Investigation of non-Gaussian Doppler spectra observed by weather radar in a tornadic supercell

Tian You Yu, Ricardo Reinoso Rondinel, Robert D. Palmer

Research output: Contribution to journalArticleScientificpeer-review

9 Citations (Scopus)


Radar Doppler spectra that deviate from a Gaussian shape were observed from a tornadic supercell on 10 May 2003, exhibiting features such as a dual peak, flat top, and wide skirt in the nontornadic region. Motivated by these observations, a spectral model of a mixture of two Gaussian components, each defined by its three spectral moments, is introduced to characterize different degrees of deviation from Gaussian shape. In the standard autocovariance method, a Gaussian spectrum is assumed and biases in velocity and spectrum width estimates may result if this assumption is violated. The impact of non-Gaussian weather spectra on these biases is formulated and quantified in theory and, consequently, verified using four experiments of numerical simulations. Those non-Gaussian spectra from the south region of the supercell are further examined and a nonlinear fitting algorithm is proposed to estimate the six spectral moments and compare to those obtained from the autocovariance method. It is shown that the dual-Gaussian model can better represent observed spectra for those cases. The authors' analysis suggests that vertical shear may be responsible for the flat-top or the dual-peak spectra in the lower elevation of 0.5° and their transition to the single-peak and wide-skirt spectra in the next elevation scan of 1.5°.

Original languageEnglish
Pages (from-to)444-461
Number of pages18
JournalJournal of Atmospheric and Oceanic Technology
Issue number3
Publication statusPublished - 2009
Externally publishedYes

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