Appendix D - An Interim Icing Envelope

Mazzawy, R. S.; Strapp, J. W.

doi:10.4271/2007-01-3311

Cited by 17 publications

(14 citation statements)

References 3 publications

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“…Motivated by the 1990s commuter jet engine power loss problem, Lawson et al (1998) reanalyzed more limited in situ measurements collected within anvils over Montana during the Cooperative-Convective-Precipitation-Experiment (CCOPE) (Knight, 1982) and near the Tiwi Islands during the Central Equatorial Pacific Experiment (CEPEX) (Heymsfield and McFarquhar, 1996;McFarquhar and Heymsfield, 1996). Since no direct measurements of IWC were obtained during these campaigns, it was calculated from the most suitable data available.…”

Section: Microphysical Conditionsmentioning

confidence: 99%

High ice water content at low radar reflectivity near deep convection – Part 1: Consistency of in situ and remote-sensing observations with stratiform rain column simulations

Fridlind¹,

Ackerman²,

Grandin³

et al. 2015

Atmos. Chem. Phys.

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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).

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Section: Microphysical Conditionsmentioning

confidence: 99%

High ice water content at low radar reflectivity near deep convection – Part 1: Consistency of in situ and remote-sensing observations with stratiform rain column simulations

Fridlind¹,

Ackerman²,

Grandin³

et al. 2015

Atmos. Chem. Phys.

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“…An early Royal Aircraft Establishment report by McNaughton (1959), which has been used for years to provide some guidelines to aviation on ice water content, describes measurements made in convective clouds near Entebbe, Singapore and Darwin with total water contents (probably mostly ice) exceeding 5 g m −3 . Mazzawy and Strapp (2007) summarize these and other measurements in order to come up with "Appendix D -An Interim Icing Envelope" which defines a mixed phase/glaciated icing environment to be used by the aviation industry in certifying engines for operations in these conditions.…”

Section: Introductionmentioning

confidence: 99%

On the observation of unusual high concentration of small chain-like aggregate ice crystals and large ice water contents near the top of a deep convective cloud during the CIRCLE-2 experiment

et al. 2012

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Abstract. During the CIRCLE-2 experiment carried out over Western Europe in May 2007, combined in situ and remote sensing observations allowed to describe microphysical and optical properties near-top of an overshooting convective cloud (11 080 m/−58 • C). The airborne measurements were performed with the DLR Falcon aircraft specially equipped with a unique set of instruments for the extensive in situ cloud measurements of microphysical and optical properties (Polar Nephelometer, FSSP-300, Cloud Particle Imager and PMS 2-D-C) and nadir looking remote sensing observations (DLR WALES Lidar). Quasi-simultaneous space observations from MSG/SEVIRI, CALIPSO/CALIOP-WFC-IIR and CloudSat/CPR combined with airborne RASTA radar reflectivity from the French Falcon aircraft flying above the DLR Falcon depict very well convective cells which overshoot by up to 600 m the tropopause level. Unusual high values of the concentration of small ice particles, extinction, ice water content (up to 70 cm −3 , 30 km −1 and 0.5 g m −3 , respectively) are experienced. The mean effective diameter and the maximum particle size are 43 µm and about 300 µm, respectively. This very dense cloud causes a strong attenuation of the WALES and CALIOP lidar returns. The SE-VIRI retrieved parameters confirm the occurrence of small ice crystals at the top of the convective cell. Smooth and featureless phase functions with asymmetry factors of 0.776 indicate fairly uniform optical properties. Due to small ice crystals the power-law relationship between ice water content (IWC) and radar reflectivity appears to be very different from those usually found in cirrus and anvil clouds. For a given equivalent reflectivity factor, IWCs are significantly larger for the overshooting cell than for the cirrus. Assuming the same prevalent microphysical properties over the depth of the overshooting cell, RASTA reflectivity profiles scaled into ice water content show that retrieved IWC up to 1 g m −3 may be observed near the cloud top. Extrapolating the relationship for stronger convective clouds with similar ice particles, IWC up to 5 g m −3 could be experienced with reflectivity factors no larger than about 20 dBZ. This means that for similar situations, indication of rather weak radar echo does not necessarily warn the occurrence of high ice water content carried by small ice crystals. All along the cloud penetration the shape of the ice crystals is dominated by chainlike aggregates of frozen droplets. Our results confirm previous observations that the chains of ice crystals are found in a continental deep convective systems which are known generally to generate intense electric fields causing efficient ice particle aggregation processes. Vigorous updrafts could lift supercooled droplets which are frozen extremely rapidly by homogeneous nucleation near the −37 • C level, producing therefore high concentrations of very small ice particles at upper altitudes. They are sufficient to deplete the water vapour and suppress further nucleation as confirmed by humidity measure...

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“…The sampling strategy was consistent with 2015 in terms of the sampling altitudes (-50°C±5°C, -40°C±5°C, -30°C±5°C and -10°C±5°C), but with an added interest to fly also at -25°C±5°C levels when mission rules allowed. Based on adiabatic estimates of maximum condensed water that are the basis of the Appendix D TWC envelope [1],and numerical simulation results by Protor, et al [22], there was reason to believe that TWC values might maximize in the -20° to -30°C temperature interval. This flight level was not identified as a priority by the EHWG, and was not a focus for the HAIC-HIWC and first HIWC RADAR campaigns.…”

Section: Sampling Strategiesmentioning

confidence: 99%

“…In 2003, the FAA chartered an Aviation Rulemaking Advisory Committee (ARAC) called the Engine Harmonization Working Group (EHWG) to evaluate the effects of supercooled large drop (SLD) and mixed phase/glaciated conditions on commercial transport power plants [1]. The EHWG found that most weather-related engine powerloss events on commercial aircraft had occurred in or near deep convective storms.…”

Section: Introductionmentioning

confidence: 99%

Summary of the High Ice Water Content (HIWC) RADAR Flight Campaigns

Ratvasky

Harrah

Strapp

et al. 2019

SAE Technical Paper Series

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NASA and the FAA conducted two flight campaigns to quantify onboard weather radar measurements with in-situ measurements of high concentrations of ice crystals found in deep convective storms. The ultimate goal of this research was to improve the understanding of high ice water content (HIWC) and develop onboard weather radar processing techniques to detect regions of HIWC ahead of an aircraft to enable tactical avoidance of the potentially hazardous conditions. Both HIWC RADAR campaigns utilized the NASA DC-8 Airborne Science Laboratory equipped with a Honeywell RDR-4000 weather radar and in-situ microphysical instruments to characterize the ice crystal clouds. The purpose of this paper is to summarize how these campaigns were conducted and highlight key results. The first campaign was conducted in August 2015 with a base of operations in Ft. Lauderdale, Florida. Ten research flights were made into deep convective systems that included Mesoscale Convective Systems (MCS) near the Gulf of Mexico and Atlantic Ocean, and Tropical Storms Danny and Erika near the Caribbean Sea. The radar and in-situ measurements from these ten flights were analyzed and correlations defined. Key results included 1) derived relationships between radar reflectivity factor (RRF), Ice Water Content (IWC), and ice particle size distributions, 2) characterization of HIWC conditions at the-50°C and other flight levels, and 3) verification of pilot observations, such as low radar reflectivity factor and pitot and total air temperature (TAT) anomalies. This data set also enabled new pilot radar HIWC detection algorithms to be developed and tested. A second campaign was conducted in August 2018 to test proposed HIWC radar detection algorithms within a new set of storm systems. Seven research flights were conducted from bases of operations in Ft. Lauderdale, Florida; Palmdale, California; and Kona, Hawaii. Flights were made into convective systems over the Gulf of Mexico and into an eastern-Pacific tropical system that developed into Hurricane Lane. Using a new, NASA-developed radar processing technique called "Swerling", regions of HIWC were identified, and estimates of IWC were produced, at distances up to 60 Nm ahead of the NASA DC-8. Subsequently, the DC-8 flew through these regions to acquire the insitu measurements to verify the radar-based IWC estimates.

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Appendix D - An Interim Icing Envelope

Cited by 17 publications

References 3 publications

High ice water content at low radar reflectivity near deep convection – Part 1: Consistency of in situ and remote-sensing observations with stratiform rain column simulations

High ice water content at low radar reflectivity near deep convection – Part 1: Consistency of in situ and remote-sensing observations with stratiform rain column simulations

On the observation of unusual high concentration of small chain-like aggregate ice crystals and large ice water contents near the top of a deep convective cloud during the CIRCLE-2 experiment

Summary of the High Ice Water Content (HIWC) RADAR Flight Campaigns

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