An evaluation of the Standardized Precipitation Index, the China‐Z Index and the statistical Z‐Score

Abstract

The Standardized Precipitation Index (SPI) was developed to detect drought and wet periods at different time scales, an important characteristic that is not accomplished with typical drought indices. More and more users employ the SPI to monitor droughts. Although calculation of the SPI is easier than other drought indices, such as the Palmer Drought Index, it is still relatively complex. In China, an index called the China-Z Index (CZI) has been used since 1995 by the National Climate Centre of China to monitor moisture conditions across the country. The calculation of this index is easier than the SPI. A third index, the statistical Z-Score, can also be used to monitor droughts. This paper evaluates the SPI, CZI and Z-Score on 1-, 3-, 6-, 9-and 12-month time scales using monthly precipitation totals for four locations in China from January 1951 to December 1998 representing humid and arid climates, and cases of drought and flood. Advantages and disadvantages for the application of each index are compared. Study results indicate that the CZI and Z-Score can provide results similar to the SPI for all time scales, and that the calculations of the CZI and Z-Score are relatively easy compared with the SPI, possibly offering better tools to monitor moisture conditions.

Use of the gamma distribution to represent monthly rainfall in Africa for drought monitoring applications

“…For example, at geographic locations whereq is larger than 0.5, the gamma distribution parameters are being estimated by fewer than 18 samples (out of 36 years) and the parameter reliability becomes quite suspect. Research applying estimated distribution parameters suggests that over 30 years of data be used in the estimation of parameters (McKee, 1993;Hayes et al, 1999;Wu et al, 2001).…”

Agricultural Drought Modeling Using Remote Sensing

“…SPI based drought identification has been utilized by [4] to monitor the 1996 drought in the United States of America. Although it is quite a recent index, the SPI was used in Turkey [5], Argentina [6], Canada [7], Spain [8], Korea [9], Hungary [10], China [11] and Europe [12] for real time monitoring or retrospective analysis of droughts. NDVI-rainfall relationship was also used in monitoring drought on a large scale in north east Thailand [13], East Asia [14] and the Central Great Plains of US [15] using NOAA/AVHRR data.…”

Assessment of areal interpolation methods for spatial analysis of SPI and EDI drought indices

“…Many drought indices have been developed to date. These include the Palmer Drought Severity Index (PDSI) (Palmer, 1965), which is widely used in the USA, the Deciles Index (Gibbs and Maher, 1967), which is operational in Australia, the China-Z Index (CZI), which is used by the National Metrological Center of China (Wu et al, 2001), Standardized Precipitation Index (SPI) (McKee et al, 1993), which has gained world popularity, etc. The review of drought indices can be found in several sources (e.g.…”