Atmospheric surface layer responses to the extreme lightning day in plateau region in India

Abstract

This paper discusses the observations of the atmospheric surface layer (ASL) parameters during the lightning event. During this event behaviour of surface layer parameters has been observed. Other derived parameters like Monin–Obukhov stability parameter (z/L), turbulent kinetic energy (TKE), momentum flux (MF) and sensible heat flux (SHF) have also been considered during this stochastic phenomenon. Characteristics of these surface layer parameters have been analysed during lightning period and compared with the clear weather day. During the peak period of the lightning, the incoming solar irradiance was reduced by one third of its normal value, resulting in an air-temperature decrement near the surface in the range of 4°C to 6°C. In addition to that a significant reduction in energy exchanges between surface and lower lying atmosphere (viz. TKE, MF and SHF), has also been observed. The rate of instantaneous decay in solar irradiance and SHF from the first strike to its peak strike time was larger than that seen during clear day hours. The normalized standard deviations of wind components during clear day were studied using Monin–Obukhov similarity theory (MOST) and the results have been compared with earlier studies reported in the literature.