The above examples show that the ARI maps are
capable of highlighting regions with particular severity
when a large system of extreme precipitation occurs.
Severe floods and landslides often occur in areas of elevated
ARI or downstream of these areas. Table 1
provides additional examples of some of the most notable
and catastrophic flood or landslide events triggered
by extreme precipitation since 3B42RT data
became available. In each case, the elevated ARI index
would provide warning for the ongoing event. We point
out that the ARI values depend not only on the actual
rain amount but also on the local climatology. For
example, a 5-day precipitation accumulation of 100mm
from Ethiopia counts as a 10-yr event in ARI, yet a 5-day
amount of 500mm in Leyte, Philippines, is only equivalent
to a 4-yr event. It is well known that the severity of
flood or landslide events is not necessarily proportional
to the magnitude of ARI, as floods and landslides depend
on a number of other factors, such as the preceding
events, topography, stream distribution, and soil moisture.
The actual damage also depends highly on the local
population and development. Nevertheless, ARI maps
could provide a near-real-time assessment of the heavy
precipitation events that would potentially lead to catastrophic
results. The ARI information could be incorporated
or serve as supplemental information to
locally more sophisticated flood or landslide monitoring
system. It could also provide awareness of the going
extreme precipitation events around the world for the
general public.