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Tibet has thinner air, more sunlight, lower temperatures
and less precipitation than other areas in China. The
air contains only 150 to 170 grams of oxygen per cubic
meter, 62 to 65.4 percent the rate found in plains
areas. Solar energy is more readily available than
elsewhere nationally, with more than one-third to even
double that available in plains area at the same
latitude. There are also more hours of daylight than
elsewhere in China; in Lhasa there are 3,021 hours of
daylight annually. Daytime and nighttime temperature
vary greatly, despite low average temperatures and low
annual temperature differentials. Average temperatures
and peak temperatures for the hottest month in Lhasa and
Xigaze are 10-15 degrees centigrade lower than in
Chongqing, Wuhan and Shanghai at about the same
latitude. Annual temperatures in Lhasa, Qamdo, Xigaze
and elsewhere in Tibet range 18 to 20 degrees centigrade
over the yea! r. At elevations in excess of 5,000 meters
in Ngari Prefecture, daytime temperatures in August
climb above 10 degrees centigrade, only to fall below
zero at night.
Seasonal
precipitation is disproportionately distributed
throughout the region. The dry season and the rainy
season are clearly demarcated. Rain usually falls at
night. Annual precipitation is 5,000 millimeters in the
lower elevations to the southeast decreasing gradually
to a mere 50 millimeters in the northwest. Precipitation
from October to April accounts for only l0 to 20 percent
of the yearly total. Rainfall is concentrated in the
period between May and September, accounting for about
90 percent of the yearly precipitation.
Geological Features of Tibet
From the view of earth science, Tibet plateau is one of
the most interesting regions in the world.
It is the highest plateau in the world, with an average
altitude 4,500 meters. Tibet Plateau has many firsts as
following: It has the highest mountains in the world Mt.
Qomolangma 8,850 meters
It has the largest canyon in the world Yarlung Zangbo
River Great Canyon with a total depth 5,382 meters. It
has the largest scale of vertical eco-system zones, from
the highest point on the earth 8,850 m, to the bottom of
valley 900 meters elevation. It has numerous glaciers
and originations of many important rivers are here. It
has very unique environment and many unique plateaus.
Tibet Plateau is the main body of the Qinghai-Tibet
Plateau, consisting of high mountains and great rivers,
prairie and gorges. On the Tibet Plateau stands the
world-famous Himalayas in southwest, the Kunlun
Mountains and the Kalakunlun Mountains spread the
northwest, the Gangdisi, Tanggula and Nyainqentanglha
Mountains traverse the middle, and the Hengduan
Mountains is its east barrier. There are 6 peaks of over
8,000 m! eters at sea level, 50 peaks of over 7,000
meters at sea level and numerous peaks of over 6,000
meters at sea level in Tibet, where the world's highest
summit Mt. Everest erects with an elevation of 8848.13
meters.
Amidst the numerous high and gigantic mountains spread a
range of hills, lakes and gorges, constituting
undulation alpine prairie. The famous Qiangtang
Grasslands on North Tibet spreads from east to west over
2,400 kilometers and from north to south over 700
kilometers, averaging 4,500 meters at sea level. The
boundless grassland is the principal pastoral area in
Tibet.
Tibet is also one of the regions in the world with the
most gorges. These gorges mainly distribute in the east
of the Tibet Plateau and the south outlying areas,
culminated by the Yarlung Zangbo Great Gorge and East
Tibet Three Rivers Gorges.
There are intensive rivers and lakes in Tibet. There are
over 20 rivers with valley area larger than 10,000
Square kilometer, and over 100 river! s with valley
larger than 2,000 square kilometers. The famous rivers
include the Yarlung Zangbo, Jinsha, Nujiang and Lancang
rivers. The Asia-famous Ganges River, Indian River and
Mekong River all originate there. The region has over
1500 lakes including 47 with over 100 square kilometers.
Lake area stands at 24,183 square kilometers,
representing over one-third of the total lake area in
China.
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