## 4 Results and Discussion
### Gaussian Fitting of SUHI Maps
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**City** & **Season** & **10:00** & **14:00** & **22:00** & **02:00** \\ \hline Bangkok & Summer & x (0.70) & x (0.70) & x (0.75) & x (0.75) \\  & Winter & x (0.74) & x (0.73) & x (0.66) & x (0.64) \\ \hline Chiang May & Summer & x (0.73) & x (0.73) & x (0.90) & x (0.87) \\  & Winter & x (0.71) & x (0.69) & x (0.86) & x (0.82) \\ \hline Nakhon & Summer & - & - & x (0.72) & x (0.82) \\ Ratchasima & Winter & - & - & x (0.73) & x (0.79) \\ \hline Ubon & Summer & x (0.60) & x (0.63) & x (0.87) & x (0.83) \\ Ratchathani & Winter & x (0.73) & x (0.69) & - & - \\ \hline Khon Kaen & Summer & - & - & x (0.81) & x (0.77) \\  & Winter & x (0.73) & x (0.68) & x (0.82) & x (0.82) \\ \hline Udon Thani & Summer & x (0.71) & x (0.70) & x (0.81) & x (0.84) \\  & Winter & x (0.88) & x (0.88) & x (0.67) & x (0.70) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Correlation coefficient r between SUHI from MODIS (MODerate Resolution Imaging Spectroradiometer) and Gaussian surface for the six cities. The mean r value over the years 2003–2016 is reported in brackets. x = reliable Gaussian fit; - = no Gaussian fit. and cassava croplands. Rice cropland experiences very different surface temperatures during the year that affect the LST of the rural area, since their thermal conditions depend strongly on site-specific activities and on the irrigation practice. Rice irrigation usually takes place during rainy season (May-October), with harvest finishing in December. Therefore, paddy rice areas are hot bare soils in summer during daytime, while in winter, the harvesting season, some areas start to appear warm. In the nighttime, such rural warming disappears, and a moderate urban heating prevails. Concerning the summer daytime KK SUHI pattern (Figure 6), the southwest rural surroundings are mostly paddy rice areas, providing the same rural warm effect of NR, even if it is not recognizable in winter daytime. The daytime and nighttime behavior of the UR SUHI pattern is very different, since the urban area is divided in two parts by the river and its rural surroundings (see Ubon Ratchathani in Figure 2), as revealed by the cold strip in the middle of the daytime pattern of Figure 6. During daytime, the urban heating of the upper and wider part of the city is predominant. During nighttime, the urban pixels and the rural/river strip pixels between the two city parts have similar LST values, resulting in an overall wider city area with a more uniform LST pattern. This effect causes a nighttime SUHI footprint (with intensities less than 2 \({}^{\circ}\)C) that is wider and has a different location. In winter nighttime, the pattern does not allow a reliable Gaussian fitting. A similar nighttime enlargement of the SUHI footprint happens also to KK during winter. For a more complete overview of the processed maps, an additional 48 maps for the six cities considering a daytime and nighttime summer map during the years 2004, 2008, 2012, and 2016 are reported in Supplementary Materials. Figure 5: _Cont._  
Figure 5: SUHI (\({}^{\circ}\)C) and Gaussian fitting during 2014 for Bangkok (BG), Chiang Mai (CM), and Nakhon Ratchasima (NR) for summer and winter, considering the diurnal variation at 10:00, 14:00, 22:00, and 02:00. Figure 6: _Cont._