Direct Effects of Air Humidity on Dust Aerosol Production: Evidences for the Surprising Role of Electrostatic Forces

Dust aerosols are produced by wind erosion, and it is widely accepted that dust aerosols can be produced only if the wind speed exceeds a certain threshold velocity, which is largely controlled by soil moisture content. The relative humidity (RH) in the air could affect soil moisture content, thereby impacting dust production indirectly. However, it is not clear if the RH can directly change dust aerosol production. Here we simulated dust production and show that the RH does play a direct role in affecting the production of dust aerosol in a quite complicated way, which can be explained by a hypothesis that the RH affects both the electrostatic forces and wet-bonding forces between soil particles in opposite directions. The current formula for dust aerosol production flux does not include the direct RH effect, and this study strongly suggests that it could lead to significant errors in estimating dust production.