Feedback between windblown dust and planetary boundary-layer characteristics: Sensitivity to boundary and surface layer parameterizations

Abstract

Inclusion of direct radiative forcing by mineral dust is important for accurate simulation of meteorological conditions, and planetary boundary-layer (PBL) parameterization plays a critical role in proper representation of such forcing. The direct radiative forcing of mineral dust and its feedback effects on boundary-layer dynamics are investigated using the Weather Research and Forecasting with Chemistry (WRF/Chem) model. Furthermore, this study examines the sensitivity of dust radiative effects associated with two different PBL schemes: the Yonsei University (YSU) scheme with both Noah and RUC (Rapid Update Cycle) land-surface models (LSMs), and the Mellor–Yamada–Janjic (MYJ) scheme. By reflecting and absorbing solar radiation, dust aerosols are predicted to cool the atmosphere from the surface to near the boundary-layer top, while warm the boundary-layer top and lower free atmosphere by absorbing both solar and infrared radiation. The simulated surface cooling and heating at the boundary-layer top stabilizes the lower atmosphere, causing a reduction of boundary-layer depth. The stabilized atmosphere restricts vertical exchange of momentum, resulting in an overall decrease of wind speeds in the lower boundary layer and an increase within the upper boundary layer and lower free atmosphere. Use of the YSU-RUC scheme resulted in larger dust feedback effects on atmospheric characteristics, while the MYJ scheme produced lower radiative feedback effects because of lower dust concentrations and reduced vertical mixing of dust. The differences in radiative forcing by dust in model runs are found to be mainly due to differences in PBL scheme, rather than the LSM used in the model.