North Americans have literally had to face some very rough weather this year After having dealt with a sweltering summer with sky-rocketing temperatures, they have just rubbed shoulder with the blizzard of the century! What could be the culprit behind this winter's blizzard in the US?...Scientists wonder
THE record highs of summer, this past,
year in the us, could be attributed to the
phenomenon of global warming. But
what about the blizzard of 1996 which
lashed throughout northeastern us,
depositing more than 50 cm of snow in
most areas, dipping mercury levels and
paralysing normal life? The blizzard has
left scientists wondering if global warming had masterminded this spell of chilling weather or if it was simply an
unforeseen natural phenomenon.
Whatever be the reasons behind
such occurrences,' "extremes of this kind
are becoming more frequent," say
researchers from the National Climatic
Data Centre, Asheville, North Carolina,
us. They have analysed the temperature
and precipitation data of the us for the
20th century and found that the period
between 1980 and 1994 has experienced
the maximum instances of extreme one-
day precipitation, over-all precipitation,
The mean location and velocities of the
westerly jet-stream in -the Northern
Hemisphere in January
above normal temperatures and
droughts. "It is rather interesting that
we seem to be getting these 'storms of
the century' @very few years," remarks
Thomas R Karl, heading the Asheville
research team.
Climatologists in their assessment of
the situation in the us this winter, are
subscribing to a variety of explanations.
Some favouring the global warming theory, have presented evidence which suggests that climatic changes associated
with global warming could indeed
create such heavy snowstorms and on
the whore, greater extremes in precipitation. According to them, the warming of
the earth will not result in seasons disappearing but will only mean more rain,
sleet or snow, as the rate at which water
from the oceans evaporates, increases.
And in regions where global atmospheric
circulation does not permit precipitation, global warming shall produce hotter heat waves and even more severe droughts.
Another theory on the
deluge this winter postulates that the, blizzard was
not a rare event but simply
one with a higher intensity.
Research meteorologist
Vernon E Kousky of the
National Weather Service's
Climate Prediction Centre,
Maryland, us, points his fingers at the super powerful
jet stream (a current in the
upper mosphere), moving
across the region. According
to Kousky, the jet stream
was strong and sucked up
huge amounts of Arctic air.
The resulting creation of a
low pressure zone over the
northeastern us prompted
the inflow of air. Warm
moist air from the Gulf of
Mexico was pushed up high
into the atmosphere, where it met a mass of heavy cold air moving south from the Arctic region and Canada. When the warm moistqre- laden mass met the cold polar air, tur- bulent conditions were created. The snowfall this time was heavier than usual as the temperature of the cold air was extremely low. These climatologists feel that such seasonal movements of air are much more significant than the smallscaJe changes produced by global warming.
The shortcomings of our forecasting skills are further pushed to the fore when such disasters strike. The undet- standing of the earth's turbulent atmos- phere is still imperfect and analytical tools like computer models cannot really be on par With real weathe! condi- tions. An element of uncertainity seems unavoidable. For instance, scientists had predicted that this year's winter would be a mild one but as one knows, th~ situation has been far from being mild.
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