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The METCRAX Research Project

The Meteorological Experiment in Arizona's Meteor Crater

Project Description
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Project Description

METCRAX, which stands for the Meteor Crater Experiment, is a collaborative research project sponsored by the Physical and Dynamic Meteorology Division of the National Science Foundation and participated by four institutions including University of Massachusetts-Amherst (Dr. Andreas Muschinski, PI), University of Utah (Dr. C. David Whiteman, PI), Michigan State University (Dr. Sharon Zhong, PI), and Northwest Research Associates (Dr. David C. Fritts, PI).

The overall goal of the METCRAXT project is to investigate the diurnal buildup and breakdown of basin temperature inversions or cold air pools and the associated physical and dynamical processes accounting for their evolving structure and morphology. The specific research objectives of METCRAX are twofold

to determine the physical processes that govern the evolution of the vertical temperature structure in stable boundary layers that develop in cold air pools in basins, with special emphasis on the evening formation and morning breakup periods, and
to determine the role that basin-scale seiches (atmospheric oscillations in the basin caused by wind disturbances at the basin crest) and internal waves play in transport and mixing in basin stable layers.

The center piece of the METCRAX research project is a month-long meteorological field campaign conducted in October of 2006 inside the Meteor Crater located about 35 miles east of Flagstaff off Interstate 40 in Arizona. The Meteor Crater was formed by the impact of a meteor approximately 50,000 years ago and is known to be the best preserved impact crater on earth. The Further detail on the history of the development of knowledge on the crater can be found on the Barringer Crater website.

The crater is a simply, nearly circular, small topographic basin with 1.2 km in diameter and 160 m deep. The surfaces and slopes of the crater are relatively uniform and there is no complex topography in the immediate vicinity of the crater. In this near-ideal basin, the physical processes leading to the buildup and breakdown of temperature inversions and the formation of atmospheric seiches can be studied in a very controlled manner that has only been achieved in laboratory settings without the complications introduced by more complex topography. The field study is designed to capture (a) the mean and turbulence characteristics of the down-slope and up-slope flows into and out of the crater, (b) the diurnal cycle of buildup and breakup of the cold-air pool, (c) seiches and other waves in the cold pool, and (d) the mesoscale variability of the ambient wind, which is expected to trigger seiches and waves in the basin.

During the month-long METCRAX field study, continuous measurements of mean and turbulence quantities within and above the crater were made by an array of towers instrumented at multiple levels, a radar wind profiler with RASS, and a sodar. During seven Intensive Observation Periods (IOPs) with quiescent weather conditions, tethered balloon soundings at three sites inside the crater were operated to document the vertical structure of wind and temperature in the crater every 30 minutes. The tethersonde soundings were supported by rawinsonde soundings released at the crater rim every three hours to provide atmospheric background conditions. The field observations were participated by scientists and technicians from the National Center for Atmospheric Research (NCAR) and the PIs and their graduate students.

The data sets collected from the field are being analyzed and are combined with numerical modeling to answer the following science questions:

What are the key terms in the mass, heat and moisture budgets of the basin atmosphere during a diurnal cycle? How do these compare to budgets over valleys and plains?
What roles do up- and down-slope flows on the sidewalls play in the buildup and breakup of basin inversions? How do the roles vary as the characteristics of slope flows change with evolving ambient stability within the basin?
What effect does asymmetry of solar heating within the basin have on the breakup of the inversion? How does this asymmetry affect the growth of boundary layers, the horizontal homogeneity of the stable core and the horizontal variation of subsidence (which compensates for upslope flows on the sidewalls) across the basin?
How are basin cooling and potential temperature structure affected by ambient flows above the basin and by surface radiation and energy budget factors (including dewfall) inside the basin? What role does soil heat flux and infrared back-radiation from the sidewalls play in the nocturnal cooling of the basin atmosphere?
What is the role of seiches for transport and mixing in the cold-air pool in a closed basin?
How well can the seiches be identified in the pressure, temperature, and velocity data, respectively?
What modes of seiches are excited in the Meteor Crater, and how do their structures depend on forcing and cold-pool stability?
What is the altitude dependence of the seiche characteristics, and how do they evolve during the night?
To what extent, and in what respect, do the observed seiches agree with the simulated ones?
How well do modeled and observed seiches and internal waves agree in their structures and decay rates? How well are the amplitudes of the seiches correlated with the ambient-wind energy contained in specific frequency bands?
What are the decay times of the potential and kinetic energy of the seiches?

Data

http://www.eol.ucar.edu/rtf/projects/METCRAX/

Publications

METCRAX 2006 - First Results from the Meteor Crater experiment (2,303 KB, PDF)
An observational and numerical study of a regional-scale downslope flow in northern Arizona (116 KB, PDF)
Slope flows observed during METCRAX (1,371 KB, PDF)
The development and characteristics of a cold air pool in a small, enclosed basin and its relationship with regional and large-scale forcing (229 KB, PDF)

Presentations

An observational and numerical study of a regional-scale downslope flow in northern Arizona (12,878 KB, PP SlideShow)
Slope flows observed during METCRAX (8,825 KB, PP SlideShow)
The development and characteristics of a cold air pool in a small, enclosed basin and its relationship with regional and large-scale forcing (1,114 KB, PP SlideShow)

Photos

Click on photo to enlarge

Bill Brown from NCAR conducting a training section Training	The ISFF tower at the floor of the Crater ISFF Tower	A midnight balloon launch in the cold Midnight launch	UH graduate student Craig Clements during the planning trip to the crater Craig Clements	MSU graduate student Lesley Fusina launching a rawinsonde balloon at night Night balloon launch
Planning trip to the crater in Sept. 2005 (from left, Andes, Barringer, Muschinski, Zhong, Whiteman, and Kring) September 2005	Lesley was having a great time Lesley Fusina	Hiking out of the crater Hiking out of the crater	MSU graduate student Lesley Fusina launching a balloon at sunrise Launch at sunrise	Wenqing Yao is setting up the antenna for the sounding system Wenqing Yao at tower
Hiking out the crater in the morning after a night in the crater (Photo by Sebastian Hoch) Hiking out of crater	MSU graduate student Crosby Savage in the field Crosby Savage	Looking at crater rim from a distance (Photo by Sebastian Hoch) Crater rim	Astronaut Astronaut	Sharon Zhong was getting ready to let go of the balloon Sharon at ISS
Geologist David Kring explaining interesting geological features of the crater during the planning trip Planning Trip