Role of Surface Roughness Length on Simulation of Cyclone Aila - Monitoring and Prediction of Tropical Cyclones in the Indian Ocean and Climate Change - page 253

3. Results and Discussions

The numerical experiments indicate that the model simulated tracks of TC
Aila had biased to right side of the observed track (Fig. 1a). It is noticed that
there is not much differences in track simulation among the different
experiments. However, when the system approaches the land, the track
simulated from Zo+50 run becomes nearer to the observed track as compared
to the other two runs. Though there is an error in landfall position, the time
error is zero from this experiment. The CNTL and Zo-50 runs simulate the
tracks more or less similar. However, sometimes, the CNTL run shows better
track prediction with 10-15 km less errors at different forecast lengths (Fig.
1b). Though all the runs capture the inland movement of TC Aila, the error is
less in Zo+50 run. The study of Wada and Kohno (2010) also mentioned that
the increased surface roughness length has impact on track simulation. Figure
1c shows the intensity evolution of TC Aila and it is clear that all the runs
overestimate the intensity. The arrow line represents the landfall. The CNTL

2606

CNTL

Zo - 50
Zo + 50

2600

2518
2512
2506

2500
2418
2412
2406
2400
12UTS23 May 2009

Fig. 1: (a) Model simulated tracks of TC Aila along with IMD observed track, (b) track
forecast errors (km) in 6-hr interval and (c) time series of model simulated intensity
(10 m maximum winds, m/s) along with observed intensity from three experiments,
CNTL, Zo-50 and Zo+50.