Thunderstorm Outflow Dust Lofting and Resulting Impacts on Convection
Numerically modeling this phenomenon is a difficult task due to the resolution required to accurately resolve the small-scale eddies responsible for lofting combined with an effective dust scheme. As such, a three-step approach using the Regional Atmospheric Modeling System (RAMS) with an on-line dust scheme will be utilized to accurately simulate: 1) how convective outflow boundaries loft mineral dust particles from the surface, 2) how the lofted dust becomes entrained into the parent convection, and 3) the resultant feedback of the ingested dust has on the parent convection and associated cold pool. Results presented are with respect to the first portion of the study.
Using RAMS with a very high-resolution domain (100m and 25m horizontal and vertical grid-spacing, respectively), an idealized downdraft generates the surface cold pool and outflow boundary responsible for dust lofting. Sensitivity experiments are conducted by systematically altering soil moisture, soil type, and low-level wind shear to develop a diagnostic parameterization of dust lofting potential as a function of surface soil conditions and cold pool strength. The parameterization will be useful for both operational forecasting to indicate dust storm potential and numerical modeling as an internal lofted dust concentration parameter. Future simulations will use idealized squall lines and supercells to better understand the pathway of dust ingestion and the impacts on the parent convection.