AVHRR to MODIS transition

1
AVHRR to MODIS transition Implications for
ecosystem modeling Amazon Rainforests Ramakrishn
a Nemani Kazuhito Ichii Hirofumi
Hashimoto Alfredo Huete Ranga Myneni August 7,
2006 VI Validation Pre-WorkshopValidation of
global vegetation indices and their time series
(A CEOS Land Product Validation topical workshop)

2
Rainforests

• Contribute to a large fraction of global carbon
  and water cycling
• Most difficult target for remote sensing
• cloud cover
• aerosols

3
Earlier studies showed similar behavior between
AVHRR and MODIS VIs with slightly higher
magnitudes for MODIS NDVI
SEMI-ARID AFRICA
4
CENTRAL EUROPE
Sensor intercalibration adjustment of MODIS-NDVI
to NOAA-AVHRR NDVI, Jonas Franke and Guenther Menz
5
Over tropical rainforests
Similar analysis over Amazon shows
6
Not much correlation
More troubling is the seasonality
GIMMSg 81-2003 monthly averages MODIS 2000-2005
monthly averages
7
On further analysis..
8
5x5 degree averages
9
5x5 degree averages
10
Implications for carbon cycling
FPAR seasonality
AVHRR FPAR based on Myneni et al., 1997 MODIS
FPAR from MOD15 C4
11
NOAA- Advanced Very High Resolution Radiometer
(AVHRR) in the Amazon
12
Rainforest GPP EVIwith modeled GPP (IBIS) at
Tapajós
GPP from Lucy Hutyra (Harvard Univ)
13
This offers new approaches to constrain rooting
depth in terrestrial ecosystem models over the
Amazon using MODIS EVI satellite data and
Biome-BGC terrestrial ecosystem model.
Ichii, K
Ichii, K
14
Implications for carbon cycling
Gross Primary Production
AVHRR underestimates in dry season with high GPP
15
Implications for carbon cycling
Gross Primary Production
AVHRR underestimates the rate of GPP during
green-up
16
Different MODIS products show different
vegetation seasonality in Amazon
Area
2001-2004 Average
17
Modeling LAI seasonality
18
Tower GPP flux
19
summary

• MODIS and AVHRR show very different behavior over
  Amazon rainforests.
• Differences may be largely due to processing.
• Changes in FPAR between the two instruments
  results in gt15difference in GPP.
• Significant differences exist in GPP seasonality.