Water Vapor Density Research Articles

Estimation of Surface Water Vapour Density and its Variation with other Meteorological Parameters over Akure, Nigeria

In this paper, the monthly variation of Surface Water Vapour Density (SWVD) with meteorological parameters of monthly average daily mean temperature, relative humidity, surface pressure, cloud cover and sunshine hours during the period of thirty-eight (38) years (1979 - 2016) for Akure (Latitude 7.280N, Longitude 5.300E, 375m above sea level) were investigated. The daily variation of surface water vapour density for the two distinct seasons considering two typical months in each during the period of year 2014 was examined. The results showed fluctuation in the amount of surface water vapour density in each day of the month for the period under investigation. The monthly average daily values indicated that the surface water vapour densities are greater during the rainy season than in the dry season. It was observed that the maximum average value of surface water vapour density of 20.1019 gm-3 occurred in the month of September during the rainy season and minimum value of 15.5110 gm-3 in the month of January during the dry season. The highest value of surface water vapour density was observed on the 4th of June, 2014 with 26.3320 gm-3 and the lowest on the 31st day of December, 2014 with 6.0276 gm-3. The comparison assessment of the developed two variable SWVD based models was carried out using statistical indices of coefficient of determination (R2), Mean Bias Error (MBE), Root Mean Square Error (RMSE), Mean Percentage Error (MPE), Nash – Sutcliffe Equation (NSE) and Index of Agreement (IA). The developed multivariate correlation regression model that relates pressure and precipitable water vapour with R2 = 100%, MBE = -0.0177, RMSE = 0.0179, MPE = 0.1034, NSE = 99.9956% and IA = 99.9989% was found more suitable for surface water vapour density estimation with good fitting and therefore can be used for estimating surface water vapour density in Akure.

Investigation of cellulose filaments as filler in rigid insulating polyurethane foam

Cellulose is a biopolymer that has broad potential applications including in building insulation, and it was studied for its potential as a filler material. A closed-cell polyurethane foam insulation formulation was developed, and cellulose filaments (CFs) were introduced at varying percentages. The viscosity and morphology of the formulations were studied, as were different foam properties, such as water vapor permeability, reaction kinetics, density, porosity, thermal conductivity, and compressive strength foams as a function of cellulose filaments content. A commercial foam was also tested as a reference. The cellulose filaments impacted the formulations’ viscosity, and all the properties of the resulting insulating material. For example, samples containing 5% of cellulose filaments were found to perform differently than samples containing 0%, 1% and 2.5% mainly due to agglomerate formation, which impacted cell size (about 0.1 mm2 at 0%, 1% and 2.5% versus a mean of over 0.4 mm2 at 5%), and differential vapor sorption (with a mass change of 2%wt at 0 parts per hundred of polyol versus 2.5%wt at 5% from 0% to 95% relative humidity). However, the required performances by the standards of polyurethane foam insulation material were always fulfilled regardless of the amount of cellulose filaments present.

Case study on a novel approach to determining initial values for 3D water vapor tomography in the a priori water vapor field

Insufficient prior information in GNSS water vapor tomographic models can lead to instability in the structure of the design matrix. The addition of high-precision initial values for water vapor density can effectively solve this problem, but common methods for obtaining water vapor density are relatively crude and not fully utilizing the original accuracy of the a priori water vapor field. To address this issue, a new method is proposed that takes into account the influence of the a priori information weight ratio in the tomographic model on tomographic analysis results, based on the negative exponential decrease of atmospheric water vapor density in the vertical direction with height. Moreover, the 3D water vapor tomographic technique based on the ray-tracing fast voxel traversal algorithm has been improved and implemented in the C++ programming language. To verify the feasibility, accuracy, and stability of the improved 3D water vapor tomographic technique and the proposed method, the experiment using actual data from the CORS station in Hong Kong in January and May and the corresponding grid data provided by ERA5 was conducted. As benchmarks, radio-sounding data from the experimental area was utilized. In May, the proposed method exhibited an average daily improvement in the root mean square error of 0.88% (UTC0) and 0.97% (UTC12), and an improvement in the interquartile range of the difference between the water vapor density values at each altitude layer (excluding the top and bottom layers) and the corresponding sounding data of 5.08% (UTC0) and 3.37% (UTC12). In January, the average daily improvement in the root mean square error was −13.78% (UTC0) and −4.84% (UTC12), and the improvement in the interquartile range of the difference between the water vapor density values at each altitude level and those calculated from the corresponding sounding data was −14.49% (UTC0) and −6.31% (UTC12). The results show that the proposed method and the commonly used method maintain high consistency in the accuracy of the water vapor density values solved by the system of tomographic equations and improve stability, especially in May when the water vapor density near the surface is high. The feasibility of the improved 3D water vapor tomographic technique based on the ray-tracing fast voxel traversal algorithm is also demonstrated.

An improved GNSS remote sensing technique for 3D distribution of tropospheric water vapor

AbstractWater vapor plays an extremely important role in the monitoring and prediction of weather, and GNSS tomography can obtain 3D spatiotemporal change information and reliable water vapor profiles. In this paper, an improved global navigation satellite system (GNSS) tropospheric tomography technique using an ERA5 (the fifth generation ECMWF reanalysis) product is developed. First, the ERA5 product was adopted to analyze the spatiotemporal distribution of water vapor, and a water vapor density threshold defining the top of the tomography was determined; then, the height of the grid top (GT) of different seasons was obtained through linear fitting; finally, the water vapor value between GT and tropopause is constrained using the data of the ERA5 product as the initial value. The new method for using the ERA5 product to determine the height of the GT of the tomographic grid reduces the height of the top layer of the grid and increases the number of effective GNSS rays. Data from nine CORS stations in Hong Kong in 2019 were selected for experiments. The results showed that the new algorithm increased the number of effective satellite signals by 14%. In addition, the ERA5 data, the radiosonde data, and the COSMIC‐2 data were used as reference values. The accuracy of the water vapor density obtained by the algorithm was improved by 25%, 17% and 9%, respectively.

Retrieval of atmospheric temperature and humidity profiles over a tropical coastal station from ground-based Microwave Radiometer using deep learning technique

Ground-based multi-frequency microwave radiometer Profiler (Microwave Radiometer Profiler-MRP) provides valuable information on the altitude distribution of atmospheric humidity and temperature in the troposphere (upto ∼10 km) with high temporal resolution (of ∼1 min) under all-weather condition. These information are vital inputs for characterization of the atmospheric boundary layer, convective cloud systems, local weather modification and for studying the atmospheric dynamics. Potential of such radiometers are well established over the mid-latitude region. Thiruvananthapuram, located in the Indian peninsular region, is one of the first stations in the equatorial region where such an instrument made continuously operational for seven years since 2010 at the tropical coastal station. The instrument measures the brightness temperatures (Tb in Kelvin) at Ka- and V-band frequencies with a temporal resolution of ∼1 min. A trained back-propagation neural network technique based on the radiosonde ascends data for more than one decade obtained by India Meteorological station at Thiruvananthapuram, was used to derive the atmospheric humidity and temperature profiles. This paper presents the implementation of another retrieval technique based on deep learning approach - batch normalization and neural network (BNN) to retrieve temperature and water vapour density (WVD) profiles from Tb values during clear sky conditions and validation of the retrieval accuracies. This inversion model, much faster in computation, consists of two hidden layers and the rectified linear unit (ReLU) is used as the activation function as it can overcome the problems of saturation and vanishing gradients. The Tbs observed by radiometer are corrected by reducing the bias between the simulated Tb, using forward radiative transfer model, and the observed Tb. The validation of retrieved profiles with the radiosonde demonstrates a good retrieval capability, showing a root-mean-square error of 1.8K for temperature, <2 g/m3 for WVD and ∼14% for RH.

HCOO− aq degradation in droplets by OHaq in an atmospheric pressure glow discharge

Plasmas in contact with liquids can degrade organic molecules in a solution, as reactive oxygen and nitrogen species produced in the plasma solvate into the liquid. Immersing small droplets (tens of microns in diameter) in the plasma can more rapidly activate the liquid compared to treating a large volume of liquid with a smaller surface-to-volume ratio. The interactions between a radio frequency glow discharge sustained in He/H2O and a water droplet containing formate (HCOO− aq) immersed in and flowing through the plasma were modeled using a zero-dimensional global plasma chemistry model to investigate these activation processes. HCOO − aq interacts with OHaq, which is produced from the solvation of OH from the gas phase. The resulting HCOO − aq concentrations were benchmarked with previously reported experimental measurements. The diameter of the droplet, initial HCOO − aq concentration, and gas flow rate affect only the HCOO − aq concentration and OHaq density, leaving the OH density in the gas phase unaffected. Power deposition and gas mixture (e.g. percentage of H2O) change both the gas and liquid phase chemistry. A general trend was observed: during the first portion of droplet exposure to the plasma, OHaq primarily consumes HCOO − aq. However, O2 − aq, a byproduct of HCOO − aq consumption, consumes OHaq once O2 − aq reaches a critically large density. Using HCOO − aq as a surrogate for OHaq-sensitive contaminants, combinations of residence time, droplet diameter, water vapor density, and power will determine the optimum remediation strategy.

Plasma‐enhanced evaporation and its impact on plasma properties and gaseous chemistry in a pin‐to‐water pulsed discharge

AbstractThe plasma in contact with liquids has led to various novel applications such as plasma biomedicine, material synthesis, and so on. However, the phenomenon of evaporation under plasma treatment and its impact on plasma–liquid interactions has a limited understanding. In this study, the spatially and temporally resolved behavior of water vapor production and its induced influences on plasma properties and gaseous chemistry were studied in detail in an atmospheric pressure pin‐to‐water pulsed He discharge. Diagnostic methods such as laser‐induced fluorescence (LIF) and high‐resolution optical emission spectroscopy (OES) were applied to determine the water vapor and OH radical densities, as well as key plasma parameters such as the gas temperature and electron density. It shows that the physicochemical properties of plasma vary among different discharge regions due to evaporation behavior stimulated during the pulsed discharge‐on phase. In addition, using simulation based on the experimental data, the mechanisms of how water vapor affects the observed spatiotemporal behaviors of OH radicals in different discharge regions are understood. Compared to the pin‐anode and liquid‐cathode sheath regions, proper electron parameters such as density and temperature, as well as water vapor density in the plasma‐positive column, significantly enhance the production of reactive OH radical through the dominant path of electron‐stimulated H2O dissociation. However, higher levels of electron parameters in the intense discharge region near the positive‐pin boundary enhance OH dissociation and finally result in the hollow distribution of OH density. From the global kinetic plasma simulation, the production of reactive hydroxide species playing key roles in plasma medicine treatments, such as O, H, HO2, H2O2, and hydrated ions including H+(H2O)4 and H+(H2O)5, are promoted noticeably as a result of the enhanced water evaporation process.

A numerical model for hydrothermal transport in unsaturated freezing soils considering thermodynamics equilibrium

AbstractThe analysis of frost heave in unsaturated subgrade soils should consider the coupled movement of liquid water, vapor, and heat, accompanied by phase transition of water, vapor, and ice. In this paper, the equilibrium relationship of the three phases of water in soils was comprehensively considered, and the water head and vapor density were determined under frozen and unfrozen conditions from the perspective of thermodynamics. Based on that, the governing equations of mass and energy conservation were then derived and a new transient finite element model was developed, considering the behavior of the phase change and coupled hydrothermal transport under frozen as well as unfrozen conditions. Since the discontinuities between the frozen and the unfrozen zones may bring difficulties to the numerical solution, two kinds of smoothing techniques were proposed to solve the discontinuities at the phase transition interface, which guaranteed robust convergence and enhanced computational efficiency. The model proposed was verified by comparing with some available test results and applied to analyze the frost heave process of unsaturated subgrade under impermeable road pavements, demonstrating the model's accuracy and applicative prospect. It is revealed that the movement of liquid water and vapor in the frozen zones may still exist, and its mechanism and performance are different from that in unfrozen zones. The significance of vapor migration on the subgrade frost heave is also emphasized.

Tomographic Reconstruction of Water Vapor Density Fields From the Integration of GNSS Observations and Fengyun-4A Products

The potential of precipitable water vapor (PWV) maps retrieved by remote sensing satellites can address the geometry defect of global navigation satellite system (GNSS) observations in tropospheric tomography. The second-generation geostationary meteorological satellite Fengyun-4A (FY-4A) of China can provide PWV products with high spatial (4 km) and temporal (15 min) resolutions. This article presents the first study on water vapor tomography by integrating GNSS measurements and FY-4A products using the node-based parameterized method. Layer PWV (LPW) products of FY-4A instead of the total PWV are adopted, which can increase the rank of the tomographic equation significantly. The integrated tomography model is validated with observational data collected over the three-month period of June to August 2020 from 124 GNSS stations in Hunan province, China. Assessments using radiosonde and European Centre for Medium-Range Weather Forecasts ReAnalysis 5 (ERA5) data demonstrate the better performance of the integrated model against the traditional model using GNSS data alone. In the assessment with radiosonde profiles, the integrated model improves the tomographic solutions upon the traditional model by 40.58% and 36.33% for 30- and 15-min resolutions, respectively. Root mean square errors (RMSEs) of density differences between ERA5 and the integrated model vary from 1.24 to 2.82 g/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{m}^{3}$ </tex-math></inline-formula> throughout the study area. RMSEs vertically decrease from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 5$ </tex-math></inline-formula> g/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{m}^{3}$ </tex-math></inline-formula> at the bottom to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 0.5$ </tex-math></inline-formula> g/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{m}^{3}$ </tex-math></inline-formula> at the top layer of about 10 km. This work demonstrates the benefit of high-quality FY-4A products to GNSS tomography because they can effectively mitigate the ill-posed problem of inverse process.

Behavioural hydroregulation protects against acute effects of drought in a dry-skinned ectotherm.

During extreme climate events, behavioural thermoregulation may buffer ectotherms from thermal stress and overheating. However, heatwaves are also combined with dry spells and limited water availability, and how much individuals can behaviourally mitigate dehydration risks through microclimate selection remains largely unknown. Herein, we investigated the behavioural and physiological responses to changes in air and microhabitat humidity in a terrestrial ectotherm, the asp viper (Vipera aspis). We exposed individuals to a simulated heatwave together with water deprivation for 3weeks, and manipulated air water vapour density (wet air vs. dry air) and microclimate (wet shelter vs. dry shelter) in a two-by-two factorial design. Dry air conditions led to substantial physiological dehydration and muscle wasting. Vipers exposed to dry air usedmore often a shelter thatoffered a moist microclimate, which reduced dehydration and muscle wasting at the individual level. These results provide the first experimental evidence that active behavioural hydroregulation can mitigate specific physiological stress responses caused by a dry spell in an ectotherm. Future studies investigating organismal responses to climate change should consider moisture gradient in the habitat and integrate both hydroregulation and thermoregulation behaviours.

When Do Subpollen Particles Become Relevant for Ice Nucleation Processes in Clouds?

AbstractWhen exposed to sufficiently humid environments, pollen grains burst and release large quantities of small subpollen particles (SPPs) which carry ice nucleating macromolecules. In this study, for the first time we develop a physically based parameterization describing the bursting process of pollen by applying a turgor pressure parameterization and quantify the impact SPPs have on overall ice nucleation in clouds. SPPs are generated from simulated birch pollen emissions over Europe for a 10‐day case study in spring. We found SPP concentrations to surpass pollen grain concentrations by 4–6 orders of magnitude leading to an abundance of biological ice nuclei from SPPs in the range of 103−104 m−3. However, it is found that these concentrations lead to only small changes in hydrometeor number densities and precipitation. Addressing the question when SPPs become relevant for ice nucleation in clouds, we conducted a sensitivity investigation. We find that amplifying ice nucleation efficiency of biological particles by factors greater 100 increases the ice particle numbers by up to 25% (T ≈ 268 K). Strong reductions show in cloud droplet number concentration and water vapor at these temperatures while water vapor is increasing at 600 m. Overall, we found a net reduction of water in the atmosphere as liquid and particularly water vapor density is reduced, while frozen water mass density increases above 257 K. Findings indicate an alteration of mixed‐phase cloud composition and increased precipitation (up to 6.2%) when SPPs are considered as highly efficient biological ice nuclei.

New Models for Vertical Distribution and Variation of Tropospheric Water Vapor—A Case Study for China

For better modeling the vertical distribution and variations of water vapor, a 10-year time-series of a newly derived water vapor parameter (termed IRPWV), defined as the ratio of water vapor density (WVD) to the total precipitable water vapor (TPWV), was statistically analyzed. This research showed that the vertical distribution of IRPWV presents a periodic pattern and is highly correlated with the relative magnitude of its corresponding TPWV when compared with the other TPWVs in the same time range. Six TPWV ranges were first chosen to determine the relative magnitude and then used to classify the IRPWV vertical distributions of TPWV. For the periodic variations in each of the six classified IRPWV vertical distribution time-series, a temporal IRPWV model was developed accordingly with six sets of coefficients. The new models were validated by comparing their predictions against the reference values from sounding data at 12 radiosonde stations in China, and their performance was also evaluated against that of the commonly used exponential model. Results showed that, first, the proportions of the height range that had reduced annual root mean square error (RMSE) of WVD in all height ranges within all TPWV ranges were over 75% at the 12 stations. Then, the annual RMSEs of the WVD for all the stations were reduced by at least 11%, 20%, 43%, 48%, 40%, 38%, 32%, 35%, 32%, and 28% in each of the 10 selected height ranges, respectively.

Tropospheric water vapor: a comprehensive high-resolution data collection for the transnational Upper Rhine Graben region

Abstract. Tropospheric water vapor is one of the most important trace gases of the Earth's climate system, and its temporal and spatial distribution is critical for the genesis of clouds and precipitation. Due to the pronounced dynamics of the atmosphere and the nonlinear relation of air temperature and saturated vapor pressure, it is highly variable, which hampers the development of high-resolution and three-dimensional maps of regional extent. With their complementary high temporal and spatial resolutions, Global Navigation Satellite Systems (GNSS) meteorology and Interferometric Synthetic Aperture Radar (InSAR) satellite remote sensing represent a significant alternative to generally sparsely distributed radio sounding observations. In addition, data fusion with collocation and tomographical methods enables the construction of detailed maps in either two or three dimensions. Finally, by assimilation of these observation-derived datasets with dynamical regional atmospheric models, tropospheric water vapor fields can be determined with high spatial and continuous temporal resolution. In the following, a collection of basic and processed datasets, obtained with the above-listed methods, is presented that describes the state and course of atmospheric water vapor for the extent of the GNSS Upper Rhine Graben Network (GURN) region. The dataset contains hourly 2D fields of integrated water vapor (IWV) and 3D fields of water vapor density (WVD) for four multi-week, variable season periods between April 2016 and October 2018 at a spatial resolution of (2.1 km)2. Zenith total delay (ZTD) from GNSS and collocation and refractivities are provided as intermediate products. InSAR (Sentinel-1A/B)-derived double differential slant total delay phases (ddSTDPs) and GNSS-based ZTDs are available for March 2015 to July 2019. The validation of data assimilation with five independent GNSS stations for IWV shows improving Kling–Gupta efficiency (KGE) scores for all seasons, most notably for summer, with collocation data assimilation (KGE = 0.92) versus the open-cycle simulation (KGE = 0.69). The full dataset can be obtained from https://doi.org/10.1594/PANGAEA.936447 (Fersch et al., 2021).

Estimation of Water Vapor Density in Adiabatic Mixing of Cryogenic Gas and Moist Air

Concentration distribution is essential for the emergency disposal of cryogenic fuel leakage. In the dispersion process of cryogenic gas, its concentration is greatly influenced by the atmospheric water vapor. The authors have presented an adiabatic mixing model to derive the concentration of the cryogenic gas, in which the value of water vapor density is obtained by referring to the NIST database continuously. However, it is difficult to achieve fast system response times for real-time monitoring systems when calling NIST. Thus, a simple algebraic model of water vapor density with high calculation efficiency is necessary. Based on the detection of temperature and the solution of water vapor partial pressure, a calculation model was developed. For a given initial ambient temperature and relative humidity, the dew point could be solved by Qian’s correlation. By temperature comparisons of the mixture cloud, dew point, and triple point, the water vapor partial pressure can be calculated by the Goff–Gratch formulation. Then, the water vapor density during the temperature declining process can be derived via EOS. The results show that the model has high estimation accuracy, and has a close mean deviationof 0.08%to the IAPWS 95 of 0.03%. The increase in the computation efficiency was confirmed as +67% under nine testing points. The model facilitates the engineering utilization of the adiabatic mixing model for cryogenic fuel leakage monitoring.

Development of a New Vertical Water Vapor Model for GNSS Water Vapor Tomography

One of the main challenges of Global Navigation Satellite System (GNSS) tomography is in solving ill-conditioned system equations. Vertical constraint models are typically used in the solution procedure and play an important role in the quality of the GNSS tomography, in addition to helping resolve ill-posed problems in system equations. In this study, based on a water vapor (WV) parameter, namely IRPWV, a new vertical constraint model with six sets of coefficients for six different WV states was developed and tested throughout 2019 in the Hong Kong region with four tomographic schemes, which were carried out with the model and the traditional vertical constraint model using three different types of water vapor scale height parameters. Experimental results were numerically compared against their corresponding radiosonde-derived WV values. Compared with the tests that used the traditional model, our results showed that, first, for the daily relative error of WV density (WVD) less than 30%, the new model can lead to at least 10% and 49% improvement on average at the lower layers (below 3 km, except for the ground surface) and the upper layers (about 5–10 km), respectively. Second, the skill score of the monthly root-mean-square error (RMSE) of layered WVD above 10 accounted for about 83%, 87%, and 64%. Third, for the annual biases of layered WVD, the new model significantly decreased by 1.1–1.5 g/m3 at layers 2–3 (about 1 km), where all schemes showed the maximal bias value. Finally, for the annual RMSE of layered WVD, the new model at the lower (about 0.6–3 km) and upper layers improved by 13–42% and 5–47%, respectively. Overall, the new model performed better on GNSS tomography and significantly improved the accuracy of GNSS tomographic results, compared to the traditional model.

Evaluation of the New York State Mesonet Profiler Network data

Abstract. The New York State Mesonet (NYSM) Profiler Network consists of 17 stations statewide. Each station operates a ground-based Doppler lidar (DL), a microwave radiometer (MWR), and an environmental Sky Imaging Radiometer (eSIR) that collectively provide profiles of wind speed and direction, aerosol, temperature, and humidity along with solar radiance, optical depth parameters, and fisheye sky images. This study presents a multi-year, multi-station evaluation of Profiler Network data to determine the robustness and accuracies of the instruments deployed with respect to well-defined measurements. The wind speed (WS) measured by the DL and temperature (T) and water vapor density (WVD) measured by the MWR at three NYSM Profiler Network sites are compared to nearby National Weather Service radiosonde (RS) data, while the aerosol optical depth (AOD) measured by the eSIR at two Profiler Network sites are compared to nearby in situ measurements from the Aerosol Robotic Network (AERONET). The overall comparison results show agreement between the DL or MWR and RS data with a correlation of R2≥0.89 and a correlation between AERONET and eSIR AOD data of R2 ≥ 0.78. The WS biases are statistically insignificant and equal to 0 (p &gt; 0.05) within 3 km, whereas T and WVD biases are statistically significant and are below 5.5 ∘C and 1.0 g m−3, within 10 km. The AOD biases are also found to be statistically significant and are within 0.02. The performance of the DL, MWR, and eSIR are consistent across sites with similar error statistics. When compared during three different weather conditions, the MWR is found to have varying performance, with T errors higher during clear-sky days, while WVD errors are higher during cloudy and precipitation days. To correct such observed biases, a linear regression method was developed and applied to the MWR data. In addition, wind shear from the DL and 14 common thermodynamic parameters derived from the MWR show an agreement with RS values where correlation is mostly R2 ≥ 0.70 and biases are mostly statistically insignificant. A case study is presented to demonstrate the applicability of DL and MWR for nowcasting a severe weather event. Overall, this study demonstrates the robustness and value of the Profiler Network for real-time weather operations.

A new method for tropospheric tomography using GNSS and Fengyun-4A data

Global Navigation Satellite Systems (GNSS) tropospheric tomography can reflect a three-dimensional distribution of water vapour. However, the common ill-posed problem for GNSS tropospheric tomography needs to be addressed. The relatively newly launched Chinese Fengyun-4A (FY-4A) satellite water vapour data have a high spatiotemporal resolution and may be used to assist in resolving the ill-posed problem. In this study, a new tropospheric tomographic method using both GNSS and FY-4A data was proposed. Tomographic schemes for the new method with the coverage rate of GNSS sites (CRGS, which is defined as the ratio of the number of GNSS sites to the number of horizontal grids in the tropospheric tomography) of 0.2, 0.28, 0.36 and 0.44 were compared with traditional tomographic schemes using the same CRGS. Test results showed that adding FY-4A data, in addition to GNSS data, to the tomographic system could effectively increase the number of voxels crossed by signals, which benefits the ill-posed problem. When CRGS equated 0.28, the new method had the largest improvement compared with the traditional method, in which the mean of the root mean squared error (RMSE) of the water vapour density (WVD) was reduced from 2.44 and 1.38 g/m3 to 2.05 and 1.22 g/m3 using radiosonde and ERA5 data as the references, respectively. Statistical results showed that the new method that used both GNSS and FY-4A data outperformed the traditional method that only used GNSS data.

Characteristics of two different types of thunderstorms in summer over the Nagqu area in China

To investigate further the characteristics of thunderstorms on the Qinghai–Tibet plateau, a plateau vortex (PV) thunderstorm and a local thermoconvective (TC) thunderstorm over the Nagqu area are analyzed using cloud-radar, microwave-radiometer, and raindrop-spectrometer data, and their macrophysical and microphysical evolution characteristics are discussed in terms of thermodynamic processes, microphysical processes, and lightning activities. The results show the following. 1) The cloud layer was deeper in the PV thunderstorm, but the TC thunderstorm had a stronger short-time updraft with a radial velocity exceeding 10 m/s, and the warming from the strong updraft action and latent heat release from the hydromorphic phase change was about twice that of the PV thunderstorm. 2) The water vapor density increased significantly when the thunderstorm cloud passed, and the liquid water content in the middle and lower layers exceeded 4 g/m3. The maximum ice water content in the TC thunderstorm was twice bigger than that in the PV thunderstorm. The trends of raindrop number concentration and rain intensity of the PV thunderstorm were similar, and the average particle size of raindrops was smaller than that of the TC thunderstorm. 3) Both types of thunderstorms accounted for more than 90% of negative cloud-to-ground (CG) lightning, and the regions with black-body temperature (TBB) less than −40 °C and a larger TBB gradient were more favorable for the occurrence of CG lightning. 4) Thermodynamic fields bring water vapor and lift for microphysical processes, and microphysical changes release latent heat to enhance the dynamic effects, which together promote the development of lightning activities. The peak radial velocity and ice-phase particle concentration were more than 10 min ahead of the active peak of the CG lightning. This study reveals the macrophysical and microphysical evolution characteristics of different types of thunderstorms and provides a certain scientific basis for disaster prevention and mitigation regarding thunderstorms over the Nagqu area.

Assessment of the Water Vapor Tomography Based on Four Navigation Satellite Systems and Their Various Combinations

With the gradual improvement of Galileo and the opening of BDS-3 services, water vapor tomography based on multi-GNSS can be effectively carried out to reconstruct three-dimensional water vapor distribution. In this paper, experiments in Hong Kong were conducted to analyze and assess the performances of GPS, BDS, GLONASS, and Galileo and their combinations in water vapor tomography. Numerical results show that the number of available signal rays varies widely in the four satellite systems, and the value can be increased by the combination of satellite systems; the combinations also increase the number of voxels crossed by signal rays, but this value is not directly related to the number of available signal rays; the number and distribution of the voxels with sufficient signal rays, which most closely related to the structure of the tomographic model, show no obvious differences in the four satellite systems and their combinations. Comparative results of slant water vapor (SWV) estimated by GNSS data and water vapor density derived from radiosonde data reveal that the differences in the water vapor tomography of the four satellite systems are small, and their combinations have limited improvement in the tomographic results.

LB962 Barrier integrity test for in vitro permeation testing of topical and transdermal products

In vitro skin permeation testing (IVPT) is often used to ensure sufficient efficacy of dermaceuticals. IVPT studies utilize viable tissue membrane to represent in vivo conditions. The intact barrier of such tissue membrane provides biological relevance, in vitro. Transepidermal water loss (TEWL) measures changes in water vapor density on the skin surface. The purpose of this study was to evaluate TEWL as an appropriate barrier integrity test, in vitro, and determine an acceptable range using a Delfin® Vapometer.