Parameter Tree:
EARTH SCIENCE > CLIMATE INDICATORS > ATMOSPHERIC/OCEAN INDICATORS > TELECONNECTIONS > BLOCKING INDEX

Definition:
Blocking in the southern hemisphere typically occurs at lower
latitudes when compared with the northern hemisphere. The index
follows Tibaldi et al. (1994).
The European blocking index is based on observations of pentad (5-day
average) wind over the region 15W to 25E and 35n to 55N. If the pentad
zonal wind equals the climatological value for that time period, the
index is zero. If the pentad zonal wind is less than average the index
is postive, while the opposite is true if the index is
negative. Values close to +/- 1 indicate relatively strong events.


Reference:
Tibaldi, S., E. Tosi, A. Navarra, and L. Pedulli, 1994: Northern and
Southern Hemisphere seasonal variability of blocking frequency and
predictability. Monthly Weather Review , 122, 1971-2003.

See:
http://www.cpc.noaa.gov/products/precip/CWlink/MJO/block.shtml