The VOCALS Program - Ocean Dynamics, Stratocumulus and Climate in the Southeast Pacific

VOCALS (the VAMOS Ocean-Cloud-Atmosphere-Land Study) is an international CLIVAR program studying feedbacks between upper-ocean dynamics, SST, stratocumulus and climate in the southeast Pacific, involving researchers from the U.S., Chile, and other South American countries. We present a summary of ongoing research and future VOCALS plans, including a 'radiator fin' (RF) field experiment for October 2007, with the goal of attracting collaboration from interested researchers in the air-sea interaction and climate modeling communities.

The overall goal of VOCALS is to develop and promote scientific activities leading to improved understanding, model simulations, and predictions of the southeastern Pacific coupled ocean-atmosphere-land system, on diurnal to interannual timescales. The two leading scientific concerns are (1) the physical processes affecting the radiative and microphysical characteristics of the persistent stratocumulus clouds of this region, and (2) the ocean budgets of heat and other constituents, and how they determine the sea-surface temperature (SST) throughout this region.

VOCALS activities began in 2003 with enhanced instrumentation, including an U. Chile automated weather station on tiny San Felix Island (27S 81W) and NOAA-ETL cloud-remote sensing and aerosol measurements on annual maintenance cruises to a WHOI IMET flux-reference buoy (20S 85W). These measurements, together with TAO buoys and the 2001 EPIC stratocumulus cruise, are providing climatological context for understanding air-sea interaction in this region. Upper-ocean heat content budgets at the WHOI buoy suggest that oceanic Rossby waves or eddies are a substantial drain of upper-ocean heat content, even far offshore of the coastal upwelling regime. The cruises, satellite analyses, and San Felix observations testify to the importance of aerosol-cloud-drizzle interactions and the strong diurnal cycle of cloud in this region. The planned VOCALS-RF field program will be focussed on better understanding these issues using in-situ observations from an aircraft, at least one ship, and mesoscale upper-ocean profiling, and will be coordinated with a coastal zone intensive observing program.