Cooperative Institute for Research in Environmental Sciences

Ocean Interactions
Ocean and Atmosphere connecting Scientists, Teachers & Students

The Tropical Atmosphere Ocean (TAO) Array

The Equatorial Pacific
Scientists are very interested in what goes on in and around the Equatorial Pacific because of the strong influence the area has on our weather and climate. The Pacific warm pool is located at the western edge of the Pacific, over by southern Asia. The sea surface temperatures in this region are the warmest found in all the oceans, averaging about 27C. Because it is so warm, there is a lot of rising air, or upwelling of air in that region. The air is very moist and when raised, clouds form and it rains. On the other side of the Pacific, deep, cold water is forced to the surface through oceanic upwelling. As a result, the ocean surface temperatures are much cooler in the eastern sector of the Pacific than on the western side, and thus the surrounding air is cooler also and comparibly less rain falls in the East. A circulation of rising air in the west and falling air in the east occurs because of the temperature difference.

El Nino / La Nina
As we have discussed previously, "El Nino" has its origins in these regions of the Pacific. Sometimes the warmer water gets pushed farther east into the cold pool region, causing the colder water of the east to warm up. This causes a shift in that atmospheric circulation. It becomes drier in the west (droughts) and wetter in the east (floods) as a result. The opposite can occur too, where the colder water pushes farther west into the warmer water. This is called a La Nina. Generally, after an El Nino, a La Nina will form. This El Nino / La Nina cycle is part of a larger-scale phenomenon referred to as the Southern Oscillation. Both of these oceanic phenomenon have far reaching affects across the world. For example, during an El Nino, the west coast of the US tends to be wetter and colder during the winter time and upper midwest is more mild.

By monitoring the atmosphere and the ocean in this region of the Pacific with the TAO buoy array, scientists can gain a better understanding for how the El Nino/Southern Oscillation cycle works and how to better forecast its potential effects on our weather and climate.

The TAO Buoy Array
The goal of the TAO (Tropical Atmosphere-Ocean) buoy array is to provide high quality real time data on the ocean and atmosphere from the equatorial Pacific Ocean for seasonal and interannual climate studies with an emphasis on El Nino and the Southern Oscillation. The array was completed in December of 1994 and has been transmitting data about the atmosphere and ocean ever since. Every 6 months, ships like the NOAA Ship Ronald H. Brown and the NOAA Ship Ka'imimoana come out and take care of the buoys, either fixing the buoys already there, or by replacing the existing buoy with a completely different one - more often the latter.

The buoys are evenly distributed across the Pacific along the equator from 8N to 8S in latitude and about every 15 degrees of longitude, starting at 95W in the eastern Pacific. The buoys make a variety of different measurements both above and below the ocean surface. Above the surface, mounted on the top of the buoy, there is an air temperature sensor along with a relative humidity sensor. A rain gage and an anemometer measurements of rain amounts and wind speed and direction. Some of the buoys, mainly along the equator, also have a radiometer that measures short wave and long wave radiation. Below the buoy, a cable runs down for about 550 meters, with sensors attached at various depths. The sensors measure mainly temperature, but can be also set up to measure pressure and conductivity. In the eastern Pacific, the sensors are set every 20 meters up to 140 meters, then at 180, 300, and 500 meters. The sensors at 300 and 500 meters also measure pressure. West of 140W, the sensors are set every 25 meters, with the last two sensors again at 300 and 500 meters. Bulk sea surface temperature is measured with a similar sensor approximately 1 meter below the ocean surface. Also mounted on the top of the buoy is the main system that communicates with all the sensors and transfers the data via satellite to the scientist on shore. The "tube", as it is affectionately called by the buoy techs, sends out signals to the instruments on a daily basis, asking for their respective daily averages, and then sends those averages to shore via the Argos Satellite system.

The data collected from the TAO buoy array have been instrumental in allowing scientists to better understand El Nino and the Southern Oscillation as well as increasing our knowledge of influences to the North American climate system. Most importantly, this information has led to improvement to U.S. weather forecasting.

The NOAA Pacific Marine Environmental Laboratory's (PMEL) TAO Buoy Group representatives on the Ron Brown during this cruise are (L to R): Ben Moore, Mike Craig, and Korey Martin. Here, they are finalizing the assembly and testing of the 110W, equator buoy.