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Questions for Claire

Archives: September

Is the weather different around urban cities, or centres? If so why?

Wednesday, September 30, 2009 | 09:33 AM PT

Question submitted by Curtis Bennett
(Kelowna, BC)

This is a great question Curtis, and the answer is "absolutely"! The effect is known as the Urban Heat Island (UHI) effect.

An urban heat island (UHI) is a metropolitan area which is significantly warmer than its surrounding rural areas.
http://i.treehugger.com/files/th_images/urban_heat_island.jpg
The observed temperature difference is larger at night than during the day, and is most apparent when winds are weak. Seasonally, UHI is seen during both summer and winter. The main cause of the urban heat island is modification of the land surface by urban development which uses materials which effectively retain heat; waste heat generated by energy usage is a secondary contributor. As population centers grow they tend to modify a greater and greater area of land and have a corresponding increase in average temperature.

Monthly rainfall is greater downwind of cities, partially due to the UHI. Increases in heat within urban centers increases the length of growing seasons, and is even thought to potentially decrease the occurrence of weak tornadoes (more research is needed for thorough confirmation). Increases in the death rate during heat waves has been shown to increase by latitude due to the urban heat island effect. The UHI decreases air quality by increasing the production of pollutants such as ozone, and decreases water quality as warmer waters flow into area streams, which stresses their ecosystems.

Not all cities have a distinct urban heat island, however. Mitigation of the urban heat island effect can be accomplished through the use of green roofs and the use of lighter-colored surfaces in urban areas, which reflect more sunlight and absorb less heat. Despite concerns raised about its possible contribution to global warming, any impact of the urban heat island on global warming is uncertain, its impact on climate change has not been proved observationally or by any quantitative modelling, though recent qualitative speculations indicate that urban thermal plumes may contribute to variation in wind patterns that may itself influence the melting of arctic ice packs and thereby the cycle of ocean current.

Are dust storms in Australia really that unusual? Is this another sign of climate change?

Wednesday, September 23, 2009 | 01:25 PM PT

Question submitted by Mi-Young
(Williams Lake, BC)

Good question Mi-Young! Simply put the answer to both questions is "no"!

The Australian Bureau of Meteorology has a great discussion on the web on this subject at http://www.bom.gov.au/lam/climate/levelthree/c20thc/storm8.htm

Dust-storms are for the most part restricted to the drier inland areas of Australia, but occasionally, during widespread drought, they can affect coastal districts. The figure below shows the average distribution of dust-storms over Australia. One of the most spectacular examples was the storm that swept across Melbourne in February 1983, late in the severe El Niño drought of 1982/83. The extended dry period of the 1930s and 1940s generated many severe dust-storms, culminating in the summer of 1944/45 when on several occasions dust in Adelaide was so thick that street lighting had to be turned on. But uncomfortable as dust-storms may be for town and city dwellers, by far their worst effect is the stripping of topsoil from Australia's arable land.

Remember also that any one single event, as far as the daily weather is concerned, is never an indicator of "global climate change". Climate change will occur on a far greater scale. However a series of single events, that appear to become "the new normal" is most definitely an indicator that our weather patterns, and hence climate, is changing.

Why is the equinox date not the same each year?

Monday, September 21, 2009 | 01:14 PM PT

Question submitted by Mike
(Salmo, BC)

While the September equinox occurs on September 22 in 2008 and 2009, it occurs on September 23 in 2010 and 2011 (UTC). The September equinox has also occurred on September 24(UTC), with the last occurrence on that date being 1931. The next time a September 24 equinox occurs will be in the year 2303. Moreover, a September 21 equinox will occur in 2092.

There are a few explanations on why the equinox dates differ in the Gregorian calendar. The varying dates of the equinox are mainly due to the calendar system – most western countries use the Gregorian calendar, which has 365 days in a year, or 366 days in a leap year. According to the National Maritime Museum, the equinoxes generally occur about six hours later each year, with a jump of a day (backwards) on leap years. An extra day is added in a leap year to minimize a gradual drift of the equinox date through the seasons.

As for the tropical year, it is approximately 365.242199 days, but varies from year to year because of the influence of other planets. A tropical year is the length of time that the sun takes to return to the same position in the cycle of seasons, as seen from earth. The exact orbital and daily rotational motion of the Earth, such as the “wobble” in the earth's axis (precession), also contributes to the changing solstice dates.

What is a meteorologist? What exactly do they (you) do?

Monday, September 14, 2009 | 10:44 AM PT

Question submitted by David
(Terrace, BC)

I get this question a lot, David, so I thought I would answer it here!
While many people know a meteorologist is a person experienced and trained in meteorology or an atmospheric science, many viewers still want to know several questions about meteorologists.

What Does a Meteorologist Do?
What Are the Types of Meteorologists?
How Can I Become a Meteorologist?

A meteorologist is a term often used to describe anyone who studies meteorology. Popularly, any weather reporter on television is often called a meteorologist, but that is not always the case. In 1990, the American Meteorological Society set an official description of a meteorologist.

A meteorologist is an individual with specialized education who uses scientific principles to explain, understand, observe or forecast the earth's atmospheric phenomena and/or how the atmosphere affects the earth and life on the planet. This specialized education would be a bachelor's or higher degree in meteorology or an atmospheric science. Individuals who have little formal education in the atmospheric sciences, or who have taken only industry survey courses, and who disseminate weather information and forecasts prepared by others, are properly designated weathercasters.

Furthermore there are many types of meteorologists:
Meteorologists work in a range of fields each with a specialized area of study. Essentially, a meteorologist is a specialized scientist that focuses on some aspect of the atmosphere. The following list shows just some of the types of meteorologists.
Broadcast Meteorologists: These folks are the people who interpret and report the weather for television.
Research Meteorologists: Many of these scientists work for the National Weather Service or other government agency. NASA, the Environmental Protection Agency, and the military. Most have a particular issue they are studying.
Teachers and Professors: Many people use their knowledge of the atmosphere and meteorology to become educators. Sharing your knowledge at a high school or college level can help to create future generations of meteorologists.
Forensic Meteorologists: This type of meteorologist will often investigate claims for insurance companies on past weather or research weather for a court of law.
Consulting Meteorologists: Large companies now hire meteorologists for consultation work. Companies such as Liz Claiborne, M&M Candies, and Target all hire meteorologists to improve their buying and selling power.
Climate Meteorologists: This type of meteorologist looks at long-term weather patterns and data to help predict future climate trends and past climate data.
Archive Meteorologists: Many weather scientists will also be in charge of researching, verifying, and reporting on storms of the past.

It's a fun and fascinating science, and I love working in this field.