R Masoudi - PhD Student of De-Desertification, University of Tehran, Karaj, Iran
Gh Zehtabian - Professor, Faculty of Natural Resources, University of Tehran, Karaj, Iran
T Mesbahzadeh - Assistant of professor, University of Tehran, Karaj, Iran
H Khosravi - Assistant of professor, University of Tehran, Karaj, Iran

In this study, the severity, duration and extent of drought during 1965 to 2006 have been studied using annual precipitation data of Kashan region. Meteorological drought index, Percent of Normal precipitation Index (PNPI) has been used in order to assess and compare their capability for drought severity and duration in annual scale. Finally, for the purpose of study on the drought extent, the zoning map has been prepared by IDW method. Also the frequency curves of drought were drawn by Excell. The consequences resulting from the zoning of drought severity, have illustrated that, the most durable drought, Based on PNPI has occurred during 1980-1981at Fin station. After calculating PNPI Index values, is drawn frequency curve and based on the result obtained, the most percentage of frequency is belong to normal rain.

Percent of Normal precipitation Index (PNPI), Kashan