Simulation of coastal winds along the central west coast of India using the MM5 mesoscale model

Abstract

High resolution mesoscale model (MM5) has been used to study the coastal atmospheric circulation of central west coast of India, and Goa in particular. The model is employed with three nested domains. The innermost domain of 3km mesh covers Goa and the surrounding region. Simulations have been carried out for three different seasons -northeast (NE) monsoon, transition period and southwest (SW) monsoon with appropriate physics options to understand the coastal wind system. Simulated wind speed and direction match well with the observations. The model winds show the presence of sea breeze during the NE monsoon season and transition period, and its absence during the SW monsoon season. In the winter period, the synoptic flow is northeasterly (offshore) and it weakens the sea breeze (onshore flow) resulting in less diurnal variation, while during the transition period, the synoptic flow is onshore and it intensifies the sea breeze. During the northeast monsoon at an altitude of above 750 m wind direction reverses, and this is the upper return current, indicating the vertical extent of sea breeze. Well developed land sea breeze circulation occurs during the transition period, with vertical extension of 300 m and 1100 m, respectively.2

Sea breezes at Cotonou and their interaction with the West African monsoon

“…Large-scale flow is characterized by the strong onshore winds that intensify the sea breeze in this period. Such an effect of the synoptic flow has been observed by Pushpadas et al (2010) in a numerical model for the west coast of India.…”

“…Such an effect of the synoptic flow has been observed by Pushpadas et al . () in a numerical model for the west coast of India.…”

“…Pushpadas et al . () in a numerical model for the west coast of India found that in the winter period, the synoptic flow is northeasterly (offshore) and weakens the sea breeze, while during the transition period between northeast monsoon and southwest monsoon, the synoptic flow is onshore and intensifies the sea breeze.…”

“…For instance, in the Bay of Alicante (Spain), it has been found that in comparison with onshore synoptic flows, offshore favours the delayed arrival and termination of sea breezes, resulting in a longer mean duration; the mean inland penetration of the sea breeze is greater under strong onshore winds than strong offshore flows (AzorinMolina and Chen, 2008). Pushpadas et al (2010) in a numerical model for the west coast of India found that in the winter period, the synoptic flow is northeasterly (offshore) and weakens the sea breeze, while during the transition period between northeast monsoon and southwest monsoon, the synoptic flow is onshore and intensifies the sea breeze.…”

Observed and simulated sea breeze characteristics over Rayong coastal area, Thailand

“…Most observational and modeling studies emphasize on general SB characterization and impacts on transport and dispersion of air pollutants. Atmospheric or meteorological modeling has also aided investigating the time-dependent vertical structure of SB in both horizontal and vertical spatial scales, and on physical processes involved (e.g., Lin et al 2001;Ding et al 2004;Srinivas et al 2006;Pushpadas et al 2010). Arritt (1992) reported that prevailing onshore synoptic winds of a few meters per second (or larger) are sufficient to suppress SB development, while it is still possible for an SB to develop under strong offshore (opposing) synoptic winds (as strong as 11 m/s).…”