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

Abstract

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 offshore and a weakly influenced onshore 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 conditions 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 offshore case, a distinct sea breeze circulation was observed unlike in the case of onshore flow. In the presence of weak onshore 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.

Sea-breeze-initiated rainfall over the east coast of India during the Indian southwest monsoon

“…This mesoscale circulation often advances inland with a well defined frontal feature called the sea breeze front. Mini-SODAR measurements from Kalpakkam indicate typical positive vertical motion of 2.0 to 2.5 m s -1 along the sea breeze front during weak synoptic conditions (Prabha et al 2002). Frequently, this convergence zone initiates convection along the sea breeze front and produces significant rainfall along the east coast of India during the southwest monsoon.…”

A Study on the Influence of Synoptic-Scale Flows on Sea Breeze During Wintertime in the Coastal Zone Near Visakhapatnam, India

“…The reduction in the SNR is due to inhibition of large-scale motions with the onset of the sea breeze and the formation of the thermal internal boundary layer (TIBL) (Prakash et al 1992;Kunhikrishnan et al 1993;Prabha et al 2002). On this day, though the sea breeze first arrived around 10:30 IST, it is not well established until 11:30 IST (see Fig.…”

“…Over the Indian sub-continent, studies on the sea breeze circulation using Doppler sodar and tower-based measurements (Rao et al 1981;Singal et al 1986;Prakash et al 1992;Kunhikrishnan et al 1993;Gera and Saxena 1996;Prabha et al 2002). Recently, using surface-based observations over the coastal station, Visakhapatnam, Kirankumar et al (2019) highlighted the impact of background prevailing wind flow on the sea breeze characteristics such as occurrence, onset and cessation during different seasons over the site.…”

Wind Speed Profile Statistics from Acoustic Soundings at a Black Sea Coastal Site

“…In summary, it can be noted that in the literature, there are many short-term studies dedicated to the coastal boundary layer using acoustic remote sounding in different places around the world for short periods [25][26][27][28][29][30][31] and they have proved the great capabilities of the sodar measurements for the study the wind structure of the PBL. The novelty and the contribution to science of this paper consist in the statistical analyzes of sodar long-term wind speed data, which brings new information for the vertical structure of the atmosphere in coastal regions, and particularly for the Bulgarian Black Sea coast.…”