Assessing characteristics of the Rosemount Icing Detector under natural icing conditions

The performance of a Rosemount Icing Detector (RID) has been characterized using in-situ measurements of microphysical conditions in winter storms. The RID was mounted on the National Research Council (NRC) Convair-580 aircraft, with the data collected during flights from the First and Third Canadian Freezing Drizzle Experiments (CFDE I and EQ respectively). Aircraft icing environments encountered included liquid phase, mixed phase (liquid and ice hydrometeors), freezing rain and freezing drizzle environments. The liquid water content (LWC) detection threshold was estimated to be 0.007 ± 0.010 g for the RID operated at air speeds of 97 ± 10 m s. This value agrees with the predictions of Mazin et al. (2000) who estimated a LWC threshold of 0.002 to 0.006 g m. No significant RID response was found in glaciated clouds, implying that for the conditions observed, the instrument can be used to segregate glaciated and mixed phase clouds. There was no significant change in the RID response between liquid and mixed phase conditions, suggesting that ice crystals neither eroded ice accumulation nor accreted to the RID surface. During sustained icing encounters, a linear relationship between the RID signal and LWC was observed after the RID signal exceeded 400 mV above the clear air signal level. The LWC derived from the RID was found to agree with LWC measurements within ± 50% for 83% of the data. The relationship between the RID signal and LWC was unchanged for freezing precipitation environments with drop median volume diameters (MVD) > 100 jurn. Characteristics of the RID, highlighted by the analysis of the data, will be discussed.