Filtern
Erscheinungsjahr
Dokumenttyp
- Wissenschaftlicher Artikel (50)
- Dissertation (45)
- Konferenzveröffentlichung (3)
- Arbeitspapier (1)
Sprache
- Englisch (99) (entfernen)
Schlagworte
- Fernerkundung (18)
- Modellierung (14)
- Satellitenfernerkundung (8)
- Meereis (7)
- Arctic (5)
- Arktis (5)
- Atmosphärische Grenzschicht (5)
- Remote Sensing (5)
- Rheinland-Pfalz (5)
- Deutschland (4)
- Luxemburg (4)
- MODIS (4)
- Nachhaltigkeit (4)
- remote sensing (4)
- Anpassung (3)
- Biomonitoring (3)
- Boden (3)
- Bodenerosion (3)
- Degradation (3)
- Höhlensalamander (3)
- Katabatischer Wind (3)
- Klima (3)
- Klimaänderung (3)
- Landsat (3)
- Landwirtschaft (3)
- Laptewsee (3)
- Polynja (3)
- Remote sensing (3)
- Rutschung (3)
- Salamander (3)
- Waldinventur (3)
- regional climate model (3)
- sea ice (3)
- Adaptation (2)
- Angola (2)
- Antarctic (2)
- Bildverarbeitung (2)
- Biodiversität (2)
- Biogeographie (2)
- Bodenmikrobiologie (2)
- Bodenverschmutzung (2)
- CCLM (2)
- COSMO-CLM (2)
- Chemische Analyse (2)
- Datenassimilation (2)
- Drift (2)
- Forst (2)
- Froschlurche (2)
- Genetische Variabilität (2)
- Geoinformation Processing (2)
- Germany (2)
- Greenland (2)
- Grönland (2)
- Hochwasser (2)
- Hydrologie (2)
- Infrarotthermographie (2)
- Land Degradation (2)
- Landdegradation (2)
- Landnutzung (2)
- Laptev Sea (2)
- Larve (2)
- Luftbild (2)
- MODIS ice surface temperatures (2)
- Mageninhalt (2)
- Maschinelles Lernen (2)
- Mittelmeerraum (2)
- Modell (2)
- Monitoring (2)
- Nahrung (2)
- Niederschlag (2)
- Ozon (2)
- Phänologie (2)
- Polargebiete (2)
- Polynya (2)
- Strahlstrom (2)
- Thailand (2)
- Trockenwald (2)
- Umweltüberwachung (2)
- Vegetation (2)
- Wald (2)
- Weinbau (2)
- Zeitreihe (2)
- atmospheric boundary layer (2)
- climate change (2)
- data assimilation (2)
- drought (2)
- hyperspectral (2)
- image segmentation (2)
- katabatic winds (2)
- leads (2)
- low-level jets (2)
- ozone (2)
- para-Phenylendiamin (PPD) (2)
- stable boundary layer (2)
- time series analysis (2)
- verification (2)
- Ökologie (2)
- 15N (1)
- AFLP (1)
- ALS (1)
- APSIM model (1)
- APSIM-Modell (1)
- Abfall (1)
- Ablagerung (1)
- Abundanz (1)
- Abwasser (1)
- Abwasserreinigung (1)
- Acidobacteria (1)
- Actinobacteria (1)
- Advection-dispersion equation (1)
- Advektion-Diffusionsgleichung (1)
- Ah-Rezeptor (1)
- AhR (1)
- Airline (1)
- Alar (1)
- Allozym-Elektrophorese (1)
- Amazonas-Gebiet (1)
- Anatolien / Süd (1)
- Andosol (1)
- Animal behaviour (1)
- Antarktis (1)
- Anthropogene Klimaänderung (1)
- Antibiotikum (1)
- Anura (1)
- Anurans (1)
- Aposeris foetida (1)
- Aquatisches Ökosystem (1)
- Arealgrenzen (1)
- Artificial Neural Network (1)
- Arzneimittel (1)
- Ascaridol (1)
- Atmosphärische Turbulenz (1)
- Ausgangsgestein (1)
- Ausrottung (1)
- Australien <Nordost> (1)
- Autokorrelation (1)
- BCI (1)
- BRDF (1)
- Bacteria phyla (1)
- Baum (1)
- Baumwollpflanze (1)
- Behandlungstechnologien (1)
- Belebtschlamm (1)
- Benzo[a]pyrene (1)
- Beregnung (1)
- Bewegungsmessung (1)
- Beweidung (1)
- Bias-Korrektur (1)
- Big Data (1)
- Bioakkumulation (1)
- Biogasgewinnung (1)
- Biogeochemie (1)
- Biogeography (1)
- Bioindication (1)
- Bioindikation (1)
- Biological control (1)
- Biological wastewater treatment (1)
- Biologischer Pflanzenschutz (1)
- Biomasse (1)
- Blattflächenindex (1)
- Blutegel (1)
- Bodenaggregate (1)
- Bodenbakterien (1)
- Bodenbearbeitung (1)
- Bodennahe Luftschicht (1)
- Bodenpilze (1)
- Bodentiere (1)
- Bodenwiderstand (1)
- Brackwasser (1)
- Bruch (1)
- Brutpflege (1)
- Burg Turaida (1)
- CAPE (1)
- CC-Chemokinrezeptor 2 (CCR2) (1)
- CCR2 (1)
- Carcinogenese (1)
- Carrier-Proteine (1)
- Cave (1)
- Chain Hotel (1)
- Characteristic (1)
- Chemische Kommunikation (1)
- China (Nordwest) (1)
- Chlorophyll (1)
- Climate Change (1)
- Crop classification (1)
- Cuvelai Etoscha Becken (1)
- Cuvelai Etosha-basin (1)
- Cäsium-134 (1)
- Cäsium-137 (1)
- DDT (1)
- DNS-Sequenz (1)
- Dachschiefer (1)
- Datensammlung (1)
- Deep learning (1)
- Deflation (1)
- Demökologie (1)
- Deposit (1)
- Desertification (1)
- Desertifikation (1)
- Diet (1)
- Digitalisierung (1)
- Diskursanalyse (1)
- Dispersal (1)
- Disturbance Index (1)
- Dose-response relationship (1)
- Dosis-Wirkungs-Beziehung (1)
- Drought (1)
- Dynamische Modellierung (1)
- E-marketing (1)
- Early Warning (1)
- Ecology (1)
- Ecosystem Services (1)
- Ecosystem services (1)
- Ecotoxicology (1)
- Eigenschaft (1)
- Eigenschaften der vorbehandelte Abfälle (1)
- Einstrahlung (1)
- Einzugsgebiet (1)
- Einzugsgebietsmanagement (1)
- Eisbildung (1)
- Eisenhydroxide (1)
- Eisenoxide (1)
- Eiszeit (1)
- Ellesmere Island (1)
- Endemic Centre (1)
- Endemitenzentren (1)
- Energie (1)
- Energiepflanzen (1)
- Entsalzung (1)
- Entwaldung (1)
- Environment (1)
- Environmental Monitoring (1)
- Enzymatic reactions (1)
- Enzyme inhibition (1)
- Enzyme kinetics (1)
- Enzymimmunassay (1)
- Enzymkinetik (1)
- Eradication (1)
- Erbkrankheit (1)
- Erde (1)
- Ernährungssicherung (1)
- Erzbergbau (1)
- Eugenol (1)
- Europa (1)
- Europe (1)
- Evapotranspiration (1)
- Evolution (1)
- Experiment (1)
- Extremwert (1)
- Extremwertanalyse (1)
- Faunal migration (1)
- Faunenmigration (1)
- Feldforschung (1)
- Feldfrucht (1)
- Fertilitätsstörung (1)
- Fettsucht (1)
- Feuchtwiese (1)
- Feuer (1)
- Feuersalamander (1)
- Fichte (1)
- Fish (1)
- Flechten (1)
- Flugkörper (1)
- Forestry (1)
- Forstlicher Standort (1)
- Forstwirtschaft (1)
- Fremdstoffmetabolismus (1)
- Fruchtbildung (1)
- Functional soil biodiversity (1)
- Fungizid (1)
- Funktionelle Biodiversität (1)
- GEOBIA (1)
- GPS (1)
- Gas Chromatography (1)
- Gasaustausch (1)
- Gauja spillway valley (1)
- Gebirgswald (1)
- Genetik (1)
- Geodatenverarbeitung (1)
- Geoinformationssystem (1)
- Geowissenschaften (1)
- Getreide (1)
- Gewitter (1)
- Glaziale Refugien (1)
- Grenzgebiet (1)
- Griechenland (1)
- Habitatfragmentierung (1)
- Hapten (1)
- Haut (1)
- Hautzelle (1)
- Herpetology (1)
- Heuschrecken (1)
- Hochmoorgelbling (1)
- Humus (1)
- Hybridisierung (1)
- Hydrodynamik (1)
- Hydrology (1)
- Hyperspectral (1)
- Hyperspektraldaten (1)
- Hyperspektraler Sensor (1)
- Häufigkeit (1)
- Höhle (1)
- Ice production (1)
- Image Processing (1)
- Immundefekt (1)
- Immunglobulintherapie (1)
- Immunisation (1)
- Immunisierung (1)
- In-vitro-Kultur (1)
- Indonesia (1)
- Indonesien (1)
- Infrarot (1)
- Inhalation (1)
- Inhalation Toxicology (1)
- Insektizid (1)
- Insel-Verdriftungen (1)
- Interaction (1)
- Inversion (1)
- Iran (1)
- Island-drifts (1)
- Isoeugenol (1)
- Kalkulationsverfahren (1)
- Karst (1)
- Karte (1)
- Kartierung (1)
- Kaulquappe (1)
- Keratiniozyten (1)
- Keratinocytes (1)
- Kieselerden (1)
- Klassifikation (1)
- Klimamodell (1)
- Klimawandel (1)
- Konservierende Bodenbearbeitung (1)
- Kontaktdermatitis (1)
- Kontamination (1)
- Kosten-Nutzen-Analyse (1)
- Kriging (1)
- Künstliches Fließgewässer (1)
- LAI (1)
- Lagerung (1)
- Landsat-8 OLI (1)
- Laptev See (1)
- Larva (1)
- Laubwald (1)
- Leaf Area Index (1)
- Lebenszyklusanalyse (1)
- Leech (1)
- Leistungsmessung (1)
- LiDAR (1)
- Lichens (1)
- Lidar (1)
- Life Cycle Assessment (1)
- Limnology (1)
- Luftverschmutzung (1)
- Lunge (1)
- Lurche (1)
- MBA-Technologie (1)
- MBT technology (1)
- MCP-1 (1)
- MOSAiC (1)
- Madagascar (1)
- Maisanbau (1)
- Maissilage (1)
- Managementstrategien (1)
- Mangrove (1)
- Marketing (1)
- Massendaten (1)
- Mathematisches Modell (1)
- Mechanical and biological treatment (1)
- Mechanisch-biologische Abfallbehandlung (1)
- Mechanisch-biologische Verfahren (1)
- Mechanische Eigenschaft (1)
- Mediterrane Rangelands (1)
- Mediterranean (1)
- Mediterranean Rangelands (1)
- Meeresströmung (1)
- Meteorologie (1)
- Mikrofaser (1)
- Mikrosatelliten (1)
- MinION (1)
- Mineral (1)
- Mineralogie (1)
- Mittelgebirge (1)
- Mittelmoseltal (1)
- MoDC (1)
- MoDZ (1)
- Modelling (1)
- Mohrenfalter (1)
- Monozyten-chemotaktische Protein 1 (MCP-1) (1)
- Monte-Carlo simulation (1)
- Monte-Carlo-Simulation (1)
- Moor (1)
- Moose (1)
- Morphologie (1)
- Mosses (1)
- Multispektralfotografie (1)
- Mykotoxin (1)
- N-Acetyltransferase 1 (NAT1) (1)
- N-acetyltransferase 1 (NAT1) (1)
- NOAA AVHRR (1)
- Nadelwald (1)
- Nahrungsaufnahme (1)
- Nanopartikel (1)
- Nares-Straße (1)
- Nationalpark Hunsrück-Hochwald (1)
- Naturgefahr (1)
- Nervennetz (1)
- Nische (1)
- Nitrogen Deposition (1)
- Nordwestchina (1)
- North Water Polynya (1)
- Nutzpflanzen (1)
- Nutzwertanalyse (1)
- Oberflächenströmung (1)
- Oberflächentemperatur (1)
- OpenStreetMap (1)
- Organic phosphorus compounds (1)
- Orientierung (1)
- Orthoptera (1)
- Oxford Nanopore Technologies (1)
- Ozon-Phytotoxizität (1)
- Ozonbelastung (1)
- Ozone flux model (1)
- Ozonflussmodell (1)
- PBMC (1)
- PPD (1)
- Pakistan (1)
- Parapatrie (1)
- Parapatry (1)
- Parasitism (1)
- Parasitismus (1)
- Partnerwahl (1)
- Patagonien Süd (1)
- Pathogener Mikroorganismus (1)
- Penman-Monteith equation (1)
- Peru (1)
- Pesticides (1)
- Pestizid-Anwendungen (1)
- Pestizidbelastung (1)
- Pflanzenschutzmitteln (1)
- Pflanzenwachstum (1)
- Pharmazeutika (1)
- Phosphatelimination (1)
- Phosphor elimination (1)
- Phosphororganische Verbindungen (1)
- Phylogeographie (1)
- Physikalische Eigenschaft (1)
- Plant pathogen repression (1)
- Plasmaersatz (1)
- Polychlorierte Biphenyle (1)
- Population Ecology (1)
- Populationsgenetik (1)
- Predation (1)
- Primary photon fluence rates (1)
- Process benchmarking (1)
- Proliferation (1)
- Provinz Copperbelt (1)
- Provinz Golestan (1)
- Prozessbenchmarking (1)
- Pseudogley (1)
- Qualitätssicherung (1)
- Radar (1)
- Radiometrie (1)
- Randmeer (1)
- Reflectance Modeling (1)
- Reflexionsmodellierung (1)
- Reflexionsspektroskopie (1)
- Regenwurmgang (1)
- Regression Kriging (1)
- Reproduction (1)
- Ressourcen-Konkurrenz (1)
- Ressourcenpolitik (1)
- Rhizosphäre (1)
- Risikomanagement (1)
- Ruthenium-106 (1)
- SAR (1)
- SARS-CoV-2 (1)
- SARS‐CoV‐2 (1)
- SODAR (1)
- Saar-Lor-Lux (1)
- Salamanders (1)
- Salzgehalt (1)
- Sambia (1)
- Samen (1)
- Sardinien (1)
- Satellit (1)
- Schelfeis (1)
- Schmetterlinge (1)
- Schweizer Alpen (1)
- Schwermetall (1)
- Schädling (1)
- Sea ice (1)
- Sediment (1)
- Selbstorganisierende Karte (1)
- Self-Organizing Maps (1)
- Sensibilisierung <Immunologie> (1)
- Sequenzanalyse / Chemie (1)
- Sewernaja Semlja (1)
- Sexualdimorphismus (1)
- Sharing Economy (1)
- Shifting cultivation (1)
- Silber (1)
- Silver Nanoparticles (1)
- Sinonatrix (1)
- Sistānbecken (1)
- Sodar (1)
- Soil (1)
- Solar thermal desalination technique (1)
- Solarthermische Entsalzungstechnologie (1)
- Southern Africa (1)
- Spanien (1)
- Spatial autocorrelation (1)
- Spektrale Emissivität (1)
- Spektroradiometrie (1)
- Spektroskopie (1)
- Speleomantes (1)
- Spitzbergen (1)
- Spline (1)
- Stabile Isotope (1)
- Stable Isotopes (1)
- Stagnosols (1)
- Steilhang (1)
- Stickstoffdeposition (1)
- Stickstoffoxide (1)
- Stofftransport (1)
- Stomach (1)
- Stomatal conductance (1)
- Stomatäre Leitfähigkeit (1)
- Strategie (1)
- Strategy (1)
- Stress (1)
- Strontium-85 (1)
- Strontium-90 (1)
- Sulfadiazin (1)
- Surface Lifted Index (1)
- Sustainability (1)
- Switzerland (1)
- THP-1 (1)
- Taiwan (1)
- Temperatur (1)
- Terpene (1)
- Terrestrisches Laserscanning (1)
- Terrestrisches ükosystem (1)
- Thermales Infrarot (1)
- Thermalluftbild (1)
- Thin Sea Ice (1)
- Time dependant Weibull-distribution (1)
- Time series analysis (1)
- Tourism (1)
- Tourismus (1)
- Touroperator (1)
- Toxikologie (1)
- Toxizität (1)
- Transfer function model (1)
- Trier (1)
- Trockengebiet (1)
- Trockenheit (1)
- Trockenstress Detektion (1)
- Trophic interactions (1)
- Tsunami (1)
- UAV (1)
- UNCCD (1)
- Umweltprobe (1)
- Utility analysis (1)
- Vaccination (1)
- Vegetation Index (1)
- Vegetationsindex (1)
- Verbreitung (1)
- Verteilungsgerechtigkeit (1)
- Visualisierung (1)
- Wachstum (1)
- Wachtelweizen (1)
- Waldtyp (1)
- Waschmittel (1)
- Wasser (1)
- Wasserbilanz (1)
- Wassernattern (1)
- Wasserstress (1)
- Watershed modelling (1)
- Wechselwarme (1)
- Weddellmeer (1)
- Weibull-Verteilung (1)
- Weißklee (1)
- White clover (1)
- Wind (1)
- Windfeld (1)
- Wolke (1)
- Wuchsmodellierung (1)
- Wurzelraum (1)
- Wärmeanomalie (1)
- Wärmestrahlung (1)
- Wüstenkonvention (1)
- Xenobiotics (1)
- Z (1)
- Zebrabärbling (1)
- Zeitreihenanalyse (1)
- Zellzyklus (1)
- Zellzyklus-Regulation (1)
- Zoologie (1)
- abiotic factors (1)
- abiotische Faktoren (1)
- abundance (1)
- acid mine drainage (1)
- actual evapotranspiration (1)
- aerial imagery (1)
- agricultural dust (1)
- allozyme electrophoresis (1)
- antibiotic (1)
- ascaridol (1)
- atmospheric modeling (1)
- atmospheric modelling (1)
- atmospheric pollution (1)
- atmospheric water balance (1)
- basal area increment (1)
- bias correction (1)
- biodiversity (1)
- biodiversity hotspots (1)
- biogas (1)
- biomethantion (1)
- burrows (1)
- canopy surface resistance (1)
- catchment management (1)
- cave (1)
- cell culture (1)
- cell cycle (1)
- characteristics of pre-treated waste (1)
- chemical communication (1)
- chemometrics (1)
- co-registration (1)
- common variable immunodeficiency (1)
- conservation value (1)
- convalescent plasma (1)
- crop stress (1)
- deep learning (1)
- degradation (1)
- dendritic cells (1)
- dendritische Zellen (1)
- detergents (1)
- diatomaceous earth (1)
- digitalization (1)
- discourse analysis (1)
- dispersal (1)
- dry tropical forest (1)
- drylands (1)
- dynamics of mammal population (1)
- ecological niche (1)
- ecology (1)
- ectotherms (1)
- emissivity (1)
- entomopathogene Pilze (1)
- entomopathogenic fungi (1)
- environmental impact (1)
- epidermal dendritic cells (1)
- epidermale dendritische Zellen (1)
- erosion measurement (1)
- eugenol (1)
- eukaryotes (1)
- evapotranspiration (ET) modeling (1)
- extreme value analysis (1)
- faunmap database (1)
- flood (1)
- floods (1)
- flushing (1)
- food security (1)
- forest (1)
- forest inventory (1)
- forestry (1)
- forests (1)
- foss (1)
- fructification (1)
- fungicides (1)
- gap flow (1)
- genetic diversity (1)
- genetische Struktur (1)
- genomic structure (1)
- geobia (1)
- geography of knowledge (1)
- geometric (1)
- glacial refugia (1)
- growth modelling (1)
- habitat fragmentation (1)
- hazard mitigation (1)
- heavy metal (1)
- high-resolution (1)
- hochauflösend (1)
- hybridization (1)
- hydraulic modelling (1)
- hydrodynamics (1)
- hyperspektral (1)
- ice shelves (1)
- ice thickness (1)
- imaging spectroscopy (1)
- immunoglobulin replacement (1)
- in vitro (1)
- individual tree detection (1)
- insect conservation (1)
- insecticides (1)
- inversion (1)
- isoeugenol (1)
- just transition (1)
- katabatic wind (1)
- land degradattion (1)
- land use (1)
- landslides (1)
- late quaternary (1)
- long DNA barcodes (1)
- lung (1)
- machine-learning (1)
- mangrove (1)
- mate choice (1)
- metabarcoding (1)
- metabolism (1)
- meteorology (1)
- microorganisms (1)
- microrefugia (1)
- mineralogy (1)
- miombo woodland (1)
- mircrosatellite (1)
- model evaluation (1)
- model performance (1)
- mountain topography (1)
- multispectral (1)
- mutation (1)
- mycotoxin degradation (1)
- nitrogen oxides (1)
- norm mineral calculation (1)
- northwestern China (1)
- numerical models (1)
- obesity (1)
- open data (1)
- para-phenylenediamine (PPD) (1)
- parental care (1)
- particulate matter (1)
- peak-over-threshold (1)
- peripheren mononukleären Blutzellen (PBMC) (1)
- pest species (1)
- pesticide application (1)
- pharmaceuticals (1)
- phenology (1)
- phototropism (1)
- phyllites (1)
- phylogeography (1)
- plant adaptation mechanisms (1)
- point set registration (1)
- polynomial spline (1)
- polynyas (1)
- population genetics (1)
- pretreated waste (1)
- primärer Photonenfluss (1)
- rain (1)
- regeneration (1)
- region growing (1)
- resource competition (1)
- resource governance (1)
- rhizosphere (1)
- ribosomal (1)
- risk assessment (1)
- roof slates (1)
- salamander (1)
- salamanders (1)
- salt (1)
- satellite TIR mission (1)
- sea-ice (1)
- segmentation (1)
- sentinel 1 (1)
- sentinel-2 (1)
- sexual size dimorphism (1)
- shales (1)
- sharing economies (1)
- skin (1)
- skin sensitization (1)
- slope stability modelling (1)
- social sustainability (1)
- socio-nature relations (1)
- soil contamination (1)
- soil microbial activity (1)
- soil microbial biomass (1)
- soil microhabitats (1)
- soil surface resistance (1)
- soil water content (1)
- spectral emissivity (1)
- stem detection (1)
- sub-Saharan Africa (1)
- sulfadiazine (1)
- sustainability (1)
- temperature (1)
- terrestrial laser scanning (1)
- thermal infrared (1)
- thermal infrared (TIR) (1)
- thermal infrared remote sensing (1)
- thermal remote sensing (1)
- thunderstorm (1)
- time series (1)
- topographic flow (1)
- toxicity (1)
- tree inclination (1)
- tree matching (1)
- turbulence parameterization (1)
- uncoupling protein (1)
- vegetation index (1)
- viticulture (1)
- vorbehandelter Abfälle (1)
- vorbeugender Hochwasserschutz (1)
- wastewater (1)
- water stress (1)
- water stress detection (1)
- water use (1)
- waterlogging (1)
- wetland conservation (1)
- wind erosion (1)
- xenobiotic metabolism (1)
- Ästuar (1)
- Ökoeffizienz (1)
- Ökologische Dienstleistungen (1)
- Ökosystemdienstleistung (1)
- Überflutung (1)
- ükosystem (1)
Institut
- Raum- und Umweltwissenschaften (99) (entfernen)
Intense, southward low-level winds are common in Nares Strait, between Ellesmere Island and northern Greenland. The steep topography along Nares Strait leads to channelling effects, resulting in an along-strait flow. This research study presents a 30-year climatology of the flow regime from simulations of the COSMO-CLM climate model. The simulations are available for the winter periods (November–April) 1987/88 to 2016/17, and thus, cover a period long enough to give robust long-term characteristics of Nares Strait. The horizontal resolution of 15 km is high enough to represent the complex terrain and the meteorological conditions realistically. The 30-year climatology shows that LLJs associated with gap flows are a climatological feature of Nares Strait. The maximum of the mean 10-m wind speed is around 12 m s-1 and is located at the southern exit of Smith Sound. The wind speed is strongly related to the pressure gradient. Single events reach wind speeds of 40 m s-1 in the daily mean. The LLJs are associated with gap flows within the narrowest parts of the strait under stably stratified conditions, with the main LLJ occurring at 100–250 m height. With increasing mountain Froude number, the LLJ wind speed and height increase. The frequency of strong wind events (>20 m s-1 in the daily mean) for the 10 m wind shows a strong interannual variability with an average of 15 events per winter. Channelled winds have a strong impact on the formation of the North Water polynya.
Mankind has dramatically influenced the nitrogen (N) fluxes between soil, vegetation, water and atmosphere " the global N cycle. Increasing intensification of agricultural land use, caused by the growing demand for agricultural products, has had major impacts on ecosystems worldwide. Particularly nitrogenous gases such as ammonia (NH3) have increased mainly due to industrial livestock farming. Countries with high N deposition rates require a variety of deposition measurements and effective N monitoring networks to assess N loads. Due to high costs, current "conventional"-deposition measurement stations are not widespread and therefore provide only a patchy picture of the real extent of the prevailing N deposition status over large areas. One tool that allows quantification of the exposure and the effects of atmospheric N impacts on an ecosystem is the use of bioindicators. Due to their specific physiology and ecology, especially lichens and mosses are suitable to reflect the atmospheric N input at ecosystem level. The present doctoral project began by investigating the general ability of epiphytic lichens to qualify and quantify N deposition by analysing both lichens and total N and δ15N along a gradient of different N emission sources and severity. The results showed that this was a viable monitoring method, and a grid-based monitoring system with nitrophytic lichens was set up in the western part of Germany. Finally, a critical appraisal of three different monitoring techniques (lichens, mosses and tree bark) was carried out to compare them with national relevant N deposition assessment programmes. In total 1057 lichen samples, 348 tree bark samples, 153 moss samples and 24 deposition water samples, were analysed in this dissertation at different investigation scales in Germany.The study identified species-specific ability and tolerance of various epiphytic lichens to accumulate N. Samples of tree bark were also collected and N accumulation ability was detected in connection with the increased intensity of agriculture, and according to the presence of reduced N compounds (NHx) in the atmosphere. Nitrophytic lichens (Xanthoria parietina, Physcia spp.) have the strongest correlations with high agriculture-related N deposition. In addition, the main N sources were revealed with the help of δ15N values along a gradient of altitude and areas affected by different types of land use (NH3 density classes, livestock units and various deposition types). Furthermore, in the first nationwide survey of Germany to compare lichens, mosses and tree bark samples as biomonitors for N deposition, it was revealed that lichens are clearly the most meaningful monitor organisms in highly N affected regions. Additionally, the study shows that dealing with different biomonitors is a difficult task due to their variety of N responses. The specific receptor surfaces of the indicators and therefore their different strategies of N uptake are responsible for the tissue N concentration of each organism group. It was also shown that the δ15N values depend on their N origin and the specific N transformations in each organism system, so that a direct comparison between atmosphere and ecosystems is not possible.In conclusion, biomonitors, and especially epiphytic lichens may serve as possible alternatives to get a spatially representative picture of the N deposition conditions. Furthermore, bioindication with lichens is a cost-efficient alternative to physico-chemical measurements to comprehensively assess different prevailing N doses and sources of N pools on a regional scale. They can at least support on-site deposition instruments by qualification and quantification of N deposition.
The main goal of this publication is the development and application of an empirical method, which allows to forecast the transport of radionuclides in soils ad sediments. The calculations are based on data published in the literature. 10 case studies, comprising 30 time series, deal with the transport of Cs-134, Cs-137, Sr-85, Sr-90, and Ru-106. Transport in undisturbed soils and experimental systems like lysimeters and columns in laboratories are dealt with. The soils involved cover a large range of soils, e. g. podsols, cambisols (FAO), and peaty soils. Different speciations are covered, namely ions, aerosols, and fuel particles. Time series analysis centres around the Weibull-distribution. All theoretical models failed to forecast the transport of radionuclides. It can be shown that the parameters D and v, the dispersion coefficient and the advection velocity, appearing in solutions of the advection-dispersion equation (ADE), have no real physical meaning. They are just fitting parameters. The calculation of primary photon fluence rates, caused by Cs-137 in the soil, stresses the unreliability of forecasts based on theoretical models.
Time series archives of remotely sensed data offer many possibilities to observe and analyse dynamic environmental processes at the Earth- surface. Based on these hypertemporal archives, which offer continuous observations of vegetation indices, typically at repetition rates from one to two weeks, sets of phenological parameters or metrics can be derived. Examples of such parameters are the beginning and end of the annual growing period, as well as its length. Even though these parameters do not correspond exactly to conventional observations of phenological events, they nevertheless provide indications of the dynamic processes occurring in the biosphere. The development of robust algorithms for the derivation of phenological metrics can be challenging. Currently, such algorithms are most commonly based on digital filters or the Fourier analysis of time series. Polynomial spline models offer a useful alternative to existing methods. The possibilities of using spline models in the analytical description of time series are numerous, and their specific mathematical properties may help to avoid known problems occurring with the more common methods for deriving phenological metrics. Based on a selection of different polynomial spline models suitable for the analysis of remotely sensed time series of vegetation indices, a method to derive various phenological parameters from such time series was developed and implemented in this work. Using an example data set from an intensively used agricultural area showing highly dynamic variations in vegetation phenology, the newly developed method was verified by a comparison of the results of the spline based approach to the results of two alternative, well established methods.
Determining the exact position of a forest inventory plot—and hence the position of the sampled trees—is often hampered by a poor Global Navigation Satellite System (GNSS) signal quality beneath the forest canopy. Inaccurate geo-references hamper the performance of models that aim to retrieve useful information from spatially high remote sensing data (e.g., species classification or timber volume estimation). This restriction is even more severe on the level of individual trees. The objective of this study was to develop a post-processing strategy to improve the positional accuracy of GNSS-measured sample-plot centers and to develop a method to automatically match trees within a terrestrial sample plot to aerial detected trees. We propose a new method which uses a random forest classifier to estimate the matching probability of each terrestrial-reference and aerial detected tree pair, which gives the opportunity to assess the reliability of the results. We investigated 133 sample plots of the Third German National Forest Inventory (BWI, 2011"2012) within the German federal state of Rhineland-Palatinate. For training and objective validation, synthetic forest stands have been modeled using the Waldplaner 2.0 software. Our method has achieved an overall accuracy of 82.7% for co-registration and 89.1% for tree matching. With our method, 60% of the investigated plots could be successfully relocated. The probabilities provided by the algorithm are an objective indicator of the reliability of a specific result which could be incorporated into quantitative models to increase the performance of forest attribute estimations.
Low-level jets (LLJs) are climatological features in polar regions. It is well known that katabatic winds over the slopes of the Antarctic ice sheet are associated with strong LLJs. Barrier winds occurring, e.g., along the Antarctic Peninsula may also show LLJ structures. A few observational studies show that LLJs occur over sea ice regions. We present a model-based climatology of the wind field, of low-level inversions and of LLJs in the Weddell Sea region of the Antarctic for the period 2002–2016. The sensitivity of the LLJ detection on the selection of the wind speed maximum is investigated. The common criterion of an anomaly of at least 2 m/s is extended to a relative criterion of wind speed decrease above and below the LLJ. The frequencies of LLJs are sensitive to the choice of the relative criterion, i.e., if the value for the relative decrease exceeds 15%. The LLJs are evaluated with respect to the frequency distributions of height, speed, directional shear and stability for different regions. LLJs are most frequent in the katabatic wind regime over the ice sheet and in barrier wind regions. During winter, katabatic LLJs occur with frequencies of more than 70% in many areas. Katabatic LLJs show a narrow range of heights (mostly below 200 m) and speeds (typically 10–20 m/s), while LLJs over the sea ice cover a broad range of speeds and heights. LLJs are associated with surface inversions or low-level lifted inversions. LLJs in the katabatic wind and barrier wind regions can last several days during winter. The duration of LLJs is sensitive to the LLJ definition criteria. We propose to use only the absolute criterion for model studies.
A model-based temperature adjustment scheme for wintertime sea-ice production retrievals from MODIS
(2022)
Knowledge of the wintertime sea-ice production in Arctic polynyas is an important requirement for estimations of the dense water formation, which drives vertical mixing in the upper ocean. Satellite-based techniques incorporating relatively high resolution thermal-infrared data from MODIS in combination with atmospheric reanalysis data have proven to be a strong tool to monitor large and regularly forming polynyas and to resolve narrow thin-ice areas (i.e., leads) along the shelf-breaks and across the entire Arctic Ocean. However, the selection of the atmospheric data sets has a large influence on derived polynya characteristics due to their impact on the calculation of the heat loss to the atmosphere, which is determined by the local thin-ice thickness. In order to overcome this methodical ambiguity, we present a MODIS-assisted temperature adjustment (MATA) algorithm that yields corrections of the 2 m air temperature and hence decreases differences between the atmospheric input data sets. The adjustment algorithm is based on atmospheric model simulations. We focus on the Laptev Sea region for detailed case studies on the developed algorithm and present time series of polynya characteristics in the winter season 2019/2020. It shows that the application of the empirically derived correction decreases the difference between different utilized atmospheric products significantly from 49% to 23%. Additional filter strategies are applied that aim at increasing the capability to include leads in the quasi-daily and persistence-filtered thin-ice thickness composites. More generally, the winter of 2019/2020 features high polynya activity in the eastern Arctic and less activity in the Canadian Arctic Archipelago, presumably as a result of the particularly strong polar vortex in early 2020.
The larval stage of the European fire salamander (Salamandra salamandra) inhabits both lentic and lotic habitats. In the latter, they are constantly exposed to unidirectional water flow, which has been shown to cause downstream drift in a variety of taxa. In this study, a closed artificial creek, which allowed us to keep the water flow constant over time and, at the same time, to simulates with predefined water quantities and durations, was used to examine the individual movement patterns of marked larval fire salamanders exposed to unidirectional flow. Movements were tracked by marking the larvae with VIAlpha tags individually and by using downstream and upstream traps. Most individuals showed stationarity, while downstream drift dominated the overall movement pattern. Upstream movements were rare and occurred only on small distances of about 30 cm; downstream drift distances exceeded 10 m (until next downstream trap). The simulated flood events increased drift rates significantly, even several days after the flood simulation experiments. Drift probability increased with decreasing body size and decreasing nutritional status. Our results support the production hypothesis as an explanation for the movements of European fire salamander larvae within creeks.
The presence of sea ice leads in the sea ice cover represents a key feature in polar regions by controlling the heat exchange between the relatively warm ocean and cold atmosphere due to increased fluxes of turbulent sensible and latent heat. Sea ice leads contribute to the sea ice production and are sources for the formation of dense water which affects the ocean circulation. Atmospheric and ocean models strongly rely on observational data to describe the respective state of the sea ice since numerical models are not able to produce sea ice leads explicitly. For the Arctic, some lead datasets are available, but for the Antarctic, no such data yet exist. Our study presents a new algorithm with which leads are automatically identified in satellite thermal infrared images. A variety of lead metrics is used to distinguish between true leads and detection artefacts with the use of fuzzy logic. We evaluate the outputs and provide pixel-wise uncertainties. Our data yield daily sea ice lead maps at a resolution of 1 km2 for the winter months November– April 2002/03–2018/19 (Arctic) and April–September 2003–2019 (Antarctic), respectively. The long-term average of the lead frequency distributions show distinct features related to bathymetric structures in both hemispheres.
Two areas were selected to represent major process regimes of Mediterranean rangelands. In the County of Lagads (Greece), situated east of the city of Thessaloniki, livestock grazing with sheep and goats is a major factor of the rural economy. In suitable areas, it is complemented by agricultural use. The region of Ayora (Spain) is located west of the city of Valencia. It is one of regions most affected by fires in Spain. First of all, long time series of satellite data were compiled for both regions on the basis of Landsat sensors, which cover the time until 1976 (Ayora) and 1984 (Lagadas) with one image per year. Using a rigorous processing scheme, the data were geometrically and radiometrically corrected Specific attention was given to an exact sensor calibration, the radiometric intercalibration of Landsat-TM and "MSS. Proportional cover of photosynthetically active vegetation was identified as a suitable quantitative indicator for assessing the state of rangelands. Using Spectral Mixture Analysis (SMA) it was inferred for all data sets. The extensive data base procured this way enabled to map fire events in the Ayora area based on sequential diachronic sets and provide fire dates, perimeter as well as fire recurrence for each pixel. The increasing fire frequency in the past decades is in large parts attributed to the accelerated abandonment of the area that leads to an encroachment of shrublands and the accumulation of combustible biomass. On the basis of the fire mapping results, a spatial and temporal stratification of the data set allowed to asses plant recovery dynamics on the landscape level through linear trend analysis. The long history of fire events in the Mediterranean frequently leads to processes of auto-succession. Following an initial dominance of herbaceous vegetation this commonly leads to similar plant communities as the ones present before the fire. On a temporal axis, this results in typical exponential post-fire trajectories which could also be shown in this study. The analysis of driving factors for post-fire dynamics confirmed the importance of aspect and slope. Locations with lower amounts of solar irradiation and favourable water supply yielded faster recovery rates and higher post-fire vegetation cover levels. In most cases, the vegetation cover levels observed before the fire were not reached within the post-fire observation period. In the area of Lagadas, linear trend analysis and additional statistical parameters were used to infer a degradation index. This could be used to illustrate a complex pattern of stability, regeneration and degradation of vegetation cover. These different processes and states are found in close proximity and are clearly determined by topography and elevation. Following a sequence of analyses, it was found that in particular steep, narrow valleys show positive trends, while negative trends are more abundant on plain or gently undulating areas. Considering the local grazing regime, this spatial differentiation was related to the accessibility of specific locations. Subsequently, animal numbers on community level were used to calculate efficient stocking rates and assess the temporal development of their relation with vegetation cover. This calculation of temporal trajectories illustrated that only some communities show the expected negative relation. To the contrary, a positive relation or even changing relation patterns are observed. This signifies recent concentration and intensification processes in the grazing scheme, as a result of which animals are kept in sheds, where additional feedstuffs are provided. In these cases, free roaming of livestock animals is often confined to some hours every day, which explains the spatial preference of easily accessible areas by the shepherds. Beyond these temporal trends, it was analysed whether the grazing pattern is equally reflected in a spatial trend. Making use of available geospatial information layers, the efforts required to reach each location was expressed as a cost. Then, cost zones could be defined and woody vegetation cover as a grazing indicator could be inferred for the different zones. Animal sheds were employed as starting features for this piospheric analysis, which could be mapped from very high spatial resolution Quickbird image data. The result was a clearly structured gradient showing increasing woody vegetation cover with increasing cost distance. On the basis of these two pilot studies, the elements of a monitoring and interpretation framework identified at the beginning of the work were evaluated and a formal interpretation scheme was presented.
A satellite-based climatology of wind-induced surface temperature anomalies for the Antarctic
(2019)
It is well-known that katabatic winds can be detected as warm signatures in the surface temperature over the slopes of the Antarctic ice sheets. For appropriate synoptic forcing and/or topographic channeling, katabatic surges occur, which result in warm signatures also over adjacent ice shelves. Moderate Resolution Imaging Spectroradiometer (MODIS) ice surface temperature (IST) data are used to detect warm signatures over the Antarctic for the winter periods 2002–2017. In addition, high-resolution (5 km) regional climate model data is used for the years of 2002 to 2016. We present a case study and a climatology of wind-induced IST anomalies for the Ross Ice Shelf and the eastern Weddell Sea. The IST anomaly distributions show maxima around 10–15K for the slopes, but values of more than 25K are also found. Katabatic surges represent a strong climatological signal with a mean warm anomaly of more than 5K on more than 120 days per winter for the Byrd Glacier and the Nimrod Glacier on the Ross Ice Shelf. The mean anomaly for the Brunt Ice Shelf is weaker, and exceeds 5K on about 70 days per winter. Model simulations of the IST are compared to the MODIS IST, and show a very good agreement. The model data show that the near-surface stability is a better measure for the response to the wind than the IST itself.
This paper describes the concept of the hyperspectral Earth-observing thermal infrared (TIR) satellite mission HiTeSEM (High-resolution Temperature and Spectral Emissivity Mapping). The scientific goal is to measure specific key variables from the biosphere, hydrosphere, pedosphere, and geosphere related to two global problems of significant societal relevance: food security and human health. The key variables comprise land and sea surface radiation temperature and emissivity, surface moisture, thermal inertia, evapotranspiration, soil minerals and grain size components, soil organic carbon, plant physiological variables, and heat fluxes. The retrieval of this information requires a TIR imaging system with adequate spatial and spectral resolutions and with day-night following observation capability. Another challenge is the monitoring of temporally high dynamic features like energy fluxes, which require adequate revisit time. The suggested solution is a sensor pointing concept to allow high revisit times for selected target regions (1"5 days at off-nadir). At the same time, global observations in the nadir direction are guaranteed with a lower temporal repeat cycle (>1 month). To account for the demand of a high spatial resolution for complex targets, it is suggested to combine in one optic (1) a hyperspectral TIR system with ~75 bands at 7.2"12.5 -µm (instrument NEDT 0.05 K"0.1 K) and a ground sampling distance (GSD) of 60 m, and (2) a panchromatic high-resolution TIR-imager with two channels (8.0"10.25 -µm and 10.25"12.5 -µm) and a GSD of 20 m. The identified science case requires a good correlation of the instrument orbit with Sentinel-2 (maximum delay of 1"3 days) to combine data from the visible and near infrared (VNIR), the shortwave infrared (SWIR) and TIR spectral regions and to refine parameter retrieval.
Measurements of the atmospheric boundary layer (ABL) structure were performed for three years (October 2017–August 2020) at the Russian observatory “Ice Base Cape Baranova” (79.280° N, 101.620° E) using SODAR (Sound Detection And Ranging). These measurements were part of the YOPP (Year of Polar Prediction) project “Boundary layer measurements in the high Arctic” (CATS_BL) within the scope of a joint German–Russian project. In addition to SODAR-derived vertical profiles of wind speed and direction, a suite of complementary measurements at the observatory was available. ABL measurements were used for verification of the regional climate model COSMO-CLM (CCLM) with a 5 km resolution for 2017–2020. The CCLM was run with nesting in ERA5 data in a forecast mode for the measurement period. SODAR measurements were mostly limited to wind speeds <12 m/s since the signal was often lost for higher winds. The SODAR data showed a topographical channeling effect for the wind field in the lowest 100 m and some low-level jets (LLJs). The verification of the CCLM with near-surface data of the observatory showed good agreement for the wind and a negative bias for the 2 m temperature. The comparison with SODAR data showed a positive bias for the wind speed of about 1 m/s below 100 m, which increased to 1.5 m/s for higher levels. In contrast to the SODAR data, the CCLM data showed the frequent presence of LLJs associated with the topographic channeling in Shokalsky Strait. Although SODAR wind profiles are limited in range and have a lot of gaps, they represent a valuable data set for model verification. However, a full picture of the ABL structure and the climatology of channeling events could be obtained only with the model data. The climatological evaluation showed that the wind field at Cape Baranova was not only influenced by direct topographic channeling under conditions of southerly winds through the Shokalsky Strait but also by channeling through a mountain gap for westerly winds. LLJs were detected in 37% of all profiles and most LLJs were associated with channeling, particularly LLJs with a jet speed ≥ 15 m/s (which were 29% of all LLJs). The analysis of the simulated 10 m wind field showed that the 99%-tile of the wind speed reached 18 m/s and clearly showed a dipole structure of channeled wind at both exits of Shokalsky Strait. The climatology of channeling events showed that this dipole structure was caused by the frequent occurrence of channeling at both exits. Channeling events lasting at least 12 h occurred on about 62 days per year at both exits of Shokalsky Strait.
Water-deficit stress, usually shortened to water- or drought stress, is one of the most critical abiotic stressors limiting plant growth, crop yield and quality concerning food production. Today, agriculture consumes about 80-90% of the global freshwater used by humans and about two thirds are used for crop irrigation. An increasing world population and a predicted rise of 1.0-2.5-°C in the annual mean global temperature as a result of climate change will further increase the demand of water in agriculture. Therefore, one of the most challenging tasks of our generation is to reduce the amount water used per unit yield to satisfy the second UN Sustainable Development Goal and to ensure global food security. Precision agriculture offers new farming methods with the goal to improve the efficiency of crop production by a sustainable use of resources. Plant responses to water stress are complex and co-occur with other environmental stresses under natural conditions. In general, water stress causes plant physiological and biochemical changes that depend on the severity and the duration of the actual plant water deficit. Stomatal closure is one of the first responses to plant water stress causing a decrease in plant transpiration and thus an increase in plant temperature. Prolonged or severe water stress leads to irreversible damage to the photosynthetic machinery and is associated with decreasing chlorophyll content and leaf structural changes (e.g., leaf rolling). Since a crop can already be irreversibly damaged by only mild water deficit, a pre-visual detection of water stress symptoms is essential to avoid yield loss. Remote sensing offers a non-destructive and spatio-temporal method for measuring numerous physiological, biochemical and structural crop characteristics at different scales and thus is one of the key technologies used in precision agriculture. With respect to the detection of plant responses to water stress, the current state-of-the-art hyperspectral remote sensing imaging techniques are based on measurements of thermal infrared emission (TIR; 8-14 -µm), visible, near- and shortwave infrared reflectance (VNIR/SWIR; 0.4-2.5 -µm), and sun-induced fluorescence (SIF; 0.69 and 0.76 -µm). It is, however, still unclear how sensitive these techniques are with respect to water stress detection. Therefore, the overall aim of this dissertation was to provide a comparative assessment of remotely sensed measures from the TIR, SIF, and VNIR/SWIR domains for their ability to detect plant responses to water stress at ground- and airborne level. The main findings of this thesis are: (i) temperature-based indices (e.g., CWSI) were most sensitive for the detection of plant water stress in comparison to reflectance-based VNIR/SWIR indices (e.g., PRI) and SIF at both, ground- and airborne level, (ii) for the first time, spectral emissivity as measured by the new hyperspectral TIR instrument could be used to detect plant water stress at ground level. Based on these findings it can be stated that hyperspectral TIR remote sensing offers great potential for the detection of plant responses to water stress at ground- and airborne level based on both TIR key variables, surface temperature and spectral emissivity. However, the large-scale application of water stress detection based on hyperspectral TIR measures in precision agriculture will be challenged by several problems: (i) missing thresholds of temperature-based indices (e.g., CWSI) for the application in irrigation scheduling, (ii) lack of current TIR satellite missions with suitable spectral and spatial resolution, (iii) lack of appropriate data processing schemes (including atmosphere correction and temperature emissivity separation) for hyperspectral TIR remote sensing at airborne- and satellite level.
Although gravitropism forces trees to grow vertically, stems have shown to prefer specific orientations. Apart from wind deforming the tree shape, lateral light can result in prevailing inclination directions. In recent years a species dependent interaction between gravitropism and phototropism, resulting in trunks leaning down-slope, has been confirmed, but a terrestrial investigation of such factors is limited to small scale surveys. ALS offers the opportunity to investigate trees remotely. This study shall clarify whether ALS detected tree trunks can be used to identify prevailing trunk inclinations. In particular, the effect of topography, wind, soil properties and scan direction are investigated empirically using linear regression models. 299.000 significantly inclined stems were investigated. Species-specific prevailing trunk orientations could be observed. About 58% of the inclination and 19% of the orientation could be explained by the linear models, while the tree species, tree height, aspect and slope could be identified as significant factors. The models indicate that deciduous trees tend to lean down-slope, while conifers tend to lean leeward. This study has shown that ALS is suitable to investigate the trunk orientation on larger scales. It provides empirical evidence for the effect of phototropism and wind on the trunk orientation.
Amphibian diversity in the Amazonian floating meadows: a Hanski core-satellite species system
(2021)
The Amazon catchment is the largest river basin on earth, and up to 30% of its waters flow across floodplains. In its open waters, floating plants known as floating meadows abound. They can act as vectors of dispersal for their associated fauna and, therefore, can be important for the spatial structure of communities. Here, we focus on amphibian diversity in the Amazonian floating meadows over large spatial scales. We recorded 50 amphibian species over 57 sites, covering around 7000 km along river courses. Using multi-site generalised dissimilarity modelling of zeta diversity, we tested Hanski's core-satellite hypothesis and identified the existence of two functional groups of species operating under different ecological processes in the floating meadows. ‘Core' species are associated with floating meadows, while ‘satellite' species are associated with adjacent environments, being only occasional or accidental occupants of the floating vegetation. At large scales, amphibian diversity in floating meadows is mostly determined by stochastic (i.e. random/neutral) processes, whereas at regional scales, climate and deterministic (i.e. niche-based) processes are central drivers. Compared with the turnover of ‘core' species, the turnover of ‘satellite' species increases much faster with distances and is also controlled by a wider range of climatic features. Distance is not a limiting factor for ‘core' species, suggesting that they have a stronger dispersal ability even over large distances. This is probably related to the existence of passive long-distance dispersal of individuals along rivers via vegetation rafts. In this sense, Amazonian rivers can facilitate dispersal, and this effect should be stronger for species associated with riverine habitats such as floating meadows.
For grape canopy pixels captured by an unmanned aerial vehicle (UAV) tilt-mounted RedEdge-M multispectral sensor in a sloped vineyard, an in situ Walthall model can be established with purely image-based methods. This was derived from RedEdge-M directional reflectance and a vineyard 3D surface model generated from the same imagery. The model was used to correct the angular effects in the reflectance images to form normalized difference vegetation index (NDVI)orthomosaics of different view angles. The results showed that the effect could be corrected to a certain scope, but not completely. There are three drawbacks that might restrict a successful angular model construction and correction: (1) the observable micro shadow variation on the canopy enabled by the high resolution; (2) the complexity of vine canopies that causes an inconsistency between reflectance and canopy geometry, including effects such as micro shadows and near-infrared (NIR) additive effects; and (3) the resolution limit of a 3D model to represent the accurate real-world optical geometry. The conclusion is that grape canopies might be too inhomogeneous for the tested method to perform the angular correction in high quality.
A sustainable development of forests and their ecosystem services requires the monitoring of the forests" state and changes as well as the prediction of their future development. To achieve the latter, eco-physiological forest growth models are usually applied. These models require calibration and validation with forestry reference data. This data includes forest structural parameters such as tree height or stem diameter which are easy to measure and can be used to estimate the core model parameters, i.e. the tree- biomass pools. The methods traditionally applied to derive the structural parameters are mainly manual and time-consuming. Hence, the in situ data acquisition is inefficient and limited in its ability to capture the vertical and horizontal variability in stand structure. Ground-based remote sensing bears the potential to overcome the limitations of the traditional methods. As they can be automated, ground-based remote sensing methods allow a much more efficient data acquisition and a larger spatial coverage. They are also able to capture forest structure in its three dimensions. Nevertheless, at present further research is required, in particular with respect to the practical integration of ground-based remote sensing data into forest growth models as well as regarding factors influencing the structural parameter retrieval from this data. Therefore, the goal of this PhD thesis was to investigate the influencing factors of two ground-based remote sensing methods (terrestrial laser scanning and hemispherical photography), which have not or only scarcely been studied to date. In addition, the use of forest structural parameters derived from these methods for the calibration of a forest growth model was assessed. Both goals were achieved. The results of this thesis could contribute significantly to a comprehensive assessment of ground-based remote sensing and its potential to derive the forest structural parameters. However, the use of these methods to calibrate forest growth models proved to be limited. An optimized data sampling design is expected to eliminate the major limitations, though. Furthermore, the combination of ground-based, airborne, and satellite remote sensing sensors was suggested to provide an optimized framework for the general integration of remotely sensed data into forest growth models. This combination of remote sensing observations at different scales will contribute greatly to a modern forest management with the purpose of warranting a sustainable forest development even under growing economic and ecological pressures.
Dry tropical forests are facing massive conversion and degradation processes and they are the most endangered forest type worldwide. One of the largest dry forest types are Miombo forests that stretch across the Southern African subcontinent and the proportionally largest part of this type can be found in Angola. The study site of this thesis is located in south-central Angola. The country still suffers from the consequences of the 27 years of civil war (1975-2002) that provides a unique socio-economic setting. The natural characteristics are a representative cross section which proved ideal to study underlying drivers as well as current and retrospective land use change dynamics. The major land change dynamic of the study area is the conversion of Miombo forests to cultivation areas as well as modification of forest areas, i.e. degradation, due to the extraction of natural resources. With future predictions of population growth, climate change and large scale investments, land pressure is expected to further increase. To fully understand the impacts of these dynamics, both, conversion and modification of forest areas were assessed. By using the conceptual framework of ecosystem services, the predominant trade-off between food and timber in the study area was analyzed, including retrospective dynamics and impacts. This approach accounts for products that contribute directly or indirectly to human well-being. For this purpose, data from the Landsat archive since 1989 until 2013 was applied in different study area adapted approaches. The objectives of these approaches were (I) to detect underlying drivers and their temporal and spatial extent of impact, (II) to describe modification and conversion processes that reach from times of armed conflicts over the ceasefire and the post-war period and (III) to provide an assessment of drivers and impacts in a comparative setting. It could be shown that major underlying drivers for the conversion processes are resettlement dynamics as well as the location and quality of streets and settlements. Furthermore, forests that are selectively used for resource extraction have a higher chance of being converted to a field. Drivers of forest degradation are on one hand also strongly connected to settlement and infrastructural structures. But also to a large extent to fire dynamics that occur mostly in more remote and presumably undisturbed forest areas. The loss of woody biomass as well as its slow recovery after the abandonment of fields could be quantified and stands in large contrast to the amount of potentially cultivated food that is necessarily needed. The results of the thesis support the fundamental understanding of drivers and impacts in the study area and can thus contribute to a sustainable resource management.
The parameterization of the boundary layer is a challenge for regional climate models of the Arctic. In particular, the stable boundary layer (SBL) over Greenland, being the main driver for substantial katabatic winds over the slopes, is simulated differently by different regional climate models or using different parameterizations of the same model. However, verification data sets with high-resolution profiles of the katabatic wind are rare. In the present paper, detailed aircraft measurements of profiles in the katabatic wind and automatic weather station data during the experiment KABEG (Katabatic wind and boundary-layer front experiment around Greenland) in April and May 1997 are used for the verification of the regional climate model COSMO-CLM (CCLM) nested in ERA-Interim reanalyses. CCLM is used in a forecast mode for the whole Arctic with 15 km resolution and is run in the standard configuration of SBL parameterization and with modified SBL parameterization. In the modified version, turbulent kinetic energy (TKE) production and the transfer coefficients for turbulent fluxes in the SBL are reduced, leading to higher stability of the SBL. This leads to a more realistic representation of the daily temperature cycle and of the SBL structure in terms of temperature and wind profiles for the lowest 200 m.