The tables of the return thresholds can be directly used to interpolate the ARI
for a given precipitation amount as shown in Fig. 1b. For
example, Fig. 1b shows that a daily rainfall of 70mmor a
10-day accumulation of 170mm would be qualified as a
10-yr event in this particular location. The near-realtime
precipitation accumulations from the past 1, 2, 3, 5,
7, and 10 days are converted into ARI by interpolation.
Figure 1b is in fact another form of intensity–duration–
frequency (IDF) curve commonly used in the hydrological
community where duration and rain depth are
plotted for given return year. The IDF curves are used as
references for infrastructure design and flood risk assessment.
However, because of the short data record
and large uncertainty with theTRMMdata (discussed in
section 3b), we do not recommend using these lookup
tables for engineering reference at the present stage.
The schematic of the TRMM ARI extreme rain alert
system is shown in Fig. 2. The initial plan is to update the
ARI maps daily as soon as the latest 3B42RT daily data
become available.