estimation of absolute surface temperature by satellite remote sensing.

132 Pages·2003·5.19 MB·English

ESTIMATON OF ABSOLUTE SURFACE TEMPERATURE BY SATELLITE REMOTE SENSING.

ESTIMATION OF ABSOLUTE
SURFACE TEMPERATURE
BY SATELLITE
REMOTE SENSING.

Michael Tsehaye Wubet
March 2003
INTERNATIONAL INSTITUTE FOR GEOINFORMATION SCIENCE AND EARTH OBSERVATION. I
ESTIMATON OF ABSOLUTE SURFACE TEMPERATURE BY SATELLITE REMOTE SENSING.

ESTIMATION OF ABSOLUTE SURFACE TEMPERATURE
BY SATELLITE REMOTE SENSING.

By

Michael Tsehaye Wubet

Thesis submitted to the International Institute for Geo-information Science and Earth
Observation in partial fulfillment of the requirements for the degree of Master of Science in
Water Resources and Environmental Management Specializing in Watershed Management,
Conservation and River Basin Planning.

Degree Assessment Board

Prof. Dr. W.G.M. Bastiaanssen (Chairman)
ITC, Enschede.
Dr. Bob Su (External Examiner)
Netherlands Alterra-Wageningen University.
Dr. A.S.M. Gieske (First Supervisor)
ITC, Enschede.
Ir. Wim Timmermans (Second supervisor)
ITC, Enschede.
Ir. G.N. Parodi (Member)
ITC, Enschede.

INTERNATIONAL INSTITUTE FOR GEO-INFORMATION SCIENCE AND EARTH OBSERVATION
ENSCHEDE, THE NETHERLANDS
INTERNATIONAL INSTITUTE FOR GEOINFORMATION SCIENCE AND EARTH OBSERVATION. II
ESTIMATON OF ABSOLUTE SURFACE TEMPERATURE BY SATELLITE REMOTE SENSING.
Disclaimer

This document describes work undertaken as part of a programme of study at the
International Institute for Geo-information Science and Earth Observation. All views
and opinions expressed therein remain the sole responsibility of the author, and do not
necessarily represent those of the institute.

INTERNATIONAL INSTITUTE FOR GEOINFORMATION SCIENCE AND EARTH OBSERVATION. III
ESTIMATON OF ABSOLUTE SURFACE TEMPERATURE BY SATELLITE REMOTE SENSING.
This thesis is dedicated to my wife Etsegenet and to all my families.

INTERNATIONAL INSTITUTE FOR GEOINFORMATION SCIENCE AND EARTH OBSERVATION. IV
ESTIMATON OF ABSOLUTE SURFACE TEMPERATURE BY SATELLITE REMOTE SENSING.
Acknowledgement
I would like to express my Sincere and heartfelt gratitude to the Netherlands Government
through the Netherlands Fellowship Program (NFP) for granting me the opportunity to
pursue this course of study without which I would not have realized my dream to further my
studies. I am grateful to my former employer, Commission for Sustainable Agriculture and
environmental Rehabilitation in Tigray (COSAERT) who through the Vice-commissioner Mr.
Leul Kashay complemented my efforts by supporting me to fulfil my wish.

My thanks go to all the staff of WREM for the support and guidance throughout the modules
and thesis preparation. Special thanks goes to my Supervisor Dr. A.S.M Gieske, for the
guidance and critical comments that made this research a success. My gratitude also goes to
my second supervisor, Ir. Wim Timmermans, for all his effort to furnish me all the necessary
data. I am particularly grateful for his help during the fieldwork in Okavango delta,
Botswana. I would also like to thank the University of Botswana Harry Oppenheimer
Okavango Research center (HOORC) and Max Planck Institute in Jena, Germany for
providing me their meteorological data. I am also grateful to my classmates in WREM 2001
with whom we shared jokes. Many thanks to Kenta Ogawa and Mekonnen G/Michael from
USA who gave me their unreserved material and advice.

My heartfelt gratitude goes to my wife Etsegenet G/hanna for your patience, support and
encouragement and, those special words especially through the hardest times gave me the
courage to continue. Special thanks go to all my dear parents who have been my mentors
always supportive and urging me on. Last but not least I would like to thank all my friends
specially Tsige G/wahide, the list is endless, for the e-mails and calls that always cheered me
up.
INTERNATIONAL INSTITUTE FOR GEOINFORMATION SCIENCE AND EARTH OBSERVATION. V
ESTIMATON OF ABSOLUTE SURFACE TEMPERATURE BY SATELLITE REMOTE SENSING.
Abstract
Land surface temperatures are important in global change studies, in estimating radiation budgets in
heat balance studies and as a control for climate models. Land surface temperature is strongly
influenced by the ability of the surface to emit radiation, i.e. surface emissivity. Therefore, knowledge
of the surface emissivity is crucial for estimating the radiation balance at the earth surface. A new
algorithm for estimating land surface temperature and emissivity spectra for multi spectral thermal
infrared ranging from 8 to 12 mm images has been developed recently by [1] and [2] for use with data
from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on the
TERRA platform. Similar methods are also used with the MODIS sensor on the same platform.

The temperature emissivity separation (TES) algorithm is based on an empirical relationship between
spectral contrast and minimum emissivity, determined from laboratory and field emissivity spectra. It
is used to equalize the number of unknown parameters and the number of measurements so that the set
of Planck’s equations for the measured thermal radiances can be inverted. Surface temperatures are
independent of wavelength and can be recovered from even a single band of radiance data provided
atmospheric characteristics can be specified and surface emissivity is known. However, emissivity of
land surfaces is not known a priori (except for water bodies) but should be estimated along with the
temperature. Moreover, emissivity values vary with wavelength.

In this study, the method developed by [3] was adopted to estimate the broadband emissivity from the
narrow band emissivities of the five TIR channels of ASTER instrument in an area close to Maun
(Botswana). MODTRAN 4 was used to calculate the necessary atmospheric corrections (for standard
atmospheres). All programming was done using the ILWIS script language. The results were
compared with field data, with a LANDSAT 7 image of the same day, and finally also with reported
ASTER surface temperature and emissivities for the same image (High level ASTER product).

Results indicate that information on atmospheric conditions is crucial. The surface temperature is
rather sensitive to atmospheric transmissivity. No relation was found between broadband emissivity
and NDVI, contrary, to earlier findings by [4]. Using the TES method it becomes possible to obtain
more reliable solutions to the energy balance and evapotranspiration problem, especially in semi-arid
areas.
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ESTIMATON OF ABSOLUTE SURFACE TEMPERATURE BY SATELLITE REMOTE SENSING.

TABLE OF CONTENTS
ACKNOWLEDGEMENT......................................................................................................................v
ABSTRACT...........................................................................................................................................vi
TABLE OF CONTENTS......................................................................................................................vii
LIST OF TABLES:................................................................................................................................ix
LIST OF FIGURES:...............................................................................................................................ix
LIST OF PLATES:.................................................................................................................................xi
LIST OF PLATES:.................................................................................................................................xi
LIST OF APPENDIXES:.......................................................................................................................xi
1 General Introduction.......................................................................................................................1
1.1. Introduction/back ground/setting:..........................................................................................1
1.2. Research objectives:..............................................................................................................2
1.3. Research questions:................................................................................................................2
1.4. Methods and Materials:.........................................................................................................2
1.4.2.1 Preliminary preparation.................................................................................................2
1.4.2.2 Field work.....................................................................................................................3
1.4.2.3 Meteorological data.......................................................................................................3
1.4.2.4 Field data collected during the satellite overpass time..................................................3
1.4.2.5 Data processing and analysis.........................................................................................3
1.4.2.6 Materials and data used.................................................................................................4
1.5 Thesis outline.........................................................................................................................4
2 Theoretical Background................................................................................................................10
2.1 Literature Review of Thermal Infrared Theory...................................................................10
2.1.1 Introduction.....................................................................................................................10
2.1.2 Introduction.....................................................................................................................11
2.1.2.1 The Planck’s law.........................................................................................................12
2.1.2.2 Wien Law....................................................................................................................12
2.1.2.3 Stefan Boltzman law...................................................................................................13
2.1.2.4 Energy emitted by grey and real bodies......................................................................13
2.1.3. Literature review on Temperature emissivity separation algorithm (TES).....................14
3 Description of Study area..............................................................................................................15
3.1 Location...............................................................................................................................15
3.2 Climate.................................................................................................................................17
3.2.1 Rainfall............................................................................................................................17
3.2.2 Temperature.....................................................................................................................18
3.2.3 Relative Humidity...........................................................................................................19
3.2.4 Wind speed......................................................................................................................20
3.2.5 Net radiation....................................................................................................................20
3.2.6 Parameters Measured During Field Work.......................................................................23
3.3 Vegetation............................................................................................................................25
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ESTIMATON OF ABSOLUTE SURFACE TEMPERATURE BY SATELLITE REMOTE SENSING.
3.3.1.1 Introduction.................................................................................................................25
3.3.1.2 Previous work (adapted and extracted from WRC report)..........................................25
3.3.2 Vegetation........................................................................................................................29
3.3.2.1 Introduction.................................................................................................................29
3.3.2.2 False Colour Composite (FCC)...................................................................................29
3.3.3 Land cover mapping using satellite imagery...................................................................31
3.3.3.1 Introduction.................................................................................................................31
3.3.3.2 Results and discussion.................................................................................................31
3.4 Soils.....................................................................................................................................33
4 Estimation of Surface Temperature and Emissivity using TES algorithm....................................35
4.1 Introduction..........................................................................................................................35
4.2 The ASTER Imaging System...............................................................................................36
4.3 Methods and Measurements................................................................................................37
4.4 Estimation of Broadband Emissivity...................................................................................40
4.4.1 Introduction.....................................................................................................................40
4.4.2. Method.............................................................................................................................40
5. Surface temperature and Emissivity estimation using Landsat 7..................................................42
5.1. Introduction..........................................................................................................................42
5.2. Conversion of DN values to Radiance.................................................................................42
5.3. Conversion of Radiance to Reflectance...............................................................................43
5.4. Normalized Difference Vegetation Index, NDVI................................................................45
5.5. Thermal infrared surface emissivity, e ...............................................................................45
o
5.6. Estimation of surface temperature, T ..................................................................................47
o
5.6.1. Computation of Brightness temperature from LANDSAT 7 ETM+ thermal band.........47
5.6.2. Algorithm for atmospheric correction of brightness temperature...................................48
5.6.3. Determination of atmospheric temperature, T ...............................................................51
at
5.6.4. Estimation of surface temperature...................................................................................52
6. RESULTS AND DISCUSSION:..................................................................................................53
6.1. Broad band emissivity.........................................................................................................53
6.2. Surface temperature estimation............................................................................................56
6.3. Cross validating ASTER and LANDSAT 7........................................................................58
6.4. Sensitivity analysis..............................................................................................................61
6.5. High level ASTER product..................................................................................................62
6.5.1. Surface Emissivity (AST_05)..........................................................................................62
6.5.2. Surface Kinetic Temperature (AST_08)..........................................................................63
7. Conclusions and Recommendation...............................................................................................65
7.1. Conclusion...........................................................................................................................65
7.2. Recommendation:................................................................................................................67
References:............................................................................................................................................68

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ESTIMATON OF ABSOLUTE SURFACE TEMPERATURE BY SATELLITE REMOTE SENSING.
LIST OF TABLES:

Table 1 General Natural Vegetation Cover of Maun (WRC, 2001.).....................................................26
Table 2 Major species found in vegetation associations in Maun.........................................................27
Table 3 Definitions of Various Okavango Ecosystems (After MLGLH, 1989)...................................28
Table 4 Description of Main Soils in Maun (From Soil Mapping and Advisory Services Project,
1990b)............................................................................................................................................33
Table 5 Spectral considerations of ASTER...........................................................................................36
Table 6 Calibrated Coefficients obtained using JHU/ASTER Library.................................................41
Table 7 Spectral Considerations of LANDSAT 7 ETM+.....................................................................42
Table 8 LANDSAT 7 ETM+ Spectral radiance range (Wm-2sr-1mm-1).................................................43
Table 9. Solar Spectral Irradiance.........................................................................................................44
Table 10 Emissivity and NDVI measurements for various natural surfaces.........................................46
Table 11 Thermal band calibration constants........................................................................................47
Table 12. Data used to estimate a6 and b6............................................................................................50
Table 13 Summary results estimated from ASTER and LANDSAT 7 for February 20, 2002.............58
Table 14 Comparison of ASTER and LANDSAT 7 derived surface temperature for different land
cover...............................................................................................................................................60
Table 15Comparison of ASTER and LANDSAT 7 derived broadband emissivity for different land
cover...............................................................................................................................................60
Table 16 Basic data used to develop TES algorithm in spreadsheet.....................................................61
Table 17 Summary of the sensitivity analysis of the parameters for changes in –10% of MODTRAN 4
out puts for Planck tower...............................................................................................................61

LIST OF FIGURES:
Figure 1 General approaches and Methodology flow chart....................................................................6
Figure 2 General approach and methodology used for developing TES algorithm using ILWIS script.7
Figure 3 (continued) General approach and methodology used for developing TES algorithm using
ILWIS script....................................................................................................................................8
Figure 4 General approach and methodology used for estimating surface temperature and emissivity
using LANDSAT 7..........................................................................................................................9
Figure 5 Comparison of TES and LANDSAT 7 derived surface temperature and emissivity................9
Figure 6 The electromagnetic spectrum................................................................................................10
Figure 7 Spectral exitance distributions for blackbodies at 6000, 4000, 2000, and 1000 K.................11
INTERNATIONAL INSTITUTE FOR GEOINFORMATION SCIENCE AND EARTH OBSERVATION. IX
ESTIMATON OF ABSOLUTE SURFACE TEMPERATURE BY SATELLITE REMOTE SENSING.
Figure 8 Location of the study area.......................................................................................................16
Figure 9 Mean monthly rainfall of the period 1925 to 2001.................................................................17
Figure 10 Annual mean rainfall of the study area for the period 1925 to 2001....................................18
Figure 11 Monthly temperature of the study area, from 1998 to 2001.................................................18
Figure 12 Air temperatures from the Planck tower dated on February 20, 2002..................................19
Figure 13 Relative humidity measured at 10 minutes interval dated on February 20, 2002.................19
Figure 14 Wind speed measured at 10 minutes interval dated on 20/02/2001......................................20
Figure 15 Radiation components from the Planck tower dated on 20/02/2001....................................21
Figure 16 surface temperatures measured by thermal Infrared thermometer dated on September 16,
2002...............................................................................................................................................23
Figure 17 Incoming and out going short wave radiations measured for bare soil-using Pyrnometer
dated on September 16, 2002........................................................................................................24
Figure 18 Incoming and out going short wave radiations measured for short bushes Pyrnometer dated
on September 16, 2002..................................................................................................................24
Figure 19 LANDSAT 7 FCC 742 of the study area dated on February 20, 2002 at 10:15 hours.........30
Figure 20 ASTER FCC 321 of the study area dated on February 20, 2002 at 10:45 hours..................30
Figure 21 Classified Images Showing the distributions of the Dominant land cover in Maun.............32
Figure 22 Feature space used for making the land cover units.............................................................32
Figure 23 Soil Map of the study area....................................................................................................34
Figure 24 ASTER spectral bands (extracted from: http://asterweb.jpl.nasa.gov/instrument/band.htm)37
Figure 25 Shows the different components used to extract Surface temperature.................................37
Figure 26 Plot of the mean emissivity versus the mean NDVI.............................................................46
Figure 27 Determination of a and B coefficients................................................................................51
6 6
Figure 28 Broadband emissivity map and histogram derived using ASTER sensor.............................53
Figure 29 Broadband emissivity map and histogram derived using LANDSAT 7 sensor....................54
Figure 30 Correlation result of broadband emissivity of LANDSAT 7 and ASTER for February 20,
2002...............................................................................................................................................54
Figure 31 Correlation result of ASTER broadband emissivity and NDVI for February 20, 2002........55
Figure 32_1 ASTER broadband emissivity correlation graph derived using Ogwa, K. et al., 2002 and
Van Griend Owe methods.............................................................................................................55
Figure 33 Correlation results of ASTER and LANDSAT 7 derived Surface temperature...................56
Figure 34 Surface temperature map of Maun derived from ASTER and LANDSAT 7.......................57
Figure 35 Histograms of Surface temperature for Maun derived from ASTER and LANDSAT 7......58
Figure 36 Map showing spatial variation of out going Long wave radiations derived from ASTER and
LANDSAT 7 [Wm-2].....................................................................................................................59
Figure 37. Broadband emissivity computed from the narrow band channels of AST_05 products for
February 20, 2002.........................................................................................................................62
Figure 38 AST_08 Surface temperature product for February 20, 2002...............................................63
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