季节转换期间副热带高压带形态变异及其机制的研究Ⅱ:亚洲季风区季节转换指数

在“季节转换期间副热带高压带形态变异及其机制的研究Ⅰ :副热带高压结构气候学特征研究”的基础上 ,进一步讨论亚洲夏季风爆发与当地对流层中上层东西向暖脊的经向位置变化关系。亚洲夏季风相继在孟加拉湾、南海和南亚爆发期间 ,除了对流层高、低空风场及深对流活动在季风爆发前后具有反相的变化以外 ,副热带高压脊面附近大气经向温度梯度亦具有明显的反相特征。对流层中上层 (2 0 0～ 5 0 0hPa)脊面附近建立的北暖南冷的温度结构 ,能够反映亚洲各季风区夏季风爆发共同的本质特征 ,根据季节转换的热力学基础 ,指出对流层中上层经向温度梯度作为度量季风爆发的指标是合理可行的。文中提出了以副热带高压脊面附近对流层中上层大气经向温度梯度作为表征季节转换的指数 ,给出了确定季节转换开始日期的具体定义以及历年季节转换日期序列 ,同时给出由85 0hPa纬向风和OLR表征的季风爆发日期序列。相关分析表明 ,85 0hPa纬向风只是个区域性指标 ,而南北温度梯度具有一定的普适性     

CMIP6模式水平分辨率对模拟我国西南地区夏季极端降水的影响评估

我国西南地区的地形地貌非常复杂,当前的气候模式对该地区降水状况特别是极端降水的模拟技巧是比较低的.本文基于台站和卫星观测的逐日降水资料以及欧洲中心第五代再分析(ERA5)降水资料,通过与CMIP6高分辨率模式比较计划(HighResMIP)中的12个模式高、低分辨率模拟结果的对比分析,评估了当前气候模式对西南地区夏季降...     

南海海气相互作用对热带气旋生成的影响——个例诊断

利用NCEP气候预报系统再分析资料（CFSR）和日本JRA-25再分析资料,对2010年西太平洋第5号热带风暴“蒲公英”的形成过程进行诊断,揭示南海海气相互作用对其初始涡旋生成的影响。分析表明,“蒲公英”的初始涡旋最早于8月20日00时出现在吕宋岛以东的对流层低层。西太平洋偏东风受到吕宋岛地形强迫可能是初始扰动形成的原因之一。在初始涡旋生成阶段,南海海域盛行较强的东南风,因风应力造成的Ekman输送导致南海中东部较暖海水流向吕宋岛附近,使得局地海温升高,自海洋向大气输送的感热通量增大。异常感热加热使其上空低层气压下降,近地层出现上升运动。但根据热力适应理论,感热加热随高度减小制造的低层负涡度不利于初始涡旋在异常感热加热区上空向高空进一步发展,可是在感热加热区东侧因涡度平流随高度增加,强迫出上升运动。该上升运动引起的凝结潜热释放,使得最大加热中心出现在对流层中层。于是,在对流层中低层非绝热加热随高度增加,制造正的相对涡度,使得初始涡旋在感热加热区的东侧生成,继而在对流层中低层增强。因此在初始涡旋增强阶段,凝结潜热加热及其对涡度的制造起主要作用。      

IMPACT OF AIR-SEA INTERACTION ON THE GENESIS OF TROPICAL INCIPIENT VORTEX OVER SOUTH CHINA SEA: A CASE STUDY

Based on 6-hourly sensible heat flux and latent heat flux from the NCEP Climate Forecast System Reanalysis (CFSR) and circulation data from the Japanese 25-year Reanalysis (JRA-25), the initial developing process of tropical cyclone Mindulle (1005) in 2010 has been diagnosed to reveal the impact of air-sea interaction over the South China Sea (SCS) on the genesis of its incipient vortex. The results show that the incipient vortex first occurred east of the Luzon Island on 0000 UTC 20 August, suggesting that the topographic forcing of the Luzon Island for easterly winds over the western Pacific might be one of the factors responsible for the formation of the incipient vortex. During the formation stage of the incipient vortex, strong southeasterlies over the SCS caused warm water of the middle and eastern SCS to flow toward the Luzon Island due to Ekman transport resulting from wind stress, leading to an increase of the sea surface temperature and sensible heat flux into the atmosphere. Although the anomalous sensible heating favored surface pressure to reduce, it was not conducive to the increase of local vorticity associated with the vortex above the heating area because, according to the atmospheric thermal adaptation theory, the anticyclonic vorticity would be created in the lower troposphere due to the decreased vertical gradient of the sensible heating. However, the ascending motions occurred over the eastern area of the anomalous sensible heating due to the augmentation of the vorticity advection with increasing height, causing water vapor to condense in the middle and upper troposphere. In turn, cyclonic vorticity was generated in the lower troposphere due to the increased vertical gradient of the condensation latent heating, resulting in the formation and further growth of the incipient vortex. Therefore, the vorticity creation due to the condensation heating played a dominant role during the subsequent enhancing stage of the incipient vortex.     

青藏高原热状况和海温异常对亚洲季风季节转换年际变化的影响

本文根据季节转换前后副高脊面附近经向温度梯度变号的本质,利用相关分析和合成分析等方法研究了季节转换年际变化与外部影响因子的联系. 结果表明,冬春季青藏高原热状况和ENSO（El Nio/Southern Oscillation,厄尔尼诺/南方涛动）是决定亚洲季风区季节转换年际变化的主要因素. 当冬、春季海温呈现El Nio异常时,Walker环流减弱,于是西太平洋暖池区对流活动受到抑制,而赤道东太平洋对流活动加强则强迫赤道印度洋地区产生绝热下沉运动,使得印度洋地区大气偏暖,结果增大了南北向温度梯度,季节转换往往偏晚. 反之,季节转换偏早. 初春高原上空对流层中高层的气温异常对于判断季节转换迟早有很好的指示意义.     

青藏高原低涡形成、发展和东移影响下游暴雨天气个例的位涡分析

2016年6月28日至7月1日在我国副热带地区发生了一次青藏高原低涡形成、发展及东传引发长江中下游地区暴雨天气的过程。本文利用MERRA2（Modern-Era Retrospective analysis for Research and Applications）再分析资料和TRMM（Tropical Rainfall Measurement Mission）降水资料对该过程进行位涡诊断分析。结果表明，夏季青藏高原地表加热具有强烈的日变化。高原地表加热由白天感热加热源到夜间辐射冷却源的转变直接影响高原上空非绝热加热率的垂直梯度，使高原近地层白天有位涡耗散，夜间有位涡制造，呈现明显的昼夜循环。当夜间的位涡制造异常强，以至不为白天的耗散所抵消时，通常位涡制造的昼夜循环被破坏，高原低涡形成，低涡周围随之出现降水。当低涡中心移动至高原东部时，中心附近伴随有强烈的降水，显著的凝结潜热加热使位涡中心增强，高原低涡进一步发展。随着低涡系统继续向东移出高原，长江中下游地区中高层出现位涡平流随高度增加的大尺度动力背景，上升运动发展，最终导致强降水发生。     

中期天气变化和中期预报

1引言从宏观上讲，全球大气运动是不可分割的统一整体运动。大气内部在各个纬带、各种尺度、各种频率的运动形式之间相互依存、相互制约、相互影响，按照大气动力学能量串级理论和能量频散原理，大尺度运动系统既可向小尺度系统转移能量，也可从小尺度系统获得能量。这样，各种尺度运动系统就会通过非线性相互作用引起大气环流形势的持续异常或急剧变化。天气、气候变化的直接原因是大气环流的变化或异常。从预报的角度讲，不同时效的预报要侧重考察相应长度的天气过程和长于预报时效的大型环流系统。天气尺度系统是短期预报的主要对象。而…     

我区近四十年短期气候预测的回顾和未来发展展望

我区近四十年短期气候预测的回顾和未来发展展望李敏志，毛江玉（内蒙古气象局）（内蒙古气象台）简单的回顾短期气候预测，通常也称做长期天气预报，是当今世界上的热门课题之一。它既有很大难度，又是服务上最迫切需要、最有社会经济效益的课题。近十几年来，无论是理论...     

CHARACTERISTICS OF THE LATENT HEAT DUE TO DIFFERENT CLOUD MICROPHYSICAL PROCESSES AND THEIR INFLUENCE ON AN AUTUMN HEAVY RAIN EVENT OVER HAINAN ISLAND

We analyzed cloud microphysical processes’ latent heat characteristics and their influence on an autumn heavy rain event over Hainan Island, China, using the mesoscale numerical model WRF and WRF-3DVAR system. We found that positive latent heat occurred far above the zero layer, while negative latent heat occurred mainly under the zero layer. There was substantially more positive latent heat than negative latent heat, and the condensation heating had the most important contribution to the latent heat increase. The processes of deposition, congelation, melting and evaporation were all characterized by weakening after their intensification; however, the variations in condensation and sublimation processes were relatively small. The main cloud microphysical processes for positive latent heat were condensation of water vapor into cloud water, the condensation of rain, and the deposition increase of cloud ice, snow and graupel. The main cloud microphysical processes for negative latent heat were the evaporation of rain, the melting and enhanced melting of graupel. The latent heat releases due to different cloud microphysical processes have a significant impact on the intensity of precipitation. Without the condensation and evaporation of rain, the total latent heating would decrease and the moisture variables and precipitation would reduce significantly. Without deposition and sublimation, the heating in high levels would decrease and the precipitation would reduce. Without congelation and melting, the latent heating would enhance in the low levels, and the precipitation would reduce.