H. Wu et al., An evaluation of the Standardized Precipitation Index, the China-Z Index and the statistical Z-Score, INT J CLIM, 21(6), 2001, pp. 745-758
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 emplo
y the SPI to monitor droughts. Although calculation of the SPI is easier th
an other drought indices, such as the Palmer Drought Index, it is still rel
atively 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 moistur
e conditions across the country. The calculation of this index is easier th
an the SPI. A third index, the statistical Z-Score, can also be used to mon
itor 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 lo
cations 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 tha
t the CZI and Z-Score can provide results similar to the SPI for all time s
cales, 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. Copyright: (C) 2001 Royal Meteorological Society.