[1] A new planetary atmospheric numerical model, ''planetWRF,'' has been developed by modifying the Weather Research and Forecasting (WRF) model. The model has generalized map projection, multiscale, and nesting capabilities, blurring the distinction between global and mesoscale models and enabling investigation of coupling between processes on all scales, including global. The model can also be run in one, two, or three dimensions. The conversion of the dynamical core for global application by altering the map projection grid and the boundary conditions as well as conversion of the physics parameterizations and constants for planetary application are described. Validation of the global dynamical core through use of standard forcing scenarios is presented. Example results from a series of simulations for Mars, Titan, and Venus are shown to demonstrate that the model performs well for a variety of planets and operating modes (microscale, mesoscale, and global scale).

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A survey of dust devils using the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) wide‐ and narrow‐angle (WA and NA) images has been undertaken. The survey comprises two parts: (1) sampling of nine broad regions from September 1997 to July 2001 and (2) a focused seasonal monitoring of variability in the Amazonis region, an active dust devil site, from March 2001 to April 2004. For part 1, dust devils were identified in NA and WA images, and dust devil tracks were identified in NA images. Great spatial variability in dust devil occurrence is highlighted, with Amazonis Planitia being the most active region examined. Other active regions included Cimmerium, Sinai, and Solis. Numerous dust devil tracks, but very few dust devils, were observed in Casius. This may suggest dust devils here occur at local times other than that of the MGS orbit (∼2 pm). Alternatively, variations in surface properties may affect the ability of dust devils to leave visible tracks. The seasonal campaign within Amazonis shows a relatively smooth variation of dust devil activity with season, peaking in mid northern summer and falling to zero in southern spring and summer. This pattern of activity correlates well with the boundary layer maximum depth and hence the vigor of convection. Global maps of boundary layer depth and surface temperature do not predict that Amazonis should be especially active, potentially suggesting a role for mesoscale circulations. Measurement of observed dust devils yields heights of up to 8 km and widths in excess of 0.5 km.