Pacific decadal oscillation

The Pacific Decadal Oscillation ( PDO abbreviation; . Engl pacific decadal oscillation ) denotes an abrupt change in the surface temperature in the northern Pacific Ocean.

The phenomenon of the Pacific decadal oscillation has been detected and named in 1996 by Steven Hare of the University of Washington. The determined by the PDO array of hot and cold water regions in the northern Pacific dominates the main flow direction of the jet stream and thus has long-term and significant impact on weather patterns.

State changes of the PDO correlated with major changes in the ecosystem of the northeastern Pacific: had warm phases a higher biological productivity in the coastal regions of Alaska, but a decreased productivity off the west coast of the United States result. Cold phases showed an inverted North-South pattern as regards the productivity of these marine ecosystems.

The following climate anomalies in North America go with extreme phases of the PDO associated:

Independent studies suggest that there were only two full PDO cycles in the past century: A cold PDO regime, which lasted from 1890-1924 and from 1947-1976, while warm PDO regime, the years of 1925-1946 and of 1977 to mid-1990 specific. PDO fluctuations in the 20th century took place in two cycles instead: One had a duration of 15-25 years, the other for a period of 50-70 years. The greatest decade wide state changes of the PDO in the period from 1706 to 1977 took place in 1750, 1905 and 1947. The pronounced bi- decadal oscillation of the PDO index was seen only in attenuated form from the late 18th to the mid 19th century.

The PDO is significantly different from the El Niño Southern Oscillation ( ENSO ): PDO events held in the 20th century for a period of 20 to 30 years, whereas ENSO events lasted only 6 to 18 months. Secondly, make PDO events in the North Pacific America evident, with smaller effects in tropical regions. When ENSO is true, however, just the opposite.

El Niño events can be attenuated by a cold phase of the PDO, La Niña events, however, be strengthened. In 2008, a change of the PDO was found towards a cold regime, what the impact of the present La Niña strengthened.

It is not known what mechanisms are put behind the PDO. Therefore, there is little predictability of this air ratio. Some climate models show PDO -like oscillations, but often differed in their reasons. The quality decadent accurate climate projections is determined by the understanding of the mechanism behind the PDO '. But even without a precise theory improve detailed knowledge of the PDO year-related climate forecasts for North America, as a condition usually has many years of existence. Alexander et al. (2008) were able by means of a statistical model of the state of PDO over a period of up to 4 years to predict with good results; issued by the NOAA PDO forecasts are made using this model.

The property of PDO to remain in one state for decades shows that distinguish "normal" air conditions over a period of time which corresponds approximately to the duration of a human life.