【作者】 蔡淼；

【导师】 刘黎平； 周毓荃；

【作者基本信息】 南京信息工程大学 ， 大气物理学与大气环境， 2013， 博士

【摘要】 能量和水分循环是全球气候系统中的重要过程,云水作为大气水循环的重要环节,在气候变化、天气分析和人工影响天气中的作用十分关键。对云水的研究,包括云场的三维结构诊断、云水平衡和转化等基本问题,过去的研究很少。本论文利用Cloudsat云观测和再分析资料,提出了三维云场和云水场的诊断方法,对包括云水在内的大气水分收支和云水资源、降水效率等进行了计算评估分析。本论文的主要工作和初步结果包括：1、提出了包括水凝物在内的大气水分收支方程,提出了一定时空范围内参与大气水循环的各种水物质总量、降水效率、更新周期等概念和计算公式,提出了云水资源和空中留存云水量的概念。2、为了得到三维云场的分布,利用2007-2008年Cloudsat云检测产品与配套ECWMF再分析资料的相对湿度进行统计,得出我国云内外相对湿度判别阈值及其随高度变化,提出了基于再分析资料的三维云场分布监测诊断方法。研究发现,Cloudsat云检测mask值大于20的云区位置与相对湿度高值区有很好的时空对应；不同高度范围的云内相对湿度都呈单峰型分布,峰值在相对湿度100%附近,晴空相对湿度受当地大气环境影响,各地各高度都有差别；云内外累积频率交叉法和TS评分法统计得出的诊断云相对湿度阈值相差10%左右,阈值随高度均先减小后增加。3、基于ECMWF的云相对湿度阈值垂直分布,利用NCEP再分析资料对全国三维云场的分布进行个例诊断应用,虽然NCEP资料的时空分辨率较粗,其相对湿度诊断的云场分布比较符合实际云降水观测；云区附近的湿度梯度大,相对湿度阈值法诊断的云区总体比较稳定；诊断的云区与上升气流区对应较好,云区和晴空的分布与卫星Tbb观测大致对应,云厚即总云层数与光学厚度和地面降水的分布比较一致；诊断的云垂直分布与地面云观测比较一致,云层密实深厚的区域通常对应着地面降水；单点的云垂直结构随时间演变与当地的雷达和地面云降水观测都比较一致。4、为了得到三维云水场分布,利用2007-2008年Cloudsat云分类和云含水量产品,统计分析了中国云含水量和粒子有效半径的典型值及分布特征。结果表明：全国平均而言,中国地区云液水含量(LWC)在低层均最为丰沛,随高度增加而减小,平均值小于0.35g/m3；液相粒子有效半径平均值整层都在10μ m左右。云冰水含量(IWC)的平均值小于0.1g/m3,层状云IWC随高度呈增加趋势,对流云IWC随高度先增加后减小两类云中最大的IWC含量分别在中高层和7km高度附近；冰相粒子有效半径(Ice_Ref)的平均值在60-90μm之间。中国不同气候区的对流云含水量均大于层状云含水量,LWC从南向北,从东向西减少,而IWC在6km以下从西向东减小,6km以上从南向北减小。5、基于大气水分收支方程和三维云场的诊断识别方法,利用NCEP再分析资料,结合卫星和雷达观测及地面降水资料,对不同时空尺度的大气水分收支和降水效率进行评估。结果表明：2011年中国全年总降水量约6.58万亿吨,水汽总输入量为22.6万亿吨,全年水汽净输入2.1万亿吨,占总输入量的9%。水凝物总输入量为2万亿吨,全年水凝物净输入两千亿吨。2011年水汽和水凝物的更新周期的分别为11天和15小时,总水物质和水凝物的年降水效率分别为18%和77%,与前人的气候分析结果比较一致。大气水循环存在明显的季节和年变化特征,由于不同季节的云系发展和覆盖差异,水汽、水凝物和地面降水总量在夏季最为丰沛,冬季最少,水汽和水凝物的更新周期为夏季最短,冬季最长,水汽和水凝物的降水效率夏季最高,冬季最低。春秋季的水物质循环和转换效率居于冬夏季之间。中国地区不同时间尺度的评估表明,随时段增长,水物质输入(出)量变大,初(终)值所占比率变小；凝结量在水凝物中所占比例很大,不同区域和云系有一定差别；降水日的水物质更新速率比全年平均快。不同空间尺度范围,水凝物的通量与净凝结量相比重要性不同,同时又与研究时段内的降水情况密切相关。对于局地的对流云,水凝物主要来源于研究区域内水汽的凝结。不同降水日,大气水分收支的评估结果有很大差异。6、利用WRF模式对2009年4月18日的降水过程进行模拟研究,结果表明：CAMS方案对本次过程的水汽、水凝物和降水的模拟效果总体较好,与NCEP水汽场、卫星光学厚度及诊断的云场和地面降水实测结果都比较一致,能够较为真实的反应出云降水的发展和演变。其中,诊断的云区和模式预报云场总是形成于天气系统附近,并随着天气系统发展移动,云中雪花和霰等大粒子含量更为丰沛,小云粒子和冰晶含量较少。后期可细致分析此次降水过程中的大气水平衡及水分收支转换和云水资源量。更多还原

【Abstract】 Energy and water cycle is an important process in the global climate system. Cloud plays a very important role Cloud plays a very important role in climate change, weather analysis and weather modification which is the main process in the global climate system as an important process of atmospheric water cycle.There are few research on cloud water, which includes three dimension cloud field diagnosis, cloud water balance and transformation. Based on the cloudsat observation and reanalysis data, three-dimensional cloud fields and cloud water field diagnostic methods is proposed. Water budget including hydrometeors, cloud water resource and precipitation efficiency are calculated, The main work and preliminary results of this paper are as follows.(1) Atmospheric moisture budget equations including hydrometeors are proposed. water budget three-dimensional cloud fields and cloud water field diagnostic methods is proposed. The concepts and formulas of various water material amount, precipitation efficiency and update cycle in a certain time and space scale are proposed. The concepts of cloud water resource and atmospheric remanding cloud water are given.(2) In order to get the three-dimension cloud distribution, based on cloud mask and relative humidity (RH) provided by Cloudsat products from2007to2008. The cloud determining RH threshold and its vertical variation over china is statistical analyzed and the monitoring and diagnosis method on three-dimensional cloud fields distribution is proposed, based on reanalysis data. Cloud region where cloud mask, which is bigger than20,has a good space and time corresponding to the high value relative humidity region.Distribution of RH in cloud at different height range shows single peak type, and the peak is near a RH value of100%. Local atmospheric environment affects the RH distribution outside cloud, which leads to RH distribution vary in different region or different height. RH threshold used for cloud diagnostic statist through the cross of cumulative RH frequency within and outside cloud, is less than the RH threshold get from Threat score(TS) method by10%. The two threshold both increased with the height first, and then reduced.(3)The method is applied to a three dimension cloud diagnosis case study which based on NCEP reanalysis data, and the diagnostic cloud field is compared to satellite, radar and cloud precipitation observation on ground. It is found that, RH gradient is very high around cloud region and the cloud area which diagnosed by RH threshold method is relatively stable. Diagnostic cloud area highly corresponds to updraft region and the cloud and clear sky distribution corresponds to satellite the Tbb observations overall. Diagnostic cloud depth, or sum cloud layers distribution greatly consists with optical thickness and precipitation on ground. The cloud vertical profile reveals the relation between cloud vertical structure and weather system clearly. Diagnostic of cloud distribution corresponds to cloud observations on ground very well. Precipitation on ground usually can be observed at deep-developed cloud area. The time series of cloud vertical structure evolution at single point is well consistent with local radar and surface cloud and precipitation observations.(4) In order to get the three-dimension cloud water distribution, based on Cloudsat cloud classification and cloud water content products from2007to2008. cloud water content and typical value and distribution characteristics of particle effective radius over China are statistical analyzed and different cloud systems. Results showed that, as the national average. the liquid water content (LWC) is most plentiful at lower layer and decreases with altitude. The average of LWC is less than0.35g/m3, and average effective radius of the liquid phase particles is about10u m at all layers. The average ice water content (IWC) is less than0.1g/m3.The IWC in stratiform clouds increases with altitude, while which in convective cloud is first increases with altitude. The largest IWC in stratiform and convective clouds is at high level and near7km respectively. The average effective radius of the ice phase particles is between60-90μ m. In different climatic zones of china. water content of convective cloud is always greater than stratiform cloud.LWC decreases from south to north, from the east to the west, while IWC reduces from west to east under6km height and reduces from south to north over6km height.(5) According to technology program of monitoring and evaluation of cloud and water resources, using the reanalysis data of NCEP. combining the observations of satellite and radar and ground precipitation data. we can calculate and assess the cloud and water resources of different cloud system, different times and range, and the main conclusion can be listed as follows:The daily calculated results of cloud and water resources over the year of China in2011show that, the total annual precipitation is about658trillion tons, the total inputting water vapor content is22.6trillion tons, the annual net inputting water vapor content is2.1trillion tons, the total inputting hydrometeors content is2trillion tons, and the annual net inputting hydrometeors content is200billion tons. The annual average value of update cycle of water vapor and hydrometeors were11days and15hours. and the annual average value of precipitation efficiency of water vapor and hydrometeors were18%and77%. Atmospheric water cycle has a significant seasonal and annual variation feature, owing to development and coverage’s diversity of cloud system in different season, the water vapor, hydrometeors and total ground precipitation are most abundant in summer and least in winter, the update cycle of water vapor and hydrometeors are shortest in summer and longest in winter, the precipitation efficiency of water vapor and hydrometeors are highest in summer and lowest in winter. The efficiency of water material recycling and conversion in spring and autumn is between summer and winter. The evaluation result varies in different precipitation days. The assessment result of cloud water resources is closely related to research area and period, when research period is very short, the initial stock of water material take up a larger proportion in total content of water material; when research period is very long just like the whole year, the advection of water material is particularly important and instantaneous stock has little effect on the results. With regard to local convective precipitation process, it has fast updating velocity of water material and high precipitation efficiency. The spatial and temporal scale has great impact on the accessing of atmospheric water balance and cloud water resource. The water substances initial and final value is small relative to the flux evaporation, condensation net amount and precipitation and can be ignored in long time assessing. The shorter research period, the greater the impact of the initial and final values of the water substance. The importance of hydrometeors flux compared with the net amount of condensation varies with different scales, meanwhile closely related to precipitation in research period.(6) WRF model simulation study of the precipitation process on April18,2009shows that, water vapor, hydrometeors and precipitation of this event are well simulated overall by the CAMS program. The simulated results are in good consistent to NCEP water vapor field, satellite retrieval optical thickness,the diagnostic field of cloud and surface precipitation observations, which reflect the development and evolution of the real cloud and precipitation. Diagnosis cloud and simulated cloud field always form nearby the weather system and develop and move with the weather systems. There’s more abundant of big particles like snowflake and graupel in cloud than little cloud particles and ice crystals. The atmospheric water balance, moisture budget and cloud water resource of this event can be analyzed later.更多还原