92nd American Meteorological Society Annual Meeting (January 22-26, 2012)

Monday, 23 January 2012: 4:30 PM
Assessing Intraseasonal to Interannual Variability of Upwelling-Favorable Coastal Winds off Central Chile
Room 338 (New Orleans Convention Center )
David A. Rahn, University of Chile, Santiago, Chile

Over the southeast Pacific a surface anticyclone is present most of the year and is associated with southerly alongshore wind along the central coast of Chile. A coastal low-level jet often develops and the wind speed is mostly controlled by the meridional pressure gradient. While the low-level jet is regarded as a mesoscale feature forced by an interaction between synoptic conditions and coastal topography, it is also known that regional surface pressure anomalies are associated with the oscillations of ENSO, AAO, and MJO.

The connection between the coastal wind and these regional influences, which has been proposed but not directly shown, is directly quantified using 30 years of high resolution (~0.3) CFSR reanalysis, which resolves coastal features better than previous, coarser analyses. For each index, the composited 10-m meridional wind reveals significant (95% confidence level) anomalies of 0.5-1.5 m/s. For each regional oscillation alongshore wind anomalies correlate well to the change of meridional surface pressure gradient. While not completely additive, there is constructive and deconstructive interference between the three indices.

Supplementary URL: http://www.dgf.uchile.cl/~darahn