84
H.-J. Bolle
respectively variability) to a degree that they are able to support intensive
irrigation,
b) the available water cannot be spent more efficiently (e.g. by application of
modern irrigation techniques and/or change to different species), and#
c)
the cultivation of species with roots reaching moist soil layer in some depth
does not receive continued economic support.
The intensive measuring phase ofEFEDA was a pilot experiment during which
only processes could be investigated with short characteristic time scales and under
dry conditions. But the occurrence of such dry conditions depends on long term
climate variability respectively climate change and the impact of dry spells in
alternation with wet events on the condition of the land-surfaces including its
vegetation inter alia is a function of the time constants of sub-surface hydrological
processes. These are much longer than could readily be studied within EFEDA. To
receive full return from the achieved insights into the investigated land-surface
processes it therefore is necessary to lead the developed methodology into an
operational mode that relies upon very few but well equipped ground stations (so
called "anchor stations") and to extend especially the hydrological studies over an
number of years and into hilly terrain.
One important task during the EFEDA pilot experiment was the re-calibration
of A VHRR satellite data and the validation of information derived from these data
(Koslowsky, 1997). The continuation of the evaluation of satellite data and some
scattered ground truth operations throughout the Mediterranean area (Castilla-La
Mancha, Tuscany, Messara Valley on Crete, and Israel) during the years 1994 -
1999 nevertheless allow to embed the measurements made 1991 and 1994 in Spain
into a larger space and time scale. Ten years of satellite data time series make it
possible to analyse the interannual variability of the Castilla-La Mancha area in the
context of changes all over the Iberian Peninsula. Moreover for few years carefully
calibrated A VHRR data are now available for the whole Mediterranean area which
enables first studies of synergisms throughout the basin.
The draw back of such regional to large scale EFEDA-type experiments so far
was that for each single parameter which enters the process studies the measuring
equipment had to be implemented or the relevant data had to be assessed by
labourious efforts from various offices. To embed such regional short-term
investigations into the larger scales of time and space variability a long term data
set of at least a reduced spatial coverage must be available. Fortunately in the case
of the Castilla-La Mancha experiment a long term hydrological data set was
available at the Uni versity Complutense in Madrid. Also the meteorological support
was excellent, weather maps and general meteorological data were made available
for the time of the experiment. But for comparison with the larger scale satellite data
so far no surface data backup exist. For the correction of the satellite data a study
was undertaken within the relevant EC projects to determine the water vapour field
over the Iberian peninsula based upon a ECMWF re-analysis. Such data must in the
future be available in nearly real time to correct the satellite data.
EFEDA-type experiments gained a lot from already existing data and served as
a vehicle to bring these data together, relate them to each other and to aggregate
H.-J. Bolle
respectively variability) to a degree that they are able to support intensive
irrigation,
b) the available water cannot be spent more efficiently (e.g. by application of
modern irrigation techniques and/or change to different species), and#
c)
the cultivation of species with roots reaching moist soil layer in some depth
does not receive continued economic support.
The intensive measuring phase ofEFEDA was a pilot experiment during which
only processes could be investigated with short characteristic time scales and under
dry conditions. But the occurrence of such dry conditions depends on long term
climate variability respectively climate change and the impact of dry spells in
alternation with wet events on the condition of the land-surfaces including its
vegetation inter alia is a function of the time constants of sub-surface hydrological
processes. These are much longer than could readily be studied within EFEDA. To
receive full return from the achieved insights into the investigated land-surface
processes it therefore is necessary to lead the developed methodology into an
operational mode that relies upon very few but well equipped ground stations (so
called "anchor stations") and to extend especially the hydrological studies over an
number of years and into hilly terrain.
One important task during the EFEDA pilot experiment was the re-calibration
of A VHRR satellite data and the validation of information derived from these data
(Koslowsky, 1997). The continuation of the evaluation of satellite data and some
scattered ground truth operations throughout the Mediterranean area (Castilla-La
Mancha, Tuscany, Messara Valley on Crete, and Israel) during the years 1994 -
1999 nevertheless allow to embed the measurements made 1991 and 1994 in Spain
into a larger space and time scale. Ten years of satellite data time series make it
possible to analyse the interannual variability of the Castilla-La Mancha area in the
context of changes all over the Iberian Peninsula. Moreover for few years carefully
calibrated A VHRR data are now available for the whole Mediterranean area which
enables first studies of synergisms throughout the basin.
The draw back of such regional to large scale EFEDA-type experiments so far
was that for each single parameter which enters the process studies the measuring
equipment had to be implemented or the relevant data had to be assessed by
labourious efforts from various offices. To embed such regional short-term
investigations into the larger scales of time and space variability a long term data
set of at least a reduced spatial coverage must be available. Fortunately in the case
of the Castilla-La Mancha experiment a long term hydrological data set was
available at the Uni versity Complutense in Madrid. Also the meteorological support
was excellent, weather maps and general meteorological data were made available
for the time of the experiment. But for comparison with the larger scale satellite data
so far no surface data backup exist. For the correction of the satellite data a study
was undertaken within the relevant EC projects to determine the water vapour field
over the Iberian peninsula based upon a ECMWF re-analysis. Such data must in the
future be available in nearly real time to correct the satellite data.
EFEDA-type experiments gained a lot from already existing data and served as
a vehicle to bring these data together, relate them to each other and to aggregate