Showing papers on "Secondary circulation published in 1987"

Inner Core Structure of Hurricane Alicia from Airborne Doppler Radar Observations

Abstract: Airborne Doppler radar measurements are used to determine the horizontal winds, vertical air motions, radar reflectivity and hydrometer fallspeeds over much of the inner-core region (within 40 km of the eye) of Hurricane Alicia (1983). The reconstructed flow field is more complete and detailed than any obtained previously. The data show both the primary (azimuthal) and secondary (radial-height) circulations. The primary circulation was characterized by an outward sloping maximum of tangential wind. The secondary circulation was characterized by a deep layer of radial inflow in the lower troposphere and a layer of intense outflow above 10 km altitude. The rising branch of the secondary circulation was located in the eyewall and sloped radially outward. Discrete convective-scale bubbles of more intense upward motion were superimposed on this mean rising current, and convective-scale downdrafts were located throughout and below the core of maximum precipitation in the eyewall. Precipitation particle...

Systematic forcing of large-scale geophysical flows by eddy-topography interaction

Abstract: The interaction of eddies with variations in topography, together with a tendency for large-scale wave propagation, generates a systematic stress which acts upon large-scale mean flows. This stress resists the midlatitude tropospheric westerlies, resists the oceanic Antarctic Circumpolar Current, and may be a dominant mechanism in driving coastal undercurrents. Associated secondary circulation provides a systematic upwelling in coastal oceans, pumping deeper water onto continental shelf areas. The derivation rests in turbulence closure theory and is supported by numerical experiments.

An MHD model for the complete open magnetotail boundary

Abstract: In the Coroniti-Kennel MHD model for the open magnetotail boundary, a standing slow-mode expansion fan turns the magnetosheath flow into the plasma mantle and converts the magnetosheath field into the tail lobe field. The expansion fan-plasma mantle is also called the high-latitude boundary layer. The Coroniti-Kennel model applies to the noon-midnight meridian plane and the case of a purely southward interplanetary magnetic field (IMF). This paper (1) quantitatively tests and verifies the model, and (2) describes how the relatively thick and rapidly propagating high-latitude expansion fan automatically thins and slows at lower latitudes. It tapers down to a thin, nonpropagating tangential discontinuity representing the low-latitude boundary layer on closed field lines. Thus the model shows how the dawn-to-dusk current sheet that bisects the tail horizontally can return to dawn over the tail's back uninterruptedly across a seamless juncture between the high- and low-latitude boundary layers. Other important properties emerge from the complete boundary mode. A rotational discontinuity preconditions the field to pass through the slow mode wave. It induces a secondary circulation in the cross-sectional plane. This circulation sweeps plasma sheet plasma dawnward and duskward away from the tail's midplane and draws it up the tail's flanks, possibly accounting formore » the plasma sheet's butterfly-shaped cross section. The along-the-tail currents flowing on the rotational discontinuity have the same IMF B/sub y/ dependence as the cusp currents, which they might feed. The B/sub y/ distortion of the secondary circulation tends to rotate the plasma sheet about the tail axis to face the IMF. copyright American Geophysical Union 1987« less