Improvement in Track and Intensity Prediction of Indian Seas Tropical Cyclones with Vortex Assimilation - Monitoring and Prediction of Tropical Cyclones in the Indian Ocean and Climate Change - page 219

respectively. At the initial time, significant improvement in the vortex position
is noticed. The initial vortex position improvement of 48%, 27% and 37% is
clearly depicted from the initial condition of 12 UTC 23 May 2009, 00 UTC
24 May 2009 and 12 UTC 24 May 2009 respectively. The improvement in
track prediction is clearly noticed throughout the life cycle of the cyclone Aila.
At the same time, the landfall position also improved with the DA experiments
than the CNTL simulations. The landfall time as well as the error are highlighted
(through oval shape) for each initial condition. The initial condition of 12 UTC
23 May 2009, shows the landfall point error of 148 km with CNTL experiment,
whereas it has reduced to 87 km in DA experiment. Similarly, the model
integration with the initial condition of 00 UTC 24 May 2009 provides the
landfall error of 148 km and 89 km in CNTL and DA experiments, respectively.
The landfall error of 121 km and 30 km is simulated with the initial condition
of 12 UTC 24 May 2009 from CNTL and DA experiments, respectively. Thus,
it is noticed that the improvement of 41%, 39% and 76% is achieved at the
landfall position with the DA experiment from the initial condition of 12 UTC
23 May 2009, 00 UTC 24 May 2009 and 12 UTC 24 May 2009, respectively.
Figure 3 represents the model simulated track and associated VDE (km)
for tropical cyclone Gonu. Figure 3(a and b) represents the tracks of the cyclone
Gonu with five different initial conditions (00 UTC 02 June 2007, 12 UTC 02
June 2007, 00 UTC 03 June 2007, 12 UTC 03 June 2007 and 00 UTC 04 June
2007) from CNTL and DA simulations, respectively. The CNTL simulation
shows the wide spread of the track of the cyclone, whereas the DA experiment
provides much confined track towards the landfall position. The VDE (km)
associated with each initial condition are evaluated and the mean VDE is
presented in Fig. 3(c). The mean improvement of 26% is noticed at the initial
time of the model integration with the DA experiment than that of the CNTL
simulation. Also the forecast position steadily improved during the life cycle
of the cyclone, Gonu. The improvement of 34% and 44% is noticed at 24 hr
and 48 hr forecast respectively. The details of the VDE are provided in Table 2.
Fig. 3: Track of cyclone Gonu with different initial conditions from (a) CNTL, (b) DA
experiments and (c) mean vector displacement errors in both CNTL and DA experiments
and % of improvement in DA experiment w. r. t. CNTL simulation.