The aim of this project was to investigate what differences exist in temperatures in the local area, and to consider the effects of certain geographical aspects on these.

Simon Barker – Year 11

Geography Coursework

Introduction

The aim of this project was to investigate what differences exist in temperatures in the local area, and to consider the effects of certain geographical aspects on these. This is in relation to the unit of work on Climate, Environment and People contained in the GCSE Geography syllabus, and this project uses principle ideas from this unit of study.

There are many factors that affect the temperature of a region, be they on a grand scale, such as across a country or continent, or in a very small area, where a few environmental differences, such as the shelter of a building or tree, can cause a difference in temperature of one or two degrees Celsius.

On a national scale, the latitude of the location will obviously have an effect, a fact clearly illustrated by the e difference in temperature between a temperate region, such as London, and a tropical rainforest town, such as Manaus in Brazil. This effect can also make a difference on a smaller scale; there is a one or two degree temperature variation between the cities of Portsmouth and London in the UK, which are only 120 km apart.

Altitude is another major factor, as it is generally cooler at higher altitudes than it is at sea level, hence the appearance of snow at the top of mountains at even the warmest of latitudes. This is due to the density of the air, which decreases as the altitude increases. It is therefore possible to have a snow-peaked mountain bordering a hot desert, as is the case with the Himalayas.

The tilt of the Earth, which is the cause of the variation in temperatures by latitude, also causes regional variations in temperature due to the season. In the British winter, places in the northern hemisphere, as the UK is, experience their coldest times of the year, because their part of the planet is tilting away from the Sun, and so the rays of the Sun are less concentrated over the specific area they land upon. However it would be unlikely for an Australian to experience a white Christmas, because Christmas Day in the southern hemisphere falls in the middle of their summer, and one of their hottest months of the year! This is because their part of the planet is tilting in the direction of the Sun, and so it is closer to it and easier to heat up.

A similar reason can be used to explain the variation in temperatures of a place at different times of day. It is generally safe to say that it is warmer in a place at midday than it is at dawn, dusk, or indeed during the night. At the middle of the day, the Sun is at its highest point in the sky, and so the heat it sends out is more concentrated on the point it lands on, rather than being spread out, because it hits the Earth at a great angle, as is the case at dusk. During the night, the Sun is not present in the sky, and so the area experiencing night is cooler than it was during the day, although, warm nights can be experienced, because cloud cover holds the heat of the day in close to the Earth.

Inland places experience different temperatures to coastal towns, suggesting that the distance from the sea is also a factor. In general, inland places experience the greatest ranges in temperature across a year. The distance in density between land and sea means that, as temperatures rise towards the summer, the sea takes longer to warm than the land, and so it is inland places that see the highest temperatures. In the UK for instance, London and East Anglia are normally the hottest parts of the country, owing to the fact they are of a southern latitude, and furthest away from the sea that faces into the prevailing south–westerly winds. However, the sea also retains the heat for longer, and so coastal regions experience the mildest winters, whereas inland places tend to be much colder. Once more using the UK for an example, the South – Eastern coastal places, such as in East Sussex and Kent, experience the warmest winters, as they are shaded from the cold northern winds by other parts of the country, but are warmed by the sea. Across continents, the same holds true. A Siberian summer can be warmer than one here in London, even though it is on a more northerly latitude, because it is so far inland that heat from the Sun simply heats the land, with nothing to absorb the heat, like a sea. However, a Siberian winter is noted for its severity, where temperatures can plunge down into the -20°C.

Cloud cover plays an important part in keeping temperatures up or down, depending upon the time of day. If the sun is out, then the presence of cloud, which absorbs the sunlight’s heat energy, cools the surface temperature. Thus places without cloud are those that are warmest. However, at night, the heat of the day tends to escape. But the clouds, which hold heat close to the Earth and keep temperatures close to the ones in the daytime, can halt its escape.

In temperate island climates such as the one in which we live here in the UK, the wind speed and direction will have a great effect on the temperature. Of course, high wind speeds will lead to a very high wind-chill factor, making temperatures lower, but the direction the wind comes from also has an effect. In Britain, winds from the sea cause relief rainfall, so any rain from a westerly or northerly direction will bring rain. But also, winds from the south carry with them the heat of the south, and the dryness of the European continent. This is why the prevailing southwesterly winds we experience here in the UK cause our unpredictable weather, which is warm for our latitude, but very wet. Winds from the north, which are mostly experienced here in winter, bring with them cold northern temperatures, and also the Arctic rain.

Air pressure is another temperature affecting element of weather. Anticyclones (places with high pressure) bring with them more settled weather, and so, in summer, this leads to clear blue skies and scorching hot days. In winter, this leads to clear but cold days, because there are few clouds to hold in the heat. Depressions (areas of low pressure) bring with cloudy and unsettled weather. In the case of summer, this means cloudy days, and summer storms. In winter, these days are cloudy and sometimes milder, but they can cause stormy weather and strong winds, which drive temperatures down.

Microclimatic Variables

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Microclimatic Variables

Temperatures do not only vary under different conditions across a national picture. On a microclimatic scale, temperatures at sites no more than 5 meters apart can differ by two to five degrees. Shelter, provided by buildings, trees, hills etc., causes a rise in temperatures, because there is not so much particle movement from wind. The inverse is also true, as wind speeds can be greater between two rows of buildings, when they can cause a sort of wind tunnel effect. In a city like Portsmouth, with high rise buildings, it is worth looking out for any of these effects, as some of the areas of the city were designed before the town planners were able to study the effect of wind on high rise buildings, and to plan to counter the effect.

When looking at most mid-latitude European cities, it is noticeable that they are generally warmer by one or two degrees than their rural surroundings – a kind of urban heat island. Buildings and other artificial characteristics of the urban landscape, such as roads, retain and conduct heat more than soil and vegetation, and they release it more slowly. The burning of fossil fuels in homes, offices, and industries and by transport is another major source of heat. Smog and traffic pollution also trap outgoing radiant energy in a sort of mini greenhouse effect, all helping to maintain higher urban temperatures in dense areas of development. Portsmouth is a densely populated and highly developed island, and so it may be worth looking out for the heat island effect as we move closer to the city centre.

Of course, areas in direct sunlight are going to be hotter than those in shade. Aspect – the direction in which a sloped location faces – can also affect its temperature, because the slope facing towards the Sun has no shade or shelter from the Sun’s direct heat, and so is heated not by the air, but by direct contact with the Sun’s heat rays. The shady and sheltered side therefore gives a true reading of air temperature. This will be important to my Portsmouth study, as to the north of the city is Portsdown Hill, and some parts of the city boundary pass over it. It may be interesting to include a site on Portsdown Hill in the study, to see if the result of its aspect affects its temperature.

In a previous experiment in school, a sample of ten sites on the premises showed the surface could affect the temperature readings in a big way. Two surfaces in direct sunlight, less than one metre apart, were used. One was a tarmac surface, and the other was soil. The density difference of the two meant that the densest was the warmest, i.e. the tarmac. Most of the other findings were quite obvious, and a simple set of predictions as to the rank order of the temperatures proved that it was common sense that the microclimatic features mentioned above would affect temperatures.

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This experiment proves that microclimate as well as weather on a national scale would both greatly affect the study I was conducting. Therefore there would be an important element of planning involved in decided what to try and prove in the study, where to go to try and prove it, and how to avoid including too many of the microclimatic variations featured above. I would also have to repeat the tests once, to allow for any experimental deviation in the first set of results, and to allow a possible comparison between the two sets of data.

The latter of the above options seemed to be more attractive, as I thought it would be interesting to compare the ranges of data between two days of different weather conditions, and to see if there was any difference between the two sets of data. Therefore I wanted to try and incorporate this in my project.

Another area that I had to decide upon was what to try and prove in my study. I looked at the options available, and decided that it would be difficult to assess temperature variations at different wind speeds and directions, as this would require either a wind vane and anemometer, both of which I had no access to, and would also take too much time waiting for the right conditions to complete the test in. It would be easiest to take a simple transect of the City of Portsmouth, and see if there were any variations in temperature caused by being further away from the sea. This would be an easy factor to assess using factors on a national scale, but I could also use the different microclimates of the locations to further my study and draw more conclusions.

Planning

To produce a good report, I needed to spend a good deal of time planning how I was going to collect the data required. It was stipulated in the criteria that about 20 sites would be appropriate to produce a good report. I decided that for the purpose

To produce this report on my findings, I collected a sample of data across a range of locations in my local area, the City of Portsmouth. I took a set of 10 temperatures along a north – south transect of the Portsmouth region, from the beach at Southsea, to Fort Widley, at the summit of Portsdown Hill (see map). These temperatures were taken over two different days, in different weather conditions, to give as wider range as possible of variations, so as to demonstrate a wide range of geographical knowledge and understanding within the framework of this report.

Selecting Sites

Having prepared my cross-section of the city, I then had to decide where to take my temperatures. The total length of route was about 4 miles, and I needed to find 10 sites along this line. The obvious choice was to choose one site at the start of the route, and then continue taking temperatures every 0.5-mile. This would leave one site left over, which could be taken up at either the start or finish of the route, to demonstrate the effect of a particular microclimate.

I chose these sites as close to the central line of longitude of the region of Portsmouth as possible, so that variations caused by moving from east to west are not taken into account. However, the sites chosen had to be near to main roads. This is because, if the data is not collected quickly, too much time elapses between the start and finish of the data collection period, and a variation occurs due to the time of day, so I would have to use public transport between measuring stations.

Apart from the odd few, it was advantageous to choose sites with a similar microclimate, so as not to produce misleading results. The readings had to be made as fair as possible and so only variations being tested were ones that really need to be allowed for.

On the map of Portsmouth over the page, you can see the sites I selected.

Breakdown of Places Used

It was important when conducting a study such as this that as many factors as possible which could affect the temperature were considered, and either cancelled out to avoid complexity, or commented upon so that a full picture can be developed. For this reason, I have provided a breakdown of the important features of each site I have used, to indicate if there were to be any variables on a micro climatic scale.

Site 1

Site 2

Site 3

Site 4

Site 5

Site 6

Site 7

Site 8

Site 9

Site 10

These sites incorporate a few of the microclimatic variations that I want to include in my study, as well as being very similar to each other in longitude and situation. Now all that remains is to choose a day to collect the data, and predict the outcomes.

How The Data Was Collected

I decided to start at the most northerly station on my route both times, mainly because it was closest to my home, and therefore easier and faster to access than the point at South Parade Pier (see map). Whatever the conditions were likely to be, the thermometer I was going to use was going to require a few minutes, if not more to acclimatise to the local microclimate. So, upon arrival at each site, I was required to leave the thermometer for two minutes before recording the temperature, and a further temperature was recorded two minutes later.

Forecast Weather Conditions

MET Office Online Forecast on Wednesday 17th July

As mentioned previously in the introduction, I wanted to collect temperatures on two days with different weather conditions. I watched the BBC weather forecasts every evening, waiting for days when the conditions would be right to conduct my measurements, and for a convenient time to do them. I also downloaded local weather forecasts for Portsmouth from the MET Office web site. On Wednesday 17th July, the forecast showed a possible time to conduct the tests.

Friday afternoon was expected to be hot, sunny and dry, with a maximum temperature of 28°C. Saturday was expected to be dry but overcast, with sunny spells in the morning, and highs of just 23°C. This was, however, just a forecast, and so I planned to perform the tests on those two days, subject to the weather changing from the forecast.

Collecting Data

General Weather Conditions

BBC News Forecasts at 6:20 on the respective mornings.

Below is an outline of the general weather conditions on the days the data was collected.

These conditions were the exact same conditions in which I collected the data on both days. There were no problems with rain, and the conditions themselves allowed for a small degree of flexibility in my readings, as, on Friday it was important to find shade to obtain the air temperature, and, on Saturday, the clouds provided the shade.

I was also able to obtain the temperatures at roughly the same time in each test, and in a satisfactorily short amount of time, so that time of day was not a major factor in the expected temperature variation.

Expectations

In order to demonstrate a full understanding of the causes of temperature variation, I will now try to explain what I expect to find in the results, what trends I expect to surface, and why.

I would expect that the distance from the sea would have an effect on the temperature, as explained in the introduction. Due to the summer time of year, I would expect that the temperatures will increase as we move further away from the sea, and so be at its highest when we reach the end of the route.

I will be looking out for a possible urban heat island, which could well occur between sites 3 and 6, as we approach some of the most densely populated area of the city, and indeed some of the most densely populated areas in the country.

I could possibly find that there is a temperature variation with altitude, although the actual variation may be negligibly small, due to the fact that the height of the hill at the end of my route is actually not very high – it is only ___ metres above sea level.

Due to the nature of the first two sites, I would expect that site 1, the site on the beach, would be a bit cooler than site 2, the site on the promenade above. The first site is on beach stones and sand, which does not heat up as easily as the pavement slabs of the second.

Table of Results

Interpretation and Justification of Results

Having collected and displayed the data, it is now time to attempt to justify them, and interpret any patterns that appear in them. In simple terms, there are a few collective and generalised statements one could make about the results I have collected.

As we move further north, and therefore further away from the sea, the temperatures increase.
The site on the beach, the first, is one or two degrees cooler than the site on the pavement above it, even if they are the same distance from the sea.
The site in direct sunlight, site 10, is warmest by over a degree.
The site at the highest altitude, also site 10, is the warmest.
The temperature range on Saturday is greater than the temperature range on Friday.

1). In my experiment, I was taking temperatures over a north - south transect of the Portsmouth island. I predicted that the coolest area was going to be that nearest the sea, and the results clearly show that this is the case. As we move further away from the sea, the temperatures get warmer, until we reach the Fort Widley location at the top of Portsdown Hill in the north, where the temperatures are warmest.

These results were collected in July, the height of the British summer months. In the summer, the temperatures in Britain vary in different ways to the winter. The sea is a major factor in this. Water in the sea is less dense than the land it borders, or, to put it another way, the particles are further apart. This means that heat from the Sun takes longer to conduct from one water particle to the next and heat it than it does on land. The inverse is also true, and so the sea will retain heat for longer during cold winter months. For the duration of winter, the seas retain some of their heat, and so the coastal regions of the south – west are the warmest. As the temperatures warm up, the sea takes longer to warm up, and so the coastal regions close to the prevailing winds remain cooler, and the warmest places are inland in the east, opposite the prevailing winds.

2). As expected, the first site was one degree cooler than the second site, even though they were at the same distance from the sea. This too was what I expected to see. The stones and sand on the beach are less dense than the pavement of site two, and so it is less susceptible to being heated than the pavement, and so it is cooler. Also, in terms of direct distance to the sea, the first site is actually closest, as it is on the beach, at sea level, compared to the promenade, which is a few metres above sea level, and sheltered from the southern winds. In fact, the true difference is probably more than one degree, because the first site was not in any sort of shade, which increases the temperature, as you will see with the next point.

3). As stated at the beginning of this project, in the Microclimatic Variables section, the effect of direct sunlight on the temperature compared to sites in shade is obvious. Therefore it comes as no surprise that site 10, which is in direct sunlight, is the warmest of the sites. The site is warmest because, with the thermometer used to measure the temperature in no shade, the sun’s heat rays are heating up the mercury inside the thermometer, rather than the air around it, and so the reading is exaggerated from the real air temperature. Therefore, I would expect that the true air temperature would be at least one degree lower, and this proves the effect of this particular microclimatic variable.

4). As you can clearly see from the graph titled Comparing Altitude and Temperature, the warmest site was also the one at the highest altitude. However, I have my reservations as to whether this relationship, although positively confirmed by the graph, is actually a true reflection of the relationship between altitude and temperature. One would normally expect that, as the atmosphere becomes thinner at higher altitude, the temperature would be lower. Perfectly obvious observations, such as comparing the temperatures in the Himalayas with temperatures on similar latitudes in neighbouring India and China, prove this two be the case. However, the results of this study totally contradict this.

The explanation for this oddity is the microclimate of the sites at different altitudes. The first site as mentioned previously in point 2) of this section, was the coolest for reasons of microclimatic variation, namely the surface of the site compared to ones of similar altitude. The final site, for other microclimatic reasons, namely the direct sunlight, was the warmest. Also, the altitude of the sites slowly increases as we move through the sites and move northwards across the island. Therefore, I would conclude that the idea that, as altitude increases the temperature also increases, is a mis-justification, and therefore, I will conclude that this generalised result is null and void.

5). The temperature range on Saturday is greater than that on Friday. This is a fact proved by the results, but it is doubtful that this is a factor related to the weather. The temperature range is merely a statistic based on two different experimental observations, and so the margin for error is only ¼ of a degree. Therefore I believe that this is nothing more than an experimental deviation, and I am paying no real attention to this result.

There is one factor that I was looking for that I didn’t actually find any evidence of in my study. I stated in my section entitled Expectations, that I was looking out for a possible urban heat island, which I believed could occur as I approached the most densely populated areas of the city, i.e. those between Sites 3 and 6. I was initially surprised not to see such an effect in my study. However, I believe I can find an explanation as to why this effect did not surface in my results.

The greatest effect of an urban heat island is found close to the Central Business District of a city, with the highest proportion of high-rise buildings and the most traffic jams and people, which generate heat. The CBD of both Portsmouth and Southsea is located on the southwest of the island. These are marked on my map in the planning section of this report. Because of this, the route along which I collected my results did not include the CBD, and therefore I would not expect the heat island effect to be so great. There was, however, a rise in the first temperature recorded at site 5 on Friday, which is geographically near the centre of the island, and essentially very close to the very densely populated region of Buckland. I will conclude from this that there is some effect caused by proximity to the CBD, although on the days the results were collected, it was not great enough to be noticed by the results table.

Evaluation

The aim of this project was to investigate any differences or variations between temperatures in the local area. Using the range of sites I chose, with a variation in microclimates, I have discovered that there is a variation in temperature related to distance from the sea, as well as many microclimatic variations that I included, such as the effect of a different surface, and of direct sunlight

In relation to the aim of the project, I believe I have fulfilling the aim. I believe that I chose two good days on which to take the temperatures - two consecutive days with slightly different weather conditions - but still reflecting the general pattern of weather in the UK in summer. There were no obvious deviations from the general pattern of things, and no anomalous results. I believe that some of the general interpretations I made from my results were not truly justified by the results, and I believe I gave reasons for this in my Interpretation. I will regard this project as a success, and it would be interesting to repeat the study again, under similar conditions, but centralising on a particular type of temperature variation, with more sophisticated equipment than just a thermometer, so I can draw more detailed and founded conclusions.

Bibliography

Warburton, Paul Atmospheric Processes and Human Influence