Hydraulic Analysis and Cold-Air Pool Interaction of the Raco Gap Wind

Author:

Muñoz Ricardo C.1ORCID,Armi Laurence2

Affiliation:

1. a Department of Geophysics, University of Chile, Santiago, Chile

2. b Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, La Jolla, California

Abstract

Abstract Raco is a local wind occurring in central Chile where the Maipo River Canyon exits into the Santiago valley. The intensification of the easterly down-canyon flow starts at any time during some cold season nights, accompanied by increases in temperature and drops in humidity. The hypothesis of the raco being a gap wind controlled by the narrowest section in the 12-km canyon exit corridor is tested with data from two events in July 2018 and July 2019. The data are analyzed in the framework of hydraulic theory, and a subcritical-to-supercritical transition is documented to occur at the narrows of the gap where the Froude number is close to unity, confirmed by radiosondes launched in the narrows in 2019. For the raco flow, the sum of potential and kinetic energy is conserved upstream of the narrows, while the acceleration occurring farther downstream loses a large fraction of energy to frictional dissipation. The raco events occur under the influence of regional subsidence, but a differential nocturnal warming of the in-canyon air mass is responsible for a pressure gradient driving the raco. In the 2019 case, a ceilometer mounted on an instrumented pickup truck documented the structure and movement of the interface between the raco air and the cold-air pool (CAP) existing over the valley to the west. Together with a radiosonde launched near the CAP–raco surface front, the observations reveal the intense shear-driven mixing taking place at the interface and the factors supporting the establishment of a stationary front.

Funder

ANID-Fondecyt

Publisher

American Meteorological Society

Reference49 articles.

1. The hydraulics of two flowing layers with different densities;Armi, L.,1986

2. Coupling between chemical and meteorological processes under persistent cold-air pool conditions: Evolution of wintertime PM2.5 pollution events and N2O5 observations in Utah’s Salt Lake Valley;Baasandorj, M.,2017

3. Conserved variable analysis of the convective boundary-layer thermodynamic structure over the tropical oceans;Betts, A. K.,1987

4. High-resolution observations and numerical simulations of easterly gap flow through the Strait of Juan de Fuca on 9–10 December 1995;Colle, B. A.,2000

5. Diagnostics of hydraulic jump and gap flow in stratified flows over topography;Drobinski, P.,2001

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