The percent area of the CONUS experiencing record dry PHDI is shown in Table 1.
The PHDI for a climate division becomes more negative as dry conditions continue and becomes less negative during wet weather.
The differences in mean percent area with PHDI [less than or equal to] -2.
bottom) Difference in frequency distribution of PHDI for the three major drought episodes: 1998-2014 minus 1949-57 (blue triangles), 1998-2014 minus 1928-42 (red circles), and 1949-57 minus 1928-42 (black squares).
Spatial pattern of occurrence of record dry PHDI, by decade or drought period.