Observational characteristics of cloud radiative effects over three arid regions in the Northern Hemisphere

Cloud–radiation processes play an important role in regional energy budgets and surface temperature changes over arid regions. Cloud radiative effects (CREs) are used to quantitatively measure the aforementioned climatic role. This study investigates the characteristics of CREs and their temporal variations over three arid regions in central Asia (CA), East Asia (EA), and North America (NA), based on recent satellite datasets. Our results show that the annual mean shortwave (SW) and net CREs (SWCRE and NCRE) over the three arid regions are weaker than those in the same latitudinal zone of the Northern Hemisphere. In most cold months (November–March), the longwave (LW) CRE is stronger than the SWCRE over the three arid regions, leading to a positive NCRE and radiative warming in the regional atmosphere–land surface system. The cold-season mean NCRE at the top of the atmosphere (TOA) averaged over EA is 4.1 W m^–2, with a positive NCRE from November to March, and the intensity and duration of the positive NCRE is larger than that over CA and NA. The CREs over the arid regions of EA exhibit remarkable annual cycles due to the influence of the monsoon in the south. The TOA LWCRE over arid regions is closely related to the high-cloud fraction, and the SWCRE relates well to the total cloud fraction. In addition, the relationship between the SWCRE and the low-cloud fraction is good over NA because of the considerable occurrence of low cloud. Further results show that the interannual variation of TOA CREs is small over the arid regions of CA and EA, but their surface LWCREs show certain decreasing trends that correspond well to their decreasing total cloud fraction. It is suggested that combined studies of more observational cloud properties and meteorological elements are needed for indepth understanding of cloud–radiation processes over arid regions of the Northern Hemisphere.     

Analysis of Short-term Cloud Feedback in East Asia Using Cloud Radiative Kernels

Cloud radiative kernels were built by BCC_RAD(Beijing Climate Center radiative transfer model) radiative transfer code. Then, short-term cloud feedback and its mechanisms in East Asia(0.5°S-60.5°N, 69.5°-150.5°E) were analyzed quantitatively using the kernels combined with MODIS satellite data from July 2002 to June 2018. According to the surface and monsoon types, four subregions in East Asia—the Tibetan Plateau, northwest, temperate monsoon(TM), and subtropical monsoon(SM)—were selected. The average longwave, shortwave, and net cloud feedbacks in East Asia are-0.68 ± 1.20, 1.34 ± 1.08, and 0.66 ± 0.40 W m~(-2) K~(-1)(±2σ), respectively, among which the net feedback is dominated by the positive shortwave feedback. Positive feedback in SM is the strongest of all subregions, mainly due to the contributions of nimbostratus and stratus. In East Asia, short-term feedback in spring is primarily caused by marine stratus in SM, in summer is primarily driven by deep convective cloud in TM, in autumn is mainly caused by land nimbostratus in SM, and in winter is mainly driven by land stratus in SM. Cloud feedback in East Asia is chiefly driven by decreases in mid-level and low cloud fraction owing to the changes in relative humidity, and a decrease in low cloud optical thickness due to the changes in cloud water content.     

近20年全球总云量变化趋势分析

利用ISCCP月平均云气候资料集的总云量资料, 采用趋势分析的方法, 得到1983年7月至2001年9月近20年来全球平均总云量的变化趋势, 并分析云量变化的可能原因。近20年全球增温幅度加快, 研究这期间云的变化, 对气候研究和模拟具有重要的意义。结果表明:平均大气环流决定总云量的分布;全球平均总云量的变化趋势在20世纪80年代末发生逆转, 即由增加转为减少;全球平均云量呈减少的变化趋势, 2000年与1987年相比, 减少量约占平均总云量的4%;从地理位置上看, 云量的变化存在区域性差异, 热带和中纬度地区的总云量减少较多, 高纬度地区云量略有增加, 其中南极大陆云量增加较多。     

Assessment of the first indirect radiative effect of ammonium-sulfate-nitrate aerosols in East Asia

A physically based cloud nucleation parameterization was introduced into an optical properties/radiative transfer module incorporated with the off-line air quality modeling system Regional Atmospheric Modeling System (RAMS)-Models-3 Community Multi Scale Air Quality (CMAQ) to investigate the distribution features of the first indirect radiative effects of sulfate, nitrate, and ammonium-sulfate-nitrate (ASN) over East Asia for the years of 2005, 2010, and 2013. The relationship between aerosol particles and cloud droplet number concentration could be properly described by this parameterization because the simulated cloud fraction and cloud liquid water path were generally reliable compared with Moderate Resolution Imaging Spectroradiometer (MODIS) retrieved data. Simulation results showed that the strong effect of indirect forcing was mainly concentrated in Southeast China, the East China Sea, the Yellow Sea, and the Sea of Japan. The highest indirect radiative forcing of ASN reached ?3.47 W m^?2 over Southeast China and was obviously larger than the global mean of the indirect forcing of all anthropogenic aerosols. In addition, sulfate provided about half of the contribution to the ASN indirect forcing effect. However, the effect caused by nitrate was weak because the mass burden of nitrate was very low during summer, whereas the cloud fraction was the highest. The analysis indicated that even though the interannual variation of indirect forcing magnitude generally followed the trend of aerosol mass burden from 2005 to 2013, the cloud fraction was an important factor that determined the distribution pattern of indirect forcing. The heaviest aerosol loading in North China did not cause a strong radiative effect because of the low cloud fraction over this region.     

Influence of the Asian-Pacific Oscillation on Spring Precipitation over Central Eastern China

The linkage between the Asian-Pacific oscillation(APO)and the precipitation over central eastern China in spring is preliminarily addressed by use of the observed data.Results show that they correlate very well,with the positive(negative)phase of APO tending to increase(decrease)the precipitation over central eastern China.Such a relationship can be explained by the atmospheric circulation changes over Asia and the North Pacific in association with the anomalous APO.A positive phase of APO,characterized by a positive anomaly over Asia and a negative anomaly over the North Pacific in the upper-tropospheric temperature,corresponds to decreased low-level geopotential height(H)and increased high-level H over Asia,and these effects are concurrent with increased low-level H and decreased high-level H over the North Pacific.Meanwhile,an anticyclonic circulation anomaly in the upper troposphere and a cyclonic circulation anomaly in the lower troposphere are introduced in East Asia,and the low-level southerly wind is strengthened over central eastern China.These changes provide advantageous conditions for enhanced precipitation over central eastern China.The situation is reversed in the negative phase of APO,leading to reduced precipitation in this region.     

Spatiotemporal Variations of Cloud Amount over the Yangtze River Delta, China

Based on the NOAA's Advanced Very High Resolution Radiometer(AVHRR) Pathfinder Atmospheres Extended(PATMOS-x) monthly mean cloud amount data, variations of annual and seasonal mean cloud amount over the Yangtze River Delta(YRD), China were examined for the period 1982–2006 by using a linear regression analysis. Both total and high-level cloud amounts peak in June and reach minimum in December, mid-level clouds have a peak during winter months and reach a minimum in summer, and lowlevel clouds vary weakly throughout the year with a weak maximum from August to October. For the annual mean cloud amount, a slightly decreasing tendency(–0.6% sky cover per decade) of total cloud amount is observed during the studying period, which is mainly due to the reduction of annual mean high-level cloud amount(–2.2% sky cover per decade). Mid-level clouds occur least(approximately 15% sky cover) and remain invariant, while the low-level cloud amount shows a significant increase during spring(1.5% sky cover per decade) and summer(3.0% sky cover per decade). Further analysis has revealed that the increased low-level clouds during the summer season are mainly impacted by the local environment. For example,compared to the low-level cloud amounts over the adjacent rural areas(e.g., cropland, large water body, and mountain areas covered by forest), those over and around urban agglomerations rise more dramatically.     

CFMIP大气环流模式模拟的东亚云辐射强迫特征

通过与卫星观测云和辐射资料的比较,检验了10个大气环流模式对东亚地区云量、垂直结构、光学属性以及辐射特征的模拟能力.10个模式的模拟结果均来自"云反馈模式比较计划"(CFMIP),为便于与国际卫星云气候计划(ISCCP)资料的比较,所有模式都引入了ISCCP模拟器.结果表明,10个模式均能模拟出东亚地区冬、夏两季云量及...     

Characterization of cloud microphysical properties in different cloud types over East Asia based on CloudSat/CALIPSO satellite products

利用CloudSat/CALIPSO卫星资料,本文揭示了东亚三个代表性区域的云微物理属性,为评估和改进模式云微物理过程提供重要的观测基础.研究的云微物理量包括云水/冰质量,数浓度和有效半径.研究表明:暖云中云水质量和数浓度随高度增加而减小,有效半径处于8-14μm范围.对于冰云,云冰质量和有效半径随高度增加而减小,而数浓度在垂直方向上变化不大.此外,云微物理属性在不同云型之间存在显著差异:积云的云水质量和数浓度最大,而卷云的云水质量和数浓度最小.从三个区域的对比结果来看,相比于华东和西北太平洋地区,青藏高原地区暖云的云水质量和数浓度较小,而冰云的则较大.     

Cloud vertical distribution from radiosonde,remote sensing,and model simulations

Knowledge of cloud vertical structure is important for meteorological and climate studies due to the impact of clouds on both the Earth’s radiation budget and atmospheric adiabatic heating. Yet it is among the most difficult quantities to observe. In this study, we develop a long-term (10 years) radiosonde-based cloud profile product over the Southern Great Plains and along with ground-based and space-borne remote sensing products, use it to evaluate cloud layer distributions simulated by the National Centers for Environmental Prediction global forecast system (GFS) model. The primary objective of this study is to identify advantages and limitations associated with different cloud layer detection methods and model simulations. Cloud occurrence frequencies are evaluated on monthly, annual, and seasonal scales. Cloud vertical distributions from all datasets are bimodal with a lower peak located in the boundary layer and an upper peak located in the high troposphere. In general, radiosonde low-level cloud retrievals bear close resemblance to the ground-based remote sensing product in terms of their variability and gross spatial patterns. The ground-based remote sensing approach tends to underestimate high clouds relative to the radiosonde-based estimation and satellite products which tend to underestimate low clouds. As such, caution must be exercised to use any single product. Overall, the GFS model simulates less low-level and more high-level clouds than observations. In terms of total cloud cover, GFS model simulations agree fairly well with the ground-based remote sensing product. A large wet bias is revealed in GFS-simulated relative humidity fields at high levels in the atmosphere.     

副热带东太平洋低云对LASG耦合环流模式FGCM-0中"双ITCZ"的影响

与其他耦合环流模式一样,LASG耦合模式FGCM-0也存在虚假的“双ITCZ”。为了认识FGCM-0中“双ITCZ”,首先研究了FGCM-0的大气分量模式,剧INCAR(美国国家大气研究中心)的公用气候模式CCM3对秘鲁和加利福尼亚沿岸低云以及低层大气整体稳定度的模拟能力。发现：尽管CCM3模拟的低层大气整体稳定度与利用NCEP(美国国家环境预报中心)再分析资料分析的结果较一致,但模拟的低云量比ISCCP(国际卫星云气候计划)观测值显偏少。利用ISCCP低云量与由NCEP再分析温度场分析的低层整体稳定度之间的回归关系,修改了CCM3中低云参数化方案,并用于敏感性试验,以研究副热带东太平洋低云对FGCM-0中“双ITCZ”的影响。结果发现,修改的方案能显增强对低云量的模拟,秘鲁沿岸冷海域低云量增加能显减弱赤道以南热带东太平洋海表面温度(SST)的暖偏差,但同时也将使赤道冷舌增强、向西伸展更远;加利福尼亚沿岸低云量增加可以有效减弱赤道以北ITCZ区SST暖偏差。为了检验秘鲁沿岸SST与低云间的正反馈,又实施了一个控制秘鲁沿岸SST的敏感性试验,结果表明：控制秘鲁沿岸SST抑制其增暖,对自东南太平洋向西北至中、西赤道太平洋广大区域产生的影响,与增加秘鲁沿岸低云量产生的影响相似。     

夏季白天中国中东部不同类型云分布特征及其对近地表气温的影响

本文利用2001～2017年ERA5再分析资料以及CERES卫星资料,探究夏季白天中国中东部不同类型云的云量及其光学厚度的时空变化特征,并利用一维辐射对流模式定量分析不同类型云对近地表气温的影响。观测结果表明:夏季白天中国中东部总云量及其光学厚度整体呈由南向北逐渐减小的分布特征,且中高云量占主导地位。总云量整体呈?0.3% a?1显著减少趋势,其中低云的贡献（?0.27% a?1）最大;总云光学厚度为0～0.1 a?1增加趋势,其中低云光学厚度（0.06 a?1）和中低云光学厚度（0.03 a?1）呈增加趋势,而中高云光学厚度（?0.08 a?1）和高云光学厚度（?0.03 a?1）呈减少趋势。模式结果表明:四种不同类型云的温度效应（Cloud Effect Temperature, CET）均为负值,表现为降温效应。低云、中低云、中高云和高云的年均CET值分别为?2.9°C、?2.7°C、?2.2°C和?1.7°C。其中,低云在华北平原降温可达?5°C;中低云和中高云在四川盆地和云贵高原降温可达?7.8°C。不同类型云温度效应与近地表气温的年际变化具有较好的一致性,具体表现为:2004年前（后）近地表气温呈现下降（上升）趋势,不同类型云的CET在此期间呈下降（上升）趋势,表现为云的降温效应增强（减弱）与近地表气温下降（上升）相对应,体现了夏季白天中国中东部4种不同类型云温度效应与近地表气温都呈正相关关系。特别地,夏季白天中国中东部中高云量占主导地位,其CET与近地表气温的相关系数高达0.63。综上,夏季白天中国中东部不同类型云温度效应对近地表气温的影响不同,但均呈正相关关系。定量分析不同类型云对近地表气温的影响可以为定量研究云反馈对区域增暖的作用以及合理预估未来区域增暖情景提供必要的科学参考。     

四川地区云和空中水资源分布与演变

利用1971～2000年台站云降水资料和NCEP再分析资料,分析了四川地区云和空中水资源的分布与演变。研究发现:四川地区平均总云量为7.2成,低云量4.7成,全年阴天日数193.5天,降水日数154.0天,小到中雨日147.1天;全年大气可降水量为181.7kg.m-2。云有明显的季节变化特征,总云量夏季最高,春季次之,冬季最低,低云量夏季最高,秋季次之,冬季最低。大气可降水量夏季最大,秋季次之,冬季最少。云和小到中雨日的空间分布具有明显的地域性,且夏季分布与全年分布显著不同。在高原上,总云和低云、降水日、小到中雨日呈相反的变化趋势,总云在平均状态附近波动略有减少,而低云、降水日、小到中雨日在平均状态附近波动略有增加;在盆地内,云和降水日的演变趋势相同,总云量、低云量、降水日、小到中雨日都在线性减少。30年来四川地区大气可降水量线性变化则略有增多。     

2000-2018年东亚地区云顶高度的时空变化特征

为了了解区域云顶高度对过去气候变化的响应,基于卫星搭载的MODIS传感器提供的2000年3月至2018年2月MOD03_08_v6.0数据,分析了东亚地区云顶高度2000—2018年的时空变化特征,并探讨其长期变化的原因。研究发现,东亚地区云顶高度呈西南高东北低的特征。云顶高度在东亚地区以0.020 km/a的变率增长,其中大陆东部云顶高度的年际变率为0.035 km/a,东部海域年际变率为0.034 km/a。在东部海域地区云顶高度的变化同海表温度的变化相关性较高,相关系数为0.68,这表明云顶高度的变化受下垫面的影响。在东亚地区30°~40°N区域内,年平均云顶高度的增加较为明显。此外,夏季云顶高度在长江中下游盆地、塔里木盆地、吐鲁番盆地以及四川盆地东北部呈-0.03 km/a的减少趋势,这是由于更多低云的形成降低了云顶高度;冬季云顶高度在东亚地区40°N以北呈下降趋势,而在40°N以南呈增加趋势。     

东亚地区云垂直结构的CloudSat卫星观测研究

本文利用卫星CloudSat同时结合了与其同轨道的卫星CALIPSO(Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations)2007至2009年3年的观测资料,将东亚地区划分为六个研究区域,着重研究了东亚地区云垂直分布的统计特征.结果表明:东亚地区不同高度的云量之和具有明显的季节变化趋势,夏季最大,春秋次之,冬季最小.海洋上空的单层云量最大值出现在冬季,而在陆地上空则出现在夏季.从云出现概率来看,东亚地区单层云出现的概率在春、夏、秋、冬季节依次为52.2%,48.1%,49.2%和51.9%,而多层(2层和2层以上)云出现的概率在春、夏、秋、冬季节分别为24.2%,31.0%,19.7%,15.8%.云出现的总概率和多层云出现的概率,在六个区域都呈现出夏季最大,冬季最小;对4个季节都呈现出东亚南部比东亚北部大,海洋上空比陆地上空大的特点,表明云出现的总概率的季节变化主要由多层云出现的概率的变化决定.东亚地区云系统中最高层云云顶的高度,在夏季最高,为15.9 km,在冬季最低,为8.2 km;在东亚南部和海洋上空较高,平均为15.1 km;在东亚北部较低,平均为12.1 km,且呈现东亚南北部之间差异较大的特点.东亚地区云系统的云层厚度基本位于1 km到3 km之间,且夏季大,冬季小;对同一季节,不同区域的云层厚度差别较小;当多层云系统中的云层数目增加时,云层的平均厚度减少,且较高层的云层平均厚度大于较低层的.云层间距的概率分布基本呈单峰分布,出现峰值范围的云层间距在1到3 km之间,各区域之间没有明显差别,季节变化也不大.本文的研究为在气候模式中精确描述云的垂直结构提供了有用的参数化依据.     

Numerical Study of the Effect of Anthropogenic Aerosols on Spring Persistent Rain over Eastern China

The eff ect of anthropogenic aerosols on the spring persistent rain （SPR） over eastern China is investigated by using a high-resolution Community Atmosphere Model version 5.1 （CAM5.1）. The results show that the SPR starts later due to anthropogenic aerosols, with a shortened duration and reduced rainfall amount. A reduction in air temperature over the low latitudes in East Asia is linked to anthropogenic aerosols;so is a weakened southwesterly on the north side of the subtropical high. Meanwhile, air temperature increases signifi cantly over the high latitudes. This north-south asymmetrical thermal eff ect acts to reduce the meridional temperature gradient, weakening the upper-level westerly jet over East Asia and the vertical motion over southeastern China. As a result, the SPR is reduced and has a much shorter duration. The indirect eff ect of anthropogenic aerosols also plays an important role in changing the SPR. Cloud droplet number concentration increases due to anthropogenic aerosols acting as cloud condensation nuclei, leading to a reduction in cloud eff ective radius over eastern China and a reduced precipitation effi ciency there.     

Evaluation of cloud properties in the NOAA/NCEP global forecast system using multiple satellite products

Knowledge of cloud properties and their vertical structure is important for meteorological studies due to their impact on both the Earth’s radiation budget and adiabatic heating within the atmosphere. The objective of this study is to evaluate bulk cloud properties and vertical distribution simulated by the US National Oceanic and Atmospheric Administration National Centers for Environmental Prediction Global Forecast System (GFS) using three global satellite products. Cloud variables evaluated include the occurrence and fraction of clouds in up to three layers, cloud optical depth, liquid water path, and ice water path. Cloud vertical structure data are retrieved from both active (CloudSat/CALIPSO) and passive sensors and are subsequently compared with GFS model results. In general, the GFS model captures the spatial patterns of hydrometeors reasonably well and follows the general features seen in satellite measurements, but large discrepancies exist in low-level cloud properties. More boundary layer clouds over the interior continents were generated by the GFS model whereas satellite retrievals showed more low-level clouds over oceans. Although the frequencies of global multi-layer clouds from observations are similar to those from the model, latitudinal variations show discrepancies in terms of structure and pattern. The modeled cloud optical depth over storm track region and subtropical region is less than that from the passive sensor and is overestimated for deep convective clouds. The distributions of ice water path (IWP) agree better with satellite observations than do liquid water path (LWP) distributions. Discrepancies in LWP/IWP distributions between observations and the model are attributed to differences in cloud water mixing ratio and mean relative humidity fields, which are major control variables determining the formation of clouds.     

中国地区空中云水资源气候分布特征及变化趋势

利用1984~2004年国际卫星云气候学计划（ISCCP）的云水路径（CWP）资料,分析了中国地区空中云水资源的分布特征、变化趋势以及与大气环流和湿度场的关系。研究发现,中国地区CWP的分布与大气环流、地形特征和大气湿度分布及水汽传输密切相关,中国地区CWP存在明显的季节变化,6月全国平均CWP最高,10月最低,不同地区季节变化差异明显。从变化趋势看,中国地区CWP以增加为主,青藏高原东部、内蒙古东部地区以及西北东部地区CWP的增加趋势较强。全国范围内,冬季和秋季CWP增加较大,春季和夏季增加较小。这些变化主要与大气环流变化导致的抬升运动的增强以及大气湿度（水汽）增加有关。中国地区空中云水资源在全球变暖的背景下表现出增加的趋势,符合气温增加导致水循环增强的观点。     

MERIDIONAL PROPAGATION OF EAST ASIAN LOW-FREQUENCY MODE AND MIDLATITUDE LOW-FREQUENCY WAVES*

Based on June to September 1981 ECMWF grid datasets analysis is done of the characteristics of thepropagation and structure of low-frequency(quasi 40 day) oscillation over eastern Asia. Results show aseparating(confluence) belt for the meridional propagation of low-frequency zonal(meridional) winds at higher(lower) levels over subtropical latitudes at 120°E, revealing that the oscillation of the zonal winds is quasi-geostrophic in pature and in phase in the high- and low-level. It is also found that the eastward propagationof the high-level zonal winds around 35°N in East Asia is the result of eastward march of midlatitude low-frequency waves with 60-90 longitude wavelength and speed of 1.5-2.0 longitudes per day. In addition, suchlow-frequency vortices, when moving over the coastwise region, tend to develop, accompanied by sharp oscil-lation in the westerly jetstream over eastern Asia.     

Seasonal scale variability of the East Asian winter monsoon and the development of a two-dimensional monsoon index

This study investigates the seasonal scale variability of the East Asian winter monsoon (EAWM), which is distinguished from the seasonal cycle with temporal variation throughout winter. Winters lasting 120 days (Nov. 17–Mar. 16) for a period of 64 years from the NCEP daily reanalysis data set are used to study the seasonal scale variability of the EAWM. Cyclostationary empirical orthogonal function (CSEOF) analysis is adopted to decompose the variability of the EAWM. The second CSEOF mode of 850-hPa temperature exhibits a seasonal scale variation, the physical mechanism of which is explained in terms of physically consistent variations of temperature, geopotential height, sea level pressure, wind, and surface heat fluxes. The seasonal-scale EAWM exhibits a weak subseasonal and a strong interannual variability and has gradually weakened during the 64 years. In a weak EAWM phase, the land-sea contrast of sea level pressure declines in East Asia. Consistent with this change, low-level winds decrease and warm thermal advection increases over the eastern part of mid-latitude East Asia. Latent and sensible heat fluxes are reduced significantly over the marginal seas in East Asia. However, during a strong EAWM phase, the physical conditions in East Asia reverse. A large fraction of the variability of the EAWM is explained by the seasonal cycle and the seasonal scale variation. A two-dimensional EAWM index was developed to explain these two distinct components of the EAWM variability. The new index appears to be suitable for measuring both the subseasonal and the interannual variability of the EAWM.     

东亚夏季气溶胶—云—降水分布特征及其相互影响的资料分析

东亚季风气候受到自然因素和人类活动的共同影响,而人类活动因子中气溶胶的作用尤为关键,采用诊断分析的手段研究东亚地区气溶胶的特征及其与云和降水的相互关系具有重要的科学意义。本文利用MODIS(moderate-resolution imaging spectroradiometer)气溶胶和云资料以及TRMM(Tropical Rainfall Measuring Mission)降水数据,分析了东亚夏季气溶胶、云、降水的时空分布特征,研究了气溶胶与云和降水的相互关系。结果表明:中国四个典型地区(珠三角、长三角、四川盆地、京津唐)2001～2011年夏季(6～8月)平均气溶胶光学厚度(Aerosol Optical Depth, AOD)变化范围为0.40～0.68,云光学厚度平均值为18.7～23.6,水云云滴有效粒子半径在20.2～25.6 μm,冰云有效粒子半径在12.9～15.3 μm,云水路径为222.2～243.8 g m-2,降水强度平均值3.6～8.6 mm d-1;珠三角气溶胶光学厚度有显著降低趋势,年倾向为-3.31%,四川盆地云滴有效粒子半径(冰云、水云)和云水路径年变化趋势为-0.42%、-0.49%和-1.26%,京津唐夏季降水量年增幅为3.24%。气溶胶光学厚度和云光学厚度呈正相关,相关系数最大为0.77;在相对湿度较低(30%～50%)情况下,气溶胶光学厚度与云滴有效粒子半径呈负相关;气溶胶光学厚度与云水路径呈正相关,相关系数最大为0.92;相对于低污染情况(AOD<0.5),高污染情况(AOD>0.5)下出现大雨(>10 mm d-1)的频率增加了6.6%～19.1%,小雨(<1 mm d-1)的频率减少了0.72%～7.3%。在水汽含量较少的情况下,气溶胶的增加导致云滴有效粒子半径的减少;气溶胶增强了南方地区的对流性降水,抑制了北方地区层云降水。