Increase In Water Vapor Content Research Articles

Water vapor condensation behavior on different wetting surfaces via molecular dynamics simulation

Understanding water vapor condensation behavior at molecular level provides critical insights and useful guidance towards applications such as atmospheric water harvesting. In this work, condensation behavior of water vapor with a range of concentrations is investigated by molecular dynamics simulation on surfaces with different wetting states, viz. hydrophilic, hydrophobic, superhydrophilic, and superhydrophobic under five levels of water vapor content. The effect of water vapor content on condensation morphology, condensation beginning time, number of water molecules condensed over time, and accumulation rate are quantitatively examined. The results demonstrate that water condensation mass increases linearly with time on hydrophilic and superhydrophilic surfaces, while displaying a two-stage behavior on hydrophobic and superhydrophobic surfaces. The increase at the first stage is slower than the second stage. Higher water vapor content enables earlier nucleation and shortens the duration of the slow increase stage for hydrophobic and superhydrophobic surfaces. Quantitatively, water condensation mass increases linearly with the relative humidity of the vapor, and the coefficient with relative humidity on the hydrophilic, hydrophobic, superhydrophilic and superhydrophobic surfaces is 25.74 × 10–19, 8.31 × 10–19, 27.63 × 10–19, and 1.34 × 10–19, respectively. Our results show that increasing water vapor content has more significant impact on hydrophilic and superhydrophilic surfaces than hydrophobic and superhydrophobic surfaces. In addition, increasing water vapor content has minor effect on condensation rate in the slow increase stage on hydrophobic and superhydrophobic surfaces, but significantly increase the condensation rate on the rapid increase stage.

The Role of Atmospheric Stabilities and Moisture Convergence in the Enhanced Dry Season Precipitation over Land from 1979 to 2021

Abstract Between 1979 and 2021, global ocean regions experienced a decrease in dry season precipitation, while the trend over land areas varied considerably. Some regions, such as southeastern China, the Maritime Continent, eastern Europe, and eastern North America, showed a slight increasing trend in dry season precipitation. This study analyzes the potential mechanisms behind this trend by using the fifth major global reanalysis produced by ECMWF (ERA5) data. The analysis shows that the weakening of downward atmospheric motions played a critical role in enhancing dry season precipitation over land. An atmospheric moisture budget analysis revealed that larger convergent moisture fluxes lead to an increase in water vapor content below 400 hPa. This, in turn, induced an unstable tendency in the moist static energy profile, leading to a more unstable atmosphere and weakening downward motions, which drove the trend toward increasing dry season precipitation over land. More water vapor in the low troposphere is because of higher moisture convergence and moisture transport from ocean to land regions. In summary, this study demonstrates the intricate elements involved in altering dry season rainfall trends over land, which also emphasizes the importance of comprehending the spatial distribution of the wet-get-wetter and dry-get-drier paradigm. Significance Statement This study found that global land precipitation during the dry season slightly increased from 1979 to 2021, while precipitation over oceans declined. Moist static energy analysis showed a trend toward less stability in areas with increased dry season precipitation and the opposite trend in regions with declining precipitation. Water vapor content trends and dynamic components were the primary controlling mechanism for precipitation trends. Furthermore, the hotspots with pronounced increases or decreases in dry season precipitation reflect local circulation changes influenced by anthropogenic or natural factors.

The effect of multiple factors on changes in organic-inorganic fractions of condensable particulate matter during coal combustion

Condensable particulate matter (CPM) from coal combustion is the focus of current pollutant emission studies, and CPM can be divided into inorganic and organic fractions according to the component characteristics. At present, the effects of different factors in the combustion process on the organic and inorganic components of CPM have not been discussed systematically. Here, we conducted combustion experiments collected the generated CPM on a well-controlled drip tube furnace, and investigated the effects of different factors on the generation of organic and inorganic components of CPM by varying the furnace wall insulation temperature, the ratio of gas supply components and the water vapor content in the flue gas. The results showed that the increase in combustion temperature (1300–1500 °C) and oxygen concentration (15–25%) reduced the total CPM generation by 9.8% and 19.98%, respectively, and the intervention of water vapor increased the ability of the whole CPM sampling device to capture ultrafine condensable particles. The generation of CPM organic components decreased with the enhancement of combustion temperature and oxygen content on combustion characteristics, and alkanes shifted to low carbon content. The amount of CPM inorganic components increased with the increase of water vapor content in the flue gas, and this change was dominated by SO42−. The above results provide a feasible idea for the next step of the precise reduction of CPM components.

Effect of water vapor content on the corrosion mechanism of HR3C in simulated oxy-coal combustion environment

The corrosion performance of the HR3C steels covered with salt deposition (Na2SO4:K2SO4 = 1:1) was investigated under various water vapor content at 700 °C. Results show that the HR3C alloy undergoes severe pitting and sulfidation in a dry corrosive atmosphere (0.5SO2-4O2-CO2) and the corrosion products are peculiarly prone to peel off. In comparison, the corrosion behavior is gradually mitigated with increasing water vapor content. In highly humid corrosive gas (0.5SO2-4O2-20H2O-CO2), the corrosion degree is remarkably faint and the dominant corrosion mode is oxidation. The mechanism responsible for the transition of corrosion mode as water vapor content varied is discussed in detail.

Observed changes in hydroclimate attributed to human forcing

Observational and modeling studies indicate significant changes in the global hydroclimate in the twentieth and early twenty-first centuries due to anthropogenic climate change. In this review, we analyze the recent literature on the observed changes in hydroclimate attributable to anthropogenic forcing, the physical and biological mechanisms underlying those changes, and the advantages and limitations of current detection and attribution methods. Changes in the magnitude and spatial patterns of precipitation minus evaporation (P–E) are consistent with increased water vapor content driven by higher temperatures. While thermodynamics explains most of the observed changes, the contribution of dynamics is not yet well constrained, especially at regional and local scales, due to limitations in observations and climate models. Anthropogenic climate change has also increased the severity and likelihood of contemporaneous droughts in southwestern North America, southwestern South America, the Mediterranean, and the Caribbean. An increased frequency of extreme precipitation events and shifts in phenology has also been attributed to anthropogenic climate change. While considerable uncertainties persist on the role of plant physiology in modulating hydroclimate and vice versa, emerging evidence indicates that increased canopy water demand and longer growing seasons negate the water-saving effects from increased water-use efficiency.

Study of the High‐Temperature Oxidation Behavior of SUS430 Ferritic Stainless Steel Under Different Content of Water Vapor Atmosphere

The oxidation behavior of SUS430 ferritic stainless steel is studied during isothermal oxidation at 1100 °C for 2 h under a mixture of 10, 30, and 50% water vapor and air, and oxidation kinetics curves are drawn. The surface morphology and phase composition of oxide scale are analyzed using X‐Ray diffractometer, scanning electron microscope, and energy dispersive spectrometer. The oxidation kinetic curves under three different humidities are S‐shaped and include three stages: induction period, acceleration period, and deceleration period. The controlling steps under 10% water vapor and air are nucleation and growth, while under 30% and 50% water vapor and air are both phase boundary control reactions. The induction period becomes shorter and the breakaway oxidation occurs earlier with increasing water vapor content. The structure of oxide scale produced is layered, with the outer layer being iron oxide and the inner layer being mainly the Fe–Cr spinel phase. The volatilization of Cr and the growth stress of the Cr2O3 layer cause the formation of nodules, and a large number of cracks are generated in oxide scale. The cracks provide diffusion paths, accelerating the diffusion of Fe ions and electrons, as well as the erosion of the substrate.

Performance of the Atmospheric Radiative Transfer Simulator (ARTS) in the 600–1650 cm−1 Region

The Atmospheric Radiative Transfer Simulator (ARTS) has been widely used in the radiation transfer simulation from microwave to terahertz. Due to the same physical principles, ARTS can also be used for simulations of thermal infrared (TIR). However, thorough evaluations of ARTS in the TIR region are still lacking. Here, we evaluated the performance of ARTS in 600–1650 cm−1 taking the Line-By-Line Radiative Transfer Model (LBLRTM) as a reference model. Additionally, the moderate resolution atmospheric transmission (MODTRAN) band model (BM) and correlated-k (CK) methods were also used for comparison. The comparison results on the 0.001 cm−1 spectral grid showed a high agreement (sub-0.1 K) between ARTS and LBLRTM, while the mean bias difference (MBD) and root mean square difference (RMSD) were less than 0.05 K and 0.3 K, respectively. After convolving with the spectral response functions of the Atmospheric Infra-Red Sounder (AIRS) and the Moderate Resolution Imaging Spectroradiometer (MODIS), the brightness temperature (BT) differences between ARTS and LBLRTM became smaller with RMSDs of <0.1 K. The comparison results for Jacobians showed that the Jacobians calculated by ARTS and LBLRTM were close for temperature (can be used for Numerical Weather Prediction application) and O3 (excellent Jacobian fit). For the water vapor Jacobian, the Jacobian difference increased with an increasing water vapor content. However, at extremely low water vapor values (0.016 ppmv in this study), LBLRTM exhibited non-physical mutations, while ARTS was smooth. This study aims to help users understand the simulation accuracy of ARTS in the TIR region and the improvement of ARTS via the community.

Study of the interaction between NH3 and NO in the reduction zone of air-staged ammonia combustion under high moisture atmosphere

NH3 is used as a hydrogen-rich fuel, and the water vapor content produced by combustion can reach 30%. However, high NOx emission is one of the main problems restricting its application. The air-staged combustion is an effective low-NOx combustion strategy, subdividing the combustion process into three typical sections: the main combustion zone, the reduction zone, and the burnout zone. Fully utilizing the reaction between NH3 and NO in the reduction zone is expected to achieve an effective control of NOx emission. This research aims to explore the reduction ability of the residual NH3 on NO reduction in the reduction zone under high moisture atmosphere formed by ammonia combustion. An isothermal flow reactor was used to study the kinetic characteristics of the NH3/NO reaction under no-oxygen or residual low-oxygen condition in a wide temperature range (1073–1773K) and a high water vapor content range (0–50%). Additionally, three chemical kinetic models were used in simulations. The results showed that oxygen significantly changes the effect of water vapor on the NH3/NO reaction. In the absence of oxygen, water vapor has less effect on NH3/NO reaction at lower temperatures (<1500K). In the presence of oxygen, the increase of water vapor content leads to a significant shift of the reaction temperature window to higher temperatures and a decrease of the maximum NO reduction efficiency. Finally, the remarks about using residual NH3 to complete NOx removal in ammonia combustion were discussed.

Investigating variable importance in ground-level ozone formation with supervised learning

Tropospheric ozone (O3) is a greenhouse gas and an influential ground-level air pollutant, thus determining the importance of various factors related to O3 formation is essential. However, O3 concentrations simulated by the available climate models exhibit significant variances, indicating the insufficiency of such models in modeling the O3 formation process accurately. This study used machine learning to identify and understand the impact of various factors on O3 formation and thereby predict O3 concentrations under different climate change and emission reduction scenarios. We employed six supervised learning models to estimate O3 concentrations by using 14 meteorological and chemical variables. We found that deep neural network (DNN) and long short-term memory (LSTM) models could accurately predict O3 concentrations. The variable importance analyses emphasized the significant positive contribution of solar radiation to O3; meanwhile both nitrogen oxides and volatile organic compounds negatively contributed to O3 concentrations. Predicted O3 concentrations based on our DNN and LSTM models in different climate change scenarios showed that increase in water vapor content could offset the effects of raised temperature, and controlling anthropogenic gases, especially carbon monoxide, might have the most bearing on controlling O3 in the future.

Future intensification of precipitation and wind gust associated thunderstorms over Lake Victoria

Severe thunderstorms affect more than 30 million people living along the shores of Lake Victoria (East Africa). Thousands of fishers lose their lives on the lake every year. While deadly waves are assumed to be initiated by severe wind gusts, knowledge about thunderstorms is restricted to precipitation or environmental proxies. Here we use a regional climate model run at convection-permitting resolution to simulate both precipitation and wind gusts over Lake Victoria for a historical 10-year period. In addition, a pseudo global warming simulation provides insight into the region’s future climate. In this simulation, ERA5’s initial and boundary conditions are perturbed with atmospheric changes between 1995–2025 and 2070–2100, projected by CMIP6’s ensemble mean. It was found that future decreases in both mean precipitation and wind gusts over Lake Victoria can be attributed to a weaker mean mesoscale circulation that reduces the trigger for over-lake nighttime convection and decreases the mean wind shear. However, an intensification of extremes is projected for both over-lake precipitation and wind gusts. The observed ∼7 %K−1 Clausius–Clapeyron extreme precipitation scaling is ascribed to increased water vapor content and a compensation of weaker mesoscale circulations and stronger thunderstorm dynamics. More frequent wind gust extremes result from higher wind shear conditions and more compound thunderstorms with both intense rainfall and severe wind gusts. Overall, our study emphasizes Lake Victoria’s modulating role in determining regional current and future extremes, in addition to changes expected from the Clausius–Clapeyron relation.

Distinct impacts of humidity profiles on physical properties and secondary formation of aerosols in Shanghai

As a key component in the atmosphere, the increase in water vapor content can aggravate air pollution by promoting hygroscopic growth and secondary formation of aerosols. In this study, water vapor mixing ratio (WVMR) profiles retrieved from Raman lidar at night in Shanghai were used to evaluate the accuracy of a maintained microwave radiometer (MWR) and reanalysis datasets (ERA5 from ECMWF and MERRA-2 from NASA). The relative humidity (RH) profiles from radiosonde and reanalysis datasets were used to explore the influence of humidity vertical distributions on aerosol physical properties and secondary formation. There was a large WVMR difference between MWR and Raman lidar, with a mean bias (MB) and a root mean square error (RMSE) being 2.47 g/kg and 3.29 g/kg, respectively. However, the WVMR from ERA5 and MERRA-2 showed excellent agreement (correlation coefficients were both 0.94, N = 11288 and 3619, respectively) with that from Raman lidar and high accuracy especially MERRA-2, which are more suitable for meteorological and climatic applications than MWR. It was found that RH had a significant effect on the vertical distribution of aerosol extinction coefficient (AEC). Aerosol hygroscopic growth caused by high RH resulted in an obvious enhancement of AEC at 355 nm below 610 m in summer. As a good indicator for determining contribution of aerosol secondary formation, large ratios of PM2.5 to CO (PM2.5/CO > 0.08) corresponded to high nitrogen oxidation ratios (NOR), sulfur oxidation ratios (SOR), and also high RH below 800 m during nighttime in winter, suggesting that RH and its vertical distribution played an important role in the aerosol secondary formation. The RH was high in the vertical direction when nitrate and sulfate mainly come from the secondary formation (NOR >0.1 or SOR >0.1), and in contrast to nitrate, the secondary formation for sulfates tended to depend on higher RH (>70%), which indicated that more stringent measures for nitrogen oxides emission reduction should be implemented in Shanghai to reduce the pollution of secondary aerosols in the future.

Impact of Lightning Data Assimilation on Forecasts of a Leeward Slope Precipitation Event in the Western Margin of the Junggar Basin

A moderate precipitation event occurring in northern Xinjiang, a region with a continental climate with little rainfall, and in leeward slope areas influenced by topography is important but rarely studied. In this study, the performance of lightning data assimilation is evaluated in the short-term forecasting of a moderate precipitation event along the western margin of the Junggar Basin and eastern Jayer Mountain. Pseudo-water vapor observations driven by lightning data are assimilated in both single and cycling analysis experiments of the Weather Research and Forecast (WRF) three-dimensional variational (3DVAR) system. Lightning data assimilation yields a larger increment in the relative humidity in the analysis field at the observed lightning locations, and the largest increment is obtained in the cycling analysis experiment. Due to the increase in water vapor content in the analysis field, more suitable thermal and dynamic conditions for moderate precipitation are obtained on the leeward slope, and the ice-phase and raindrop particle contents increase in the forecast field. Lightning data assimilation significantly improves the short-term leeward slope moderate precipitation prediction along the western margin of the Junggar Basin and provides the best forecast skill in cycling analysis experiments.

Thermodynamic modeling of nickel and iron reduction from B&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; – CaO – Fe&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; – NiO melt by СО – СО&lt;sub&gt;2&lt;/sub&gt; and Н&lt;sub&gt;2&lt;/sub&gt; – Н&lt;sub&gt;2&lt;/sub&gt;О mixtures

To predict the conditions for metals reduction from an oxide melt by gas in bubbling processes, a thermodynamic modeling technique has been developed that provides an approximation to real systems. The main difference between the accepted method and the well-known one is in conducting successive calculation cycles with withdrawal of the generated gases and the metal phase from the working medium. This paper presents the results of thermodynamic modeling of nickel and iron reduction processes from B2O3 – CaO– Fe2O3 – NiO melts by mixtures of CO– CO2 and H2 – H2O containing 0 – 60 % CO2 (H2O) in the temperature range of 1273 – 1673 K. The calculations evaluated the content of nickel and iron oxides in the melt and the degree of their reduction. It is shown that, regardless of the gas composition, this process proceeds in several stages. At the first stage, Fe2O3 is reduced to Fe3O4 and FeO. СFe2O3 values decrease to almost zero, while СFe3O4 and CFeO increase simultaneously. By the end of the phase, СFeO reaches its maximum value. At the second stage, the Fe3O4 → FeO transition occurs, when СFe3O4 values reach maximum, nickel and iron begin to reduce to metal. At reduction by CO– CO2 mixture, an increase in temperature reduces the metallization of both nickel and iron. Similarly, an increase in the CO2 content of the introduced gas affects. During interaction of the oxide melt with a gas containing 60 % CO2 , the third stage is absent. At reduction by H2 – H2O mixture, an increase in temperature reduces the metallization of nickel, but increases metallization of iron. With increasing water vapor content in the introduced gas, the degree of metallization of both nickel and iron decreases. The obtained data are useful for creating technologies for selective reduction of metals and formation of ferronickel of the required composition.

Surface Temperature Retrieval From Gaofen-5 Observation and its Validation

Surface temperature (ST) plays a great role in urban heat island effect, environment monitoring, earth resources monitoring, and water balance at local and global scales. The Chinese Gaofen-5 (GF5) satellite can capture Earth’s thermal infrared information for use in national high-resolution Earth observations. In this article, the nonlinear split-window algorithm and the refined generalized split-window method are used to retrieve sea surface temperature (SST) and land surface temperature (LST) from GF5 observations. For different atmospheric and surface conditions, the algorithm coefficients are calculated using a statistical regression method from the numerical values simulated with the atmospheric radiative transfer model MODTRAN 5.0. The simulation results show that the root mean square error (RMSE) for SST and LST retrieval ranges from 0.09 K to 0.46 K and 0.19 K to 0.69 K, respectively, with increasing water vapor content (WVC). To validate the retrieved STs, Moderate Resolution Imaging Spectroradiometer (MODIS) STs extracted from the MYD11A1 product are used. Note that the RMSEs of both the LST and SST are less than 3.3 K. The RMSE for SST retrieval varies from 1.2 K to 1.45 K, with a mean value of 1.33 K; the RMSE for LST retrieval ranges from 1.57 K to 3.3 K, with a mean value of 2.41 K.

Study of the effect of formation water during reserves estimation and designing hydrocarbon recovery of oil and gas condensate fields

Currently, exploratory thermodynamic studies of the PVT reservoir fluids properties to assess the effect of condensate water on reserves estimation, design and development of the fields are carried out on Russian National and international oil companies. Such PVT ratios settings allow a wide range of pressures and temperatures to be used to study phase transitions of hydrocarbon systems. Conducted experimental studies of gas condensate systems showed a negative effect of formation water on the amount of condensate extraction during development. The studies were conducted on recombined samples of gas separation, formation water and saturated condensate taken from the wells during the pilot development of the Srednetyungskoe field in Western Yakutia. Wherein, a pattern was found of increasing the loss of high molecular hydrocarbons at the stage of the onset of condensation with increasing water vapor content in the gas condensate system. As a result of studies of the dependence of hydrocarbon losses during the increasing in the water vapor content in the system, certain parameters are the initial ones when calculating the reserves of hydrocarbon and non-hydrocarbon components in natural gas, the development of designing and field development. The aim of thermodynamic investigations was to determine the effect of formation and condensation water vapors on the condensate recovery rate during the isothermal condensation process, which manifests itself when the pressure decreases in the oil and gas condensate field.

Numerical simulation of the influence of water vapor on gas explosions in a high-pressure environment

Gas explosion seriously threatens the employees security and restricts the safe production of coal mines. Therefore, it is particularly essential to investigate the prevention and control of gas explosions. In this study, a two-dimensional numerical model of a spherical explosion tank was developed to explore the effects of water vapor on gas explosions in a high-pressure environment. Explosion parameters of 10% gas, 1 MPa pressure, and water vapor contents varying from 0% to 8% were simulated using FLUENT software. The results show that the maximum explosion pressure and temperature of the premixed gas gradually decrease with increasing water vapor content, i.e., when the water vapor content is increased from 0% to 8%, the maximum explosion pressure and temperature of the gas mixture decreases from 2.52 MPa and 2092 K under dry conditions to 1.62 MPa and 1714 K with 8% water vapor. The attenuation amplitude is also reduced upon the addition of steam. Water vapor in premixed gas therefore plays a vital role in suppressing gas explosions.

Heavy Daily Precipitation Events in the CMIP6 Worst-Case Scenario: Projected Twenty-First-Century Changes

AbstractHeavy precipitation is often the trigger for flooding and landslides, leading to significant societal and economic impacts, ranging from fatalities to damage to infrastructure to loss of crops and livestock. Therefore, it is critical that we have a better understanding of how it may be changing in the future. Based on model projections from phases 3 and 5 of the Coupled Model Intercomparison Project (CMIP3 and CMIP5), future daily precipitation is likely to increase in intensity. The main goal of this study is to examine possible improvements in the representation of intense and extreme precipitation by a new set of climate models contributing to phase 6 of CMIP effort (CMIP6) and to quantify its projected changes under the highest emissions scenario by the end of the current century [i.e., Shared Socioeconomic Pathway (SSP) SSP5-8.5]. Daily precipitation data from six CMIP6 models were analyzed that have a nominal horizontal grid spacing around 100 km and provide data for the highest emissions scenario SSP5-8.5. Two of the six CMIP6 models overestimate the extreme precipitation (defined as the 99th percentile of the precipitation distribution) in the tropics, leading to large biases in the right tail of the daily precipitation over the tropics. Consistent with the CMIP5 results, the CMIP6 models projected increased heavy daily precipitation and increased width of the right tail of the precipitation distribution associated with increased water vapor content.

Research on gas side performance of staggered fin-tube bundles with different serrated fin geometries

This investigation conducted experiments on the gas-side performance of serrated spiral fin-and-tube heat exchanger with staggered layouts. The number of tube rows is 10 under the Reynolds numbers of 6000 to 12,000. The influences of varied water vapor content and fin geometry were explored. The results showed that the increase of water vapor content leads to an increase in the Nusselt number of the serrated fin and twisted serrated fin, and the effect on serrated fin was more significant. Besides, the decrease in the Euler number of both fin tube was observed with the water vapor content increasing. The twisting in the top of segment fin corresponded to a significant increase in the Nusselt and Euler numbers. Finally, the comparison of overall performance between the two types of fin tube was performed, and the results showed that the twisted serrated fin has better performance in the current experimental range.

Effect of water vapor content during the solid state synthesis of manganese-doped magnesium fluoro-germanate phosphor on its chemistry and photoluminescent properties

Several samples of magnesium fluoro-germanate doped with Mn4+ were prepared by solid state synthesis with a different water vapor content in the synthesis atmosphere. A significant decrease in quantum yield and emission intensity was observed with the increase in water vapor content during synthesis. Although there was little effect on the emission spectra, the changes in excitation spectra indicate the dominance of magnesium germanate instead of magnesium fluoro-germanate at high water vapor content. X-ray diffraction (XRD) results show that the pure phase was only achieved with the least amount of water vapor. Refinement of XRD data estimates the quantities of different phases present. The effect on the grain size and morphology is also remarkable, as demonstrated by scanning electron microscopy imaging. The reason behind the changes is discussed in detail. The temperature dependence of the photoluminescence spectra was measured between room temperature and 500 °C where the luminescence is quenched to nearly 3% of its initial value.

Impact of water vapor transfer on a Circum-Bohai-Sea heavy fog: Observation and numerical simulation

a wide-range winter frontal fog that happened over Circum-Bohai-Sea (CBS) on December 17–192,016 was observed using satellite cloud image inversion, surface, ocean buoy, and radiosonde data. The evolution of fog processes was investigated with numerical simulations using the Weather Research and Forecasting (WRF) Model together with the FNL (Final) reanalysis data. The results show that the WRF model can reproduce the features of the heavy fog generation and development. The observed results show following characteristics: (1) Before fog appearance, the southwest low-level jet (LLJ) of which the wind speed was over 16 m/s at 925 hPa developed. The LLJ carrying warm and wet air provided a stable inversion layer about 1200 m thick and continuous vapor transport to the CBS area, which is favorable for the formation of heavy fog. With the weak northwestern cold air moving towards the CBS area, a typical frontal fog process was triggered; (2) the weak cold air did not destroy the structure of low-level thermal inversion, and the heavy fog maintained. With the weak front moving towards the east, the foggy coverage continually extended over the sea surface, finally covering the Bohai Sea and the North Yellow Sea. A water-vapor sensitivity test suggests that with the LLJ continually conveying water vapor to the area, the accumulative effect of an increase in water vapor content took place in the low-level atmosphere, which changed the temperature and humidity structure of the boundary layer. The liquid water content, coverage area, and thickness of fog changed drastically.