Glossary and Acronyms: J

Jaxa:

Japan Aerospace eXploration Agency

Jason:

Jason-1 is the first follow-on to the highly successful TOPEX/Poseidon mission that measured ocean surface topography to an accuracy of 4.2 cm, enabled scientists to forecast the 1997-1998 El Niño, and improved understanding of ocean circulation and its effect of global climate. Jason-1 was launched in July 2001 and Jason-2 in June 2008.
The altimeter is the main instrument on the Jason-2 mission. Derived from the Poseidon-1 altimeter on Topex/Poseidon and the Poseidon-2 on Jason-1, it measures sea level, wave heights and wind speed.

Jet stream:

flat tubular, quasi-horizontal, current of air generally near the tropopause, whose axis is along a line of maximum speed and which is characterized by great speeds and strong vertical and horizontal wind shears.
The jet-stream axis is the axis along which the wind speed is the strongest at a given level (e.g. 250 hpa).
The jet-stream core is the line which the wind speeds are maximum both in the vertical and in the horizontal.

JMA:

Japan Meteorological Agency.

JTWC:

Joint Typhoon Warning Centre (USA, Pearl Harbor).

Jet (Subtropical):

Strong westerly winds observed near 30° of latitude, feeding by the Hadley cells. The most powerful subtropical jet (70 knots in zonal and monthly average) is always located in the winter hemisphere, where the Hadley cell is the stronger.