The Global AEZ study uses a recent global climate data set, which is here referred to as the ‘CRU’ climate database (New et al., 1998). This database comprises a suite of nine climatic variables interpolated from observed station data to a 30 minutes latitude/longitude grid. Each data set contains 720x360 grid-cells. In addition to the 1961-90 climate averages, historical gridded data was obtained from CRU, comprising year-by-year data of the period 1901-1996 also in the form of 30 minutes latitude/longitude grids. The mean monthly climate attributes include: precipitation, wet-days frequency, mean temperature, diurnal temperature range, sunshine duration, windspeed, vapor pressure, and ground-frost frequency. The historical monthly attributes are: precipitation, wet days frequency, mean temperature, diurnol temperature range, and vapor pressure.
| Average annual precipitation |
| Average annual reference evapotranspiration (Penman-Monteith) |
| Monthly precipitation - reference climatology (1961 - 1990) |
| Monthly average temperature - reference climatology (1961 - 1990) |
The year-by-year historical databases, along with the 1961-90 average climate database, have been used to quantify growing period variability and to estimate for each grid-cell by crop/LUT the variability of agro-climatically attainable crop yields.
| The ratio of annual precipitation and reference evapotranspiration |
Average annual rainfall and estimated reference evapotranspiration, calculated according to Penman-Monteith have been compared with average data from climate stations of the FAOCLIM database (FAO, 1995b).
 | Scattergram of (a) annual rainfall and (b) reference evapotranspiration (Penman-Monteith), between grid-cell data from the CRU 1961-90 climate normals database and average station data of the FAOCLIM database |
