The simulation was performed for a typical day, 24 September 2010, when the structure of rolls was observed as shown in The life time of these structures on the day was about 4 h from 7.30 LT to 11.30 LT.After 11.30 LT, these rolls were transformed to cells. Once the sea breeze sets, cloud structures disappeared in the region of sea breeze over the land and were found inland ahead of the sea breeze front. The large scale features simulated by the mesoscale model over the outer domain on this day (figure not shown) confirm that the synoptic lower level wind was south-west near Kalpakkam and the magnitude of the wind was higher in the sea side whereas the land side was relatively calm. The simulated innermost domain wind at hundred meters above ground level (Fig. 5a and b) showed regions of convergence
and divergence. Also alternate high and low wind speed streaks were visible which are between 2.5 and 4.5 m/s in
magnitude. The convergence areas are characterized by low wind speed and divergence areas by highwind speed. Similarly the simulated vertical velocity and cloud fraction (Fig. 5c andd) confirm the presence of roll vortices. Simulated spatial cloud fractions havewave length and pattern similar to the observed satellite image. However, low resolution domain configuration failed to resolve this cloud structure (figure not shown). Another feature observed in the numerical simulation is that the boundary layer height exhibited awavy nature as shown in the Fig. 6a with maximum height of 550 m and a minimum height of 350 m. Such a feature in boundary layer height was also observed with a wind profiler by Miao and Chen (2008).