Earth Science
¨ Weather in Edmonton on Oct. 9, 1954
¨ When does a pond become a lake? Is
there a difference?
¨ During which time period were the Palisades cliffs of New
Jersey formed?
¨ Tornado formation and frequency in Alberta
¨ Explanation for ice shards on Pigeon Lake
¨ How many times does lightning strike the Earth?
¨ Does lightning
start from the ground or cloud?
¨ Claire Martin's weather forecasting award
¨ What is the prevailing wind direction in
Sherwood Park, Alberta?
¨ What is a clear sky
clock?
¨ Which websites do you use in your weather
forecasts?
¨ How do I get historical weather data for
Fort Saskatchewan, Alberta?
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QUESTION:
I need to know what the weather in Edmonton was for Oct. 9, 1954. It's
my in-laws 50th Anniversary and we are trying to find out as much as possible
about that day.
ANSWER from Stephanie
Wong on 13 September 2004:
Your best bet for obscure weather data for Edmonton is to contact Environment
Canada. If you cannot find the correct info online, please contact Environment
Canada via one of their phone numbers on their website. If the data is
not publicly available, you will likely have to pay a fee to get the data that
you want. If you want to look through old archives of The Edmonton Journal,
ask Rutherford Library at the University of Alberta: http://www.library.ualberta.ca/. They
might have hard copies, or microfiche, or they may be able to to direct you
to the correct source. You might also want to ask the people at The Edmonton
Journal directly.
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QUESTION:
When does a pond become a lake? Is there a difference?
ANSWER from Stephanie
Wong on 21 August 2004:
I checked the Oxford English Dictionary, and it appears that "pond" usually
refers to a small body of water of artificial origin. A "lake" is
a large body of water such that it is considered a geologic formation. That
being said, I think people often use such terms interchangeably, so the line
is really blurred. There are no concrete "definitions" for
the common names of bodies of water on Earth. Unlike the other planets,
which we have largely named geologic features during the scientific era where
we have to classify everything into categories, the names for bodies of water
on Earth have been named throughout human history and so do not have a coherent
consistency. I've seen natural "ponds", and so-called small
artificial "lakes". So in the vernacular and general populace,
naming is almost entirely subjective. However, geological societies might
have stricter definitions they use to officially classify bodies of water. A
biological example of this is the naming of species. An animal will have
a precise species name, defined to the key, yet it might have numerous common
names that don't even have it in the correct family of species. Whether
there is an exact scientific definition of a lake or pond, try contacting someone
at the Geological
Survey of Canada.
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QUESTION:
During which time period were the Palisades cliffs of New Jersey formed?
ANSWER from Stephanie
Wong on 21 August 2004:
According to: http://www.geo.hunter.cuny.edu/bight/trips.html,
the Palisades were formed during the Triassic Period. The Triassic period
existed about 200 million years ago.
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QUESTION:
I live in Calmar Alberta. I have always had a VERY bad fear of tornadoes
and I was just wondering if you could answer a few questions for me about them:
1.) How hot does it have to be for a tornado
to occur?
2.) How probable is it that a tornado will come to Calmar?
3.) Are tornadoes rare in Alberta and Calmar or can they happen a lot?
ANSWER from Claire Martin
on 23 June 2004:
1. Tornadoes are not simply created by hot temperatures - they are formed below
strong thunderstorms when warm, humid air tries to push through cooler, dry
air. As long as the air aloft is cooler than the air rising, there is
the potential (under certain conditions) for a tornado to form. Then
- pushed by a cross wind - the air begins to swirl forming a funnel cloud. If
the tunnel touches the ground it is called a tornado. Most tornadoes
stay on the ground for between 10 and 15 minutes, during that time they can
travel about 10 km.
2. We here in central Alberta are "lucky" enough
to live in a "hot region" for tornado development. So
Calmar will very likely see a tornado one day in the future.
3. On average we get between 12 and 20
tornadoes in central Alberta a year.
Note that the best defense against tornadoes
is by being "sky aware". For a great web site on
summer severe weather preparedness check out the Environment
Canada web site - and go to the link "Skywatchers".
Claire Martin
Meteorologist
Global Edmonton
Alberta, Canada
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QUESTION:
I was out at Ma-Me-O Beach on Pigeon
Lake May 1 and 2. The amount of ice that had been blown up onto
the beach was incredible. It was like a carpet of ice shards,
several feet thick in places. I would like to know what causes
the ice to form in such a way. Also, in several places, there
were circles of ice about 8 inches across that were more opaque and
there was a hole in the centers. Any ideas on that? It
was incredibly beautiful and weird at the same time.
ANSWER from Edward Lozowski
on 25 May 2004:
Ice shards are typical results of
decaying (melting) lake and river ice. This ice is sometimes referred
to as rotten ice and the individual ice crystals, which are typically
long and thin, extending from the surface to the bottom of the ice sheet,
break apart. The wind and waves can then pile them up on shore. As
to the chunks of ice with circular holes, I really don't have an explanation. Perhaps
they are the remains of ice fishing holes, but I doubt it. I would
really need to see a photograph to be able to offer a better explanation.
Edward Lozowski
Professor
Department of Earth & Atmospheric Sciences
University of Alberta, Canada
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QUESTION:
How many times does lightning strike the Earth?
ANSWER from Michelle Mock
on 21 April 2004:
Happy Earth Day!
Lighting strikes somewhere on the Earth
approximately 100 times every second! This makes for a good
math problem for you. How many times is that per year?
Here are some interesting sites for you
to look at:
http://www1.msfc.nasa.gov/NEWSROOM/NSSTC/news/releases/2002/N02-001.html
http://news.nationalgeographic.com/news/2002/09/0925_020925_lightning.html
http://www.nationalgeographic.com/lightning/
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QUESTION:
There is a debate going on about where lightning comes
from. Some say it starts in the sky, some say it
starts in the ground. I would like to put an end to
this argument with facts.
ANSWER
from Stephanie Wong on 19 July 2003:
Lightning is a process due to electric charges, fields
and potentials. By where lightning "comes from",
I gather that you mean from where you first start to see
the flash of lightning. The answer is that the
flash can start from either the ground or cloud, but the
latter is extremely rare. I will discuss the common
case:
The science of what causes
the conditions for thunderclouds to be conducive to
producing lighning is still under investigation. I
will not mention them here. However, the actual
process of producing that spark is well known. It
starts out when the cloud is polarized, meaning there is
an abundance of postive charges on the top and negative
charges on the bottom of the cloud. A basic
principle of electricity is that like charges repel and
unlike charges attract. The bottom of the cloud
repels the negative charges on the ground, forcing them
below the ground and inducing the surface with a net
positive charge. Now, since the bottom of the cloud
and the ground surface have unlike charges, they attract
each other. Electrons from the cloud propagate
slowly towards the ground in a stream, thereby ionizing
the air around it. When a "leader"
reaches the ground (or near the ground), there is a huge
"dumping" current as the electrons rush to the
ground. When this occurs, the ionized air suddenly
recombines to its constituent atoms, starting from the
point of ground contact up. In order for the
molecules to recombine, they must release a large amount
of energy, and we see that as light energy. So, in
the most common case, we see lightning go from ground to
cloud.
The process is reversed in
cases where we begin with a positive charge on the cloud
bottom, or in some cases where we have large structures (like
towers) on the ground. These are rare and where you
see lightning "fork up". Also note that
occuring frequently is lightning from cloud-to-cloud or
within an cloud itself.
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QUESTION:
Claire,
We are at work discussing your latest award. You
won an international award this week. Please tell
us about it.
ANSWER
from Claire Martin on 9 April 2003:
I won the "presenter's award" at the 13th
International Weathercasters Festival in Zagreb, Croatia. This
festival tries to bring participants from all around the
world together to share different ways of weather
presenting - this year there were presenters from Moscow
to Melbourne and from Senegal to Switzerland.
It was a great honour!
Claire Martin
Meteorologist
Edmonton, Canada
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QUESTION:
I live in Sherwood Park, Alberta and was curious which
way the wind blows the most.
ANSWER
from Claire Martin on 17 February 2003:
Hmm.. the good ol' prevailing wind direction question!!
Historically, the
prevailing wind direction in Edmonton is from the south
from October through to April, and from the northwest May
through to September.
Claire Martin
Meteorologist
Edmonton, Alberta, Canada
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QUESTION:
What is a clear sky clock? What parameters does
such a "clock" measure?
ANSWER
from Roger Herzler on 4 February 2003:
A "Clear Sky Clock" is an online tool provided
through the skills of Attilla Danko and the data from
Canadian Meteorological Centre. At present this
tool shows the user the approximate cloud cover,
transparency, seeing and darkness for given hours of the
day and locations, such as observatories or star party
locations.
Let's define some
astronomy terminology. The term "transparency"
is how transparent or clear the sky is from the ground to
space. It is driven by moisture and dust in the air.
The term "seeing" is the turbulence of air
currents in the sky which also affects observing,
especially at higher telescope magnification.
The Clear Sky Clock is
designed to predict these observing conditions for
astronomers, which are critical to any observing trip.
It becomes very difficult to turn telescopes to the skies
and see celestial objects if there is cloud cover, or
poor transparency and seeing. Anyone around the
world can request a clock for their own observing area if
a Clear Sky Clock isn't set up for an area nearby.
This is done by getting the observing site's latitude and
longitude, and then following the instructions on the
website.
External links:
Clear Sky Clock Homepage
http://www.cleardarksky.com/csk/
Canadian Meteorological
Centre
http://www.cmc.ec.gc.ca/cmc/htmls/mainpage.html
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QUESTION:
Which websites do you use in your weather forecasts?
ANSWER
from Claire Martin on 27 January 2003:
I use Environment Canada's web site for the numerical
guidance charts. Then I use a "UNISYS"
weather web site - it's a main sorting and collecting web
site for weather information around the world.
There's also a slew of other sites that I use, depending
on the various weather features of the day.
Claire Martin
Meteorologist
Edmonton, Alberta
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QUESTION:
How do I get historical weather data for Fort
Saskatchewan, Alberta?
ANSWER
from Claire Martin on 23 July 2002:
Great question! Here's the scoop.
Environment Canada
considers "historical weather data" a source of
revenue nowadays and as such it is not available (in
detail) on the internet. However, there are still
ways of getting that data .. first the free way! EC
issues pamphlets called "Monthly Climate Summaries"
.. all the country's weather data is published in these
things - they are then sent out to larger public
libraries - the downtown Edmonton Library and the Cameron
Library at the U of A are two good examples. You
can go down and look up (and photo copy) the relevant
data at will. The other (2nd) way to get official
climate data is through the source - EC - itself.
They have a climate services department - you can call
them at 780-991-8881 - but charges apply. The data
- this way - will be collected by a climatologist and
sent out to you directly.
I hope this answers your
question!
Claire Martin
Meteorologist
Edmonton, Alberta, Canada
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