Idealized Simulations of the Brown Ocean Effect—Sensitivity to Land Use and Soil Moisture Availability

The Brown Ocean Effect (BOE) is the observation that post-landfalling tropical cyclones strengthen over moist surface, given a near-barotropic environment and sufficient latent heat flux release, emphasizing soil moisture. Under these conditions, the land surface imitates an ocean surface, which provides a moisture source. Previous research has indicated that an average latent heat flux of 70 W m^-2 over a two-week antecedent period has been able to support the BOE. However, there has not been a study that has identified the critical amount of soil moisture needed for the BOE. To this end, an idealized tropical cyclone simulation over a water surface using the Weather Research and Forecasting model (WRF) was conducted. After the idealized tropical cyclone developed over a water surface, a series of sensitivity experiments were conducted, with the water surface replaced by a barren and sparsely vegetated land surface with varying quantities of moisture availability. Statistical methods were employed to approximate a critical value of moisture availability needed for the BOE to occur. The sensitivity of this critical value to land use type will be explored.