Uploaded on 2016-03-03 by nesfog

The top 10 cities with the most intense summer urban heat islands (average daily urban-rural temperature differences) over the past 10 years are: 1. Las Vegas (7.3°F) 2. Albuquerque (5.9°F ) 3. Denver (4.9°F) 4. Portland (4.8°F) 5. Louisville (4.8°F) 6. Washington, D.C. (4.7°F) 7. Kansas City (4.6°F) 8. Columbus (4.4°F) 9. Minneapolis (4.3°F) 10. Seattle (4.1°F) On average across all 60 cities, urban summer temperatures were 2.4°F hotter than rural temperatures. **Let's focus on las Vegas.** ![Las vegas UHI][1] ![Las vegas UHI][2] ![Las vegas UHI 3][3] Among all this cities Las Vegas stands up, as we can see Las Vegas is the city with the higher difference between the urban and rural temperature, but with this information a question rises, **¿why the difference in the temperature is so high if there's a desert in the surroundings?** ![Las vegas terrain][4] This is because urban construction materials have different thermal (heat capacity and thermal conductivity) and radiative (reflectivity and emissivity) properties compared to surrounding rural areas, which results in more of the sun’s energy being absorbed and stored in urban compared to rural surfaces. In addition, the height of buildings and the way in which they are arranged affects the rate of escape at night of the sun’s energy absorbed during the day by building materials. The result is that urban areas cool at a much slower rate than rural areas at night, thus maintaining comparatively higher air temperatures. Another important reason is aerodynamic properties of the surface but what really increase UHI is the **heat produced by conditioned air systems**, since the city is located in a desert zone the city demands so much energy to make the buildings atmosphere cooler, I think this problem can be solved by improving design parameters for the cities but as we can see in the case of Las Vegas green areas makes no difference between the UHI effects. But increasing these green areas in to the city may improve air quality and humidity but I think it has no much to be with the UHI effect. **2. Which are the main UHI effects that you can identify in your area?** ![Santa Ana Urban][5] This is the Urban Area of Santa Ana City ![Cafetal][6] This is the rural area of Santa Ana City, As you can see Santa Ana has not grown in vertical way, it has grown horizontally that’s why thee UHI is not recognizable on the city. **3. Which are the measures you would propose?** These are measurements that should be registered related to the UHI effect • Temperature of the environment • Temperature of the buildings • Humidity • Rain • Carbon dioxide and other gases • Wind Velocity • Aerodynamic design of the city and topography • Reflectiveness and typology of the roofing materials • Reflectiveness and typology of the walls materials • Reflectiveness and typology of the streets • cooling energy consumption • Solar radiation - Is UHI effect concerning policy making in your area? Nowadays in my city there is no policies concerning this problem, actually the UHI effect is not known in Santa Ana, and that's because it is no so notable, sin the city is really small and the city has not grown in vertical. ![windity][7] This is the thermal situation of El Salvador, the temperature actually is really high but it is because of the location, this is a tropical country but the UHI effect it is not so strong and recognizable because of the small size of the cities. ![PNUD][8] In this map you can see the difference on the temperature compared by the high, as you can see the highest places are the coolest and the temperature of the cities in El Salvador are directly related with location. [1]: https://edxuploads.s3.amazonaws.com/14570264185048458.png [2]: https://edxuploads.s3.amazonaws.com/1457026449766231.png [3]: https://edxuploads.s3.amazonaws.com/14570264673663261.png [4]: https://edxuploads.s3.amazonaws.com/14570265082297682.jpg [5]: https://edxuploads.s3.amazonaws.com/145702670422092.png [6]: https://edxuploads.s3.amazonaws.com/14570267551870.jpg [7]: https://edxuploads.s3.amazonaws.com/1457026961458364.png [8]: https://edxuploads.s3.amazonaws.com/14570270543708609.png