Climatic Data, Oceanic Observations

CLIMATIC OCEANIC OBSERVATIONS are marine meteorological and deep ocean observations that are performed for a long time (at least over a few decades) using specialized océanographie vessels, volunteer merchant ships, buoy arrays, floats, and drifters. Marine meteorological observations are performed over a few centuries. Voluntary observations by merchant ships (volunteer observing systems, or VOS) report most of these data. Standard marine meteorological observations include sea-level pressure, air and sea-surface temperatures, humidity, cloudiness, velocity, and direction of wind.

Marine meteorological observations have been collected and generalized in the Comprehensive Ocean-Atmosphere Data Sets (COADS). However, the differences in instruments and observation techniques, and construction and size of various ships, reduce the compatibility of different data for analysis of climate variability and change. One of the most comprehensive analyses of this problem has been done at the CLIMAR 99 WMO workshop.

Between 1948 and 1984, the Ocean Weather Station (OWS) network operated in the North Atlantic and Pacific Oceans. The principal goal of this network was to get oceanic meteorological and aerological data for improvement of the weather forecast in North America, Europe, the North Atlantic Ocean, and the Pacific Ocean. At the same time, OWS performed deep-ocean hydrographie casts and soundings. This network provided long-term and compatible deep-ocean time series of temperature and salinity, and aerological data on wind, pressure, temperature, and humidity within air columns up to about 19 mi. (30 km.). The OWS network initially consisted of 13 stations in the North Atlantic and nine stations in the Pacific. After 1973 (when a world economic crisis occurred), funding was cut off, and in 1984 (soon after beginning of the satellite era in meteorology), OWS observations ceased (with the exception of one Norwegian station in the North Atlantic that is still in operation).

Deep-sea hydrographie observations have been performed since 1872. Pre-1970s hydrographie casts were performed using Nansen bottles, and were the [Page 242]main source of deep-sea hydrographie data. Then, the expandable bathythermograph (XBT) and conductivity-temperature-depth (CTD) soundings replaced the Nansen bottles' measurements. However, the routine océanographie observations are too sparse and noisy for the reliable detection of low-frequency (long-term) changes of the oceanic fields in the deep ocean (below 2,625 ft. [800 m.]), except near a few standard océanographie sections and some specific regions with strong océanographie activity.

Long-term buoy arrays have been deployed in a few key regions of the world's oceans, such as the tropical Pacific and Atlantic, since early 1990s. The Tropical Ocean-Global Atmosphere-Tropical Atmosphere Ocean (TOGA-TAO) and Pilot Research Moored Array in the Tropical Atlantic (PIRATA) mooring networks are in operation. They perform marine meteorological observations and subsurface océanographie measurement in approximately the first 984 ft. (300 m.), and regularly transmit information to the satellite.

The Rapid Climate Change (RAPID) mooring array has monitored the meridional circulation in the North Atlantic along 26.5 degrees N since March of 2004. First results published by Stuart Cunningham, et al, showed that meridional overturning could be observed with errors smaller than 1.5 Sv (one Sv equals a flow of ocean water of 106 eu. m. per second). This shows the beginning of thermohaline catastrophy (which occurs when meridional overturning in the North Atlantic Ocean shuts down) at the early stage and superimposed high-magnitude interannual variability of meridional circulation.

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