@article {181,
	title = {Scale-dependent interactions between tree canopy cover and impervious surfaces reduce daytime urban heat during summer},
	journal = {Proceedings of the National Academy of Sciences},
	year = {2019},
	month = {2019/03/20},
	pages = {201817561},
	abstract = {Cities worldwide are experiencing record-breaking summer air temperatures, with serious consequences for people. Increased tree cover is suggested as a climate adaptation strategy, but the amount of tree canopy cover needed to counteract higher temperatures associated with impervious surface cover is not known. We used a bicycle-mounted measurement system to quantify the interaction of canopy cover and impervious surface cover on urban air temperature. Daytime air temperature was substantially reduced with greater canopy cover (>=40\%) at the scale of a typical city block (60{\textendash}90 m), especially on the hottest days. However, reducing impervious surfaces remained important for lowering nighttime temperatures. Results can guide strategies for increasing tree cover to mitigate daytime urban heat and improve residents{\textquoteright} well-being.As cities warm and the need for climate adaptation strategies increases, a more detailed understanding of the cooling effects of land cover across a continuum of spatial scales will be necessary to guide management decisions. We asked how tree canopy cover and impervious surface cover interact to influence daytime and nighttime summer air temperature, and how effects vary with the spatial scale at which land-cover data are analyzed (10-, 30-, 60-, and 90-m radii). A bicycle-mounted measurement system was used to sample air temperature every 5 m along 10 transects (\~{}7 km length, sampled 3{\textendash}12 times each) spanning a range of impervious and tree canopy cover (0{\textendash}100\%, each) in a midsized city in the Upper Midwest United States. Variability in daytime air temperature within the urban landscape averaged 3.5 {\textdegree}C (range, 1.1{\textendash}5.7 {\textdegree}C). Temperature decreased nonlinearly with increasing canopy cover, with the greatest cooling when canopy cover exceeded 40\%. The magnitude of daytime cooling also increased with spatial scale and was greatest at the size of a typical city block (60{\textendash}90 m). Daytime air temperature increased linearly with increasing impervious cover, but the magnitude of warming was less than the cooling associated with increased canopy cover. Variation in nighttime air temperature averaged 2.1 {\textdegree}C (range, 1.2{\textendash}3.0 {\textdegree}C), and temperature increased with impervious surface. Effects of canopy were limited at night; thus, reduction of impervious surfaces remains critical for reducing nighttime urban heat. Results suggest strategies for managing urban land-cover patterns to enhance resilience of cities to climate warming.},
	keywords = {air temperature, ecosystem services, landscape context, urban forest, urban heat island},
	doi = {10.1073/pnas.1817561116},
	url = {http://www.pnas.org/content/early/2019/03/19/1817561116.abstract},
	author = {Ziter, Carly D. and Pedersen, Eric J. and Kucharik, Christopher J. and Turner, Monica G.}
}
@article {162,
	title = {Urban heat island-induced increases in evapotranspirative demand},
	journal = {Geophysical Research Letters},
	year = {2017},
	month = {2017},
	abstract = {Although the importance of vegetation in mitigating the urban heat island (UHI) is known, the impacts of UHI-induced changes in micrometeorological conditions on vegetation are not well understood. Here we show that plant water requirements are significantly higher in urban areas compared to rural areas surrounding Madison, WI, driven by increased air temperature with minimal effects of decreased air moisture content. Local increases in impervious cover are strongly associated with increased evapotranspirative demand in a consistent manner across years, with most increases caused by elevated temperatures during the growing season rather than changes in changes in growing season length. Potential evapotranspiration is up to 10\% higher due to the UHI, potentially mitigating changes to the water and energy balances caused by urbanization. Our results indicate that local-scale land cover decisions (increases in impervious cover) can significantly impact evapotranspirative demand, with likely implications for water and carbon cycling in urban ecosystems.},
	keywords = {ecohydrology, plant water use, reference evapotranspiration, urban climatology, urban ecology, urban heat island, Urban systems, Water supply},
	isbn = {1944-8007},
	doi = {10.1002/2016GL072190},
	url = {http://dx.doi.org/10.1002/2016GL072190},
	author = {Zipper, Samuel C. and Schatz, Jason and Kucharik, Christopher J. and Loheide, Steven P.}
}
@article {128,
	title = {Urban heat island effects on growing seasons and heating and cooling degree days in Madison, Wisconsin USA},
	journal = {International Journal of Climatology},
	year = {2016},
	month = {2016},
	abstract = {Urban areas tend to be warmer than their rural surroundings, a phenomenon known as the urban heat island (UHI) effect. UHIs are nearly always described in terms of temperature. However, UHIs can also be described using derived climate indices, including growing season length, growing degree days (GDDs), and heating and cooling degree days, which may have more direct ecological and economic significance than temperature alone. To characterize UHI effects on these basic climate parameters, we used over 3 years of continuously collected temperature data from up to 150 locations in and around Madison, Wisconsin, USA, an urban area of population 402 000 surrounded by lakes and a rural landscape of agriculture, forests, wetlands, and grasslands. Compared to rural areas, Madison{\textquoteright}s UHI extended the freeze-free season by several weeks each year. However, it only shifted the onset of spring and fall (represented by 10-day moving average temperature crossing seasonal thresholds) by 1 day or less in spring and by a few days to a week in fall. The different effects on freeze dates versus running-mean temperatures were primarily because the UHI could affect temperatures during individual freeze events much more than it could influence regional seasonal temperature trends. Urban effects on the meteorological growing season were nearly always greater in fall than in spring. We hypothesize that this is due to seasonal differences in sub-surface temperatures, with urban and rural areas presumably having more uniform sub-surface temperatures in spring after being frozen throughout the winter, contributing to weaker UHI effects in spring than in fall. In terms of degree days, densely built urban areas averaged 14\% (209) more GDDs, 25\% (117) more cooling degree days, and 6\% (284) fewer heating degree days than rural areas, indicating that the UHI could have significant impacts on energy consumption in Madison.},
	keywords = {cooling degree days, energy, freeze dates, growing degree days, growing season, heating degree days, urban climate, urban heat island},
	isbn = {1097-0088},
	url = {http://dx.doi.org/10.1002/joc.4675},
	author = {Schatz, Jason and Kucharik, Christopher J.}
}
@article {137,
	title = {Urban heat island impacts on plant phenology: intra-urban variability and response to land cover},
	journal = {Environmental Research Letters},
	volume = {11},
	year = {2016},
	month = {2016},
	pages = {054023},
	abstract = {Despite documented intra-urban heterogeneity in the urban heat island (UHI) effect, little is knownabout spatial or temporal variability in plant response to the UHI. Using an automated temperaturesensor network in conjunction with Landsat-derived remotely sensed estimates of start/end of thegrowing season, we investigate the impacts of the UHI on plant phenology in the city of Madison WI(USA) for the 2012{\textendash}2014 growing seasons. Median urban growing season length (GSL) estimated fromtemperature sensors is \~{}5 d longer than surrounding rural areas, and UHI impacts on GSL arerelatively consistent from year-to-year. Parks within urban areas experience a subdued expression ofGSL lengthening resulting from interactions between the UHI and a park cool island effect. Acrossall growing seasons, impervious cover in the area surrounding each temperature sensor explains >50\%of observed variability in phenology. Comparisons between long-term estimates of annual meanphenological timing, derived from remote sensing, and temperature-based estimates of individualgrowing seasons show no relationship at the individual sensor level. The magnitude of disagreementbetween temperature-based and remotely sensed phenology is a function of impervious and grass coversurrounding the sensor, suggesting that realized GSL is controlled by both local land cover andmicrometeorological conditions.},
	keywords = {land surface phenology, remote sensing, sensor network, urban climate, urban ecology, urban heat island, vegetation phenology},
	isbn = {1748-9326},
	doi = {10.1088/1748-9326/11/5/054023},
	url = {http://stacks.iop.org/1748-9326/11/i=5/a=054023},
	author = {Samuel C Zipper and Jason Schatz and Aditya Singh and Christopher J Kucharik and Philip A Townsend and Steven P Loheide}
}
