# Assessing Spatiotemporal LST Variations in Urban Landscapes Using Diurnal UAV Thermography
## 4 Results
### Trend and Correlation Analysis of LULC and Ambient Temperature  
Ambient air temperature measurements were recorded concurrently with the UAV thermal data acquisition flights to establish the relationship between air and land surface temperatures across different temporal periods. The diurnal ambient temperature profile exhibited expected temporal variations, with minimum values recorded during morning and midnight periods (both 8 \({}^{\circ}\)C), reaching its peak during afternoon measurements (17 \({}^{\circ}\)C), and showing moderate temperatures during the evening period (12 \({}^{\circ}\)C). These ambient temperature measurements (single measurement for each time of day) serve as reference data for contextualizing the observed LST patterns and quantifying the surface-air temperature relationships across different LULC classes. The comparison of LULC class mean temperatures (Figure 6) with ambient weather temperatures revealed significant variations in thermal behavior across different surfaces throughout the diurnal cycle. Bare soil and grassland exhibited the highest fluctuations, with temperatures rising sharply in the afternoon, exceeding ambient conditions, and cooling drastically at midnight. Paved roads demonstrated notable heat retention, maintaining higher temperatures during the evening and midnight hours compared to other LULC classes. Water bodies exhibited the most stable temperature profile, reflecting their high thermal inertia and capacity to moderate temperature fluctuations. Built-up areas, such as buildings, followed a trend similar to ambient temperatures but displayed slightly lower values during the morning and midnight periods. It is possible to say that urban surfaces (paved roads and buildings) retain heat more effectively, contributing to higher evening temperatures, while natural surfaces (bare soil, grassland, and water bodies) respond more dynamically to diurnal temperature variations. The correlation analysis between LULC classes and ambient temperature revealed significant relationships that provide evidence of the influence of surface types on thermal variations (Figure 7). The results indicated that paved roads and buildings exhibited \begin{table}
\begin{tabular}{l l c c c c c} \hline \multirow{2}{*}{**LULC Class**} & **Temporal** & \multirow{2}{*}{\(n\)} & **Mean (\({}^{\circ}\)C)** & **SD** & **Median (\({}^{\circ}\)C)** & **Min** & **Max** \\ \hline Bare Soil & Morning & 96 & 7.00 & 3.45 & 7.45 & \(-\)0.90 & 11.62 \\  & Afternoon & 96 & 20.39 & 4.50 & 20.78 & 8.71 & 27.92 \\  & Evening & 96 & 8.60 & 3.78 & 8.57 & 3.01 & 17.31 \\  & Midnight & 96 & \(-\)0.97 & 1.35 & \(-\)1.18 & \(-\)2.93 & 3.07 \\ \hline Building & Morning & 98 & 3.15 & 3.07 & 2.38 & \(-\)0.90 & 11.39 \\  & Afternoon & 98 & 15.12 & 4.54 & 14.06 & 5.27 & 26.55 \\  & Evening & 98 & 6.88 & 3.29 & 5.79 & 2.16 & 15.24 \\  & Midnight & 98 & \(-\)0.52 & 1.71 & \(-\)1.05 & \(-\)2.60 & 4.78 \\ \hline Grassland & Morning & 81 & 6.19 & 3.49 & 7.37 & \(-\)0.90 & 11.39 \\  & Afternoon & 81 & 20.57 & 5.13 & 21.33 & 7.75 & 27.78 \\  & Evening & 81 & 3.34 & 0.41 & 3.33 & 2.36 & 4.36 \\  & Midnight & 81 & \(-\)2.45 & 0.31 & \(-\)2.50 & \(-\)3.16 & \(-\)1.55 \\ \hline Paved Road & Morning & 99 & 3.47 & 2.92 & 2.75 & \(-\)0.68 & 10.13 \\  & Afternoon & 99 & 19.45 & 4.22 & 19.69 & 7.75 & 28.06 \\  & Evening & 99 & 13.18 & 3.49 & 13.23 & 4.69 & 18.54 \\  & Midnight & 99 & 2.25 & 1.51 & 2.47 & \(-\)1.41 & 5.04 \\ \hline Water Body & Morning & 89 & 5.27 & 2.85 & 5.95 & \(-\)0.90 & 9.98 \\  & Afternoon & 89 & 7.10 & 1.25 & 7.20 & 5.00 & 10.22 \\  & Evening & 89 & 3.59 & 0.79 & 3.52 & 2.16 & 5.59 \\  & Midnight & 89 & 2.39 & 1.25 & 2.60 & \(-\)1.08 & 4.91 \\ \hline \end{tabular} Note: SD = Standard Deviation; \(n\) = number of observations.  
\end{table} 
Table 1: Descriptive statistics of land surface temperature by LULC class and temporal period.