The statistics and the threshold tables
will be updated on a yearly basis when all data from the
previous year become available. For the web application,
global maps will show the locations of extreme
events with ARI larger than 5 years represented with the
largest ARI in the area. Clicking the symbols on the
global map can access enhanced regional maps. Figure 3
shows an example of daily precipitation and an ARI
map on 27 April 2011. The precipitation map shows
areas of heavy precipitation but provides no information
on the rarity of these events. The ARI map highlights
the areas with locally rare precipitation accumulations
that could lead to potential hazards, especially over the
lands. For example, a big red dot in the southeastern
United States captures the heaviest rain episode with
ARI . 50 yr during the April–May period in 2011. A
series of heavy rain events during this period led to
massive lower Mississippi River floods—one of the
largest and most damaging flooding events recorded
along this U.S. waterway in the past century. This
product provides additional information of the relative
severity of ongoing precipitation events on short and
medium time scales that is significant for disaster management. Since ARI is location specific and duration
dependent, such properties make ARI particularly
relevant for public awareness.