Variability in the surface wind direction at a coastal site of complex terrain
Variability in the standard deviation of surface wind direction (σθ), under different Pasquill stability regimes on diurnal, seasonal and interannual scales has been investigated making use of a 10-year data set collected at Visakhapatnam (17°42′ N., 82° 18′ E) during January, April, August and October for winter, pre-monsoon, monsoon and post-monsoon seasons respectively. The diurnal scale variability in σθ is more pronounced during day time than in night. The seasonal variability in σθ is only moderate around noon while relatively large fluctuations are noticed on inter-annual scale only during day time in January and August. The seasonal dispersion in σθ decreased from most unstable regime to most stable regime.