| Environment and Natural Resources, Working paper No. 9 (CD-ROM) | February 2002 |
Climatic conditions are recorded for very few locations on earth and
most of the time, when an agricultural development project is planned,
or when a climate-related risk assessment is to be carried out, the
experts have to resort to using data from distant stations.
Dr Jürgen Grieser, now at the Global Precipitation Climatology Centre
of the German Meteorological Service has spent several months with the
Agrometeorology Group of the Environment and Natural Resources Service
(SDRN) of FAO to develop a tool, LocClim, an abbreviation of Local
Climate, to answer the very common question about climate in a location
where there is no climate observing station.
Overview
LocClim was developed to provide an estimate of climatic conditions
at locations for which no observations are available. To achieve this,
the programme uses the 28800 stations of
FAOCLIM 2.0,
the global agroclimatic database maintained by the Agrometeorology Group of FAO.
Next to a "no questions asked" automatic mode, the "benchmark" mode
gives the user full control over the interpolation procedure
(Inverse Distance Weighting). Inputs can be taken from the keyboard
(location specified either by co-ordinates or by a click on a map)
or from user-provided ASCII files. Output can be in the form of ASCII
files or user-defined georeferenced grids in
WinDisp format.
The programme also provides estimates of growing season characteristics
based on a comparison of rainfall and potential evapotranspiration
(Franquin's method).
Estimates of monthly, 10-daily and daily values of common climate
variables are given together with error estimates, using a number
of options to correct for regional variability, altitude dependency
and horizontal gradients of the variables. For any given location
LocClim searches for the nearest stations that fulfil given criteria
(absolute number, maximum distance, altitude constraints).
If desired LocClim fits a linear altitude function through the observations to
reduce all of them to the elevation of the desired location. This
minimises the systematic error resulting from the different elevations
of the neighbouring stations. The altitude of the desired location
can either be given by the user or taken from a built-in digital
elevation model (DEM) with a spatial resolution of 10 km and an
altitudinal resolution of 20 m (DEM downgraded from the NOAA/NCDC
Global Land One-kilometre Base Elevation). LocClim can perform
climate gradient correction by fitting a plane surface to the
observations over the latitude-longitude plane. Thus the smooth
geographical climate variation is taken into consideration. If
desired a shadowing routine can be applied that gives neighbours
hidden by closer neighbours a low weight.
For details or for booking a copy of the LocClim CD-rom, kindly send
an email to agromet@fao.org.
For more information, contact:
Chief-SDRN@fao.org or
Environment@fao.org
Other tools:
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