Diurnal and seasonal variability of TKE dissipation rate in the ABL over a tropical station using UHF wind profiler

摘要

This paper presents the diurnal and seasonal variation of Turbulence Kinetic Energy (TKE) dissipation rate (epsilon) in the Atmospheric Boundary-Layer (ABL) over a tropical station, Gadanki (13.5 degrees N, 79.2 degrees E) in India. Doppler spectral width measurements made by Lower Atmospheric Wind Profiler (LAWP) operating at 1357 MHz are utilized to estimate epsilon in the height region of 0.5-4.0 km on clear air days. Various non-turbulent spectral broadenings are calculated and separated out from the observed spectral width before estimating epsilon. It is found that in the lower tropospheric height region epsilon is in the range from 10(-5.0) to 10(-1.0) m(2) s(-3). epsilon showed significant diurnal variation in the boundary-layer. The larger values of epsilon, 10(-2.7) m(2) s(-3), are noted to be associated with the Convective Boundary-Layer (CBL). The parameter epsilon is also showing significant seasonal variation. In summer and monsoon seasons the boundary-layer depths are observed up to a height of similar to 4.0 km while the same are confined to below 2.0 km in post-monsoon and winter seasons. (c) 2006 Elsevier Ltd. All rights reserved.