一次超级单体的多普勒雷达特征分析

运用长沙多普勒天气雷达的基本反射率因子(R)、径向速度(V)、垂直积分液态含水量(VIL)、垂直剖面等产品,分析了2008年4月8日发生在湘东地区的一次超级单体强对流天气过程。分析表明:这次过程是一次典型的超级单体过程,在反射率因子上出现了钩状回波、三体散射回波、弱回波、高悬垂回波,相应的径向速度图上出现了持久的中气旋,风暴顶表现为强烈的辐散,降雹前相应的液态垂直累积含水量有一个跃增,这些多普勒雷达特征均为超级单体风暴预警提供了有利的临近预报因子。     

2002年6月21～24日梅雨锋暴雨过程中的水汽羽特征

利用GMS 5水汽图像和NCAR/NCEP再分析资料 ,分析了 2 0 0 2年 6月 2 1～ 2 4日长江中下游梅雨锋暴雨过程中水汽图像上水汽羽的特征。结果表明 :日平均水汽图像上显示了这次暴雨过程中对流层中上部的主要水汽型 ,是一条热带水汽羽从孟加拉湾经过青藏高原东部向偏东方向伸展至江淮地区 ,并与中纬度水汽羽相互作用 ,暴雨云团在热带水汽羽中连续生成。这条热带水汽羽是一条深厚暖湿输送带 ,反映了中高层水汽从孟加拉湾向长江下游的输送 ,以及通过大尺度上升运动造成的水汽自下而上的垂直输送 ,并且水汽羽与对流层上层的负涡度和正散度区域有很好的对应关系。水汽羽的北部边界附近的暗带与一条强涡度梯度和高空急流轴相关 ,具有明显的斜压性     

Observed monthly precipitation trends in China 1951–2002

Summary Monthly precipitation trends of 160 stations in China from 1951–2002 have been analysed and interpolated. The Mann-Kendall trend test was applied to examine the monthly precipitation data. Significant positive and negative trends at the 90, 95, and 99 percent confidence levels were detected for numerous stations. The number, distribution, and direction of the trends varied from month to month.The detected trends were spatially interpolated by applying the Inverse Distance Weighted (IDW) interpolation method. The spatial presentation of the detected precipitation trends gives a better understanding of climatic changes or variations in China during the last 50 years. This is especially the case for highlighting the spatial structure of precipitation trends.A clustering of trends is observed in certain months, including distinct trend belts especially in east and north-east China. Nevertheless, positive as well as negative monthly trends can be noted simultaneously in different areas. The spatial interpolation of precipitation trend analysis results is a useful approach to give further understanding of the regional pattern of precipitation trends in China.     

珠江流域1961-2007年气候变化及2011-2060年预估分析

 根据珠江流域1961-2007年气温、降水量观测资料和ECHAM5/MPI-OM模式2011-2060年预估结果,分析了流域过去47 a的气温和降水量变化,并预估未来50 a变化趋势。结果表明,在全球变暖的背景下,过去47 a温度呈上升趋势,约升高1.8℃。冬季增温最明显,夏季最弱。未来50 a流域温度仍呈上升趋势,A1B情景下升幅约1.9℃,并且年际变化增强。A2和B1两种排放情景下秋季升温最显著,冬季最弱,A1B排放情景与此相反。过去47 a秋季降水量呈减少趋势;春、夏、冬季和年降水量均呈增加趋势。未来50 a降水总体呈增加趋势,A1B排放情景降水增加最多,约为230 mm。A2、A1B和B1情景下降水季节分配未发生显著变化。年降水和冬季降水的年际变率增强,秋季减弱。     

Interdecadal variations of cold air activities in Northeast China during springtime

Based on the daily mean temperature data of CN05.2 from 1961 to 2012, cold events (CEs) are first divided into two categories according to their duration: strong cold events (SCEs) and weak cold events (WCEs). Then, the characteristics of CEs, SCEs, and WCEs during springtime are investigated. The results indicate that in the pre-1990s epoch, ENSO and Arctic Oscillation events in the previous winter are closely related to SCEs in the following spring. The multidecadal variations of CEs, SCEs, and WCEs are obvious. The intensity trend for SCEs is significantly negative, but it seems less apparent for WCEs. Further analysis reveals that when both SCEs and WCEs occur, a typical East Asian trough in the 850- hPa wind field, whose northwesterly wind component invades Northeast China (NEC) and causes freezing days, can be found in every decade. For the SCEs, a cold vortex, with its center located over Okhotsk and northeasterly current affecting NEC, is found as an additional feature. For the WCEs, the cold vortex is located in Karafuto and its northwesterly airflow intrudes into NEC. As for the difference between SCEs and WCEs, the northwestern flow is weaker while the northeastern counterpart is stronger during the SCEs, in all decades. In the Takaya–Nakamura flux and divergence fields, for the SCEs, a divergence center exists over NEC; and over its downstream regions, a stronger divergence center appears, not like a wave train. However, the opposite is the case for the WCEs; moreover, the wave train appears clearly during the WCEs, which means that the wave energy can propagate and dissipate more easily during WCEs.     

Interannual and interdecadal variations of the South Asian and western Pacific subtropical highs and their relationships with Asian-Pacific summer climate

In this study, interdecadal and interannual variations of the South Asian high (SAH) and the western Pacific subtropical high (WPSH), as well as their relationships with the summer climate over Asian and Pacific regions, are addressed. The variations of SAH and WPSH are objectively measured by the first singular value decomposition (SVD) mode of geopotential heights at the 100- and 500-hPa levels. The first SVD mode of summertime 100- and 500-hPa geopotential heights represents well the relationship between the variations of SAH and WPSH. Both SAH and WPSH exhibit large interannual variability and experienced an apparent long-term change in 1987. The WPSH intensifies and extends westward when SAH intensifies and extends eastward, and vice versa. The India?CBurma trough weakens when WPSH intensifies. The changes in SAH and WPSH at various levels are linked to broad-scale increases in tropical tropospheric temperature and geopotential height. When SAH and WPSH strengthen, monsoon flow becomes weaker over eastern Asia. In the meantime, precipitation decreases over eastern South China Sea, Philippines, the Philippine Sea and northeastern Asia, but increases over China, Korea, Japan and the ocean domain east of Japan. Similar features are mostly found on both interdecadal and interannual timescales, but are more evident on interannual timescale.     

2008年1月一次强雨雪过程的诊断分析

采用NCEP1°×1°客观再分析资料和常规观测资料,对2008年1月25—29日发生在长江中下游地区的强雨雪过程进行诊断分析,结果表明,低空急流与强雨雪有着密切关系,强雨雪的发生需具备一定的温度条件以及水汽场与动力场的耦合机制。对强雨雪过程的湿Q矢量诊断分析表明,700hPa湿Q矢量辐合区以及850hPa锋生函数正值区与强雨雪区对应较好,对雨雪天气的发生有着很好的指示意义。湿位涡特征分析表明,此次强雨雪过程发生在层结稳定的大气中且垂直涡度发展较强。     

东亚多卫星集成降水业务系统

静止气象卫星与极轨气象卫星的集成应用,能够充分发挥静止气象卫星与极轨气象卫星的各自优势。东亚多卫星集成降水业务系统采用拉格朗日集成算法,利用静止气象卫星的红外观测信息计算的红外冷云移动矢量,为极轨气象卫星微波降水的发展提供约束条件,实现了静止气象卫星红外观测信息与极轨气象卫星微波降水的集成,综合了两类卫星观测的优势。同时业务系统的设计考虑了多数据分级管理、多业务单元的协同工作和插件式的系统整体框架,为业务系统合理、快速处理多种来源的红外观测数据、微波降水数据,以及未来的数据更迭和算法更新提供了必要保障。     

Yangtze Delta floods and droughts of the last millennium: Abrupt changes and long term memory

Summary Climate variability and flood events in the Yangtze Delta, which is a low-lying terrain prone to flood hazards, storm tides and typhoons, are studied in terms of a trend and detrended fluctuation analysis of historical records. The data used in this paper were extracted from historical records such as local annuals and chronologies from 1000–1950 and supplemented by instrumental observations since 1950. The historical data includes frequencies of floods, droughts and maritime events on a decadal basis. Flood magnitudes increase during the transition from the medieval warm interval into the early Little Ice Age. Fluctuating climate changes of the Little Ice Age, which are characterised by arid climate events, are followed by wet and cold climate conditions with frequent flood hazards. For trend analysis, the Mann-Kendall test is applied to determine the changing trends of flood and drought frequency. Flood frequency during 1000–1950 shows a negative trend before 1600 A.D. and a positive trend thereafter; drought frequency increases after 1300. The detrended fluctuation analysis of the flood and drought frequencies reveals power law scaling up to centuries; this is related to long-term memory and is similar to the river Nile floods.     

珠江三角洲城市群污染综合指数预报的模式方法

应用全二阶矩表示的商斯烟团模式,重点引入烟团的合并与分解及各种清除过程,并利用广州热带模式（GZTM）所提供的华南地区细网格的三维数字化流场,来计算污染物浓度的长期变化。具体先模拟计算SO2、NOx、TSP的地面浓度日变化,通过求平均得到每种污染物的日均浓度,并和对应的污染物的日均浓度二级标准比较,得到每种污染物的污染指数Pi,最后求和得出污染综合指数P,从而对珠江三角洲地区的污染综合指数作出预报。