Vapor Content Research Articles

Generation and delivery of free hydroxyl radicals using a remote plasma

We demonstrate a new gas-based generation source using a low power radio frequency driven atmospheric pressure plasma configured to deliver the radical flux into the far effluent region, well away from interference from other plasma factors such as electric fields, currents, and ultraviolet radiation. Using He–H2O gas chemistry isolated from the laboratory air, the plasma generated flux contains and other radicals including, O and HO2 as well as H2O2 which, along with, was found to vary with H2O vapour content and absorbed power density. Peak flux values were 2.3 nmol s−1 and 0.23 nmol s1 for H2O2 and respectively at a distance of 50 mm from the plasma, with 790 ppmv H2O and a power density of ∼108 W m−3. The maximum flux density was 4.5 × 1019 m−2s−1 falling to 1.7 × 1019 m2 s1 at 110 mm, equivalent to generation rates of 74 µM s1 and 28 µM s−1. Despite high recombination rates at the plasma exit, the escaping flux is still significant, indicating a viable delivery capability to downstream targets. Its performance with regard to generation rates compares well with traditional generation techniques such as radiolysis, advanced oxidation processes and enhanced Fenton-chemistry approaches where production rates are sub-µM s−1. Delivering precisely quantifiable fluxes provides new opportunities for scientific studies and technological opportunities in cell biology, atmospheric chemistry, protein unfolding and systematic dose studies for plasma-based and other related potential medical treatments.

Discrete-Pulsed Energy Input Based Method for Neutralisation of the Acidic Condensate

The article's authors analysed the most perspective and widely known methods of neutralising the acidic condensate, which is a by-product of natural gas combustion. Among them, the hydrodynamic cavitation method was the most effective. In this regard, it was proposed to improve this method by using the method of discrete-pulsed energy input, which involves neutralisation due to the degassing process. Based on the mathematical model of the bubble ensemble dynamics, a numerical simulation of the formation and growth of vapour-gas bubbles in the process of cavitation boiling of condensate was carried out. Also, an analytical study of the evolution of the vapour-gas bubble population and changes in the current vapour content of the condensate during its boiling was investigated under different values of the initial size of gas micronuclei. The results of the experimental study also confirmed the effectiveness of this method and showed that almost complete removal of carbonic acid from condensate occurs during the first two minutes of processing. That is evidenced by the increased pH values of condensate, which corresponds to the range of permissible pH values of distilled water. Therefore, the carbonic acid in the condensate is absent. Using this method will significantly reduce the environmental effect and the amount of harmful emissions.

Effect of water vapor on the reduction kinetics of hematite powder by hydrogen-water vapor in different stages

The powder of the hematite sample was isothermally reduced with a hydrogen-water vapor gas mixture at 1023K-1273K. The results indicate that the overall reduction process of hematite can be divided into three stages (Fe2O3-Fe3O4-FeO-Fe) each of which should be investigated. At 1023K, the average reaction rate decreased by 53.6% in stage 1 when the water vapor content of the reaction gas increased from 0% to 50%, and it decreased by about 77.2% in stage 2. However, in stage 3, when the water vapor content increased only from 0% to 20%, it decreased by about 78.1%. The results also show that the influence of water vapor on the reduction reaction increases with increasing reaction temperature in all stages of the reduction reaction. The microstructure of the reduction products showed that they still had some holes; that did not seriously block the channel for hydrogen diffusion. Various models were considered to further clarify the influence of water vapor in the reduction stage The range of apparent activation energy of the different stages obtained by the model fitting was about 20-70 kJ/mol, which also confirmed the absence of the solid-state diffusion phenomenon.

Impact of High Concentrations of Saharan Dust Aerosols on Infrared-Based Land Surface Temperature Products

An analysis of three operational satellite-based thermal-infrared land surface temperature (LST) products is presented for conditions of heavy dust aerosol loading. The LST products are compared against ERA5's skin temperature (SKT) across the Sahara Desert and Sahel region, where high concentrations of dust aerosols are prevalent. Large anomalous differences are found between satellite LST and ERA5's SKT during the periods of highest dust activity, and satellite–ERA5 differences are shown to be strongly related to dust aerosol optical depth at 550 nm (DuAOD), indicating an underestimation of LST in conditions of heavy dust aerosol loading. In situ measurements from two ground stations in the Sahel region provide additional evidence of this underestimation, showing increased biases of satellite LST with DuAOD, and no significant dependence of ERA5's SKT biases on dust aerosol concentrations. The impact of atmospheric water vapor content on LST and SKT is also examined, but dust aerosols are shown to be the primary driver of the inaccurate LSTs observed. Based on comparisons with in situ data, we estimate an aerosol-induced underestimation of LST of approximately 0.9 K for every 0.1 increase in DuAOD. Analysis of brightness temperatures (BTs) in the thermal infrared atmospheric window reveals that dust aerosols have the opposite effect on BT differences compared to water vapor, leading to an underestimation of atmospheric correction by the LST retrieval algorithms. This study highlights a shortcoming of current operational LST retrieval algorithms that must be addressed.

Particularities of flue gases from energy installations on the process of continuous flow capture for CO2 by direct methanation

The efficiency of the direct methanation of the flue gases from the energy installations is influenced both by the relatively low participation of the CO2 component and by the presence of water vapor and oxygen from the excess air. The water vapor content reduces the efficiency of the methanation process by a small percentage. The excess air has been analysed in the paper in more detail to determine whether it can lead to the process of self-ignition (explosion) of hydrogen in the phase of its admission to the methanizer. Thus, an analytical calculation was performed for the composition of the flue gases from an energy installation that uses liquid fuel, the excess air being 1.3. At the end of the paper, the objectives of the experimental tests to be performed were presented, and details regarding the complex experimental installation and the already achieved methanizer were provided.

Removal of H2S from simulated blast furnace gas by adsorption over metal-modified 13X zeolite

With the promulgation of new regulations, it’s of great significance to desulfurization from blast furnace gas (BFG) to meet the clean production of iron making industry. Among different desulfurization technologies, zeolite-based sorbents are extensively studied due to the easy operation, low operating cost, and long service life. In this research, the 13X zeolite was selected, and it was ion-exchanged by different metal elements (Cu, Zn, Co, Mn) to prepared a series of sorbents. A fixed bed was used to evaluate their desulfurization behavior, and the XRD, SEM, ICP-OES, XPS, N2 adsorption, and CO2-TPD were carried out to characterize the physical and chemical properties of sorbents. The effects of water vapor content and desulfurization temperature on the removal of H2S were investigated. The regeneration performance of sorbent was also explored. The results showed that the Cu25X-Ex sorbent has the highest breakthrough sulfur capacity of 7.71 g S/100 g sorbent in dry simulated BFG. The breakthrough sulfur capacity of Cu25X-Ex was 4.52 g S/100 g sorbent when the water vapor content is 5 %. The CO2-TPD results showed that the basic sites were favorable for the adsorption of H2S on the surface of zeolite. The XPS results illustrate that the forms of S adsorbed on Cu25X-Ex sorbent were CuS, CuS2O3, and CuSO4, so it is suggested that the reaction between adsorbed H2S with the metal cations in sorbent occurred subsequently. The research indicated that Cu25X-Ex sorbent has potential applicability in the desulfurization of blast furnace gas.

An Improved Strategy for Real-Time Troposphere Estimation and Its Application in the Severe Weather Event Monitoring

The water vapor content in the atmosphere is highly correlated with rainfall events, which can be used as a data source for rainfall prediction or drought monitoring. The GNSS PPP (Precise Point Positioning) technique can be used to estimate the troposphere ZWD (Zenith Wet Delay) parameter which can be converted into precipitable water vapor (PWV). In this study, we first investigate the impacts of the weighting strategies, observation noise settings, and gradient estimation on the accuracy of ZWD and positions. A refined strategy is proposed for the troposphere estimation with uncombined raw PPP model, down-weighting of Galileo/GLONASS/BDS code observation by a factor of 3, using a sine2-type elevation-dependent weighting function and estimating the horizontal gradients. Based on the strategy, the correlation of the estimated tropospheric parameters with the rainfall is analyzed based on the data from the “7.20” rainstorm in Henan Province, China. The PWV is first calculated based on the hourly global pressure and temperature (HGPT) model and compared with the results from ERA5 products. Results show their good consistency during the rainfall period or the normal period with a standard deviation of 3 mm. Then, the high correlation between the PWV and the heavy rain rainfall event is validated. Results show that the accumulated PWV maintains a high level before the rainstorm if a sustainable water supply is available, while it decreased rapidly after the rainfall. In comparison, the horizontal gradients and the satellite residuals are less correlated with the water vapor content. However, the gradients can be used to indicate the horizontal asymmetry of the water vapor in the atmosphere.

Development of Solutions for Increasing the Combustion Efficiency of Hydrogen in Water Vapor in a Hydrogen-Oxygen Steam Superheater

The study is aimed at revealing the specific features of the burning of hydrogen with oxygen in a water-vapor atmosphere. The purpose of the study is to define the optimal values for diluting the burning mixture with water vapor in the active burnout zone, providing the minimal values of incomplete combustion. Modeling of burning processes was carried out with the use of kinetic mechanisms in the Ansys Chemkin-Pro software. The result of the study was the definition of critical water vapor content in a burning mixture as 60% fraction of total mass with, obtaining dependencies of key parameters of the burning process within a wide range. The mechanism of chemical kinetics was selected for further modeling in a three-dimensional setting, and tasks for the formulation of requirements and methods for the design of efficient hydrogen combustion chambers were set up for 500 MW gas turbine plants at a supercritical pressure of 20 MPa or higher.

Precipitable Water Vapor Retrieval Based on DPC Onboard GaoFen-5 (02) Satellite

GaoFen-5 (02) (GF5-02) is a new Chinese operational satellite that was launched on 7 September 2021. The Directional Polarimetric Camera (DPC) is one of the main payloads and is mainly used for the remote sensing monitoring of atmospheric components such as aerosols and water vapor. At present, the DPC is in the stage of on-orbit testing, and no public DPC precipitable water vapor (PWV) data are available. In this study, a PWV retrieval algorithm based on the spectral characteristics of DPC data is developed. The algorithm consists of three parts: (1) the construction of the lookup table, (2) the calculation of water vapor absorption transmittance (WVAT) in the band at 910 nm, and (3) DPC PWV retrieval. The global PWV results derived from DPC data are spatially continuous, which can illustrate the global distribution of water vapor content well. The validation based on the Aerosol Robotic Network (AERONET) PWV data shows that the DPC PWV data have accuracy similar to that of Moderate-resolution Imaging Spectroradiometer (MODIS) PWV data, with coefficient correlation of determination (R2), mean absolute error (MAE), and relative error (RE) of 0.32, 0.30, and 0.93 using the DPC and 0.23, 0.36, and 0.96 using the MODIS, respectively. The results show that our proposed DPC PWV retrieval algorithm is feasible and has high accuracy. By analyzing the errors, we found that the calibration coefficients of the DPC in the 865 nm and 910 nm bands need to be updated.

Numerical analysis of moisture and gas transport in earthen final covers considering effects of vapor and temperature gradient

Biochemical decomposition of high kitchen wastes in landfills in China results in (i) a high content of vapor in landfill gas (LFG) and (ii) a noticeable temperature gradient across the earthen final cover (EFC). Yet, it is unclear how vapor and temperature gradients affect moisture and gas transport through EFC and microbial aerobic methane oxidation (MAMO). A theoretical model of moisture-gas-heat reactive transport considering MAMO and effects of vapor flow and temperature gradients was developed, and a series of parametric studies were included. The model was verified by published test results. The parametric simulation results show that vapor from landfill wastes can replenish water to EFCs in dry seasons, which results in (i) the relief of water shortage of vegetation and MAMO and (ii) LFG emission reduction. Effects of vapor inflow become more significant under larger temperature gradient. In cold seasons, temperature gradients can promote MAMO to reduce methane emissions, and enhance evaporation to reduce percolation. When evaporation rate at the surface exceeds 30 times vapor influx, vapor inflow has negligible effects on moisture and gas transport in EFCs. Neglecting effects of vapor and temperature gradient can lead to misjudgments on anti-seepage performance and methane emission reduction performance of EFCs.

Atmospheric Correction Inter-comparison eXercise, ACIX-II Land: An assessment of atmospheric correction processors for Landsat 8 and Sentinel-2 over land

The correction of the atmospheric effects on optical satellite images is essential for quantitative and multi-temporal remote sensing applications. In order to study the performance of the state-of-the-art methods in an integrated way, a voluntary and open-access benchmark Atmospheric Correction Inter-comparison eXercise (ACIX) was initiated in 2016 in the frame of Committee on Earth Observation Satellites (CEOS) Working Group on Calibration & Validation (WGCV). The first exercise was extended in a second edition wherein twelve atmospheric correction (AC) processors, a substantially larger testing dataset and additional validation metrics were involved. The sites for the inter-comparison analysis were defined by investigating the full catalogue of the Aerosol Robotic Network (AERONET) sites for coincident measurements with satellites' overpass. Although there were more than one hundred sites for Copernicus Sentinel-2 and Landsat 8 acquisitions, the analysis presented in this paper concerns only the common matchups amongst all processors, reducing the number to 79 and 62 sites respectively. Aerosol Optical Depth (AOD) and Water Vapour (WV) retrievals were consequently validated based on the available AERONET observations. The processors mostly succeeded in retrieving AOD for relatively light to medium aerosol loading (AOD < 0.2) with uncertainties <0.08, while the overall uncertainty values were typically 0.23 ± 0.15. Better performances were observed for WV retrievals with >90% of the results falling within the suggested empirical specifications and with the Root Mean Square Error (RMSE) being mostly <0.25 g/cm2. Regarding Surface Reflectance (SR) validation two main approaches were followed. For the first one, a simulated SR reference dataset was computed over all of the test sites by using the 6SV (Second Simulation of the Satellite Signal in the Solar Spectrum vector code) full radiative transfer modelling (RTM) and AERONET measurements for the required aerosol variables and water vapour content. The performance assessment demonstrated that the retrievals were not biased for most of the bands. The uncertainties ranged from approximately 0.003 to 0.01 (excluding B01) for the best performing processors in both sensors' analyses. For the second one, measurements from the radiometric calibration network RadCalNet over La Crau (France) and Gobabeb (Namibia) were involved in the validation. The performance of the processors was in general consistent across all bands for both sensors and with low standard deviations (<0.04) between on-site and estimated surface reflectance. Overall, our study provides a good insight of AC algorithms' performance to developers and users, pointing out similarities and differences for AOD, WV and SR retrievals. Such validation though still lacks of ground-based measurements of known uncertainty to better assess and characterize the uncertainties in SR retrievals.

Importance of Tropospheric Correction to C-band InSAR Measurements: Application in the 2018 Palu Earthquake

Long-term InSAR-based observations are prone to atmospheric delay interference. The active-phase signals emitted and recorded back by sensors during imaging are easily disturbed by the electron content in the ionospheric layer and the water vapor content in the tropospheric layer. Given that the short wavelength of the C-band used by Sentinel-1 is more sensitive to tropospheric delay than to ionospheric delay, in this work, we utilized InSAR Sentinel-1 data to observe the postseismic deformation that occurred following the 2018 Palu earthquake and to evaluate the effect of tropospheric delay on the estimated interferogram time series. The cloud computation of Looking into Continent from Space with Synthetic Aperture Radar (LiCSAR) and LiCSBAS was used to generate interferograms and analyze the time series. Here the atmospheric delay was modeled by using Generic Atmospheric Correction Online Service (GACOS) and removed from the generated interferograms. Results showed that the annual velocity and cumulative line-of-sight (LOS) displacement were refined by correcting the atmospheric delay. Specifically, by applying GACOS, the standard deviation of the generated interferograms decreased by up to 76.6%. GNSS observations were utilized to verify the improvement due to the removal of tropospheric noise. We found that LOS displacement with GACOS correction better fitted the GNSS observation than LOS displacement without GACOS correction. Therefore, atmospheric correction plays an important role in long-term InSAR-based observations, especially in avoiding any bias in the interpretation of the estimated time series.

Gaseous ethylbenzene removal by photocatalytic TiO2 nanoparticles immobilized on glass fiber tissue under real conditions: evaluation of reactive oxygen species contribution to the photocatalytic process.

Photocatalytic oxidation (PCO) using a TiO2 catalyst is an effective technique to remove gaseous volatile organic compounds (VOCs). Herein, a lab-scale continuous reactor is used to investigate the photocatalytic performance toward ethylbenzene (EB) vapor removal over TiO2 nanoparticles immobilized on glass fiber tissue. The role of the reactive species in the removal of EB and the degradation pathway were studied. Firstly, the effect of key operating parameters such as EB concentration (13, 26, 60mg/m3), relative humidity levels (From 5 to 80%), gas carrier composition (dry air + EB, O2 + EB and N2 + EB) and ultraviolet (UV) radiation wavelength (UV-A 365nm, UV-C 254nm) were explored. Then, using superoxide dismutase and tert-butanol as trapping agents, the real contribution of superoxide radical anion (O2.-) and hydroxyl radicals (OH.) to EB removal was quantified. The results show that (i) small water vapor content enhances the EB degradation; (ii) the reaction atmosphere plays an important role in the photocatalytic process; and (iii) oxygen atmosphere/UV-C radiation shows the highest EB degradation percentage. The use of radical scavengers confirms the major contribution of the hydroxyl radical to the photocatalytic mechanism with 75% versus 25% for superoxide radical anion.

An assessment of land energy balance over East Asia from multiple lines of evidence and the roles of the Tibet Plateau, aerosols, and clouds

Abstract. With high emissions of aerosols and the known world's “Third Pole” of the Tibet Plateau (TP) in East Asia, knowledge on the energy budget over this region has been widely concerned. This study first attempts to estimate the present-day land energy balance over East Asia by combining surface and satellite observations as well as the atmospheric reanalysis and Coupled Model Intercomparison Project Phase 6 (CMIP6) simulations. Compared to the global land budget, a substantially larger fraction of atmospheric shortwave radiation of 5.2 % is reflected, highly associated with the higher aerosol loadings and more clouds over East Asian land. While a slightly smaller fraction of atmospheric shortwave absorption of 0.6 % is unexpectedly estimated, possibly related to the lower water vapor content effects due to the thinner air over the TP to overcompensate for the aerosol and cloud effects over East Asian land. The weaker greenhouse effect and fewer low clouds due to the TP are very likely the causes of the smaller fraction of East Asian land surface downward longwave radiation. Hence, high aerosol loadings, clouds, and the TP over East Asia play vital roles in the shortwave budgets, while the TP is responsible for the longwave budgets during this regional energy budget assessment. The further obtained cloud radiative effects suggest that the presence of clouds results in a larger cooling effect on the climate system over East Asian land than that over the globe. This study provides a perspective to understand fully the roles of potential factors in influencing the different energy budget assessments over regions.

Precipitable Water Vapor and Fractional Clear Sky Statistics within the Big Telescope Alt-Azimuthal Region

The development of a network of ground-based telescopes requires detailed astroclimatic studies. This paper presents the spatial distributions of precipitable water vapor (PWV), total cloud cover (TCC) and cloud base height (CBH). With the aim of a representative description of the precipitable water vapor, a method for correcting this characteristic which takes into account the underlying surface is proposed. The method uses the exponential decrease in the water vapor content with the altitude and is based on the calculation of the averaged elevation of the grid nodes around the site. By applying this correction method, the seasonal changes in the median PWV values at the sites of Ali, Muztag-Ata and Suffa, as well as within the Chajnantor area are estimated. We show that the decrease of PWV with the altitude is exponential with a height scale of 1000 m for the sites in South America and Eurasia. The astroclimatic characteristics within the Big Telescope Alt-azimuthal (BTA) region (40∘N–50∘N; 35∘E–55∘E) are estimated. In this region, the sites suitable for the millimeter and submillimeter (mm/submm) observations are revealed. New sites are Mt. Horai and Mt. Kurapdag. In addition, we show that the Era-5 reanalysis data overestimate the PWV values by 1–2 mm and describe changes in the monthly medians of PWV. Comparison of the calculated medians with the measured PWV show that the correlation coefficient between these characteristics is 0.97.

ИЗУЧЕНИЕ ХАРАКТЕРИСТИК ОБЛАЧНОЙ АТМОСФЕРЫ ПО РЕЗУЛЬТАТАМ ИЗМЕРЕНИЙ СПЕКТРОВ ЕЕ НИСХОДЯЩЕГО СВЧ-ИЗЛУЧЕНИЯ В ОБЛАСТИ РЕЗОНАНСНОГО ПОГЛОЩЕНИЯ ВОДЯНОГО ПАРА 18,0-27,2 ГГЦ

The paper deals with studying the atmospheric characteristics based on spectral microwave radiometric measurements in the 18.0-27.2 GHz band close to the water vapor absorption line. The results of analyzing the ground-based measurements of clear-sky and cloudy atmosphere radiation with the P22M microwave radiometer-spectrometer performed at Fryazino Branch of Kotelnikov Institute of Radioengineering and Electronics of Russian Academy of Sciences are presented. The measurements have been carried out almost continuously since July 2017. The seasonal variability of clear-sky self-radiation spectra in the 18.0-27.2 GHz frequency band is analyzed. Estimates are made for the error in the linear approximation of the dependence between clear-sky brightness temperature and atmospheric integrated water vapor retrieved from radiosonde data. A possibility of studying the variability of liquid water content in clouds of various types with a spatial resolution about 200 m and a temporal resolution of 10 s is demonstrated. The time series of the brightness temperature spectra may be a basis for an operational analysis of the temporal variability of atmospheric integrated water vapor and cloud liquid water content.

Sensor Based on a Solid Oxide Electrolyte for Measuring the Water-Vapor and Hydrogen Content in Air

The present communication describes the results of the performance and the assessment of a sensor based on a solid oxide electrolyte with a composition of 0.9ZrO2 + 0.1Y2O3 (YSZ), equipped with a ceramic diffusion barrier for measuring the water vapor and hydrogen content in air. The possibility of determining the concentration of water vapor and hydrogen in the air is based on the measurement of the limiting current value. For the calculation of the steam and hydrogen concentration in ambient air, analytical expressions were obtained and applied, using the limiting current values measured in air with a standard oxygen concentration of 20.9 vol.% and in the analyzed air. A two-stage method for the determination of the hydrogen and steam amount in ambient air is proposed. It is stated that the sensor operates successfully at the temperature of 700 °C and can be applied for the continuous determination of steam or hydrogen concentrations in air.

Sea Surface Temperature Impact on Diurnal Cycle and Seasonal Evolution of the Guinea Coast Rainfall in Boreal Spring and Summer

Abstract ERA5 reanalyses and observations of convective clouds and precipitation are used over the northern Gulf of Guinea between 7°W and 3°E to study the influence of ocean surface temperature and the land–sea temperature gradient on Guinea Coast rainfall (GCR) in boreal spring and summer. Seasonal composites are calculated around two dates indexing the onset (Tref) and demise (Tend) of the GCR. The Tref date corresponds to the emergence of the equatorial upwelling in boreal spring, which “pushes” the zonal precipitation belt northward against the Guinea coast. The Tend date characterizes the emergence of the coastal upwelling in July, which is known to coincide with the beginning of the “Little Dry Season” that lasts until September. Along the Guinea Coast, the diurnal cycle of the air–sea temperature gradient controls precipitation through the land–sea breeze, which explains why precipitation reaches its maximum around noon over the ocean, and in the late afternoon over the continent. The emergence of the Guinea Coast upwelling in July induces a weakening of southerlies on a seasonal scale, and a weaker land breeze on a diurnal scale. It induces a decrease in the convergence of humidity transport across the coast and in coastal oceanic precipitation. Therefore, the GCR is seasonally controlled by the latitude of the maximum tropospheric water vapor content and the annual cycle of the West African monsoon, but the ocean surface temperature is responsible for the abruptness of its onset via the intensification of the equatorial upwelling around the end of May, and possibly of its demise as well via the emergence of the coastal upwelling by early July.

Comparison of the Integral Water Vapor Content of the Atmosphere by Data of the Global Forecast System (GFS) and GNSS Observations (Primorski Krai, Russia)

Comparison of the Integral Water Vapor Content of the Atmosphere by Data of the Global Forecast System (GFS) and GNSS Observations (Primorski Krai, Russia)

Temporal and Spatial Distribution of Cloud Water Content in Arid Region of Central Asia

To evaluate the distribution characteristics of water vapor content (WVC), cloud liquid water content (CLWC) and cloud ice water content (CIWC) in arid areas of central Asia from 1980 to 2019 were analyzed by using average data of ERA5 in the European Centre for Medium-Range Weather Forecasts. The results show that: On the spatial scale, the WVC in the arid area of central Asia is mainly between 2 and 26 kg·m−2. The area of maximum water vapor content is distributed in southwestern Kazakhstan and southwestern Tajikistan, with a maximum value of 26 kg·m−2. The minimum areas are distributed in eastern Tajikistan, central Kyrgyzstan, central Tajikistan, and western Xinjiang, China, with the lowest WVC of 2 kg·m−2. The maximum of CLWC areas were mainly distributed in northwest Kazakhstan, with a maximum value of 0.08 kg·m−2, while the minimum areas were distributed in Tajikistan, eastern Kyrgyzstan, and northwest China, with a minimum value of 0.02 kg·m−2. The maximum areas of CIWC were distributed in the north of Tajikistan and the west of Kyrgyzstan, possessing a maximum value of 0.06 kg·m−2. The minimum area is distributed in the western part of Central Asia with a minimum value of 0.01 kg·m−2. From 1980 to 2019, the WVC generally increased, while the annual average CIWC and CLWC appeared a downward trend.