RQL's Blog 菜鸟成长记



Climate Change and Climate Modeling

Chapter 4 El Niño and year-to-year climate prediction







在向EINino转变时,深厚的温跃层从赤道太平洋西部向东部传播。当太平洋东部的温跃层也变深厚后,在上升流的影响下时太平洋东部海温升高,进而激发 Bjerknes feedbacks 。随后该反馈进一步使太平洋西部的温跃层变浅,这也是EINino向LaNina转变的一个信号,因为随后太平洋西部的这一浅温跃层又会向太平洋东部传播。





the essential features of sth

the mechanisms for maintaining a fully developed El Niño (warm) or La Niña (cold) phase

While the heart of ENSO lies in the tropical Pacific, impacts in other parts of the world are also important. Such remote effects of El Niño or La Niña are termed teleconnections.

During the 1980s and 1990s many investigators contributed to making this conjecture a full fledged theory.

In essence, ENSO arises as a coupled cycle in which anomalies of SST in the Pacific cause the trade winds to strengthen or slacken, and this in turn drives the ocean circulation changes that produce anomalous SST.

As we shall see, the dynamics of “how the turnabout” takes place involves subsurface ocean dynamics.

the trade winds blowing from east to west across the Pacific

Surface currents exactly on the equator tend to flow westward, accelerated by the wind stress on the ocean surface due to frictional effects.

While we often show anomalies for these conditions, it is useful to remember what the total fields look like.

In terms of anomalies, this corresponds to a westerly anomaly, even though the total winds may still be easterly.

Initial success in the Pacific led to subsequent deployment of similar buoys in the Atlantic, and ongoing deployment in the Indian Ocean. The observations are transmitted via satellite to data centers, where they are compiled and made available to researchers and forecast centers almost immediately.

The depression of the thermocline extends slowly from west to east along the equator.

Basically the cold anomalies along and off the equator in the west are a La Niña waiting to happen. This allowed model predictions of the 1998–99 La Niña, just as the subsurface warm anomalies allowed predictions of the preceding El Niño.

On the oceanic side

It is also worth noting that the succession between El Niño and La Niña is not always so rapid and can be more complex than the example provided by the 1998 case.