Application of the isentropic analysis of convective motions for gravity wave filtering in the TWP-ICE IOP 2006 Australian Monsoon

Gravity waves are often spatially and temporally collocated with a vigorous convection that generated them. Attempts to diagnose the convective mass transport through spatial and temporal filtering are often contaminated by oscillatory motions that do not contribute to transport. Here, we explore the possibility of using an isentropic analysis to study turbulent convection. By sorting the convective circulation based on the adiabatic invariants of the flow, such as entropy or equivalent potential temperature, which evolve timescales that are much shorter than convectively driven gravity waves, one can filter out most of the gravity waves from the convective overturning.

In the present study, we test this filtering method using existing multiple cloud resolving models' (CRMs) simulations of the TWP-ICE IOP case study of the 2006 Australian Monsoon. We analyze the transport and properties of updrafts and downdrafts separately in convective and stratiform regions. We then compare the results with and without isentropic filtering to assess the mass transport associated with deep convective events and discuss the apparent, but incorrect, contribution to convective mass flux that is filtered out through this method. We find that this method of filtering indeed works very well in removing gravity wave noise, and can be used to evaluate the thermodynamic properties of the convective updraft and downdrafts.