## 4 Discussion
An SUHI intensity study across 150 major cities in India, each located in distinct climatic regions, analyzed by employing MODIS data spanning from 2003 to 2018, found that daytime SUHI was tightly linked to vegetation, evapotranspiration, and thermal inertia, while nighttime SUHI was linked with built-up intensity, white sky albedo, and thermal inertia [90]. The nighttime UHI effect and its intensity observed in the present study were more conspicuous, positive, and consistent compared with daytime satellite observations, which agrees with the previous studies and suggests that nighttime LST is more sensitive to changes in urban microclimate and hence a better indicator of SUHI intensity. Cities located in the Indo-Gangetic plains showed seasonal variation in daytime LST with a rising trend in LST during pre-monsoon to monsoon months and a decreasing trend in post-monsoon to winter months (Tables 1 and 5). The present study is consistent with the reports of [98], which stated that a decline in daytime LST over the GRB and central India from 2001 to 2019 was partially attributable to rising aerosol trends except for higher sporadic pockets of warming observed in pre-monsoon and monsoon months. The rising trend in AOD over GRB during winter and post-monsoon season and its declining trend in pre-monsoon and monsoon season can be negatively correlated with the daytime LST trend [99]. The decline in daytime LST compared with the significant rise in nighttime LST over the same region suggests that nighttime temperature is more sensitive as a climate change indicator than daytime temperature [100]. The decreased precipitation observed in recent decades, especially during the monsoon months, is speculated to be a possible reason for rising LST in the monsoon. The elevation in net radiation absorption, coupled with increasingly arid climatic conditions, amplifies the warming effect due to reduced cloud cover and diminished moisture availability for evaporative cooling, resulting in higher LST [98]. Previous works of literature have found a decreasing trend in summer rainfall over GRB and central India [101; 102]. The present study found that the highest nighttime surface urban island effect was observed in Jaipur, Delhi, Lucknow, Lahore, Faisalabad, Kanpur, and Dhanbad during the pre-monsoon (March-April-May) months (Figures 9 and 10, Table 6), although the highest average nighttime temperatures recorded in these cities were in April-May-June, while Ahmedabad, Hyderabad, Surat, Kolkata, Yangon, Karachi, Pune, Bengaluru, Chennai, Dhaka, Mumbai, Coimbatore, and Colombo exhibited the highest effect of urban heat island during winter. The study points out that all cities uniformly exhibited higher nighttime SUHI during winter months than during AMJ in all cities except Lahore. Delhi exhibited slightly less nighttime SUHI in winters than during AMJ. The nighttime SUHI effect was observed to be lowest in all cities during the peak monsoon (June-July-August) months (Figure 10c). It can be clearly demarcated from Figure 10a,b that average nighttime temperature patterns varied along different months over different cities. Delhi, Kolkata, Lahore, Lucknow, Faisalabad, Jaipur, Kanpur, and Dhanbad were observed to have peak nighttime temperatures during MJJ months, which were maintained throughout the monsoon season. The nighttime LST of these regions was observed to decrease only during winter months. Contrary to this, the nighttime SUHI effect peaked with a significant dip in SUHI during monsoon season for cities such as Mumbai, Ahmedabad, Surat, Bangalore, Coimbatbatore, and Hyderabad (Figure 10d). These cities showed relatively higher SUHI during winter months. The daytime SUHI variability showed strong contrast compared with the nighttime SUHI (Figures 10 and 11). Karachi, Bengaluru, Hyderabad, Pune, and Jaipur exhibited negative daytime SUHI in both pre-monsoon to onset of monsoon months and during winter months.