Current Icing Potential (CIP) severity index

A severity index has been added to the Current Icing Potential (CIP) product. The CIP severity index is compared with the icing severity contained in pilots’ reports (PIREPs), as well as the performance of the operational icing advisories (i.e., AIRMETs and SIGMETs). The comparisons are presented via standard verification statistics and a variety of plots. The results indicate that the CIP severity index performs at least as well as AIRMETs for identifying moderate-or-greater PIREPs and at least as well as SIGMETs for identifying moderate-to-severe or greater PIREPs. However, the CIP severity does not appear to discriminate well between the eight categories of icing intensity reported by pilots. The lack of discrimination may be due to the nature of PIREPs rather than the CIP severity. Research aircraft measurements of liquid water content and drop size distribution can be used as surrogates for icing intensity measurements. Though the research aircraft data are more limited spatially, they are more likely to accurately and consistently represent the true atmospheric conditions. The CIP severity index is compared to these measurements.