By Alan Rogers
IN 2007, the United Nations (UN) Demography Unit declared that half of the world’s population lived in cities or large urban areas. With a Malaysian population growth rate of 1.78 per cent per annum (2006 data) and urban population figures quoted for Sabah and Sarawak at just over 48 per cent in 2008, it seems inevitable that in our next census this July that both states will match the UN figures of 50 per cent urban dwellers. With estimated populations of 635,000 and 560,000 in Kuching and Kota Kinabalu respectively, these cities are now making their own microclimates.
A fascinating book ‘The Climate Near The Ground’, written in German by Professor Dr Rudolf Geiger of Munich University, was published in 1934 followed closely by Dr Franz Kratzner’s book ‘Das Stadt Klima’ (The Urban Climate). Both valuable sources were lost to World War II and translated rather crudely into English now some 60 years ago.
It was only in 1965 that a lecturer at UCL London University, Tony Chandler — later to become Professor of Geography at Manchester University and eventually Master of Birkbeck College London — published his paper on ‘The Climate of London’, using the term the urban heat island, which allegedly was first coined by the father of British Meteorology, Luke Howard, in 1810!
Chandler criss-crossed London in a battered Land Rover laden with meteorological equipment in high pressure conditions by night and day in the summer and winter months. He monitored the temperature, relative humidity, and wind speeds in various locations. Later, he persuaded 60 schools, teachers’ training colleges and individuals in the Greater London area to set up their own weather stations and to send their results to him. What did he find?
He observed that the temperature differences between the centre of a city and its suburbs and rural surroundings were greater at night. The buildings and built up areas absorbed heat by day and released that heat by night. This was due to the heat retaining capacity and thermal conductivity of concrete, brick and tarmac peaking in the Central Business District with the high rise structures acting as giant convector heaters.
Urban canyons existed between buildings trapping pollutants from traffic, which absorbed heat as well as held in heat from summer air conditioning systems and winter central heating units. Industry added to the heat build up with its thermal plumes adding pollutionand dust particles into the air absorbing heat.
Thus the temperature of Central London was several degrees higher than the suburbs. The tall buildings also acted as windbreaks and wind speeds in the centre of the city were much lower than in the rural outskirts. In summer anticyclonic weather, he noted that the frequency and ferocity of thunderstorms were greater in the city centre than on the outskirts or in the numerous London parks. Why? Heat generated by the buildings by day was released at night as giant thermal convection currents into the surrounding atmosphere. Hot air rises, cools and condenses.
In July 1976, I witnessed, standing on the North Downs some 80km from the centre of London, the very best natural fireworks display for four hours during the night when sheet and bolt lightning illuminated the sky with torrential rain hammering down on the City of London. I was dry but flooding occurred in the city. How can all this be applied to our tropical/ equatorial climate only a couple of degrees north of the Equator here in Kuching? Why do we get rain in the centre of Kuching when say Tabuan Jaya and Petra Jaya are bone dry? Every city makes its own climate and Kuching can be no exception to this.
Hypothetically our overall climate is much the same throughout the year with seasonal exceptions perhaps becoming less noticeable as climatic change worldwide takes its toll. There are however variations in our temperatures, relativehumidity, and rainfall inputs on an hourly and daily basis depending on where we live in Greater Kuching. A theoretical transect of temperatures by day and by night may look like what’s shown in the diagram. What are the hourly temperatures, rainfall figures and wind speeds like at Universiti Malaysia Sarawak (Unimas) along Samarahan Road as opposed to those at Swinburne University of Technology and INTI College? What are the same for Buntal or Santubong with the moderating effects of land and sea breezes?
Are the temperatures north of the Sarawak River in the lower density housing schemes there any different from those south of the river in higher density areas?
What of the microclimates of say Sama Jaya Forest Park and Reservoir Park, compared with centralKuching. Perhaps we need to know how increased urbanisation is affecting our local microclimate. Haze hoods exist in most cities largely through a combination of pollution and temperature inversions — but that’s another story!
Let’s mobilise our observant school and university students by setting up weather stations on their campuses. Certainly this can be done cheaply with electronic recording gadgets and data logging devices. Such findings could be reported by email to the local Meteorological Department office.
Thank goodness for the urban planners in Kuching, as most high rise buildings are seldom concentrated together and thus concrete canyons are avoided. Long may this continue despite high land values near the city centre. We should thank our city councillors both north and south of the river for our parks and the greenness of much of the city. Those trees cool down our urban climate through the process of evapotranspiration and act as urban lungs in absorbing carbon dioxide as well as other gases and releasing oxygen into the air.
We have so much to be proud of but we can still be better. Kuching could be marketed on the tourist front as one of the greenest cities in Asia much as Shenzen, the garden city, is marketed in China.
The next time you are driving in or out or through Kuching, turn on the outside automatic temperature recorder in you car and quietly monitor the changes over a few kilometres. You will be pleasantly surprised!
No comments:
Post a Comment