Fourth Study Conference on BALTEX Scala Cinema Gudhjem

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Validation of Boundary Layer Parameters and Extension of Boundary
Conditions of the Climate Model REMO – Estimation of Leaf Area Index
from NOAA-AVHRR-Data
Birgit Streckenbach und Eberhard Reimer
Institute of Meteorology, Free University of Berlin, Carl-Heinrich-Becker-Weg 6-10, streckba@zedat.fu-berlin.de
1. Introduction
At this time the climate model REMO of the Max-Planck-
Institute Hamburg works with fixed regional vegetation
parameters for every month of the year. To obtain a better
adaptation to real conditions the estimation of the annual
changes in vegetation, especially deciduous forests, which
significantly influence the boundary layer processes and in
particular the moisture budget, is necessary. The Leaf Area
Index (LAI) is a characteristic indicator for the type of
vegetation and its activity.
2. Data and Method
At the Institute of Meteorology of the Free University Berlin
NOAA-AVHRR data for the European region are available
day by day since 1989. The data are corrected to eliminate
typical errors referring to calibration and shift in observation
time. They are also adjusted to geographic coordinates and
to a land mask.
On the basis of these data from 1995 until 2002 during the
vegetation period (April-September) the LAI in the Baltic
region was predicted pixelwise from the Normalized
Difference Vegetation Index (NDVI) for 1km x 1km resolution
using an algorithm from Sellers et al. (1996).
At first 10 day composites of the NDVI were created to
eliminate the disturbing influence of cloudiness. Missing or
incorrect pixels were completed in time by harmonic
analysis and regionally by pixel neighbourhood reconstruction.
From these NDVI values the Fraction of Absorbed
Photosynthetic Active Radiation (FAPAR) was predicted
and then the LAI was determined using a modified USGS
land cover classification. Finally the 1km x 1km, 10 day
averaged LAI data were converted into the 1/6 degree
resolution of the REMO climate model.
3. Results
In Figures 1 and 2 the Normalized Difference Vegetation
Index and the Leaf Area Index are shown for the second
decade of June 2000 in the Western part of the BALTEX
region, derived from NOAA-AVHRR data. with a resolution
of 1km x 1km.The regional variability of the NDVI values is
not very strong.. In difference the LAI shows very high
values in the Southern parts of Scandinavia and in the Alps
region. The landuse in these region is characterised by
agriculture, grassland and deciduous forests. This figure is a
good example for the LAI as indicator for the activity of
vegetation and biomass production. For the detection of the
interannual LAI development and its changes from year to
year in dependence of the weather conditions LAI data sets
over a period of seven years for the whole BALTEX region
were created. They allow to make statistical evaluation and
to test the sensitvity of the REMO model against varying
vegetation parameters. To validate the used land cover
classification ASTER and Landsat7 scenes with a resolution
of 250m up to 15m for single days were evaluated and
compared with the NOAA data sets (DBS GmbH Mohnen).
Figure 1. High resolution NDVI for the Western part of
the BALTEX region (June 2000)
Figure 2. High resolution LAI for the Western part of the
BALTEX region (June 2000)
References
Sellers, P.J., Los, S.O., Tucker, C.J., Justice, C.O.,
Dazlich, D.A., Collatz, G.J. and D.A. Randall, A
revised land surface parameterization (SiB2) for
atmospheric GCMs. Part II: The generation of global
fields of terrestrial biophysical parameters from
satellite data. Journal of Climate, Vol. 9, pp. 706-737,
1996