Turbulent kinetic energy in the atmospheric surface layer during the summer monsoon

Abstract

The turbulent kinetic energy (TKE) in the atmospheric surface layer (ASL) gives a measure of the intensity of turbulence that could be altered or brought about by mechanical generation, by thermal generation, through vertical transport into or away, and through dissipation. TKE is mainly responsible for the transportation of pollutants suspended in the air. In this paper, TKE evolution in the ASL is studied for Kharagpur (22.20° N, 87.18° E) during the summer monsoon by making use of data from a 30 m micrometeorological tower set up as part of the Monsoon Trough Boundary Layer Experiment (MONTBLEX). Under steady state and homogeneous conditions the various terms in the TKE equation are studied for active and non-active phases of the monsoon in 1990. Their day-to-day variations and the budgets are studied at the 8 m and 15 m levels. The study reveals strong day-to-day variation and significant vertical variations within the ASL. Despite being a tropical station, the buoyancy term is much less than the contribution by mechanical generation ostensibly due to the monsoon. There are also differences between active and non-active phases of the monsoon. Mechanical generation by wind shear has been found to be the dominating production term, while dissipation dominates the magnitude of all other terms.