Kirsten Elger

ASCAT Surface State Flag (SSF): Extracting Information on Surface Freeze/Thaw Conditions From Backscatter Data Using an Empirical Threshold-Analysis Algorithm

Information on soil surface state is valuable for many applications such as climate studies and monitoring of permafrost regions. C-band scatterometer data indicate good potential to deliver information on surface freeze/thaw. Variation in state or amount of water contained in the soil causes significant alteration of dielectric properties of the soil which is markedly observable in scatterometer backscattered signal. A threshold-analysis method is developed to derive a set of parameters to be used in evaluating the normalized backscatter measurements through decision trees and anomaly detection modules for determination of freeze/thaw conditions. The model parameters are extracted from two years (2007-2008) backscatter data from ASCAT scatterometer onboard Metop satellite collocated with ECMWF ReAnalysis (ERA-Interim) soil temperature. Backscatter measurements are flagged as indicator of frozen/unfrozen surface, and snowmelt or existing water on the surface. The output product, so-called surface state flag (SSF), compares well with two modeled soil temperature data sets as well as the air temperature measurements from synoptic meteorological stations across the northern hemisphere. The SSF time series are also validated with soil temperature data available at four in situ observation sites in Siberian and Alaska regions showing the overall accuracy of about 80% to 90%.

Open research data, data portals and data publication – an introduction to the data curation landscape

During the past decade, the relevance of research data stewardship has been rising significantly and data publication has become more familiar. Preservation of research data for long-term use, including its storage in adequate repositories has been identified as a key issue by the scientific community as well as by research agencies and the public. In practice, however, the current state of data sharing and re-use requires considerable improvement. This paper reviews recent developments in this area, and aims to provide some guidance to the increasing diversity of newly developed digital solutions, such as data journals, online data repositories, and citable digital object identifier (DOI) for datasets. We examine the differences and similarities between different examples of Arctic-related data management, including the newly created database of the Global Terrestrial Network for Permafrost GTN-P, a Canadian example of a (meta)data portal (Polar Data Catalogue), and examples of data repositories (e.g., PANGAEA, Nordicana D) and data journals (e.g., Earth System Science Data). We also describe the newly established Registry of Research Data Depositories (re3data.org) as a convenient resource for individual researchers to get an overview on and identify an appropriate repository for their scientific datasets as well for funding agencies during the evaluation process of the data management plan of research proposals. Zusammenfassung: In den letzten zehn Jahren ist die Bedeutung des Zugangs und der Nachnutzung von Forschungsdaten gestiegen. Neue Publikationsstrategien für Forschungsdaten stellen sicher, dass wissenschaftliche Daten dauerhaft in geeigneten Daten-Repositorien gespeichert und zugänglich gemacht werden können. Auch wenn die Umsetzung dieser Publikationsstrategien von der wissenschaftlichen Community und von Forschungsförderorganisationen als zentrale Herausforderung für das Wissenschaftssystem benannt wird, ergeben sich in der Praxis noch viele Herausforderungen. Dieser Artikel gibt einen Überblick über aktuelle Entwicklungen im Bereich des Forschungsdatenmanagements. Exemplarisch werden einige Beispiele für den offenen Zugang vorgestellt und Publikationsstrategien für Forschungsdaten beschrieben. U.a. werden Aufgabe und Dienstleistung von Daten-Repositorien, Daten-Journalen sowie Daten-Portalen im Bereich der Arktisforschung erläutert. Exemplarisch werden folgende digitale Forschungsdateninfrastrukturen vorgestellt: Das kanadische (Meta)daten-Portal Polar Data Catalogue, die neue Datenbank des Global Terrestrial Network for Permafrost GTN-P (Metadaten und Daten), die Daten-Repositorien PANGAEA und Nordicana D sowie das Daten-Journal Earth System Science Data (ESDD). Darüber hinaus wird der Service des Registry of Research Data Repositories (re3data. org) vorgestellt. Dieses internationale Verzeichnis unterstützt Forschende und Forschungsförderer bei der Identifikation von geeigneten Daten-Repositorien zur Speicherung und Zugänglichmachung ihrer Forschungsdaten.

Schematic overview of a typical terrestrial and shallow-marine permafrost landscape during summer and winter

Schematic overview of a typical terrestrial and shallow-marine permafrost landscape during summer and winter. Permafrost is defined as ground that remains continuously at or below 0°C for at least two consecutive years; some 24% of the land surface in the northern hemisphere is classified as permafrost. This schematic figure (summer) pictures a terrestrial and shallow marine permafrost system. A permafrost landscape is characterized by its large heterogeneity with morphological permafrost-related features such as polygonal patterned ground with underlying ice wedges, thaw ponds, thermokarst lakes, and wetland areas. During winter, the terrestrial landscape is covered with snow, and water bodies and the ocean are typically covered with ice.The last pictures shows schematically the fluxes (not scaled) that occur between the terrestrial and marine environment and atmosphere.