Over the past 15 years the increasing interest in climate analysis and forecasting has been evidenced by many national and international programs dealing with the problem or using to justify related research¾the North Pacific Experiment (NORPAX); Equatorial Pacific Ocean Climate Studies (EPOCS); Pacific Equatorial Dynamics (PEQUOD); Tropical Pacific Ocean Heat and Mass Budgets (Tropic Heat); Seasonal Equatorial Atlantic Experiment (SEQUAL); Tropical Ocean Global Atmosphere (TOGA); and World Climate Research Program (WCRP). In part, all of these set out to improve the atmospheric and oceanic data bases. EPOCS conceived and partly funded a large joint effort to compile global ship observations by the Environmental Research Laboratories of NOAA; the Cooperative Institute for Research in Environmental Sciences (CIRES) of NOAA and the University of Colorado; the National Center for Atmospheric Research (NCAR); and the National Climatic Data Center (NCDC) of NOAA. The result was the Comprehensive Ocean-Atmospheric Data Set (COADS) for the period 1850-1979. Details of how the ship observations were collected, evaluated, and compiled on a 2° by 2° grid are contained in Woodruff et al. (1987). We selected the last 80 years, 1900-1979, for this atlas.
Figure 1. Year-month number in thousands of ship observations per ocean basin.
Figure 2. The average distribution of ship observations per 2° square per individual month for the 80-year period ;1900-1979. Black- >30; grey = >10<30; chicken tracks = >2<10; no shading = <2; dashed lines enclose areas of <1.
ANALYSES
The inadequate number and uneven distribution of data coupled with large gradients and the relatively small atmospheric systems in the tropics require a manual analysis for optimum results. In this atlas, manual analysis, in contrast to machine analysis, permits a variable radius of data influence (a variable amount of smoothing) and the incorporation of auxiliary information and experience. For example the wind analysis utilizes knowledge of the distribution of sea level pressure, sea surface pressure, sea surface temperature, rainfall, satellite cloudiness; orography and coastal effects; persistent wind systems and patterns; and climatological constraints.
Recent atlases, produced by machine methods from essentially the same data base, differ significantly from our atlas (Hastenrath and Lamb, 1979; Reynolds, 1985). When compared to recent wind stress produced by a machine analysis scheme (Picaut et al., 1985), differences amount to 25% in the maxima, minima, and gradients of monthly averaged wind stress.
ELEMENTS AND CHART FORMAT
Of the 19 available parameters in the COADS, wind, wind stress, sea level pressure and sea surface temperature were selected for publication since they are of interest to the greatest number of people in the World Climate Research Program (WCRP). The four fields are shown [in the original print version] on facing pages for easy intercomparison. Total cloudiness determined from nine years of satellite observations has been published (Sadler et al., 1984). COADS total cloudiness shows identical patterns but poorer data coverage so is not included in the atlas. So as to maintain a comparable reproduction scale for the three oceans, the atlas is in two volumes. Volume I contains the Atlantic and Indian Oceans and Volume II the Pacific Ocean. The data plots for each element contain (1) the number of observations during the 80-year/month period within each 2° square and (2) the 80-year/month average value of the element after weighting each year/month value by number of observations. The observed resultant directions of the wind and wind stress are shown by arrows with the length of shaft proportional to the resultant speed of the wind and value of the stress.
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