*3.5. Patch Descriptors of the Park*

In this paper, several indicators were applied to characterize the impact factors on PCI (Table 3). By using the ArcGIS 10.2 tools, we calculated fractal dimension (Frac\_Dim), perimeter-area ratio (Patario) and shape index (Shape\_ldx) in patch level. From the previous studies, those three indicators were used as the main patch metrics, and had been widely employed to analyze landscape patterns, both in class level and patch level [33–35]. These initial base studies were successful in demonstrating the characteristics of landscape patterns both in regional and local scale [53]. Here we investigated the relation of these indicators to park cooling effect in sample areas of Zhengzhou city. Low fractal dimension is described as simple, non-waving, straight boundaries, high fractal dimension means waving edges of park and surroundings.


#### **Table 3.** Park metrics used in this study.

Notes: \* Source: FRAGSTATS: https://www.umass.edu/landeco/research/fragstats/documents/fragstats\_documents.html.

In addition to the three indicators, we also used three indices to classify the satellite image of the study area (Table 4), which have been successfully proven by other researchers. The three indicators are Normalized Difference Water Index (NDWI) [55], Fractional Vegetation Cover (FVC) [56] and Normalized Difference Impervious Surface Index (NDISI) [57]. These indices can represent the surface coverage condition inside of the park.


**Table 4.** Spectral indexes of Landsat image used in this study.

Notes: \* Where NDVIi is NDVI value of a pixel i; NDVImin is minimum value; NDVImax is maximum value. R, G, NIR, SWIR, TIR, (Table 1).
