Fig. 5
From: Classification of drought severity in contiguous USA during the past 21 years using fractal geometry
Histogram of Continental US (CONUS) Percent Area in US Drought Monitor Categories database (2000–present). The histogram uses five classifications: abnormally dry (D0), showing areas that may be going into or are coming out of drought, and four levels of drought: moderate (D1), severe (D2), extreme (D3) and exceptional (D4); Source(s): National Drought Mitigation Center (NDMC), the US Department of Agriculture (USDA), and the National Oceanic and Atmospheric Administration (NOAA)