Brian Jackson edited As_another_recent_example_citet__.tex  over 8 years ago

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As another recent example, \citet{Jackson_2015} conducted a terrestrial survey at El Dorado Playa in Nevada, deploying several pressure loggers that collected data over the course of two years. With more than 250 million time-series data points collected, they applied an automated detection scheme that involved smoothing the data stream over 1,000-s windows and searching for statistically significant outlier points. This scheme recovered more than 1,600 putative dust devil pressure dips. Figure \ref{fig:Jackson_data} shows a scatter plot of their reported detections (note the change in units from Pa to hPa for the pressures). As in \citet{Jackson_2015}, we masked out detections with large $\Gamma_{\rm obs}^\prime$ and small $P_{\rm obs}$ (called ``unexpectedly shallow'' in \citet{Jackson_2015}), giving rise to the absence of points in the lower right-hand corner of the bottom left panel. As for the previous dataset, we employed a Gaussian kernel density estimate with a bandwidth of 1 to suppress spurious structure (somewhat smaller bandwidths do not qualitatively change the results).   Similar features appear for this dataset as for the previous dataset, for the densities of both observed and actual parameters, although the locations of features are shifted. Again, a sharp decline in the distribution of $\Gamma_{\rm act}^\prime$ coincides with a peak in the $\Gamma_{\rm obs}^\prime$ density, but this time around $\Gamma_{\rm act}^\prime = 10^{1.6} =$ 40 s. With a typical speed of 5 m/s, $\Gamma_{\rm obs}^\prime = $ 40 s corresponds to a physical width of 200 m, much larger than the typical dust devil width observed on El Dorado Playa \citep{Balme_2012}. This result either indicates the detection of unusually large/slow-moving dust devils or (more likely) some of the widest signals reported in \citet{Jackson_2015} are pressure dips unrelated to dust devils, an issue discussed at length in that study. In any case, if many of the detections can be attributed to dust devil passages, the observed $\Gamma_{\rm obs}$-distribution points to population of much more narrow dust devils. Again, as for the previous dataset, the peak near $P_{\rm obs}$ is likely due, at least in part, to recovery biases for shallow devils. However, we would also expect the miss distance effect to shift the peak in the $P_{\rm act}$ distribution near $10^0$ hPa = 1 hPa to $10^{-0.6}$ hPa = 0.25 hPa in the $P_{\rm obs}$ distribution: $P_{\rm min} = 0.1$ hPa and $\langle b/\Gamma_{\rm act} \range = \frac{1}{3} \sqrt{1\ {\rm hPa}/0.1\ {\rm hPa} hPa}}  = 1$, so a peak at $P_{\rm act} = 1$ hPa should be shifted to $P_{\rm obs} = 1\ {\rm hPa}/\left( 1 + (2 \times 1)^2 \right) = 0.2$ hPa.