## 3 Results
### Spatial Variability of Annual and Seasonal Mean LST
#### 3.1.1 Nighttime LST
The monthly average nighttime LST for DJF (December-January-February) representing winter months in the Indian subcontinent is illustrated in Figure 4. January showed relatively lower warming along the northern India and IG plains, while February showed higher warming in these areas during the winter months. Some of the largest agglomerations of northern India and its surrounds such as New Delhi, Jaipur, Kanpur, Faisalabad, and Lahore, showed much higher nighttime (24.47, 25.71, 25.46, 24.80, and 24.69 \({}^{\circ}\)C) LST within the city limits compared with their surroundings during AMJ and DJF months, as illustrated in Figures 3 and 4. Figure 1: The average (**a**) nighttime and (**b**) daytime MODIS-derived LST (\({}^{\circ}\)C) over India and surrounding countries for AMJ (April–May–June) months for the period 2000–2023. The extent of major urban cities (Table 1) derived from the MODIS urban extent and having the highest population are marked as polygons (core city region), along with a 10 km buffer ring. The geographical region (5–38\({}^{\circ}\) N and 66–100\({}^{\circ}\) E) under investigation is shown on the map. The monthly breakdown of the average nighttime temperature as given in Table 2 shows that that the highest nighttime temperatures for most of the cities (Karachi, Bengaluru, Chennai, Hyderabad, Ahmedabad, Surat, and Pune) were recorded during April, May, and June. Delhi, Dhaka, Kolkata, Lahore, Lucknow, Kanpur, and Dhanbad showed variations with the highest nighttime temperature recorded during the May-September months (Table 2). The highest and lowest average nighttime temperature of major cities during AMJ months was 27.82 \({}^{\circ}\)C recorded in Ahmedabad and 22.56 \({}^{\circ}\)C recorded in Bengaluru, respectively. Similarly, the lowest nighttime temperatures were recorded during DJF/winter months with the highest temperature recorded in Chennai at 23.17 \({}^{\circ}\)C and the lowest in Faisalabad at 9.13 \({}^{\circ}\)C. In general, the southern Indian cities such as Bengaluru, Chennai, Pune, Hyderabad, and Coimbatore showed the lowest temperature in the month of December, while the other northern Indian cities of the plains showed the lowest nighttime temperatures during January. Figure 2: The average nighttime MODIS-derived LST (\({}^{\circ}\)C) over India and surrounding countries for pre-monsoon (April-May) and onset of monsoon (June) months for the period 2000–2023. Figure 3: The monthly average nighttime MODIS-derived LST (\({}^{\circ}\)C) over India and surrounding countries for pre-monsoon (April–May) and onset of monsoon (June) months for the period 2000–2023 showing thermal contrast between major urban cities extent marked as polygons, and surrounding areas marked with 10 km buffer ring (for the period 2000–2023). Figure 4: The monthly average nighttime MODIS-derived LST (°C) over India and surrounding countries for DJF (December–January–February, winter season) months showing thermal contrast between major urban cities extent marked as polygons, and surrounding areas marked with 10 km buffer ring for the period 2000–2023. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c c c} \hline \hline
**Sl.** & **City** & **Ann.** & **AMJ** & **DJF** & **Jan** & **Feb** & **Mar** & **Apr** & **May** & **Jun** & **July** & **Aug** & **Sep** & **Oct** & **Nov** & **Dec** \\ \hline
1. & Delhi & 19.77 & 24.47 & 10.95 & 9.35 & 12.81 & 17.71 & 22.64 & 25.06 & 25.71 & 25.61 & 25.37 & 25.01 & 21.61 & 15.64 & 10.69 \\ \hline
2. & Mumbai & 22.49 & 25.13 & 20.62 & 19.82 & 21.16 & 23.54 & 25.86 & 26.15 & 23.38 & 19.68 & 19.93 & 21.55 & 24.01 & 22.90 & 20.86 \\ \hline
3. & Dhaka & 22.11 & 24.38 & 16.71 & 15.15 & 18.04 & 21.58 & 24.09 & 24.06 & 24.99 & 25.93 & 26.30 & 26.47 & 24.96 & 21.17 & 16.95 \\ \hline
4. & Karachi & 21.72 & 25.29 & 16.77 & 15.38 & 18.22 & 21.70 & 24.92 & 26.22 & 24.73 & 20.63 & 20.96 & 24.50 & 25.25 & 21.33 & 16.73 \\ \hline \hline \end{tabular}
\end{table}