Uploaded on 2017-03-08 by Phil Jones

Finding data and information about the urban heat island effect of UK cities and towns is problematic. It appears that there has been little study published on the subject outside of London. As I don't know London I can't discuss it here to give reasons as to what may contribute to the UHI effect, nor is it local to my home. Plymouth, Devon, is listed in one of the articles I found, which is the closest of these cities to where I live. It's not a city I know well nor is it sufficiently close that I can visit to take photographs. My own town of South Molton, which is actually some 2.5 miles north of my home, has neither data, a weather station nor sufficient roads and buildings to have much of a UHI effect. It is also surrounded by open countryside. The two articles I have found differ in that one selected cities by size of urban centre. The other uses Met Office weather stations which are located at various sites but not necessarily within cities, rather at airfields and other locations. For the purpose of this exercise I shall compare Plymouth and South Molton as they meet the requirements of being a local city with its rural counterpart. Plymouth lies approximately 46miles or 75km south west of South Molton. Plymouth is situated at mean sea level rising to 155mtrs amsl whereas South Molton is some 130mtrs amsl. Topography has a major influence on the two locations. Plymouth has the high rising Dartmoor plateau set behind it and faces into the prevailing winds of the western English Channel. It is a large university city with an ancient port and a mix of buildings. South Molton sits in an east-west valley formed by the river Taw at Barnstaple and the river Yeo that runs along the southern flank of Exmoor. The land rises on the northern, southern and eastern sides. It is a medieval market town that has little in the way of modern architecture, mostly dating from the late 1800s and early 1900s. Plymouth is a built up city of around 31 square miles with the main centre being close to the coastal location around the historical naval and maritime centres. Population is in excess of 262, 000. [2011 census] From the data collected by Kershaw et al [1], the mean annual heat island for Plymouth calculated over the years 2002 - 2006 is 1.1 Celsius. That places the city as number 8 in the UK with 1.9C being the highest and 0.1C the lowest of the 21 cities meeting the selection criteria. It is interesting that Plymouth should rank so highly in comparison to cities that are much larger in size and population. The summertime temperatures are comparable with much larger cities such as Manchester and Bristol all of which shared a figure of 1.2C. Plymouth's south sloping aspect and the relative shelter from the east, west and north clearly add to the amount of heat that the city surfaces can absorb during the day. The proximity of the sea and the adjacent river Tamar, the high moorland to the north and the very rural and open country surrounding the city must also have a cooling effect. The old parts of the city date from several hundred years ago but a lot of this was destroyed during the bombing of WW2. There are some very modern buildings and the old parts are mixed amongst the new. The main shopping and commercial centre was built after the war and is mostly concrete structures with some wide canyons landscaped with trees and some grassed areas. There are very few tall buildings by modern city standards. Parts of the city contain many densely packed streets that are only able to allow cars to travel in one direction and mostly the roads are just capable of carrying two way traffic but not large goods vehicles. There are some major roads passing through the city which carry large volumes of traffic, especially during the summer months when visitors pass into and through the city. The main road, the Devon Expressway, runs straight through the city east to west, carrying traffic to and from the county of Cornwall. Within the city there are large wooded coombes or valleys and many parks and green areas. The areas east and north of the city are most developed with modern buildings and large housing estates. I would think that the position of Plymouth as the most southerly large city in the UK, the prevailing weather patterns and the relatively sheltered location are more contributing factors to the heat island effect than the actual building layout or any anthropogenic additions. South Molton is a rural market town of less than one square mile with most residents living around the central square or in housing built on the western side. The population is around 5,000 [2011 census] There is no weather data for South Molton as there is no weather station here. The minimal amount of hard surfaces, the low height of buildings and the immediate surrounding open countryside will be contributing little to any heating of the town. There is only one main road through the town and it is generally quiet apart from market days. It still closes half day on Wednesday and Saturday, something unheard of in most modern towns. reference: [1] (Estimation of the urban heat island for UK climate change projections, Building Services Engineering, Research and Technology 31 251-263 (2010)) ----------------------------------------------------------------------------------------------------------------------------------------- In any situation where new building is concerned, the planting of green spaces, trees and shrubs is without doubt the best way to contribute to the liveability and climate. There can be very few humans who have a total aversion to sitting on a grassy area or under a tree especially during hot weather. At street level the shading given by trees offers a comfortable zone to move through. Even vehicles benefit from moving through cooler air. The effect of transpiration from living surfaces adds additional cooling to the shade given which in turn cools upper layers of the atmosphere within the city. Trees can improve the way wind reaches the lower street levels diminishing some of the effects caused by the canyons between buildings. Proactive planting design and careful consideration of how buildings create turbulence can lead to areas that are uncomfortably effected by wind being made much more tolerable. Covering buildings with plants at any scale not only gives shading to the structure but adds surface texture that takes energy from wind. Green roofs provide pleasant habitats for a diverse range of life whilst reflecting some heat and converting some to further growth and again the effect of transpiration not only cools the atmosphere around the roof but can also assist in cooling the internal space of the building. Where existing cities are concerned the adoption of as many additional green areas should always be considered as an improvement to the liveability and to the shading and cooling effect in the primary habitation zone. In many cases it is possible to upgrade roof areas to sedum lawns with no major structural addition. Often the roof areas of buildings can be made into desirable park like areas suitable for recreation such as dining, theatre or small scale urban farming such as bees. Many such examples already exist and the feasibility for most cities to improve their habitat by incorporating as many plants whether ornamental or food crops is something that should be a priority at the most basic of planning levels. In temperate cities the use of deciduous trees and plants can assist by allowing surfaces to heat up during the winter period when the additional heat island helps to improve the climate. Where water is an issue in warmer climates, there is a strong case for using waste water to irrigate urban planted areas. Selection of tolerant species is more applicable in these circumstances as effects of salination and nutrient build up in the soil can harm some species. There has been plenty of study of this subject and data is available that can enable the choice of plants that not only tolerate such conditions but can also assist by removing harmful materials from the environment. ==================================================================================================================================== The only reference to UHI is under the section sustainability in the North Devon and Torridge Local Plan 2011-2031 “In the built up areas of northern Devon, strategic green spaces will also be important in minimising the urban heat island effect and as functional flood plain to mitigate against flood risk” There are no visible results as far as I am aware. On the contrary. Several open areas between existing housing are being developed for new housing taking open green areas and permanently burying them under standard design modern housing. Existing recreational areas have begun to be developed despite strong local objection. ............................................................................................................... the image attached is all I have on my computer that is neutral. I can't travel to Plymouth to take a photo and at present can't get to South Molton to do the same. There is only one image permitted to be uploaded here and requests for advice refer me to answers not relating to this matter. I apologise for being too dim to understand this technology. I am fairly new to it and there is no one to teach me. Maybe if you published some better information would help. It seems pretty stupid to ask for two images but only permit one to be added.