A study is underway at New Mexico State University to investigate the effects of different landscapes (irrigated turfgrass, non-irrigated xeric, hardscape) on ambient air and surface temperatures. In a second phase, data will be used to model energy requirements to cool or heat adjacent buildings. Two standard wood frame walls covered with stucco measuring 3.5 m by 3.5 m (11.48 ft. by 11.48 ft.) and surrounded by either Kentucky bluegrass or hardscape (coarse, crushed rock) were set up at New Mexico State University’s turfgrass research center and on campus. Four thermocouples were mounted on each wall, two at 0.50 m (1.64 ft.) and two at 1.00 m (3.28 ft.) height from the ground. To measure air temperature, sensors were also installed at the same height in front on each wall at a distance of 10 m (32.81 ft.). Additional sensors measuring relative humidity, wind speed, and net radiation were placed on top of each of the walls. Sensor readings were collected and recorded every 30 minutes using dataloggers.
Data are used to calculate heat flux (q) on the outside of the walls, which is a contributing factor to temperature changes inside buildings. Heat flux or thermal flux, also referred to as heat flux density or heat flow rate intensity, is a flow of energy per unit of area per unit of time. Moreover, relative differences between the heat fluxes on turfgrass and on hardscape also can be calculated.
A small sample of results are presented here during one week in June 2017 with high solar radiation (7.22 kWh/m2/day, week of June 5, 2017). Generally, the temperatures on the outside of the walls surrounded by two different landscapes do not differ considerably (Figure 1) even though building wall temperatures are cooler when surrounded by natural turfgrass than xeric landscapes. However, differences are more pronounced for heat flux. In June for example, heat flux along the wall surrounded by xeric landscaping exceeds those at the wall surrounded by natural turfgrass by up to 80 percent (Figure 2). In November, during a time period with low solar radiation (5.69 kWh/m2/day, week of November 7) these differences are still present but are much smaller.
Tis research will continue through 2019 with more results forthcoming. You can also keep an eye on the Twitter accounts of Dr. Bernd Leinauer (@NuMex_Turf) and Dr. Matteo Serena (@matteoserena1) for updates and images.
Figure 1. Temperature changes during one week in June on wall surrounded by turfgrass and by hardscape.
Figure 2. Heat flux changes during one week in June on wall surrounded by turfgrass and by hardscape.
TPI Turf News September/October 2018
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