The inverse influence of MJO on the cyclogenesis in the north Indian Ocean

Abstract

We examine the influence of Madden Julian Oscillation (MJO) on tropical cyclones (TCs) in the north Indian Ocean (NIO). To analyse cyclogenesis, we have used the Genesis Potential Index (GPI) and Accumulated Cyclonic Energy (ACE) in the active years (AYs) and the non-active years (NAYs) of MJO during the period 1979–2019. The GPI anomaly shows enhanced cyclogenesis in NIO except for the northern part of the Bay of Bengal (BoB) in AYs, and an exact opposite anomaly of GPI is observed in NAYs in the Arabian Sea (AS) and BoB. Additionally, a strong negative correlation exists in the anomaly of relative humidity, potential intensity and absolute vorticity in AYs and NAYs. The reduction in MJO phase duration by 3–4 days in NIO is in accordance with the declining frequency of cyclones in AYs in BoB, but in contrast with the frequency of cyclones in AS. Similarly, an increasing trend of ACE is observed in AS with a clear indication of shifting the increased frequency of cyclones towards the western NIO (AS) in AYs. An inverse characteristic of cyclonic activity is observed in AS and BoB during AYs, particularly from 2014 onwards. Our analysis exposes apparent changes in MJO activity and its impact on cyclogenesis and cyclone activity in NIO, which may be attributed to the recent warming in NIO.