343 Assessment of Environments Conducive to Convective Generation and Sustenance within the Maritime Continent

Monday, 23 January 2017
4E (Washington State Convention Center )
Benjamin A. Toms, Colorado State University, Fort Collins, CO; and S. C. van den Heever

Deep convection is a critical component of the hydrological cycle and radiative energy budget within the Maritime Continent.  Individual moist, convective plumes commonly aggregate into large convective complexes that then feed back into the convectively coupled meso- and synoptic scale circulations.  This upward energy cascade may have significant thermodynamic impacts downstream of the Maritime Continent, even propagating across the globe in the form of the Madden-Julian Oscillation (MJO).  Analysis of the evolution of individual convective cells within the Maritime Continent is, therefore, crucial to the understanding of the development and propagation of the MJO.  However, analysis of such convective evolution is complex due to its dependence on a wide range of variables, including: land-sea interactions, land- and ocean-atmosphere interactions, sea-surface temperatures, aerosol concentrations (e.g. anthropogenic and wildfire-borne), and kinematic and thermodynamic profiles.

We aim to quantify the importance of specific environmental variables on singular deep convective cells within the Maritime Continent using an in-depth evaluation of a basin-scale simulation.  The Regional Atmospheric Modeling System (RAMS), an open-source cloud-resolving model with an integrated bin-emulating double-moment microphysics scheme, was used to simulate an MJO event centered over the northern portions of the Maritime Continent. ERA-Interim reanalyses were used to constrain only the lateral domain boundaries of the multi-week large-scale simulation, within which RAMS was allowed to directly resolve the evolution of the mesoscale features.  The grid spacing (2 km x 2 km horizontal; 100 m base, stretched vertical grid to 1000 m) was sufficient to explicitly resolve cloud-scale processes, although emphasis was placed on the generation of deep convection rather than on cloud microphysical characteristics.

Canonical environments were identified within which deep convection occurred throughout the simulation.  The contributions of land- and ocean-atmosphere fluxes, land-sea interactions, sea-surface temperatures, aerosol concentrations, and kinematic and thermodynamic profiles were deduced by tracking convective clusters and sampling the ambient environment throughout their evolution.  Ranges of the specified parameters favorable for the generation and sustenance of deep convection were binned, and probability distribution functions (PDFs) generated.  Contoured frequency by altitude diagrams (CFADs) were used to quantify the influences of environmental variables on the vertical structure of the deep convection.  This presentation will highlight the relative importance of each environmental variable in the generation and aggregation of deep convective cells.

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