Jennifer Clark goes
about her business on a warm, summer day in Kansas. The skies are blue from horizon to horizon,
not a cloud in sight. The conditions are
perfect for a relaxing summer afternoon.
A few hours later clouds arrive and the skies open up. The thunder shakes her house on its
foundation. The lightning illuminates
every inch of the residence. The
torrential rain limits visibility to only inches outside the window.
Some fear these typical thunderstorms that characterize
the plain states. Clark, however, enjoys
these types of storms. She observes them
roll in across the horizon, creeping ever closer. The constant rumbling of thunder doesn't faze
Clark; she carries on with her business.
Average number of days thunderstorms occur throughout
the United States.
"I like to go outside or stand at the window and watch
storms," Clark, Kansas City, Kan., junior, said. "The lightning in some can be
crazy. It's also nice to just sit inside and listen to them and go about my
activities."Thunderstorms are a common occurrence in Kansas and
around the world. Jon Van de Grift, Earth
scientist, said it is estimated that 40,000 thunderstorms take place every day
across the world and the U. S. sees 100,000 thunderstorms per year. "Thunderstorms are usually small,
organized parcels of warm and moist air that produce lightning and thunder,"
Van de Grift said. Characteristics of
any thunderstorm may include torrential rain, lightning, hail, and tornadoes.
In the U. S., thunderstorms occur
most often along the East Coast with Florida having more than 90 days of
thunderstorms per year. The Plain states
have the second most number of days with thunderstorms at 50-70 days and the
Rocky Mountain region follow the Plains with 30-50 days of thunderstorms per
year, according to the Oklahoma Climatological Survey.
However, the size of thunderstorms
is not equal in two different regions of the U. S. Dr. Donna Tucker researches this topic of
varying thunderstorm sizes across different geographical regions. Tucker, Atmospheric Science associate
professor, said the Rocky Mountain region has many thunderstorms, but they are
smaller than the thunderstorms found in Kansas.
"Thunderstorms may generate new
storms or grow from their outflow," Tucker said. "In the mountains the outflow is interrupted
by terrain variations so it is harder for thunderstorms to grow large. On the Plains without the terrain variations
to interrupt the outflow, thunderstorm complexes can grow large enough to cover
an entire state."
A thunderstorm's outflow is
responsible for maintaining its strength.
"When precipitation starts falling some
of it evaporates and cools the air around it," Tucker said. "The cooler
air is more dense than the air around it and sinks. When this cooler air
reaches the ground, it spreads out in outflow."
The outflow is a crucial part of the size of a
thunderstorm. A disruption in the
outflow will not allow the storm to grow large, but remain a small
thunderstorm. This is the cause of small
thunderstorms in Colorado. The outflow
is constantly disrupted by terrain variations such as mountains and
ridges. Since the outflow of the storm
is limited, the storm remains small.
The opposite is true for a region like Kansas. Kansas consists of no terrain variations, but
flat land across the state. Since the
state is flat the storm's outflow is not disrupted, but constantly fuels the
thunderstorm. Since there is a constant
outflow, the storms are able to grow to large a size; sizes that may encompass
the entire state.
Richard McNulty, Atmospheric Science professor, said he
agrees with Tucker's observations about thunderstorms and the effects
geographical regions have on their size.
"Based on my observation of the
atmosphere, Dr. Tucker is on target with her research," McNulty said. "Moisture
is needed to feed and grow these thunderstorm clusters. As she states, over the
mountains, higher moisture levels are typically confined to the lower
elevations, interrupted by the higher mountains. This limit on available
moisture impacts the size of thunderstorms."
McNulty
said there is a constant stream of moisture from Kansas to Texas that is not
interrupted. The moisture is then used
to "feed the mesoscale beast" or the thunderstorms increase in size.
All
of Tucker's research is computer-based.
She observes the data on the size of thunderstorms through radar and
writes down the results. The University
of Kansas has supplied some grant money to finance her research, but the
majority of it comes from the National Science Foundation. The foundation gives grants that range from
$100,000-300,000. Tucker said it's a hard process.
"Since
this is a lot of money, many people want it so the process is very competitive,"
Tucker said.
Tucker's interest in precipitation started this research.
Tucker said precipitation is so variable.
One part of Lawrence may get a lot of rain, but another portion will get
none. She is interested in the reasons
behind thunderstorm formation and their growth.
"When I started looking for the roots of the large
thunderstorm complexes that form on the High Plains, I saw that their origin
really was in the mountains," Tucker said. "Then comes the question of
why the mountain thunderstorms form. My research has applications dealing
with why thunderstorms form, where they do and why they will form in some
locations on one day and other locations on another day."
