In the task of inspecting underwater suspended pipelines,multi-beam sonar(MBS)can provide two-dimensional water column images(WCIs).However,systematic interferences(e.g.,sidelobe effects)may induce misdetection in WCI...In the task of inspecting underwater suspended pipelines,multi-beam sonar(MBS)can provide two-dimensional water column images(WCIs).However,systematic interferences(e.g.,sidelobe effects)may induce misdetection in WCIs.To address this issue and improve the accuracy of detection,we developed a density-based clustering method for three-dimensional water column point clouds.During the processing of WCIs,sidelobe effects are mitigated using a bilateral filter and brightness transformation.The cross-sectional point cloud of the pipeline is then extracted by using the Canny operator.In the detection phase,the target is identified by using density-based spatial clustering of applications with noise(DBSCAN).However,the selection of appropriate DBSCAN parameters is obscured by the uneven distribution of the water column point cloud.To overcome this,we propose an improved DBSCAN based on a parameter interval estimation method(PIE-DBSCAN).First,kernel density estimation(KDE)is used to determine the candidate interval of parameters,after which the exact cluster number is determined via density peak clustering(DPC).Finally,the optimal parameters are selected by comparing the mean silhouette coefficients.To validate the performance of PIE-DBSCAN,we collected water column point clouds from an anechoic tank and the South China Sea.PIE-DBSCAN successfully detected both the target points of the suspended pipeline and non-target points on the seafloor surface.Compared to the K-Means and Mean-Shift algorithms,PIE-DBSCAN demonstrates superior clustering performance and shows feasibility in practical applications.展开更多
The potential evapotranspiration of main ecosystems and its relationship with precipitation during the same period were studied,the results showed that precipitation did not meet the water requirement of main ecosyste...The potential evapotranspiration of main ecosystems and its relationship with precipitation during the same period were studied,the results showed that precipitation did not meet the water requirement of main ecosystems influencing ecosystem construction.Based on the data from Liaoning Provincial Department of Water Resources and Liaoning Meteorological Archives,the characteristics of water inflow and each component were analyzed,and it showed that the imbalance between supply and demand of water resource in main ecosystems was improved by means of developing cloud water resource to increase atmospheric precipitation.展开更多
Analyses of cloud water path （CWP） data over China available from the International Satellite Cloud Climatology Project （ISCCP） are performed for the period 1984-2004. Combined with GPCP precipitation data, cloud ...Analyses of cloud water path （CWP） data over China available from the International Satellite Cloud Climatology Project （ISCCP） are performed for the period 1984-2004. Combined with GPCP precipitation data, cloud water cycle index （CWCI） is also calculated. The climatic distributions of CWP are found to be dependent on large-scale circulation, topographical features, water vapor transport and similar distribution features which are found in CWCI except in the Sichuan Basin. Influenced by the Asia monsoon, CWP over China exhibits very large seasonal variations in different regions. The seasonal cycles of CWCI in different regions are consistent and the largest CWCI occurs in July. The long-term trends of CWP and CWCI are investigated, too. Increasing trends of CWP are found during the period with the largest increase found in winter. The decreasing trends of CWCI dominate most regions of China. The differences in long-term trends between CWP and CWCI suggest that CWP only can influence the variation of CWCI to a certain extent and that other factors need to be involved in cloud water cycle researches. This phenomenon reveals the complexity of the hydrological cycle related to cloud water.展开更多
This paper documents a study to examine the sensitivity to cloud droplet effective radius and liquid water path and the alleviation the energy imbalance at the top of the atmosphere and at the surface in the latest ve...This paper documents a study to examine the sensitivity to cloud droplet effective radius and liquid water path and the alleviation the energy imbalance at the top of the atmosphere and at the surface in the latest version of the Grid-point Atmospheric Model of the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics （LASG）, Institute of Atmospheric Physics （IAP） （GAMIL1.1.0）. Considerable negative biases in all flux components, and thus an energy imbalance, are found in GAMIL1.1.0. In order to alleviate the energy imbalance, two modifications, namely an increase in cloud droplet effective radius and a decrease in cloud liquid water path, have been made to the cloud properties used in GAMIL. With the increased cloud droplet effective radius, the single scattering albedo of clouds is reduced, and thus the reflection of solar radiation into space by clouds is reduced and the net solar radiation flux at the top of the atmosphere is increased. With the reduced cloud optical depth, the net surface shortwave radiation flux is increased, causing a net warming over the land surface. This results in an increase in both sensible and latent heat fluxes over the land regions, which is largely balanced by the increased terrestrial radiation fluxes. Consequently, the energy balance at the top of atmosphere and at the surface is achieved with energy flux components consistent with available satellite observations.展开更多
Based on relationships between cloud microphysical and optical properties, three different parameterization schemes for narrow and broad band optical properties in longwave region for water clouds have been presented....Based on relationships between cloud microphysical and optical properties, three different parameterization schemes for narrow and broad band optical properties in longwave region for water clouds have been presented. The effects of different parameterization schemes and different number of broad bands used on cloud radiative properties have been investigated. The effect of scattering role of cloud drops on longwave radiation fluxes and cooling rates in cloudy atmospheres has also been analyzed.展开更多
The role of Arctic clouds in the recent rapid Arctic warming has attracted much attention.However,Arctic cloud water paths(CWPs)from reanalysis datasets have not been well evaluated.This study evaluated the CWPs as we...The role of Arctic clouds in the recent rapid Arctic warming has attracted much attention.However,Arctic cloud water paths(CWPs)from reanalysis datasets have not been well evaluated.This study evaluated the CWPs as well as LWPs(cloud liquid water paths)and IWPs(cloud ice water paths)from five reanalysis datasets(MERRA-2,MERRA,ERA-Interim,JRA-55,and ERA5)against the COSP(Cloud Feedback Model Intercomparison Project Observations Simulator Package)output for MODIS from the MERRA-2 CSP(COSP satellite simulator)collection(defined as M2Modis in short).Averaged over 1980-2015 and over the Arctic region(north of 60°N),the mean CWPs of these five datasets range from 49.5 g/m^(2)(MERRA)to 82.7 g/m^(2)(ERA-Interim),much smaller than that from M2Modis(140.0 g/m^(2)).However,the spatial distributions of CWPs,show similar patterns among these reanalyses,with relatively small values over Greenland and large values over the North Atlantic.Consistent with M2Modis,these reanalyses show larger LWPs than IWPs,except for ERA-Interim.However,MERRA-2 and MERRA underestimate the ratio of IWPs to CWPs over the entire Arctic,while ERA-Interim and JRA-55 overestimate this ratio.ERA5 shows the best performance in terms of the ratio of IWPs to CWPs.All datasets exhibit larger CWPs and LWPs in summer than in winter.For M2Modis,IWPs hold seasonal variation similar with LWPs over the land but opposite over the ocean.Following the Arctic warming,the trends in LWPs and IWPs during 1980~2015 show that LWPs increase and IWPs decrease across all datasets,although not statistically significant.Correlation analysis suggests that all datasets have similar interannual variability.The study further found that the inclusion of re-evaporation processes increases the humidity in the atmosphere over the land and that a more realistic liquid/ice phase can be obtained by independently treating the liquid and ice water contents.展开更多
Tropical cyclone(TC) rainfall forecast has remained a challenge. To create initial conditions with high quality for simulation, the present study implemented a data assimilation scheme based on the EnKF method to inge...Tropical cyclone(TC) rainfall forecast has remained a challenge. To create initial conditions with high quality for simulation, the present study implemented a data assimilation scheme based on the EnKF method to ingest the satellite-retrieved cloud water path(C_(w)) and tested it in WRF. The scheme uses the vertical integration of forecasted cloud water content to transform control variables to the observation space, and creates the correlations between C_(w) and control variables in the flow-dependent background error covariance based on all the ensemble members, so that the observed cloud information can affect the background temperature and humidity. For two typhoons in 2018(Yagi and Rumiba), assimilating C_(w) significantly increases the simulated rainfalls and TC intensities. In terms of the average equitable threat score of daily moderate to heavy rainfall(5-120 mm), the improvements are over 130%, and the dry biases are cut by about 30%. Such improvements are traced down to the fact that C_(w) assimilation increases the moisture content, especially that further away from the TC center, which provides more precipitable water for the rainfall,strengthens the TC and broadens the TC size via latent heat release and internal wind field adjustment.展开更多
The effects of water and ice clouds on the cloud microphysical budget associated with rainfall are investigated through the analysis of grid-scale data from a series of two-dimensional cloud-resolving model equilibriu...The effects of water and ice clouds on the cloud microphysical budget associated with rainfall are investigated through the analysis of grid-scale data from a series of two-dimensional cloud-resolving model equilibrium sensitivity simulations. The model is imposed without large-scale vertical velocity. In the control experiment, the contribution from rainfall （cM） associated with net evaporation and hydrometeor loss/convergence is about 29% of that from the rainfall （Cm） associated with net condensation and hydrometeor gain/divergence and about 39% of that from the rainfall （CM） associated with net condensation and hydrometeor loss/convergence. The exclusion of ice clouds enhances rainfall contribution of CM, whereas it reduces rainfall contributions of Cm and cM. The removal of radiative effects of water clouds increases rainfall contribution of CM, barely changes rainfall contribution of Cm and reduces the rainfall contribution of cM in the presence of the radiative effects of ice clouds. Elimination of the radiative effects of water clouds reduces the rainfall contributions of CM and Cm, whereas it increases the rainfall contribution of cM in the absence of the radiative effects of ice clouds.展开更多
Cloud water samples, LWC （Liquid Water Content） and meteorological data were collected at the Clingmans Dome, Tennessee, high-elevation site in Great Smoky Mountains National Park during the warm season from 1994 th...Cloud water samples, LWC （Liquid Water Content） and meteorological data were collected at the Clingmans Dome, Tennessee, high-elevation site in Great Smoky Mountains National Park during the warm season from 1994 through 2011. This paper presents results from 2000 through the conclusion of the study in 2011. Samples were analyzed for SO42＂, NO3, NH4＋ and H＋. These measurements were supplemented by measurements of ambient air and precipitation concentrations to estimate dry and wet deposition. Cloud water concentrations, LWC, cloud frequency, various meteorological measurements and information on nearby forest canopy were used to model cloud water deposition to gauge trends in deposition. Total deposition was calculated as the sum of cloud, dry and wet deposition estimates. Concentrations and deposition fluxes declined over the study period. The decreases in cloud water SO42＂ and NO3 concentrations were 40 percent and 26 percent, respectively. Three-year mean 5042 and NO3 deposition rates decreased by 71 percent and 70 percent, respectively. Trends in concentrations and depositions were comparable with trends in SO2 and NOx emissions from Tennessee Valley Authority power plants and aggregated emission reductions from electric generating units in adjacent states. Back trajectories were simulated with the HYSPLIT model and aggregated over cloud sampling periods from 2000 through 2007 and 2009 through 2011. Trajectories during periods with high H＋ concentrations traveled over local EGU （Electric Generating Unit） emission sources in Tennessee and Kentucky to the Ohio River Valley, Alabama and Georgia with the conclusion that these source regions contributed to acidic cloud water deposition at Clingmans Dome. This work was supported by U.S. Environmental Protection Agency and the Tennessee Valley Authority with infrastructure support provided by the National Park Service.展开更多
The Water Cloud Model(WCM)plays a crucial role in active microwave soil moisture inversion applications.Empirical parameters are important factors affecting the accuracy of WCM simulation,but the current evaluation of...The Water Cloud Model(WCM)plays a crucial role in active microwave soil moisture inversion applications.Empirical parameters are important factors affecting the accuracy of WCM simulation,but the current evaluation of empirical parameters only considers the forward simulation process,and insufficient consideration is given to the model inversion problem.This study proposes a new estimation method for vegetation parameters in the WCM by combining the soil backscattering model and the objective function.The effectiveness of the method is then verified using measured data.Simultaneously,this study also analyzes the factors influencing the evaluation of vegetation parameters in the WCM,resulting in the following conclusions.First,blindly utilizing vegetation parameters recommended by previous model studies is not advisable.To ensure the accuracy of the simulation,it is necessary to adjust the vegetation parameters appropriately.Second,to ensure the ability of the WCM solving both forward and inverse problems,it is advisable to consider both soil backscatter and surface backscatter simulations in the construction of the cost function.Third,soil backscatter simulations have an impact on the solution of vegetation parameters,and more accurate soil scattering models provide a better representation of the modeled vegetation.This study presents a dependable method for resolving the vegetation parameters of the WCM,thereby offering a valuable reference for the application of the model in surface parameter inversion research.展开更多
This study quantitatively analyzes the effects of cloud seeding on precipitation and seasonal variations over the Boryeong Dam region,which has the lowest dam storage in South Korea,based on a one-year numerical simul...This study quantitatively analyzes the effects of cloud seeding on precipitation and seasonal variations over the Boryeong Dam region,which has the lowest dam storage in South Korea,based on a one-year numerical simulation for2021.The Morrison microphysics scheme in the WRF(Weather Research and Forecasting)model was modified to estimate differences in precipitation between simulations with seeding materials(Ag I and Ca Cl2;SEED)and without them(UNSD).The effect of cloud seeding on increasing precipitation or artificial rainfall(AR)between the two simulations was highest in August(average:0.21 mm;31%of the SEED-simulated monthly mean)and lowest in January(average:0.003 mm;30%).This large AR may be attributable to a combination of abundant moisture from the summer monsoon climate and enhanced cloud droplet growth resulting from cloud seeding.In the analysis of seasonal representative cases,cloud seeding demonstrated more pronounced effects in spring and summer,with mean 180-min accumulated AR values of 0.46 and 0.43 mm,respectively,within the study area.In the spring,where an actual flight experiment was conducted,the simulated mean180-min accumulated AR(1.41 mm)in the flight experiment area was close to the observed value(1.61 mm)for the same area.Additionally,cloud seeding promoted the hygroscopic growth of water vapor,thereby reducing the cloud water mixing ratio and increasing the rain water mixing ratio.Seasonal cross-sectional analysis further highlighted the impact of cloud seeding on changes in these two mixing ratios,with the most pronounced effects observed in spring and summer.展开更多
By using the microphysical data of stratiform cloud in Henan which were observed by PMS airborne cloud particle measure system on March 23 in 2007 and combining with the radar,satellite,sounding data,the macro and mic...By using the microphysical data of stratiform cloud in Henan which were observed by PMS airborne cloud particle measure system on March 23 in 2007 and combining with the radar,satellite,sounding data,the macro and micro physical structure characteristics of cloud were analyzed.The results showed that the average diameter of small cloud drop which was measured by FSSP-100 in the warm layer of cloud was mainly during 5-12 μm,and the average value was 7.33 μm.The biggest diameter of small cloud drop changed during 14-47 μm,and the average value was 27.80 μm.The total number concentration scope of small cloud drop was during 47.73-352.00 drop/cm3,and the average value was 160 drop/cm3.In the cold layer of cloud,the biggest diameter of small cloud particle(included the cloud droplet and the ice crystals)which was measured by FSSP-100 was 24.8 μm.The total number concentration scope of small cloud particle was during 0.899-641.000 drop/cm3,and the average value was 297 drop/cm3.The airborne King heat line liquid water content instrument observed that the super-cooling liquid water existed in the cloud.The super-cooling cloud water content changed during 0.02-0.20 g/m3,and the average value was 0.093 g/m3.The biggest value which was 0.202 g/m3 appeared in 4 368 m height(the temperature was-8.5 ℃).The particle spectrum type in the cloud was mainly the negative exponent type and the single peak type.展开更多
The characteristics of seasonal precipitation over the Tibetan Plateau （TP） were investigated using TRMM （Tropical Rain- fall Measuring Mission） precipitation data （3B43）. Sensitive regions of summer precipitati...The characteristics of seasonal precipitation over the Tibetan Plateau （TP） were investigated using TRMM （Tropical Rain- fall Measuring Mission） precipitation data （3B43）. Sensitive regions of summer precipitation interannual variation anomalies were investigated using EOF （empirical orthogonal function） analysis. Furthermore, the profiles of cloud water content （CWC） and precipitable water in different regions and seasons were analyzed using TRMM-3A12 data observed by the TRMM Microwave Imager. Good agreement was found between hydrometeors and precipitation over the eastern and southeastern TP, where water vapor is adequate, while the water vapor amount is not significant over the western and northern TE Further analysis showed meridional and zonal anomalies of CWC centers in the ascending branch of the Hadley and Walker Circulation, especially over the south and east of the TE The interannual variation of hydrometeors over the past decade showed a decrease over the southeastern and northwestern TP, along with a corresponding increase over other regions.展开更多
The effects of sea surface temperature（SST）,cloud radiative and microphysical processes,and diurnal variations on rainfall statistics are documented with grid data from the two-dimensional equilibrium cloud-resolvin...The effects of sea surface temperature（SST）,cloud radiative and microphysical processes,and diurnal variations on rainfall statistics are documented with grid data from the two-dimensional equilibrium cloud-resolving model simulations.For a rain rate of higher than 3 mm.h 1,water vapor convergence prevails.The rainfall amount decreases with the decrease of SST from 29℃ to 27℃,the inclusion of diurnal variation of SST,or the exclusion of microphysical effects of ice clouds and radiative effects of water clouds,which are primarily associated with the decreases in water vapor convergence.However,the amount of rainfall increases with the increase of SST from 29℃ to 31℃,the exclusion of diurnal variation of solar zenith angle,and the exclusion of the radiative effects of ice clouds,which are primarily related to increases in water vapor convergence.For a rain rate of less than 3 mm.h 1,water vapor divergence prevails.Unlike rainfall statistics for rain rates of higher than 3 mm.h 1,the decrease of SST from 29℃ to 27℃ and the exclusion of radiative effects of water clouds in the presence of radiative effects of ice clouds increase the rainfall amount,which corresponds to the suppression in water vapor divergence.The exclusion of microphysical effects of ice clouds decreases the amount of rainfall,which corresponds to the enhancement in water vapor divergence.The amount of rainfall is less sensitive to the increase of SST from 29℃ to 31℃ and to the radiative effects of water clouds in the absence of the radiative effects of ice clouds.展开更多
The objective of this work is to investigate experimentally controlling cavitating flow over NACA66(MOD)hydrofoils by means of an active water injection along its suction surface.The continuous water vertically jets o...The objective of this work is to investigate experimentally controlling cavitating flow over NACA66(MOD)hydrofoils by means of an active water injection along its suction surface.The continuous water vertically jets out of the chamber inside the hydrofoil through evenly distributed surface holes.Experiments were carried out in cavitation water tunnel.using high-speed visualization technology and the particle image velocimetry(PIV)system to study the sheetlcloud cavity behaviors.We studied the effects of this active control on cavity evolution with four kinds of jet flow at two different jet positions.We analyzed the effect of water injection on the mechanism of the cavitating flow control.The results were all compared with that for the original hydrofoil without jet and show that the active jet can effectively suppress the sheet/cloud cavitation characterized by shrinking the attached cavity size and breaking the large-scaled cloud sheding vortex cavity into small-scaled ones.The optimum effectiveness of cavitation suppression is affected by the jet flow rates and jet positions.The water injection at flow rate coefficient 0.0245 with the jet position of 0.45C reduces the maximum sheet cavity length by 79.4%and the cavity shedding is diminished completely,which gives the most superior effect of sheet cavitation suppression.The jet blocks the re-entrant jet moving upstream and weakens the power of re-entrant jet and thus restrains the cavitation development effectively and stabilizes the flow field.展开更多
ABSTRACT This paper reports airborne measurements of midlatitude altostratus clouds observed over Zhengzhou, Henan Province, China on 3 March 2007. The case demonstrates mixed-phase conditions at altitudes from 3200 ...ABSTRACT This paper reports airborne measurements of midlatitude altostratus clouds observed over Zhengzhou, Henan Province, China on 3 March 2007. The case demonstrates mixed-phase conditions at altitudes from 3200 to 4600 m （0°C to -7.6°C）, with liquid water content ranging from 0.01 to 0.09 g m-3. In the observed mixed-phase cloud, liquid water content exhibited a bimodal distribution, whereas the maximum ice particle concentration was located in the middle part of the cloud. The liquid and ice particle data showed significant horizontal variability on the scale of a few hundred meters. The cloud droplet concentration varied greatly over the horizontal sampling area. There was an inverse relationship between the cloud droplet concentration and ice particle concentration. A gamma distribution provided the best description of the cloud droplet spectra. The liquid droplet distributions were found to increase in both size and concentration with altitude. It was inferred from the profile of the spectra parameters that the cloud droplet sizes tend to form a quasi-monodisperse distribution. Ice particle spectra in the cloud were fitted well by an exponential distribution. Finally, a remarkable power law relationship was found between the slope （λ） and intercept （No） parameters of the exponential size distribution.展开更多
Cloud water plays an important role in the global atmospheric water cycle and weather modification,but cloud is one of the most uncertain parameters in the study of weather and climate.The cloud water products from di...Cloud water plays an important role in the global atmospheric water cycle and weather modification,but cloud is one of the most uncertain parameters in the study of weather and climate.The cloud water products from different data sources may have considerable discrepancies.In this study,the total cloud liquid water(termed as cloud liquid water path,LWP)obtained from satellite observations[Advanced Himawari Imager(AHI)and Advanced Microwave Scanning Radiometer(AMSR)]and three sets of modern reanalysis data(ERA5,JRA-55,and MERRA-2)are compared and analyzed.Moreover,characteristics of vertical distributions of cloud liquid water content(LWC)in different regions over East Asia are analyzed by using the profile data from the reanalyses.The main findings are as follows:(1)in extensive warm marine clouds,AHI and AMSR have a good agreement(with the correlation coefficient larger than 0.7)but with an overestimation from AHI;(2)under warm cloud conditions,the LWP in ERA5shows a significant positive bias(about 0.065 kg m^(-2))over land,while MERRA-2 is closer to the satellite product compared with ERA5 and JRA-55;and(3)Southwest China(SW)is the area with most abundant LWC.The LWC is mainly concentrated in the middle and lower troposphere in the study area,and the LWC in ERA5 is higher than that in MERRA-2 and JRA-55.Overall,satellite observations and reanalyses exhibit significant inconsistency for cloud LWP,which needs further investigation and understanding.展开更多
基金the National Natural Science Foundation of China(Nos.42176188,42176192)the Hainan Provincial Natural Science Foundation of China(No.421CXTD442)+2 种基金the Stable Supporting Fund of Acoustic Science and Technology Laboratory(No.JCKYS2024604SSJS007)the Fundamental Research Funds for the Central Universities(No.3072024CFJ0504)the Harbin Engineering University Doctoral Research and Innovation Fund(No.XK2050021034)。
文摘In the task of inspecting underwater suspended pipelines,multi-beam sonar(MBS)can provide two-dimensional water column images(WCIs).However,systematic interferences(e.g.,sidelobe effects)may induce misdetection in WCIs.To address this issue and improve the accuracy of detection,we developed a density-based clustering method for three-dimensional water column point clouds.During the processing of WCIs,sidelobe effects are mitigated using a bilateral filter and brightness transformation.The cross-sectional point cloud of the pipeline is then extracted by using the Canny operator.In the detection phase,the target is identified by using density-based spatial clustering of applications with noise(DBSCAN).However,the selection of appropriate DBSCAN parameters is obscured by the uneven distribution of the water column point cloud.To overcome this,we propose an improved DBSCAN based on a parameter interval estimation method(PIE-DBSCAN).First,kernel density estimation(KDE)is used to determine the candidate interval of parameters,after which the exact cluster number is determined via density peak clustering(DPC).Finally,the optimal parameters are selected by comparing the mean silhouette coefficients.To validate the performance of PIE-DBSCAN,we collected water column point clouds from an anechoic tank and the South China Sea.PIE-DBSCAN successfully detected both the target points of the suspended pipeline and non-target points on the seafloor surface.Compared to the K-Means and Mean-Shift algorithms,PIE-DBSCAN demonstrates superior clustering performance and shows feasibility in practical applications.
文摘The potential evapotranspiration of main ecosystems and its relationship with precipitation during the same period were studied,the results showed that precipitation did not meet the water requirement of main ecosystems influencing ecosystem construction.Based on the data from Liaoning Provincial Department of Water Resources and Liaoning Meteorological Archives,the characteristics of water inflow and each component were analyzed,and it showed that the imbalance between supply and demand of water resource in main ecosystems was improved by means of developing cloud water resource to increase atmospheric precipitation.
基金CAS/SAFEA International Partnership Program for Creative Research Teams, the Knowledge Innovation Program of Chinese Academy of Sciences （Project No. KZCX2-YW-202） National Basic Research Program of China （Grant No. 2006CB403600） +1 种基金 the National Natural Science Foundation of China（Grant Nos. 40437017, 40221503） ＂The Climate System Model Development and Application Studies＂ of International Partnership Creative Group program of Chinese Academy of Sciences, and the Key Sci. ＆ Tech. Supporting Project of the Ministry of Science and Technology of China（2006BAC12B03）.
文摘Analyses of cloud water path （CWP） data over China available from the International Satellite Cloud Climatology Project （ISCCP） are performed for the period 1984-2004. Combined with GPCP precipitation data, cloud water cycle index （CWCI） is also calculated. The climatic distributions of CWP are found to be dependent on large-scale circulation, topographical features, water vapor transport and similar distribution features which are found in CWCI except in the Sichuan Basin. Influenced by the Asia monsoon, CWP over China exhibits very large seasonal variations in different regions. The seasonal cycles of CWCI in different regions are consistent and the largest CWCI occurs in July. The long-term trends of CWP and CWCI are investigated, too. Increasing trends of CWP are found during the period with the largest increase found in winter. The decreasing trends of CWCI dominate most regions of China. The differences in long-term trends between CWP and CWCI suggest that CWP only can influence the variation of CWCI to a certain extent and that other factors need to be involved in cloud water cycle researches. This phenomenon reveals the complexity of the hydrological cycle related to cloud water.
基金This work was jointly supported by the 973 Project(Grant No.2005CB321703)the National Natural Science Foundation of China(Grant No.40221503)the Chinese Academy of Sciences International Partnership Creative Group entitled"The Climate System Model Development and Application Studies".
文摘This paper documents a study to examine the sensitivity to cloud droplet effective radius and liquid water path and the alleviation the energy imbalance at the top of the atmosphere and at the surface in the latest version of the Grid-point Atmospheric Model of the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics （LASG）, Institute of Atmospheric Physics （IAP） （GAMIL1.1.0）. Considerable negative biases in all flux components, and thus an energy imbalance, are found in GAMIL1.1.0. In order to alleviate the energy imbalance, two modifications, namely an increase in cloud droplet effective radius and a decrease in cloud liquid water path, have been made to the cloud properties used in GAMIL. With the increased cloud droplet effective radius, the single scattering albedo of clouds is reduced, and thus the reflection of solar radiation into space by clouds is reduced and the net solar radiation flux at the top of the atmosphere is increased. With the reduced cloud optical depth, the net surface shortwave radiation flux is increased, causing a net warming over the land surface. This results in an increase in both sensible and latent heat fluxes over the land regions, which is largely balanced by the increased terrestrial radiation fluxes. Consequently, the energy balance at the top of atmosphere and at the surface is achieved with energy flux components consistent with available satellite observations.
基金This work was supported by National Key Basic Research Development Program (G1999043400) and the National Natural Science Founda
文摘Based on relationships between cloud microphysical and optical properties, three different parameterization schemes for narrow and broad band optical properties in longwave region for water clouds have been presented. The effects of different parameterization schemes and different number of broad bands used on cloud radiative properties have been investigated. The effect of scattering role of cloud drops on longwave radiation fluxes and cooling rates in cloudy atmospheres has also been analyzed.
基金The National Key R&D Program of China under contract No.2018YFA0605904the Global Change Research Program of China under contract No.2015CB953900+1 种基金the Innovative Platform Program of Chinese Arctic and Antarctic Administration under contract No.CXPT2020009the Program of China Scholarships Council under contract No.201908320511.
文摘The role of Arctic clouds in the recent rapid Arctic warming has attracted much attention.However,Arctic cloud water paths(CWPs)from reanalysis datasets have not been well evaluated.This study evaluated the CWPs as well as LWPs(cloud liquid water paths)and IWPs(cloud ice water paths)from five reanalysis datasets(MERRA-2,MERRA,ERA-Interim,JRA-55,and ERA5)against the COSP(Cloud Feedback Model Intercomparison Project Observations Simulator Package)output for MODIS from the MERRA-2 CSP(COSP satellite simulator)collection(defined as M2Modis in short).Averaged over 1980-2015 and over the Arctic region(north of 60°N),the mean CWPs of these five datasets range from 49.5 g/m^(2)(MERRA)to 82.7 g/m^(2)(ERA-Interim),much smaller than that from M2Modis(140.0 g/m^(2)).However,the spatial distributions of CWPs,show similar patterns among these reanalyses,with relatively small values over Greenland and large values over the North Atlantic.Consistent with M2Modis,these reanalyses show larger LWPs than IWPs,except for ERA-Interim.However,MERRA-2 and MERRA underestimate the ratio of IWPs to CWPs over the entire Arctic,while ERA-Interim and JRA-55 overestimate this ratio.ERA5 shows the best performance in terms of the ratio of IWPs to CWPs.All datasets exhibit larger CWPs and LWPs in summer than in winter.For M2Modis,IWPs hold seasonal variation similar with LWPs over the land but opposite over the ocean.Following the Arctic warming,the trends in LWPs and IWPs during 1980~2015 show that LWPs increase and IWPs decrease across all datasets,although not statistically significant.Correlation analysis suggests that all datasets have similar interannual variability.The study further found that the inclusion of re-evaporation processes increases the humidity in the atmosphere over the land and that a more realistic liquid/ice phase can be obtained by independently treating the liquid and ice water contents.
基金National Key R&D Project of China(2018YFC1507001)。
文摘Tropical cyclone(TC) rainfall forecast has remained a challenge. To create initial conditions with high quality for simulation, the present study implemented a data assimilation scheme based on the EnKF method to ingest the satellite-retrieved cloud water path(C_(w)) and tested it in WRF. The scheme uses the vertical integration of forecasted cloud water content to transform control variables to the observation space, and creates the correlations between C_(w) and control variables in the flow-dependent background error covariance based on all the ensemble members, so that the observed cloud information can affect the background temperature and humidity. For two typhoons in 2018(Yagi and Rumiba), assimilating C_(w) significantly increases the simulated rainfalls and TC intensities. In terms of the average equitable threat score of daily moderate to heavy rainfall(5-120 mm), the improvements are over 130%, and the dry biases are cut by about 30%. Such improvements are traced down to the fact that C_(w) assimilation increases the moisture content, especially that further away from the TC center, which provides more precipitable water for the rainfall,strengthens the TC and broadens the TC size via latent heat release and internal wind field adjustment.
基金Project supported by the National Key Basic Research and Development Project of China (Grant No.2012CB417201)the National Natural Sciences Foundation of China (Grant Nos.40930950 41075043,41275065,and 41075044)the 985 Program of Zhejiang University (Grant No.188020+193432602/215)
文摘The effects of water and ice clouds on the cloud microphysical budget associated with rainfall are investigated through the analysis of grid-scale data from a series of two-dimensional cloud-resolving model equilibrium sensitivity simulations. The model is imposed without large-scale vertical velocity. In the control experiment, the contribution from rainfall （cM） associated with net evaporation and hydrometeor loss/convergence is about 29% of that from the rainfall （Cm） associated with net condensation and hydrometeor gain/divergence and about 39% of that from the rainfall （CM） associated with net condensation and hydrometeor loss/convergence. The exclusion of ice clouds enhances rainfall contribution of CM, whereas it reduces rainfall contributions of Cm and cM. The removal of radiative effects of water clouds increases rainfall contribution of CM, barely changes rainfall contribution of Cm and reduces the rainfall contribution of cM in the presence of the radiative effects of ice clouds. Elimination of the radiative effects of water clouds reduces the rainfall contributions of CM and Cm, whereas it increases the rainfall contribution of cM in the absence of the radiative effects of ice clouds.
文摘Cloud water samples, LWC （Liquid Water Content） and meteorological data were collected at the Clingmans Dome, Tennessee, high-elevation site in Great Smoky Mountains National Park during the warm season from 1994 through 2011. This paper presents results from 2000 through the conclusion of the study in 2011. Samples were analyzed for SO42＂, NO3, NH4＋ and H＋. These measurements were supplemented by measurements of ambient air and precipitation concentrations to estimate dry and wet deposition. Cloud water concentrations, LWC, cloud frequency, various meteorological measurements and information on nearby forest canopy were used to model cloud water deposition to gauge trends in deposition. Total deposition was calculated as the sum of cloud, dry and wet deposition estimates. Concentrations and deposition fluxes declined over the study period. The decreases in cloud water SO42＂ and NO3 concentrations were 40 percent and 26 percent, respectively. Three-year mean 5042 and NO3 deposition rates decreased by 71 percent and 70 percent, respectively. Trends in concentrations and depositions were comparable with trends in SO2 and NOx emissions from Tennessee Valley Authority power plants and aggregated emission reductions from electric generating units in adjacent states. Back trajectories were simulated with the HYSPLIT model and aggregated over cloud sampling periods from 2000 through 2007 and 2009 through 2011. Trajectories during periods with high H＋ concentrations traveled over local EGU （Electric Generating Unit） emission sources in Tennessee and Kentucky to the Ohio River Valley, Alabama and Georgia with the conclusion that these source regions contributed to acidic cloud water deposition at Clingmans Dome. This work was supported by U.S. Environmental Protection Agency and the Tennessee Valley Authority with infrastructure support provided by the National Park Service.
基金National Natural Science Foundation of China,Grant/Award Number:51779269。
文摘The Water Cloud Model(WCM)plays a crucial role in active microwave soil moisture inversion applications.Empirical parameters are important factors affecting the accuracy of WCM simulation,but the current evaluation of empirical parameters only considers the forward simulation process,and insufficient consideration is given to the model inversion problem.This study proposes a new estimation method for vegetation parameters in the WCM by combining the soil backscattering model and the objective function.The effectiveness of the method is then verified using measured data.Simultaneously,this study also analyzes the factors influencing the evaluation of vegetation parameters in the WCM,resulting in the following conclusions.First,blindly utilizing vegetation parameters recommended by previous model studies is not advisable.To ensure the accuracy of the simulation,it is necessary to adjust the vegetation parameters appropriately.Second,to ensure the ability of the WCM solving both forward and inverse problems,it is advisable to consider both soil backscatter and surface backscatter simulations in the construction of the cost function.Third,soil backscatter simulations have an impact on the solution of vegetation parameters,and more accurate soil scattering models provide a better representation of the modeled vegetation.This study presents a dependable method for resolving the vegetation parameters of the WCM,thereby offering a valuable reference for the application of the model in surface parameter inversion research.
基金funded by the Korea Meteorological Administration Research and Development Program“Research on Weather Modification and Cloud Physics”(Grant No.KMA2018-00224)supported by Korea Institute of Marine Science&Technology Promotion(KIMST)funded by the Ministry of Oceans and Fisheries,Korea(RS-202502217872)supported by an NRF grant funded by the Korean government(MSIT)(Grant No.NRF2023R1A2C1002367)。
文摘This study quantitatively analyzes the effects of cloud seeding on precipitation and seasonal variations over the Boryeong Dam region,which has the lowest dam storage in South Korea,based on a one-year numerical simulation for2021.The Morrison microphysics scheme in the WRF(Weather Research and Forecasting)model was modified to estimate differences in precipitation between simulations with seeding materials(Ag I and Ca Cl2;SEED)and without them(UNSD).The effect of cloud seeding on increasing precipitation or artificial rainfall(AR)between the two simulations was highest in August(average:0.21 mm;31%of the SEED-simulated monthly mean)and lowest in January(average:0.003 mm;30%).This large AR may be attributable to a combination of abundant moisture from the summer monsoon climate and enhanced cloud droplet growth resulting from cloud seeding.In the analysis of seasonal representative cases,cloud seeding demonstrated more pronounced effects in spring and summer,with mean 180-min accumulated AR values of 0.46 and 0.43 mm,respectively,within the study area.In the spring,where an actual flight experiment was conducted,the simulated mean180-min accumulated AR(1.41 mm)in the flight experiment area was close to the observed value(1.61 mm)for the same area.Additionally,cloud seeding promoted the hygroscopic growth of water vapor,thereby reducing the cloud water mixing ratio and increasing the rain water mixing ratio.Seasonal cross-sectional analysis further highlighted the impact of cloud seeding on changes in these two mixing ratios,with the most pronounced effects observed in spring and summer.
基金Supported by Henan Meteorological Science and Technology Research Project(Z200407)
文摘By using the microphysical data of stratiform cloud in Henan which were observed by PMS airborne cloud particle measure system on March 23 in 2007 and combining with the radar,satellite,sounding data,the macro and micro physical structure characteristics of cloud were analyzed.The results showed that the average diameter of small cloud drop which was measured by FSSP-100 in the warm layer of cloud was mainly during 5-12 μm,and the average value was 7.33 μm.The biggest diameter of small cloud drop changed during 14-47 μm,and the average value was 27.80 μm.The total number concentration scope of small cloud drop was during 47.73-352.00 drop/cm3,and the average value was 160 drop/cm3.In the cold layer of cloud,the biggest diameter of small cloud particle(included the cloud droplet and the ice crystals)which was measured by FSSP-100 was 24.8 μm.The total number concentration scope of small cloud particle was during 0.899-641.000 drop/cm3,and the average value was 297 drop/cm3.The airborne King heat line liquid water content instrument observed that the super-cooling liquid water existed in the cloud.The super-cooling cloud water content changed during 0.02-0.20 g/m3,and the average value was 0.093 g/m3.The biggest value which was 0.202 g/m3 appeared in 4 368 m height(the temperature was-8.5 ℃).The particle spectrum type in the cloud was mainly the negative exponent type and the single peak type.
基金supported by the National Key Basic Research Program of China(2013CBA01808)National Natural Science Foundation of China(Grant Nos.91437217,41275061,and 41440035)
文摘The characteristics of seasonal precipitation over the Tibetan Plateau （TP） were investigated using TRMM （Tropical Rain- fall Measuring Mission） precipitation data （3B43）. Sensitive regions of summer precipitation interannual variation anomalies were investigated using EOF （empirical orthogonal function） analysis. Furthermore, the profiles of cloud water content （CWC） and precipitable water in different regions and seasons were analyzed using TRMM-3A12 data observed by the TRMM Microwave Imager. Good agreement was found between hydrometeors and precipitation over the eastern and southeastern TP, where water vapor is adequate, while the water vapor amount is not significant over the western and northern TE Further analysis showed meridional and zonal anomalies of CWC centers in the ascending branch of the Hadley and Walker Circulation, especially over the south and east of the TE The interannual variation of hydrometeors over the past decade showed a decrease over the southeastern and northwestern TP, along with a corresponding increase over other regions.
基金Project supported by the National Basic Research Program of China (Grant No. 2012CB417201)the National Natural Science Foundation of China (Grant Nos. 41075034,40930950,40975034,and 41075044)
文摘The effects of sea surface temperature（SST）,cloud radiative and microphysical processes,and diurnal variations on rainfall statistics are documented with grid data from the two-dimensional equilibrium cloud-resolving model simulations.For a rain rate of higher than 3 mm.h 1,water vapor convergence prevails.The rainfall amount decreases with the decrease of SST from 29℃ to 27℃,the inclusion of diurnal variation of SST,or the exclusion of microphysical effects of ice clouds and radiative effects of water clouds,which are primarily associated with the decreases in water vapor convergence.However,the amount of rainfall increases with the increase of SST from 29℃ to 31℃,the exclusion of diurnal variation of solar zenith angle,and the exclusion of the radiative effects of ice clouds,which are primarily related to increases in water vapor convergence.For a rain rate of less than 3 mm.h 1,water vapor divergence prevails.Unlike rainfall statistics for rain rates of higher than 3 mm.h 1,the decrease of SST from 29℃ to 27℃ and the exclusion of radiative effects of water clouds in the presence of radiative effects of ice clouds increase the rainfall amount,which corresponds to the suppression in water vapor divergence.The exclusion of microphysical effects of ice clouds decreases the amount of rainfall,which corresponds to the enhancement in water vapor divergence.The amount of rainfall is less sensitive to the increase of SST from 29℃ to 31℃ and to the radiative effects of water clouds in the absence of the radiative effects of ice clouds.
基金the National NaturalScience Foundation of China(Grant 5l876022)the National BasicResearch Program of China(Grant 2015CB057301).
文摘The objective of this work is to investigate experimentally controlling cavitating flow over NACA66(MOD)hydrofoils by means of an active water injection along its suction surface.The continuous water vertically jets out of the chamber inside the hydrofoil through evenly distributed surface holes.Experiments were carried out in cavitation water tunnel.using high-speed visualization technology and the particle image velocimetry(PIV)system to study the sheetlcloud cavity behaviors.We studied the effects of this active control on cavity evolution with four kinds of jet flow at two different jet positions.We analyzed the effect of water injection on the mechanism of the cavitating flow control.The results were all compared with that for the original hydrofoil without jet and show that the active jet can effectively suppress the sheet/cloud cavitation characterized by shrinking the attached cavity size and breaking the large-scaled cloud sheding vortex cavity into small-scaled ones.The optimum effectiveness of cavitation suppression is affected by the jet flow rates and jet positions.The water injection at flow rate coefficient 0.0245 with the jet position of 0.45C reduces the maximum sheet cavity length by 79.4%and the cavity shedding is diminished completely,which gives the most superior effect of sheet cavitation suppression.The jet blocks the re-entrant jet moving upstream and weakens the power of re-entrant jet and thus restrains the cavitation development effectively and stabilizes the flow field.
基金supported by the National Natural Science Foundation of China (Grant No. 41175120)the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KZCX2-EW-203)
文摘ABSTRACT This paper reports airborne measurements of midlatitude altostratus clouds observed over Zhengzhou, Henan Province, China on 3 March 2007. The case demonstrates mixed-phase conditions at altitudes from 3200 to 4600 m （0°C to -7.6°C）, with liquid water content ranging from 0.01 to 0.09 g m-3. In the observed mixed-phase cloud, liquid water content exhibited a bimodal distribution, whereas the maximum ice particle concentration was located in the middle part of the cloud. The liquid and ice particle data showed significant horizontal variability on the scale of a few hundred meters. The cloud droplet concentration varied greatly over the horizontal sampling area. There was an inverse relationship between the cloud droplet concentration and ice particle concentration. A gamma distribution provided the best description of the cloud droplet spectra. The liquid droplet distributions were found to increase in both size and concentration with altitude. It was inferred from the profile of the spectra parameters that the cloud droplet sizes tend to form a quasi-monodisperse distribution. Ice particle spectra in the cloud were fitted well by an exponential distribution. Finally, a remarkable power law relationship was found between the slope （λ） and intercept （No） parameters of the exponential size distribution.
基金Supported by the National Natural Science Foundation of China(42205044)National Key Research and Development Program of China(2024YFF1308202)+2 种基金Fengyun Application Pioneer Project(FY-APP-2022.0111)Project for the Capacity Construction of Weather Modification in Southwest China[SCIT-ZG(Z)-2024100001]Wuxi University Research Start-up Fund for Introduced Talents(2024r045)。
文摘Cloud water plays an important role in the global atmospheric water cycle and weather modification,but cloud is one of the most uncertain parameters in the study of weather and climate.The cloud water products from different data sources may have considerable discrepancies.In this study,the total cloud liquid water(termed as cloud liquid water path,LWP)obtained from satellite observations[Advanced Himawari Imager(AHI)and Advanced Microwave Scanning Radiometer(AMSR)]and three sets of modern reanalysis data(ERA5,JRA-55,and MERRA-2)are compared and analyzed.Moreover,characteristics of vertical distributions of cloud liquid water content(LWC)in different regions over East Asia are analyzed by using the profile data from the reanalyses.The main findings are as follows:(1)in extensive warm marine clouds,AHI and AMSR have a good agreement(with the correlation coefficient larger than 0.7)but with an overestimation from AHI;(2)under warm cloud conditions,the LWP in ERA5shows a significant positive bias(about 0.065 kg m^(-2))over land,while MERRA-2 is closer to the satellite product compared with ERA5 and JRA-55;and(3)Southwest China(SW)is the area with most abundant LWC.The LWC is mainly concentrated in the middle and lower troposphere in the study area,and the LWC in ERA5 is higher than that in MERRA-2 and JRA-55.Overall,satellite observations and reanalyses exhibit significant inconsistency for cloud LWP,which needs further investigation and understanding.
