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Title: AN APPLICATION OF GPCC AND NCEP/NCAR DATASETS FOR DROUGHT MONITORING IN IRAN

Author: T. Raziei, I. Bordi and L. S. Pereira

Year: 2009

Publisher: European Water Resources Association (EWRA)

Description:

The lack of reliable and updated precipitation datasets is the most important limitation that hinders establishing a drought monitoring and early warning system in Iran, which is one of the most drought prone countries in the world. To overcome this obstacle we have evaluated the applicability of GPCC and NCEP/NCAR precipitation datasets for drought analysis in Iran. For this purpose, drought variability across the country has been analyzed by computing the Standardized Precipitation Index (SPI) on 12-month time scale based on the common period 1951–2005. For each dataset, by applying the S-mode PCA to the SPI field and Varimax rotation, the studied area has been regionalized into a few distinctive sub-regions characterized by independent climatic variability. To verify the results against observations at rain gauges, 32 synoptic stations having monthly precipitation data for the study period have been considered and the same procedure has been applied to analyze the space/time variability of drought across the country. Results show that both datasets identify the same sub-regions of drought variability and they are in good agreement with those found using observations. However, the NCEP rotated principal components associated with the sub-regions show different time variability with respect to the behaviors captured by GPCC and observations. Such differences that concern mainly the period 1951–1970 have been investigated. Thus, the study suggests that GPCC precipitation dataset is a useful tool for drought monitoring in Iran and can be used to complement the information provided by rain gauge observations. The NCEP/NCAR reanalysis dataset shows a good agreement with observations for the period 1970–2005, and its discrepancies with GPCC and observations should be taken into account when periods before 1970 are considered.