Evaluation of modis products over four European ecological study sites [Elektronische Ressource] / presented by Nguyen Quoc Dinh

Huong Ngo

Sujets

• Biologie

Informations

• Publié par: universitat_bayreuth
• Publié le: 01 janvier 2008
• Nombre de lectures: 16
• Langue: English
• Poids de l'ouvrage: 7 Mo

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EVALUATION OF MODIS PRODUCTS
OVER FOUR EUROPEAN ECOLOGICAL STUDY SITES



A dissertation submitted to the
FACULTY OF BIOLOGY, CHEMISTRY AND GEOSCIENCES
UNIVERSITY OF BAYREUTH, GERMANY

to obtain the academic degree of
DR. RER. NAT.


presented by
NGUYEN QUOC DINH
M. Sc.
born June 16, 1970
in Namha, Vietnam



Bayreuth, December 2008

EVALUATION OF MODIS PRODUCTS
OVER FOUR EUROPEAN ECOLOGICAL STUDY SITES





By
Nguyen Quoc Dinh
Departments of Micrometeorology
And Plant Ecology
University of Bayreuth
Germany





Supervisors:
Prof. Dr. Thomas Foken
Prof. Dr. John Tenhunen


















Vollständiger Abdruck der von der Fakultät für Biologie, Chemie und Geowissenschaften der
Universität Bayreuth genehmigten Dissertation zur Erlangung des akademischen Grades
eines Doktors der Naturwissenschaften (Dr. rer. nat.).



Promotionsgesuch eingereicht am: 16. Dezember 2008
Wissenschaftliches Kolloquium am: 16. April 2009



Prüfungsausschuss:

Prof. Dr. Thomas Foken (Erstgutachter)
Prof. Dr. John Tenhunen (Zweitgutachter)

Prof. Dr. Michael Hauhs (Vorsitzender)
Prof. Dr. Bernd Huwe
PD. Dr. Werner Borken

Dekan: Prof. Dr. Axel Müller








Die vorliegende Arbeit wurde in der Zeit von Oktober 2001 bis Dezember 2008 an der
Universität Bayreuth am Lehrstuhl für Mikrometeorologie und Pflanzenökologie, unter
Betreuung von Prof. Dr. Thomas Foken und Prof. Dr. John Tenhunen angefertigt.

Verfügbar als PDF unter/ available as PDF at: http:/opus.ub.uni-bayreuth.de








To four women of my life:
Mom, Huong, Minh Hanh, and Minh Anh
Summary
SUMMARY
Global vegetation is a key component of the climate system due to its key role
in geosphere-biosphere-atmosphere interactions. Understanding these processes is
of important for predicting future climate and the future state of terrestrial
ecosystems. Land surface properties such as the land cover type and leaf area
index (LAI) are used as essential inputs in many hydrological, ecological, and
climate models. They are key parameters that describe the functioning of vegetation
and are required for modeling vegetation productivity, land surface climatology,
global carbon budgets and agricultural outputs as influenced by resource
management. Successful modeling of these processes to quantitatively and
accurately characterize global dynamics requires definition of these parameters
periodically and globally with high accuracy. For this purpose the MODIS-based land
surface products were designed and are now regularly available worldwide.
Nevertheless, analyses based on MODIS inputs of land cover and LAI must be
tested with respect to their reliability, in order that we can trust and use the outputs
from simulation models quantifying water and carbon balances at large scale. The
purpose of the research reported here is to determine the reliability of the MODIS
spectral reflectance, land cover and LAI products for European landscapes which
are highly fragmented and not necessarily homogeneous at the 1 km scale
characteristic of MODIS products. A stepwise analysis has been carried out for
reflectance, land cover and LAI products, comparing results from ground truth data
and from high resolution remote sensing images (Landsat) to the coarser scale
MODIS information. In this way, the influence of landscape fragmentation on the
MODIS products should be clear and advice can be given about how they should be
used in land surface modelling efforts.
Four European locations were chosen for study; landscapes dominated by
deciduous forest at Hesse, France; by coniferous forest at Tharandt, Germany, and
by forest and grassland in mountainous terrain in the Berchtesgaden National Park,
Germany and in Stubai Valley, Austria. All of these landscapes, however, have a
mixture of land use. In order to compare measurements at intensive study plots with
MODIS (1 km resolution), it was necessary to build a bridge via remote sensing data
derived with Landsat TM (30 m resolution). It was demonstrated that for all study
sites, the registration accuracy of Landsat TM images did not deviate by more than
half of one pixel, and that the root mean square of error (RMSE) was less than 0.3
pixel when utilizing at least 40 ground control points and nearest-neighbor
I Summary
resampling technique. Comparing Landsat images with aerial photography clearly
demonstrated that specific study sites on the ground could be identified and that the
measured characteristics could be associated with Landsat pixel properties.
The evaluation results showed that the MODIS reflectance product is
reasonably accurate (less than 10 % absolute error). Certainly it is appropriate to
utilize reflectance data from the two types of satellite images and to use these
information in comparative examinations of land cover mapping and leaf area index
estimation. The land cover comparison demonstrates that both the scale applied in
classifications and the number and type of land use categories that are permitted
lead to important shifts in the characterization of land cover when moving from 30 m
to 1 km resolution of MODIS. Fragmentation in European landscapes is a
fundamental problem encountered in the use of MODIS products. A true
representation of the land surface cannot be obtained from the current MODIS land
cover classifications at 1 km scale. The use of these descriptors in models
describing land surface properties may potentially lead to large errors. Thus,
exchange between the land surface and the atmosphere of water and CO as 2
estimated by models using MODIS inputs will have a high level of uncertainty, and
the results must be considered with caution. The problems in classification that are
encountered lead to further difficulties in land surface characterization, since the
retrieval of LAI uses land cover as an input variable. At the peak of vegetation
development, MODIS LAI appears to strongly underestimate values of the Landsat
based maps. During winter, the comparison is even worse, but is not consistent from
grassland to deciduous forest and coniferous forest. The results cast doubt on the
usefulness of MODIS LAI products as input to continental scale simulation models
for carbon and water balances, at least in Europe where land cover is highly
modified and fragmented due to centuries of human use and management. Use of
the MODIS products in Europe requires that new techniques be considered to
search for compatibility in averaging and aggregating information on land cover and
reflectance that is used to estimate LAI for large areas.

Keywords: Remote sensing, vegetation, MODIS, Landsat, LAI, Land cover,
reflectance, evaluation
II Zusammenfassung
ZUSAMMENFASSUNG
Aufgrund der komplexen Interaktionen zwischen Geosphäre, Biosphäre und
Atmosphäre spielt die Vegetation auf der Erde eine der Schlüsselrollen des globalen
Klimas. Das Verständnis dieser Interaktionen und Prozesse ist von grundlegender
Bedeutung zur Vorhersage zukünftiger Klima- und Vegetationsszenarios.
Eigenschaften der Kontinentoberflächen, wie Vegetationsbedeckung und
Blattflächenindex (LAI) fließen ein als essentielle Vorgaben für die Berechnung
hydrologischer, ökologischer und klimatischer Modelle. Es sind dies
Schlüsselparameter zur Erklärung der „Funktion“ der Pflanzendecke und sie werden
daher benötigt für die Modellierung der Biomasse-Produktion, des Klimas der
Landoberflächen, der globalen Kohlenstoff-Bilanz und der Landwirtschafts-Erträge in
Abhängigkeit zum anthropogenen Ressourcen-Management. Ihre realistische
Modellierung für eine exakte quantitative Charakterisierung globaler Dynamiken
verlangt die periodische und globale Definition dieser Prozesse in höchster
Genauigkeit. Hierfür wurden MODIS-basierte Land-Oberflächen-Modelle entwickelt,
welche inzwischen weltweit verfügbar sind.
Zur Überprüfung der Vorhersagegenauigkeit der MODIS-Modellierungen sind
dennoch Tests hinsichtlich Land-Vegetationsbedeckung und LAI erforderlich, um die
Simulationen hinsichtlich der Quantifizierung der großmaßstäblichen Wasser- und
Kohlenstoff-Bilanz überprüfen zu können. Die vorliegende Arbeit befasst sich mit der
Bestimmung der Zuverlässigkeit von MODIS-Produkten, die die spektrale
Reflexions-Eigenschaften der Land-Bedeckung, der Landnutzung und des LAIs in
typischen europäischen Landschaften räumlich charakterisieren sollen, welche aber
hinsichtlich des viel zu großen 1 km-Rasters von MODIS als äußerst fragwürdig zu
werten sind. Durchgeführt wurde deshalb eine stufenweise Analyse für die Licht-
Reflexion, Land