Brian Jackson edited section_Formulating_the_Signal_Distortions__.tex  over 8 years ago

Commit id: 360c0e33b81c77d1777b668ef28b09c3de885ee3

deletions | additions      

       

\item Each dust devil pressure profile has a well-defined, static profile, which follows a Lorentzian: $P(r) = \dfrac{P_{\rm act}}{1 + \left( 2r/\Gamma_{\rm act} \right)^2 }$. Here $r$ is the distance from the devil center, $P_{\rm act}$ the actual pressure depth at the devil's center, and $\Gamma_{\rm act}$ the profile full-width at half-max. Alternative profiles have been suggested, including Burgers-Rott or Vatistas profiles that might provide more accurate physical description \citep{Lorenz_2014}, but using a different profile would not modify our results substantially.   \item The dust devil center is carried by the ambient wind field at a velocity $\upsilon$, which is constant in magnitude and direction. In reality, the ambient wind field carrying a devil can be complex, even causing multiple encounters between devil and sensor and consequently more complex pressure signals \citep{Lorenz_2013}. A devil whose center passes directly over the sensor will register a pressure dip with a full-width at half-max in time $\Gamma^\prime_{\rm act} = \Gamma_{\rm act}/\upsilon$, so that theobserved  profile width observed  in timeobserved  is $\Gamma^\prime_{\rm obs}$. \item A dust devil appears and disappears instantaneously, traveling a distance $\upsilon \tau$ over its lifetime $\tau$. As pointed out by \citet{Lorenz_2013}, $\tau$ seems to depend on dust devil diameter $D$ as $\tau = 40\ {\rm s}\ \left( D/{\rm m} \right)^{2/3}$, with diameter in meters. We assume $D = \Gamma_{\rm act}$ \cite{Vatistas_1991}.