PrognosticDiagnostic analysis of ecosystem processes

1
Prognostic/Diagnostic analysis of ecosystem
processes Comparison of MODIS and Biome-BGC based
LAI, GPP and Snow Cover over United States from
2000 to 2003 Kazuhito Ichii 1, Petr Votava 2,3,
Andrew Michaelis 3,4, Ramakrishna Nemani 3 1San
Jose State Univ., 2 California State Univ.
Monterey Bay, 3 NASA Ames Research Center, 4
Univ. of Montana
2. Model Data Sets
1. Introduction
MODIS Products
Biome-BGC
Terrestrial ecosystem models can simulate
terrestrial carbon, water, energy cycles, and
have a potential to forecast future status of
them. However, we need to conduct validation and
comparison studies with observed data for
improving model capabilities and performances.
Four-years of MODIS products, such as Snow cover,
LAI, and GPP provide the opportunity for
validating the terrestrial ecosystem models.
In this study, we used Biome-BGC terrestrial
ecosystem model and MODIS based land surface
products to evaluate the model performance. We
analyzed spatial patterns and interannual
variations over continental United States from
model-based and satellite-based products. We
focused on GPP, snow cover, and LAI over US from
2000 to 2003.
LAI, GPP, Snow Cover over continental US from
2000 to 2003. (1km to 8km resolution)
Terrestrial ecosystem model which simulate
carbon, water, nitrogen, and energy cycle using
daily climate data. (Biome-BGC Ver. 4.1.2
Thornton et al., 2002) LAI calculated
mechanistically from leaf carbon balances of
photosynthesis, respiration, and
litterfall. GPP calculated based on biochemical
photosynthesis model and stomatal conductance
model. Snow cover calculated from precipitation
as snow, sublimation, and melting based on
energy balance.
LAI MOD15A2 GPP TOPS (Terrestrial Observation
Prediction System) Light Use Efficiency model
based on MOD17A2 Algorithm to calculate
GPP. Soil water stress is accounted in addition
to temperature and vapor pressure
deficit. Water cycle model of
Biome-BGC. MODIS FPAR LAI climate data are
used to run the model. Snow Cover MOD10A2
Climate Data
Daily, 8km continental US climate data for
2000-2003 were produced.
Temperature, Precipitation, VPD based on
ground meteorological observations
(NCDC) Incoming Surface Shortwave Radiation
GCIP surface solar radiation data
3. Spatial Patterns MODIS vs Biome-BGC
Snow Cover
LAI
GPP
MODIS (MOD15A2)
Biome-BGC
TOPS
Biome-BGC
Biome-BGC
MODIS (MOD10A2)
Number of days covered by snow
Number of days covered by snow
Annual Max. LAI, 2000-2003 average
Annual GPP, 2000-2003 average
Snow cover (2001-2002 average)
Histograms
Histograms
Summary
Evergreen Needleleaf Forest
Evergreen Needleleaf Forest
Deciduous Broadleaf Forest
Deciduous Broadleaf Forest
LAI Although magnitudes are different, similar
variations are obtained except for grassland
(Most of the central US). Biome-BGC
estimations are lower than MOD15A2. GPP Similar
pattern are obtained except for
grassland. Biome-BGC estimations are higher than
that of TOPS in forest ecosystems, and lower in
grassland. Snow Cover Spatial patterns are
similar. Biome-BGC slightly overestimates snow
cover.
Grassland
Shrubland
Grassland
Shrubland
4. Interannual variations from 2000 to 2003
MODIS vs Biome-BGC
Snow Cover
GPP
LAI
MODIS
Evergreen Needleleaf Forest
Evergreen Needleleaf Forest
6
Biome-BGC
TOPS
MODIS
Biome-BGC
Snow Areas ( 106 km2)
LAI (Biome-BGC)
LAI (MODIS)
GPP (gC/m2/day)
0
MODIS
Deciduous Broadleaf Forest
Deciduous Broadleaf Forest
Biome-BGC
TOPS
Summary
MODIS
Biome-BGC
LAI (MODIS)
LAI (Biome-BGC)
GPP (gC/m2/day)
GPP Snow Cover show similar patterns in each
method.
LAI Seasonal pattern is similar, however,
magnitude is different. Vegetation on the
forest floor mixed vegetation cover are
possible reasons of these differences. GPP
Interannual variations are similar among
these methods. We need further improvement for
grassland. Snow Cover Interannual variation are
very similar between Biome-BGC and MODIS.
Shrubland
Shrubland
MODIS
TOPS
Biome-BGC
MODIS
Biome-BGC
LAI (MODIS)
LAI (Biome-BGC)
GPP (gC/m2/day)
Grassland
Grassland
MODIS
TOPS
Biome-BGC
MODIS
Biome-BGC
LAI (MODIS)
GPP (gC/m2/day)
LAI (Biome-BGC)
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