Urban parks have been known to form park cooling islands (PCI), which can effectively alleviate the effect of urban heat islands (UHI) in cities. This paper presents results obtained for four different size parks in the city of Wroclaw, which is located in a temperate continental climate. The number of publications for urban areas located in this type of climate and cities is low compared to sites in hot and humid areas. Land surface temperature (LST) maps were developed from Landsat 8 Thermal Infrared Sensor (TIRS) data acquired during three hottest weather periods between 2017 and 2019. Metrics and spatial statistics characterising the four parks selected for the analysis based on their size were calculated. These included: perimeter, area, landscape shape index (LSI) and PLC (forest area) park metrics, and Park Cooling Area (PCA), Park Cooling Efficiency (PCE), Park Cooling Gradient (PCG), Park Cooling Island (PCI) and Extended Park Cooling Island (PCIe) spatial indexes. The averaged PCIe values ranged from 2.0 to 3.6 °C, PCI from 1.9 to 3.6 °C, PCG from 0.7 to 2.2 °C, PCE from 5.3 to 11.5, and PCA from 78.8 to 691.8 ha depending on the park. The cooling distance varied from 110 m to 925 m depending on park size, forest area and land use type in the park’s vicinity. The study provides new insight into urban park cooling effects in a medium sized city located in a temperate continental climate, and the role of parks in regulation of urban temperature to mitigate the UHI effect.

<p>The average air temperature in the world has increased recently. Over the past 20 years, the global average has increased by 0.6 C and continues to increase [1]. In south-western Poland, in Wrocław, for the same period, the recorded increase in the average air temperature is approx. 0.5 °C [2]. The reason for this phenomenon is human activity. The process of urbanisation has created another phenomenon called the Urban Heat Island (UHI), which can be studied analysing for example the Land Surface Temperature (LST). The combined effect of the UHI and climate change can influence groundwater temperature by penetrating underground. The phenomenon of elevated groundwater temperatures is called the Subsurface Urban Heat Island (SUHI) [3,4]. While the Urban Heat Island effects is generally negative and widely investigated, the higher groundwater temperature may have positive aspect, such as e.g. use in heat pumps. The SUHI phenomenon is less understood than the UHI one.<br>This presentation focuses on the spatial distribution of temperature in shallow aquifers in the city of Wroclaw (SW Poland) developed with various interpolation techniques and based on measurements made in a network of piezometers in the 2004-2005 period. In total 67 locations have been measured and the temperatures recorded varied between 1.1 °C and 24.5 °C with the average of 13.2 °C. The data has been processed with the IDW, spline and kriging interpolation methods. The groundwater temperature distribution was analysed spatially, taking into account the then land use and location of technical infrastructure. In addition, an attempt has been made to compare the distribution of groundwater temperature with the Land Surface Temperature. The latter was determined based on Landsat 5 satellite imagery.<br>The interpolated groundwater temperature maps have made it possible to analyse and present graphically the spatial distribution of temperature and link it to the LST UHI for the analysed period.</p><p>Bibliography:</p><p>[1] Global Climate Change https://climate.nasa.gov/ (accessed on 11 January 2022)</p><p>[2] Polish climate 2020. Institute of Meteorology and Water Management, National Research Institute. Available online: https://www.imgw.pl/sites/default/files/2021-04/imgw-pib-klimat-polski-2020-opracowanie-final-pojedyncze-min.pdf. (accessed on 11 January 2022)</p><p>[3] Luo Z., Asproudi C., Subsurface urban heat island and its effects on horizontal ground-source heat pump potential under climate change, Applied Thermal Engineering, Volume 90, 2015, doi: 10.1016/j.applthermaleng.2015.07.025.</p><p>[4] Zhu, K., Bayer, P., Grathwohl, P., and Blum, P. (2015), Groundwater temperature evolution in the subsurface urban heat island of Cologne, Germany, Hydrol. Process., 29, 965– 978, doi: 10.1002/hyp.10209</p>

In Wrocław over the past 20 years, the recorded increase in the average ambient air temperature is approx. 0.5 °C. In addition, urbanisation has created a phenomenon called the Urban Heat Island (UHI). The combined effect of the UHI and climate change can influence groundwater temperature by penetrating underground. The phenomenon of elevated groundwater temperatures in urban areas is called the Subsurface Urban Heat Island (SSUHI). This study focuses on the spatial distribution of temperature in shallow aquifers in the city of Wroclaw. The spatial distribution was analysed based on groundwater temperature maps developed with various interpolation techniques. The results of measurements in a network of 65 piezometers conducted in the 2004-2005 hydrological year have been used in this study. The temperatures recorded show seasonal variation with the lowest recorded in February (1.3 °C) and the highest in August (24.5 °C) with the annual average of 13.2 °C. The data has been processed with the Inverse Distance Weighted (IDW), Radial Basis Function (RBF) and Kriging interpolation methods. Furthermore, the cokriging method based on multivariate linear regression models has been used to assess if variable such as distance from the city centre improve the interpolation performance expressed as the lowest RMS error value. It has been established that the Kriging univariate regression model based interpolation method produced the best results (RMS error equal to 1.33 °C) and that the distance from the city centre has improved the accuracy of interpolation.