Thursday, 27 January 2011: 2:30 PM
604 (Washington State Convention Center)
Jerry Allwine and Chris Doran have studied the meteorology of valleys and basins, concentrating on the related evolution of stable boundary layers and downslope flows, with a special emphasis on field studies and data analysis. In the present talk, we take an approach that Jerry and Chris have previously used - combining data collection and analysis, reasoning, and simple analytical models - to investigate the peculiar, but interesting, relationship between downslope flows on two scales and the evolution of the nighttime stable boundary layer within Arizona's Meteor Crater Basin. The data show the complications that occur in real topography and the power of meteorological data analysis to gain understanding of a previously undocumented, but ultimately sensible phenomenon that illustrates the broad range of meteorological behaviors that can be expected in complex terrain.
On clear, synoptically undisturbed nights a mesoscale (~ 50 km length-scale) southeasterly cold-air drainage flow on the tilted plain outside the Meteor Crater impinges on the crater topography and lifts air to the crater rim that is cold enough to intrude into the crater basin. The cold air intrusion comes down the upwind inner sidewall of the basin and descends until reaching its level of buoyancy equilibrium. The shallow cold-air intrusion coming down the inner sidewall of the basin differs from typical downslope flows in that it benefits from a continuous source of relatively cold air at the crater rim. Detrainment of cold air from this downslope flow increases nighttime cooling inside the basin and destabilizes the nighttime temperature profiles inside the crater basin. The destabilization produces odd isothermal profiles through most of the basin depth, a peculiar feature not seen before in other basins of this approximate size.
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