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Home > Activities > Net Primary Productivity

Net Primary Productivity


New developments

GTOS Terrestrial Ecosystem Demonstration Project Report 831kb - NEW March 2004
Report on Evaluation of Remote Sensing and In-situ Datasets for Carbon Accounting for the Ecosystem Productivity Project of GTOS Report New developments.


Background

The GTOS Net Primary Productivity (NPP) demonstration project was initiated in 1998 to improve the current estimates of global terrestrial primary productivity by comparing ground based measurements of land cover (LC), leaf area indices (LAI) and net primary productivity (NPP) with satellite-derived remote sensing products. The project will serve to calibrate the Moderate Resolution Imaging Spectroradiometer (MODIS) remote sensor on board the Terra satellite launched 18 Dec 1999.


MODIS sensor

The advantage of using the MODIS remote sensor is that the data is collected from a single source (i.e. the sensor) so it can provide complete globally consistent measurements of seasonal growth and annual NPP for all vegetation types. The data can be used for a number of scientific applications, including defining carbon budgets and in resource management applications such as food/fibre/fuel production. Before the MODIS datastream can be used for such purposes rigorous testing and validation need to be carried out by sites which have different climatic and ecological conditions. The GTOS NPP Demonstration project is coordinating a validation effort of the MODIS NPP data with site measurements.

For further information on project developments consult the websites of the Numerical Terradynamic Simulation Group (NTSG) and the MODIS land team validation.


Uniform sampling protocols


In the year 2000 the BigFoot project established uniform field sampling protocols for field sites, so that consistent NPP data can be collected for direct comparison to the MODIS derived global datastream (Further details).


Workshops

MODIS NPP data products have been produced globally since December 2000. This will allow a first comparison of global satellite, and ground based annual NPP data to be carried out by the end of 2001. A number of workshops were held during 2001 in preparation for this collaboration (further details).


Database update

During 2001, the database, developed to support information and data exchange within the NPP demonstration project, was modified and updated with new site information. MODIS data products have been downloaded from NASA sources for most of the 26 sites participating in the GTOS NPP Project and placed online within the NPP project webpage for sites to access.


Data products

At present global MODIS data is available on the Internet in the form of 1100 x 1100 km "tiles" from the EROS Data Center. Beginning in the summer of 2001 regular 7 x 7 km cutouts of selected MODIS products are being made available to FLUXNET and other partici-pating GTOS-NPP sites by the Oak Ridge National Laboratory Distributed Active Archive Center (ORNL DAAC). NASA expects the entire 2001 year of MODIS land products to be processed and available by March 2002.


Collaborating networks


Two field site networks are planning to contribute to GTOS NPP. These are FLUXNET, a global network of eddy covariance flux towers and the International Long Term Ecological Research (ILTER) network.

Currently 54 FLUXNET sites are receiving the MODIS cutout datastream every eight days.

As scientific validity of the MODIS global NPP is established, cooperating sites will be able to begin using the data for wider regional monitoring of the vegetation dynamics of their areas. Cooperating sites will be able to use local weather and topographic data to refine the global MODIS NPP estimate, modifiers for local vegetation types, and merging the MODIS ima-gery with higher reso-lution satellite data such as IKONOS, SPOT or Landsat. The MODIS NPP will then provide a consistent regionally-scaled measure of vegetation that has not previously been available.

Workshops to compare ground validation measurements with the MODIS data products produced during 2001 will be held in 2002.

Updated information is available on the GTOS NPP Project webpage.

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© FAO   ::   Global Terrestrial Observing System - GTOS   ::   16 May 2002