What is multi-scale drought analysis with SPI and SPEI?
In short: multi-scale drought analysis computes the SPI or SPEI at several accumulation periods (for example 1, 3, 6, 12, and 24 months) at the same time, because each scale reveals a different drought: short scales track soil-moisture and agricultural drought, while long scales track hydrological drought. Comparing the scales shows how a drought begins, propagates, and persists. DMAP V2.1 computes multi-scale SPI and SPEI in a single run.