Decay of Turbulence during Evening Transition at the Kempegowda International Airport, Bengaluru, India

Evening Transition (ET) over Kempegowda International Airport (77.70◦ E, 13.20◦ N) is investigated over 2
seasons to calculate robust statistics of decay of Turbulent Kinetic Energy (TKE) in the Atmospheric Boundary
Layer (ABL). Although previous research on TKE decay during ET has largely relied on Large Eddy Simulations
(LES) and analytical models to determine decay rates of volume-averaged TKE, our study takes a more granular
approach.
We use two remote sensing instruments (Radiometer Physics HATPRO Radiometer and Vaisala Windcube
100S) to measure temperature, humidity, and wind components at multiple levels within the ABL. In addition,
ground instruments like temperature, relative humidity sensors, ground heat flux sensors and radiation sensors
provide near-surface data about temperature, moisture and heat fluxes. Together, these instruments allow us
to track local decay of TKE at various heights within the ABL.
We then apply functional fits for various time intervals during the decay period, generating vertical profiles
of the TKE decay exponents across the ABL. These profiles provide valuable insights into the relative importance
of surface-driven vs. ABL top-driven decay of TKE. Moreover, we observe that separate intervals of time in the
ET might have separate functional forms for the decay of TKE, instead of a commonly used single power-law
fit. The entire investigation enhances our understanding of TKE decay during the ET and could be
helpful for real-life applications such as understanding nighttime pollution dispersal or forecasting condensation
phenomenon like fog or mist. around Bengaluru city.