GLORIA

GEOMAR Library Ocean Research Information Access

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    facet.materialart.
    Unknown
    Combining Commercial Microwave Link and Rain Gauge Observations to Estimate Countrywide Precipitation: A Stochastic Reconstruction and Pattern Analysis Approach (2022)
    Details
    Publication Date: 2024-02-28
    Description: Accurate spatiotemporal precipitation quantification is a crucial prerequisite for hydrological analyses. The optimal reconstruction of the spatial distribution, that is, the rainfall patterns, is particularly challenging. In this study, we reconstructed spatial rainfall on a countrywide scale for Germany by combining commercial microwave link and rain gauge observations for a better representation of the variability and spatial structure of rainfall. We further developed and applied the Random‐Mixing‐Whittaker‐Shannon method, enabling the stochastic reconstruction of ensembles of spatial fields via linear combinations of unconditional random fields. The pattern of rainfall objects is evaluated by three performance characteristics, that is, ensemble Structure‐, Amplitude‐, and Location‐error. Precipitation estimates obtained are in good agreement with the gauge‐adjusted weather radar product RADOLAN‐RW of the German Weather Service (DWD) which was used as a reference. Compared to reconstructions by Ordinary Kriging, Random Mixing showed clear advantages in the pattern representation via a five times smaller median structure error.
    Description: Plain Language Summary: Rainfall is commonly measured by dedicated sensors such as rain gauges or weather radars. Commercial microwave links (CMLs), which have the primary purpose of signal forwarding within cellular networks, can be used for rainfall measurements too. The signal, which is transmitted from one antenna to another, is being attenuated if it rains along the path. From the amount of attenuation an average rain rate can be retrieved. For many hydrological applications, it is of major interest to estimate area‐wide rainfall (i.e., rainfall maps) while observations provide only scattered information. In this study, we used the local information from almost 1,000 rain gauges and the information along the paths of 3,900 CMLs distributed over Germany to reconstruct rainfall maps. We did this by applying a method of stochastic simulation (called Random Mixing) which we compared to a more common method of estimation (Ordinary Kriging). To evaluate the quality of the obtained maps, we compared them to rainfall information from weather radars. We found that the general agreement is high, and that maps reconstructed by Random Mixing have particular advantages in representing the spatial structure, that is, the shape of rainfall cells.
    Description: Key Points: Geostatistical Random Mixing simulation now capable of countrywide spatial rainfall interpolation. Variability assessment via commercial microwave link path consideration and ensemble estimation. Realistic rainfall pattern representation quantified by ensemble Structure‐, Amplitude‐, and Location‐error metrics.
    Description: German Research Foundation
    Description: Federal Ministry of Education and Research
    Description: https://doi.org/10.5281/zenodo.4810169
    Description: https://opendata.dwd.de/climate_environment/CDC
    Description: https://maps.dwd.de/geoserver/web/wicket/bookmarkable/org.geoserver.web.demo.SRSDescriptionPage?10 26code=EPSG:1000001
    Description: https://doi.org/10.5281/zenodo.5380342
    Description: https://doi.org/10.5281/zenodo.7048941
    Description: https://doi.org/10.5281/zenodo.7049826
    Description: https://doi.org/10.5281/zenodo.7049846
    Keywords: ddc:551.5 ; precipitation estimation ; geostatistical simulation ; spatial pattern analysis ; commercial microwave links ; rain gauges ; random mixing
    Language: English
    Type: doc-type:article
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 2
    facet.materialart.
    Unknown
    Glacial-interglacial changes of water isotopes (H218O, HDO) 
 as simulated by a fully coupled Earth System Model (2014)
    In:  EPIC3European Geosciences Union General Assembly, Vienna, 2014-04-27-2014-05-02
    Details
    Publication Date: 2014-07-08
    Description: During the past two decades, several atmospheric and oceanic general circulation models (GCMs) have been enhanced by the capability to explicitly simulate the hydrological cycle of the two stable water isotopes H218O and HDO. They have provided a wealth of understanding regarding changes of the water isotope signals in various archives under different past climate conditions. However, so far the number of fully coupled atmosphere-ocean GCMs with explicit water isotope diagnostics is very limited. Such coupled models are required for a more comprehensive simulation of both past climates as well as related isotope changes in the Earth’s hydrological cycle. Here, we report first results of a newly developed isotope diagnostics within the Earth system model ECHAM5-JSBACH/MPIMOM. Both H218O and HDO and their relevant fractionation processes are included in all compartments and branches of the water cycle within this model. First equilibrium simulations have been performed for both pre-industrial (PI) and Last Glacial Maximum (LGM) boundary conditions. Evaluation of the PI simulation reveals a good overall model performance in accordance with available modern isotope data from vapour measurements, precipitation samples as well as marine records. The LGM experiment results in spatially varying isotope depletion in precipitation between -20‰ and 0‰ in agreement with data from various isotope records. The simulated isotopic compoisiton of ccean surface waters shows a strong glacial enrichment in the Arctic. In further model analyses we investigate how the relation between water isotopes and key climate variables, e.g. land and surface temperatures, precipitation amounts, oceanic salinity, might has changed for different regions on a glacial-interglacial time scale. Moreover, the influence of glacial climates changes on second-order isotope signals, e.g. the Deuterium excess, is examined.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER (OA)
  • 3
    facet.materialart.
    Unknown
    Stable water isotopes in the coupled atmosphere-land surface model ECHAM5-JSBACH (2013)
    In:  EPIC3Geoscientific Model Development, 6, pp. 1463-1480
    Details
    Publication Date: 2019-07-17
    Description: In this study we present first results of a new model development, ECHAM5-JSBACH-wiso, where we have incorporated the stable water isotopes H218O and HDO as tracers in the hydrological cycle of the coupled atmosphere–land surface model ECHAM5-JSBACH. The ECHAM5-JSBACH-wiso model was run under present-day climate conditions at two different resolutions (T31L19, T63L31). A comparison between ECHAM5-JSBACH-wiso and ECHAM5-wiso shows that the coupling has a strong impact on the simulated temperature and soil wetness. Caused by these changes of temperature and the hydrological cycle, the δ18O in precipitation also shows variations from −4‰ up to 4‰. One of the strongest anomalies is shown over northeast Asia where, due to an increase of temperature, the δ18O in precipitation increases as well. In order to analyze the sensitivity of the fractionation processes over land, we compare a set of simulations with various implementations of these processes over the land surface. The simulations allow us to distinguish between no fractionation, fractionation included in the evaporation flux (from bare soil) and also fractionation included in both evaporation and transpiration (from water transport through plants) fluxes. While the isotopic composition of the soil water may change for δ18O by up to +8‰:, the simulated δ18O in precipitation shows only slight differences on the order of ±1‰. The simulated isotopic composition of precipitation fits well with the available observations from the GNIP (Global Network of Isotopes in Precipitation) database.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER (OA)
  • 4
    facet.materialart.
    Unknown
    Glacial-interglacial changes 
of water isotopes (H218O, HDO) 
 as simulated by a 
fully coupled Earth System Model (2014)
    In:  EPIC3AGU Fall Meeting, San Francisco, 2014-12-15-2014-12-19
    Details
    Publication Date: 2015-02-03
    Description: During the past two decades, several atmospheric and oceanic general circulation models (GCMs) have been enhanced by the capability to explicitly simulate the hydrological cycle of the two stable water isotopes H218O and HDO. They have provided a wealth of understanding regarding changes of the water isotope signals in various archives under different past climate conditions. However, so far the number of fully coupled atmosphere-ocean GCMs with explicit water isotope diagnostics is very limited. Such coupled models are required for a more comprehensive simulation of both past climates as well as related isotope changes in the Earth’s hydrological cycle. Here, we report first results of a newly developed isotope diagnostics within the Earth system model ECHAM5-JSBACH/MPIMOM. Both H218O and HDO and their relevant fractionation processes are included in all compartments and branches of the water cycle within this model. First equilibrium simulations have been performed for both pre-industrial (PI) and Last Glacial Maximum (LGM) boundary conditions. Evaluation of the PI simulation reveals a good overall model performance in accordance with available modern isotope data from vapor measurements, precipitation samples as well as marine records. For precipitation, root-mean-square error (RMSE) between model results and GNIP δ18O data is approx. 3‰. For ocean surface water, model results and GISS δ18O observational data deviate by 1‰ RMSE or less, with strongest differences in the Arctic Ocean. The LGM experiment results in spatially varying isotope depletion in precipitation between -20‰ and 0‰ in agreement with data from various isotope records. The isotope data clearly mirrors a temperature change of similar range. For the ocean surface waters, the simulated isotopic composition shows a strong glacial enrichment in the North Atlantic of more than +0.5‰. In combination with glacial SST changes a LGM calcite δ18O enrichment of +2.5‰ is simulated. Analyses of the simulated Deuterium excess changes with Antarctic ice core data reveal a good model-data agreement and support the hypothesis of rather cool tropical SST during the last glacial maximum.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER (OA)
  • 5
    facet.materialart.
    Unknown
    Modelling water isotopes for an improved interpretation of climate proxy records (2012)
    In:  EPIC33rd International Conference on Earth System Modelling (3ICESM), Hamburg, Germany, 2012-09-17-2012-09-21
    Details
    Publication Date: 2019-07-17
    Description: During the past two decades, several atmospheric and oceanic general circulation models (GCMs) have been enhanced by the capability to explicitly simulate the hydrological cycle of the two stable water isotopes H218O and HDO. A number of previous studies have demonstrated the possibility of an improved interpretation of observed isotope variability in terms of climate change by such isotope GCM simulations. Here, we report new results of the ECHAM5 atmosphere GCM enhanced by explicit water isotope diagnosis (named ECHAM5-wiso hereafter). Several simulations covering climate changes in the range of the last decades up to glacial-interglacial cycles have been performed to evaluate the overall capability of the ECHAM5-wiso model and to enable a more quantitative interpretation of various isotope paleoarchives. All simulations have been performed with a high spatial model resolution of approx. 1° (T106 spectral mode) or finer. It is shown that the refinement of the spatial resolution leads to a substantially better agreement with available present-day observations and isotopic paleorecords, e.g. Antarctic ice core data. Using this new set of paleoclimate simulations, we investigate if and how climate variability is imprinted in the isotopic composition of precipitation on different time scales. Special focus is given to the question how the temperature-isotope relation might has changed in different regions of the Earth on the various time scale. The atmospheric isotope GCM results are complemented by first oceanic isotope GCM simulation results with the MPI-OM model as well as investigations of the influence of paleovegetation changes on the hydrological cycle and its isotopic composition, as simulated by an isotope-enhanced ECHAM5/JSBACH model setup.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER (OA)
  • 6
    facet.materialart.
    Unknown
    A new hydrogen-isotope approach to understand North African monsoon changes in the Holocene (2014)
    In:  EPIC3122 p.
    Details
    Publication Date: 2019-07-17
    Description: The aim of this thesis is to improve the understanding of the hydrological evolution of the North-West African monsoon system during the Holocene period. In particular the focus is placed on the drastic regime shift from humid and vegetated conditions of the mid-Holocene to the arid present-day conditions in North-West Africa. The timing of this regime shift is investigated in order to determine if the transition from the African Humid Period (approx. from 16,000 – 6,000 years ago) to dry present-day conditions occurred gradually or rapidly. In order to achieve this objective, variations in the isotopic composition of precipitation in relation to rainfall amount are scrutinized. To reach this goal the coupled atmosphere-land surface model ECHAM5-JSBACH is enhanced by the inclusion of a stable water isotope diagnostic module which traces beside the “normal water” H16O the heavier water isotopes H18O and HDO. The ECHAM5-JSBACH-wiso model is able to simulate the isotopic composition of precipitation (δ18OP and δDP) comparably well as the stand-alone ECHAM5-wiso model. In order to analyze the sensitivity of fractionation processes over land, a set of simulations with various implementations of these processes over the land surface are compared. The simulations distinguish between no fractionation, fractionation included in the evaporation flux (from bare soil), and fractionation included in both evaporation and transpiration (from water transport through plants) fluxes. While the isotopic composition of the soil water may change for δ18O by up to +8‰, the simulated δ18O in precipitation shows only slight differences in the order of ±1‰. For evaluation of the simulated isotope composition over the 20th century in North Africa, a nudged ECHAM5-JSBACH-wiso experiment is performed over the period 1958 to 2002. It is shown that the model simulates the climatology as well as interannual variability of precipitation and its isotopic composition in good agreement with observations. Furthermore, it is illustrated that the amount of Sahelian precipitation and δDP are correlated, with a Pearson correlation coefficient r = 0.71. Based on these model results the observed isotope variations are quantitatively calibrated with respect to changes of the precipitation amount. According to the model results, changes of -5‰ in δDP can be related to an increase of approximately 100 mm in rainfall amount under present-day conditions. In order to further investigate the evolution of the North-West African hydrological cycle during the Holocene, the precipitation and the vegetation cover simulated by the fully coupled Earth System model COSMOS are analyzed. Both variables indicate a gradual transition from the African Humid Period into the dry present-day conditions. Based on this transient experiment, time-slice simulations, performed with the ECHAM5-JSBACH-wiso model, are carried out. These time-slice simulations reveal an amplification as well as a southwards shift of the North African rain belt from mid-Holocene to present day. Due to the negative relation between the amount of precipitation and its isotopic composition, the simulated δD in precipitation is about -18‰ more depleted in the mid-Holocene experiment, compared to the present-day one, in the West Sahel region. The findings of the model studies are supported by novel proxy data derived from δD measurements on leaf waxes in the marine sediment core GeoB7920 from the North-West African coast. In summary, all results of these studies indicate that the drastic regime shift of vegetation and rainfall amount in North-West Africa during mid-Holocene was gradual.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Thesis , notRev
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER (OA)
  • 7
    facet.materialart.
    Unknown
    Stable water isotopes in the coupled atmosphere-land surface model ECHAM5-JSBACH, supplementary data (2013)
    PANGAEA
    In:  EPIC3Bremerhaven, PANGAEA
    Details
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: PANGAEA Documentation , notRev
    Format: application/x-netcdf
    Format: application/x-netcdf
    Format: application/x-netcdf
    Format: application/x-netcdf
    Format: application/x-netcdf
    Format: application/x-netcdf
    Format: application/x-netcdf
    Format: application/x-netcdf
    Format: application/x-netcdf
    Format: application/x-netcdf
    Format: application/x-netcdf
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER (OA)
  • 8
    facet.materialart.
    Unknown
    Glacial–interglacial changes in H218O, HDO and deuterium excess – results from the fully coupled ECHAM5/MPI-OM Earth system model (2016)
    In:  EPIC3Geoscientific Model Development, 9(2), pp. 647-670, ISSN: 1991-9603
    Details
    Publication Date: 2016-09-16
    Description: In this study we present the first results of a new isotope-enabled general circulation model set-up. The model consists of the fully coupled ECHAM5/MPI-OM atmosphere–ocean model, enhanced by the JSBACH interactive land surface scheme and an explicit hydrological discharge scheme to close the global water budget. Stable water isotopes H218O and HDO have been incorporated into all relevant model components. Results of two equilibrium simulations under pre-industrial and Last Glacial Maximum conditions are analysed and compared to observational data and paleoclimate records for evaluating the model’s performance in simulating spatial and temporal variations in the isotopic composition of the Earth’s water cycle. For the pre-industrial climate, many aspects of the simulation results of meteoric waters are in good to very good agreement with both observations and earlier atmosphere-only simulations. The model is capable of adequately simulating the large spread in the isotopic composition of precipitation between low and high latitudes. A comparison to available ocean data also shows a good model–data agreement; however, a strong bias of overly depleted ocean surface waters is detected for the Arctic region. Simulation results under Last Glacial Maximum boundary conditions also fit to the wealth of available isotope records from polar ice cores, speleothems, as well as marine calcite data. Data–model evaluation of the isotopic composition in precipitation reveals a good match of the model results and indicates that the temporal glacial–interglacial isotope– temperature relation was substantially lower than the present spatial gradient for most mid- to high-latitudinal regions. As compared to older atmosphere-only simulations, a remarkable improvement is achieved for the modelling of the deuterium excess signal in Antarctic ice cores. Our simulation results indicate that cool sub-tropical and mid-latitudinal sea surface temperatures are key for this progress. A recently discussed revised interpretation of the deuterium excess record of Antarctic ice cores in terms of marine relative humidity changes on glacial–interglacial timescales is not supported by our model results.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER (OA)
  • 9
    facet.materialart.
    Unknown
    Enriching the isotopic toolbox for migratory connectivity analysis: a new approach for migratory species breeding in remote or unexplored areas (2015)
    Wiley
    In:  EPIC3Diversity and Distributions, Wiley, 21(4), pp. 416-427, ISSN: 1366-9516
    Details
    Publication Date: 2015-12-09
    Description: Aim: We examined three potential enhancements of the stable isotope tech- nique for elucidating migratory connectivity in birds inhabiting poorly studied areas, illustrated for Eurasian cranes (Grus grus) that overwinter in and migrate through Israel. First, we examined the use of oxygen stable isotopes (d18O), sel- dom applied for this purpose. Second, we examined the relationship between ambient water d18O and hydrogen stable isotope (d2H) values derived from various models, to determine the geographical origins of migrants. Third, we introduced the use of probabilistic distribution modelling to refine the assign- ment to origin of migrants lacking detailed distribution maps. Location: Feather samples were collected in the Hula Valley (northern Israel) and across the species breeding range in north Eurasia. Methods: We analysed d18O and d2H in primary and secondary flight feathers using standard mass spectrometry. The maximum entropy (MAXENT) model was used to map the probability surface of potential breeding areas, as a Bayesian prior for assigning Hula Valley cranes to potential breeding grounds. Results: We found that d18O was suitable and informative. The soil water iso- scape performed better for d18O while precipitation isoscape was preferable for d2H. The MAXENT-based probability surface largely refined assignments. Overall, most (〉85%) cranes were assigned to the area west of the Ural Mountains, but for two individuals, most of the assigned area (〉90%) was farther east, suggest- ing, for the first time, that Eurasian cranes may undertake the North Asia–Mid- dle East (and perhaps Africa) migration flyway. Main conclusions: Our results call for broader use of d18O in migratory con- nectivity studies and for application of probabilistic distribution modelling. We also encourage investigation of factors determining d18O and d2H integration into animal tissues. The proposed framework may help improve our under- standing of migratory connectivity of species inhabiting previously unexplored areas and thus contribute to the development of efficient conservation plans.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER (OA)
  • 10
    facet.materialart.
    Unknown
    North-West African Hydrologic Changes in the Holocene: A Combined Isotopic Data and Model Approach (2015)
    Springer
    In:  EPIC3Integrated Analysis of Interglacial Climate Dynamics (INTERDYNAMIC), (SpringerBriefs in Earth System Sciences), Heidelberg, Springer, 139 p., pp. 109-114, ISBN: 978-3-319-00692-5, ISSN: 2191-589X
    Details
    Publication Date: 2015-02-04
    Description: To achieve a better understanding of the hydrologic evolution of the North-West (NW) African monsoon system during the Holocene, in particular during inferred abrupt climate changes at the end of the African Humid Period (AHP), we investigated terrigenous plant lipids deposited in marine sediments offshore NW Africa. Changes in rainfall amount were estimated by compound-specific hydrogen isotope (δD) analyses. The spatial gradient of rainfall isotopic compositions is reflected in marine surface sediments. δD changes in plant waxes covering the last 100 years confirm the observed decrease in rainfall during the late twentieth century Sahel drought, and thus can be used for a quantitative calibration of δD and pre- cipitation. δD changes in sedimentary plant waxes show no abrupt change at the end of the AHP suggesting a gradual precipitation decline. These results are supported by Holocene climate simulations using a coupled atmosphere-land surface model, which includes an explicit modeling of isotopic fractionation within the hydrological cycle.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Inbook , peerRev
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER (OA)
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...