Introduction

The Comprehensive Ocean-Atmosphere Data Set (COADS) is the most extensive collection of surface marine data available for the world ocean over the past century and a half. In COADS processing, the basic observational data have been edited, using a "trimming" procedure to identify outliers with respect to climatological 3.5 sigma limits derived from data for three periods (1854-1909, 1910-49, 1950-79). A variety of observed and derived variables has then been summarized for each month of each year and decade of the period of record, currently 1854-1992, using 2-degree latitude x 2-degree longitude boxes (and using the 1950-79 limits for trimming after 1979). Resulting observational or summary statistical products are now used by over 200 research groups worldwide, but vigorous efforts continue to update and improve the available products.

Until recently, COADS Release 1 (Slutz et al., 1985; Woodruff et al., 1987), covering 1854-1979, had been extended for 1980-1991 by a set of "interim" products. However, the interim products were constructed using simplified procedures (e.g., for elimination of duplicate reports) that did not yield the full set of Release 1 statistics. Annual updates of the interim products (for 1985-91) had the additional limitation of relying primarily on the Global Telecommunication System (GTS) for foreign ship reports because receipt of international ship logbook data is often delayed by 2-5 years (Jenne, 1992). Moreover, concerns about the trimming performance during extreme climate anomalies such as the 1982-83 El Niño/Southern Oscillation event (ENSO) (Wolter, 1992) prompted us to reevaluate the quality control procedures employed in COADS.

COADS Release 1a, offering a set of extensive and easily used products for 1980-92, has now been completed to address many of these shortcomings for that period. To provide consistency with Release 1, as well as the broadest possible coverage and improved quality control, we have created two alternative sets of 2-degree monthly summaries for 1980-92. These products and other aspects of Release 1a are discussed in the following sections.