Anticyclonic precession of a plume in a rotating environment

Motivated by potential effects of the Earth’s rotation on the Deepwater Horizon oil plume, we conducted laboratory experiments on salt-water point plumes in a homogeneous rotating environment across a wide range of Rossby numbers 0.02 < Ro < 1.3. We report a striking physical instability in the plume dynamics near the source: after approximately one rotation period, the plume tilts laterally and starts to precess anticyclonically. The mean precession frequency ω scales linearly with the rotation rate Ω as ω ≈ 0.4 Ω. We find no evidence of a critical Rossby number above which precession ceases. We infer that a conventionally defined Rossby number is not an appropriate parameter when the plume is maintained over a long time: provided Ω ≠ 0, rotation is always important to the dynamics. This indicates that precession may occur in persistent oceanic or atmospheric plumes even at low latitudes

Resonances in an evolving hole in the swash zone

Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of American Society of Civil Engineers for personal use, not for redistribution. The definitive version was published in Journal of Waterway, Port, Coastal, and Ocean Engineering 138 (2012): 299–302, doi:10.1061/(ASCE)WW.1943-5460.0000136.Water oscillations observed in a 10-m diameter, 2-m deep hole excavated on the foreshore just above the low-tide line on an ocean beach are consistent with theory. When swashes first filled the initially circular hole on the rising tide, the dominant mode observed in the cross-shore velocity was consistent with a zero-order Bessel function solution (sloshing back and forth). As the tide rose and swash transported sediment, the hole diameter decreased, the water depth inside the hole remained approximately constant, and the frequency of the sloshing mode increased according to theory. About an hour after the swashes first reached the hole, it had evolved from a closed circle to a semi-circle, open to the ocean. When the hole was nearly semi-circular, the observed cross-shore velocity had two spectral peaks, one associated with the sloshing of a closed circle, the other associated with a quarter-wavelength mode in an open semi-circle, both consistent with theory. As the hole evolved further toward a fully semi-circular shape, the circular sloshing mode decreased, while the quarter-wavelength mode became dominant.The Office of Naval Research, a National Security Science and Engineering Faculty Fellowship, a National Science Foundation Career award, and a National Defense Science and Engineering Graduate Fellowship provided support

Categorical Imperatives: The Interaction of Latino and Racial Identification

Most large data sets solicit "ethnic" identification and "racial" identification in separate questions. We test the relative salience of these two identifications by exploring whether individuals who chose both a Latino "ethnic" label and a "racial" label on separate survey questions still chose both of these labels when they were given a single combined question about their racial and ethnic origins. Copyright (c) 2006 Southwestern Social Science Association.