Thermal internal boundary layer characteristics at a tropical coastal site as observed by a mini-SODAR under varying synoptic conditions

Thara V. Prabha, R. Venkatesan, Erich Mursch-Radlgruber, G. Rengarajan, N. Jayanthi
2002 Proceedings of the Indian Academy of Sciences, Earth and Planetary Sciences  
Atmospheric boundary layer observations are conducted at a coastal site during a transition phase from winter to summer season over the Indian peninsula. Thermal Internal Boundary Layer (TIBL) characteristics in presence of an off-shore and a weakly influenced on-shore synoptic wind are examined with the help of measurements carried out with a mini-SODAR (SOund Detection And Ranging), tethered balloon, and tower-based micrometeorological measurements. Influence of the changing synoptic scale
more » ... ditions on turbulent characteristics of TIBL is discussed. Mini-SODAR data showed the development and decay of sea and land breeze. It is seen that the characteristics of TIBL over the coastal land after sea breeze onset are similar to that of a shallow convective boundary layer (CBL) commonly found over plain land. Inside the TIBL, a maximum wind speed was noted close to the surface due to the penetration of sea breeze. In the off-shore case, a distinct sea breeze circulation was observed unlike in the case of on-shore flow. In the presence of weak on-shore case, a 'minor sea' breeze is noted before the establishment of sea breeze and a reduction in the momentum fluxes gives rise to decrease in the turbulence intensity. Updraft in the sea breeze front was stronger during weak synoptic conditions. Influence of synoptic changes on the sea breeze-land breeze circulation such as onset, strength and duration of the sea-land breeze are also examined. * This work was done while the first author was a visiting scientist at IGCAR, Kalpakkam, India. Several researchers have noted that direction and strength of the synoptic flow influence the structure and evolution of sea breeze (Estoque 1962; Pielke 1974; Arritt 1993) . The off-shore/on-shore wind velocity of the ambient flow influences inland penetration of the sea breeze. In the laboratory experiments conducted by Simpson (Simpson 1987) it was noted that the nature of prevailing gradient flow affects the development of sea breeze. Several theoretical studies (Pearson et al 1983; Garratt et al 1990; Bechtold et al 1991) have also been reported investigating the effects of large-
doi:10.1007/bf02702223 fatcat:kafvzisl3vax3d5fxaxjtq3tle