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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Aircraft microwave observations and simulations of deep convection from 18 to 183 GHz. II - Model results

In this June 29, 1986 case study, a radiative transfer model is used to simulate the aircraft multichannel microwave brightness temperatures presented in the Adler et al. (1990) paper and to study the convective storm structure. Ground-based radar data are used to derive hydrometeor profiles of the storm, based on which the microwave upwelling brightness temperatures are calculated. Various vertical hydrometeor phase profiles and the Marshall and Palmer (M-P, 1948) and Sekhon and Srivastava (S-S, 1970) ice particle size distributions are experimented in the model. The results are compared with the aircraft radiometric data. The comparison reveals that the M-P distribution well represents the ice particle size distribution, especially in the upper tropospheric portion of the cloud; the S-S distribution appears to better simulate the ice particle size at the lower portion of the cloud, which has a greater effect on the low-frequency microwave upwelling brightness temperatures; and that, in deep convective regions, significant supercooled liquid water (about 0.5 g/cu m) may be present up to the -30 C layer, while in less convective areas, frozen hydrometeors are predominant above -10 C level.

Yeh, Hwa-Young M.↗
NASA NTRS1992

Polarization Lidar Liquid Cloud Detection Algorithm for Winter Mountain Storms

We have collected an extensive polarization lidar dataset from elevated sites in the Tushar Mountains of Utah in support of winter storm cloud seeding research and experiments. Our truck-mounted ruby lidar collected zenith, dual-polarization lidar data through a roof window equipped with a wiper system to prevent snowfall accumulation. Lidar returns were collected at a rate of one shot every 1 to 5 min during declared storm periods over the 1985 and 1987 mid-Jan. to mid-Mar. Field seasons. The mid-barrier remote sensor field site was located at 2.57 km MSL. Of chief interest to weather modification efforts are the heights of supercooled liquid water (SLW) clouds, which must be known to assess their 'seedability' (i.e., temperature and height suitability for artificially increasing snowfall). We are currently re-examining out entire dataset to determine the climatological properties of SLW clouds in winter storms using an autonomous computer algorithm.

Sassen, Kenneth↗
NASA NTRS1994

Deep cumulonimbus cloud systems in the tropics with and without lightning

The thunderstorm frequency over the oceans during the Global Atmospheric Research Program Atlantic Tropical Experiment is quantified by examination of over 20,000 surface hourly observations from research ships. The overall thunderstorm frequency is one thunderstorm day per ship per month. There were many examples of intense mesoscale systems, such as squall lines, passing over the ships, extending to 13-17 km in altitude, but that nevertheless produce few reports of lightning. This reinforces the idea, based on data from other tropical ocean regions and from global satellite data, that in spite of the ubiquitous 'hot towers' over tropical oceans, marine cumulonimbus produce little lightning. Climatological data from the monsoon regions of the Tropics are analyzed to reveal that during periods of onshore flow and heavy rainfall the oceanic regime of high rainfall but little lightning moves onshore. A rain-thunderstorm ratio is defined and used to characterize convective rainfall regimes as continental (relatively little) or maritime (relatively great) rainfall compared to the number of thunderstorm days. In regions such as West Africa and south Asia, the seasonal rainfall peak is actually accompanied by a thunderstorm minimum. It is further suggested that the data support the idea, not original here, that vertical velocities in oceanic cumulonimbus clouds tend to be low compared with continental clouds. It is hypothesized that most oceanic storms have updrafts weaker than a posssible threshold value, below which the supercooled liquid water, large ice particles, and ice-ice collisions are not present in the mixed-phase region in sufficient concentrations for electrification leading to lightning.

Zipser, Edward J.↗
NASA NTRS2004

A Real-Time Satellite-Based Icing Detection System

Aircraft icing is one of the most dangerous weather conditions for general aviation. Currently, model forecasts and pilot reports (PIREPS) constitute much of the database available to pilots for assessing the icing conditions in a particular area. Such data are often uncertain or sparsely available. Improvements in the temporal and areal coverage of icing diagnoses and prognoses would mark a substantial enhancement of aircraft safety in regions susceptible to heavy supercooled liquid water clouds. The use of 3.9 microns data from meteorological satellite imagers for diagnosing icing conditions has long been recognized (e.g., Ellrod and Nelson, 1996) but to date, no explicit physically based methods have been implemented. Recent advances in cloud detection and cloud property retrievals using operational satellite imagery open the door for real-time objective applications of those satellite datasets for a variety of weather phenomena. Because aircraft icing is related to cloud macro- and microphysical properties (e.g., Cober et al. 1995), it is logical that the cloud properties from satellite data would be useful for diagnosing icing conditions. This paper describes the a prototype realtime system for detecting aircraft icing from space.

Minnis, Patrick↗
NASA NTRS2006

Comparison of Balloonsonde and Remote Sensing Atmospheric Measurements

As part of its aircraft icing research program, the NASA Glenn Research Center is conducting a program to develop technologies for the remote sensing of atmospheric conditions. A suite of instruments, currently ground-based, are used to identify a region of supercooled liquid water which is labeled as hazardous if its liquid water content is sufficiently high. During the recently completed Alliance Icing Research Study (AIRS II), these instruments were deployed in conjunction with those of other U.S. and Canadian researchers at the Mirabel Airport near Montreal. As part of the study, balloonsondes were employed to provide in-situ measurement of the atmospheric conditions that were being concurrently remotely sensed. Balloonsonde launches occurred daily at 1200 GMT to provide AIRS forecasters with local data and additionally when research aircraft were present in the airspace. In this paper, we compare the processed data from the NASA remote sensing instruments, which included an X-band radar, lidar and two radiometers, to the data gathered from the 70 soundings conducted while the NASA instruments were active. Among the parameters compared are cloud upper and lower boundaries, temperature and humidity profiles and freezing levels.

Brinker, David J.↗
NASA NTRS2009

Progress Towards the Remote Sensing of Aircraft Icing Hazards

NASA has teamed with the FAA, DoD, industry, and academia for research into the remote detection and measurement of atmospheric conditions leading to aircraft icing hazards. The ultimate goal of this effort is to provide pilots, controllers, and dispatchers sufficient information to allow aircraft to avoid or minimize their exposure to the hazards of in-flight icing. Since the hazard of in-flight icing is the outcome of aircraft flight through clouds containing supercooled liquid water and strongly influenced by the aircraft s speed and configuration and by the length of exposure, the hazard cannot be directly detected, but must be inferred based upon the measurement of conducive atmospheric conditions. Therefore, icing hazard detection is accomplished through the detection and measurement of liquid water in regions of measured sub-freezing air temperatures. The icing environment is currently remotely measured from the ground with a system fusing radar, lidar, and multifrequency microwave radiometer sensors. Based upon expected ice accretion severity for the measured environment, a resultant aircraft hazard is then calculated. Because of the power, size, weight, and view angle constraints of airborne platforms, the current ground-based solution is not applicable for flight. Two current airborne concepts are based upon the use of either multifrequency radiometers or multifrequency radar. Both ground-based and airborne solutions are required for the future since groundbased systems can provide hazard detection for all aircraft in airport terminal regions while airborne systems will be needed to provide equipped aircraft with flight path coverage between terminal regions.

Reehorst, Andrew↗
NASA NTRS2011

Comparison of In-Situ, Model and Ground Based In-Flight Icing Severity

As an aircraft flies through supercooled liquid water, the liquid freezes instantaneously to the airframe thus altering its lift, drag, and weight characteristics. In-flight icing is a contributing factor to many aviation accidents, and the reliable detection of this hazard is a fundamental concern to aviation safety. The scientific community has recently developed products to provide in-flight icing warnings. NASA's Icing Remote Sensing System (NIRSS) deploys a vertically--pointing Ka--band radar, a laser ceilometer, and a profiling multi-channel microwave radiometer for the diagnosis of terminal area in-flight icing hazards with high spatial and temporal resolution. NCAR s Current Icing Product (CIP) combines several meteorological inputs to produce a gridded, three-dimensional depiction of icing severity on an hourly basis. Pilot reports are the best and only source of information on in-situ icing conditions encountered by an aircraft. The goal of this analysis was to ascertain how the testbed NIRSS icing severity product and the operational CIP severity product compare to pilot reports of icing severity, and how NIRSS and CIP compare to each other. This study revealed that the icing severity product from the ground-based NASA testbed system compared very favorably with the operational model-based product and pilot reported in-situ icing.

Johnston, Christopher J.↗
NASA NTRS2014

NASA Glenn Propulsion Systems Lab: 2012 Inaugural Ice Crystal Cloud Calibration Procedure and Results

The inaugural calibration of the ice crystal and supercooled liquid water clouds generated in NASA Glenn's engine altitude test facility, the Propulsion Systems Lab (PSL) is reported herein. This calibration was in support of the inaugural engine ice crystal validation test. During the Fall of 2012 calibration effort, cloud uniformity was documented via an icing grid, laser sheet and cloud tomography. Water content was measured via multi-wire and robust probes, and particle sizes were measured with a Cloud Droplet Probe and Cloud Imaging Probe. The environmental conditions ranged from 5,000 to 35,000 ft, Mach 0.15 to 0.55, temperature from +50 to -35 F and relative humidities from less than 1 percent to 75 percent in the plenum.

ice clouds↗
NASA NTRS2011

Comparison of In-Situ, Model and Ground Based In-Flight Icing Severity

Currently there are two systems that are being developed for the detection of in-flight icing: NASA Icing Remote Sensing System (NIRSS) and current Icing Product (CIP). In-flight icing (IFI) is a significant hazard for the aviation industry. IFI occurs when supercooled liquid water (SLW) comes in contact with, and freezes to, the leading surfaces of an aircraft. Significantly alters aircraft aerodynamic properties: increases the amount of drag on an aircraft and reduces the lift. The objective of this study is to examine how the testbed NIRSS icing severity product and the operational CIP severity product compare to PIREPs of icing severity, and how the NIRSS and CIP compare to each other.

Serke, David J.↗
NASA NTRS2019

Microphysical Retrievals from Simultaneous Measurements by Airborne and Ground Radars during OLYMPEX

The OLYMPEX field campaign took place over the Olympic Peninsula of Washington during winter 2015-2016. During the intensive observing period, several aircraft flights obtained multi-frequency airborne radar measurements at X-, Ku-, Ka, and W-band from radars aboard the ER-2 and DC-8 aircraft. In addition, ground radars at S- and X-band performed RHI scans under the aircraft ground tracks. These coincident datasets provide a wealth of complementary information about the hydrometeor particle sizes, shapes, and orientations.In order to synthesize these measurements and test the robustness of scattering models, an optimal estimation retrieval based upon a Hitschfeld-Bordan profiling algorithm has been developed. This algorithm retrieves profiles of the particle size distribution parameters Nw and Dm, and, in the ice phase, relative proportions of aggregate, pristine, and rimed particles, using scattering models with different size-density and size-aspect ratio relationships. Under this formulation, only the pristine particles are horizontally aligned and capable of producing non-zero ZDR and KDP.From the nadir-looking airborne multifrequency radars, we find that aggregates may be readily distinguished from rimed and pristine particles owing to their uniqueness in triple-frequency space. However, rimed and pristine particles occupy a similar region in this space and thus polarimetric measurements greatly enhance their identification in our retrieval framework. With these capabilities we will present analyses of three-dimensional hydrometeor mapping obtained during various OLYMPEX cases. Some features retrieved in these cases include a layer of enhanced aggregation about 2km above the melting layer, hypothesized to be maintained by orographic uplift. This layer is often situated above a layer of denser, aligned particles. Regions of riming and supercooled liquid water beneath generating cells are also identified by our retrieval algorithm. Comparisons to in-situ observations and evaluation of scattering models will be presented.

Munchak, S. Joseph↗
NASA NTRSDate not supplied

A Study of Ice-Crystal Icing Erosion Using the NASA Icing Research Tunnel and Propulsion Systems Laboratory

In ice-crystal icing, ice erosion can occur simultaneously with ice accretion. This paper presents a proof-of-concept experimental study that attempts to isolate and quantify ice erosion. The experiments took place at the NASA Icing Research Tunnel and Propulsion Systems Laboratory in 2017 and 2018. The test procedure involved first generating an ice accretion on various NACA 0012 airfoil models using a supercooled liquid water or mixed-phase icing cloud and, subsequently, exposing that ice accretion to an ice crystal cloud. The resulting ice mass decay rates were analyzed in terms of an erosion term, defined as the ratio of the eroded mass flux to impinging mass flux. The erosion term generally increased with airspeed with a value of 1.8% at air velocities of 270 knots and increasing to just over 6% at 360 knots. A preliminary correlation for ice erosion is developed for use in ice accretion models subject to the conditions tested. The study revealed several challenges, both experimental and analytical, including spray bar nozzle freeze-out as well as measurement of the cloud melt ratio to ensure freeze-out.

Icing↗
NASA NTRS2023

Electrification Within Wintertime Stratiform Regions Sampled During the 2020/2022 NASA IMPACTS Field Campaign

Two nor'easter events—sampled during the NASA Investigation of Microphysics and Precipitation for Atlantic Coast-Threatening Snowstorms (IMPACTS) field campaign—were examined to characterize the microphysics in relation to the underlying electrification processes within wintertime stratiform regions. A theoretical model was developed to determine whether accretion or diffusion growth regimes were preferential during periods of greatest electrification. Model simulation with electrification parameterization was used to provide supplemental context to the physical processes of in-cloud microphysics and electrification. The strongest electric fields (i.e., ∼80 V m −1 at 20 km) during the 2020 NASA IMPACTS deployment was associated with large non-rimed ice crystals colliding with each other. During the 29–30 January 2022 science flight, the NASA P-3 microphysical probe data demonstrated that non-inductive charging was possible off the coastline of Cape Cod, Massachusetts. Later in the science flight, when the NASA P-3 and ER-2 were coordinating with each other, measured electric fields consistently were less than 8 V m −1 and electrification was subdued owing to reduced concentrations of graupel and large ice hydrometeors. Altogether, the in-situ observations provide evidence for the non-riming collisional charging mechanism and demonstrates that graupel and supercooled liquid water may not be necessary for weak electrification within wintertime stratiform regions. Model output from simulation of both events suggested that the main synoptic snowbands were associated with elevated hydrometeor snow charge density and electric fields.

snowfall↗
NASA NTRSDate not supplied

Impact Ice Adhesion at NASA Glenn: Current Experimental Methods and Supporting Measurements

When examining the literature on the adhesion strength of impact ice, there have been a wide range of methodologies tried to measure the required stresses to induce interfacial delamination. Utilizing the Icing Research Tunnel at the NASA Glenn Research Center to generate the impact ice required for this work, several different mechanical tests have been and are being developed to determine the stresses along the interface between ice and coupon. This set of tests includes the technical mature modified lap joint test which has been used to conduct ice adhesion studies through a wide sweep of icing conditions. To conduct in situ ice adhesion measurements inside of the Icing Research Tunnel, several new experiments are currently being developed to make ice adhesion measurements during and immediately after ice accretion. In addition to these experimental methods, several supporting measurement techniques have been developed to allow for a better understanding on the influence of icing cloud conditions on the mechanical behavior of impact ice. Digital image correlation has been successfully implemented to augment the data generated by the modified lap joint test with full field surface displacement and strain measurements which allow for insight into the deformation processes present during a test. Both optical microscopy of impact ice samples along with ice replication techniques have been used to study the grain structure of the impact ice. This has led to a deeper understanding of the results from the modified lap joint method and how the structure of impact ice changes as it is accreted during an icing spray. The freezing process of impact ice generated by supercooled liquid water is not a volume conserving process, which leads to the presence of residual strains along the interface between ice and substrate. These strains have been observed using both a simplified flat geometry and a representative airfoil. The data gathered by these experimental adhesion methods and supporting measurements allows for a comprehensive understanding on the behavior of impact ice which will be critical to the development of future ice shedding models.

Ice Adhesion↗
NASA NTRSDate not supplied

Impact Ice Adhesion at NASA Glenn: Current Experimental Methods and Supporting Measurements

When examining the literature on the adhesion strength of impact ice, there have been a wide range of methodologies tried to measure the required stresses to induce interfacial delamination. Utilizing the Icing Research Tunnel at the NASA Glenn Research Center to generate the impact ice required for this work, several different mechanical tests have been and are being developed to determine the stresses along the interface between ice and coupon. This set of tests includes the technical mature modified lap joint test which has been used to conduct ice adhesion studies through a wide sweep of icing conditions. To conduct in situ ice adhesion measurements inside of the Icing Research Tunnel, several new experiments are currently being developed to make ice adhesion measurements during and immediately after ice accretion. In addition to these experimental methods, several supporting measurement techniques have been developed to allow for a better understanding on the influence of icing cloud conditions on the mechanical behavior of impact ice. Digital image correlation has been successfully implemented to augment the data generated by the modified lap joint test with full field surface displacement and strain measurements which allow for insight into the deformation processes present during a test. Both optical microscopy of impact ice samples along with ice replication techniques have been used to study the grain structure of the impact ice. This has led to a deeper understanding of the results from the modified lap join method and how the structure of impact ice changes as it is accreted during an icing spray. The freezing process of impact ice generated by supercooled liquid water is not a volume conserving process, which leads to the presence of residual strains along the interface between ice and substrate. These strains have been observed using both a simplified flat geometry and a representative airfoil. The data gathered by these experimental adhesion methods and supporting measurements allows for a compressive understanding on the behavior of impact ice which will be critical to the development of future ice shedding models.

Ice Adhesion↗
NASA NTRS2024

Cloud Top Phase Characterization of Extratropical Cyclones over the Northeast and Midwest United States: Results from IMPACTS

Cloud top phase (CTP) impacts cloud albedo and pathways for ice particle nucleation, growth, and fallout within extratropical cyclones. This study uses airborne lidar, radar, and Rapid Refresh analysis data to characterize CTP within extratropical cyclones as a function of cloud top temperature (CTT). During the 2020, 2022, and 2023 Investigation of Microphysics and Precipitation for Atlantic Coast-Threatening Snowstorms (IMPACTS) field campaign deployments, the Earth-Resources 2 (ER-2) aircraft flew 26 research flights over the Northeast and Midwest U.S. to sample the cloud tops of a variety of extratropical cyclones. A training dataset was developed to create probabilistic phase classifications based on Cloud Physics Lidar measurements of known ice and liquid clouds. These classifications were then used to quantify dominant CTP in the top 150 m of clouds sampled by the Cloud Physics Lidar in storms during IMPACTS. Case studies are presented illustrating examples of supercooled liquid water at cloud top at different CTT ranges (-3°C -20°C. Liquid-bearing cloud tops were found at CTTs as cold as -37ºC.

Troy J. Zaremba↗
NASA NTRS1951

Analysis of Meteorological Data Obtained During Flight in a Supercooled Stratiform Cloud of High Liquid-Water Content

Flight icing-rate data obtained in a dense and. abnormally deep supercooled stratiform cloud system indicated the existence of liquid-water contents generally exceeding values in amount and extent previously reported over the midwestern sections of the United States. Additional information obtained during descent through a part of the cloud system indicated liquid-water contents that significantly exceeded theoretical values, especially near the middle of the cloud layer.. The growth of cloud droplets to sizes that resulted in sedimentation from the upper portions of the cloud is considered to be a possible cause of the high water contents near the center of the cloud layer. Flight measurements of the vertical temperature distribution in the cloud layer indicated a rate of change of temperature with altitude exceeding that of the moist adiabatic lapse rate. This excessive rate of change is considered to have contributed to the severity of the condition.

Perkins, Porter J.↗
NASA NTRS2022

166 GHZ Ice Scattering Signal in Snowfall Events Over Ocean

Snowfall retrieval algorithms for spaceborne passive microwave (PMW) sensors have been developed and refined in recent years, but many complicating issues still affect their accuracy and reliability. Previous work showed that the Global Precipitation Measurement (GPM) mission Goddard PROFiling (GPROF) algorithm snowfall retrieval performance strongly depends on the snowfall type. In particular, PMW-based detection of shallow cumuliform snowfall (SCS), which accounts for 36%-70% of global snowfall frequency, can be very challenging. The snowfall scattering signal can be contaminated by the background surface or supercooled cloud liquid water emission. A scattering index (SI) approach that exploits the GPM Microwave Imager (GMI) dual-polarization 166 GHz channels is developed to analyze its behavior in presence of SCS over ocean. Case studies show that, compared to the SI at 89 GHz, it can isolate the SCS snowfall scattering signal in extremely dry conditions. Some issues are still observed in presence of supercooled liquid water.

Lisa Milani↗