TY - JOUR A1 - Doetterl, Sebastian A1 - Berhe, Asmeret Asefaw A1 - Nadeu, Elisabet A1 - Wang, Zhengang A1 - Sommer, Michael A1 - Fiener, Peter T1 - Erosion, deposition and soil carbon: A review of process-level controls, experimental tools and models to address C cycling in dynamic landscapes JF - Earth science reviews : the international geological journal bridging the gap between research articles and textbooks N2 - The role of soil erosion in terrestrial carbon (C) sequestration and release remains one of the most important uncertainties in our attempts to determine the potential of soils to mediate climate change. Despite its widely recognized importance for terrestrial C sequestration, to date, no Earth System Model (ESM) implements soil erosion effects on carbon cycling in sufficient detail. So far, available studies have mostly investigated the magnitude of erosional C transport and in-situ measurements of vertical C fluxes on the catchment or regional scale. Recognizing the need to adequately represent C erosion processes and controls in ESMs, we provide a comprehensive cross-disciplinary review on lateral C redistribution in the landscape and discuss the implications for bio-geochemical cycling of carbon. We present current knowledge on the role of erosional C distribution in controlling the stabilization and release of C in soils, taking into consideration the important geomorphic, ecological, hydrologic, pedologic and micro-climatic processes and controls that affect soil organic carbon (SOC) stock, fluxes, and persistence in dynamic landscapes. Further, we provide an overview on latest experimental and modelling approaches that are being used to investigate the role of erosion in the carbon cycle. Finally, to advance our understanding of the role of soil redistribution in biogeochemical cycles of essential elements, we discuss the most promising topics for future research in this field. (C) 2015 Elsevier B.V. All rights reserved. KW - Soil erosion KW - Soil deposition KW - Carbon redistribution KW - Terrestrial C sink Y1 - 2016 U6 - https://doi.org/10.1016/j.earscirev.2015.12.005 SN - 0012-8252 SN - 1872-6828 VL - 154 SP - 102 EP - 122 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Wehrhan, Marc A1 - Rauneker, Philipp A1 - Sommer, Michael T1 - UAV-Based Estimation of Carbon Exports from Heterogeneous Soil Landscapes-A Case Study from the CarboZALF Experimental Area JF - SENSORS N2 - The advantages of remote sensing using Unmanned Aerial Vehicles (UAVs) are a high spatial resolution of images, temporal flexibility and narrow-band spectral data from different wavelengths domains. This enables the detection of spatio-temporal dynamics of environmental variables, like plant-related carbon dynamics in agricultural landscapes. In this paper, we quantify spatial patterns of fresh phytomass and related carbon (C) export using imagery captured by a 12-band multispectral camera mounted on the fixed wing UAV Carolo P360. The study was performed in 2014 at the experimental area CarboZALF-D in NE Germany. From radiometrically corrected and calibrated images of lucerne (Medicago sativa), the performance of four commonly used vegetation indices (VIs) was tested using band combinations of six near-infrared bands. The highest correlation between ground-based measurements of fresh phytomass of lucerne and VIs was obtained for the Enhanced Vegetation Index (EVI) using near-infrared band b(899). The resulting map was transformed into dry phytomass and finally upscaled to total C export by harvest. The observed spatial variability at field- and plot-scale could be attributed to small-scale soil heterogeneity in part. KW - VI KW - soil landscape KW - carbon export KW - agriculture KW - multispectral KW - UAV Y1 - 2016 U6 - https://doi.org/10.3390/s16020255 SN - 1424-8220 VL - 16 PB - MDPI CY - Basel ER - TY - GEN A1 - Sommer, Michael A1 - Augustin, Jürgen A1 - Kleber, M. T1 - Feedbacks of soil erosion on SOC patterns and carbon dynamics in agricultural landscapes-The CarboZALF experiment T2 - Journal of real-time image processing Y1 - 2016 U6 - https://doi.org/10.1016/j.still.2015.09.015 SN - 0167-1987 SN - 1879-3444 VL - 156 SP - 182 EP - 184 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Verma, Meetu A1 - Denker, Carsten A1 - Balthasar, H. A1 - Kuckein, Christoph A1 - González Manrique, Sergio Javier A1 - Sobotka, M. A1 - Gonzalez, N. Bello A1 - Hoch, S. A1 - Diercke, Andrea A1 - Kummerow, Philipp A1 - Berkefeld, T. A1 - Collados Vera, M. A1 - Feller, A. A1 - Hofmann, A. A1 - Kneer, F. A1 - Lagg, A. A1 - Löhner-Böttcher, J. A1 - Nicklas, H. A1 - Pastor Yabar, A. A1 - Schlichenmaier, R. A1 - Schmidt, D. A1 - Schmidt, W. A1 - Schubert, M. A1 - Sigwarth, M. A1 - Solanki, S. K. A1 - Soltau, D. A1 - Staude, J. A1 - Strassmeier, Klaus G. A1 - Volkmer, R. A1 - von der Lühe, O. A1 - Waldmann, T. T1 - Horizontal flow fields in and around a small active region The transition period between flux emergence and decay JF - Polymers N2 - Context. The solar magnetic field is responsible for all aspects of solar activity. Thus, emergence of magnetic flux at the surface is the first manifestation of the ensuing solar activity. Aims. Combining high-resolution and synoptic observations aims to provide a comprehensive description of flux emergence at photospheric level and of the growth process that eventually leads to a mature active region. Methods. The small active region NOAA 12118 emerged on 2014 July 17 and was observed one day later with the 1.5-m GREGOR solar telescope on 2014 July 18. High-resolution time-series of blue continuum and G-band images acquired in the blue imaging channel (BIC) of the GREGOR Fabry-Perot Interferometer (GFPI) were complemented by synoptic line-of-sight magnetograms and continuum images obtained with the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO). Horizontal proper motions and horizontal plasma velocities were computed with local correlation tracking (LCT) and the differential affine velocity estimator (DAVE), respectively. Morphological image processing was employed to measure the photometric and magnetic area, magnetic flux, and the separation profile of the emerging flux region during its evolution. Results. The computed growth rates for photometric area, magnetic area, and magnetic flux are about twice as high as the respective decay rates. The space-time diagram using HMI magnetograms of five days provides a comprehensive view of growth and decay. It traces a leaf-like structure, which is determined by the initial separation of the two polarities, a rapid expansion phase, a time when the spread stalls, and a period when the region slowly shrinks again. The separation rate of 0.26 km s(-1) is highest in the initial stage, and it decreases when the separation comes to a halt. Horizontal plasma velocities computed at four evolutionary stages indicate a changing pattern of inflows. In LCT maps we find persistent flow patterns such as outward motions in the outer part of the two major pores, a diverging feature near the trailing pore marking the site of upwelling plasma and flux emergence, and low velocities in the interior of dark pores. We detected many elongated rapidly expanding granules between the two major polarities, with dimensions twice as large as the normal granules. KW - Sun: photosphere KW - Sun: magnetic fields KW - techniques: image processing KW - methods: data analysis Y1 - 2016 U6 - https://doi.org/10.1051/0004-6361/201628380 SN - 1432-0746 VL - 596 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Gonzalez Manrique, Sergio Javier A1 - Kuckein, Christoph A1 - Pastor Yabar, A. A1 - Collados Vera, M. A1 - Denker, Carsten A1 - Fischer, C. E. A1 - Gömöry, P. A1 - Diercke, Andrea A1 - Gonzalez, N. Bello A1 - Schlichenmaier, R. A1 - Balthasar, H. A1 - Berkefeld, T. A1 - Feller, A. A1 - Hoch, S. A1 - Hofmann, A. A1 - Kneer, F. A1 - Lagg, A. A1 - Nicklas, H. A1 - Orozco Suarez, D. A1 - Schmidt, D. A1 - Schmidt, W. A1 - Sigwarth, M. A1 - Sobotka, M. A1 - Solanki, S. K. A1 - Soltau, D. A1 - Staude, J. A1 - Strassmeier, Klaus G. A1 - Verma, Meetu A1 - Volkmer, R. A1 - von der Lühe, O. A1 - Waldmann, T. T1 - Fitting peculiar spectral profiles in He I 10830 angstrom absorption features JF - Astronomische Nachrichten = Astronomical notes N2 - The new generation of solar instruments provides better spectral, spatial, and temporal resolution for a better understanding of the physical processes that take place on the Sun. Multiple-component profiles are more commonly observed with these instruments. Particularly, the He i 10830 triplet presents such peculiar spectral profiles, which give information on the velocity and magnetic fine structure of the upper chromosphere. The purpose of this investigation is to describe a technique to efficiently fit the two blended components of the He i 10830 triplet, which are commonly observed when two atmospheric components are located within the same resolution element. The observations used in this study were taken on 2015 April 17 with the very fast spectroscopic mode of the GREGOR Infrared Spectrograph (GRIS) attached to the 1.5-m GREGOR solar telescope, located at the Observatorio del Teide, Tenerife, Spain. We apply a double-Lorentzian fitting technique using Levenberg-Marquardt least-squares minimization. This technique is very simple and much faster than inversion codes. Line-of-sight Doppler velocities can be inferred for a whole map of pixels within just a few minutes. Our results show sub-and supersonic downflow velocities of up to 32 km s(-1) for the fast component in the vicinity of footpoints of filamentary structures. The slow component presents velocities close to rest. (C) 2016 WILEY-VCH Verlag GmbH& Co. KGaA, Weinheim KW - Sun: chromosphere KW - methods: data analysis KW - techniques: spectroscopic KW - line: profiles Y1 - 2016 U6 - https://doi.org/10.1002/asna.201512433 SN - 0004-6337 SN - 1521-3994 VL - 337 SP - 1057 EP - 1063 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Verma, Meetu A1 - Denker, Carsten A1 - Böhm, F. A1 - Balthasar, H. A1 - Fischer, C. E. A1 - Kuckein, Christoph A1 - Gonzalez, N. Bello A1 - Berkefeld, T. A1 - Collados Vera, M. A1 - Diercke, Andrea A1 - Feller, A. A1 - Gonzalez Manrique, Sergio Javier A1 - Hofmann, A. A1 - Lagg, A. A1 - Nicklas, H. A1 - Orozco Suarez, D. A1 - Pator Yabar, A. A1 - Rezaei, R. A1 - Schlichenmaier, R. A1 - Schmidt, D. A1 - Schmidt, W. A1 - Sigwarth, M. A1 - Sobotka, M. A1 - Solanki, S. K. A1 - Soltau, D. A1 - Staude, J. A1 - Strassmeier, Klaus G. A1 - Volkmer, R. A1 - von der Lühe, O. A1 - Waldmann, T. T1 - Flow and magnetic field properties in the trailing sunspots of active region NOAA 12396 JF - Astronomische Nachrichten = Astronomical notes N2 - Improved measurements of the photospheric and chromospheric three-dimensional magnetic and flow fields are crucial for a precise determination of the origin and evolution of active regions. We present an illustrative sample of multi-instrument data acquired during a two-week coordinated observing campaign in August 2015 involving, among others, the GREGOR solar telescope (imaging and near-infrared spectroscopy) and the space missions Solar Dynamics Observatory (SDO) and Interface Region Imaging Spectrograph (IRIS). The observations focused on the trailing part of active region NOAA 12396 with complex polarity inversion lines and strong intrusions of opposite polarity flux. The GREGOR Infrared Spectrograph (GRIS) provided Stokes IQUV spectral profiles in the photospheric Si i.1082.7 nm line, the chromospheric He I lambda 1083.0 nm triplet, and the photospheric Ca I lambda 1083.9 nm line. Carefully calibrated GRIS scans of the active region provided maps of Doppler velocity and magnetic field at different atmospheric heights. We compare quick-look maps with those obtained with the " Stokes Inversions based on Response functions" (SIR) code, which furnishes deeper insight into the magnetic properties of the region. We find supporting evidence that newly emerging flux and intruding opposite polarity flux are hampering the formation of penumbrae, i.e., a penumbra fully surrounding a sunspot is only expected after cessation of flux emergence in proximity to the sunspots. (C) 2016 WILEY-VCH Verlag GmbH& Co.KGaA, Weinheim KW - Sun: magnetic fields KW - sunspots KW - methods: data analysis KW - techniques: polarimetric KW - techniques: spectroscopic Y1 - 2016 U6 - https://doi.org/10.1002/asna.201612447 SN - 0004-6337 SN - 1521-3994 VL - 337 SP - 1090 EP - 1098 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Martinez Gonzalez, M. J. A1 - Pastor Yabar, A. A1 - Lagg, A. A1 - Asensio Ramos, A. A1 - Collados Vera, M. A1 - Solanki, S. K. A1 - Balthasar, H. A1 - Berkefeld, T. A1 - Denker, Carsten A1 - Doerr, H. P. A1 - Feller, A. A1 - Franz, M. A1 - González Manrique, Sergio Javier A1 - Hofmann, A. A1 - Kneer, F. A1 - Kuckein, Christoph A1 - Louis, R. A1 - von der Lühe, O. A1 - Nicklas, H. A1 - Orozco, D. A1 - Rezaei, R. A1 - Schlichenmaier, R. A1 - Schmidt, D. A1 - Schmidt, W. A1 - Sigwarth, M. A1 - Sobotka, M. A1 - Soltau, D. A1 - Staude, J. A1 - Strassmeier, Klaus G. A1 - Verma, Meetu A1 - Waldman, T. A1 - Volkmer, R. T1 - Inference of magnetic fields in the very quiet Sun JF - Journal of geophysical research : Earth surface N2 - Context. Over the past 20 yr, the quietest areas of the solar surface have revealed a weak but extremely dynamic magnetism occurring at small scales (<500 km), which may provide an important contribution to the dynamics and energetics of the outer layers of the atmosphere. Understanding this magnetism requires the inference of physical quantities from high-sensitivity spectro-polarimetric data with high spatio-temporal resolution. Aims. We present high-precision spectro-polarimetric data with high spatial resolution (0.4") of the very quiet Sun at 1.56 mu m obtained with the GREGOR telescope to shed some light on this complex magnetism. Methods. We used inversion techniques in two main approaches. First, we assumed that the observed profiles can be reproduced with a constant magnetic field atmosphere embedded in a field-free medium. Second, we assumed that the resolution element has a substructure with either two constant magnetic atmospheres or a single magnetic atmosphere with gradients of the physical quantities along the optical depth, both coexisting with a global stray-light component. Results. Half of our observed quiet-Sun region is better explained by magnetic substructure within the resolution element. However, we cannot distinguish whether this substructure comes from gradients of the physical parameters along the line of sight or from horizontal gradients (across the surface). In these pixels, a model with two magnetic components is preferred, and we find two distinct magnetic field populations. The population with the larger filling factor has very weak (similar to 150 G) horizontal fields similar to those obtained in previous works. We demonstrate that the field vector of this population is not constrained by the observations, given the spatial resolution and polarimetric accuracy of our data. The topology of the other component with the smaller filling factor is constrained by the observations for field strengths above 250 G: we infer hG fields with inclinations and azimuth values compatible with an isotropic distribution. The filling factors are typically below 30%. We also find that the flux of the two polarities is not balanced. From the other half of the observed quiet-Sun area similar to 50% are two-lobed Stokes V profiles, meaning that 23% of the field of view can be adequately explained with a single constant magnetic field embedded in a non-magnetic atmosphere. The magnetic field vector and filling factor are reliable inferred in only 50% based on the regular profiles. Therefore, 12% of the field of view harbour hG fields with filling factors typically below 30%. At our present spatial resolution, 70% of the pixels apparently are non-magnetised. KW - Sun: atmosphere KW - Sun: magnetic fields KW - techniques: polarimetric KW - methods: observational Y1 - 2016 U6 - https://doi.org/10.1051/0004-6361/201628449 SN - 1432-0746 VL - 596 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Denker, Carsten A1 - Heibel, C. A1 - Rendtel, J. A1 - Arlt, K. A1 - Balthasar, H. A1 - Diercke, Andrea A1 - Gonzalez Manrique, Sergio Javier A1 - Hofmann, A. A1 - Kuckein, Christoph A1 - Önel, H. A1 - Valliappan, Senthamizh Pavai A1 - Staude, J. A1 - Verma, Meetu T1 - Solar physics at the Einstein Tower JF - Astronomische Nachrichten = Astronomical notes KW - history and philosophy of astronomy KW - Sun: photosphere KW - Sun: magnetic fields KW - techniques: spectroscopic KW - telescopes Y1 - 2016 U6 - https://doi.org/10.1002/asna.201612442 SN - 0004-6337 SN - 1521-3994 VL - 337 SP - 1105 EP - 1113 PB - Wiley-VCH CY - Weinheim ER -