1,197 research outputs found
Optical measurements of bare ice and melt ponds on Arctic sea ice acquired during POLARSTERN cruise PS106
No full textThe dataset contains two different datasets: 1) Gege, Peter; König, Marcel; Oppelt, Natascha: Reflectance measurements (Ocean Optics STS-VIS) of bare ice and melt ponds on Arctic sea ice acquired during POLARSTERN cruise PS106. 2) Gege, P; König, M (2019): HCRF measurements (Ibsen Freedom VIS FSV-305) of bare Arctic sea ice acquired during POLARSTERN cruise PS106. The first dataset also contains a table with depth information and field photographs. The second dataset also contains photographs
Airborne Visible/Infrared Imaging spectrometer AVIS: Design, characterization and calibration
No full textThe Airborne Visible/Infrared imaging Spectrometer AVIS is a hyperspectral imager designed for environmental monitoring purposes. The sensor, which was constructed entirely from commercially available components, has been successfully deployed during several experiments between 1999 and 2007. We describe the instrument design and present the results of laboratory characterization and calibration of the system's second generation, AVIS-2, which is currently being operated. The processing of the data is described and examples of remote sensing reflectance data are presented
Outbreak of Moroccan locust in Sardinia (Italy): a remote sensing perspective
No full textThe Moroccan locust has been considered one of the most dangerous agricultural pests in the Mediterranean region. The economic importance of its outbreaks diminished during the second half of the 20th century due to a high degree of agricultural industrialization and other human-caused transformations of its habitat. Nevertheless, in Sardinia (Italy) from 2019 on, a growing invasion of this locust species is ongoing, being the worst in over three decades. Locust swarms destroyed crops and pasture lands of approximately 60,000 ha in 2022. Drought, in combination with increasing uncultivated land, contributed to forming the perfect conditions for a Moroccan locust population upsurge. The specific aim of this paper is the quantification of land cover land use (LCLU) influence with regard to the recent locust outbreak in Sardinia using remote sensing data. In particular, the role of untilled, fallow, or abandoned land in the locust population upsurge is the focus of this case study. To address this objective, LCLU was derived from Sentinel-2A/B Multispectral Instrument (MSI) data between 2017 and 2021 using time-series composites and a random forest (RF) classification model. Coordinates of infested locations, altitude, and locust development stages were collected during field observation campaigns between March and July 2022 and used in this study to assess actual and previous land cover situation of these locations. Findings show that 43% of detected locust locations were found on untilled, fallow, or uncultivated land and another 23% within a radius of 100 m to such areas. Furthermore, oviposition and breeding sites are mostly found in sparse vegetation (97%). This study demonstrates that up-to-date remote sensing data and target-oriented analyses can provide valuable information to contribute to early warning systems and decision support and thus to minimize the risk concerning this agricultural pest. This is of particular interest for all agricultural pests that are strictly related to changing human activities within transformed habitats
Monitoring of Plant Chlorophyll and Nitrogen Status Using the Airborne Imaging Spectrometer AVIS
No full textAirborne hyperspectral remote sensing enables not only spatial monitoring of vegetation
cover, but also the derivation of individual plant constituents such as chlorophyll and
nitrogen content. These are important parameters for optimised agricultural management
on a field basis through the possibility of spatially differentiated fertilisation and for
hydrological and vegetation yield modelling.
The use of existing airborne imaging spectrometers is cost-intensive. Moreover, it is
difficult to obtain these sensors for multitemporal applications. The imaging spectrometer
AVIS (Airborne Visible/Near Infrared Imaging Spectrometer) was built at the Chair of
Geography and Geographical Remote Sensing of the Ludwig Maximilians University
Munich, Germany, to overcome these difficulties. AVIS is designed as a cost-effective tool
for environmental monitoring using commonly available components. AVIS enables the
deployment of a hyperspectral sensor for both scientific research and educational
purposes. It is based on a direct sight spectrograph coupled to a standard B/W CCD
camera. The signal received by the CCD is read out and sent via a frame grabber card to a
personal computer, where the data is stored on the hard disc together with additional GPS
data. The radiometric, spectral and geometric properties of AVIS resulting from the
calibration procedure are summarised in Table 7-1.
Table 7-1: AVIS characteristics
Parameter Description
Spectral range 553-999nm
Spectral resolution 6nm
Spectral sampling rate / resampling 2nm / 6nm
Number of used bands 74
SNR 45dB (year 1999), 47dB (year 2000)
Spatial resolution 300 pixels per image line
Spatial sampling rate 390 pixels per image line
FOV 1.19rad
IFOV across track 3.1mrad
IFOV along track 2.98mrad
One aim of this thesis was to test the potential of AVIS for the purpose of environmental
monitoring, especially of the chlorophyll and nitrogen status of plants. The land cover
types under investigation were grassland, maize ( Zea mays L.) and winter wheat ( Triticum
aestivum L.). Within this scope, a total of 21 AVIS flights were carried out during the
vegetation periods of the years 1999 and 2000. The AVIS data were preprocessed before analysis, including dark current and flat field correction, resampling as well as atmospheric
correction and reflectance calibration.
The test area chosen for the validation of the AVIS data is located in the northern
Bavarian foothills, 25km southwest of Munich, Germany (48° 6’ N, 11° 17’ E). It is situated
between the Ammersee in the west and the Starnberger See in the east. The
municipalities Gilching and Andechs define the northern and southern borders
respectively.
Within this area, three water protection areas were chosen as test sites. In these test
sites, most of the farmers are under contract to the local agricultural office “ Amt für
Landwirtschaft” resulting in detailed management data for each field. This data include
useful information for the interpretation of ground and AVIS data. Two weather stations of
the Bavarian network of agro-meteorological stations, namely No.72 (Gut Hüll) and No.80
(Rothenfeld), are located in the test area and provide information about precipitation,
temperature and radiation. Ten and thirteen stands were selected as test fields in 1999
and 2000 respectively, including three fields each of maize and wheat in 1999 as well as
three fields of maize and six fields of wheat in 2000. During both years, four meadows
were investigated belonging to the same plant community ( Arrhenatherion elatioris). The
meadows differ in the utilisation intensity (non-fertilised meadow with one cut, meadow
with one cut, meadow with rotational grazing and meadow with four to five cuts).
The ground truth campaigns included weekly measurements of plant parameters, such as
height, dry and wet biomass, phenological stage, chlorophyll and nitrogen content, as well
as a photographic documentation for each field.
The chlorophyll and nitrogen measurements, which were derived from the sampling on
ground, are available in contents per area [g/m²] and in contents per mass ([mg/g] for
chlorophyll and [%DM] for nitrogen). The former can be used to evaluate the
photosynthetic capacity or productivity of a canopy, which is an important input parameter
for hydrological or vegetation models; the latter may be an indicator for plant physiological
status or level of stress, which is a valuable source of information for optimising field
management.
The relationship between chlorophyll and nitrogen based on the ground measurements
showed that a differentiation of the land cover types is necessary for significant
correlation. When the plant species are investigated separately, the chlorophyll and
nitrogen content per area are always highly correlated, especially for chlorophyll a and
total chlorophyll content (r²≥0.8). For all investigated land cover types, the nitrogen and
chlorophyll contents per mass are uncorrelated. For wheat, the results improve when the
phenological state and the cultivar are considered (r²>0.67). For maize, distinct variations
in the chlorophyll content per mass during the vegetation period reduced correlation with these parameters. The use of a fitted chlorophyll trend curve instead of the original
measurements does not lead to a significant improvement of the results.
For grassland, no significant correlation above r²=0.67 could be observed except for
chlorophyll and nitrogen, both per area, where a decreasing strength of correlation could
be monitored with increasing fertilisation level.
These results lead to the conclusion that the chlorophyll and nitrogen contents per mass
of the investigated land covers are decoupled when the compensation point for effective
photosynthesis is exceeded. Beyond this limit the nitrogen in the plants is no longer
incorporated into chlorophylls, but mainly into proteins, alkaloids and nucleic acids,
whereas the proteins especially are used for internal storage of nitrogen.
The derivation of the chlorophyll and nitrogen content of the plant leaves on a mean field
basis was conducted using three hyperspectral spectral approaches, namely the
hyperspectral NDVI (hNDVI), the Optimised Soil Adjusted Vegetation Index OSAVI as well
as the relatively unknown Chlorophyll Absorption Integral CAI. The multispectral NDVITM
was simulated as established reference.
The results of the derivation of both chlorophyll and nitrogen content of plants with the
investigated approaches depend strongly on a priori knowledge about the canopies
monitored. In general, the use of contents per area rather than contents per mass has
been found more suitable for the investigated remote sensing applications.
A significant correlation between any index and the chlorophyll or nitrogen content for the
whole sample size could not be derived. The optimal spectral approach for derivation is
species-dependent, but also dependent on the cultivar. The chlorophyll and nitrogen level
of the plants under observation as well as their temperature sensitivity mainly caused this
dependence. The NDVITM, hNDVI and OSAVI became insensitive for high chlorophyll
content above about 1g/m² (1.5mg/g) chlorophyll a and 0.2g/m² (0.4mg/g) chlorophyll b,
respectively. A saturation of the indices was also found for nitrogen content above
2.5g/m². The saturation limit of nitrogen in percentage of dry matter could be rated at
about 4%. The positive correlation between the indices and this parameter for wheat
leads to insensitivity at values above this limit, while the negative correlation for maize
results in saturation for values below 2.5%.
The CAI is not affected by saturation as much as the other spectral approaches, leading to
higher coefficients of determination, especially for contents per area. The CAI becomes
insensitive at chlorophyll contents per area above 2g/m². The results lead to the
assumption, that the flattening and narrowing of the chlorophyll absorption feature at
680nm most probably causes the saturation of the NDVITM, hNDVI and OSAVI. The ratios
are directly affected by an increase in reflectance in the red wavelength region. The high
correlations between the CAI and contents per area can be ascribed to the fact that the
CAI is based on an integrated measurement over an area and therefore is less affected by an increase of reflectance in the red wavelengths. The CAI probably becomes insensitive
at the point where the narrowing of the absorption feature leads to a shift of the red edge
position towards the blue wavelength region. This saturation limit lies at approximately 2g
chlorophyll per m².
In contrast, the chlorophyll content per mass, which indicates the plant’s physiological
status or level of stress, could be estimated more accurately using spectral indices such as
hNDVI and OSAVI, especially for wheat. The low correlations derived for maize are caused
by its higher temperature dependence, leading to daily variations in the chlorophyll
content per mass.
The chlorophyll and nitrogen contents of the grassland canopies could not be derived with
the spectral approaches investigated. When the meadows were investigated separately,
correlations could only be found between the CAI and the chlorophyll content per area for
the most intensely utilised meadow (four to five cuts), which on the one side is
characterised by the highest level of fertilisation, but on the other side is affected by the
highest nutrient offtake. The low potential of the investigated indices can be mainly
assigned to the fact that the chlorophyll and nitrogen values of the meadows mostly
exceeded the saturation limits of the applied indices.
The possibility of deriving chlorophyll and nitrogen accurately enough to map within field
heterogeneities was discussed on the basis of a wheat field, which was analysed
separately at three sampling points for chlorophyll and nitrogen content. The approaches
found to be most suitable for the parameter estimation of wheat were applied. The CAI
was used for the estimation of the chlorophyll content per area and mass as well as for
the nitrogen content per area. The hNDVI was applied to estimate the canopy’s nitrogen
content per mass. Both approaches were able to reproduce the chlorophyll contents of the
different sampling points accurately enough to derive the differences between the
measurement points when the saturation limits were not exceeded. Beyond these limits
the index values decreased with increasing measurement values.
The spatial pattern of the nutrient supply was discussed by comparing nitrogen pattern
images, which were derived from CAI measurements acquired in 2000 with the yield
measurement map of the same field. The phenological stage of stem elongation (EC 30)
turned out to be most suitable for the derivation of the nitrogen pattern. On the one hand,
the crop condition at these stages determine yield and on the other hand the nitrogen
pattern images were able to map the inner field patterns of nitrogen supply. After anthesis
the nitrogen images can map areas with different degrees of maturity. Therefore they can
be used for the monitoring of maturity stages for the determination of the most favourable
harvest date.
As described here, AVIS is still in its early stages. It has the potential to become a costeffectiveAVIS2, which covers the spectral range of 400-900nm, has been in commercial use since
2001.
tool for the monitoring of the environment. A modification of AVIS, namelyDie Arbeit mit hyperspektralen Fernerkundungssensoren ermöglicht nicht nur eine
flächenhafte Aufnahme der Vegetationsdecke, sondern vor allem auch die Beurteilung des
phänologischen und gesundheitlichen Zustandes der Pflanzen. Dies geschieht über die
Ableitung einzelner Pflanzeninhaltsstoffe, wie z. B. Chlorophyll und Stickstoff, beides
bedeutende Parameter für ein optimales Feldmanagement . Daneben spielen diese
Pflanzeninhaltsstoffe eine bedeutende Rolle als Inputparameter für hydrologische und
pflanzenkundliche Modelle.
Da sich derzeit noch keine operationell arbeitenden, satellitengestützten Spektrometer im
Orbit befinden, beschränkt sich die flächenhafte Anwendung von hyperspektralen
Fernerkundungssensoren auf den Einsatz flugzeuggetragener Spektrometer. Die Arbeit mit
kommerziellen Sensoren, wie AVIRIS, DAIS, HYMAP oder ROSIS, ist aber mit einem hohen
finanziellen Aufwand verbunden. Eine für das Vegetationsmonitoring erforderliche
multitemporale Anwendung wird sowohl durch die hohen Kosten als auch durch die
limitierte Verfügbarkeit dieser Systeme erschwert. Diese Einschränkungen gaben am
Institut für Geographie der Ludwig-Maximilians-Universität München den Anlass für die
Entwicklung und den Bau eines institutseigenen flugzeuggetragenen abbildenden
Spektrometers. Das vorrangige Ziel dabei war ein kostengünstiges System für Forschung
und Lehre. Diese Vorgaben führten zur Entwicklung des flugzeuggetragenen abbildenden
Spektrometers AVIS (Airborne Visible/near Infrared imaging Spektrometer).
Diese Arbeit beschäftigt sich sowohl mit der Kalibrierung als auch dem Einsatz von AVIS
im Rahmen eines von der Deutschen Forschungsgemeinschaft DFG geförderten Projektes
„Bestimmung des Stickstoffgehaltes von Vegetation – ein Beitrag zur deutschen BAHC
Forschung“ (DFG MA 875 6).
Die Kalibrierung von AVIS beinhaltet eine Beschreibung des Aufbaus mit den daraus
resultierenden radiometrischen, spektralen und geometrischen Eigenschaften des
Systems: AVIS ist ein Zeilenscanner, d.h. eine Bildzeile repräsentiert eine Aufnahme.
Durch die Bewegung des Sensors über der Erdoberfläche hinweg entsteht durch die
Aneinanderreihung mehrerer Aufnahmen ein Bildstreifen. Der Kern von AVIS ist ein direct
sight Spektrograph, der zwischen ein Objektiv und eine Standard schwarz-weiß
Videokamera montiert ist. Das einfallende Licht wird im Objektiv gebündelt und passiert
dann den Spektrographen, wo es entlang einer spektralen Achse in verschiedene
Wellenlängen dispergiert wird. Im Fall von AVIS wird für jeden Bildpunkt einer Zeile die
spektrale Information in 240 einzelnen Wellenlängen oder Kanälen abgebildet. Die
Information wird auf dem CCD der Videokamera als elektrische Ladung registriert und
über eine Frame-Grabber-Karte auf der Festplatte eines angeschlossenen PCs gespeichert.
Die Daten eines an AVIS gekoppelten GPS-Gerätes, wie z.B. geographische Länge und Breite, Flughöhe über NN und Zeitpunkt der Aufnahme, werden in einem header für jede
Bildzeile gespeichert.
Die radiometrischen, spektralen und geometrischen Eigenschaften, welche sich aus der
Kalibrierung von AVIS ergeben, sind in Tabelle 8-1 zusammengefasst.
Tabelle 8-1: AVIS Spezifikationen
Parameter Beschreibung
Spektralbereich 553-999nm
Spektrale Auflösung 6nm
Spektrale Abtastrate / Resamplingrate 2nm / 6nm
Anzahl verwendeter Kanäle 74
Signal-Rausch-Verhältnis 45dB (Jahr 1999), 47dB (Jahr 2000)
Räumliche Auflösung 300 Pixel pro Bildzeile
Räumliche Abtastrate 390 Pixel pro Bildzeile
FOV 1.19rad
IFOV across track 3.1mrad
IFOV along track 2.98mrad
Der Einsatz von AVIS in der Vegetationsaufnahme, und hier speziell die Bestimmung des
Chlorophyll- und Stickstoffgehaltes von Pflanzen, wird anhand drei verschiedener
Landnutzungstypen erprobt, nämlich Mais ( Zea mays L.), (Winter-) Weizen ( Triticum
aestivum L.) und Grünland. Dabei beschränken sich die Untersuchungen auf die Blätter
der Pflanzen.
Die Untersuchung der Landnutzungstypen erfolgte während der Vegetationsperioden der
Jahre 1999 und 2000 in einem Testgebiet im nördlichen Alpenvorland, 25km südwestlich
von München. Das Untersuchungsgebiet erstreckt sich von der Stadt Gilching im Norden
bis zur Gemeinde Andechs im Süden. Die westliche bzw. östliche Grenze bilden der
Ammersee und der Starnberger See. Innerhalb dieses Untersuchungsgebietes wurden drei
Wasserschutzgebiete gewählt, in welchen die Testfelder liegen. Diese Gebiete zeichnen
sich dadurch aus, dass die Mehrzahl der Landwirte vertraglich an das örtliche
Landwirtschaftsamt gebunden ist. Diese Verträge beinhalten u.a. die genaue Aufzeichnung
der Bewirtschaftung im Rahmen der sog. Schlagkartei und stellen damit eine wertvolle
Informationsquelle dar. Des weiteren ermöglichen zwei Wetterstationen des Bayerischen
agrarmeteorologischen Messnetzes (Nr.72 „Gut Hüll“ und Nr.80 „Rothenfeld“) die
Erfassung der meteorologischer Daten innerhalb des Untersuchungsgebietes in einer
stündlichen Auflösung. Im Jahr 1999 wurden insgesamt zehn Testfelder untersucht, wobei je drei Felder mit
Winterweizen (Sorte Bussard) und Mais (Sorte Narval und Sortenmischung Bristol/Korus)
einbezogen waren. Im Jahr 2000 wurden sechs Weizenfelder (Sorten Bussard und Capo)
und drei Maisfelder (Sorte Magister) untersucht. Außerdem wurden über beide Jahre
hinweg vier Felder mit der Nutzung als permanentes Grünland bearbeitet (einschürig
ungedüngt, einschürig gedüngt, vier- bis fünfschürig und Mähweide).
Im Laufe der Vegetationsperioden von 1999 und 2000 wurden im Untersuchungsgebiet
insgesamt 21 AVIS Überflüge durchgeführt. Dabei wurden die Testgebiete aus einer Höhe
von 4000ft bzw. 10000ft über NN erfasst, was bei einer mittleren Geländehöhe von 680m
zu einer räumlichen Pixelauflösung von 3 bzw. 10m führt. Vor der quantitativen
Auswertung der hyperspektralen Daten mussten die Rohdaten vorprozessiert werden. Dies
beinhaltete folgende Korrekturen: a) die Korrektur des Dunkelstromes und den Ausgleich
von Inhomogenitäten des CCD’s (Flatfield); b) ein Resampling der ursprünglich 240 Kanäle
mit einer Abtastrate von 2nm zu einem 80-kanaligem Datensatz mit einer Abtastrate von
6nm, welche der spektralen Auflösung von AVIS entspricht; c) Atmosphärenkorrektur und
Reflexionskalibrierung.
Die bodengestützte Geländekampagne beinhaltete wöchentlich durchgeführte Messungen
verschiedener Pflanzenparameter wie Höhe des Triebes und der Blätter, feuchte und
trockene Biomasse, phänologischer Zustand, Chlorophyll- und Stickstoffgehalt getrennt
nach Blatt, Stängel und Frucht. Außerdem wurde jedes Feld zu Dokumentationszwecken
wöchentlich fotografiert.
Die Chlorophyll- und Stickstoffgehalte, welche von den bodengestützten Messungen
abgeleitet wurden, liegen in Gehalten pro Fläche [g/m²] und in Gehalten pro Masse (bei
Chlorophyll [mg/g] und bei Stickstoff [% der trockenen Biomasse]). Mit Hilfe des Gehaltes
pro Fläche können Aussagen über die photosynthetische Produktivität oder Kapazität eines
Bestandes getroffen werden – ein wichtiger Eingabeparameter für hydrologische oder
vegetationskundliche Modelle. Gehalte pro Masse dagegen geben Aufschluss über den
physiologischen Zustand der Pflanzen sowie über Auswirkungen von Stress oder
Krankheiten – wichtige Informationen für ein optimales Feldmanagement durch den
Landwirt.
Der in den Pflanzen befindliche Stickstoff weist im sichtbaren und nahen infraroten
Wellenlängenbereich keine spezifischen Absorptions- oder Reflexionsmuster auf. Aufgrund
seines engen Zusammenhanges mit dem Pflanzenchlorophyll (jedes Chlorophyllmolekül
enthält vier Stickstoffatome) wird sein Gehalt über die Menge des Chlorophylls abgeleitet.
Der erste Teil der Auswertungen beschäftigte sich deshalb mit dem Zusammenhang des
Gehaltes an Chlorophyll und Stickstoff in den Blättern. Dabei konnte bei der gemeinsamen
Analyse der drei Landnutzungsarten kein signifikanter Zusammenhang zwischen dUntersuchung konnte ein signifikant hoher Zusammenhang (r²≥0.67) zwischen dem
Stickstoff und Chlorophyll gefunden werden, wenn beide Parameter in Gehalten pro Fläche
vorliegen. Dabei korreliert insbesondere Chlorophyll a stark mit dem Stickstoffgehalt bei
den untersuchten Mais-, Weizen- und Grünlandpflanzen (r²≥0.8). Dagegen konnten bei
allen drei Landnutzungstypen keine signifikanten Beziehungen zwischen dem Chlorophyll-
und Stickstoffgehalt pro Masse nachgewiesen werden. Im Fall von Weizen verbesserten
sich die Ergebnisse nach der Trennung in die unterschiedlichen Sorten (r²≥0.67). Eine
Unterscheidung der Wachstumsphasen ergab ebenfalls eine Verbesserung der Ergebnisse,
wenn die Zeiten vor und nach der Blüte getrennt untersucht wurden (r²≥0.67).
Die untersuchten Maissorten sind dagegen durch auffällige Schwankungen im
Chlorophyllgehalt pro Masse geprägt. Diese Schwankungen werden von den aktuell
herrschenden Temperaturen im Untersuchungsgebiet beeinflusst. Der Mais als
ursprünglich tropische Pflanze stellt bei Temperaturen unter 15° das Wachstum ein und
reduziert seinen Stoffwechsel erheblich, was Auswirkungen auf den Gehalt an aktivem
Chlorophyll in den Pflanzen hat. Bei steigenden Temperaturen erholt sich der Stoffwechsel
und die Pflanzen beginnen wieder zu wachsen. Diese Erkältungssymptome ebenso wie die
Erholungszeiten sind bei den verschiedenen Maissorten unterschiedlich ausgeprägt. Diese
Temperaturabhängigkeit führt im Untersuchungsgebiet, in dem während der
Sommermonate des öfteren Temperaturen unter 15°C erreicht werden, zu Variationen im
Chlorophyllgehalt pro Masse, welche die Beziehung zum Stickstoff vermindern.
Bei der Analyse der Graslandflächen ergab sich, außer bei den oben bereits erwähnten
Gehalten pro Fläche, kein signifikanter Zusammenhang zwischen Chlorophyll und
Stickstoff.
Die Analyse dieser Resultate führen zu dem Schluss, dass die Stickstoff- und
Chlorophyllgehalte pro Masse der untersuchten Landnutzungsarten ab einem bestimmten
Level, dem Kompensationspunkt, entkoppelt sind. Dieser Kompensationspunkt wird dann
erreicht, wenn das in der Luft enthaltene CO2 limitierend auf die Photosyntheserate wirkt.
Wird dieses Limit überschritten, hat ein weiterer Aufbau von Chlorophyllmolekülen keine
Erhöhung der Photosyntheserate der Pflanze zur Folge. Eventuell vorhandener
pflanzenverfügbarer Stickstoff wird somit nicht mehr für den Einbau in Chlorophylle
verwendet, sondern vermehrt für die Synthese von Speicherproteinen genutzt.
Ein weiterer Schwerpunkt dieser A
Reflectance measurements (ASD LabSpec5000) of different surface types from Arctic sea ice acquired during POLARSTERN cruise PS106
No full textASD measurements are in units of irradiance reflectance. Every spectrum has an individual timestamp. Positions of each spectrum can be localized by joining the GPS data with the spectral data on the datetime of the measurement
Reflectance measurements (Ocean Optics STS-VIS) of bare ice and melt ponds on Arctic sea ice acquired during POLARSTERN cruise PS106/1
No full textAssessing the integrated water resources development potential of Wadi systems in Iran and their vulnerability to climate change
No full textSimilar to other Middle Eastern countries, Iran is experiencing a serious water crisis. Water resources become increasingly stressed in the Wadi regions of central and eastern Iran. Assessing water resources there is thus essential due to growing water demand and possible effects of future climate change.
Due to the lack of readily available surface water resources, different water use systems (WUSs) exist that provide water mainly for drinking, irrigation and further domestic use. In addition, many soil and water conservation measures (SWCMs) have been established to slow down the velocity of water and to increase infiltration and percolation rates. These alter hydrological components in Wadi regions that need to be considered.
Such characteristics particularly apply to the Wadi basin Halilrood in central Iran. Halilrood River is the largest river in terms of discharge in the Kerman Province and the major water provider for the downstream Jazmorian wetland. The Soil and Water Assessment Tool (SWAT) is employed to model the hydrological processes of the Wadi. WUSs and SWCMs are implemented into the hydrological model to simulate streamflow and major hydrological components under current and future climate change conditions. Moreover, groundwater sustainability and possible alterations in the ecological flow regime are evaluated by taking both climate change and population growth into account.
Results of the SWAT model simulation show that the hydrological processes of the Wadi system are better represented when WUSs and SWCMs are implemented. The improvement in model performance varies for different segments of the hydrograph. Peak and mean flows are simulated more accurately due to the improved depiction of infiltration rates and the slower release of water to the channels. The investigation of hydrological components reveals that the contribution of surface runoff and groundwater flows to the streams decrease in all sub-basins with WUSs. On the contrary, a higher contribution of groundwater to the streams is shown in most sub-basins with SWCMs. In sub-basins with both WUSs and SWCMs, groundwater contribution increases or does not show any change.
To assess the impact of climate change on the water resources in the near and far future (2030-2059 and 2070-2099) in comparison to the baseline period (1979-2009), the projections from 11 climate models and two bias correction methods (LS: linear scaling and DM: distribution mapping) for two Representative Concentration Pathways (RCP4.5 and RCP8.5) are used as input data for the calibrated hydrologic model. The results indicate a slight increase of streamflow in winter season for both RCPs and both bias correction methods, due to higher precipitation intensity. Besides that, a shift is simulated in the timing of the seasonal peak-flow. This is due to increases in temperature and changes in the precipitation pattern. The Halilrood Basin is expected to be vulnerable to climate change as different segments of the flow duration curve (FDC) show increasing variability that can also be interpreted as an alteration of the future flood and drought extremes. A decrease for very high and high flows is projected under both RCPs. Climate change is causing a slight increase in evaporation and less available water for infiltration and percolation, which eventually leads to zero contribution of groundwater to the main channel.
The impacts of climate change and growing water demand on the sustainability of groundwater use and the hydrologic regime of the Wadi are analyzed by linking the SWAT model results to the Indicators of Hydrologic Alteration (IHA) and the Range of Variability Approach (RVA). An unsustainable water resources situation (groundwater recharge is equal or greater than groundwater Demand) is expected in the future for the vast majority of sub-basins with WUSs. Due to the imbalance between the groundwater recharge under climate change and estimated groundwater demand in the future, a decline of groundwater levels is anticipated for the entire Halilrood Basin. This is not only resulting in unsustainable groundwater use, but also changes the hydrologic regime and poses a significant threat to downstream ecosystems.
The presented modeling framework is a useful approach, providing beneficial information on the water resources of Iranian Wadi systems and their vulnerability to climate change and population growth. The results of this research can contribute to long-term planning there, which is required for a sustainable water resources management under changing future conditions
Towards an improved understanding of hydrological alteration under global change
No full textThis dissertation proposes a comprehensive approach to explain the transitions in discharge regime in a more practical way using Indicators of Hydrological Alteration (IHA) and to disentangle the effects of individual factors on the detected changes in hydrological alteration. To identify the role of each environmental factor in the transition from local to global scales, the method uses discharge time series, both historical observations and projected data, as target variables. This allows a proper assessment from multiple case studies and at different scales. The method is first applied to an anthropogenically influenced river basin and then transferred to simulated runoff based on climate input at the multi-basin scale under climate factors until the end of the 21st century. Finally, it was used to detect the transitions in runoff regimes globally in the period 1960-2010. More than ten environmental variables, including climatic factors and anthropogenic factors, categorized by nine climate zones, are used as input to investigate systematic changes in the historical river regime using machine learning. The main findings of the thesis are that abrupt changes in the discharge regime are clearly evident in all case studies, and that these coincide visibly with human intervention (diversion dam) at the local scale. On a global scale, two-thirds of catchments worldwide experienced significant changes in discharge between the 1980s and 1990s. The top, highest, and lowest ranking variables that contributed to the change in flow regime have been tentatively identified. Overall, an improved understanding of the influence of environmental factors on hydrological change has been demonstrated. This highlights the contribution of individual environmental factors to global runoff regimes and can be used to provide a good guidance for further strategies applied to the river basin management
A new land cover map for the Mekong: Southeast Asia’s largest transboundary river basin
No full textThe transboundary Mekong basin, including territorial parts of China, Myanmar, Laos, Thailand, Cambodia, and Vietnam, is endowed with a rich natural resource base. The rapid socio-economic development of the region, however, substantially increases pressure on its natural resources that are increasingly subject of over-exploitation and environmental degradation. Some of the main environmental problems facing the region are common or transboundary issues that only can be addressed by transboundary approaches based on consistent and regional comparable information on the state of the environment at basin scale. In this context, a regional specific land cover map, the MEKONG LC2010 product, was produced for the entire Mekong Basin, utilising information from the MODIS sensor aboard the platforms Aqua and Terra
130 - Natascha Heise
No full textLearning and studying human anatomy is often associated with using rote knowledge. Novice students often memorize terms and structures in the laboratory with little reasoning skills. In attempt to promote application, integration, and critical thinking skills we introduced case based study into the human anatomy course at CSU. Early implementation suggested little change in student’s ability to solve novel problems using simple recall in attempt to answer case study questions. Here, we describe a novel approach using a 5-step method to promote critical thinking. Results suggest students application and integration during the case studies correlated with overall class performance
- …
