Mr. Wim Timmermans Profile

Wim Timmermans

at ITC

SPIE Involvement:

Author

Publications (2)

This will count as one of your downloads.

You will have access to both the presentation and article (if available).

DOWNLOAD NOW

This content is available for download via your institution's subscription. To access this item, please sign in to your personal account.

Email or Username Forgot your username?

Password Forgot your password?

Show

Keep me signed in

No SPIE account? Create an account

Proceedings Article | 24 February 2004 Paper

Determination of water and heat fluxes with MODIS imagery: Maun, Botswana

Wim Timmermans, Ambro Gieske, William Kustas, Piotr Wolski, Almut Arneth, Gabriel Parodi

Proceedings Volume 5232, (2004) https://doi.org/10.1117/12.511117

KEYWORDS: Heat flux, Vegetation, MODIS, Visible radiation, Near infrared, Shortwaves, Data modeling, Remote sensing, Atmospheric modeling, Solar radiation models

Read Abstract +

Estimation of regional evapotranspiration is of major importance in hydrological modeling, where the partitioning of available energy into sensible and latent heat fluxes is crucial. Point-based measurements are routinely obtained with micrometeorological methods through a combination of radiometers and eddy-covariance instruments. Notwithstanding closure problems, they are considered to yield reliable flux point values. However, when dealing with heterogeneous semi-arid terrain, these point estimates are not representative for regional values. In this paper the results are presented of an analysis where MODIS images are used for the mapping of energy and water balances of a heterogeneous land surface in a savannah environment on the southern fringe of the Okavango Delta (Maun, Botswana). Despite its semi-arid character, fresh floodwaters arrive through the Delta seasonally and therefore part of the area’s vegetation is always transpiring at a potential rate. The model we implemented is governed by remotely sensed values of surface temperature, reflection and vegetation density. The availability of MODIS data provided an opportunity to test the new algorithm by determining the energy balance components on a regional scale for a heterogeneous area and then comparing the results with energy flux measurements using a meteorological flux tower situated in a woodland savannah environment. The results indicate good estimates of net radiation, soil and turbulent fluxes. However, if energy closure problems are neglected, latent heat estimates show significant deviations.

Proceedings Article | 24 February 2004 Paper

Temperature-emissivity separation with ASTER and LANDSAT 7 validation on the fringe of the Okavango Delta, Botswana

Ambro Gieske, Michael Wubett, Wim Timmermans, Gabriel Parodi, Piotr Wolski, Almut Arneth

Proceedings Volume 5232, (2004) https://doi.org/10.1117/12.511043

KEYWORDS: Landsat, Satellites, Atmospheric corrections, Algorithm development, Thermography, Image processing, Infrared imaging, Infrared radiation, Sensors, Earth observing sensors

Read Abstract +

Land surface temperatures are important in global change studies, in estimating radiation budget, heat balance studies and as control for climate models. A new algorithm for estimating land surface temperature and emissivity spectra for multi spectral thermal infrared ranging from 8 to 12mm images has been developed recently (Schmugge et al., 2002) 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 instrument. In this study, the method developed by Ogawa et al. (2002) was adopted to estimate the broadband emissivity from the narrow band emissivities of the five TIR channels of ASTER instrument in an area on the southern fringe of the Okavango Delta (Botswana). MODTRAN 4 was used to determine the necessary atmospheric corrections while software was developed to facilitate MODTRAN pre- and post-processing. 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 the surface temperature depends rather sensitively on atmospheric transmissivity. No relation was found between broad-band emissivity and NDVI, contrary, for example, to earlier findings in Botswana by Owe and Van de Griend (1993). Using the TES method it becomes possible to obtain more reliable solutions to the energy balance and evapotranspiration problem, especially in semi-arid areas.

My Library

You currently do not have any folders to save your paper to! Create a new folder below.

Folder Name

Folder Description

View contact details

UPDATE YOUR PROFILE

Is this your profile? Update it now.

Sign into your SPIE.org account

Don’t have a profile and want one?

Create an account on SPIE.org

Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks. You are receiving this notice because your organization may not have SPIE eBooks access.*

*Shibboleth/Open Athens users─please sign in to access your institution's subscriptions.

To obtain this item, you may purchase the complete book in print or electronic format on SPIE.org.

ORGANIZATIONAL
Sign in with credentials provided by your organization.

Organizational Username

Organizational Password

Show/Hide Password

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available

Members:

Non-members: ADD TO CART

Keywords/Phrases

Search In:

Publication Years