Cloud base height(CBH) is a crucial parameter for cloud radiative effect estimates, climate change simulations, and aviation guidance. However, due to the limited information on cloud vertical structures included in p...Cloud base height(CBH) is a crucial parameter for cloud radiative effect estimates, climate change simulations, and aviation guidance. However, due to the limited information on cloud vertical structures included in passive satellite radiometer observations, few operational satellite CBH products are currently available. This study presents a new method for retrieving CBH from satellite radiometers. The method first uses the combined measurements of satellite radiometers and ground-based cloud radars to develop a lookup table(LUT) of effective cloud water content(ECWC), representing the vertically varying cloud water content. This LUT allows for the conversion of cloud water path to cloud geometric thickness(CGT), enabling the estimation of CBH as the difference between cloud top height and CGT. Detailed comparative analysis of CBH estimates from the state-of-the-art ECWC LUT are conducted against four ground-based millimeter-wave cloud radar(MMCR) measurements, and results show that the mean bias(correlation coefficient) is0.18±1.79 km(0.73), which is lower(higher) than 0.23±2.11 km(0.67) as derived from the combined measurements of satellite radiometers and satellite radar-lidar(i.e., Cloud Sat and CALIPSO). Furthermore, the percentages of the CBH biases within 250 m increase by 5% to 10%, which varies by location. This indicates that the CBH estimates from our algorithm are more consistent with ground-based MMCR measurements. Therefore, this algorithm shows great potential for further improvement of the CBH retrievals as ground-based MMCR are being increasingly included in global surface meteorological observing networks, and the improved CBH retrievals will contribute to better cloud radiative effect estimates.展开更多
Based on ground-based Atmospheric Emitted Radiance Interferometer (AERI) observations in Shouxian, Anhui province, China, the authors retrieve the cloud base height (CBH) and effective cloud emissivity by using the mi...Based on ground-based Atmospheric Emitted Radiance Interferometer (AERI) observations in Shouxian, Anhui province, China, the authors retrieve the cloud base height (CBH) and effective cloud emissivity by using the minimum root-mean-square difference method. This method was originally developed for satellite remote sensing. The high-temporal-resolution retrieval results can depict the trivial variations of the zenith clouds continu-ously. The retrieval results are evaluated by comparing them with observations by the cloud radar. The comparison shows that the retrieval bias is smaller for the middle and low cloud, especially for the opaque cloud. When two layers of clouds exist, the retrieval results reflect the weighting radiative contribution of the multi-layer cloud. The retrieval accuracy is affected by uncertainties of the AERI radiances and sounding profiles, in which the role of uncertainty in the temperature profile is dominant.展开更多
Cloud vertical structure(CVS)strongly affects atmospheric circulation and radiative transfer.Yet,long-term,groundbased observations are scarce over the Tibetan Plateau(TP)despite its vital role in global climate.This ...Cloud vertical structure(CVS)strongly affects atmospheric circulation and radiative transfer.Yet,long-term,groundbased observations are scarce over the Tibetan Plateau(TP)despite its vital role in global climate.This study utilizes ground-based lidar and Ka-band cloud profiling radar(KaCR)measurements at Yangbajain(YBJ),TP,from October 2021 to September 2022 to characterize cloud properties.A satisfactorily performing novel anomaly detection algorithm(LevelShiftAD)is proposed for lidar and KaCR profiles to identify cloud boundaries.Cloud base heights(CBH)retrieved from KaCR and lidar observations show good consistency,with a correlation coefficient of 0.78 and a mean difference of-0.06 km.Cloud top heights(CTH)derived from KaCR match the FengYun-4A and Himawari-8 products well.Thus,KaCR measurements serve as the primary dataset for investigating CVSs over the TP.Different diurnal cycles occur in summer and winter.The diurnal cycle is characterized by a pronounced increase in cloud occurrence frequency in the afternoon with an early-morning decrease in winter,while cloud amounts remain high all day,with scattered nocturnal increases in summer.Summer features more frequent clouds with larger geometrical thicknesses,a higher multi-layer ratio,and greater inter-cloud spacing.Around 26%of the cloud bases occur below 0.5 km.Winter exhibits a bimodal distribution of cloud base heights with peaks at 0-0.5 km and 2-2.5 km.Single-layer and geometrically thin clouds prevail at YBJ.This study enriches long-term measurements of CVSs over the TP,and the robust anomaly detection method helps quantify cloud macro-physical properties via synergistic lidar and radar observations.展开更多
Clouds are critical to the global radiation budget and hydrological cycle, but knowledge is still poor concerning the observed climatology of cloud-base height （CBH） in China. Based on fine-resolution sounding obser...Clouds are critical to the global radiation budget and hydrological cycle, but knowledge is still poor concerning the observed climatology of cloud-base height （CBH） in China. Based on fine-resolution sounding observations from the China Radiosonde Network （CRN）, the method used to estimate CBH was modified, and uncertainty analyses indicated that the CBH is good enough. The accuracy of CBH estimation is verified by the comparison between the sounding-derived CBHs and those estimated from the micro-pulse lidar and millimeter-wave cloud radar. As such, the CBH climatology was compiled for the period 2006-16. Overall, the CBH exhibits large geographic variability across China, at both 0800 Local Standard Time （LST） and 2000 LST, irrespective of season. In addition, the summertime cloud base tends to be elevated to higher altitudes in dry regions [i.e., Inner Mongolia and the North China Plain （NCP）]. By comparison, the Tibetan Plateau （TP）, Pearl River Delta （PRD） and Sichuan Basin （SCB） have relatively low CBHs （〈 2.4 km above ground level）. In terms of seasonality, the CBH reaches its maximum in summer and minimum in winter. A low cloud base tends to occur frequently （〉 70%） over the TP, PRD and SCB. In contrast, at most sites over the Yangtze River Delta （YRD） and the NCP, about half the cloud belongs to the high-cloud category. The CBH does not exhibit marked diurnal variation in summer, throughout all CRN sites, probably due to the persistent cloud coverage caused by the East Asia Summer Monsson. To the best of our knowledge, this is the first CBH climatology produced from sounding measurements in China, and provides a useful reference for obtaining observational cloud base information.展开更多
The electrification of vehicle helps to improve its operation efficiency and safety.Due to fast development of network,sensors,as well as computing technology,it becomes realizable to have vehicles driving autonomousl...The electrification of vehicle helps to improve its operation efficiency and safety.Due to fast development of network,sensors,as well as computing technology,it becomes realizable to have vehicles driving autonomously.To achieve autonomous driving,several steps,including environment perception,path-planning,and dynamic control,need to be done.However,vehicles equipped with on-board sensors still have limitations in acquiring necessary environmental data for optimal driving decisions.Intelligent and connected vehicles(ICV)cloud control system(CCS)has been introduced as a new concept as it is a potentially synthetic solution for high level automated driving to improve safety and optimize traffic flow in intelligent transportation.This paper systematically investigated the concept of cloud control system from cloud related applications on ICVs,and cloud control system architecture design,as well as its core technologies development.Based on the analysis,the challenges and suggestions on cloud control system development have been addressed.展开更多
The satellite-based quantification of cloud radiative forcing remains poorly understood,due largely to the limitation or uncertainties in characterizing cloud-base height(CBH).Here,we use the CBH data from radiosonde ...The satellite-based quantification of cloud radiative forcing remains poorly understood,due largely to the limitation or uncertainties in characterizing cloud-base height(CBH).Here,we use the CBH data from radiosonde measurements over China in combination with the collocated cloud-top height(CTH) and cloud properties from MODIS/Aqua to quantify the impact of CBH on shortwave cloud radiative forcing(SWCRF).The climatological mean SWCRF at the surface(SWCRFSUR),at the top of the atmosphere(SWCRFTOA),and in the atmosphere(SWCRFATM) are estimated to be-97.14,-84.35,and 12.79 W m^(-2),respectively for the summers spanning 2010 to 2018 over China.To illustrate the role of the cloud base,we assume four scenarios according to vertical profile patterns of cloud optical depth(COD).Using the CTH and cloud properties from MODIS alone results in large uncertainties for the estimation of SWCRFATM,compared with those under scenarios that consider the CBH.Furthermore,the biases of the CERES estimation of SWCRFATM tend to increase in the presence of thick clouds with low CBH.Additionally,the discrepancy of SWCRFATM relative to that calculated without consideration of CBH varies according to the vertical profile of COD.When a uniform COD vertical profile is assumed,the largest SWCRF discrepancies occur during the early morning or late afternoon.By comparison,the two-point COD vertical distribution assumption has the largest uncertainties occurring at noon when the solar irradiation peaks.These findings justify the urgent need to consider the cloud vertical structures when calculating the SWCRF which is otherwise neglected.展开更多
In this study,cloud base height（CBH） and cloud top height（CTH） observed by the Ka-band（33.44 GHz） cloud radar at the Boseong National Center for Intensive Observation of Severe Weather during fall 2013（Septembe...In this study,cloud base height（CBH） and cloud top height（CTH） observed by the Ka-band（33.44 GHz） cloud radar at the Boseong National Center for Intensive Observation of Severe Weather during fall 2013（September-November） were verified and corrected.For comparative verification,CBH and CTH were obtained using a ceilometer（CL51） and the Communication,Ocean and Meteorological Satellite（COMS）.During rainfall,the CBH and CTH observed by the cloud radar were lower than observed by the ceilometer and COMS because of signal attenuation due to raindrops,and this difference increased with rainfall intensity.During dry periods,however,the CBH and CTH observed by the cloud radar,ceilometer,and COMS were similar.Thin and low-density clouds were observed more effectively by the cloud radar compared with the ceilometer and COMS.In cases of rainfall or missing cloud radar data,the ceilometer and COMS data were proven effective in correcting or compensating the cloud radar data.These corrected cloud data were used to classify cloud types,which revealed that low clouds occurred most frequently.展开更多
Cloud radiative kernels(CRK)built with radiative transfer models have been widely used to analyze the cloud radiative effect on top of atmosphere(TOA)fluxes,and it is expected that the CRKs would also be useful in the...Cloud radiative kernels(CRK)built with radiative transfer models have been widely used to analyze the cloud radiative effect on top of atmosphere(TOA)fluxes,and it is expected that the CRKs would also be useful in the analyses of surface radiative fluxes,which determines the regional surface temperature change and variability.In this study,CRKs at the surface and TOA were built using the Rapid Radiative Transfer Model(RRTM).Longwave cloud radiative effect(CRE)at the surface is primarily driven by cloud base properties,while TOA CRE is primarily decided by cloud top properties.For this reason,the standard version of surface CRK is a function of latitude,longitude,month,cloud optical thickness(τ)and cloud base pressure(CBP),and the TOA CRK is a function of latitude,longitude,month,τand cloud top pressure(CTP).Considering that the cloud property histograms provided by climate models are functions of CTP instead of CBP at present,the surface CRKs on CBP-τhistograms were converted to CTP-τfields using the statistical relationship between CTP,CBP andτobtained from collocated CloudSat and MODIS observations.For both climate model outputs and satellites observations,the climatology of surface CRE and cloud-induced surface radiative anomalies calculated with the surface CRKs and cloud property histograms are well correlated with those calculated from surface radiative fluxes.The cloud-induced surface radiative anomalies reproduced by surface CRKs and MODIS cloud property histograms are not affected by spurious trends that appear in Clouds and the Earth's Radiant Energy System(CERES)surface irradiances products.展开更多
Cloud computing is one of the fastest growing and popular computer technologies, and there are more and more enterprise services based on the cloud computing. In order to save costs, more and more enterprises and thei...Cloud computing is one of the fastest growing and popular computer technologies, and there are more and more enterprise services based on the cloud computing. In order to save costs, more and more enterprises and their employees have hired the enterprise cloud services, and put much important information in the cloud gradually. Cloud service systems have become the main targets of malicious attacks. However, the cloud computing technologies are still not perfect, and the management and maintenance of enterprise cloud services are more complex compared to traditional network services of cloud computing. So, enterprise cloud services are more likely to encounter some security problems, and the influenced scale of these security problems is broad. But there are few researches on the security of enterprise cloud services. In this paper, we analyze the software as a service（Saa S） enterprise cloud services and introduce the research status of security problems in cloud computing environment. Combining with the analysis of the characteristics and application architecture of Saa S enterprise cloud services, we propose the security problems analysis model, the analysis system architecture and the relational model. Our researches can support further research of the automatic generation of solutions and guide the deployment of security policies of Saa S enterprise cloud services.展开更多
The Internet of Everything(IoE)based cloud computing is one of the most prominent areas in the digital big data world.This approach allows efficient infrastructure to store and access big real-time data and smart IoE ...The Internet of Everything(IoE)based cloud computing is one of the most prominent areas in the digital big data world.This approach allows efficient infrastructure to store and access big real-time data and smart IoE services from the cloud.The IoE-based cloud computing services are located at remote locations without the control of the data owner.The data owners mostly depend on the untrusted Cloud Service Provider(CSP)and do not know the implemented security capabilities.The lack of knowledge about security capabilities and control over data raises several security issues.Deoxyribonucleic Acid(DNA)computing is a biological concept that can improve the security of IoE big data.The IoE big data security scheme consists of the Station-to-Station Key Agreement Protocol(StS KAP)and Feistel cipher algorithms.This paper proposed a DNA-based cryptographic scheme and access control model(DNACDS)to solve IoE big data security and access issues.The experimental results illustrated that DNACDS performs better than other DNA-based security schemes.The theoretical security analysis of the DNACDS shows better resistance capabilities.展开更多
In the paper, we propose a new method of identifying the clear sky based on the Atmospheric Emitted Radiance Interferometer （AERI）. Using the Atmospheric Radiation Measurement （ARM） Mobile Facility （AFM） dataset...In the paper, we propose a new method of identifying the clear sky based on the Atmospheric Emitted Radiance Interferometer （AERI）. Using the Atmospheric Radiation Measurement （ARM） Mobile Facility （AFM） dataset in Shouxian in 2008, we sim- ulate the downwelling radiances on the surface in the 8-12 μm window region using Line-By-Line Radiative Transfer Model （LBLRTM）, and compare the results with the AERI radiances, The differences larger （smaller） than 3 mW （cm2 sr cm-1）-1 suggest a cloudy （clear） sky. Meanwhile, we develop the new algorithms for retrieving the zenith equivalent cloud base height （CBHe） and the equivalent emissivity （ee）, respectively. The retrieval methods are described as follows. （1） An infinitely thin and isothermal blackbody cloud is simulated by the LBLRTM. The cloud base height （H） is adjusted iteratively to satisfy the situation that the contribution of the blackbody to the downwelling radiance is equal to that of realistic cloud. The final H is considered as CBHe. The retrieval results indicate that the differences between the CBHe and observational cloud base height （CBH） are much smaller for thick low cloud, and increase with the increasing CBH. （2） An infinitely thin and isothermal gray body cloud is simulated by the LBLRTM, with the CBH specified as the observed value. The cloud base emissivity （co） is ad- justed iteratively until the contribution of the gray body to the downwelling radiance is the same as that of realistic cloud. The corresponding εc is εe. The average εe for the low, middle, and high cloud is 0.967, 0.781, and 0.616 for the 50 cases, respec- tively. It decreases with the increasing CBH. The retrieval results will be useful for studying the role of cloud in the radiation budget in the window region and cloud parameterizations in the climate model.展开更多
基金funded by the National Natural Science Foundation of China (Grant Nos. 42305150 and 42325501)the China Postdoctoral Science Foundation (Grant No. 2023M741774)。
文摘Cloud base height(CBH) is a crucial parameter for cloud radiative effect estimates, climate change simulations, and aviation guidance. However, due to the limited information on cloud vertical structures included in passive satellite radiometer observations, few operational satellite CBH products are currently available. This study presents a new method for retrieving CBH from satellite radiometers. The method first uses the combined measurements of satellite radiometers and ground-based cloud radars to develop a lookup table(LUT) of effective cloud water content(ECWC), representing the vertically varying cloud water content. This LUT allows for the conversion of cloud water path to cloud geometric thickness(CGT), enabling the estimation of CBH as the difference between cloud top height and CGT. Detailed comparative analysis of CBH estimates from the state-of-the-art ECWC LUT are conducted against four ground-based millimeter-wave cloud radar(MMCR) measurements, and results show that the mean bias(correlation coefficient) is0.18±1.79 km(0.73), which is lower(higher) than 0.23±2.11 km(0.67) as derived from the combined measurements of satellite radiometers and satellite radar-lidar(i.e., Cloud Sat and CALIPSO). Furthermore, the percentages of the CBH biases within 250 m increase by 5% to 10%, which varies by location. This indicates that the CBH estimates from our algorithm are more consistent with ground-based MMCR measurements. Therefore, this algorithm shows great potential for further improvement of the CBH retrievals as ground-based MMCR are being increasingly included in global surface meteorological observing networks, and the improved CBH retrievals will contribute to better cloud radiative effect estimates.
基金supported by the National Natural Science Foundation of China (Grant No. 40710059003)
文摘Based on ground-based Atmospheric Emitted Radiance Interferometer (AERI) observations in Shouxian, Anhui province, China, the authors retrieve the cloud base height (CBH) and effective cloud emissivity by using the minimum root-mean-square difference method. This method was originally developed for satellite remote sensing. The high-temporal-resolution retrieval results can depict the trivial variations of the zenith clouds continu-ously. The retrieval results are evaluated by comparing them with observations by the cloud radar. The comparison shows that the retrieval bias is smaller for the middle and low cloud, especially for the opaque cloud. When two layers of clouds exist, the retrieval results reflect the weighting radiative contribution of the multi-layer cloud. The retrieval accuracy is affected by uncertainties of the AERI radiances and sounding profiles, in which the role of uncertainty in the temperature profile is dominant.
基金jointly funded by the Second Tibetan Plateau Scientific Expedition and Research Program of China under Grant 2019QZKK0604the National Natural Science Foundation of China(Grant Nos.92044303 and 42001294).
文摘Cloud vertical structure(CVS)strongly affects atmospheric circulation and radiative transfer.Yet,long-term,groundbased observations are scarce over the Tibetan Plateau(TP)despite its vital role in global climate.This study utilizes ground-based lidar and Ka-band cloud profiling radar(KaCR)measurements at Yangbajain(YBJ),TP,from October 2021 to September 2022 to characterize cloud properties.A satisfactorily performing novel anomaly detection algorithm(LevelShiftAD)is proposed for lidar and KaCR profiles to identify cloud boundaries.Cloud base heights(CBH)retrieved from KaCR and lidar observations show good consistency,with a correlation coefficient of 0.78 and a mean difference of-0.06 km.Cloud top heights(CTH)derived from KaCR match the FengYun-4A and Himawari-8 products well.Thus,KaCR measurements serve as the primary dataset for investigating CVSs over the TP.Different diurnal cycles occur in summer and winter.The diurnal cycle is characterized by a pronounced increase in cloud occurrence frequency in the afternoon with an early-morning decrease in winter,while cloud amounts remain high all day,with scattered nocturnal increases in summer.Summer features more frequent clouds with larger geometrical thicknesses,a higher multi-layer ratio,and greater inter-cloud spacing.Around 26%of the cloud bases occur below 0.5 km.Winter exhibits a bimodal distribution of cloud base heights with peaks at 0-0.5 km and 2-2.5 km.Single-layer and geometrically thin clouds prevail at YBJ.This study enriches long-term measurements of CVSs over the TP,and the robust anomaly detection method helps quantify cloud macro-physical properties via synergistic lidar and radar observations.
基金the Ministry of Science and Technology of China (Grant Nos. 2017YFC1501701, 2017YFC1501401, 2017YFA0603501 and 2016YFA0600403)the National Natural Science Foundation of China (Grant Nos. 91544217, 41771399 and 41471301)+1 种基金the Chinese Academy of Meteorological Sciences (Grant Nos. 2017Z005 and 2017R001)the Fundamental Research Funds for the Central Universities (Grant No. 2017STUD17)
文摘Clouds are critical to the global radiation budget and hydrological cycle, but knowledge is still poor concerning the observed climatology of cloud-base height （CBH） in China. Based on fine-resolution sounding observations from the China Radiosonde Network （CRN）, the method used to estimate CBH was modified, and uncertainty analyses indicated that the CBH is good enough. The accuracy of CBH estimation is verified by the comparison between the sounding-derived CBHs and those estimated from the micro-pulse lidar and millimeter-wave cloud radar. As such, the CBH climatology was compiled for the period 2006-16. Overall, the CBH exhibits large geographic variability across China, at both 0800 Local Standard Time （LST） and 2000 LST, irrespective of season. In addition, the summertime cloud base tends to be elevated to higher altitudes in dry regions [i.e., Inner Mongolia and the North China Plain （NCP）]. By comparison, the Tibetan Plateau （TP）, Pearl River Delta （PRD） and Sichuan Basin （SCB） have relatively low CBHs （〈 2.4 km above ground level）. In terms of seasonality, the CBH reaches its maximum in summer and minimum in winter. A low cloud base tends to occur frequently （〉 70%） over the TP, PRD and SCB. In contrast, at most sites over the Yangtze River Delta （YRD） and the NCP, about half the cloud belongs to the high-cloud category. The CBH does not exhibit marked diurnal variation in summer, throughout all CRN sites, probably due to the persistent cloud coverage caused by the East Asia Summer Monsson. To the best of our knowledge, this is the first CBH climatology produced from sounding measurements in China, and provides a useful reference for obtaining observational cloud base information.
基金Supported by Beijing Nova Program of Science and Technology(Grant No.Z191100001119087)Beijing Municipal Science&Technology Commission(Grant No.Z181100004618005 and Grant No.Z18111000460000)。
文摘The electrification of vehicle helps to improve its operation efficiency and safety.Due to fast development of network,sensors,as well as computing technology,it becomes realizable to have vehicles driving autonomously.To achieve autonomous driving,several steps,including environment perception,path-planning,and dynamic control,need to be done.However,vehicles equipped with on-board sensors still have limitations in acquiring necessary environmental data for optimal driving decisions.Intelligent and connected vehicles(ICV)cloud control system(CCS)has been introduced as a new concept as it is a potentially synthetic solution for high level automated driving to improve safety and optimize traffic flow in intelligent transportation.This paper systematically investigated the concept of cloud control system from cloud related applications on ICVs,and cloud control system architecture design,as well as its core technologies development.Based on the analysis,the challenges and suggestions on cloud control system development have been addressed.
基金support from the National Key R&D Program of China under Grants Nos.2017YFC1501401 and 2017YFC0212803the National Natural Science Foundation under Grant No.41771399the Chinese Academy of Meteorological Sciences under Grant No.2018Y014。
文摘The satellite-based quantification of cloud radiative forcing remains poorly understood,due largely to the limitation or uncertainties in characterizing cloud-base height(CBH).Here,we use the CBH data from radiosonde measurements over China in combination with the collocated cloud-top height(CTH) and cloud properties from MODIS/Aqua to quantify the impact of CBH on shortwave cloud radiative forcing(SWCRF).The climatological mean SWCRF at the surface(SWCRFSUR),at the top of the atmosphere(SWCRFTOA),and in the atmosphere(SWCRFATM) are estimated to be-97.14,-84.35,and 12.79 W m^(-2),respectively for the summers spanning 2010 to 2018 over China.To illustrate the role of the cloud base,we assume four scenarios according to vertical profile patterns of cloud optical depth(COD).Using the CTH and cloud properties from MODIS alone results in large uncertainties for the estimation of SWCRFATM,compared with those under scenarios that consider the CBH.Furthermore,the biases of the CERES estimation of SWCRFATM tend to increase in the presence of thick clouds with low CBH.Additionally,the discrepancy of SWCRFATM relative to that calculated without consideration of CBH varies according to the vertical profile of COD.When a uniform COD vertical profile is assumed,the largest SWCRF discrepancies occur during the early morning or late afternoon.By comparison,the two-point COD vertical distribution assumption has the largest uncertainties occurring at noon when the solar irradiation peaks.These findings justify the urgent need to consider the cloud vertical structures when calculating the SWCRF which is otherwise neglected.
基金supported by the principal project, “Development and application of technology for weather forecasting (NIMR-2012-B-1)” of the National Institute of Meteorological Sciences of the Korea Meteorological Administration
文摘In this study,cloud base height（CBH） and cloud top height（CTH） observed by the Ka-band（33.44 GHz） cloud radar at the Boseong National Center for Intensive Observation of Severe Weather during fall 2013（September-November） were verified and corrected.For comparative verification,CBH and CTH were obtained using a ceilometer（CL51） and the Communication,Ocean and Meteorological Satellite（COMS）.During rainfall,the CBH and CTH observed by the cloud radar were lower than observed by the ceilometer and COMS because of signal attenuation due to raindrops,and this difference increased with rainfall intensity.During dry periods,however,the CBH and CTH observed by the cloud radar,ceilometer,and COMS were similar.Thin and low-density clouds were observed more effectively by the cloud radar compared with the ceilometer and COMS.In cases of rainfall or missing cloud radar data,the ceilometer and COMS data were proven effective in correcting or compensating the cloud radar data.These corrected cloud data were used to classify cloud types,which revealed that low clouds occurred most frequently.
基金supported by the National Natural Science Foundation of China(Grant No.NSFC 41875095,42075127).
文摘Cloud radiative kernels(CRK)built with radiative transfer models have been widely used to analyze the cloud radiative effect on top of atmosphere(TOA)fluxes,and it is expected that the CRKs would also be useful in the analyses of surface radiative fluxes,which determines the regional surface temperature change and variability.In this study,CRKs at the surface and TOA were built using the Rapid Radiative Transfer Model(RRTM).Longwave cloud radiative effect(CRE)at the surface is primarily driven by cloud base properties,while TOA CRE is primarily decided by cloud top properties.For this reason,the standard version of surface CRK is a function of latitude,longitude,month,cloud optical thickness(τ)and cloud base pressure(CBP),and the TOA CRK is a function of latitude,longitude,month,τand cloud top pressure(CTP).Considering that the cloud property histograms provided by climate models are functions of CTP instead of CBP at present,the surface CRKs on CBP-τhistograms were converted to CTP-τfields using the statistical relationship between CTP,CBP andτobtained from collocated CloudSat and MODIS observations.For both climate model outputs and satellites observations,the climatology of surface CRE and cloud-induced surface radiative anomalies calculated with the surface CRKs and cloud property histograms are well correlated with those calculated from surface radiative fluxes.The cloud-induced surface radiative anomalies reproduced by surface CRKs and MODIS cloud property histograms are not affected by spurious trends that appear in Clouds and the Earth's Radiant Energy System(CERES)surface irradiances products.
基金supported by National Natural Science Foundation of China(Nos.61300049,61502197 and 61503044)the Specialized Research Fund for the Doctoral Program of Higher Education of China(No.20120061120059)+2 种基金the China Postdoctoral Science Foundation(No.2011M500612)the Key Program for Science and Technology Development of Jilin Province of China(No.20130206052GX)the Natural Science Research Foundation of Jilin Province of China(Nos.20140520069JH,20150101054JC and 20150520058JH)
文摘Cloud computing is one of the fastest growing and popular computer technologies, and there are more and more enterprise services based on the cloud computing. In order to save costs, more and more enterprises and their employees have hired the enterprise cloud services, and put much important information in the cloud gradually. Cloud service systems have become the main targets of malicious attacks. However, the cloud computing technologies are still not perfect, and the management and maintenance of enterprise cloud services are more complex compared to traditional network services of cloud computing. So, enterprise cloud services are more likely to encounter some security problems, and the influenced scale of these security problems is broad. But there are few researches on the security of enterprise cloud services. In this paper, we analyze the software as a service（Saa S） enterprise cloud services and introduce the research status of security problems in cloud computing environment. Combining with the analysis of the characteristics and application architecture of Saa S enterprise cloud services, we propose the security problems analysis model, the analysis system architecture and the relational model. Our researches can support further research of the automatic generation of solutions and guide the deployment of security policies of Saa S enterprise cloud services.
文摘The Internet of Everything(IoE)based cloud computing is one of the most prominent areas in the digital big data world.This approach allows efficient infrastructure to store and access big real-time data and smart IoE services from the cloud.The IoE-based cloud computing services are located at remote locations without the control of the data owner.The data owners mostly depend on the untrusted Cloud Service Provider(CSP)and do not know the implemented security capabilities.The lack of knowledge about security capabilities and control over data raises several security issues.Deoxyribonucleic Acid(DNA)computing is a biological concept that can improve the security of IoE big data.The IoE big data security scheme consists of the Station-to-Station Key Agreement Protocol(StS KAP)and Feistel cipher algorithms.This paper proposed a DNA-based cryptographic scheme and access control model(DNACDS)to solve IoE big data security and access issues.The experimental results illustrated that DNACDS performs better than other DNA-based security schemes.The theoretical security analysis of the DNACDS shows better resistance capabilities.
基金supported by the Chinese Academy of Sciences (Grant No. XDA05040300)National Natural Science Foundation of China (Grant No. 40710059003)
文摘In the paper, we propose a new method of identifying the clear sky based on the Atmospheric Emitted Radiance Interferometer （AERI）. Using the Atmospheric Radiation Measurement （ARM） Mobile Facility （AFM） dataset in Shouxian in 2008, we sim- ulate the downwelling radiances on the surface in the 8-12 μm window region using Line-By-Line Radiative Transfer Model （LBLRTM）, and compare the results with the AERI radiances, The differences larger （smaller） than 3 mW （cm2 sr cm-1）-1 suggest a cloudy （clear） sky. Meanwhile, we develop the new algorithms for retrieving the zenith equivalent cloud base height （CBHe） and the equivalent emissivity （ee）, respectively. The retrieval methods are described as follows. （1） An infinitely thin and isothermal blackbody cloud is simulated by the LBLRTM. The cloud base height （H） is adjusted iteratively to satisfy the situation that the contribution of the blackbody to the downwelling radiance is equal to that of realistic cloud. The final H is considered as CBHe. The retrieval results indicate that the differences between the CBHe and observational cloud base height （CBH） are much smaller for thick low cloud, and increase with the increasing CBH. （2） An infinitely thin and isothermal gray body cloud is simulated by the LBLRTM, with the CBH specified as the observed value. The cloud base emissivity （co） is ad- justed iteratively until the contribution of the gray body to the downwelling radiance is the same as that of realistic cloud. The corresponding εc is εe. The average εe for the low, middle, and high cloud is 0.967, 0.781, and 0.616 for the 50 cases, respec- tively. It decreases with the increasing CBH. The retrieval results will be useful for studying the role of cloud in the radiation budget in the window region and cloud parameterizations in the climate model.
