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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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Last Updated:
27 August 2005
 

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