What type of study is this?

October 3, 2025

The Structure of a Developing Arabian Sea Monsoon Onset Vortex: Role of Moist Convection

Key Points

The study finds that moist convection primarily influences the structure and intensification of the monsoon onset vortex.
A composite analysis of 23 cases demonstrates distinct lower and mid-tropospheric maxima in potential vorticity associated with the MOV.
Using reanalysis data, the research shows that the MOV's structural characteristics arise from diabatic heating and vertical advection.
Comparative discussion highlights both parallels and discrepancies between the MOV and Bay of Bengal monsoon depressions.

Abstract

Abstract The Monsoon Onset Vortex (MOV) forms in the Arabian Sea around the beginning of the Indian Summer monsoon. Many MOVs intensify into tropical cyclones and can potentially impact the onset and advance of the Monsoon. The prevailing theory for the genesis of the MOV invokes the adiabatic hydrodynamic instability of the lower-tropospheric Somali Jet. However, the role of precipitating moist convection in MOV formation remains unexplored. This study examines the structure of a canonical MOV, defined as a composite of 23 past cases, using reanalysis data. The MOV structure indicates a lower tropospheric maxima (from ~ 700-850 hPa) and a mid-tropospheric maxima (~550 hPa) in the potential vorticity. A potential vorticity budget shows that this observed structure of the MOV likely results from adjustment to diabatic heating and vertical advection to a leading order. Both the low- and mid-level vortices in the developing MOV are primarily attributed to moist convection. Similarities and differences between the composite structures of the MOV and Bay of Bengal monsoon depressions are discussed. Additional work is needed to clarify the role of the traditional hydrodynamic instability in MOV formation.

Ask AI

Helpful

Bookmark