## 4 Discussion
### Heatwave Detection, Its Magnitude, and Characteristics
#### 4.2.2 Satellite-Based Land Surface Temperature Assessment  
Comparative analysis using satellite data alongside air temperature measurements further confirms the notable difference, with satellite observations specifically highlighting the enhanced intensity of nighttime heatwaves in comparison to daytime events across various metrics. This observation aligns with the findings of [106], which suggest that nighttime and compound heatwaves experience a more pronounced increase in both frequency and intensity compared to their daytime counterparts. Notably, peri-urban and rural regions display elevated heatwave metrics consistently. Further, the examination of annual heatwave patterns at specific sites reveals that daytime heatwave events are more prevalent and severe in peri-urban areas, such as Pathum Thani and Eastern Bangkok, with occurrences ranging from 2 to 9 and durations from 10 to 39 days within a year. In contrast, urban areas, specifically downtown Bangkok, face a higher risk of nighttime heatwaves, with an annual frequency of 3 to 12 events and durations ranging from 13 to 62 days. Our findings reveal a significant rise in nighttime heatwave number (HWN) and heatwave amplitude (HWA) trends in urban settings, particularly in the Bang Na and Suan Luang districts of Eastern Bangkok. These trends suggest a potential amplification of the urban heat island effect, likely influenced by rapid urban development. The construction of new residential projects, warehouses, and buildings, alongside proximity to industrial estates and Suvarnabhumi International Airport, may contribute to this phenomenon. A study by [138] supports this correlation, indicating that a 10% increase in urban built-up density can lead to a 0.08% to 0.95% rise in HWN. Our study highlights that LST demonstrates lower amplification for HWM while being higher for HWA compared to air temperature measurements, particularly in urban settings during daytime heatwaves. Our findings, in line with [37], reveal that comparing air temperatures and satellite-derived LST data between normal and heatwave years shows a significant increase in daytime air temperature during heatwaves. For example, the Don Muang region in Bangkok exhibited the highest annual temperature extremes, with observed HWM fluctuating between 33 \({}^{\circ}\)C and 42 \({}^{\circ}\)C, and HWA extending from 35 \({}^{\circ}\)C to 45 \({}^{\circ}\)C. Significantly, the highest mean HWM of \(T_{\text{air}}\) was observed in UBKK (Khlong Toei, Bangkok) at 45.5 \({}^{\circ}\)C in 1997, and the highest HWA was recorded in RBCL (Bua Chum Meteorological Station, Lop Buri) at 43.2 \({}^{\circ}\)C in 2016. Our findings contrast with the reported effectiveness of LST data in identifying daytime heatwaves as underscored by [38; 139], demonstrating the strong correlations between \(T_{\text{air}}\) and MODIS-LST data. However, ref. [140] demonstrates how the suggested GIS-based methodology may be used to analyze heatwave susceptibility and effect scenarios in different urban patterns. This result underscores the need for targeted climate adaptation and resilience strategies, particularly in urban and peri-urban areas, to address the distinct impacts of daytime and nighttime heatwaves. Therefore, these findings are crucial for understanding heatwave dynamics, providing essential insights for anticipating and mitigating heatwave impacts, which are increasing in frequency and severity due to climate change. Spatial Homogeneity in Correlation Analysis between Detected Heatwave Indices from Ground-Observed Air Temperature and Satellite-Based Land Surface Temperature  
Spatial-temporal consistency evaluates the uniformity of identified heatwave patterns across varied regions and temporal spans. This evaluation is frequently quantified through the use of correlation coefficients or measures of similarity. By conducting comparisons of identified heatwave events with ground truth data and evaluating the detection algorithms' reliability, the study can affirm the integrity of the findings.