Direct Radiative Effects in Haboobs

Abstract

AbstractConvective dust storms, or haboobs, form when strong surface winds loft loose soils in convective storm outflow boundaries. Haboobs are a public safety hazard and can cause a near instantaneous loss of visibility, inimical air quality, and contribute significantly to regional dust and radiation budgets. Nevertheless, reliable predictions of convective dust events are inhibited by a lack of understanding regarding the complex and non‐linear interactions between density currents, or convective cold pools, and dust radiative effects. In this study, the Weather Research and Forecasting model coupled with Chemistry (WRF‐Chem) is utilized to simulate the effect dust radiation interactions have on a long‐lived haboob case study that spans three distinct radiative regimes: day (high shortwave), evening (low shortwave), and night [longwave (LW) only]. A sophisticated algorithm is used to track and identify the numerous convective old pool boundaries in the simulations and assemble statistics that represent the impact of dust radiative effects. To first order, dust scattering of shortwave radiation in the day leads to a colder, dustier, and faster moving convective cold pool. In the transition period of early evening, the shortwave effects diminish while LW dust absorption leads to warmer, slower density currents that loft less dust as they propagate. At night, the haboob is again warmer due to dust absorption, but gustier in the more stable nocturnal surface layer, leading to enhanced dust emissions.