Crystal Clouds Research Articles

Correlation between Peak Height of Polar Mesospheric Clouds and Mesopause Temperature

Polar mesospheric clouds (PMCs) are ice crystal clouds formed in the mesosphere of high-latitude regions in both the northern (NH) and southern hemispheres (SH). Peak height is an important physical characteristic of PMCs. Satellite observation data from solar occultation for ice experiments (SOFIE) during seven PMC seasons from 2007 to 2014 show that the difference between the height of the mesopause and the peak height of the PMCs (Zmes-Zmax) were inversely correlated with the atmospheric mesopause temperature. The Zmes-Zmax averages for all seasons for the NH and SH were 3.54 km and 2.66 km, respectively. They were smaller at the starting and ending stages of each PMC season and larger in the middle stages. Analysis of the individual cases and statistical results simulated by the PMCs 0-D model also revealed the inverse correlations between the Zmes-Zmax and mesopause temperature, with correlation coefficients of −0.71 and −0.62 for the NH and SH, respectively. The corresponding rates of change of Zmes-Zmax with respect to mesopause temperature were found to be −0.21 km/K and −0.14 km/K, respectively. The formation mechanism of PMCs suggests that a lower temperature around the mesopause can lead to a greater distance and longer time for ice crystals to condense and grow in clouds. Thus, ice crystals sediment to a lower height, making the peak height of the PMCs further away from the mesopause. In addition, disturbances in small-scale dynamic processes tend to weaken the impact of temperature on the peak height of PMCs.

Characteristics of Ice Super Saturated Regions in Washington, D.C. Airspace (2019–2023)

Contrails are estimated to contribute 2% of the Earth’s anthropogenic global warming. Contrails are ice crystal clouds formed by the emission of soot and water vapor from jet engines in atmospheric conditions known as Ice Super Saturated (ISS) regions. The formation of contrails can be avoided by flying over or under the ISS regions. Aircraft operators/dispatchers and air traffic control need to know the location of ISS regions in a given airspace to flightplan to avoid contrails. This paper describes the statistics for the presence of ISS regions in the airspace over metropolitan Washington, D.C. These statistics can be used to better understand the operational implications for contrail avoidance. Based on the measurements taken from the twice-daily launch of an aerosonde from Sterling, Virginia (adjacent to Washington, D.C.), analysis of five years of data (2019–2023) indicated that this airspace experiences ISS regions 40% of the days. ISS regions were equally likely during daylight hours (26%) than nighttime (27%). The vertical depth of the ISS region averaged 3000 feet but with a median of 2000 feet. The ISS region floor and ceiling varied by season, with an annual average floor of FL330 and ceiling of FL360. The implications of these results on the operations to avoid contrails, limitations, and future work are discussed.

Characteristics of Cloud and Aerosol Derived from Lidar Observations during Winter in Lhasa, Tibetan Plateau

In order to investigate the variations of cloud and aerosol vertical profiles over the Tibetan Plateau (TP) in winter, we performed ground-based lidar observations in Lhasa, a city on the TP, from November 2021 to January 2022. The profiles of extinction coefficient, depolarization ratio, and signal-to-noise ratio (SNR) were retrieved using the atmospheric echo signals collected by the lidar. Clouds were identified by the range-correction echo signals and classified into water clouds, mixed clouds, horizontally oriented ice crystal clouds (HOICC), and ice clouds by the depolarization ratio and the hourly temperature from the European Centre for Medium-Range Weather Forecasts Reanalysis version 5 (ERA5). The clouds mainly appeared at a height of 3~5 km from 14:00–22:00 Beijing Time throughout the field campaign. The height and frequency (~30%) for cloud appearance were significantly lower than that reported in previous studies in summer. The cloud categories were dominated by mixed clouds and ice clouds during the observation period. The proportions of ice clouds gradually increased with increasing heights. After eliminating profiles influenced by clouds, the aerosol extinction coefficient and depolarization ratio were obtained, and the atmospheric boundary layer height (ABLH) was calculated. The aerosol extinction coefficient decreased with increasing height in the ABLH, and there were no obvious changes for the aerosol extinction coefficient above the ABL. The aerosol extinction coefficients near the Earth’s surface presented two peaks, appearing in the morning and evening, respectively. The high aerosols at the surface in the morning continually spread upward for 4–5 h and finally reached an altitude of 1 km with the development of ABLH. In addition, the depolarization ratio of aerosols decreased slowly with increasing altitudes. There was no obvious diurnal variation for depolarization ratios, indicating partly that the source of aerosols did not change significantly. These results are beneficial in understanding the evolution of cloud and aerosol vertical profiles over the TP.

Monte Carlo Method for Numerical Simulation of Solar Energy Radiation Transfer in Crystal Clouds

Monte Carlo Method for Numerical Simulation of Solar Energy Radiation Transfer in Crystal Clouds

Electrochemical sensing of Hg(ii) in chicken liver and snail shell extract samples using novel modified SDA/MWCNT electrodes.

Heavy metal ions (Hg(ii)) were detected in fresh chicken liver and snail shell extract samples using novel synthesised SDA/MWCNT-modified electrodes. The synthesized N,N'-bis(salicylaldehyde)-1,2-diaminobenzene (SDA) ligand was characterized via FT-IR, 1H-NMR, and 13C-NMR spectroscopy. The hydroxyl and imine functional groups present in SDA act as active sites and bind to the MWCNT surface. The surface morphology of the modified SDA/MWCNT electrode exhibited a star-like crystal structure and the preconcentration of Hg(ii)-SDA/MWCNTs lead to a crystal cloud structure, as characterized by SEM with EDX. The enhancement of current and conductance of the SDA/MWCNT- and MWCNT-modified electrode was investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The conductance (σ) values for the MWCNT- and SDA/MWCNT-modified electrodes are 234.1 × 10-5 S cm-1 and 358.4 × 10-5 S cm-1, respectively, as determined by electrochemical impedance spectroscopy. Consequently, an electrochemical sensor with outstanding performance in terms of reproducibility, stability and anti-interference ability was fabricated. The stripping analysis of Hg(ii) was performed using square wave anodic stripping voltammetry (SWASV) and cyclic voltammetry (CV). Using SWASV, a linear range of Hg(ii) response was found to be 1.3 to 158 μg L-1, and the limit of detection (LOD) was 0.24 μg L-1. Finally, the results of the recovered value of Hg(ii) in freshly prepared chicken liver and snail shell extract samples by SWASV were compared with the atomic absorption spectroscopy (AAS) results.

Effect of Shape and Sizes of Crystal Particles on Angular Distributions of Transmitted Solar Radiation in Two Sensing Geometries: Results of Numerical Simulation

The results of statistical simulation of intensity of transmitted solar radiation in the presence of optically thin cirrus clouds for two sensing geometries: in solar almucantar and hybrid scan (AERONET photometric network) are considered. Numerical experiments were performed using ice crystal cloud models: OPAC (hexagonal particles with a smooth surface) and a model proposed by Baum et al. (а mixture of particles with different shapes, hexagonal columns and aggregates of hexagonal columns with a very rough surface). The effects of shape and size of ice crystals on the angular distributions of downward radiation in the wavelength channels of 440 and 870 nm are estimated for background atmospheric situations observed in Tomsk in the summer period.

Analysis of the Honeywell Uncertified Research Engine With Ice Crystal Cloud Ingestion at Simulated Altitudes

Abstract The Honeywell Uncertified Research Engine (HURE), a research version of a turbofan engine that never entered production, was tested in the NASA Propulsion Systems Laboratory (PSL), an altitude test facility at the NASA Glenn Research Center. The PSL is a facility that is equipped with water spray bars capable of producing an ice cloud consisting of ice particles, having a controlled particle diameter and concentration in the airflow. To develop the test matrix of the HURE, the numerical asw analysis of flow and ice particle thermodynamics was performed on the compression system of the turbofan engine to predict operating conditions that could potentially result in a risk of ice accretion due to ice crystal ingestion. The goal of the test matrix was to provide operating conditions such that ice would accrete either in the fan-stator through the inlet guide vane region of the compression system or within the first stator of the high-pressure compressor. The predictive analyses were performed with the mean-line compressor flow modeling code (comdes-melt) which includes an ice particle model. The HURE engine was tested in PSL with the ice cloud over the range of operating conditions of altitude, ambient temperature, simulated flight Mach number, and fan speed with guidance from the analytical predictions. The engine was fitted with video cameras at strategic locations within the engine compression system flow path where ice was predicted to accrete in order to visually confirm ice accretion when it occurred. In addition, traditional compressor instrumentation, such as total pressure and temperature probes, static pressure taps, and metal temperature thermocouples, were installed in targeted areas where the risk of ice accretion was expected. The current research focuses on the analysis of the data that were obtained after testing the HURE engine in PSL with ice crystal ingestion. The computational method (comdes-melt) was enhanced by computing key parameters through the fan-stator at multiple spanwise locations in order to increase the fidelity with the current mean-line method. The Icing Wedge static wet-bulb temperature thresholds were applied for determining the risk of ice accretion in the fan-stator, which is thought to be an adiabatic region. At some operating conditions near the splitter–lip region, other sources of heat (non-adiabatic walls) were suspected to be the cause of accretion, and the Icing Wedge was not applied to predict accretion at that location. A simple order-of-magnitude heat transfer model was implemented into the comdes-melt code to estimate the wall temperature minimum and maximum thresholds that support ice accretion, as observed by video confirmation. The results from this model spanned the range of wall temperatures measured on a previous engine that experienced ice accretion at certain operating conditions. The goal of this study is to show that the computational process developed on earlier engine icing tests can be used to provide an icing risk assessment in adiabatic regions for other engines.

Simulation of solar radiation brightness fields in the presence of optically anisotropic crystal clouds: algorithm and test results

Simulation of solar radiation brightness fields in the presence of optically anisotropic crystal clouds: algorithm and test results

Evaluation of Cloud Top Height Retrievals from China’s Next-Generation Geostationary Meteorological Satellite FY-4A

To evaluate the validity of cloud top height (CTH) retrievals from FY-4A, the first of China’s next-generation geostationary meteorological satellite series, the retrievals are compared to those from Himawari-8, CloudSat, Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), and Moderate Resolution Imaging Spectroradiometer (MODIS) operational products from August to October 2017. Regarding CTHs from CloudSat, CALIPSO, and MODIS as truth, the results show that the performance of FY-4A CTH retrievals is similar to that of Himawari-8. Both FY-4A and Himawari-8 retrieve reasonable CTH values for single-layer clouds, but perform poorly for multi-layer clouds. The mean bias error (MBE) shows that the mean value of FY-4A CTH retrievals is smaller than that of Himawari-8 for single-layer clouds but larger for multi-layer clouds. For ice crystal clouds, both FY-4A and Himawari-8 obtain the underestimated CTHs. However, there is a tendency for FY-4A and Himawari-8 to overestimate the CTH values of CloudSat and CALIPSO mainly for low level liquid water clouds. The temperature inversion near the tops of water clouds may result in an overestimation of CTHs. According to the MBE change with altitude, FY-4A and Himawari-8 overestimate the CTHs mainly for clouds below 3 km, and the overestimation is slightly more apparent in Himawari-8 data than that in FY-4A values. As the cloud optical thickness (COT) increases, the CTH bias of FY-4A CTH retrievals gradually decreases. Two typical cases are analyzed to illustrate the differences between different satellites’ CTH retrievals in detail.

Radiant Energy Extinction in the Radiative Transfer Equation for Crystal Clouds

Systematic information on the application of the extinction formalization of different types for solving the equation of radiative transfer in a crystal cloud is presented. The basic laws of visible and infrared radiation extinction are illustrated that provide the basis for the assessment of the extent with which the special features of the energy and polarization extinction characteristics formed by crystals with different microphysical, optical, and orientational parameters must be taken into account. It is shown that large plates with preferred orientation stand out among crystals of all types in the degree and stability of manifestation of the polarization extinction characteristics and their spectral dependence. For such particles, the polarization extinction effect can be higher by several orders of magnitude and constitute more than 50% of the energy characteristic of the extinction.

Mathematical aspects in the meteorological interpretation of satellite hyperspectral infrared measurements part II: estimates of the cloud absorption vertical profile of Hurricane Ioke on 28 August 2006

ABSTRACTThis study processes and analyses hyperspectral measurements from the Atmospheric Infrared Sounder on 28 August 2006 covering day and night scenes of Hurricane Ioke with a temporal spacing of 12 hours. A semi-discrete multilevel cloud model is used to describe the perturbation of the outgoing thermal radiation caused by cloudiness in the field of view (FOV) of a satellite instrument. Cloud spectral effects in the model are represented by an effective cloud absorption vertical profile (CAVP). The CAVP estimate is considered an indicator of the presence of clouds at specific atmospheric layers. The CAVP estimates are compared with lidar measurements. Results indicate a realistic characterization of cloud top and cloud vertical scale. The spatial distribution of the CAVP estimates is used to describe the spatial structure of the hurricane and to monitor its changes over time.Comparison of daytime and night-time CAVP estimates shows that the effective hurricane radius is drastically reduced from about 578 km during the day to about 463 km at night at an atmospheric layer above 212 hPa and from about 604 km to about 499 km at atmospheric layer above 300 hPa. In addition, there is indication of a significant presence of ice crystals in the upper troposphere 10–14 km at night over the large areas adjacent to the hurricane. These crystal clouds have the potential to affect the hurricane energy budget by reducing the night-time cooling rate and trapping heat and moisture in the lower atmospheric layers.

Optical characteristics of irregular atmospheric ice columns

The study of cirrus clouds, which significantly affect the climate, is carried out using lidars. Interpretation of the lidar data is based on the direct solution of the problem of light scattering by particles of crystal clouds. Optical characteristics of perfect ice hexagonal columns, obtained previously, poorly agree with the lidar observation results. The work describes calculations of the optical characteristics of irregular hexagonal ice columns, which are in a good agreement with the experimental results. The calculations for particles with deformation of a dihedral angle of 90° are presented. It is shown that the logarithm of the scattering matrix can be linearly approximated well by the logarithm of the particle size. This can significantly accelerate the calculations of the optical characteristics of clouds. It is ascertained that the optical characteristics are in a good agreement with the lidar observation results throughout the range of sizes calculated even at deformation angles of a few degrees.

Numerical study of influence of different dispersed components of crystal cloud on transmission of radiant energy

The calculated results of the transmission of visible and infrared radiation by an atmosphere layer involving ensembles of large preferentially oriented crystals and spherical particles are presented. To calculate extinction characteristics, the physical optics method and the Mie theory are applied. Among all atmospheric particles, both the small particles that are commensurable with the wavelength of the incident radiation and the large plates and the columns are distinguished by the most pronounced dependence of the transmission on spectra of radiant energy. The work illustrates features of influence of parameters of the particle size distribution, particle aspect ratios, orientation and particle refractive index, also polarization state of the incident radiation on the transmission. The predominant effect of the plates on the wavelength dependence of the transmission is shown. A separated and cooperative contributes of the large plates and the small volume shape particles to the common transmission by medium are considered.

Growth of ice particle mass and projected area during riming

Abstract. There is a long-standing challenge in cloud and climate models to simulate the process of ice particle riming realistically, partly due to the unrealistic parameterization of the growth of ice particle mass (m) and projected area (A) during riming. This study addresses this problem, utilizing ground-based measurements of m and ice particle maximum dimension (D) as well as theory to formulate simple expressions describing the dependence of m and A on riming. It was observed that β in the m − D power law m = α Dβ appears independent of riming during the phase 1 (before the formation of graupel), with α accounting for the ice particle mass increase due to riming. This semi-empirical approach accounts for the degree of riming and renders a gradual and smooth ice particle growth process from unrimed ice particles to graupel, and thus avoids discontinuities in m and A during accretional growth. Once the graupel with quasi-spherical shape forms, D increases with an increase in m and A (phase 2 of riming). The treatment for riming is explicit, and includes the parameterization of the ice crystal–cloud droplet collision efficiency (Ec) for hexagonal columns and plates using hydrodynamic theory. In particular, Ec for cloud droplet diameters less than 10 µm are estimated, and under some conditions observed in mixed-phase clouds, these droplets can account for roughly half of the mass growth rate from riming. These physically meaningful yet simple methods can be used in models to improve the riming process.

A WRF Simulation of an Episode of Contrails Covering the Entire Sky

On 21 September 2012 the entire sky was covered by contrails over the Gulf of Lyon (NW of the Mediterranean basin). These clouds were well recorded by ground observers as well as by Meteosat imagery. The atmospheric characteristics at the levels where these anthropic clouds formed are analyzed by performing a WRF simulation in the area where Meteosat recorded contrail clouds. According to the vertical profiles of temperature and the relative humidity respect to the ice (RHI), the environmental condition favors that the water vapor exhaust emitted by the aircraft engines reaches the deposition point and form crystal clouds, which spread out because the temperature remained below 230 K and the RHI was higher than 70% during the whole episode.

ALLURE OF THE "CRYSTAL: MYTHS AND METAPHORS IN ARCHITECTURAL MORPHOGENESIS

'Form' has always been one of the most important issues in architectural design. In the process of form-giving to the end-product, architects make use of different sources from typologies to intuitions or metaphorical ones. When the generic ideas of the prominent examples in architectural history have been traced, it can clearly be stated that one of the most effective metaphors used in architecture is the 'Crystal.' Appearing at the intersections between nature and human history and having a long history going back to myths, the 'Crystal' has been used extensively in architecture both as reflecting the meaning originating from its mythical background, and also, as a metaphor representing the perfection in nature. This article will try to trace the use of 'crystal' metaphor in history and analyzing the two examples, namely, the Royal Ontario Museum: 'Crystal' in Toronto (2007) by Daniel Libeskind and Musée des Confluences: 'Crystal Cloud of Culture' in Lyon (2014) by Coop Himmelb(l)au, will try to evaluate the change in the use of crystal metaphor in contemporary architectural morphogenesis.

Icing of aircraft engines in ice crystal clouds: A case study

Analyzed is a serious flight accident with a Boeing-747 aircraft happened on July 31, 2013 during its flight from Moscow to Hong Kong. The plane entered the upper crystal part of the mesoscale convective complex (MCC) and got damaged the compressors of three engines. This is considered to be caused by the so called ice crystal icing in the areas with high concentration of ice crystals. Considered are meteorological conditions in the corresponding part of the flight route and available information about this type of icing. To prevent aircrafts from ice crystal icing, special attention should be paid to very short-range forecasting, now casting, and detection of zones of deep intense convection, especially of MCC along the flight route.

Transformation of light backscattering phase matrices of crystal clouds depending on the zenith sensing angle

Problems encountered in the interpretation of results of laser sensing of crystal clouds are considered. The parameters characterizing the cloud particle orientation are determined through the backscattering phase matrix elements. It is demonstrated how these parameters are related to the probability density of particle distribution over the spatial orientation angles. Trends in the change of the backscattering phase matrices attendant to variations of the zenith sensing angle are shown on the example of a monodisperse ice particle ensemble.

The Non-linear Modeling of the Rotational Vibrations of the Electrically Charged Cloud of the Ice Crystals

The paper presents derivation of non-linear model of vibrations of electrically charged cloud of ice crystals. This problem is applicable as mechanical basis of a theoretical model of atmospheric optical phenomenon commonly known as the miracle of Sun. A large crystal rotation angles and a continuous distribution of charges on surface of crystals are included in deliberations. It is shown that obtained equation of non-linear model is type of equation  4 . The numerical solutions are shown for some examples of model parameter sets. They are compared with solutions of linear model available in literature. Finally, obtained theoretical results have been compared with results of observations of atmospheric phenomenon called the miracle of Sun available in literature.

Clear-air Seeding: Opportunities and Strategies

Clear-air seeding is the artificial creation or enhancement of cloud cover in clear air which is between saturation with respect to ice and saturation with respect to liquid water. Previous work has demonstrated that clear-air seeding is possible, and may be economically worthwhile through its effects on the radiation balance near the ground. Order-of-magnitude arguments, contrail observations and direct measurements are used to assess the frequency and horizontal extent of opportunities for clear-air seeding in the upper troposphere. Clear, ice-supersaturated air is a common occurrence in the mid-latitude upper troposphere at all times of year, typically appearing over 100 km-wide regions downstream of cyclonic or convective storm systems. The frequency of opportunities was also estimated for a particular application of clear-air seeding-cloud cover enhancement during winter nights to reduce space heating costs. Opportunities were studied for the middle and lower troposphere through a careful analysis of radiosonde humidity data, and for the upper troposphere through observalions of natural cirrus. Under suitable cloud cover and wind conditions, five to ten opportunities each season are estimated for locations in the northeastern United States, a frequency sufficient for economic advanlage based on a previous analysis. Two methods are discussed for seeding clear, ice-superssLurated air to create clouds. Seeding with ice crystals is studied using a numerical simulation of ice crystal cloud growth, which includes both ice physics and radiative transfer. Ice crystal seeding is most effective when the seeding rate is greatest and the moist layer seeded is deepest. Aircraft contrails generally utilize only a small fraction of the available water vapor in excess of ice saturation, before they settle out of the moist layer in which they were created. The development of clouds seeded with ice-nucleating aerosols, rather than ice crystals, depends greatly on the rate at which the seed material nucleates ice crystals. This type of seeding would produce a longer lasting, lower density cloud than would seeding with ice crystals.