MODELLING SENSIBLE HEAT FLUX IN MOUNTAINOUS AREAS WITH HIGH RESOLUTION TERRAIN
PARAMETERS DERIVED FROM LANDSAT-TM DATA
Dipl. Geogr./Hydol. Jürgen Storl
President GEOTEC S.R.L.
Av. 20 de Octubre 2252 - La Paz - Bolivia
Fax: (591) (2) 37 49 97 - E-mail: geo@geo.bo
Commission VII, Working Group 5
KEY WORDS:
ABSTRACT
Sensible heat flux, Remote sensing, Modelling, Energy budget, Soil moisture, Evapotranspiration
This article presents a method to model sensible heat flux on micro scale over mountainous terrain and shows how the
model parameters can be derived at high resolution (30m) from Landsat-TM data, a digital terrain model and point
measurements of atmospheric parameters.
Thermal information of Landsat channel 6 is transformed to a resolution of 30m, applying a multiple linear regression
model that contains soil moisture information.
The modelling of sensible heat flux is performed using a slope wind model developed by Brehm (Brehm, 1986) and
applied with NOAA AVHRR data by Mannstein (Mannstein, 1991) over the Alpes.
The modelling of sensible heat flux is placed in the context of an inventory of all energy budget terms.
1. INTRODUCTION
The local dynamics of heat interchange are subject to
investigation in order to increase our understanding of
micrometeorological processes.
Calculating senible heat flux on micro scale makes it
possible to predict microclimatic changes due to changes
in vegetation cover (Parlow, 1988, 1990).
Moreover, sensible heat flux is a highly usefull term to be
calculated in order to derive actual evapotranspiration,
the most difficult term of the energy budget to be
modeled directly, due to its dependance on physiologic
control by plants.
Understanding evapotranspiration, in turn, leads to an
understanding of the water cycle for hydrologic and
agricultural purposes.
The modelling of sensible heat flux with remotely sensed
data is subject to many investigations, and a
considerable number of methods have been developed
for flat and uniform terrain, especially for certain crop
types.
Few investigators have undertaken the task of modelling
sensible heat flux from remotely sensed data over
mountainous and highly inhomogeneous terrain, as it is
presented in this study.
2. CONTEXT
The author developed a method applied by Mannstein
(Mannstein, 1991) for modelling sensible heat flux over
mountainous terrain. All model parameters were
procesed at a resolution that allows the calculation of
sensible heat flux on micro scale. The availability of a
great amount of datasets for the study area made it
possible to place the sensible heat flux modelling into the
context of an energy budget integration. Therefore, a
valuable instrument for verification was at hand.
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3. DATA
The data used in the present study consisted of a
satellite scene Landsat-TM, aquired on july 20, 1986 at
9h20 over the study area in northern scandinavia. All
channels were radiation corrected using the short wave
insulation model SWIM (Parlow, 1988, 1990, 1992
Parlow/Scherer 1991) and a detailed land use
classification derived by Parlow (Parlow, 1988) from
radiation corrected data was available.
Furthermore, the author could dispose of a PAR-albedo
image (Albedo for Photosynthetically Active Radiation,
Parlow, 1988, 1990) an image of solar irradiation
calculated with the program SWIM (Short Wave
Insulation Model, University of Basel) and calibrated by
Parlow and an image of longwave atmospheric counter
radiation (Parlow, 1988).
For each land use class, detailed radiometric
measurements of integral albedo had been performed by
Parlow (Parlow, 1988, 1990, 1991) and were available to
the author.
Thermal channel 6 of Landsat-TM had been calibrated
by Parlow to radiance surface temperatures over the sea
surface of lake Abisko, using a calibration formula
suggested by Schott and Volchok (Schott/Volchok,
1985). The atmospheric influence was eliminated using
an improved version of the WINDOW model of J. Price,
NASA (WINDHA, Price, 1987 / ATMKOR, Scherer,
1987).
At the day of satellite overpass, all meteorological
parameters of Abisko Station, inside the study area, were
available, together with a collection of meteorological
data from several years for the same station. A profile of
air temperature, air- and vapour pressure had been taken
by a radio sonde at Kallax/Lulea at the day of satellite
overpass at 12h00 local time.
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B7. Vienna 1996
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