Based on satellite data and the estimated inversion strength(EIS) derived by Wood et al.(2006), a feasible and uncomplicated stratocumulus scheme is proposed, referred to as EIS scheme. It improves simulation of cloud...Based on satellite data and the estimated inversion strength(EIS) derived by Wood et al.(2006), a feasible and uncomplicated stratocumulus scheme is proposed, referred to as EIS scheme. It improves simulation of cloud radiative forcing(CRF) in the Grid-point Atmospheric Model of IAP/LASG version 2(GAMIL2.0) model. When compared with the original lower troposphere stability(LTS) scheme, the EIS scheme reproduces more reasonable climatology distributions of clouds and CRF. The parameterization partly corrects CRF underestimation at mid and high latitudes and overestimation in the convective region. Such improvements are achieved by neglecting the effect of free-tropospheric stratification changes that follow a cooler moist adiabat at middle and high latitude, thereby improving simulated cloudiness. The EIS scheme also improves simulation of the CRF interannual variability. The positive net CRF and negative stratiform anomaly in the East Asian and western North Pacific monsoon regions(EAWNPMR) are well simulated. The EIS scheme is more sensitive to sea surface temperature anomalies(SSTA) than the LTS. Therefore, under the effect of a warmer SSTA in the EAWNPMR, the EIS generates a stronger negative stratiform response, which reduces radiative heating in the low and mid troposphere, in turn producing strong subsidence and negative anomalies of both moisture and cloudiness. Consequent decreases in cloud reflection and shading effects ultimately improve simulation of incoming surface shortwave radiative fluxes and CRF. Because of the stronger subsidence, a stronger anomalous anticyclone over the Philippines Sea is simulated by the EIS run, which leads to a better positive precipitation anomaly in eastern China during ENSO winter.展开更多
By using the cloud echoes fi rst successfully observed by China’s indigenous 94-GHz SKY cloud radar, the macrostructure and microphysical properties of drizzling stratocumulus clouds in Anhui Province on 8 June 2013 ...By using the cloud echoes fi rst successfully observed by China’s indigenous 94-GHz SKY cloud radar, the macrostructure and microphysical properties of drizzling stratocumulus clouds in Anhui Province on 8 June 2013 are analyzed, and the detection capability of this cloud radar is discussed. The results are as follows. （1） The cloud radar is able to observe the time-varying macroscopic and microphysical parameters of clouds, and it can reveal the microscopic structure and small-scale changes of clouds. （2） The velocity spectral width of cloud droplets is small, but the spectral width of the cloud containing both cloud droplets and drizzle is large. When the spectral width is more than 0.4 m s-1, the radar refl ectivity factor is larger （over-10 dBZ）. （3） The radar’s sensitivity is comparatively higher because the minimum radar refl ectivity factor is about-35 dBZ in this experiment, which exceeds the threshold for detecting the linear depolarized ratio （LDR） of stratocumulus （commonly -11 to -14 dBZ; decreases with increasing turbulence）. （4） After distinguishing of cloud droplets from drizzle, cloud liquid water content and particle eff ective radius are retrieved. The liquid water content of drizzle is lower than that of cloud droplets at the same radar refl ectivity factor.展开更多
Biases in shortwave cloud radiative forcing(SWCF), which cause overestimates in tropical regions and underestimates in subtropical marine stratocumulus regions, are common in many climate models. Here, two boundary la...Biases in shortwave cloud radiative forcing(SWCF), which cause overestimates in tropical regions and underestimates in subtropical marine stratocumulus regions, are common in many climate models. Here, two boundary layer processes are investigated in the atmospheric model GAMIL2, entrainment at the top of the boundary layer and longwave radiative cooling at the top of stratocumulus clouds, in order to reduce biases and reveal the mechanisms underlying these processes. Our results show that including the entrainment process in the model can reduce negative SWCF biases in most tropical regions but increases positive SWCF biases in subtropical marine stratocumulus regions. This occurs because entrainment reduces the low-level cloud fraction and its cloud liquid water content by suppressing the vertical turbulent diffusion in the boundary layer and decreasing the relative humidity when warm and dry free atmosphere is entrained in the boundary layer. Longwave radiative cooling at the top of stratocumulus clouds can enhance turbulent diffusion within the stratocumulus-topped boundary layer. When combined with the entrainment process, longwave radiative cooling reduces the positive SWCF biases in subtropical marine stratocumulus regions that are observed using the entrainment process alone. The incorporation of these two boundary layer processes improves the simulated SWCF in tropical and subtropical regions in GAMIL2.展开更多
A one-dimensional 3rd-order turbulence closure model with size-resolved microphysics and radiative transfer has been developed for investigating aerosol and cloud interactions of the stratocumulus-topped marine bounda...A one-dimensional 3rd-order turbulence closure model with size-resolved microphysics and radiative transfer has been developed for investigating aerosol and cloud interactions of the stratocumulus-topped marine boundary layer. A new method is presented for coupling between the dynamical model and the microphysical model. This scheme allows the liquid water related correlations to be directly calculated rather than parameterized. On 21 April 2001, a marine stratocumulus was observed by the Caesar aircraft over the west Pacific Rim south of Japan during the 2001 APEX/ACE-Asia field measurements. This cloud is simulated by the model we present here. The model results show that the general features of the stratocumulus-topped marine boundary layer predicted by the model are in agreement with the measurements. A new onboard cloud condensation nuclei (CCN) counter provides not only total CCN number concentration (as the traditional CCN counters do at a certain supersaturation) but also the CCN size distribution information. Using these CCN data, model responses to different CCN initial concentrations are examined. The model results are consistent with both observations and expectations. The numerical results show that the cloud microphysical properties are changed fundamentally by different initial CCN concentrations but the cloud liquid water content does not differ significantly. Different initial CCN loadings have large impacts on the evolution of cloud microstructure and radiation transfer while they have a modest effect on thermodynamics. Increased CCN concentration leads to significant decrease of cloud effective radius.展开更多
This study explores the microphysical responses to a cloud seeding operation in the Sanjiangyuan region, China. The cloud seeding was performed using a zigzag flight pattern, while the detection phase was accomplished...This study explores the microphysical responses to a cloud seeding operation in the Sanjiangyuan region, China. The cloud seeding was performed using a zigzag flight pattern, while the detection phase was accomplished using a back-and-forth flight pattern through the top of a stratocumulus layer. Global Position System（GPS） and Particle Measuring System（PMS） data obtained during the operation are used to determine the efective cloud area before and after the operation, diferentiate the phase states of cloud particles, and analyze changes in the concentrations of liquid cloud particles and ice crystals, the evolution of the cloud particle spectrum, and the content of supercooled water. The median diameter of liquid cloud particles in the area of the cloud-seeding operation was 3.5–18.5 μm, most cloud particles observed in the 21.5–45.5-μm size regime were ice crystals, while all particles of size 50 μm and above were in the ice phase. Changes in the concentration and typical diameter of cloud particles within 36 km downwind of the cloudseeding operation did not exceed natural fluctuations in the cloud area before the operation; however, the concentration of liquid cloud particles decreased substantially in areas with high concentrations of supercooled water（concentrations of supercooled water exceeding 0.01 g m 3）. The concentration of ice crystals within the measuring range of the Forward Scattering Spectrometer Probe（FSSP） increased substantially, the water content of ice-phase particles increased, and the average supercooled water content in the cloud decreased from（68.3± 23.1）% before the operation to（34.2± 12.4）%. The efects of cloud seeding were more pronounced in parts of the cloud where the content of supercooled water was higher. Little to no efects were observed in parts of the cloud with low concentrations of supercooled water.展开更多
气候预测系统的海洋初始化积分试验考虑了海气相互作用,可以视为一种弱耦合同化试验。海温(SST)和层积云的关系是检验海气相互作用过程模拟效果的重要参考。分析了基于耦合气候系统模式FGOALS-s2的中国科学院大气物理研究所近期气候预...气候预测系统的海洋初始化积分试验考虑了海气相互作用,可以视为一种弱耦合同化试验。海温(SST)和层积云的关系是检验海气相互作用过程模拟效果的重要参考。分析了基于耦合气候系统模式FGOALS-s2的中国科学院大气物理研究所近期气候预测系统IAP Dec Pre S的海洋初始化模拟实验(简称EnOI-IAU试验)所模拟的海温—云关系。结果表明,EnOI-IAU试验较好地模拟出了SST和低云的气候态空间分布,但在主要层积云区低估了低云云量和云水,SST模拟偏高,特别在副热带东大洋沿岸和南大洋。部分原因是这些地区实际影响海表温度模拟的是模式的内部过程,而低云模拟不足导致了海表入射更多的短波辐射(强度约偏强20 W/m^2),迫使局地SST模拟过高。分析显示,低云模拟不足主要是由于EnOI-IAU试验不能再现合理的边界层逆温结构,表现为大气垂直速度、温度和湿度过于集中在近地层,使得边界层垂直热输送较弱、边界层无法充分混合,进而无法有效模拟出层积云。这些结果表明,未来引入大气观测数据同化,特别是改善边界层结构的模拟,对形成完整的耦合同化系统具有必要性。展开更多
The effect of a vertical diffusion scheme over a stratocumulus topped boundary layer （STBL） was investigated using the YONU AGCM （Yonsei University Atmospheric General Circulation Model）. To consider the impact of...The effect of a vertical diffusion scheme over a stratocumulus topped boundary layer （STBL） was investigated using the YONU AGCM （Yonsei University Atmospheric General Circulation Model）. To consider the impact of clouds on the turbulence production, the turbulence mixing term, driven by radiative cooling at the cloud top, is implemented as an extended non-local diffusion scheme. In the model with this new scheme, the STBL parameterization significantly influences the lower atmosphere over the tropical and subtropical regions. Consideration of the turbulent mixing within the cloud layer leads to continuous stratocumulus formation. The cloud-top radiative cooling tends to favor more rapid entrainment and produces top-down turbulent mixing. This cooling develops a mixed layer without initiation of deep convection by surface fluxes. Variations in thermodynamical and dynamical features are produced by planetary boundary layer （PBL） cloud development. The simulated stratocumulus induces more mixing of heat and moisture due to the cloud forcing. Over STBL regions, the lower boundary layer becomes warmer and drier. It also weakens vertical motion and zonal trade winds in the eastern Pacific, which indicates that stratocumulus cloud cover plays a role in weakening the Walker circulation; that is, cloud cover damps the tropical circulation.展开更多
中南半岛地区生物物质燃烧活动使其成为东南亚烟雾气溶胶的高值区,排放的烟雾可以传播到南海海域,影响当地层积云的微观特性和降水活动,进而对气候产生影响。本文利用2007—2019年CALIPSO和CloudSat卫星数据筛选了190个烟雾气溶胶与层...中南半岛地区生物物质燃烧活动使其成为东南亚烟雾气溶胶的高值区,排放的烟雾可以传播到南海海域,影响当地层积云的微观特性和降水活动,进而对气候产生影响。本文利用2007—2019年CALIPSO和CloudSat卫星数据筛选了190个烟雾气溶胶与层积云混合的个例,其中中南半岛等陆地上空(代表陆地)的烟雾混合层积云为88个,南海海域(代表海洋)的烟雾混合层积云为102个。基于个例的研究发现:相对于海洋上的烟雾混合层积云,陆地上的烟雾混合层积云中云的液态粒子数浓度(Number concentration of liquid water drops,LNC)、液态粒子有效半径(Geometric mean radius of liquid water drops,LER)和液态水含量(Liquid water content,LWC)的值都更高。与清洁层积云相比,烟雾气溶胶主要通过半直接效应影响海洋上的层积云,而主要作为云凝结核(Cloud condensation nuclei,CCN)通过间接效应影响陆地上的层积云。当气溶胶光学厚度(Aerosol optical depth,AOD)≤0.6时,海洋上烟雾混合层积云内Twomey效应发挥主导作用,而陆地上烟雾混合层积云内反Twomey效应发挥主导作用;当AOD处于0.6~1.2时,烟雾混合层积云的半直接效应发挥主导作用。本文的研究对中南半岛和南海海域的气溶胶与云的相互作用机制有重要参考意义,并为改进模式结果提供理论支持。展开更多
This paper presents a method to distinguish and link inhomogeneous mixing with subsequent ascent and collision-coalescence. Three stratocumulus clouds analyzed were collected over the U.S. Department of Energy's A...This paper presents a method to distinguish and link inhomogeneous mixing with subsequent ascent and collision-coalescence. Three stratocumulus clouds analyzed were collected over the U.S. Department of Energy's Atmospheric Radiation Measurement Southern Great Plains site during the March 2000 cloud Intensive Observation Period. The criteria are presented to distinguish the two processes. Inhomogeneous mixing with subsequent ascent is identified if cloud along an aircraft horizontal leg is non-drizzling and the relationship between cloud volume-mean radius and liquid water content is negative; in contrast, drizzling and positive relationship between the above two properties are the criteria for collision-coalescence. To link the two processes, threshold function, the possibility of occurrence of collision-coalescence, is employed; the big droplets generated during the in-homogeneous mixing with subsequent ascent increase the threshold function, initiates collision-coalescence and produces drizzle drops. To the authors' knowledge, this is the first study on distinguishing and linking inhomogeneous mixing with subsequent ascent and collision-coalescence based on observational data.展开更多
On the basis of the conceptual model,the development of wintertime stratocumulus cloud has been sim- ulated by using a planetary boundary layer/cloud physics model.The main characteristics of the cloud struc- ture and...On the basis of the conceptual model,the development of wintertime stratocumulus cloud has been sim- ulated by using a planetary boundary layer/cloud physics model.The main characteristics of the cloud struc- ture and evolution obtained from the simulation are consistent with those from observations.By analyzing the modeled results,some details of the cloud structures and microphysics processes are discussed.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.41125017)the National Basic Research Program of China(Grant No.2010CB951904)
文摘Based on satellite data and the estimated inversion strength(EIS) derived by Wood et al.(2006), a feasible and uncomplicated stratocumulus scheme is proposed, referred to as EIS scheme. It improves simulation of cloud radiative forcing(CRF) in the Grid-point Atmospheric Model of IAP/LASG version 2(GAMIL2.0) model. When compared with the original lower troposphere stability(LTS) scheme, the EIS scheme reproduces more reasonable climatology distributions of clouds and CRF. The parameterization partly corrects CRF underestimation at mid and high latitudes and overestimation in the convective region. Such improvements are achieved by neglecting the effect of free-tropospheric stratification changes that follow a cooler moist adiabat at middle and high latitude, thereby improving simulated cloudiness. The EIS scheme also improves simulation of the CRF interannual variability. The positive net CRF and negative stratiform anomaly in the East Asian and western North Pacific monsoon regions(EAWNPMR) are well simulated. The EIS scheme is more sensitive to sea surface temperature anomalies(SSTA) than the LTS. Therefore, under the effect of a warmer SSTA in the EAWNPMR, the EIS generates a stronger negative stratiform response, which reduces radiative heating in the low and mid troposphere, in turn producing strong subsidence and negative anomalies of both moisture and cloudiness. Consequent decreases in cloud reflection and shading effects ultimately improve simulation of incoming surface shortwave radiative fluxes and CRF. Because of the stronger subsidence, a stronger anomalous anticyclone over the Philippines Sea is simulated by the EIS run, which leads to a better positive precipitation anomaly in eastern China during ENSO winter.
基金Supported by China Meteorological Administration Special Public Welfare Research Fund(GYHY201206038,GYHY200906053,and GYHY201306040)National(Key)Basic Research and Development(973)Program of China(2013CB430102)+8 种基金National High Technology Research and Development Program(863)of China(2007AA061901)Natural Science Foundation of the Jiangsu Higher Education Institutions of China(10KJA170030)State Key Laboratory Program(2013LASW-B16)Nanjing Weather Radar Open Laboratory Research Fund(BJG201208)Key Technology Projects of China Meteorological Bureau(CMAGJ2014M21)Young Scientists Fund of the Natural Science Foundation of Jiangsu Province(BK2012466)Postgraduate Science and Technology Innovation Project of Jiangsu Province(CXZZ13-0513)Non-Profit Industry Fund by Ministry of Science and Technology of China and Ministry of Water Resources(201201063)Young Scientists Fund of the National Natural Science Foundation of China(41305031)
文摘By using the cloud echoes fi rst successfully observed by China’s indigenous 94-GHz SKY cloud radar, the macrostructure and microphysical properties of drizzling stratocumulus clouds in Anhui Province on 8 June 2013 are analyzed, and the detection capability of this cloud radar is discussed. The results are as follows. （1） The cloud radar is able to observe the time-varying macroscopic and microphysical parameters of clouds, and it can reveal the microscopic structure and small-scale changes of clouds. （2） The velocity spectral width of cloud droplets is small, but the spectral width of the cloud containing both cloud droplets and drizzle is large. When the spectral width is more than 0.4 m s-1, the radar refl ectivity factor is larger （over-10 dBZ）. （3） The radar’s sensitivity is comparatively higher because the minimum radar refl ectivity factor is about-35 dBZ in this experiment, which exceeds the threshold for detecting the linear depolarized ratio （LDR） of stratocumulus （commonly -11 to -14 dBZ; decreases with increasing turbulence）. （4） After distinguishing of cloud droplets from drizzle, cloud liquid water content and particle eff ective radius are retrieved. The liquid water content of drizzle is lower than that of cloud droplets at the same radar refl ectivity factor.
基金supported by the CAS Strategic Priority Research Program (Grant No. XDA05110304)the National Basic Research Program of China (Grant No. 2015CB954102)the National Natural Science Foundation of China (Grant Nos. 41205079 & 41305040)
文摘Biases in shortwave cloud radiative forcing(SWCF), which cause overestimates in tropical regions and underestimates in subtropical marine stratocumulus regions, are common in many climate models. Here, two boundary layer processes are investigated in the atmospheric model GAMIL2, entrainment at the top of the boundary layer and longwave radiative cooling at the top of stratocumulus clouds, in order to reduce biases and reveal the mechanisms underlying these processes. Our results show that including the entrainment process in the model can reduce negative SWCF biases in most tropical regions but increases positive SWCF biases in subtropical marine stratocumulus regions. This occurs because entrainment reduces the low-level cloud fraction and its cloud liquid water content by suppressing the vertical turbulent diffusion in the boundary layer and decreasing the relative humidity when warm and dry free atmosphere is entrained in the boundary layer. Longwave radiative cooling at the top of stratocumulus clouds can enhance turbulent diffusion within the stratocumulus-topped boundary layer. When combined with the entrainment process, longwave radiative cooling reduces the positive SWCF biases in subtropical marine stratocumulus regions that are observed using the entrainment process alone. The incorporation of these two boundary layer processes improves the simulated SWCF in tropical and subtropical regions in GAMIL2.
基金supported by the National Natural Science Foundation of China(NSFC)under Grant No.40005001 and the key laboratory of storm and disaster of Educational Department of China
文摘A one-dimensional 3rd-order turbulence closure model with size-resolved microphysics and radiative transfer has been developed for investigating aerosol and cloud interactions of the stratocumulus-topped marine boundary layer. A new method is presented for coupling between the dynamical model and the microphysical model. This scheme allows the liquid water related correlations to be directly calculated rather than parameterized. On 21 April 2001, a marine stratocumulus was observed by the Caesar aircraft over the west Pacific Rim south of Japan during the 2001 APEX/ACE-Asia field measurements. This cloud is simulated by the model we present here. The model results show that the general features of the stratocumulus-topped marine boundary layer predicted by the model are in agreement with the measurements. A new onboard cloud condensation nuclei (CCN) counter provides not only total CCN number concentration (as the traditional CCN counters do at a certain supersaturation) but also the CCN size distribution information. Using these CCN data, model responses to different CCN initial concentrations are examined. The model results are consistent with both observations and expectations. The numerical results show that the cloud microphysical properties are changed fundamentally by different initial CCN concentrations but the cloud liquid water content does not differ significantly. Different initial CCN loadings have large impacts on the evolution of cloud microstructure and radiation transfer while they have a modest effect on thermodynamics. Increased CCN concentration leads to significant decrease of cloud effective radius.
基金Supported by the Research Fund of the Doctoral Program of Higher Education of China (20113228110002)Priority Academic Program Development (PAPD) of Jiangsu Higher Education InstitutionsChina Meteorological Administration Special Pwblic Welfare Research Fund (GYHY200906024)
文摘This study explores the microphysical responses to a cloud seeding operation in the Sanjiangyuan region, China. The cloud seeding was performed using a zigzag flight pattern, while the detection phase was accomplished using a back-and-forth flight pattern through the top of a stratocumulus layer. Global Position System（GPS） and Particle Measuring System（PMS） data obtained during the operation are used to determine the efective cloud area before and after the operation, diferentiate the phase states of cloud particles, and analyze changes in the concentrations of liquid cloud particles and ice crystals, the evolution of the cloud particle spectrum, and the content of supercooled water. The median diameter of liquid cloud particles in the area of the cloud-seeding operation was 3.5–18.5 μm, most cloud particles observed in the 21.5–45.5-μm size regime were ice crystals, while all particles of size 50 μm and above were in the ice phase. Changes in the concentration and typical diameter of cloud particles within 36 km downwind of the cloudseeding operation did not exceed natural fluctuations in the cloud area before the operation; however, the concentration of liquid cloud particles decreased substantially in areas with high concentrations of supercooled water（concentrations of supercooled water exceeding 0.01 g m 3）. The concentration of ice crystals within the measuring range of the Forward Scattering Spectrometer Probe（FSSP） increased substantially, the water content of ice-phase particles increased, and the average supercooled water content in the cloud decreased from（68.3± 23.1）% before the operation to（34.2± 12.4）%. The efects of cloud seeding were more pronounced in parts of the cloud where the content of supercooled water was higher. Little to no efects were observed in parts of the cloud with low concentrations of supercooled water.
文摘气候预测系统的海洋初始化积分试验考虑了海气相互作用,可以视为一种弱耦合同化试验。海温(SST)和层积云的关系是检验海气相互作用过程模拟效果的重要参考。分析了基于耦合气候系统模式FGOALS-s2的中国科学院大气物理研究所近期气候预测系统IAP Dec Pre S的海洋初始化模拟实验(简称EnOI-IAU试验)所模拟的海温—云关系。结果表明,EnOI-IAU试验较好地模拟出了SST和低云的气候态空间分布,但在主要层积云区低估了低云云量和云水,SST模拟偏高,特别在副热带东大洋沿岸和南大洋。部分原因是这些地区实际影响海表温度模拟的是模式的内部过程,而低云模拟不足导致了海表入射更多的短波辐射(强度约偏强20 W/m^2),迫使局地SST模拟过高。分析显示,低云模拟不足主要是由于EnOI-IAU试验不能再现合理的边界层逆温结构,表现为大气垂直速度、温度和湿度过于集中在近地层,使得边界层垂直热输送较弱、边界层无法充分混合,进而无法有效模拟出层积云。这些结果表明,未来引入大气观测数据同化,特别是改善边界层结构的模拟,对形成完整的耦合同化系统具有必要性。
基金supported by Ministry of Environment of Korea as "The Eco-technopia 21 Project"supported by Pusan National University under the "Post-Doc. 2008 Program"
文摘The effect of a vertical diffusion scheme over a stratocumulus topped boundary layer （STBL） was investigated using the YONU AGCM （Yonsei University Atmospheric General Circulation Model）. To consider the impact of clouds on the turbulence production, the turbulence mixing term, driven by radiative cooling at the cloud top, is implemented as an extended non-local diffusion scheme. In the model with this new scheme, the STBL parameterization significantly influences the lower atmosphere over the tropical and subtropical regions. Consideration of the turbulent mixing within the cloud layer leads to continuous stratocumulus formation. The cloud-top radiative cooling tends to favor more rapid entrainment and produces top-down turbulent mixing. This cooling develops a mixed layer without initiation of deep convection by surface fluxes. Variations in thermodynamical and dynamical features are produced by planetary boundary layer （PBL） cloud development. The simulated stratocumulus induces more mixing of heat and moisture due to the cloud forcing. Over STBL regions, the lower boundary layer becomes warmer and drier. It also weakens vertical motion and zonal trade winds in the eastern Pacific, which indicates that stratocumulus cloud cover plays a role in weakening the Walker circulation; that is, cloud cover damps the tropical circulation.
文摘中南半岛地区生物物质燃烧活动使其成为东南亚烟雾气溶胶的高值区,排放的烟雾可以传播到南海海域,影响当地层积云的微观特性和降水活动,进而对气候产生影响。本文利用2007—2019年CALIPSO和CloudSat卫星数据筛选了190个烟雾气溶胶与层积云混合的个例,其中中南半岛等陆地上空(代表陆地)的烟雾混合层积云为88个,南海海域(代表海洋)的烟雾混合层积云为102个。基于个例的研究发现:相对于海洋上的烟雾混合层积云,陆地上的烟雾混合层积云中云的液态粒子数浓度(Number concentration of liquid water drops,LNC)、液态粒子有效半径(Geometric mean radius of liquid water drops,LER)和液态水含量(Liquid water content,LWC)的值都更高。与清洁层积云相比,烟雾气溶胶主要通过半直接效应影响海洋上的层积云,而主要作为云凝结核(Cloud condensation nuclei,CCN)通过间接效应影响陆地上的层积云。当气溶胶光学厚度(Aerosol optical depth,AOD)≤0.6时,海洋上烟雾混合层积云内Twomey效应发挥主导作用,而陆地上烟雾混合层积云内反Twomey效应发挥主导作用;当AOD处于0.6~1.2时,烟雾混合层积云的半直接效应发挥主导作用。本文的研究对中南半岛和南海海域的气溶胶与云的相互作用机制有重要参考意义,并为改进模式结果提供理论支持。
基金LIU and Lu was supported by the U.S. Department of Energy (DOE) Earth System Modeling (ESM) Program via the FASTER Project (www.bnl.gov/esm)and At-mospheric System Research (ASR) ProgramNiu was supported by the Qing-Lan Project for Cloud-Fog-Precipitation-Aerosol Study in Jiangsu Province, Chinaa Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘This paper presents a method to distinguish and link inhomogeneous mixing with subsequent ascent and collision-coalescence. Three stratocumulus clouds analyzed were collected over the U.S. Department of Energy's Atmospheric Radiation Measurement Southern Great Plains site during the March 2000 cloud Intensive Observation Period. The criteria are presented to distinguish the two processes. Inhomogeneous mixing with subsequent ascent is identified if cloud along an aircraft horizontal leg is non-drizzling and the relationship between cloud volume-mean radius and liquid water content is negative; in contrast, drizzling and positive relationship between the above two properties are the criteria for collision-coalescence. To link the two processes, threshold function, the possibility of occurrence of collision-coalescence, is employed; the big droplets generated during the in-homogeneous mixing with subsequent ascent increase the threshold function, initiates collision-coalescence and produces drizzle drops. To the authors' knowledge, this is the first study on distinguishing and linking inhomogeneous mixing with subsequent ascent and collision-coalescence based on observational data.
文摘On the basis of the conceptual model,the development of wintertime stratocumulus cloud has been sim- ulated by using a planetary boundary layer/cloud physics model.The main characteristics of the cloud struc- ture and evolution obtained from the simulation are consistent with those from observations.By analyzing the modeled results,some details of the cloud structures and microphysics processes are discussed.
