New York City’s recent summer heat wave has made the Urban Heat Island effect—the tendency of cities to be warmer than surrounding areas due to their lack of vegetation and high concentrations of cement and asphalt—an even greater concern. Urban vegetation serves as a tool to mitigate the Urban Heat Island effect due to evapotranspiration. In New York City, Central Park’s 843 acres of greenery and the growing number of green roofs throughout the five boroughs are cooling the urban landscape. We sought to quantify their effects.

In our first study, we evaluated the cooling effect of a New York City green roof during the winter and summer months, analyzing both surface temperature and 1-foot air temperature, which is rarely studied due to its complexity. We found a consistent daytime surface cooling effect in both summer and winter. Air temperature results were inconclusive, illustrating the difficulty of measuring air temperature in imperfectly controlled urban environments. Our second project consisted of a detailed analysis of the effect of Central Park on ground and air temperature readings taken from river to river at 79th Street. Air and surface temperatures were measured by a Thermoworks infrared thermometer. Our Central Park findings showed an average ground cooling effect of 4.12ºF and an average air cooling effect of 3.21ºF inside the park. The data indicate that the cooling effect may extend out of the park on the East Side; however, the near West Side demonstrated higher temperatures than the far West Side on both days, which merits further investigation. We have confirmed that urban vegetation demonstrates significant cooling effects. However, our conclusions display the challenges urban scientists face when monitoring temperature.

Sponsors:National Aeronautics and Space Administration (NASA) NASA Goddard Space Flight Center (GSFC)NASA Goddard Institute for Space Studies (GISS)NASA New York City Research Initiative (NYCRI) Contributors:Stuart Gaffin, Ph.D., Cynthia Rosenweig, Ph.D.Angelica Pasqualini, Center for Climate Systems Research Alan Roditi, High School TeacherEmma Hartung, Undergraduate Student Akil Grubb, High School Student

Going Green, Keeping Cool:The Cooling Power of Urban Vegetation

Alan Roditi, Emma Hartung, Akil Grubb

•Thermoworks IR Sensor•GPS•Black Umbrellas•Tape Measure•Chalk•Standard Excel Data Sheets•Clipboards

Central Park: Temperatures were recorded using two Thermoworks IR sensors starting at 79th Street and West End, passing through Central Park and ending on 79th Street and First Avenue. Temperatures were recorded three times on every block and approximately every 50 feet within Central Park. Readings were taken between 10am and noon. A black umbrella was used to block out the air probe from being in direct sunlight. The recordings and weather and sidewalk conditions were recorded on our standard data sheets.

Abstract

Materials

Background

Procedure

Conclusions

Future Work

References

Fieldston Green Roof•Our study displays that there is a daytime cooling effect for surface temperature during both summer and winter.•Our data suggests that nighttime green roof air temperatures are warmer than black roof air temperatures.• Slight variations in distance can have significant effect on air

temperature.Central Park•Our study is showing that Central Park temperatures are cooler than urban city.• Time of measurements affect temperature trends.

Fieldston Green Roof Analysis

•With global temperatures rising due to climate change, scientists are investigating increased vegetation as an urban cooling strategy.•Cooling strategies are especially necessary in urban areas due to the Urban Heat Island effect (UHI), which is the tendency for cities to absorb and retain more heat than surrounding areas.•An estimated 1/3 of New York City’s post-1900 warming can be attributed to UHI (Gaffin et al., 2008), which creates a 2.5ºC average annual urban-rural temperature difference (Gaffin et al., 2009.)When vegetated surfaces are replaced with man-made surfaces, the latter create an UHI effect due to the loss of heat-mitigating evapotranspiration (Akbari et al., 1992).•Green roofs demonstrate lower heat gain (Gaffin et al., 2010) and lower surface temperatures (Gaffin et al., 2009) than black roofs, reducing the UHI and need for cooling in the buildings below.

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Average Surface Temperature Over 24 Hours

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Black Air Temp

Green Surf. Temp

Black Surf. Temp

•From 8am to 5pm the Green Roof surface temperature was significantly cooler the Black Roof surface temperature during Summer and winter.• Average daytime cooling effect: Winter: 0.53 ºC, Summer: 7.53 ºC

Summer

Summer

Winter

Winter

•Data suggests that from 6pm to 7am the Green Roof air temperature was slightly warmer than the Black Roof air temperature. This however is not a conclusive result.• Average nighttime cooling effect: Summer: 0.71 ºC, Winter: 1.25 ºC

•Air temperature results were unexpected.•Possible causes may come from inconsistencies such as variation in roof location as well as roof structure as shown by disparity between North and South air temperature.

Akbari, H., Davis, S. Dorsano, S., Huang, J., Winnett, S., 1992. Cooling our Communities: A Guide-book on Tree Planting and LightColored Surfacing. U.S. Environmental Protection Agency and Lawrence Berkeley Laboratory.

Gaffin, S. R., Khanbilvardi, R., Rosenzweig, C., 2012. Development of a Green Roof Environ-mental Monitoring and Meteorological Network in New York City. Sensors 9 2647-61.

Gaffin, S. R., Rosenzweig, C., Eichenbaum-Pikser, J., Khanbilvardi R., Susca, T., 2010. A Temperature and Seasonal Energy Analysis of Green, White, and Black Roofs. Columbia University, Center for Climate Systems Research. New York. 19 pages.

Gaffin, S.R., Rosenzweig, C., Khanbilvardi, R., Parshall, L., Mahani, S., Glickman, H., Goldberg, R., Blake R., Slossberg, R.B., Hillel, D., 2008. Variations in New York City’s Urban Heat Island Strength Over Time and Space. Theoretical and Applied Climatology 94 1-11.

Fieldston Green Roof: Temperatures were recorded by CR-800 and CR-1000 data loggers at 1 hour intervals. Data loggers where located on the North and South green roofs as well as the black roof. The recordings were exported to Microsoft excel data sheets for analysis

Fieldston Green Roof•Further research about air temperatures and attempt to control or take it accounts variable such as roof location and structure.• Compare air temperature above other surfaces e.g: turf versus grass.Central Park• Repeat experiment for more data; investigate Near West Side warming.• Attempt a traverse across 42st so that Central Park’s cooling effect is

removed.

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Near West Average

Central Park Average

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Far East Average

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West to East Central Park Traverse (7/24/13)

10:30 am

10:48 am

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10:07 am

approaching the East River; this may indicate that Central Park’s cooling effect radiates outward

• The West Side showed no gradual decrease due to high Near West Side temperatures.

• We will continue to investigate potential reasons behind this, including escaping subway heat and sidewalk surface types.

Air Temperature Difference, Summer 2011 (°C)

North Green South Green Average Green

Overall -1.55 0.22 -0.67

High Temps -1.11 0.34 -0.38

Central Park Study

West to East Central Park Traverse (7/3/13)85 11:49 am

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75West Side Average Central Park Average East Side Average

Ground Air

• Air temperatures in the park were an average 3.21ºF cooler

• Ground temperatures in the park were an average 4.12ºF cooler

• Temperatures within Central Park were relatively constant

• Near East Side/Far East Side averages show a gradual temperature increase