Understanding heat retention and release through outgoing longwave radiation dynamics in the upper Gangetic alluvial plain

Outgoing Longwave Radiation (OLR) is a fundamental component of Earth's energy budget, representing the planet's primary mechanism for heat loss to space. The physical principles governing OLR emission, including blackbody radiation and the role of atmospheric absorption by greenhouse gases and clouds, are crucial for understanding this energy flux. This study investigates the month-wise trends in daytime and night-time outgoing longwave radiation (OLR) over the period 2013 to 2025, aiming to assess seasonal variability and the relationship between day and night radiative fluxes. Using OLR values (in W/m²), the analysis reveals distinct seasonal patterns daytime OLR peaks during the pre-monsoon months (April-May), indicating intense solar heating and clear-sky conditions, while significant drops during monsoon months (July-September) reflect increased cloud cover and atmospheric moisture. Night-time OLR follows a similar seasonal rhythm but is more influenced by nocturnal cloud cover and radiative cooling efficiency. 

A scatter plot between daytime and night-time OLR shows a strong positive correlation (r = 0.86), suggesting that surface heating during the day is closely linked to heat retention and emission at night. The high correlation also indicates the consistency of radiative processes over the diurnal cycle, with deviations hinting at atmospheric disturbances such as cloud formation or humidity changes. This relationship is critical for understanding regional energy balance and climate behaviour. The study concludes that OLR trends can serve as valuable indicators for monitoring climatic variability, supporting heatwave forecasting, enhancing agricultural resilience, and informing local adaptation strategies in climate-sensitive regions like north western India.