Data-driven Estimation of Cloud Effects on Surface Irradiance at Xianghe,a Suburban Site on the North China Plain

Clouds are a dominant modulator of the energy budget.The cloud shortwave radiative effect at the surface(CRE)is closely related to the cloud macro-and micro-physical properties.Systematic observation of surface irradiance and cloud properties are needed to narrow uncertainties in CRE.In this study,1-min irradiance and Total Sky Imager measurements from 2005 to 2009 at Xianghe in North China Plain are used to estimate cloud types,evaluate cloud fraction(CF),and quantify the sensitivities of surface irradiance with respect to changes in CF whether clouds obscure the sun or not.The annual mean CF is 0.50,further noting that CF exhibits a distinct seasonal variation,with a minimum in winter(0.37)and maximum in summer(0.68).Cumulus occurs more frequently in summer(32%),which is close to the sum of the occurrence of stratus and cirrus.The annual CRE is–54.4 W m^(–2),with seasonal values ranging from^(–2)9.5 W m^(–2)in winter and–78.2 W m^(–2)in summer.When clouds do not obscure the sun,CF is a dominant factor affecting diffuse irradiance,which in turn affects global irradiance.There is a positive linear relationship between CF and CRE under sun-unobscured conditions,the mean sensitivity of CRE for each CF 0.1 increase is about 1.2 W m^(–2)[79.5°<SZA(Solar Zenith Angle)<80.5°]to 7.0 W m^(–2)(29.5°<SZA<30.5°).When clouds obscure the sun,CF affects both direct and diffuse irradiance,resulting in a non-linear relationship between CF and CRE,and the slope decreases with increasing CF.It should be noted that,although only data at Xianghe is used in this study,our results are representative of neighboring areas,including most parts of the North China Plain.

Analytical treatment of the nonlinear electron cloud effect and the combined effects with beam-beam and space charge nonlinear forces in storage rings

In this paper we treat first some nonlinear beam dynamics problems in storage rings, such as beam dynamic apertures due to magnetic multipoles, wiggles, beam-beam effects, nonlinear space charge effect, and then nonlinear electron cloud effect combined with beam-beam and space charge effects, analytically. This analytical treatment is applied to BEPC II. The corresponding analytical expressions developed in this paper are useful both in understanding the physics behind these problems and also in making practical quick hand estimations.

Sensitivity of the Grid-point Atmospheric Model of IAP LASG(GAMILI.I.0)Climate Simulations to Cloud Droplet Effective Radius and Liquid Water Path

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.

An Evaluation of the Effects of Cloud Parameterization in the R42L9 GCM

Cloud is one of the uncertainty factors influencing the performance of a general circulation model (GCM). Recently, the State Key Laboratory of Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics (LASG/IAP) has developed a new version of a GCM (R42L9). In this work, roles of cloud parameterization in the R42L9 are evaluated through a comparison between two 20-year simulations using different cloud schemes. One scheme is that the cloud in the model is diagnosed from relative humidity and vertical velocity, and the other one is that diagnostic cloud is replaced by retrieved cloud amount from the International Satellite Cloud Climatology Project (ISCCP), combined with the amounts of high-, middle-, and low-cloud and heights of the cloud base and top from the NCEP. The boreal winter and summer seasonal means, as well as the annual mean, of the simulated top-of-atmosphere shortwave radiative flux, surface energy fluxes, and precipitation are analyzed in comparison with the observational estimates and NCEP reanalysis data. The results show that the scheme of diagnostic cloud parameterization greatly contributes to model biases of radiative budget and precipitation. When our derived cloud fractions are used to replace the diagnostic cloud amount, the top-of-atmosphere and surface radiation fields are better estimated as well as the spatial pattern of precipitation. The simulations of the regional precipitation, especially over the equatorial Indian Ocean in winter and the Asia-western Pacific region in summer, are obviously improved.

An Evidence of Aerosol Indirect Effect on Stratus Clouds from the Integrated Ground-Based Measurements at the ARM Shouxian Site

The aerosol effect on clouds was explored using remote sensing of aerosol and cloud data at Shouxian, China. Non-precipitation, ice-free, and overcast clouds were firstly chosen by a combination of sky images from the Total Sky Imager (TSI), cloud base heights from the Ceilometer, and vertical temperature profiles from the Balloon-Borne Sounding System (BBSS). Six cases were chosen in summer, and seven in autumn. The averaged cloud effective radii (re), cloud optical depth (COD), aerosol total light scattering coefficient (σ), and liquid water path (LWP) are, respectivey, 6.47 μm, 35.4, 595.9 mm-1, 0.19 mm in summer, and 6.07 μm, 96.0, 471.7 mm-1, 0.37 mm in autumn. The correlation coefficient between re and σ was found to change from negative to positive value as LWP increases.

A Comprehensive Observational Analysis for the Effects of Gas Cannons on Clouds and Precipitation

To analyze the effects of gas cannons on clouds and precipitation,multisource observational data,including those from National Centers for Environmental Prediction(NCEP)reanalysis,Hangzhou and Huzhou new-generation weather radars,laser disdrometer,ground-based automatic weather station,wind profiler radar,and Lin'an C-band dualpolarization radar,were adopted in this study.Based on the variational dual-Doppler wind retrieval method and the polarimetric variables obtained by the dual-polarization radar,we analyzed the microphysical processes and the variations in the macro-and microphysical quantities in clouds from the perspective of the synoptic background before precipitation enhancement,the polarization echo characteristics before,during and after enhancement,and the evolution of the fine three-dimensional kinematic structure and the microphysical structure.The results show that the precipitation enhancement operation promoted the development of radar echoes and prolonged their duration,and both the horizontal and vertical wind speeds increased.The dual-polarization radar echo showed that the diameter of the precipitation particles increased,and the concentration of raindrops increased after precipitation enhancement.The raindrops were lifted to a height corresponding to 0 to-20℃due to vertical updrafts.Based on the disdrometer data during precipitation enhancement,the concentration of small raindrops(lgN_(w))showed a significant increase,and the mass-weighted diameter D_(m)value decreased,indicating that the precipitation enhancement operation played a certain“lubricating”effect.After the precipitation enhancement,the concentration of raindrops did not change much compared with that during the enhancement process,while the Dm increased,corresponding to an increase in rain intensity.The results suggest the positive effect of gas cannons on precipitation enhancement.

A Preliminary Evaluation of Global and East Asian Cloud Radiative Effects in Reanalyses

Cloud radiative effects(CREs) at the top of the atmosphere(TOA) in three reanalysis datasets(the European Center for Medium-Range Weather Forecasts Interim Reanalysis(ERA-Interim), the Japanese 55-yr Reanalysis Project(JRA-55), and the Modern-Era Retrospective Analysis for Research and Applications(MERRA)) are evaluated using recent satellite-based observations. The reanalyses can basically capture the spatial pattern of the annual mean shortwave CRE, but the global mean longwave CRE in ERA-Interim and JRA55 is weaker than observed, leading to overestimations of the net CRE. Moreover, distinct CRE biases of the reanalyses occur in the Intertropical Convergence Zone(ITCZ), coastal Pacific and Atlantic regions, and East Asia. Quantitative examination further indicates that the spatial correlations of CREs and TOA upward radiation fluxes with corresponding observations in ERA-Interim are better than in the other two reanalyses. Although MERRA has certain abilities in producing the magnitudes of global mean CREs, its performance in terms of spatial correlations in winter and summer are worse than for the other two reanalyses. The ability of JRA55 in reflecting CREs lies between the other two datasets. Compared to the global mean results, the spatial correlations of shortwave CRE in East Asia decrease and the biases of regional mean CREs increase in the three reanalyses. This implies that, currently, it is still difficult to reproduce East Asian CREs based on these reanalyses. Relatively, ERA-Interim describes the seasonal variation of East Asian CREs well, albeit weaker than observed. The present study also suggests that in-depth exploration of the ability of reanalysis data to describe aspects relating to cloud properties and radiation is needed using more comprehensive observations.

Variation of sulfate aerosol concentrations over the western Pacific and their effect on clouds, radiation and precipitation

Under bilateral cooperation between the United States of America and the People's Republic of China, a series of research cruises were conducted over the western Pacific Ocean. It was found that a) the non-sea-salt sulfate aerosol particles are the major source of cloud condensation nuclei, b) the population of clouds and the total albedo are proportional to the concentration of condensation nuclei and consequently to the concentration of the non-sea-salt aerosol particles, and c) the amount of rainfall is inversely proportional to the concentration of non-sea-salt sulfate aerosol particles. It seems that anthropogenic sulfate aerosol particles affect the regional planetary albedo and climate and that the contribution from biogenically derived sulfate aerosol particles is of lesser importance.

CLOUD RADIATIVE AND MICROPHYSICAL EFFECTS ON THE RELATION BETWEEN SPATIAL MEAN RAIN RATE, RAIN INTENSITY AND FRACTIONAL RAINFALL COVERAGE

Cloud radiative and microphysical effects on the relation between spatial mean rain rate, rain intensity and fractional rainfall coverage are investigated in this study by conducting and analyzing a series of two-dimensional cloud resolving model sensitivity experiments of pre-summer torrential rainfall in June 2008. The analysis of time-mean data shows that the exclusion of radiative effects of liquid clouds reduces domain mean rain rate by decreasing convective rain rate mainly through the reduced convective-rainfall area associated with the strengthened hydrometeor gain in the presence of radiative effects of ice clouds, whereas it increases domain mean rain rate by enhancing convective rain rate mainly via the intensified convective rain intensity associated with the enhanced net condensation in the absence of radiative effects of ice clouds. The removal of radiative effects of ice clouds decreases domain mean rain rate by reducing stratiform rain rate through the suppressed stratiform rain intensity related to the suppressed net condensation in the presence of radiative effects of liquid clouds, whereas it increases domain mean rain rate by strengthening convective rain rate mainly via the enhanced convective rain intensity in response to the enhanced net condensation in the absence of radiative effects of liquid clouds. The elimination of microphysical effects of ice clouds suppresses domain mean rain rate by reducing stratiform rain rate through the reduced stratiform-rainfall area associated with severely reduced hydrometeor loss.

Effect of Merging of the Convective Cloud Clusters on Occurrence of Heavy Rainfall

Sun et al., (1983) have given some favourable environmental conditions and have shown that there are four common features in convective rainstorms. In this paper, an important process of evolution of cloud systems was revealed when heavy rainfall occurred based on the diagnostic analysis of heavy rainfall cases. When the different cloud systems merge into a large one, the mesoscale heavy rainfall occurs and enhances. In other words, the process of evolution of cloud systems emphasized in this paper is the process of interaction between two cloud systems when the heavy rainfall occurs. The favourable environmental condition is also investigated.

Cloud Base Height and Effective Cloud Emissivity Retrieval with Ground-Based Infrared Interferometer

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.

Effects of water and ice clouds on cloud microphysical budget:An equilibrium modeling study

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.

Analytical Studies of the Cloud Droplet Spectral Dispersion Influence on the First Indirect Aerosol Effect

Atmospheric aerosols （acting as cloud condensation nuclei） can enhance the cloud droplet number concentration and reduce the cloud droplet size, and in turn affect the cloud optical depth, as well as the cloud albedo, and thereby exert a radiative influence on climate （the first indirect aerosol effect）. In this paper, based on various relationships between cloud droplet spectral dispersion （c） and cloud droplet number concentration （Nc）, we analytically derive the corresponding expressions of the cloud radiative forcing induced by changes in the cloud droplet number concentration. Further quantitative evaluation indicates that the cloud radiative forcing induced by aerosols for the different ^-Nc relationships varies from -29.1% to 25.2%, compared to the case without considering spectral dispersion （e = 0）. Our results suggest that an accurate description of e - Nc relationships helps to reduce the uncertainty of the first indirect aerosol effect and advances our scientific understanding of aerosol-cloud-radiation interactions.

Effects of sea surface temperature,cloud radiative and microphysical processes,and diurnal variations on rainfall in equilibrium cloud-resolving model simulations

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.

Model Analysis of the Anthropogenic Aerosol Effect on Clouds over East Asia

A coupled meteorology and aerosol/chemistry model WRF-Chem(Weather Research and Forecast model coupled with Chemistry) was used to conduct a pair of simulations with present-day(PD) and preindustrial(PI) emissions over East Asia to examine the aerosol indirect effect on clouds.As a result of an increase in aerosols in January,the cloud droplet number increased by 650 cm-3 over the ocean and East China,400 cm-3 over Central and Southwest China,and less than 200 cm-3 over North China.The cloud liquid water path(LWP) increased by 40-60 g m-2 over the ocean and Southeast China and 30 g m-2 over Central China;the LWP increased less than 5 g m-2 or decreased by 5 g m-2 over North China.The effective radius(Re) decreased by more than 4 μm over Southwest,Central,and Southeast China and 2μm over North China.In July,variations in cloud properties were more uniform;the cloud droplet number increased by approximately 250-400 cm-3,the LWP increased by approximately 30-50 g m-2,and Re decreased by approximately 3 ?m over most regions of China.In response to cloud property changes from PI to PD,shortwave(SW) cloud radiative forcing strengthened by 30 W m-2 over the ocean and 10 W m-2 over Southeast China,and it weakened slightly by approximately 2-10 W m-2 over Central and Southwest China in January.In July,SW cloud radiative forcing strengthened by 15 W m-2 over Southeast and North China and weakened by 10 W m-2 over Central China.The different responses of SW cloud radiative forcing in different regions was related to cloud feedbacks and natural variability.

A cloud optical and microphysical property product for the advanced geosynchronous radiation imager onboard China's Fengyun-4 satellites: The first version

风云四号作为中国新一代静止气象卫星,提供了高时空分辨率的监测产品。本文介绍风云四号搭载的先进地球同步轨道辐射成像仪AGRI的云光学和微物理特性产品.该产品包含了基于双光谱通道反演的云光学厚度和云粒子有效半径产品,以及基于机器学习的云识别和云相态产品。与时空匹配的主动卫星观测结果对比显示,该产品的云识别和云相态的准确率分别在95%和85%;该产品提供的云光学厚度和云有效粒径与经典的MODIS产品的相关系数达到0.76和0.63.团队将持续优化和更新该云光学和微物理特性定量产品,服务风云四号卫星定量应用。

RADIATIVE AND MICROPHYSICAL EFFECTS OF ICE CLOUDS ON A TORRENTIAL RAINFALL EVENT OVER HUNAN,CHINA

The radiative and microphysical effects of ice clouds on a torrential rainfall event over Hunan,China in June 2004 are investigated by analyzing the sensitivity of cloud-resolving model simulations.The model is initialized by zonally-uniform vertical velocity,zonal wind,horizontal temperature and vapor advection from National Centers for Environmental Prediction(NCEP) /National Center for Atmospheric Research(NCAR) reanalysis data.The exclusion of radiative effects of ice clouds increases model domain mean surface rain rates through the increase in the mean net condensation associated with the increase in the mean radiative cooling during the onset phase and the increases in the mean net condensation and the mean hydrometeor loss during the mature phase.The decrease in the mean rain rate corresponds to the decreased mean net condensation and associated mean latent heat release as the enhanced mean radiative cooling by the removal of radiative effects of ice clouds cools the mean local atmosphere during the decay phase.The removal of microphysical effects of ice clouds decreases the mean rain rates through the decrease in the mean net condensation during the onset phase,while the evolution of mean net condensation and the mean hydrometeor changes from decrease to increase during the mature phase.The reduction in the mean rain rate is primarily associated with the mean hydrometeor change in the absence of microphysical effects of ice clouds during the decay phase.

Numerical study of aerosol effect on three types of clouds and precipitation in Beijing area

Three types of rainfall （storm, moderate and slight rainfall） in the Beijing area were simulated by the Weather Research and Fore- cast （WRF3.2） model coupled with Milbrandt-two-moment cloud microphysics scheme, to explore the effect of aerosols on clouds and precipitation under continental and maritime aerosol scenarios. Results indicate that an increase of aerosols has various effects on clouds and precipitation. （1） The amount of surface precipitation is obviously affected. With an increase of aerosol con- centration, the 48-hr total precipitation of storm and moderate rainfall decreased by 23% and 16.6%, respectively, and the 24-hr total precipitation of slight rainfall decreased by 14.0%. （2） The distribution of surface precipitation is also clearly affected. The average precipitation for a rain storm increases in most parts of western Beijing and decreases by more than 20 mm in most parts of eastern Beijing with increasing aerosol concentration. The average precipitation of moderate rainfall decreases by 0.1-5 mm in most parts of the Beijing area. The effect of increased aerosol concentration is weak for slight rainfall distribution in the study area. （3） With an increase of aerosol concentration, a narrower width and lower precipitation peak value are found in the storm rainfall, and its duration is prolonged for the high aerosol concentration. An earlier precipitation termination of moderate rainfall is found with increasing aerosol concentration. （4） The upper-air hydrometeors vary with aerosol concentration, For storm and moderate rainfall, significantly higher cloud water concentration and lower rain water were found under the continental aerosol scenario.

开放远程教育背景下云教室有效教学应用的影响因素研究

云教室是国家开放大学为了实现优质教育资源共享提出的一种新型远程教育方式,研究对云教室试点的相关教师进行的深度访谈和教学观察,应用扎根理论的程序化方法分析材料,在三级编码的基础上建构了影响云教室有效教学应用的“条件—过程—效果”模型,归纳出硬件技术、教学设计、团队教学、制度环境等四个关键影响因素的主范畴,提出了云教室的建构与教学应进行充分的前期调研与评估,建构与云教室教学配套的师资体系和管理保障机制;根据云教室的教学方式进行有针对性的教学设计等建议,以期打造高效课堂,提高教学质量,真正实现新技术与课程教学的深度融合。

东亚地区云微物理量分布特征的CloudSat卫星观测研究

本文利用2007～2010年整四年最新可利用的CloudSat卫星资料,对东亚地区（15°～60°N,70°～150°E）云的微物理量包括冰/液态水含量、冰/液态水路径、云滴数浓度和有效半径等的分布特征和季节变化进行了分析.本文将整个东亚地区划分为北方、南方、西北、青藏高原地区和东部海域五个子区域进行研究,结果显示：东亚地区冰水路径值的范围基本在700 g m-2以下,高值区分布在北纬40度以南区域,在南方地区夏季的平均值最大,为394.3 g m-2,而在西北地区冬季的平均值最小,为78.5 g m-2;而液态水路径的范围基本在600 g m-2以下,冬季在东部海域的值最大,达到300.8 g m-2,夏季最大值为281.5 g m-2,分布在南方地区上空.冰水含量的最高值为170 mg m-3,发生在8km附近,南方地区夏季的值达到最大,青藏高原地区的季节差异最大;而液态水含量在东亚地区的范围小于360 mg m-3,垂直廓线从10km向下基本呈现逐渐增大的趋势,峰值位于1～2 km高度上.冰云云滴数浓度在东亚地区的范围在150 L-1以下,水云云滴数浓度的值小于80 cm-3,垂直廓线的峰值均在夏季最大.冰云有效半径在东亚地区的最大值为90 μm,发生在5km左右;水云有效半径在东亚地区的值分布在10km以下,最大值为10～12 μm,基本位于1～2 km高度上.从概率分布函数来看,东亚地区冰/水云云滴数浓度的分布呈现明显的双峰型,其他量基本为单峰型.本文的结果可以为全球和区域气候模式在东亚地区对以上云微物理量的模拟提供一定的观测参考依据.