ERS SCATTEROMETER DERIVED SOIL MOISTURE MAPS OF THREE CLIMATIC ZONES
Wolfgang Wagner
Institute for Photogrammetry and Remote Sensing, Vienna University of Technology
&
Space Applications Institute, EC Joint Research Centre, Ispra, Italy
KEY WORDS: Soil Moisture, Radar, Global Monitoring, Climate
ABSTRACT:
Soil moisture is still a poorly simulated component of General Circulation Models
(GCMs) .
performance of
Remotely sensed soil wetness information could be useful for improving the
In this paper derived from ERS |
Scatterometer imagery are discussed. The ERS Scatterometer is a radar operating at 5.3
these models. Soil moisture maps
GHz (C-band) and has a spatial resolution of about 50 km. Its three antennas illuminate
which allows to distinguish
of three
the surface from three different viewing directions
vegetation and soil moisture effects on the signal. Soil moisture maps
climatic zones are presented: Mediterranean climate (Iberian Peninsula), wet-dry
(Mali),
that the ERS Scatterometer based soil moisture maps reflect the different precipitation
tropical climate and moist-continental climate (Hungary). The analysis shows
patterns of these regions very well.
1. INTRODUCTION climate) derived from ERS
Scatterometer imagery are presented
Based on General Circulation Models and discussed qualitatively. To
(GCM) simulations it was suggested investigate if year to year
that for ‘a’ world’ made differences
warmer by
enhanced greenhouse gases summer soil
moisture could decrease over
midcontinent agricultural regions. To
determine if midcontinental drying is
a robust prediction soil moisture must
be properly simulated (Robock et al.,
1995). However, it appears that one of
GCM models
lies in their inability to correctly
the main limitations of
simulate the terrestrial hydrological
cycle (Lawford, 1992; Robock et al.,
1995). According to Dirnmeyer (1995)
the lack of widespread observations of
Soil moisture continues to hamper
efforts to verify and improve
simulations. For this purpose point
measurements would not fully meet the
requirements of land process modellers
because they need soil moisture
averaged over thousands of square
kilometres (Lawford, 1992). On this
scales only remote sensing can provide
the required information. In this
paper soil moisture maps of three
climatic zones (Mediterranean, wet-dry
tropical, and
moist continental
Intemational Archives of Photogrammetry and Remote Sensing. Vol. XXXII, Part 7, Budapest, 1998
in the ERS Scatterometer
derived soil moisture maps reflect the
qualitative
agricultural
physical reality a
with
Statistics is attempted.
comparison
2. METHODOLOGY
The ERS Scatterometer is a radar
operating at 5.3 GHz (C-band)
flown on board of the European Remote
Sensing Satellites ERS-1 and ERS-2
(Lecomte and Attema, 1992). Since the
launch of ERS-1 in 1991 it has been
providing continuous global coverage.
and is
It measures the backscattering
coefficient c? with a spatial
resolution of 50 km. Its three
sideways looking antennas (fore-, mid-
, and aft- beam antennas) scan a 500
km wide swath right to the satellite
track different
each
from viewing
three
independent measurements of Oo" are
obtained at two different incidence
angles and at three different azimuth
directions. For pixel
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