The 
Tibet 
Connection 
Having discovered some new details 
of far-flung climatic linkages, 
meteorologists are reexamining 
historic weather maps and revising 
their computer models 
by Elmar R. Reiter 
Weather may seem to be just a local 
affair, but in fact, its events are not self- 
contained. Rather, each is part of a 
highly complex global system involving 
such variables as temperature, air pres- 
sure, wind, humidity, and precipita- 
tion. The bonds that join these 
atmospheric conditions are the jet 
streams — large, high-speed air currents 
that circle the earth in ever changing 
patterns at altitudes of five to thirty 
miles. Jet streams in the troposphere 
(the innermost layer of the atmosphere, 
extending up to about ten miles) travel 
at velocities of between 60 and 400 
miles per hour, moving blizzards, rain- 
storms, and squall lines, and dragging 
lower-lying air packages across the face 
of the land, thereby affecting local 
weather conditions. Over North Amer- 
ica the jet streams usually shift north- 
ward into Canada during the summer 
and migrate as far south as the Gulf of 
Mexico during the winter, but their be- 
havior is not always easy to predict. 
Erratic meanders in jet stream sys- 
tems are closely related to some of the 
Mount Everest, at the left, the world's 
highest peak, is on the Tibet-Nepal 
border. Rising 29,028 feet, it is part of 
the Himalayas. To the right is Lhotse, 
2 7, 923 feet high. Sheltered behind the 
1,500-mile-long curving Himalayan 
range is the Tibet plateau. Because the 
Himalayas do not lie at right angles to 
the airflow in the upper troposphere, 
jet streams can circle around them. 
Yoshikazu Sturakawa/ Image Bank 
65 
