Ecology Elective Course Essay

Fredrik Venold

What causes the seasonal temperature changes in Oslo

Introduction :

The seasonal changes in temperature in Oslo, have a huge impact on the population living there, as during the winter, reduced movability and lack of agricultural production may be observed. The aim of this essay is therefore to prove that there is a direct correlation between the sunrays angle of incidence and the average montly temperature. All other factors have not been taken into consideration as the sun is the most important factor leading to heat production, in the form  of solar energy. It is well known that the Gulf Stream is another key element, as neighbouring countries, meaning those at the same latitude, are colder, and experience longer cold periods.

Facts :

 1. Cause of seasons

The cause of the seasonal alterations is “ the angle of the earth’s axis in relation to the plane of the ecliptic. This causes the seasons and the changes in the height of the sun above the horizon. This therefore controls the intensity and duration of sunlight received by locations on the earth”. As this then causes the difference in angle between the earth’s surface and the sun, the angle of incidence for each ray of light also changes.

2. Distance between sun and earth

If one was to calculate all waves, there would also be a need to know the distances of each side of the triangles. “As the earth moves in an elliptical cycle around the earth, the average distance of the earth from sun over a one year period is 150 million kilometres”.

But as I am only considering one point on the earth’s surface, and the distance is so great, only the angle of incidence is taken into consideration.

3. Seasonal terminology :

To be able to explain the movement of the earth, there have been designated four terms to that of the suns presence.

1. The earth moves around the sun and never opposite as earlier believed. “The celestial cycle takes 365 ¼ days to complete one cycle”.
2. During this cycle, “the summer solstice (June 21-22), the north pole is tilted 23,5 degrees toward the sun.
3. On December 21-22 , the winter solstice, the South Pole is 23,5 degrees to the sun.
4. “Vernal Equinox (September 22-23) and autumnal equinox (march 20-21)is when neither pole is tilted the sun. Day lengths on both these days, regardless of latitude, are exactly 12 hours”.

4. Angle at which the solar radiation hits Oslo

The angles of sun to a point in Oslo may be described as fallows:

“The annual change in the relative position of the Earth's axis in relationship to the sun causes the height of the sun (solar altitude) to vary in our skies. The total variation in maximum solar altitude for any location on the Earth over a one year period is 47 degrees (2 x 23.5 = 47). For example, at 50 degrees North maximum solar altitude varies from 63.5 degrees on the summer solstice to 16.5 degrees on

the winter solstice “.

5. Energy absorption

The next part unit after the angle of incidence needed, would be the energy received from 1 unit of light. “The sun emits energy in the form electro-magnetic radiation. We see this as light, feel it at infra-reed waves as heat, and becomes tanned by UV”.

If one therefore was to simplify the calculation, using only angle of incidence and the assumption that at

-        90 degrees there would be complete absorption (100%), and at

-        90 degrees there would be 0% absorption,

something there is not, one would see the fallowing for a city as Oslo, which is located at 59 degrees latitude ( I simplify this by rounding it up to 60.

If one then compares it to the annual average temperatures taken from Norway’s Meteorology institute, they seem to correlate rather well.

Conclusion :

As this has shown, there is not just a clear theoretical correlation between the suns angle of incidence to the earth and the average temperature, but also in reality. If one was to compare it to another city, closer to the equator, as Budapest, it therefore only reasonably that the climate is warmer, as the angle gets closer to 90 degrees.

Even in more advanced measuring, as the one below, one may see the same tendency as described above.

IF one was to further complicate the temperature evaluation of Oslo, one would also need to take the Gulf stream and the average atmospherics absorption/filtration, as this has proven to be a filter for the suns emitted light, thereby greatly limiting the amount of energy reaching the earth. If this is an equally important factor during all angle of incidence is unknown to me, so would require further investigation.

Sources :

1.     Webpage : http://atschool.eduweb.co.uk/kingworc/departments/geography/nottingham/atmosphere/pages/solarradiationalevel.html

2.     Webpage :http://www.geog.ouc.bc.ca/physgeog/contents/6h.html

3.     Webpage : www.ssb.no (Statistisk Sentralbyrå)

4.     Webpage : www.met.no ( Norges Meterologiske Institutt)

5.     Webpage : http://bio.univet.hu/SALVE/ecol/wildlife/w_02_bioms.htm (Bioms, lecture notes by Peter Kabai)