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Coverage, spatial and temporal resolution
Time period and temporal resolution:
- 07/1981 - 12/2011
- half-monthly: 07/1981 - 02/2000
- 8-daily: 02/2000 - 12/2011
Spatial coverage and resolution:
- Spatial resolution: about 0.0727°, cartesian grid
- Geographic Latitude: 62.7771°S to 89,2229°N
- Geographic Longitude: 179.996°W to 179.932°E
- Dimension: 2091 rows x 4950 columns
- Altitude: following terrain
Both data sets used for this synthesis have been thoroughly validated; the MODIS data sets are those of release 5.
For 99% of the investigated vegetated area of the overlap period 2000-2006 the difference between new AVHRR LAI and MODIS LAI is less than 0.6. Comparison of the long LAI time series with field plot measurements reveal a mean uncertainty of 0.81. More results can be found in Tucker et al. (2005), Deng et al. (2006), and Liu et al. (2012) (see references).
Since publication of the data set (Liu et al., 2002) two major improvements have been already realized. On the one hand, the so-called "clumping effect" (He et al., 2012, see references) is used to take into account the different density of the vegetation. On the other hand the cloud detection has been improved.
Further planned improvement is consideration of canopy layers, removal of a negative bias over grass and an improved mitigation of the impact of clouds in tropical latitudes and snow in boreal forests.
Institute of Geographical Sciences and Natural Resources Research
Chinese Academy of Sciences, Bejing, China
email: liurg (at) igsnrr.ac.cn
ICDC / CEN / University of Hamburg
email: stefan.kern (at) uni-hamburg.de
Liu, Y., R. Liu, and J. M. Chen (2012), Retrospective retrieval of long-term consistent global leaf area index (1981-2011) from combined AVHRR and MODIS data, J. Geophysical Research, 117, G04003, doi:10.1029/2012JG002084.
Data have been provided in netCDF format by the Integrated Climate Data Center (ICDC, http://icdc.cen.uni-hamburg.de), University of Hamburg, Hamburg, Germany.