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

Abstract

This paper presents the diurnal and seasonal variation of Turbulence Kinetic Energy (TKE) dissipation rate (ε) in the Atmospheric Boundary-Layer (ABL) over a tropical station, Gadanki (13.5° N, 79.2° E) in India. Doppler spectral width measurements made by Lower Atmospheric Wind Profiler (LAWP) operating at 1357 MHz are utilized to estimate ε 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 ε. It is found that in the lower tropospheric height region ε is in the range from 10−5.0 to 10−1.0 m2 s−3. ε showed significant diurnal variation in the boundary-layer. The larger values of ε, 10–2.7 m2 s−3, are noted to be associated with the Convective Boundary-Layer (CBL). The parameter ε is also showing significant seasonal variation. In summer and monsoon seasons the boundary-layer depths are observed up to a height of 4.0 km while the same are confined to below 2.0 km in post-monsoon and winter seasons.