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Hierarchical Observing Strategy (GHOST)
Global Hierarchical Observing Strategy (GHOST) is an information
gathering system shared by both the terrestrial and climate
responds to the need for reliable, representative, long-term
data about the earth's land and freshwater ecosystems. The
system works on a global scope because many of the processes
affecting the quality of the environment occur beyond national
boundary lines - climate change, desertification and transboundary
pollution are examples. The system uses a long-term strategy
because the processes involved may be slow, but cumulatively
dangerous. The need for a long observation period and global
coverage means that the measurements must be made very consistently
if they are to be comparable. The scope of the effort requires
that the observing system be designed for maximum efficiency.
is a hierarchical strategy. On the macro level a few variables
are measured regularly in a large number of places, and
on the micro level a large number of variables are measured
in a few locations for a limited period. The hierarchy divides
into five tiers, each with unique characteristics and roles,
although existing facilities often straddle more than one
tier (see Table 1). The concept is applicable to the three
main areas which GHOST is concerned with - the land surface,
freshwater ecosystems and ice surfaces - each with its own
hierarchy, but all share tier five (Table 1). The observing
system is built largely out of existing national and international
observation systems and research centres, with modest additions
of stations and sites where representation was previously
inadequate. GHOST was designed with a heavy emphasis on
methodological consistency and efficient data management.
1 Examples of terrestrial carbon information users
Large area experiments e.g., IGBP transcets, large catchment
of spatial structure and processes.
a linear dimension of >100 km, very intensive sampling,
highly integrated data sets.
Research centres e.g., Large LTERS, large agricultural
processes, experimentation, method development, data
research on a crop, ecosystem or cryosphere type, one
per major type. Generally expensive complex instruments.
Stations e.g., Biosphere reserves, smaller national
agricultural and ecosystem research sites, research
catchments, small polar stations.
measurement of variables which vary over periods from
weeks to years. Calibration and validation of remotely-sensed
variables. Trends of variables.
existence, representative of the range within a type,
but not statistically unbiased. Frequent measurement
Sample sites e.g., US EMAP programme, UK country survey.
measurement of variables not observable by remote sensing,
calibration and validation of remotely-sensed variables,
status and trends of biome health.
visited (once per year to once per decade), large sample,
Remote sensing e.g., AVHRR, SPOT, Landsat.
and temporal interpolation at scales down to 1 day and
30 metres. Extent of biome, ice sheets, etc., status
and trends of a biome health.
complete coverage, variables mostly indirectly observed.
a. The numbers indicated
are estimates only and may vary significantly especially
at tier 3. Approximately in the ratios: 35 natural ecosystems;
35 agroecosystems; 10 rivers; 10 lakes; 10 cryosphere.
more information on GHOST, please refer to two published
reports from the planning phase: GTOS-12
FAO :: Global Terrestrial
Observing System - GTOS ::
16 May 2002