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Fourth Study Conference on BALTEX Scala Cinema Gudhjem

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- 31 -<br />

Determinati<strong>on</strong> and Comparis<strong>on</strong> of Evapotranspirati<strong>on</strong> with Remote<br />

Sensing and Numerical Modelling in the LITFASS Area<br />

A. Tittebrand , C. Heret , B. Ketzer and F.H. Berger<br />

Institute for Hydrology and Meteorology, University of Dresden (atibrand@forst.tu-dresden.de)<br />

1. Introducti<strong>on</strong><br />

This study is part of the network project EVA_GRIPS. The<br />

aim of our subproject is the determinati<strong>on</strong> and scaling up of<br />

biophysical land surface properties, radiant- and energy flux<br />

densities with modelling (LM) and remote sensing data<br />

analysis (NOAA-AVHRR, Landsat-7 ETM+) with different<br />

spatial resoluti<strong>on</strong>s.<br />

The area of interest is the LITFASS-area (20 x 20 km 2 ), a<br />

highly heterogeneous landscape around the meteorological<br />

observatory of the DWD in Lindenberg (50 km southeastern<br />

from Berlin).<br />

2. Methods<br />

To infer radiant and energy flux densities from a given<br />

landscape several methods are possible. First modelling<br />

efforts are used. The Lokal-Modell (LM) of the DWD is an<br />

n<strong>on</strong>-hydrostatic mesoscale model for Central and Western<br />

Europe. It c<strong>on</strong>tains 35 layers, 10 layers within 1500 m above<br />

model orography, and offers results with a spatial resoluti<strong>on</strong><br />

of 7 km.<br />

Sec<strong>on</strong>d simulati<strong>on</strong>s with the LM were combined with<br />

observati<strong>on</strong>s from satellites. On the <strong>on</strong>e hand we want to<br />

compare the determined results, <strong>on</strong> the other hand the<br />

satellite data can offer realistic input-parameters for the LM<br />

to improve the simulati<strong>on</strong>s. The used satellite systems are<br />

NOAA-AVHRR and LANDSAT-ETM with different spatial<br />

resoluti<strong>on</strong> (NOAA-AVHRR: 1 km, LANDSAT-ETM:<br />

30 m). For the utilisati<strong>on</strong> of the NOAA-data the modular<br />

and hierarchic analysis scheme SESAT (Berger, 2001) was<br />

used, The computati<strong>on</strong> of the Landsat data was realised with<br />

similar algorithms. To remark and remove atmospheric<br />

effects simulati<strong>on</strong>s with radiative transfer codes like<br />

LOWTRAN-7 and 6S are necessary.<br />

During the Litfass03 field campaign in May/June 2003,<br />

which offers validati<strong>on</strong> data, a defect of Landsat’s scan line<br />

corrector occurred, so the two cloud free Landsat scenes for<br />

this time are currently not available. That is why we chose a<br />

golden day (30.05.2003) where at least NOAA-AVHRR<br />

results in additi<strong>on</strong> to LM values can be provided.<br />

Nevertheless it is advantageously to use Landsat scenes<br />

because of the very high spatial resoluti<strong>on</strong> and to realise<br />

methods for scaling up. So we decided to find a comm<strong>on</strong><br />

date for compensati<strong>on</strong> (17.04.2003), for which the fluxes,<br />

especially the evapotranspirati<strong>on</strong>, can be computed with a<br />

variety of methods (LM, NOAA, Landsat).<br />

The results of evapotranspirati<strong>on</strong>, inferred with different<br />

spatial resoluti<strong>on</strong> could be averaged to the LM-grid-cells<br />

(7 x 7 km²) in LITFASS-area. Specific results will be given<br />

for the two datasets: first for April 17 (Landsat data<br />

available) and sec<strong>on</strong>d for May 30 (<strong>on</strong>ly with the AVHRR<br />

dataset and LM results).<br />

3. Results<br />

A first dem<strong>on</strong>strati<strong>on</strong> of the evapotranspirati<strong>on</strong> (LE),<br />

determined with Landsat data and averaged to the LMresoluti<strong>on</strong><br />

for the 17th of April, is shown in Fig 1.<br />

a)<br />

b)<br />

Figure 1: Landsat-LE (a) and averaged (b) to the<br />

LM-grid

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