The Cloud Scene Simulation Model (CSSM) was developed to generate high-resolution synthetic cloud backgrounds for a variety of military simulation systems. Cloud types which are currently simulated include stratiform, cirriform, and cumulus. This paper presents a summary of recent improvements to the CSSM's cirriform cloud model along with results from a comparison of that model to observed ice water content data. Model improvements focused on tuning internal model parameters used to control the spatial character of the simulated cloud fields. Previous model parameters were estimated from values reported in literature and on visual inspection. Recent efforts estimated parameter values using a more quantitative approach; by comparing CSSM output fields to in situ measurements from the SUCCESS experiment. A description of the analysis process used to estimate "tuned" model parameters is included in this paper. Results show a much improved cirrus model. Preliminary statistical hypothesis testing shows that paths through CSSM cirrus cloud fields compare well to in situ cirrus measurements. Results from that analysis are presented