Oscillations and teleconnections - The Global Climate System: Patterns, Processes, and Teleconnections - page 34

Background Box 2.1

Monitoring intraseasonal oscillation in the tropics
The major intraseasonal oscillation in the tropics is the Madden-Julian Oscillation,
the MJO. Given that most climatological variations that occur on a monthly basis are
related to precipitation, the feature plays a significant role in the nature of the
regional climate. The MJO is identified by the eastward progression of a large region
of either enhanced or suppressed rainfall.
It has proved difficult to accurately model the MJO. Generally, dynamic models
do not work well with tropical convective rainfall, while the slow evolution of the
MJO further complicates accurate prediction. Because of this, a variety of more
conventional means are used to monitor the feature.
Of singular importance is information derived from polar-orbiting and geostationary
satellites. This fundamental diagnostic tool uses derived images and data to identify
regions in which convectional activity departs from a derived long-term mean.
The global radiosonde network, which provides data twice daily, is used in conjunction
with satellite analysis. Radiosondes provide temperature, pressure, moisture values,
and wind data at many levels of the atmosphere. The data are incorporated into weather
prediction models that are used for weather and climate analysis.
The nature and location of the MJO uses are displayed in time-longitude format to
reveal a number of characteristics. The Climate Prediction Center of NOAA lists the
following:

1. outgoing long-wave radiation, a satellite derived measure of tropical convective
activity and precipitation;
2. velocity potential, a derived quantity that isolates upper level divergence;
3. upper level and lower level wind anomalies;
4. 500 hPa anomalies to represent the atmospheric responses in mid-latitudes.

While the features are used to identify and monitor the MJO, it is also thought that
the oscillation plays a role in hurricane formation and ENSO events. Researchers at
many atmospheric science centers are actively monitoring the MJO and seeking to
assess its role in many teleconnections.

Hurricane Center have been informally using the MJO, the linkage is currently
insufficient for accurate modeling and forecasting.

2.6 The Quasi-biennial Oscillation (QBO)
The QBO is a low-latitude oscillation that is longer than the dominant annual
cycle and its identification rests with sophisticated computer modeling