Geoscience Reference
In-Depth Information
3.4 Energy Metrics of TCs over NIO
Different energy metrics like Accumulated Cyclone Energy (ACE) and Power
Dissipation Index (PDI), which can be used to define the TC activity,
are calculated for each year. These parameters take into account the number,
strength and duration of all the tropical storms in the season. ACE and PDI are
defined as:
ACE = 6
v
2
max
having units
(10
4
kt
2
)
and
PDI = 6
v
3
max
with units
(10
6
kt
3
)
where
v
max
is intensity of TC and is calculated six-hourly for each TC and then
summed up for all TCs in the season for a year. Time series of ACE and PDI,
for the North Indian Ocean show significant increasing trend over 30-year
period (Fig. 5). Trends for ACE and PDI are given as:
years
Fig. 5:
Trend in energy parameters and NTC activity over the NIO
during 1979-2009.
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