., Jansen, F., Jourdan, O., Jurányi, Z., Kalesse-Los, H., Kanzow, T., Käthner, R., Kliesch, L. L., Klingebiel, M., Knudsen, E. M., Kovács, T., Körtke, W., Krampe, D., Kretzschmar, J., Kreyling, D., Kulla, B., Kunkel, D., Lampert, A., Lauer, M., Lelli, L., von Lerber, A., Linke, O., Löhnert, U., Lonardi, M., Losa, S. N., Losch, M., Maahn, M., Mech, M., Mei, L., Mertes, S., Metzner, E., Mewes, D., Michaelis, J., Mioche, G., Moser, Manuel, Nakoudi, K., Neggers, R., Neuber, R., Nomokonova, T., Oelker, J., Papakonstantinou-Presvelou, I., Pätzold, F., Pefanis, V., Pohl, C., van Pinxteren, M., Radovan, A., Rhein, M., Rex, Markus, Richter, A., Risse, N., Ritter, C., Rostosky, P., Rozanov, V. V., Ruiz Donoso, E., Saavedra-Garfias, P., Salzmann, M., Schacht, J., Schäfer, M., Schneider, J., Schnierstein, N., Seifert, P., Seo, S., Siebert, H., Soppa, M. A., Spreen, G., Stachlewska, I. S., Stapf, J., Stratmann, F., Tegen, I., Viceto, C., Voigt, Christiane, Vountas, M., Walbröl, A., Walter, M., Wehner, B., Wex, H., Willmes, S., Zanatta, M., Zeppenfeld, S., Laboratoire de Météorologie Physique (LaMP), and Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS)

Subjects
Atmospheric Science, [SDU]Sciences of the Universe [physics], clouds, Arctic amplification
Abstract

Mechanisms behind the phenomenon of Arctic amplification are widely discussed. To contribute to this debate, the (AC)3 project was established in 2016 (www.ac3-tr.de/). It comprises modeling and data analysis efforts as well as observational elements. The project has assembled a wealth of ground-based, airborne, shipborne, 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. For example, a distinct atmospheric moistening, an increase of regional storm activities, an amplified winter warming in the Svalbard and North Pole regions, and a decrease of sea ice thickness in the Fram Strait and of snow depth on sea ice have been identified. A positive trend of tropospheric bromine monoxide (BrO) column densities during polar spring was verified. Local marine/biogenic sources for cloud condensation nuclei and ice nucleating particles were found. Atmospheric–ocean and radiative transfer models were advanced by applying new parameterizations of surface albedo, cloud droplet activation, convective plumes and related processes over leads, and turbulent transfer coefficients for stable surface layers. Four modes of the surface radiative energy budget were explored and reproduced by simulations. To advance the future synthesis of the results, cross-cutting activities are being developed aiming to answer key questions in four focus areas: lapse rate feedback, surface processes, Arctic mixed-phase clouds, and airmass transport and transformation.

Published
2023
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8. Atmospheric and Surface Processes, and Feedback Mechanisms Determining Arctic Amplification: A Review of First Results and Prospects of the (AC)3 Project

Author

Wendisch, M, Brückner, M, Crewell, S, Ehrlich, A, Notholt, J, Lüpkes, C, Macke, A, Burrows, JP, Rinke, A, Quaas, J, Maturilli, M, Schemann, V, Shupe, MD, Akansu, EF, Barrientos-Velasco, C, Bärfuss, K, Blechschmidt, A-M, Block, K, Bougoudis, I, Bozem, H, Böckmann, C, Bracher, A, Bresson, H, Bretschneider, L, Buschmann, M, Chechin, DG, Chylik, J, Dahlke, S, Deneke, H, Dethloff, K, Donth, T, Dorn, W, Dupuy, R, Ebell, K, Egerer, U, Engelmann, R, Eppers, O, Gerdes, R, Gierens, R, Gorodetskaya, IV, Gottschalk, M, Griesche, H, Gryanik, VM, Handorf, D, Harm-Altstädter, B, Hartmann, J, Hartmann, M, Heinold, B, Herber, A, Herrmann, H, Heygster, G, Höschel, I, Hofmann, Z, Hölemann, J, Hünerbein, A, Jafariserajehlou, S, Jäkel, E, Jacobi, C, Janout, M, Jansen, F, Jourdan, O, Jurányi, Z, Kalesse-Los, H, Kanzow, T, Käthner, R, Kliesch, LL, Klingebiel, M, Knudsen, EM, Kovács, T, Körtke, W, Krampe, D, Kretzschmar, J, Kreyling, D, Kulla, B, Kunkel, D, Lampert, A, Lauer, M, Lelli, L, von Lerber, A, Linke, O, Löhnert, U, Lonardi, M, Losa, SN, Losch, M, Maahn, M, Mech, M, Mei, L, Mertes, S, Metzner, E, Mewes, D, Michaelis, J, Mioche, G, Moser, M, Nakoudi, K, Neggers, R, Neuber, R, Nomokonova, T, Oelker, J, Papakonstantinou-Presvelou, I, Pätzold, F, Pefanis, V, Pohl, C, van Pinxteren, M, Radovan, A, Rhein, M, Rex, M, Richter, A, Risse, N, Ritter, C, Rostosky, P, Rozanov, VV, Donoso, E Ruiz, Saavedra Garfias, P, Salzmann, M, Schacht, J, Schäfer, M, Schneider, J, Schnierstein, N, Seifert, P, Seo, S, Siebert, H, Soppa, MA, Spreen, G, Stachlewska, IS, Stapf, J, Stratmann, F, Tegen, I, Viceto, C, Voigt, C, Vountas, M, Walbröl, A, Walter, M, Wehner, B, Wex, H, Willmes, S, Zanatta, M, Zeppenfeld, S, Wendisch, M, Brückner, M, Crewell, S, Ehrlich, A, Notholt, J, Lüpkes, C, Macke, A, Burrows, JP, Rinke, A, Quaas, J, Maturilli, M, Schemann, V, Shupe, MD, Akansu, EF, Barrientos-Velasco, C, Bärfuss, K, Blechschmidt, A-M, Block, K, Bougoudis, I, Bozem, H, Böckmann, C, Bracher, A, Bresson, H, Bretschneider, L, Buschmann, M, Chechin, DG, Chylik, J, Dahlke, S, Deneke, H, Dethloff, K, Donth, T, Dorn, W, Dupuy, R, Ebell, K, Egerer, U, Engelmann, R, Eppers, O, Gerdes, R, Gierens, R, Gorodetskaya, IV, Gottschalk, M, Griesche, H, Gryanik, VM, Handorf, D, Harm-Altstädter, B, Hartmann, J, Hartmann, M, Heinold, B, Herber, A, Herrmann, H, Heygster, G, Höschel, I, Hofmann, Z, Hölemann, J, Hünerbein, A, Jafariserajehlou, S, Jäkel, E, Jacobi, C, Janout, M, Jansen, F, Jourdan, O, Jurányi, Z, Kalesse-Los, H, Kanzow, T, Käthner, R, Kliesch, LL, Klingebiel, M, Knudsen, EM, Kovács, T, Körtke, W, Krampe, D, Kretzschmar, J, Kreyling, D, Kulla, B, Kunkel, D, Lampert, A, Lauer, M, Lelli, L, von Lerber, A, Linke, O, Löhnert, U, Lonardi, M, Losa, SN, Losch, M, Maahn, M, Mech, M, Mei, L, Mertes, S, Metzner, E, Mewes, D, Michaelis, J, Mioche, G, Moser, M, Nakoudi, K, Neggers, R, Neuber, R, Nomokonova, T, Oelker, J, Papakonstantinou-Presvelou, I, Pätzold, F, Pefanis, V, Pohl, C, van Pinxteren, M, Radovan, A, Rhein, M, Rex, M, Richter, A, Risse, N, Ritter, C, Rostosky, P, Rozanov, VV, Donoso, E Ruiz, Saavedra Garfias, P, Salzmann, M, Schacht, J, Schäfer, M, Schneider, J, Schnierstein, N, Seifert, P, Seo, S, Siebert, H, Soppa, MA, Spreen, G, Stachlewska, IS, Stapf, J, Stratmann, F, Tegen, I, Viceto, C, Voigt, C, Vountas, M, Walbröl, A, Walter, M, Wehner, B, Wex, H, Willmes, S, Zanatta, M, and Zeppenfeld, S

Abstract

Mechanisms behind the phenomenon of Arctic amplification are widely discussed. To contribute to this debate, the (AC)3 project was established in 2016 (www.ac3-tr.de/). It comprises modeling and data analysis efforts as well as observational elements. The project has assembled a wealth of ground-based, airborne, shipborne, 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. For example, a distinct atmospheric moistening, an increase of regional storm activities, an amplified winter warming in the Svalbard and North Pole regions, and a decrease of sea ice thickness in the Fram Strait and of snow depth on sea ice have been identified. A positive trend of tropospheric bromine monoxide (BrO) column densities during polar spring was verified. Local marine/biogenic sources for cloud condensation nuclei and ice nucleating particles were found. Atmospheric–ocean and radiative transfer models were advanced by applying new parameterizations of surface albedo, cloud droplet activation, convective plumes and related processes over leads, and turbulent transfer coefficients for stable surface layers. Four modes of the surface radiative energy budget were explored and reproduced by simulations. To advance the future synthesis of the results, cross-cutting activities are being developed aiming to answer key questions in four focus areas: lapse rate feedback, surface processes, Arctic mixed-phase clouds, and airmass transport and transformation.

Published
2023

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

Author

Linke, O., Quaas, J., Baumer, F., Becker, S., Chylik, J., Dahlke, S., Ehrlich, A., Handorf, D., Jacobi, C., Kalesse-Los, H., Lelli, L., Mehrdad, S., Neggers, R., Riebold, J., Saavedra Garfias, P., Schnierstein, N., Shupe, M., Smith, C., Spreen, G., Verneuil, B., Vinjamuri, K., Vountas, M., Wendisch, M., Linke, O., Quaas, J., Baumer, F., Becker, S., Chylik, J., Dahlke, S., Ehrlich, A., Handorf, D., Jacobi, C., Kalesse-Los, H., Lelli, L., Mehrdad, S., Neggers, R., Riebold, J., Saavedra Garfias, P., Schnierstein, N., Shupe, M., Smith, C., Spreen, G., Verneuil, B., Vinjamuri, K., Vountas, M., and Wendisch, M.

Abstract

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 s

Published
2023
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12. Low-level jets over the Arctic Ocean during MOSAiC

Author

López-García, V, Neely, III, RR, Dahlke, S, and Brooks, IM

Subjects
Atmospheric Science, Environmental Engineering, Ecology, Geology, Geotechnical Engineering and Engineering Geology, Oceanography
Abstract

We present an annual characterization of low-level jets (LLJs) over the Arctic Ocean using wind profiles from radiosondes launched during the Multidisciplinary drifting Observatory for the Study of Arctic Climate expedition, from October 2019 through September 2020. Our results show LLJs to be common throughout the entire year, with a mean annual frequency of occurrence of more than 40%, a typical height below 400 m, peaking at 120–180 m, and speed between 6 and 14 m s–1. Jet characteristics show some seasonal variability: During winter and the freeze-up period, they are more common and faster, with an average occurrence of 55% and speeds of 8–16 m s–1, while in summer and the transition period, they have a mean occurrence of 46% and speeds of 6–10 m s–1. They have a similar height all year, with a peak between 120 and 180 m. The ERA5 reanalysis shows a similar frequency of occurrence, but a 75 m high bias in altitude, and a small, 0.28 m s–1, slow bias in speed. The height biases are greater in the transition period, more than 130 m, while the bias in speed is similar all year. Examining jets in ERA5 over the full year and whole Arctic Ocean, we find that the frequency of occurrence depends strongly on both the season and the distance to the sea-ice edge.

Published
2022

14. Overview of the MOSAiC expedition : Atmosphere

Author

Shupe, M. D., Rex, M., Blomquist, B., G. Persson, P. O., Schmale, J., Uttal, T., Althausen, D., Angot, H., Archer, S., Bariteau, L., Beck, I., Bilberry, J., Bucci, S., Buck, C., Boyer, M., Brasseur, Z., Brooks, I. M., Calmer, R., Cassano, J., Castro, V., Chu, D., Costa, D., Cox, C. J., Creamean, J., Crewell, S., Dahlke, S., Damm, E., de Boer, G., Deckelmann, H., Dethloff, K., Dütsch, M., Ebell, K., Ehrlich, A., Ellis, J., Engelmann, R., Fong, A. A., Frey, M. M., Gallagher, M. R., Ganzeveld, L., Gradinger, R., Graeser, J., Greenamyer, V., Griesche, H., Griffiths, S., Hamilton, J., Heinemann, G., Helmig, D., Herber, A., Heuzé, C., Hofer, J., Houchens, T., Howard, D., Inoue, J., Jacobi, H. -W, Jaiser, R., Jokinen, T., Jourdan, O., Jozef, G., King, W., Kirchgaessner, A., Klingebiel, M., Krassovski, M., Krumpen, T., Lampert, A., Landing, W., Laurila, T., Lawrence, D., Lonardi, M., Loose, B., Lüpkes, C., Maahn, M., Macke, A., Maslowski, W., Marsay, C., Maturilli, M., Mech, M., Morris, S., Moser, M., Nicolaus, M., Ortega, P., Osborn, J., Pätzold, F., Perovich, D. K., Petäjä, T., Pilz, C., Pirazzini, R., Posman, K., Powers, H., Pratt, K. A., Preußer, A., Quéléver, L., Radenz, M., Rabe, B., Rinke, A., Sachs, T., Schulz, A., Siebert, H., Silva, T., Solomon, A., Sommerfeld, A., Spreen, G., Stephens, M., Stohl, A., Svensson, Gunilla, Uin, J., Viegas, J., Voigt, C., von der Gathen, P., Wehner, B., Welker, J. M., Wendisch, M., Werner, M., Xie, Z., Yue, F., Shupe, M. D., Rex, M., Blomquist, B., G. Persson, P. O., Schmale, J., Uttal, T., Althausen, D., Angot, H., Archer, S., Bariteau, L., Beck, I., Bilberry, J., Bucci, S., Buck, C., Boyer, M., Brasseur, Z., Brooks, I. M., Calmer, R., Cassano, J., Castro, V., Chu, D., Costa, D., Cox, C. J., Creamean, J., Crewell, S., Dahlke, S., Damm, E., de Boer, G., Deckelmann, H., Dethloff, K., Dütsch, M., Ebell, K., Ehrlich, A., Ellis, J., Engelmann, R., Fong, A. A., Frey, M. M., Gallagher, M. R., Ganzeveld, L., Gradinger, R., Graeser, J., Greenamyer, V., Griesche, H., Griffiths, S., Hamilton, J., Heinemann, G., Helmig, D., Herber, A., Heuzé, C., Hofer, J., Houchens, T., Howard, D., Inoue, J., Jacobi, H. -W, Jaiser, R., Jokinen, T., Jourdan, O., Jozef, G., King, W., Kirchgaessner, A., Klingebiel, M., Krassovski, M., Krumpen, T., Lampert, A., Landing, W., Laurila, T., Lawrence, D., Lonardi, M., Loose, B., Lüpkes, C., Maahn, M., Macke, A., Maslowski, W., Marsay, C., Maturilli, M., Mech, M., Morris, S., Moser, M., Nicolaus, M., Ortega, P., Osborn, J., Pätzold, F., Perovich, D. K., Petäjä, T., Pilz, C., Pirazzini, R., Posman, K., Powers, H., Pratt, K. A., Preußer, A., Quéléver, L., Radenz, M., Rabe, B., Rinke, A., Sachs, T., Schulz, A., Siebert, H., Silva, T., Solomon, A., Sommerfeld, A., Spreen, G., Stephens, M., Stohl, A., Svensson, Gunilla, Uin, J., Viegas, J., Voigt, C., von der Gathen, P., Wehner, B., Welker, J. M., Wendisch, M., Werner, M., Xie, Z., and Yue, F.

Abstract

With the Arctic rapidly changing, the needs to observe, understand, and model the changes are essential. To support these needs, an annual cycle of observations of atmospheric properties, processes, and interactions were made while drifting with the sea ice across the central Arctic during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition from October 2019 to September 2020. An international team designed and implemented the comprehensive program to document and characterize all aspects of the Arctic atmospheric system in unprecedented detail, using a variety of approaches, and across multiple scales. These measurements were coordinated with other observational teams to explore crosscutting and coupled interactions with the Arctic Ocean, sea ice, and ecosystem through a variety of physical and biogeochemical processes. This overview outlines the breadth and complexity of the atmospheric research program, which was organized into 4 subgroups: atmospheric state, clouds and precipitation, gases and aerosols, and energy budgets. Atmospheric variability over the annual cycle revealed important influences from a persistent large-scale winter circulation pattern, leading to some storms with pressure and winds that were outside the interquartile range of past conditions suggested by long-term reanalysis. Similarly, the MOSAiC location was warmer and wetter in summer than the reanalysis climatology, in part due to its close proximity to the sea ice edge. The comprehensiveness of the observational program for characterizing and analyzing atmospheric phenomena is demonstrated via a winter case study examining air mass transitions and a summer case study examining vertical atmospheric evolution. Overall, the MOSAiC atmospheric program successfully met its objectives and was the most comprehensive atmospheric measurement program to date conducted over the Arctic sea ice. The obtained data will support a broad range of coupled-system s

Published
2022
Full Text
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15. Overview of the MOSAiC expedition:atmosphere

Author

Shupe, M. D. (Matthew D.), Rex, M. (Markus), Blomquist, B. (Byron), Persson, P. O. (P. Ola G.), Schmale, J. (Julia), Uttal, T. (Taneil), Althausen, D. (Dietrich), Angot, H. (Helene), Archer, S. (Stephen), Bariteau, L. (Ludovic), Beck, I. (Ivo), Bilberry, J. (John), Bucci, S. (Silvia), Buck, C. (Clifton), Boyer, M. (Matt), Brasseur, Z. (Zoe), Brooks, I. M. (Ian M.), Calmer, R. (Radiance), Cassano, J. (John), Castro, V. (Vagner), Chu, D. (David), Costa, D. (David), Cox, C. J. (Christopher J.), Creamean, J. (Jessie), Crewell, S. (Susanne), Dahlke, S. (Sandro), Damm, E. (Ellen), de Boer, G. (Gijs), Deckelmann, H. (Holger), Dethloff, K. (Klaus), Duetsch, M. (Marina), Ebell, K. (Kerstin), Ehrlich, A. (Andre), Ellis, J. (Jody), Engelmann, R. (Ronny), Fong, A. A. (Allison A.), Frey, M. M. (Markus M.), Gallagher, M. R. (Michael R.), Ganzeveld, L. (Laurens), Gradinger, R. (Rolf), Graeser, J. (Juergen), Greenamyer, V. (Vernon), Griesche, H. (Hannes), Griffiths, S. (Steele), Hamilton, J. (Jonathan), Heinemann, G. (Guenther), Helmig, D. (Detlev), Herber, A. (Andreas), Heuze, C. (Celine), Hofer, J. (Julian), Houchens, T. (Todd), Howard, D. (Dean), Inoue, J. (Jun), Jacobi, H.-W. (Hans-Werner), Jaiser, R. (Ralf), Jokinen, T. (Tuija), Jourdan, O. (Olivier), Jozef, G. (Gina), King, W. (Wessley), Kirchgaessner, A. (Amelie), Klingebiel, M. (Marcus), Krassovski, M. (Misha), Krumpen, T. (Thomas), Lampert, A. (Astrid), Landing, W. (William), Laurila, T. (Tiia), Lawrence, D. (Dale), Lonardi, M. (Michael), Loose, B. (Brice), Luepkes, C. (Christof), Maahn, M. (Maximilian), Macke, A. (Andreas), Maslowski, W. (Wieslaw), Marsay, C. (Christopher), Maturilli, M. (Marion), Mech, M. (Mario), Morris, S. (Sara), Moser, M. (Manuel), Nicolaus, M. (Marcel), Ortega, P. (Paul), Osborn, J. (Jackson), Paetzold, F. (Falk), Perovich, D. K. (Donald K.), Petäjä, T. (Tuukka), Pilz, C. (Christian), Pirazzini, R. (Roberta), Posman, K. (Kevin), Powers, H. (Heath), Pratt, K. A. (Kerri A.), Preusser, A. (Andreas), Quelever, L. (Lauriane), Radenz, M. (Martin), Rabe, B. (Benjamin), Rinke, A. (Annette), Sachs, T. (Torsten), Schulz, A. (Alexander), Siebert, H. (Holger), Silva, T. (Tercio), Solomon, A. (Amy), Sommerfeld, A. (Anja), Spreen, G. (Gunnar), Stephens, M. (Mark), Stohl, A. (Andreas), Svensson, G. (Gunilla), Uin, J. (Janek), Viegas, J. (Juarez), Voigt, C. (Christiane), von der Gathen, P. (Peter), Wehner, B. (Birgit), Welker, J. M. (Jeffrey M.), Wendisch, M. (Manfred), Werner, M. (Martin), Xie, Z. (ZhouQing), Yue, F. (Fange), Shupe, M. D. (Matthew D.), Rex, M. (Markus), Blomquist, B. (Byron), Persson, P. O. (P. Ola G.), Schmale, J. (Julia), Uttal, T. (Taneil), Althausen, D. (Dietrich), Angot, H. (Helene), Archer, S. (Stephen), Bariteau, L. (Ludovic), Beck, I. (Ivo), Bilberry, J. (John), Bucci, S. (Silvia), Buck, C. (Clifton), Boyer, M. (Matt), Brasseur, Z. (Zoe), Brooks, I. M. (Ian M.), Calmer, R. (Radiance), Cassano, J. (John), Castro, V. (Vagner), Chu, D. (David), Costa, D. (David), Cox, C. J. (Christopher J.), Creamean, J. (Jessie), Crewell, S. (Susanne), Dahlke, S. (Sandro), Damm, E. (Ellen), de Boer, G. (Gijs), Deckelmann, H. (Holger), Dethloff, K. (Klaus), Duetsch, M. (Marina), Ebell, K. (Kerstin), Ehrlich, A. (Andre), Ellis, J. (Jody), Engelmann, R. (Ronny), Fong, A. A. (Allison A.), Frey, M. M. (Markus M.), Gallagher, M. R. (Michael R.), Ganzeveld, L. (Laurens), Gradinger, R. (Rolf), Graeser, J. (Juergen), Greenamyer, V. (Vernon), Griesche, H. (Hannes), Griffiths, S. (Steele), Hamilton, J. (Jonathan), Heinemann, G. (Guenther), Helmig, D. (Detlev), Herber, A. (Andreas), Heuze, C. (Celine), Hofer, J. (Julian), Houchens, T. (Todd), Howard, D. (Dean), Inoue, J. (Jun), Jacobi, H.-W. (Hans-Werner), Jaiser, R. (Ralf), Jokinen, T. (Tuija), Jourdan, O. (Olivier), Jozef, G. (Gina), King, W. (Wessley), Kirchgaessner, A. (Amelie), Klingebiel, M. (Marcus), Krassovski, M. (Misha), Krumpen, T. (Thomas), Lampert, A. (Astrid), Landing, W. (William), Laurila, T. (Tiia), Lawrence, D. (Dale), Lonardi, M. (Michael), Loose, B. (Brice), Luepkes, C. (Christof), Maahn, M. (Maximilian), Macke, A. (Andreas), Maslowski, W. (Wieslaw), Marsay, C. (Christopher), Maturilli, M. (Marion), Mech, M. (Mario), Morris, S. (Sara), Moser, M. (Manuel), Nicolaus, M. (Marcel), Ortega, P. (Paul), Osborn, J. (Jackson), Paetzold, F. (Falk), Perovich, D. K. (Donald K.), Petäjä, T. (Tuukka), Pilz, C. (Christian), Pirazzini, R. (Roberta), Posman, K. (Kevin), Powers, H. (Heath), Pratt, K. A. (Kerri A.), Preusser, A. (Andreas), Quelever, L. (Lauriane), Radenz, M. (Martin), Rabe, B. (Benjamin), Rinke, A. (Annette), Sachs, T. (Torsten), Schulz, A. (Alexander), Siebert, H. (Holger), Silva, T. (Tercio), Solomon, A. (Amy), Sommerfeld, A. (Anja), Spreen, G. (Gunnar), Stephens, M. (Mark), Stohl, A. (Andreas), Svensson, G. (Gunilla), Uin, J. (Janek), Viegas, J. (Juarez), Voigt, C. (Christiane), von der Gathen, P. (Peter), Wehner, B. (Birgit), Welker, J. M. (Jeffrey M.), Wendisch, M. (Manfred), Werner, M. (Martin), Xie, Z. (ZhouQing), and Yue, F. (Fange)

Abstract

With the Arctic rapidly changing, the needs to observe, understand, and model the changes are essential. To support these needs, an annual cycle of observations of atmospheric properties, processes, and interactions were made while drifting with the sea ice across the central Arctic during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition from October 2019 to September 2020. An international team designed and implemented the comprehensive program to document and characterize all aspects of the Arctic atmospheric system in unprecedented detail, using a variety of approaches, and across multiple scales. These measurements were coordinated with other observational teams to explore crosscutting and coupled interactions with the Arctic Ocean, sea ice, and ecosystem through a variety of physical and biogeochemical processes. This overview outlines the breadth and complexity of the atmospheric research program, which was organized into 4 subgroups: atmospheric state, clouds and precipitation, gases and aerosols, and energy budgets. Atmospheric variability over the annual cycle revealed important influences from a persistent large-scale winter circulation pattern, leading to some storms with pressure and winds that were outside the interquartile range of past conditions suggested by long-term reanalysis. Similarly, the MOSAiC location was warmer and wetter in summer than the reanalysis climatology, in part due to its close proximity to the sea ice edge. The comprehensiveness of the observational program for characterizing and analyzing atmospheric phenomena is demonstrated via a winter case study examining air mass transitions and a summer case study examining vertical atmospheric evolution. Overall, the MOSAiC atmospheric program successfully met its objectives and was the most comprehensive atmospheric measurement program to date conducted over the Arctic sea ice. The obtained data will support a broad range of coupled

Published
2022

17. The seasonsal contrast of aerosols that can seed ice formation in central Arctic clouds

Author

Creamean, J., Barry, K., Hill, T., Hume, C., DeMott, P., Shupe, M., Dahlke, S., Willmes, S., Schmale, J., Beck, I., Hoppe, C.J.M., Fong, A.A., Chamberlain, E., Scharien, R., Persson, O., the, MOSAiC field team, Creamean, J., Barry, K., Hill, T., Hume, C., DeMott, P., Shupe, M., Dahlke, S., Willmes, S., Schmale, J., Beck, I., Hoppe, C.J.M., Fong, A.A., Chamberlain, E., Scharien, R., Persson, O., and the, MOSAiC field team

Published
2021

23. Wavelet-based approximations of pointwise bound constraints in Lebesgue and Sobolev spaces.

Author

Dahlke, S and Surowiec, T M

Subjects
SOBOLEV spaces, WAVELETS (Mathematics), FINITE element method, INTERPOLATION, CONSTRAINED optimization
Abstract

Many problems in optimal control, PDE-constrained optimization and constrained variational problems include pointwise bound constraints on the feasible controls and state variables. Most well-known approaches for treating such pointwise inequality constraints in numerical methods rely on finite element discretizations and interpolation arguments. We propose an alternative means of discretizing pointwise bound constraints using a wavelet-based discretization. The main results show that the discrete, approximating sets converge in the sense of Mosco to the original sets. In situations of higher regularity, convergence rates follow immediately from the underlying wavelet theory. The approach exploits the fact that one can easily transform between a given multiscale wavelet representation and single-scale representation with linear complexity. This allows, for example, a direct treatment of variational problems involving fractional operators, without the need for lifting techniques. We demonstrate this fact with several numerical examples of fractional obstacle problems. [ABSTRACT FROM AUTHOR]

Published
2022
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27. Piecewise tensor product wavelet bases by extensions and approximation rates

Author

Chegini, N., Dahlke, S., Friedrich, U., Stevenson, R., and Analysis (KDV, FNWI)

Subjects
Computational Mathematics, Algebra and Number Theory, Applied Mathematics
Abstract

Following [Studia Math., 76(2) (1983), pp. 1-58 and 95-136] by Z. Ciesielski and T. Figiel and [SIAM J. Math. Anal., 31 (1999), pp. 184-230] by W. Dahmen and R. Schneider, by the application of extension operators we construct a basis for a range of Sobolev spaces on a domain $ \Omega $ from corresponding bases on subdomains that form a non-overlapping decomposition. As subdomains, we take hypercubes, or smooth parametric images of those, and equip them with tensor product wavelet bases. We prove approximation rates from the resulting piecewise tensor product basis that are independent of the spatial dimension of $ \Omega $. For two- and three-dimensional polytopes we show that the solution of Poisson type problems satisfies the required regularity condition. The dimension independent rates will be realized numerically in linear complexity by the application of the adaptive wavelet-Galerkin scheme.

Published
2013
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28. Russia’s North Pacific

Author

Dahlke, Sandra, Renner, Andreas, and Beuerle, Benjamin

Subjects
Russia/Soviet Union, Asia-Pacific, Entanglements, Regions, Empire Russland / Sowjetunion, Asien-Pazifik, Verflechtungen, Regionen, Imperium
Abstract

"The series “Russia and the Asia-Pacific” explores political, economic, social, cultural and environmental interactions of the Russian Far East within its Asian-Pacific context as well as with the Russian capital in the past and present. Its first volume addresses from a multidisciplinary perspective notably the following questions: How were and are directives from a centre thousands of kilometers away perceived and implemented by actors in this region? To which extent was and is the centre successful or how did or does it fail in integrating a region as far away from the centre as the Russian Far East in its state structures? How have notions of “centre” and “periphery” changed over time?

Published
2023
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34. Piecewise Tensor Product Wavelet Bases by Extensions and Approximation Rates

Author

Chegini, N.G., Dahlke, S., Friedrich, U., Stevenson, R., Dahmen, W., Griebel, M., Hackbusch, W., Ritter, K., Schneider, R., Schwab, C., Yserentant, H., and Analysis (KDV, FNWI)

Subjects
Algebra, Nonlinear system, Operator (computer programming), Tensor product, Wavelet, Tensor product of Hilbert spaces, Sparse grid, Piecewise, MathematicsofComputing_NUMERICALANALYSIS, Tensor, Mathematics
Abstract

DIn this chapter, we present some of the major results that have been achieved in the context of the DFG-SPP project "Adaptive Wavelet Frame Methods for Operator Equations: Sparse Grids, Vector-Valued Spaces and Applications to Nonlinear Inverse Problems". This project has been concerned with (nonlinear) elliptic and parabolic operator equations on nontrivial domains as well as with related inverse parameter identification problems. One crucial step has been the design of an efficient forward solver. We employed a spatially adaptive wavelet Rothe scheme. The resulting elliptic subproblems have been solved by adaptive wavelet Galerkin schemes based on generalized tensor wavelets that realize dimension-independent approximation rates. In this chapter, we present the construction of these new tensor bases and discuss some numerical experiments.

Published
2014

35. Adaptive Wavelet BEM for Boundary Integral Equations: Theory and Numerical Experiments.

Author

Dahlke, S., Harbrecht, H., Utzinger, M., and Weimar, M.

Subjects
*BOUNDARY element methods, *WAVELETS (Mathematics), *FREDHOLM equations, *OPERATOR equations, *MANIFOLDS (Mathematics)
Abstract

We are concerned with the numerical treatment of boundary integral equations by the adaptive wavelet boundary element method. In particular, we consider the second kind Fredholm integral equation for the double layer potential operator on patchwise smooth manifolds contained in ℝ3. The corresponding operator equations are treated by adaptive implementations that are in complete accordance with the underlying theory. The numerical experiments demonstrate that adaptive methods really pay off in this setting. The observed convergence rates fit together very well with the theoretical predictions based on the Besov regularity of the exact solution. [ABSTRACT FROM AUTHOR]

Published
2018
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39. The $$\alpha $$ -modulation transform: admissibility, coorbit theory and frames of compactly supported functions.

Author

Speckbacher, M., Bayer, D., Dahlke, S., and Balazs, P.

Abstract

The $$\alpha $$ -modulation transform is a time-frequency transform generated by square-integrable representations of the affine Weyl-Heisenberg group modulo suitable subgroups. In this paper we prove new conditions that guarantee the admissibility of a given window function. We also show that the generalized coorbit theory can be applied to this setting, assuming specific regularity of the windows. This then yields canonical constructions of Banach frames and atomic decompositions in $$\alpha $$ -modulation spaces. In particular, we prove the existence of compactly supported (in time domain) vectors that are admissible and satisfy all conditions within the coorbit machinery, which considerably go beyond known results. [ABSTRACT FROM AUTHOR]

Published
2017
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40. A wavelet based numerical method for nonlinear partial differential equations

Author

Dahlke, S., Lindemann, M., Teschke, G., Zhariy, M., Soares, M. J., Cerejeiras, P., Kähler, U., and Universidade do Minho

Subjects
MathematicsofComputing_NUMERICALANALYSIS
Abstract

The purpose of this paper is to present a wavelet–Galerkin scheme for solving nonlinear elliptic partial differential equations. We select as trial spaces a nested sequence of spaces from an appropriate biorthogonal multiscale analysis. This gives rise to a nonlinear discretized system. To overcome the problems of nonlinearity, we apply the machinery of interpolating wavelets to obtain knot oriented quadrature rules. Finally, Newton’s method is applied to approximate the solution in the given ansatz space. The results of some numerical experiments with different biorthogonal systems, confirming the applicability of our scheme, are presented., Instituto de Cooperação Científica e Tecnológica Internacional - Acções Integradas Luso-Alemãs (DAAD/ICCTI) - Projecto DAAD/ICCTI nº 01141.

Published
2003

41. A Wavelet Based Numerical Method for Nonlinear Partial Differential Equations

Author

Soares, Maria Joana, Dahlke, S., and Lindemann, M.

Abstract

This paper is concerned with the numerical treatment of quasilinear elliptic partial differential equations. In order to solve the given equation we propose to use a Galerkin approach, but, in contrast to conventional finite element discretizations, we work with trial spaces that, not only exhibit the usual approximation and good localization properties, but, in addition, lead to expansions of any element in the underlying Hilbert spaces in terms in multiscale or wavelet bases with certain stability properties. Specifically, we select as trial spaces a nested sequence of spaces from an appropriate biorthogonal multiscale analysis. This gives rise to a nonlinear discretized system. To overcome the problems of nonlinearity, we make use of the machinery of interpolating wavelets to obtain knot oriented quadrature rules. Finally, Newton's method is applied to approximate the solution in the given ansatz space. The results of some numerical experiments with different biorthogonal systems, confirming the applicability of our scheme, are presented.

Published
2003
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45. Seasonal study of methane and nitrous oxide in the coastal waters of the southern Baltic Sea

Author

Bange, Hermann W., Dahlke, S., Ramesh, R., Meyer-Reil, L., Rapsomanikis, S., Andreae, M.O., Bange, Hermann W., Dahlke, S., Ramesh, R., Meyer-Reil, L., Rapsomanikis, S., and Andreae, M.O.

Abstract

Atmospheric and dissolved methane (CH4) and nitrous oxide (N2O) were measured in the unique coastal ecosystem of the Bodden waters, including the western Oder estuary, (southern Baltic Sea) during five campaigns between 1994 and 1997. The CH4 saturations, ranging from 105-15 500%, showed great spatial and temporal variability with maximum values in September and minimum values in December. The N2O saturations were in the range of 91-312% with a maximum in March. Enhanced concentrations of both gases were observed only in the western Oder estuary near the mouth of the Peene River. Thus, we conclude that the distributions of CH4 and N2O in the investigated Bodden waters are, directly or indirectly, linked to the Peene River runoff and not to the Oder River. Our estimate of the annual CH4 emissions from the Bodden waters to the atmosphere indicates a significant contribution (c. 17%) to the overall CH4 emissions from the Baltic Sea. In contrast, the Bodden waters represent only a small source for atmospheric N2O. CH4 production rates estimated from sediment slurry experiments revealed a significant spatial variability and indicated that methanogenic activity was related to acetate consumption in the surface sediment layer. Sedimentary CH4 production might depend on different amounts of accumulation of organic material. (C) 1998 Academic Press

Published
1998
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