Enhanced TAO Monitoring of
Ocean-Atmosphere Interactions in the Cold
Tongue / ITCZ Complex
Dr. Meghan F. Cronin and Dr. Michael J. McPhaden
NOAA / Pacific Marine Environmental Laboratory
| INTRODUCTION The principal goal of the PACS program is to extend the scope and improve the skill of operational Pan-American seasonal-to-interannual climate prediction, and, in particular, to improve warm season rainfall prediction over the Americas. Improved predictability will depend crucially on improving our understanding of the oceanic boundary forcing, and in particular, the relationship between the surface heating gradient and the sea surface temperature (SST). The eastern tropical Pacific near the Pan-American land masses is characterized by southerly winds and a stratus deck which extends from the cool waters off South America to the convective region of the cold tongue (CT) / intertropical convergence zone (ITCZ) complex. Beneath the stratus and particularly near the equator, SSTs are cool, while at and north of the ITCZ, in the "breeding grounds" of east Pacific tropical storms, SSTs are extremely warm (Fig. 1). Anomalous SSTs in the eastern tropical Pacific have the ability to perturb the atmosphere and alter weather and climate both locally and remotely. On interannual time scales, SST anomalies associated with El Nino cause, and in turn are caused by, shifts in the basin-scale convection and wind patterns. On seasonal time scales, the cold tongue formation is associated with a meridional migration of the ITCZ and intensified southerly winds on the equator in the far eastern Pacific. On tropical instability time scales, variations in the SST are reflected in wind stress fields, apparently due to the influence of SST on the stability of the atmospheric boundary layer. On diurnal time scales, SST variations potentially have the ability to cause late afternoon cloud formation. Understanding the ocean-atmosphere coupling responsible for the structure and evolution of the large-scale heating gradients and wind and rainfall patterns in the CT/ITZC complex is a prime objective of the Eastern Pacific Investigation of Climate processes (EPIC) program, a 5-year process study initiated by PACS. PROJECT GOALS * Obtain near-realtime daily averages of all enhanced TAO data and make available to data center and the modeling community from PMEL-maintained ftp and websites. All standard TAO measurements from the new sites along 95°W (3.5°N, 10°N, 12°N) will also be made available through the GTS. Some of the new measurements, such as barometric pressure, will likewise be put on GTS. Post-processed and high resolution 10-minute and hourly averaged data will be made available in delayed mode via PMEL, as well as via national archives. * Analyze the diurnal-interannual evolution of the CT/ITCZ system. * Analyze the relationship between anomalous SST variability in this region and remote variability in the ocean-atmosphere-land climate system. * Use the enhanced TAO array to provide a large-scale framework for the intensive process study (EPIC2001) planned for this region in 2001. METHODOLOGY The enhanced moorings will have sufficient temporal resolution (10 minute or better) and duration (3-4 years) to monitor variability from the diurnal cycle through interannual variability. The data will be transmitted in near realtime so that data can be assimilated into models and data products. The first deployments were completed in April 2000. Each deployment is nominally one year. A ship will visit the line for deployments/recoveries/repairs every six months, typically in November and in April. Final recoveries are scheduled for fall 2003. ACCOMPLISHMENTS AND RESULTS A project homepage has been developed: http://www.pmel.noaa.gov/tao/epic The enhanced TAO mooring is in many ways similar to the IMET flux mooring. Both systems have a similar suite of instrumentation and can be considered flux moorings. However, the TAO and IMET systems were developed for different purposes over the past two decades and, among other things, have different sampling schemes and electronic interfaces. To establish the consistency of the two systems, a land-based intercomparison was performed at WHOI in May-June 2000. Initial analysis indicates that the two systems were consistent within standard measurement errors. A report documenting this intercomparison is underway. PUBLICATIONS RESULTING FROM THIS WORK To be updated as project progresses. CONTACTS Principle Investigator: Dr. Meghan F. Cronin Co-Principle Investigator: Dr. Michael J. McPhaden INSTITUTION LINKS http://www.pmel.noaa.gov/tao/epic Return to CLIVAR PACS Home Page |
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