USING TEMPERATURE TO CALCULATE THE DRYNESS INDEX OF GRAPE PRODUCTION REGIONS

The Geoviticulture Multicriteria Climatic Classification System (CCM), used to characterize the climate in grape production regions, is composed by the Heliothermal Index (HI), the Cool Night Index (CI) and the Dryness Index (DI), which is based on the potential soil water balance. The calculation of DI values requires precipitation and evapotranspiration potential (ETP) data, estimated using the standard Penman-Monteith method. However, not all grape regions have the climatic variables required to use this ETP method. Therefore, it is important to use other methods to estimate ETP based only on air temperature available data, such as the Hargreaves ETP method. The present study compared the Drought Index values calculated using the Penman-Monteith and the Hargreaves methods for different grape growing regions of the world. Climate data from 83 meteorological stations were used, representing grapevine regions located in 18 countries. The Hargreaves equation achieved a very good performance and can be used in the CCM system in places where there are insufficient data for the Penman-Monteith method.