STUDIES ON REFRACTIVITY STRUCTURE CONSTANT, EDDY DISSIPATION RATE, AND MOMENTUM FLUX AT A TROPICAL LATITUDE

VHF and UHF Doppler radars provide a unique database to estimate the r efractivity structure constant C-n(2), eddy dissipation rate epsilon, and vertical flux of horizontal momentum. Using the data collected fro m the Indian MST radar, these parameters are studied at a tropical lat itude. The refractivity turbulence structure constant is estimated fro m the backscattered power of the received echoes. C-n(2)(radar) and C- n(2)(model), derived from radiosonde observations, are compared, and a fairly good agreement is seen. Diurnal and seasonal variations of C-n (2) are also presented. The eddy dissipation rate is estimated from th e radar echoes employing the power and spectral width methods. A fairl y good agreement is seen between the two methods. Values of epsilon ar e found to vary from 10(-6) to 10(-3) m(2) s(-3) in a height range of 4-19 km. C-n(2) and epsilon are observed to be minimum during a modera te jet stream wind of 50-60 m s(-1). Vertical flux of horizonal moment um is computed using the symmetrical two-beam method. Significant flux es of westward and northward momentum are observed, and the values lie in the range of -1 to +1 m(2) s(-2). The implied accelerations are al so estimated. The results presented are largely consistent with the re sults available in the literature.