Influence of aerosols on tropical cyclone dynamics during landfall over Indian region

Cyclone Fani, an extremely severe cyclone storm (ESCS) is one of the strongest cyclones in the Bay of Bengal (BoB) in recent decades and was responsible for the death of 90 people and the devastation of billions of dollars in Odisha. Many aspects of physical processes impact tropical cyclones. For the first time, the influence of aerosols on the structural and precipitation characteristics of the intense landfalling cyclone is investigated using high-resolution models over the Indian region. Two experiments using Weather Research and Forecast (WRF) are carried out i.e. without chemistry (CNT) and with chemistry (CHEM) in a nested domain fashion with 3 km resolution. The track and intensity forecast of CHEM is close to the observation compared to CNT during the landfall. In addition, the cyclone structure has been rapidly distorted in CNT due to early landfall (3 h prior) compared to observation, whereas CHEM has a realistic intensity, translational speed, structure and accurate landfall time. It is found that the CNT has a large overestimation of rainfall (> 300 mm) due to the presence of anomalously high cloud water and cloud ice compared to CHEM (250–300 mm), which has a closer match with observations. In general, it is also noted that the moisture source/sink Q_m has more contribution than cloud source/sink Q_c in rain for both simulations. However, the CNT has a high contribution in Q_m compared to CHEM due to overestimated moisture and intense vertical and horizontal advection. The intrusion of dust aerosol at the lower level leads to a higher boundary layer and radiative heating facilitating a more stable environment leading to suppression of moisture and weaker updrafts resulting in a realistic intensity and rainfall during landfall in CHEM. These findings have significant implications for aerosol re-distribution and how it affects precipitation and structural patterns of the cyclone.