Characteristics of Diurnal Convection and Winds over the Maritime Continent during YMC with WRF Numerical Simulations and Data Assimilation at a Cloud Permitting Scale

This study utilizes the mesoscale community Weather Research and Forecasting (WRF) model and its data assimilation system to investigate the diurnal variations of the small- and meso-scale convective systems and their associated winds and precipitation over Maritime Continent (MC) during Madden-Julia Oscillation (MJO) events. The variability of the convective systems, precipitation, and winds on the diurnal and synoptic scales and their interactions with the MJO propagation are characterized. The relationship between diurnal variations of winds and precipitation over the MC region as well as the effects of local scale land-sea breezes and orography on convective system initiation, evolution, and propagation are investigated.

Specifically, cases during the MJO events within the Years of Maritime Continent (YMC) field campaign are studied. High resolution numerical simulations and analyses are conducted at a cloud permitting scale (~ 3km horizontal resolution) by assimilating available conventional and satellite observations. The local-scale effects contribute to the diurnal cycle of the convective systems, precipitation, and winds, as well as their variability over the MC region, are examined. The major controlling factors that enhance the interactions between local diurnal variability and large-scale dynamic and thermodynamic conditions, as well as MJO propagation, are investigated. The high-resolution analysis and simulations are also compared with the available global analyses to identify the uncertainties that limit the application of global analyses to understanding these processes. The NASA GPM satellite precipitation measurements and CYGNSS satellite ocean surface winds, and available local radar observations are also used for model validation and evaluation. The sensitivity of numerical simulations of the wind and precipitation fields to different microphysical, cumulus, and boundary layer schemes, as well as ocean-coupling, is also conducted to obtain insights into different processes that control the diurnal and multiscale variabilities over the MC region. Detailed results will be reported at the conference.