Effect of urban land use change on ambient air temperature
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Contents
Scope
Change in urban near-surface ambient air temperature (2 m) caused by a given type of land use/surface cover type.
⇤# : this is not clear and does not answer to the question on the page --Matthew 08:22, 4 February 2013 (EET)
Definition
--# : Urban land use and changes in ambient air temperature is an impact assessments having a wide scope relating to both environmental and health issues conducted so as to prevent against land surface heating that could result in near surface air temperature changes by replacing each unit surface heating with a potential cooling trees --Matthew 09:55, 4 February 2013 (EET)
Data
NYSERDA 2006: Urban heat island mitigation study conducted in New York City[1]
Absolute differences in near-surface air temperature (ºF) between different surface cover types within New York City.
| Average daily temperature | Maximum daily temperature | |
| Grass to trees | -1.1 | -3 |
| Impervious to trees | -3.5 | -8.7 |
| Impervious to grass | -2.5 | -5.8 |
| Impervious to light | -2 | -4.6 |
These differences were derived from MM5 regional climate model run, in which New York City's land surface is assumed to have it's present (year 2006) configuration of trees, grass, and impervious surfaces. The difference in near-surface air temperature between impervious surfaces and trees represents the potential cooling from replacing a unit of impervious surface with a unit of trees. Considering these differences independent of the amount of available area for redevelopment allows for direct comparison of the cooling potential of different mitigation strategies, all else being equal. The actual city-wide cooling then depends on the number of units that can be redeveloped and the percent of the city's total surface area these units represent.
Underlying assumptions in different mitigation strategies in the NYSERDA study:
Grass to trees (open space planting)
It was assumed that any area that is currently grassy could be planted with trees unless it had been delineated as a cemetery, ball field, playground, athletic track or tennis courts. Areas within parks designated as beaches, gardens, recreational centres, playgrounds, or athletic areas were also filtered out. All planted trees were assumed to be deciduous and mature from the date of planting.
Street to trees (curbside planting)
The available area for street trees was an estimate based on inventories subtracted from a hypothetical maximum carrying capacity for each city street. The estimate was adjusted for highways, bridges, tunnels, and subtraction of intersection widths and tree setbacks from corners, and other infrastructure that could limit street tree density. Spacing of one tree every 23 meters was applied to account for the impact of limited planting sites due to existing infrastructure. All planted trees were assumed to be deciduous and mature from the date of planting, and have a canopy diameter of 11.5 meters.
Impervious surface to light surface
A flat-roof data layer was created by determining which land-use categories in NYC are most likely to have flat roof architecture. It was assumed that all flat roofs were available to receive 75% coverage of light roof surface. For light roof surface, a clean bright surface with and albedo of 0.5 was assumed as opposed to an estimated average albedo of 0.15 for impervious surfaces in NYC. An albedo of 0.2 was assumed for light street level surfaces, such as sidewalks and roadways.
Dependencies
Unit
°C/unit area
Formula
Result
| Average daily temperature | Maximum daily temperature | |
| Grass to trees | -0.6 | -1.7 |
| Impervious to trees | -1.9 | -4.8 |
| Impervious to grass | -1.4 | -3.2 |
| Impervious to light | -1.1 | -2.6 |
See also
References
Related files
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