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\section*{Background}  Dust devils are small-scale (few to many tens of meters) low-pressure vortices rendered visible by lofted dust. They usually occur in arid climates on the Earth and ubiquitously on Mars, where they likely may  dominate the supply of atmospheric dust and influence climate. Martian dust devils have been studied with orbiting and landed spacecraft and were first identified on Mars using images from the Viking Orbiter \citep{Thomas_1985}. A long series of subsequent dust devil studies have followed, either through direct imaging or by identification of their tracks on Mars' dusty surface \citep[cf.][]{Balme_2006}. Meteorological sensors have also provided evidence for Martian dust devils passing near landed craft, either viatheir pressure signals \citep{Ellehoj_2010} or  obscuration of the Sun by the dust column \citep{Zorzano_2013}. \citep{Zorzano_2013} or their pressure signals \citep{Ellehoj_2010}.  By contrast, studies Studies  of terrestrial dust devils frequently involve in-person monitoring of field sites, and dust devils are visually surveyed \citep{Pathare_2010} or directly sampled \citep{Balme_2003}. Recently, terrestrial As noted in \citet{Lorenz_2009}, in-person visual  surveys similar are likely  to Martian dust devil surveys have been conducted using in-situ single barometers \citep{Lorenz_2012, Lorenz_2014, Jackson_2015} and photovoltaic sensors \citep{Lorenz_2015}. These sensor-based terrestrial surveys have the advantage be biased toward detection  of being directly analogous to Martian larger, more easily seen devils. Such  surveys and are highly cost-effective compared would also fail  to the in-person surveys. recover dustless vortices \citep{Lorenz_2015}.  All these surveys, however, suffer from observational biases that skew the statistical properties inferred for the underlying Recently, terrestrial surveys similar to Martian  dust devilpopulation. For example, as noted in \citet{Lorenz_2009}, in-person visual  surveys are likely to be biased toward detection of larger, more easily seen devils. On the other hand, single-sensor barometer have been conducted using in-situ single barometers \citep{Lorenz_2012, Lorenz_2014, Jackson_2015} and photovoltaic sensors \citep{Lorenz_2015}. These sensor-based terrestrial  surveyssuffer from a ``miss distance'' bias: a fixed barometric sensor is more likely to  havea more distant encounter than a close encounter with a dust devil. Since the pressure perturbation associated with a devil falls off with distance,  the deepest point in the observed pressure profile will almost always be less than the actual pressure well at the devil's center. The observed shape advantage  of the profile will be distorted as well. These biases are intrinsic being directly analogous  to the detection methods, Martian surveys  and additional biases can influence the inferred statistical properties. For instance, noise in the pressure time series from a barometer may make more difficult detection of a dust devils with smaller pressure perturbations, depending on are highly cost-effective compared to  the exact detection scheme. in-person surveys.  In this kind of survey, one or more barometric sensors these single-barometer surveys, a sensor is  deployed in-situ record a pressure time series at a sampling rate $\lesssim 1$ s. As a  low-pressure convective vortex, the nearby passage of  a dust devil has an actual will register as  pressure depth $P_{\rm act}$ at its center measured dip discernible  against some known a  background level and ambient (but not necessarily constant) pressure. Figure \ref{fig:conditioning_detection_b_inset} from \citet{Jackson_2015} shows  a radial profile $P(r)$ resembling time-series with  a inverted Lorentz function typical dust devil signal. However, as  with visual surveys, single-sensor barometer surveys suffer from biases as well, primarily from the ``miss distance'' effect:  a full-width half-max $\Gamma_{\rm act}$: $P(r) = \dfrac{P_{\rm act}}{1 + \left( 2r/\Gamma_{\rm act} \right)^2 }$. Dust devils are usually carried by fixed barometric sensor is more likely to have a more distant than closer encounter with a dust devil. Since  the background wind pressure perturbation associated  with a velocity $\upsilon$. Figure \ref{fig:conditioning_detection_b_inset} devil falls off with distance, the deepest point in the observed pressure profile will almost always be less than the actual pressure well at the devil's center. The observed shape of the profile will be distorted as well. These biases are intrinsic to the detection methods, and additional biases can influence the inferred statistical properties. For instance, noise in the pressure time series  from\citet{Jackson_2015} shows  a typical profile. barometer may make more difficult detection of a dust devils with smaller pressure perturbations, depending on the exact detection scheme.  %\citet{Lorenz_2014} investigated biases inherent The dust-lifting capacity of dust devils seems  to single barometer surveys using a phenomenological Monte-Carlo model depend sensitively on their structures, in particular on the pressure wells at their centers \citep{Neakrase_2006}, so the dust supply from dust devils on both planets may be dominated by the seldom observed larger devils. Thus, it is particularly important to study the underlying distribution of dust devil properties. Thus, elucidating the origin, evolution, and population statistics of dust devils is critical for understanding important terrestrial and Martian atmospheric properties and  for in-situ exploration of Mars --  dust devils advected through might pose  a virtual arena. hazard for human exploration but have also apparently lengthened the operational lifetime of the Spirit rover.  %They have been observed to persist from minutes to hours and can travel kilometers, often carried by the ambient wind [Lorenz, 2013a]. OnEarth, they are observed in arid locations primarily, where the ground is usually dry enough to provide a ready supply of dust [e.g., Balme and Greeley, 2006]. On Mars, they have been observed ubiquitously,  both from the ground [Metzger et al., 1999] Mars  and from orbiting spacecraft [Cantor et al., 2006]. On both planets, the Earth,  dust devils contribute to the atmospheric aerosol content, sometimes increasing the dust content over the U.S. Southwest by more than an order of magnitude [Renno et al., 2004]. On Mars, dust devils may be the magnitude, they  primary source for atmospheric dust, which plays a role in the radiative balance of the Martian atmosphere and, therefore, on the planet's meteorology [Basu et al., 2004]. Dust devils also seem to have lengthened the operating lifetime of Martian rovers by frequently cleaning their solar panels (http://mars.jpl.nasa.gov/mer/mission/status_opportunityAll.html#sol3603). Since the dust supply from dust devils on both planets may be dominated by the seldom observed larger devils, it is particularly important to study the underlying distribution of dust devils, rather than focusing on the typical devil. Thus, elucidating the origin, evolution, and population statistics of dust devils is critical for understanding important terrestrial and Martian atmospheric properties and for in situ exploration of Mars. %While the pressure dips associated with dust devils have been recorded on Earth [e.g., Wyett, 1954; Lambeth, 1966; Sinclair, 1973], they are actually more systematically documented in studies of dust devils on Mars (e.g., by Mars Pathfinder: Murphy and Nelli, 2002; and by the Phoenix mission: Ellehoj et al., 2010), where landers have recorded meteorological parameters over long periods with a high enough cadence to detect small vortical structures. Most terrestrial meteorological records have cadence too low (canonically, 15 min) to record dust devils, for which a sampling rate of ∼1 Hz or better is typically required. 
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