Modeling the atmospheric life cycle and radiative impact of mineral dust in the Hadley Centre climate model

A parameterization of mineral dust within the Hadley Centre atmospheric general circulation model (AGCM) is described, modeled dust distributions are compared with observations, and estimates of the radiative forcing due to the inclusion of dust in the model are obtained. The parameterization uses six particle size divisions in the range 0.3-30 mum radius, and all calculations are performed on each division independently, using the GCM's prognostic variables. The dust production scheme works within the GCM and includes dependencies on particle size distribution, soil moisture, vegetation, and friction velocity. Dust transport is carried out by the GCM's tracer advection scheme and includes vertical motion due to convection, gravitational settling, and turbulent mixing in the boundary layer. Wet and dry deposition processes are included within the GCM's precipitation schemes. Representative dust radiative parameters are incorporated into the GCM's two stream radiation code. Modeled monthly average near-surface dust concentrations are compared with observations: good agreement is seen in most locations, though the dust scheme tends to produce too little dust from China and too much from Australia in the southern spring. Global annual mean direct forcing due to the inclusion of dust in the GCM is +0.07 W m(-2) at the top of the atmosphere (TOA) and -0.82 W m(-2) at the surface. The geographical distributions of annual mean forcings are very inhomogeneous, with peak values exceeding the global means by a factor of approximately 2 orders of magnitude.