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- Title
Measurements of a Dusty Density Current in the Western Sonoran Desert.
- Authors
Evan, A. T.; Porter, W.; Clemesha, R.; Kuwano, A.; Frouin, R.
- Abstract
Here we present observations of a dust storm that occurred on 22 February 2020 in the northwestern Sonoran Desert. In‐situ and remotely sensed measurements and output from numerical simulations suggest that evaporative cooling from cold frontal orographic precipitation spilling over an upwind mountain range generated a density current, with dust uplift occurring as the density current traveled over the emissive desert surface. Because the density current was laden with dust, time series of vertical profiles of aerosol backscatter and extinction from a ceilometer located 25 km downwind of the initial dust emission event show a well‐developed density current structure, including an overturning frontal head with a vertical extent of 1.2 km. Ceilometer measurements and soundings suggest a density current body depth of 400–500 m exhibiting a two‐layer structure that consisted of a positively sheared and dusty lower‐level, and a negatively sheared and pristine upper level. Kelvin‐Helmholtz instability at the top of the density current cold pool generated quasi‐regular oscillations in the height of the dust and pristine‐sky interfacial layer. Ridges and troughs in the height of this interfacial layer were coupled to maxima and minima in surface wind speed and near surface dust concentrations, respectively, with peak dust concentrations located directly under the interfacial layer ridges. These results corroborate several findings from model studies of dust emission and transport by density currents, and suggest that the internal circulation of a density current modifies the timing of dust emission and the patterns of dust concentration within the current body. Plain Language Summary: Here we discuss the case of a unique dust storm that occurred in the western end of the Sonoran Desert. Remote sensing and in‐situ measurements are used to demonstrate that the dust storm was generated by a density current. Lidar backscatter measurements during passage of this density current over a research site in the region are used to trace the path of dust laden air through the density current head and body, and reveal the internal circulation of this feature. These observational results corroborate findings from modeling studies of dust emission and transport by density currents, but also suggest a complex distribution of dust within the density current body. Key Points: Measurements of a dust storm in the western Sonoran Desert that was generated by a density current are presentedThe density current exhibits a 2‐layer internal circulation with a lower dusty layer and an upper pristine layerThese observations corroborate several findings from numerical simulations of dust emission and transport by density currents
- Subjects
SONORAN Desert; DENSITY currents; EVAPORATIVE cooling; KELVIN-Helmholtz instability; DUST storms; DESERTS; WIND speed
- Publication
Journal of Geophysical Research. Atmospheres, 2022, Vol 127, Issue 8, p1
- ISSN
2169-897X
- Publication type
Article
- DOI
10.1029/2021JD035830