Variations in the Daily Cycle of Winds Over the Galápagos

Leslie M. Hartten
University of Colorado/Cooperative Institute for Research in Environmental Sciences (CIRES) and NOAA/Aeronomy Laboratory, Boulder CO 80309-0216 USA
[lhartten@al.noaa.gov]

Pauline A. Datulayta
University of Colorado/Summer Multicultural Access to Research Training (SMART) program and Queens College, Flushing NY 11367 USA
[pdatula1@forbin.qc.edu]

The seasonal and interannual variability of the daily cycle of winds over Isla San Cristóbal has been studied using four years’ worth of 915-MHz wind profiler data. The pronounced daily cycle observed by the profiler is inconsistent with a land/sea breeze. The zonal semidiurnal atmospheric tide is evident in the data, especially above 800 m, but not the diurnal tide. The diurnal cycle is predominantly meridional and deep during El Niño events, warm seasons, and the 1997 cold season, which occurred during a strong El Niño. During La Niña events and the 1998 and 1999 cold seasons, the diurnal cycle is meridional below 500 m and zonal above that. The vertical decoupling during periods with colder SSTs may be due to enhanced stability of the lower atmosphere. This low-level meridional diurnal cycle does not appear to be correlated with the daily cycle of convection in the ITCZ.