The Budget of Turbulent Kinetic Energy during Premonsoon Season over Kharagpur as Revealed by STORM Experimental Data

Turbulent kinetic energy (TKE) budget variations during thunderstorm days (TD) and nonthunderstorm days (NTD) of premonsoon seasons of 2007, 2009, and 2010 have been investigated at a tropical station Kharagpur (22°30′N, 87°20′E) using the surface layer turbulence data obtained during severe thunderstorms-observations and regional modeling (STORM) experiment. Significant variations in the contributions of the TKE budget parameters with respect to stability are observed on these contrasting days of weather activity. In highly unstable conditions, smaller dissipation rates are seen on TD compared to NTD, while approaching near neutral conditions, higher dissipation rates are found in TD. New relationships between TKE dissipation rates with respect to atmospheric stability are proposed at Kharagpur for TD and NTD. 1. Introduction Evolution of turbulence in atmospheric surface layer (ASL) assumes special importance, as it plays major role in the transportation of heat and moisture from near the surface to higher levels in the atmosphere. Turbulent kinetic energy (TKE), which is a measure of turbulence in the atmosphere, is directly related to the transport of momentum, heat, and moisture through the boundary layer [1]. Thus, understanding the variation of the individual budget components is crucial for energy exchange mechanism from atmospheric surface layer to upper atmosphere and vice versa. TKE budget has been studied during various field campaigns based on Monin-Obukhov similarity theory (MOST) [2–6]. TKE budget equation is still an uncertain relation in the quantitative case and is commonly used to parameterize turbulent properties of the surface layer in atmospheric models of larger scale [7]. TKE budget associates the local storage of turbulence to the shear production, buoyancy production, dissipation, and the transport processes and has numerous applications in both empirical and computational modeling in boundary-layer meteorology [8–10]. Study of TKE budget under unstable conditions and convective conditions is important for understanding the timely response of ASL. It was found in [11] that in the unstable surface layer, all terms in the TKE budget are considerable, and TKE generated through buoyancy forces is transported out of the layer, while the dissipation rate can be regarded as an approximation of the sum of mechanical production and the residual, with the unmeasured pressure term. Results at different sites about TKE budget and dissipation are emphasizing the importance of various TKE terms during convective situations and the necessity