Comparison of our fast solar wind model to observed properties of the real fast solar wind close to the solar surface. Upper panel: proton densities within 10 R_⊙ of the solar surface in our fast wind model compared to observational electron density profiles inside and above coronal holes from Munro & Jackson (1977), Doyle et al. (1999), and Cranmer & van Ballegooijen (2005). Lower panel: wind temperature within 4.5 R_⊙ compared to measurements of wind temperatures in coronal holes (red circles) compiled by Cranmer (2004). As in Fig. 3, the red and black lines in the lower panel show the fast and slow wind simulations respectively.