Aerosol modulation of tropical cyclone landfall dynamics over the Indian region

Aerosols are increasingly recognized as a significant modulator of tropical cyclone (TC) dynamics. Yet, their stage-dependent roles during the pre-landfall (PLF), landfall (LF), and post-landfall (PoLF) stages remain poorly understood, particularly over India. Three high-impact landfalling TCs over the east coast of India, i.e., Hudhud (2014), Titli (2018), and Fani (2019), using the WRF-Chem model with Doppler Weather Radar (DWR’s) radar reflectivity data assimilation are considered in this study. Results suggest exceptional performance of the model in terms of TC intensity and rainfall estimates up to a lead time of 72 hours. It is evident that dust, sea salt (SS), and sulphate (SA) play major roles in regulating TC characteristics during different stages. Robust instability and well-organized features are noted for each TC during PLF and LF, except for Hudhud, which suddenly collapsed during the LF and PoLF. This unique feature in Hudhud is attributed to weak radial inflow and outflow, along with weak moisture convergence (MFC) during PoLF, in contrast to other TCs. Results also suggest a systematic, stage-dependent shift in the dominant aerosol regime: SS co-varies with TC intensity and rainfall during PLF and may participate in feedback between strong winds, sea-salt production, and cloud microphysics, with strong updrafts amplifying marine aerosol content, latent heat release, and rainfall intensity. During LF, intense rainfall suppresses aerosol-microphysics feedbacks. In PoLF, there is generally a massive surge in dust and SA within the TC environment due to overwhelming land interactions. In this stage, unique influences are noted for each TC. For Hudhud, dust is a major factor, whereas for Titli and Fani, it is SS due to variations in landfall tracks. Lead-lag correlation analysis further demonstrates that SS precede rainfall and intensity enhancement during PLF, whereas enhanced dust and SA are associated with subsequent weakening, though this co-occurs with land interaction and reduced moisture supply during LF and PoLF.