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Climate variability and observations

As part of a special issue of the J. Climate arising from the June 2004 CLIVAR science conference, current and past members of the Atlantic Implementation Panel of International CLIVAR, completed a comprehensive review of three interrelated climate phenomena: Tropical Atlantic variability (TAV), the North Atlantic Oscillation (NAO), and the Atlantic Meridional Overturning Circulation (MOC) (Hurrell et al. 2006a). These phenomena produce a myriad of impacts on society and the environment on seasonal, interannual, and longer time scales through variability manifest as coherent fluctuations in ocean and land temperature, rainfall, and extreme events. As well as a review of the state of understanding of Atlantic climate variability and achievements to date, considerable discussion was given to future challenges related to building and sustaining observing systems, developing synthesis strategies to support understanding and attribution of observed change, understanding sources of predictability, and developing prediction systems in order to meet the scientific objectives of the CLIVAR Atlantic program.

Also featured in the CLIVAR special issue of J. Climate is a write up of a keynote invited presentation on climate observations at the International CLIVAR conference in Baltimore in 2004 (Trenberth et al. 2006c). It focuses on the need for a climate information system, reprocessing of datasets to create climate data records, reanalysis of observations to create multivariate global gridded fields (see also Uppala et al. 2005), and the use of the resulting products, including as initial fields for climate predictions. The role of the oceans in climate is described in Trenberth (2006) along with ocean observations and their analysis in National Oceanic and Atmospheric Administration (NOAA).

High-frequency ocean-atmosphere coupling was explored by Jochum et al. (2006) and Ueyama and Deser (2006). Tropical instability waves, which are due to internal ocean dynamics, have a significant impact upon surface zonal wind and precipitation variability in the tropical Pacific, and thus may be a source of “stochastic” noise in the climate system that may in turn augment the excitation of ENSO (Jochum et al (2006). The climatological semidiurnal and diurnal variability of surface winds in the tropical Pacific, using 12 years of data from the Tropical Atmosphere Ocean Moored Buoy Array, feature a large-scale diurnal pattern of surface wind convergence in the tropical Pacific, which may have implications for the diurnal cycle of rainfall (Ueyama and Deser 2006).

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