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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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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Evaluation of the response of tritium-in-air instrumentation to HT in dry and humid conditions and to HTO vapor

Nuclear plant operators (power generation, decommissioning and reprocessing operations) are required to monitor releases of tritium species for regulatory compliance and radiation protection purposes. Tritium monitoring is performed using tritium-in-air gas monitoring instrumentation based either on flow-through ion chambers or proportional counting systems. Tritium-in-air monitors are typically calibrated in dry conditions but in service may operate at elevated levels of relative humidity. The NPL (National Physical Laboratory) radioactive gas-in-air calibration system has been used to study the effect of humidity on the response to tritium of two tritium-in-air ion chamber based monitors and one proportional counting system which uses a P10/air gas mixture. The response of these instruments to HTO vapour has also been evaluated. In each case, instrument responses were obtained for HT in dry conditions (relative humidity (RH) about 2%), HT in 45% RH, and finally HTO at 45% RH. Instrumentation response to HT in humid conditions has been found to slightly exceed that in dry conditions. (authors)

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2016

Compact Buried Ducts in a Hot-Humid Climate House

"9A system of compact, buried ducts provides a high-performance and cost-effective solution for delivering conditioned air throughout the building. This report outlines research activities that are expected to facilitate adoption of compact buried duct systems by builders. The results of this research would be scalable to many new house designs in most climates and markets, leading to wider industry acceptance and building code and energy program approval. The primary research question with buried ducts is potential condensation at the outer jacket of the duct insulation in humid climates during the cooling season. Current best practices for buried ducts rely on encapsulating the insulated ducts with closed-cell spray polyurethane foam insulation to control condensation and improve air sealing. The encapsulated buried duct concept has been analyzed and shown to be effective in hot-humid climates. The purpose of this project is to develop an alternative buried duct system that performs effectively as ducts in conditioned space - durable, energy efficient, and cost-effective - in a hot-humid climate (IECC warm-humid climate zone 3A) with three goals that distinguish this project: 1) Evaluation of design criteria for buried ducts that use common materials and do not rely on encapsulation using spray foam or disrupt traditional work sequences; 2) Establishing design criteria for compact ducts and incorporate those with the buried duct criteria to further reduce energy losses and control installed costs; 3) Developing HVAC design guidance for performing accurate heating and cooling load calculations for compact buried ducts.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2017

Biases of the MET Temperature and Relative Humidity Sensor (HMP45) Report

The U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility Data Quality (DQ) Office was alerted to a potential bias in the surface meteorological instrumentation (MET) temperature when compared with a nearby Mesonet station. This led to an investigation into this problem that was expanded to include many of the other extended facilities (EF) and both the temperature and relative humidity (RH) variables. For this study, the Mesonet was used as the standard reference due to results that showed an increased accuracy in high-humidity environments along with the fact that the Mesonet had previous documented a problem with the HMP45C sensors. Some differences between the sites were taken into account during the analysis: 1. ARM MET sensors were upgraded from an HMP35 to an HMP45 throughout 2007 2. Mesonet switched to aspirated shields in 2009 – To mitigate the differences between aspirated and non-aspirated measurements, data were only analyzed when the wind speed was higher than 3 m/s. This reduced the uncertainty for the non-aspirated measurements from 1.51 ºC to 0.4 ºC. 3. ARM MET is mounted 0.5m higher than the Mesonet station (2.0m versus 1.5m) – This is assumed to have a negligible effect on the differences. 4. Sites were not co-located – For some locations, the distances between sites were as much as 45 km. As part of the investigation into the differences, the Mesonet had reported that the HMP45 sensors had a low-temperature bias in high-humidity environments. This was verified at two different sites where the ARM measurements were compared with the Mesonet measurements. The Mesonet provided redundant temperature measurements from two different sensors at each site. These measurements compared fairly well, while the ARM sensor showed a bias overnight when the humidities were higher. After reviewing the yearly average differences in the data and analyzing the RH data during fog events when we assume it should be 100%, we determined that a majority of the sites have a bias in the RH compared to the Mesonet sites, but that only a few sites show a bias in the temperature measurements that are outside the range of instrument uncertainties. We note that there can be a lot of variability across some of the distances between the MET and Mesonet sites and these biases reported herein should not be used as offsets.

47 OTHER INSTRUMENTATION↗
NASA NTRS2020

Effect of Irrigation on Humid Heat Extremes

Most studies of irrigation as an anthropogenic climate forcing focus on its cooling effects. However, irrigation also increases humidity, and so may not ameliorate humid heat and its extremes. We analyzed global climate model results over hot locations and seasons at high temporal resolution to estimate the impact of irrigation on humid heat extremes, quantified as different percentiles of wet-bulb temperature (T(sub w)), under contemporary conditions. We found that although irrigation reduced temperature, the median and higher percentiles of T(sub w) on average did not decrease. Increases in T(sub w) percentile values and increases in frequency of dangerous T(sub w) of several days per year due to irrigation were found in some densely populated regions, including the central United States and the Middle East, while the Ganges basin saw reduced T(sub w). Changes in T(sub w) were partly associated with the differential regional impacts of irrigation on moisture transport. These results underline the importance of considering impacts of climate forcings on humidity as well as temperature in evaluating associated effects on heat extremes.

Irrigation↗
DOE OSTI2016

Building America Case Study: Compact Buried Ducts in a Hot-Humid Climate House, Lady's Island, South Carolina

A system of compact, buried ducts provides a high-performance and cost-effective solution for delivering conditioned air throughout the building. This report outlines research activities that are expected to facilitate adoption of compact buried duct systems by builders. The results of this research would be scalable to many new house designs in most climates and markets, leading to wider industry acceptance and building code and energy program approval. The primary research question with buried ducts is potential condensation at the outer jacket of the duct insulation in humid climates during the cooling season. Current best practices for buried ducts rely on encapsulating the insulated ducts with closed-cell spray polyurethane foam insulation to control condensation and improve air sealing. The encapsulated buried duct concept has been analyzed and shown to be effective in hot-humid climates. The purpose of this project is to develop an alternative buried duct system that performs effectively as ducts in conditioned space - durable, energy efficient, and cost-effective - in a hot-humid climate (IECC warm-humid climate zone 3A) with three goals that distinguish this project: 1) Evaluation of design criteria for buried ducts that use common materials and do not rely on encapsulation using spray foam or disrupt traditional work sequences, 2) Establishing design criteria for compact ducts and incorporate those with the buried duct criteria to further reduce energy losses and control installed costs, and 3) Developing HVAC design guidance for performing accurate heating and cooling load calculations for compact buried ducts.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2017

An XPS study on the impact of relative humidity on the aging of UO 2 powders

High resolution x-ray photoemission spectroscopy (XPS) was used to characterize the chemical speciation of high purity uranium dioxide (UO 2 ) powder samples following aging for periods of up to one year under controlled conditions with relative humidity ranging from 34% to 98%. A systematic shift to higher uranium oxidation states, and thus an increase in the mean uranium valence, was found to directly correlate with the dose of water received (i.e. the product of exposure time and relative humidity). Exposure duration was found to have a greater impact on sample aging than relative humidity. Lastly, the sample aged at 98% relative humidity was found to have unique structural differences for exposure time beyond 180 days when observed by scanning electron microscopy (SEM).

36 MATERIALS SCIENCE↗
DOE OSTI2021

Adsorption of Iodine on Metal Coupons in Humid and Dry Environments

In this study, five different metal coupons were evaluated for gaseous iodine [I2(g)] adsorption including two stainless steels (i.e., SS304 and SS316), two Inconel® alloys (i.e., 625 and 718) and pure Ni (i.e., Ni-200) within a dynamic flow-through system where temperature, iodine concentration, flow rate, atmosphere, and relative humidity were controlled. Humidity was shown to be critical to iodine adsorption on SS304 and SS316 and Ni-200 at ambient temperatures. The results presented herein suggest that a moisture mediated reaction is occurring. However, higher humidity levels decrease the adsorption, suggesting an ideal range of humidity for highest corrosion. A comparison of the five metal substrates showed the highest I2(g) adsorption in the following descending order Ni-200 > SS304 > SS316 >718>625.The 625 and 718 Inconel alloys were fairly inert to iodine adsorption under the conditions tested. Characterization by scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction of the Ni-200 coupon indicates that NiI2 is formed and flakes off the surface as a black powder. The SS304 and SS316 coupons showed evidence of extensive reactions with I2(g) and formed a much more deliquescent corrosion product, which reacted with air when removed from the flow-through system for weighing on the analytical balance. These findings assist in predicting iodine adsorption behavior on a variety of metal surfaces under various conditions.

Beck, Chelsie L.↗
DOE OSTI2024

High protonic resistance of hydrocarbon-based cathodes in PEM fuel cells under low humidity conditions: Origin, implication, and mitigation

Hydrocarbon-based electrodes for proton-exchange membrane fuel cells face challenges in closing the performance gap with electrodes based on perfluorosulfonic acid ionomers, particularly under low humidity conditions. Alongside increased oxygen transport resistance and higher kinetic-induced overpotentials, the protonic resistance of these fluorine-free electrodes is the primary hurdle to improved performance. This study systematically investigates the origin and impact of the cathode protonic resistance on fuel cell performance, utilizing sulfonated phenylated polyphenylenes as hydrocarbon ionomers. Electrochemical characterization at low relative humidity (≤50 %) reveal a high protonic resistance arising from both lower conductivity of the hydrocarbon thin film compared to the bulk membrane and increased cathode tortuosity at a gas transport-optimized ionomer to carbon (I/C) ratio of 0.2. The poor protonic resistance at low relative humidities leads to a non-homogeneous current distribution across the thickness of the cathode electrode, resulting in lower catalyst utilization. To address this issue, reducing the thickness of the cathode CL while maintaining a constant Pt loading (i.e., increasing the Pt on carbon ratio) significantly reduces protonic resistance. This improvement compensates for the kinetic disadvantages of highly loaded carbon particles and results in a considerable performance increase by 40 % at 0.75 V under low relative humidities.

25 ENERGY STORAGE↗
DOE OSTI2021

Long-term thermal aging of parylene conformal coating under high humidity and its effects on tin whisker mitigation

Usage of pure tin (Sn) or Sn-rich alloy in electronics industry is growing, which makes them more susceptible to the spontaneous growth of tin whiskers. The risk of having these whiskers can be dramatically mitigated by applying a conformal coating provided that it not only possesses excellent mechanical and adhesion properties but also maintains these properties throughout their service. Parylene C is commonly used as a conformal coating because of its favorable mechanical and physical properties, as well as superior conformal coverage. The purpose of this paper is to investigate the degradation of parylene C coating during the thermal aging in high humidity environment (85°C/85% relative humidity for up to 5000hrs) and its effect on the tin whisker mitigation capacity. It was observed that during aging at high temperature and high humidity (HTHH) environment, the oxidation occurs at early times, followed by bond scission, resulting in the loss of strength of the coating. Thinner parylene coating (12.5-μm-thick) had better coating adhesion on the silane-treated tin surface, so provided the better protection for tin whisker penetration than the thicker counterpart (25-μm-thick). After 2500hrs of aging, due to the degradation of the silane agent at the tin/parylene interface, the adhesion of the parylene coating was significantly weakened on the tin surface, which resulted in extensive corrosion of the tin solderpads. The loss of adhesion of the coating, along with the corrosion of the tin surface facilitated the tin whisker nucleation at the interface while the loss of mechanical strength and the brittleness made the coating easily penetrated by the growing whiskers. Tin whiskers with a smaller diameter were buckled and grew along the delaminated region while those with a larger diameter penetrated and continued to grow through the coating. Hence, the effectiveness of the parylene coatings on tin whisker mitigation is significantly reduced under long exposure to such high temperature and high humidity.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Reaction Layer Formation on MgO in the Presence of Humidity

Mineralization by MgO is an attractive potential strategy for direct air capture (DAC) of CO 2 due to its tendency to form carbonate phases upon exposure to water and CO 2 . Hydration of MgO during this process is typically assumed to not be rate limiting, even at ambient temperatures. However, surface passivation by hydrated phases likely reduces the CO 2 capture capacity. Here, we examine the initial hydration reactions that occur on MgO(100) surfaces to determine whether they could potentially impact CO 2 uptake. We first used atomic force microscopy (AFM) to explore changes in reaction layers in water (pH = 6 and 12) and MgO-saturated solution (pH = 11) and found the reaction layers on MgO are heterogeneous and nonuniform. To determine how relative humidity (R.H.) affects reactivity, we reacted samples at room temperature in nominally dry N 2 (~11–12% R.H.) for up to 12 h, in humid (>95% R.H.) N 2 for 5, 10, and 15 min, and in air at 33 and 75% R.H. for 8 days. X-ray reflectivity and electron microscopy analysis of the samples reveal that hydrated phases form rapidly upon exposure to humid air, but the growth of the hydrated reaction layer slows after its initial formation. Reaction layer thickness is strongly correlated with R.H., with denser reaction layers forming in 75% R.H. compared with 33% R.H. or nominally dry N 2 . The reaction layers are likely amorphous or poorly crystalline based on grazing incidence X-ray diffraction measurements. After exposure to 75% R.H. in air for 8 days, the reaction layer increases in density as compared to the sample reacted in humid N 2 for 5–15 min. Further, this may represent an initial step toward the crystallization of the reaction layer. Overall, high R.H. favors the formation of a hydrated, disordered layer on MgO. Based on our results, DAC in a location with a higher R.H. will be favorable, but growth may slow significantly from initial rates even on short timescales, presumably due to surface passivation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Optical Fiber Sensor with a Hydrophobic Filter Layer for Monitoring Hydrogen under Humid Conditions

Real-time and remote monitoring of hydrogen concentration in underground hydrogen storage reservoirs is crucial to maintaining the integrity and safety of the storage facilities. High humidity in the underground deposits interferes with hydrogen sensors, introducing inaccuracy into the hydrogen sensing measurements. A hydrophobic filter layer over a hydrogen sensing layer on an optical fiber hydrogen sensor was devised to minimize the impact of the humidity on the sensor. The hydrogen sensor coated with a hydrophobic filter layer demonstrated a significant improvement in reliable hydrogen sensing under high humidity conditions (99% RH) without severe baseline drift and reduction of transmission intensity. Finally, the optical fiber hydrogen sensor revamped with the filter layer would enable the reliable measurement of hydrogen concentration under the humid conditions expected in subsurface hydrogen storage facilities.

08 HYDROGEN↗
DOE OSTI2015

Properties of Ammonium Ion–Water Clusters: Analyses of Structure Evolution, Noncovalent Interactions, and Temperature and Humidity Effects

Although ammonium ion–water clusters are abundant in the biosphere, some information regarding these clusters, such as their growth route, the influence of temperature and humidity, and the concentrations of various hydrated clusters, is lacking. In this study, theoretical calculations are performed on ammonium ion–water clusters. These theoretical calculations are focused on determining the following characteristics: (1) the pattern of cluster growth; (2) the percentages of clusters of the same size at different temperatures and humidities; (3) the distributions of different isomers for the same size clusters at different temperatures; (4) the relative strengths of the noncovalent interactions for clusters of different sizes. The results suggest that the dipole moment may be very significant for the ammonium ion–water system, and some new stable isomers were found. The nucleation of ammonium ions and water molecules is favorable at low temperatures; thus, the clusters observed at high altitudes might not be present at low altitudes. High humidity can contribute to the formation of large ammonium ion–water clusters, whereas the formation of small clusters may be favorable under low-humidity conditions. The potential energy surfaces (PES) of these different sized clusters are complicated and differ according to the distribution of isomers at different temperatures. Some similar structures are observed between NH4+(H2O)n and M(H2O)n (where M represents an alkali metal ion or water molecule); when n = 8, the clusters begin to form the closed-cage geometry. As the cluster size increases, these interactions become progressively weaker. The successive binding energy at the DF-MP2-F12/VDZ-F12 level is better than that at the PW91PW91/6-311++G(3df, 3pd) level and is consistent with the experimentally determined values.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2018

Observational Relationship between Entrainment Rate and Environmental Relative Humidity and Implications for Convection Parameterization

Entrainment rate is a critical but highly uncertain quantity in convective parameterizations; especially, the effects of environmental relative humidity on entrainment rate are controversial, or even opposite, in different studies. Analysis of aircraft observations of cumuli from the RACORO and RICO field campaigns shows that entrainment rate is positively correlated with relative humidity. Physical analysis shows that higher relative humidity promotes entrainment by reducing buoyancy in the cloud cores and by weakening downdrafts near the cloud cores. The reduced buoyancy in the cloud cores and weakened downdrafts surrounding the cores further reduce updrafts in the cloud cores; the cloud cores with smaller updrafts are more significantly affected by their environment, resulting in larger entrainment rate. The relationship between entrainment rate and relative humidity is consistent with the buoyancy sorting concept widely used in convection parameterizations. The results provide reliable in situ observations to improve parameterizations of entrainment rate.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Revisiting Recent U.S. Heat Waves in a Warmer and More Humid Climate

The frequency and intensity of heat waves in the United States is projected to increase in the 21st century. We investigate dry and humid heat waves in a pair of high-resolution model simulations that constrain large-scale atmospheric circulation, to isolate the thermodynamic impacts on characteristics of present and future heat waves over the United States. The two kinds of heat waves show differences in mean intensity, amplitude, duration, and frequency over the Southeast, Northeast, and Midwest, while their characteristics are largely similar in the drier central and western United States. In a warmer climate, relative humidity is projected to decrease during dry heat waves, whereas it remains unchanged during humid heat waves. However, the overall increase in daily maximum temperature intensifies the heat stress during future humid and dry heat waves across all regions. With large-scale circulation constrained, these simulations emphasize the importance of thermodynamic drivers in determining future heat wave characteristics.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

The Evolving Distribution of Relative Humidity Conditional Upon Daily Maximum Temperature in a Warming Climate

Abstract The impacts of heat waves in a warming climate depend not only on changing temperatures but also on changing humidity. Using 35 simulations from the Community Earth System Model Large Ensemble (CESM LENS), we investigate the long‐term evolution of the joint distribution of summer relative humidity (RH) and daily maximum temperature ( Tmax ) near four U.S. cities (New York City, Chicago, Phoenix, and New Orleans) under the high‐emissions Representative Concentration Pathway (RCP) 8.5. We estimate the conditional quantiles of RH given Tmax with quantile regression models, using functions of temperature for each city in July for three time periods (1990–2005, 2026–2035, and 2071–2080). Quality‐of‐fit diagnostics indicate that these models accurately estimate conditional quantiles for each city. As expected, each quantile of Tmax increases from 1990–2005 to 2071–2080, while mean RH decreases modestly. Conditional upon a fixed quantile of Tmax , the median and high quantiles of RH decrease, while those of the Heat Index (HI) and dew point both increase. This result suggests that, despite a modest decrease in median relative humidity, heat stress measured by metrics considering both humidity and temperature in a warming climate will increase faster than that measured by temperatures alone would indicate. For a fixed Tmax , the high quantiles of RH (and thus of HI and dew point) increase from 1990–2005 to 2071–2080 in all four cities. This result suggests that the heat stress of a day at a given Tmax will increase in a warming climate due to the increase of RH.

Yuan, Jiacan↗
DOE OSTI2024

Enhancing carbon dioxide capture under humid conditions by optimizing the pore surface structure

Metal–organic frameworks (MOFs) exhibit significant potential for mitigating carbon emissions due to their high porosity and tunability. Despite numerous reports on CO 2 capture by MOF sorbents, a common challenge is their poor selectivity for CO 2 over water. Moreover, in-depth studies are much needed to elucidate the relationships among the pore surface structure, hydrophobicity, and CO 2 uptake capacity/selectivity. In this work, we investigate the factors influencing CO 2 adsorption capacity and selectivity under humidity in a series of isoreticular pillar-layer structures, Ni 2 (L) 2 (dabco) (L = bdc, ndc, adc). Our study shows that increasing ligand conjugation not only results in increased hydrophobicity, decreased pore size and BET surface area, but also leads to the change of primary binding sites of water molecules and higher binding energy of CO 2 , all of which contribute to largely increased CO 2 uptake capacity under humid conditions. Additionally, increasing ligand conjugation and consequently hydrophobicity slow down and reduce competitive water adsorption drastically. Notably, the MOF made of ligand with the highest conjugation, Ni 2 (adc) 2 (dabco), exhibits significantly enhanced CO 2 adsorption in N 2 /CO 2 binary mixtures under relatively high humidity (50% RH), with an increase of ~31% and ~36% for the composition of 15/85 and 50/50, respectively, compared to dry conditions. An experimental FTIR study and DFT theoretical calculations confirm that H 2 O occupies different primary binding site in Ni 2 (bdc) 2 (dabco) and Ni 2 (adc) 2 (dabco), and under humid conditions a higher binding energy of CO 2 is achieved with preferential H 2 O/CO 2 co-adsorption in Ni 2 (adc) 2 (dabco), potentially creating additional adsorption sites for CO 2 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Solid organic-coated ammonium sulfate particles at high relative humidity in the summertime Arctic atmosphere

The ability of atmospheric aerosols to impact climate through water uptake and cloud formation is fundamentally determined by the size, composition, and phase (liquid, semisolid, or solid) of individual particles. Particle phase is dependent on atmospheric conditions (relative humidity and temperature) and chemical composition and, importantly, solid particles can inhibit the uptake of water and other trace gases, even under humid conditions. Particles composed primarily of ammonium sulfate are presumed to be liquid at the relative humidities (67 to 98%) and temperatures (–2 to 4 °C) of the summertime Arctic. Under these atmospheric conditions, we report the observation of solid organic-coated ammonium sulfate particles representing 30% of particles, by number, in a key size range (<0.2 µm) for cloud activation within marine air masses from the Arctic Ocean at Utqiagvik, AK. The composition and size of the observed particles are consistent with recent Arctic modeling and observational results showing new particle formation and growth from dimethylsulfide oxidation to form sulfuric acid, reaction with ammonia, and condensation of marine biogenic sulfate and highly oxygenated organic molecules. Aqueous sulfate particles typically undergo efflorescence and solidify at relative humidities of less than 34%. Therefore, the observed solid phase is hypothesized to occur from contact efflorescence during collision of a newly formed Aitken mode sulfate particle with an organic-coated ammonium sulfate particle. With declining sea ice in the warming Arctic, this particle source is expected to increase with increasing open water and marine biogenic emissions.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Theoretical Analysis of the Entrainment–Mixing Process at Cloud Boundaries. Part I: Droplet Size Distributions and Humidity within the Interface Zone

Abstract The problem of a complex entrainment–mixing process is analyzed by solving a diffusion–evaporation equation for an open region in the vicinity of the cloud–dry air interface. Upon normalization the problem is reduced to a one-parametric one, the governing parameter being the potential evaporation parameter R proportional to the ratio of saturation deficit in the dry air to the available liquid water content in the cloud air. As distinct from previous multiple studies analyzing mixing within closed adiabatic volumes, we consider a principally nonstationary problem that never leads to a homogeneous equilibrium state. It is shown that at R < −1 the cloud edge shifts toward the cloud; that is, the cloud dissipates due to mixing with dry air, and the cloud volume decreases. If R > −1, the cloud edge shifts outside; that is, the mixing leads to an increase in the cloud volume. The time evolution of droplet size distribution and its moments, as well as the relative humidity within the expanding cloud–dry air interface, are calculated and analyzed. It is shown that the values of the mean volume radii rapidly decrease within the interface zone in the direction away from the cloud, indicating significant changes in the cloud edge microstructure. Scattering diagrams plotted for the cloud edge agree well with high-frequency in situ measurements, corroborating the reliability of the proposed approach. It is shown that the humidity front moves toward dry air faster than the front of liquid water content. As a result, the mixing leads to formation of a humid air shell around the cloud. The widths of the interface zone and humid shell are evaluated.

Pinsky, Mark↗