01-05 December 2025
INCOIS, Hyderabad, India.
| Abstract Submission No. | ABS-03-0313 |
| Title of Abstract | Moist Static Energy Budgets and Propagation Characteristics of Indian Summer Monsoon Intraseasonal Oscillations |
| Authors | Nirupam Karmakar*, Poulami Chattopadhyay |
| Organisation | IIT Bhubaneswar |
| Address | SEOCS 120 IIT Bhubaneswar Khordha, Odisha, India Pincode: 752050 E-mail: nirupam@iitbbs.ac.in |
| Country | India |
| Presentation | Oral |
| Abstract | The Indian Summer Monsoon (ISM) is crucial for agriculture and water resources across South Asia, with one of its dominant modes of variability occurring on intraseasonal timescales (20⿿70 days). These intraseasonal oscillations (ISO) manifest as alternating active and break phases of rainfall and are marked by the coherent northward propagation of convection from the equatorial Indian Ocean (EIO) to the Himalayan foothills. Previous studies have examined the characteristics of ISO and suggested links between the state of central India (CI) during break phases and the subsequent strength of active phases. However, the thermodynamic and dynamic processes governing ISO initiation and propagation remain less well understood. In particular, the relative contributions of moist static energy (MSE) budget components to the ISO lifecycle have not been systematically quantified. In this study, we first analyze the spatiotemporal evolution of ISO events, with emphasis on their inception over the EIO and subsequent northward propagation. Using Multichannel Singular Spectrum Analysis (MSSA), ISO signals are isolated from 25 years of IMERG rainfall and atmospheric data. Eastern EIO convective events are categorized based on simultaneous rainfall anomalies over CI. Results show that of 77 EIO convective initiations, 26 exhibit stronger and slower northward propagation when CI experiences a strong dry anomaly at the time of onset. To investigate the energetic drivers of these differences, we apply an MSE budget framework using ERA5 reanalysis. The analysis evaluates the roles of horizontal and vertical advection, surface turbulent fluxes (latent and sensible heat), and radiative heating during active and break phases of ISO. Our findings suggest a strong connection between ISO propagation speed and MSE budget components, particularly under suppressed CI conditions. These results provide new insights into the energetics of monsoon intraseasonal variability and have implications for improving extended-range prediction systems. |
| Are you part of IIOE-2 endorsed project | no |
| Keywords | Indian monsoon variability; intraseasonal oscillation; moist static energy budget |
| For Awards | no |