The aim of this Fieldwork is to investigate urban heat islands (UHI) in So Paulo’s CBD1 and analyze to what degree “Parque da Luz” influences on them.According to David Waugh, urban heat island is a metropolitan area that is warmer than its surroundings.
It persists during the night because of the availability of heat stored in the ground during the day-time hours, and during winter because of the use of heaters.Other reasons are Changes in the thermal properties of surface materials and Lack of evapotranspiration in urban areas. These materials (concrete and asphalt) have significantly different heat capacity, thermal conductivity and surface radioactive properties (albedo2 and emissivity3) than the surroundings.
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The lack of vegetation in urban areas eliminates the natural cooling effects of shading and evapotranspiration.Tall buildings within urban areas provide multiple surfaces for the reflection and absorption of sunlight, and it inhibits cooling by convection.Besides these effects, UHI can produce secondary effects like altering wind patterns, the development of clouds and humidity.According to Magda Lombardo, ever since So Paulo started growing, the average temperature went up 1,5C.The lack of vegetation and parks is one of the biggest reasons for urban heat island growing in So Paulo. It is estimated that only 3% of the territory are covered by vegetation.”Parque da Luz” was chosen because its location provides us a great example of urban heat island in So Paulo. We can see through the map 1 (page 3), that this park is located in the middle of So Paulo’s CBD.
As UHI can be diminished by reforestation, we can analyze if “Parque da Luz” is helping to diminish the urban heat island in So Paulo’s CBD.”Parque da Luz” is the oldest public park in the city; it was inaugurated in 1825 when it was called “Jardim Botnico da Luz”.For this Fieldwork the following Research Question was elaborated:To what extent does “Parque da Luz” influences the heat islands within So Paulo’s CBD?This question focus on the solution for urban heat island, we have to answer if “Parque da Luz” is helping or not to diminish UHI in So Paulo’s CBD.Because of that my hypothesis is:Further the place is from “Parque da Luz” warmer it is, therefore the park helps on diminishing UHI in So Paulo’s CBD.This answer will be proven right or wrong in the Conclusion but my point in this hypothesis is that the park does help the CBD urban heat island problem because it seemed that further the place is from the park, warmer it becomes.MethodologyWe read about UHI, after it we organized our plans and divided ourselves in 3 groups to collect datas from the three different places, which are: “Parque da Luz”, “Estao da Luz” and “Estao Jlio Prestes” (these places can be located on the map 1 and photos can be seen in the Attachements).With this map, we can understand the distances between the Fieldwork Places:- “Parque da Luz” to “Estao da Luz” is 193,39 meters.
– “Parque da Luz” to “Estao Jlio Prestes” is 772,93 meters.- “Estao da Luz” to “Estao Jlio Prestes” is 602,82 meters.Map 1 – The three places studied:Source: Google Earth Author: Teresa P. NogueiraA list was made of the chosen items to be analyzed and measured every 15 minutes from 9:45am until 3:45pm (with one hour break for lunch at 12pm) on the work places.
The items measured were (see more details in the Attachements):* Time* Temperature from dry bulb* Temperature from humid bulb* Temperature of the ground* Cloud coverage* Type of clouds* Wind intensity* Wind direction* Atmospheric pressure* Car Flux* Thermal sensation* Relative Humidity* Altitude* Level of constructionThe colour, texture and materials of the constructions, season of the year are also factors that influence UHI but we did not focus much on that.The data collected was treated by making tables and by its higher influence and importance.Presentation and analysis of the DataTo have better results to answer my Research Question and prove that my hypothesis was right or not, I will organize the data collected in graphs and tables on this chapter.The table below is the average of the most significant measurements collected during the fieldwork. With this table it is possible to observe the differences from the three places studied.”Estao da Luz” is the hottest place comparing to the other two, and “Parque da Luz” is colder.
Table 1 – the average from different datas on the three placesPlaceParque da LuzEstao da LuzEstao Jlio PrestesDry bulb temperature24.726.025.8Humid bulb temperature20.623.322.
1Ground temperature22.428.222.6Atmospheric pressure933.1933.1933.
1Car flux0.121.4108.5Thermal sensation23.024.823.7Relative Humidity77.
181.372.6Source: Fieldwork Author: Teresa P. NogueiraThe graphs 1, 2 and 3 below are used to show the difference from the real temperature to the thermal sensation in each place studied.It is possible to notice that the thermal sensations in “Estao da Luz” and “Estao Jlio Prestes” are lower than the dry bulb temperature, around 2C below.In “Parque da Luz” the thermal sensation is closer to the dry bulb temperature, because of the trees and shadows.Graph 1 -Source: Fieldwork Author: Teresa P.
NogueiraGraph 2 -Source: Fieldwork Author: Teresa P. NogueiraGraph 3 -Source: Fieldwork Author: Teresa P. NogueiraThe graph number 4 demonstrates the evolution of the dry bulb temperature on the three studied places during the day.Graph 4 -Source: Fieldwork Author: Teresa P.
NogueiraComparing graph number 4 with the graph 5 below, which has the average dry bulb temperatures of the three places, it able us to conclude that “Estao da Luz” is hotter than the other two. The two other places have lower temperatures in the morning, but also rise during the hottest hours of the day, in the afternoon. However, between 1:30pm and 2:45pm, the temperatures are a few degrees higher than in “Estao da Luz”, but this does not have a great impact because it continues to have the greatest temperature average.Because of its distance, “Estao Jlio Prestes” should be hotter than “Estao da Luz”, but its average temperature is actually 0,2C lower. Which I believe is because in “Estao Jlio Prestes” there is a wind corridor and there are a few vegetation in front of it, contrasting with “Estao da Luz”, where there is only concrete.It was stated an edification level in the three places; “Estao da Luz” has an average of 13,3m, “Estao Jlio Prestes” has a 23m average and “Parque da Luz” is only 9,4m. The edification level intensifies the temperature because of the concrete, as it was said in the introduction.
So again, “Estao Jlio Prestes” should be the hottest one.Graph 5 -Source: Fieldwork Author: Teresa P. NogueiraConclusionThrough the processes of analysis of the data collected I can say that my hypothesis, “Further the place is from “Parque da Luz” warmer it is, therefore the park helps on diminishing urban heat island in So Paulo’s CBD” was partially right.
The temperature on the two stations are higher than on the park; but the odd thing is that “Estao Jlio Prestes” should have its temperature average higher than the other because it has a lot of the factors that intensifies the temperature, it is farther away from the park, its level of edification is higher, but “Estao da Luz” continues to have the higher temperature average.I believe that without the park, the temperature on these places would be much higher than it is today. That is why the park helps, but not much, on diminishing urban heat island in So Paulo, because its area is not enough for the surrounded urban area.If I could do this fieldwork again, my hypothesis to the Research Question would be: “The park area does not help to diminish urban heat island in the three places studied because the other factors are stronger than the vegetation on the park, therefore the park does not change anything in the temperature of its surroundings.”I think that to improve the data collection and the information, we should have more precisely tools to better measurements and results.
We could also have more factors analyzed like the colour, materials of the constructions to see if they have a big influence on UHI.For example for measuring wind intensity we could have equipment, not just a table and our guessing. And also, for a climatology work to be valid the data needs to be collected for at least 30 years.If we were in more people we would not need to stop the measuring for one-hour lunch and we would be able to measure the data from other places as well, to have more examples of distances and temperatures.
References:1 CBD is the Central Business District where contains the major shops and offices. Large cities may have more than one (Waugh, David – 1995).2 Albedo is the capacity of a surface material to reflect incident solar radiation. (http://www.epa.gov/hiri/resources/faq.html).3 The ratio, of the radiation emitted by a surface to the radiation emitted by a blackbody at the same temperature (http://www.epa.gov/hiri/resources/faq.html).