Impacts of Saharan dust as CCN on the evolution of an idealized tropical cyclone

[1] The impact of dust in the Saharan Air Layer (SAL) acting as cloud condensation nuclei (CCN) on the evolution of a tropical cyclone (TC) was examined by conducting simulations initialized with an idealized pre-TC mesoscale convective vortex (MCV) using the Regional Atmospheric Modeling System (RAMS). Increasing the background CCN concentration from 100 to 1000 and 2000 cm 3 in a layer between 1 and 5 km led to increases in averaged cloud droplet number concentration, and decreases in cloud droplet mean mass diameter through the entire simulation except during the initial spin-up. Dust in the SAL as CCN influenced the TC development by inducing changes in the hydrometeor properties, modifying the storm diabatic heating distribution and thermodynamic structure, and ultimately influencing the TC intensity through complex dynamical responses. The simulated storm intensities differed by up to 22 hPa depending on CCN concentration. The impact of CCN on storm intensity was sensitive to the background giant CCN (GCCN) vertical profile and presumably other environmental factors. The physical processes responsible for the impact of dust as nucleating aerosols on TC development need to be examined in the future under a wide range of environmental conditions. Citation: Zhang, H., G. M. McFarquhar, S. M. Saleeby, and W. R. Cotton (2007), Impacts of Saharan dust as CCN on the evolution of an idealized tropical cyclone, Geophys. Res. Lett., 34, L14812,

[1]  Z. Levin,et al.  On the interactions of mineral dust, sea-salt particles, and clouds : A measurement and modeling study from the Mediterranean Israeli Dust Experiment campaign , 2005 .

[2]  Bin Wang,et al.  A Potential Vorticity Tendency Diagnostic Approach for Tropical Cyclone Motion , 2000 .

[3]  Melville E. Nicholls,et al.  A Vortical Hot Tower Route to Tropical Cyclogenesis. , 2006 .

[4]  Sonia M. Kreidenweis,et al.  African dust aerosols as atmospheric ice nuclei , 2003 .

[5]  W. Cotton,et al.  RAMS 2001: Current status and future directions , 2003 .

[6]  William R. Cotton,et al.  A Large-Droplet Mode and Prognostic Number Concentration of Cloud Droplets in the Colorado State University Regional Atmospheric Modeling System (RAMS). Part I: Module Descriptions and Supercell Test Simulations , 2004 .

[7]  C. L. Jordan.  MEAN SOUNDINGS FOR THE WEST INDIES AREA , 1958 .

[8]  William R. Cotton,et al.  Impacts of Nucleating Aerosol on Florida Storms. Part I: Mesoscale Simulations , 2006 .

[9]  Z. Levin,et al.  The Effects of Desert Particles Coated with Sulfate on Rain Formation in the Eastern Mediterranean , 1996 .

[10]  Yoram J. Kaufman,et al.  Dust transport and deposition observed from the Terra‐Moderate Resolution Imaging Spectroradiometer (MODIS) spacecraft over the Atlantic Ocean , 2005 .

[11]  Thomas A. Guinn,et al.  Hurricane Spiral Bands , 1993 .

[12]  S. H. Melfi,et al.  Validation of the Saharan dust plume conceptual model using lidar, meteosat, and ECMWF Data , 1999 .