Sensitivity of Temperature Perturbation to Precipitation: A Parametric Study

Global warming and unusual rainfall are significant consequences of anthropogenic activities and have been a hot research topic since the last century. Urban heat island (UHI) causes serious environmental hazards that occur mainly due to urbanisation and anthropogenic activity, which may change the weather pattern. UHI effect is referred to the temperature of the air or the land surface of an urban area being more than the surrounding non-urban region. This temperature difference, referred to as urban heat island intensity, is generated mainly due to an increase in anthropogenic heat. This intensity of UHI may cause an uplift of local heat flux and spread to the atmospheric planetary boundary layer (PBL), which leads to instability in the thermodynamic and dynamic structure of the urban environment. Together with ground surface heating, atmosphere instability indirectly influences the intensity of rainfall in the urbanised area. Most of the earlier UHI-related study has shown the increase in temperature around the major city ranging from $2 ^{\circ}\mathrm{C}$ to $10 ^{\circ}\mathrm{C}$. In the present work, an attempt is made to quantify the effect of temperature perturbation on precipitation rate. A numerical simulation is carried out by perturbing temperature at the surface level by 2 K, 4K, 6 K, 8 K and 10 K and exponentially decreasing height up to the PBL. The enhanced temperature increases in near-surface mixing and convection resulted in a significant change in the local weather leading to a shift in rainfall pattern. Due to temperature perturbation from 2 K to 10 K, the precipitation rate increases continuously; however precipitation rate is more sensitive to the degree of perturbation. These enhancement characteristics are observed locally at the downwind side of perturbation.