Seasonal characteristics of sea breeze and thermal internal boundary layer over Indian east coast region

Characteristics of the sea breeze and thermal internal boundary layer (TIBL) during different seasons are studied using mini micropulse lidar (MPL) at Kattankulathur (12.83 degrees N, 80.04 degrees E, 45 m) and radiosonde and surface meteorological observations at Meenambakkam (13.0 degrees N, 80.06 degrees E, 16 m) during the period January 2016-June 2018 over Chennai, in the Indian east coast region. Study of the sea breeze is important because it is one of the main factors responsible for most of the convective rainfall during summer monsoon season over Chennai. The sea breeze onset occurs from morning similar to 07:00 IST to late afternoon during winter and pre-monsoon seasons whereas it occurs from mid-morning similar to 09:00 IST to late evening similar to 19:00 IST during the summer monsoon and post-monsoon seasons. The cessation of the sea breeze lies between the late evening similar to 18:00 IST and early morning similar to 04:00 IST on the next day. Sea breeze prevails for the longest (shortest) duration during pre-monsoon (summer monsoon) season. The temperature, moisture, refractivity, and aerosol profiles show double mixed layer characteristics indicating TIBL as the first layer and convective boundary layer (CBL) or residual layer (RL) as the second layer. TIBL occurs throughout the year with maximum occurrence during pre-monsoon season. It varies from 0.2 to 0.8 km (0.4-1.0 km) with peak at 0.4 km (0.6 km) over Meenambakkam (Kattankulathur). TIBL height is found to be at altitude similar to 0.54 +/- 0.16 km and 0.62 +/- 0.13 km at Meenambakkam and Kattankulathur, respectively. TIBL shows a weak seasonal variation with maximum height during winter and minimum height during summer in contrast to the seasonal variation of the CBL.

Automated summary

The study found that sea breeze in Chennai has different onset and cessation times in different seasons, while TIBL height remains relatively stable throughout the year, with the highest occurrences during the pre-monsoon season.