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note > note 17 |
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LocClim CD-ROM v1.0, the FAO Local Climate Estimator LocClim provides estimates of climatic conditions at locations for which no observations are available. The programme is based on the 28800 stations of FAOCLIM 2.0, the global agroclimatic database maintained by the Agrometeorology Group of FAO (see www.fao.org/sd/2001/EN1102_en.htm). These estimates are also directly accessible for each registered sites in TEMS (see www.fao.org/gtos/tems/tsite_list.jsp).
Technical features
Next to a "no questions asked" automatic mode, the "benchmark" mode gives full control over the interpolation procedure (Inverse Distance Weighting). Inputs (locations) can be entered manually by specifying the co-ordinates or by clicking on a map; or they can be imported from an ASCII file. Outputs are generated as ASCII files or user-defined georeferenced grids in WinDisp format (see www.fao.org/ES/giews/english/windisp/windisp.htm).
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 climatic variables are given together with error estimates, using a number of options to correct regional variability, altitude dependency and horizontal gradients. For any given location, LocClim searches for the nearest stations fulfiling a given criteria (absolute number, maximum distance, altitude constraints).
If needed 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 performs a 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.
Free copy
For a free copy
of LocClim CD-ROM v1.0, kindly send a request to gtos@fao.org,
providing your full mailing address. Please feel free to contact
the Agrometeorology Group (agromet@fao.org)
for further information or comments on LocCLIM.
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