|
|
|
Temperature Research
Page
|
Research Question: How and why does the mean monthly
temperature change each month and from year to year?
Background Information on Surface Water Temperature
Water in the Juan de Fuca strait is consistently cold
throughout the year. This is, in part, due to the exposure
from the cool Pacific Ocean as well as the strong tidal
currents that pass through Juan de Fuca twice daily,
and from the upwelling of water from below.
|
|
Below 10 metres the water usually never rises above 12 çC,
even during the warmest summer months. And, in the winter,
it usually varies between 6-8 çC.
Around the month of March, colder ocean waters with temperatures
around 6-7 çC start to penetrate up the channel along the bottom
of the Juan de Fuca Strait, but the surface temperatures remain
below 10 çC. Surface temperatures begin to change when the
runoff from the rains enters into the Fraser River and dumps
into the strait. Most of this water, which may warm to
over 20çC works its way southward through the eastern basin
of the Juan de Fuca Strait. A result of the tidal mixing of
warm fresh water with the colder salt water is warmer water
overall.
In some places where there are patches of water that are relatively
unaffected by the tides, the water can start to heat up and
by mid-August, some shallow areas can reach 12-14çC, even though
the bottom will remain cold. This temperature difference
is called a thermocline.
Surface temperatures then start to diminish again in September
when colder water enters the strait combined with enhanced
wind activity and reduced solar radiation. These factors tend
to lower surface temperatures from about 4 çC.
|
Since 1921, with the exception of a few years off during
the second world war, the surface water temperature has
been taken daily. This information is now posted on the
web. Considering what you have read above, what do you
think has been the mean temperature for this month during
all those years?
|
|
| |
Mike, the guardian
of Race Rocks, takes the daily temperature and temperature
readings.
|
Let's check out the mean monthly readings
for the past 80 years and see what has happened over time.
- Open
an excel spreadsheet and label it RaceRockstemp.xls
- Go
to the temperature
information page.
- Highlight
the temperature data and copy it
- Paste
the information into the cells on the sheet. Each month should
have its own column.
- Do
an edit-replace and delete all the 99.9 numbers and replace
them with a blank space.
- In
the far right hand column, determine the average mean annual
temperature for each year.
- Graph
the results.
- Answer
the following questions:
- What is the maximum
and minimum mean annual temperature?
- What is the range
of mean temperatures?
- Why would the
mean temperature change from year to year? (Think globally!)
- In
the bottom columns, graph the monthly mean temperature measurements
for the months, over all the years.
- Graph
the results.
- Answer
the following questions:
- During what months
is the temperature highest?
- During what months
is the temperature lowest?
- What is the
range in temperature?
- Why would mean temperature
levels change from month to month in this area?
|
