The relationship between spatial extent and duration of severe droughts in China over the last 50 years

Correlation between spatial extent and duration of severe droughts process and its statistical law is analyzed using Palmer Drought Severity Index (PDSI) through a newly developed system of drought process monitoring. Results indicate that during the period from late 1990s to early 2000s, the percentage of severe drought (PDSI<;-3.0) in China is unprecedented since 1960 under the background of global warming and the variation of the distributions of droughts coverage areas in different seasons is uneven. The distribution of spatial extent and durations of severe droughts follows a power-law, e.g. the spatial-temporal characteristics of severe droughts is independent to their scaling, namely, being scale free. In general the area of severe droughts is correlated closely with its duration, while the deviations of the linear fit from its correlation is also high.