What is CZI(China-ZIndex) and MCZI (Modified CZI)?

The National Climate Center of China developed the CZI in 1995 as an alternative to the SPI (Ju et al., 1997) when mean precipitation follows the Pearson type III distribution. AgMerra Drought paper. You can calculate CZI and MCZI with 6 other indies by using Rain-based Drought Index in AgriMetSoft products.

Different from SPI, the CZI is related to the Wilson-Hilferty cube-root transformation (Kendall and Stuart 1977), and the detail computation process can be seen in Wu's(2001) literature. The two indices are widely used in China, for the data needed is relatively easily acquired (Yuan and Zhou 2004), and the temporal-spatial adaptability is relatively great, because it is independent of drought mechanism.

Wu et al. (2001) expressed three indices, including Standard Precipitation Index (SPI), China Z and Z-Score Index (ZSI) for the dry and humid climate in China and described their advantages and disadvantages by monthly precipitation data. They also attempted deferential deduction of Standard Precipitation Index. and Modified CZI. The overall differences between these two indices reduced significantly compared to the difference between the SPI and CZI.

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