Abstract
Abstract. Occurrences of jet engine power loss and damage have been associated with flight through fully glaciated deep convection at −10 to −50 °C. Power loss events commonly occur during flight through radar reflectivity (Ze) less than 20–30 dBZ and no more than moderate turbulence, often overlying moderate to heavy rain near the surface. During 2010–2012, Airbus carried out flight tests seeking to characterize the highest ice water content (IWC) in such low-Ze regions of large, cold-topped storm systems in the vicinity of Cayenne, Darwin, and Santiago. Within the highest IWC regions encountered, at typical sampling elevations (circa 11 km), the measured ice size distributions exhibit a notably narrow concentration of mass over area-equivalent diameters of 100–500 μm. Given substantial and poorly quantified measurement uncertainties, here we evaluate the consistency of the Airbus in situ measurements with ground-based profiling radar observations obtained under quasi-steady, heavy stratiform rain conditions in one of the Airbus-sampled locations. We find that profiler-observed radar reflectivities and mean Doppler velocities at Airbus sampling temperatures are generally consistent with those calculated from in situ size-distribution measurements. We also find that column simulations using the in situ size distributions as an upper boundary condition are generally consistent with observed profiles of Ze, mean Doppler velocity (MDV), and retrieved rain rate. The results of these consistency checks motivate an examination of the microphysical pathways that could be responsible for the observed size-distribution features in Ackerman et al. (2015).
Highlights
Between 1990 and 1998, commuter transport jets experienced at least 10 incidents of engine power loss near thunderstorms at elevations of 8.5–9.5 km a.m.s.l. and temperatures of −27 to −33 ◦C (Lawson et al, 1998; Mason et al, 2006)
= drizzle 2 = rain 3 = low-density snow 4 = high-density snow 5 = melting snow 6 = dry graupel 7 = wet graupel 8 = small hail 9 = large hail 10 = rain-hail mix Whereas that earlier study measured condensed water content (CWC) at 0 to −26 ◦C, the Airbus flights primarily sampled at colder temperatures, where many such events have occurred
These ice water content (IWC) measurements are roughly a factor of 2 greater than measurements from similar cloud regions documented in the scientific literature to date
Summary
Between 1990 and 1998, commuter transport jets experienced at least 10 incidents of engine power loss near thunderstorms at elevations of 8.5–9.5 km a.m.s.l. and temperatures of −27 to −33 ◦C (Lawson et al, 1998; Mason et al, 2006). Within any single flight through dense anvil at circa 11 km altitude in the Cayenne and Darwin flights, a stable selfsimilarity of mass size distributions over a wide range of IWC can be considered a surprising result because it is generally thought that the process of ice outflow from convective updrafts and subsequent sedimentation consistently leads to preferentially larger particles and more mass occurring closer to updraft sources (e.g., Lawson et al, 1998, 2010).
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