Oral Presentation AMOS Annual Meeting and International Conference on Tropical Meteorology and Oceanography

CONVECTIVE TRIGGERING IN CLOUD LINES (#178)

Abhnil Prasad 1 , Steven Sherwood 1
  1. University of New South Wales, Sydney, NSW, Australia

The diurnal cycle of convection and the associated rainfall is influenced by convective triggering. Triggering is crucial in understanding deep convection, which is poorly represented in global models and is the source of many model biases, especially over the Maritime Continent in the Tropics. We use several cases of convective cloud lines observed in January 2016 from the Himawari-8/9 satellite over the Gulf of Carpentaria in Northern Australia to test the convective triggering process. We simulated these cases using the Weather Research and Forecasting (WRF) Model (version 3.7.1) starting at a resolution of 9 km with convective parametrization and then downscaled the outermost domain up to a resolution of 333 m using three additional nested grids with explicitly resolved convection. Several microphysical and radiation schemes were tested to match the satellite-derived outgoing longwave radiation used as a proxy for deep convection. We then use the finest simulations closest to observations as “truth” to determine critical thresholds used by the convective trigger functions in parametrized convection. Several experiments using the vertical velocity and moisture-advection based trigger are tested in an attempt to improve convection over observed cloud lines. Results from the improved trigger functions and its sensitivity to moisture in the boundary layer influencing convection will also be discussed.