Time-frequency characteristics of the relationships between tropical Indo-Pacific SSTs

In this study, several advanced analysis methods are applied to understand the relationships between the Nino-3.4 sea surface temperatures （SST） and the SSTs related to the tropical Indian Ocean Dipole （IOD）. By analyzing a long data record, the authors focus on the time-frequency characteristics of these relationships, and of the structure of IOD. They also focus on the seasonal dependence of those characteristics in both time and frequency domains. Among the Nino-3.4 SST, IOD, and SSTs over the tropical western Indian Ocean （WIO） and eastern Indian Ocean （EIO）, the WIO SST has the strongest annual and semiannual oscillations. While the Nino-3.4 SST has large inter-annual variability that is only second to its annual variability, the IOD is characterized by the largest semiannual oscillation, which is even stronger than its annual oscillation. The IOD is strongly and stably related to the EIO SST in a wide range of frequency bands and in all seasons. However, it is less significantly related to the WIO SST in the boreal winter and spring. There exists a generally weak and unstable relationship between the WIO and EIO SSTs, especially in the biennial and higher frequency bands. The relationship is especially weak in summer and fall, when IOD is apparent, but appears highly positive in winter and spring, when the IOD is unimportantly weak and even disappears. This feature reflects a caution in the definition and application of IOD. The Nino-3.4 SST has a strong positive relationship with the WIO SST in all seasons, mainly in the biennial and longer frequency bands. However, it shows no significant relationship with the EIO SST in summer and fall, and with IOD in winter and spring.     

COMPARISON OF THE EFFECTS OF ANOMALOUS CONVECTIVE ACTIVITIES IN THE TROPICAL WESTERN PACIFIC ON TWO PERSISTENT HEAVY RAIN EVENTS IN SOUTH CHINA

The different effects of anomalous convective activities in the tropical western Pacific on two persistent heavy rain events in South China in 2005 and 2006 have been compared in this study. The dataused consist of NOAA Outgoing Longwave Radiation (OLR) data, the NCEP-NCAR reanalysis and precipitation from meteorological stations in South China. Results show that the persistent heavy rain in 2005 was related to the 10-25-day westward propagation of convective activities in the tropical western Pacific from about 150 °E. The physical mechanism is interpreted as a Gill-type response of subtropical anticyclone westward extension during weak convective activities period over the Philippine Sea. Our researches also show that the persistent heavy rain in 2006 has longer period than that in 2005, and the subtropical anticyclone persists westward in the earlier summer which is possibly related to the lasting anomalous strong convective motion in the southern branch of Intertropical Convergence Zone (ITCZ) in the tropic western Pacific. The anomalous convective activities affect the local Hadley circulation over the western Pacific with anomalous ascending motion south of the equator and anomalous descend motion north of it, in favor of the westward extension of the subtropical anticyclone for a long time. Comparison between the two persistent heavy rain events indicates different physical effects of convective activities in the tropical western Pacific, though both effects are helpful to the subtropical anticyclone westward extension as a common character of large-scale circulation backgrounds for persistent heavy rain events in South China.     

Heavy Rainfall Associated with a Monsoon Depression in South China: Structure Analysis

A heavy rainfall associated with the deepening of a monsoon depression happened in the summer of 2005. This process was first diagnostically analyzed and the 3D structure of the monsoon depression was discussed~ then this structure was compared with those of the monsoon depression in South Asia and the low vortex in the Meiyu front. The results showed that the heavy rainfall directly resulted from a monsoon depression in South China~ and the large-scale environment provided a favorable background for the deepening of the monsoon depression. The 3D structure of the monsoon depression was as follows. In the horizontal direction, there existed a convective cloud band to the south of the monsoon depression, which lay in a convectively instable area, with a relatively strong ascending motion in the mid and low levels of the troposphere, and the ascending motion matched well with a moist tongue, a convergence area, and a band of positive vorticity in the mid and low levels of the troposphere. In the vertical direction, the depression had an obviously cyclonic circulation in the mid and low levels of the troposphere, but no circulation from above 300 hPa. The monsoon depression corresponded to convergence and positive vorticity in the low levels, but to divergence and negative vorticity in the upper levels. The upward draft of the depression could reach the upper levels of the troposphere in the west of the depression, while the descending motion lay in the east. There was a low-level jet to the south of the depression, while the upper-level jet was not obvious. The depression was vertically warm in the upper levels and cold in the low levels, and the axis of the depression tilted southeastward with height, whose characteristics were different not only from the monsoon depression in South Asia but also from the low vortex in the Meiyu front.     

La Nia年冬季亚洲中高纬环流与我国南方降雪异常关系

2007/2008年冬季,赤道中东太平洋形成了一次中等强度的La Nia事件。本文根据NCAR/NCEP再分析资料,探讨La Nia气候背景下亚洲中高纬大气环流及南亚上空南支槽强度与我国南方（25～35°N,110～125°E）多雪、少雪以及2008年1月我国南方大范围低温雨雪冰冻灾害的关系。分析指出,La Nia气候背景下,500 hPa高度场亚洲高纬位势高度偏高易出现阻塞型,当乌拉尔山阻塞高压强度、位置比鄂霍次克阻塞高压偏强、偏北时,入侵我国南方的偏北气流主要来自乌拉尔山地区,南方偏冷（距平达-40 ℃）多雪;当鄂霍次克阻塞高压强度、位置比乌拉尔山阻塞高压偏强、偏北,入侵我国南方的偏北气流主要来自鄂霍次克海地区,南方偏暖（距平达10 ℃）少雪。2008年1月500 hPa高度上亚洲高纬乌拉尔山阻高偏北、强度偏强（正距平中心值达120 gpm）,入侵我国南方的2支偏北气流都来自乌拉尔山地区,南方出现了低温（温度距平达-40 ℃）雨雪冰冻天气;分析指出,200 hPa高度场南亚地区南支槽的强弱对我国南方降雪多寡有重要影响。     

中国夏季极端酷暑的气候统计和趋势分析

Based on the daily maximum air temperature data from 300 stations in China from 1958 to 2008, the climatological distribution of the number of days with high temperature extremes （HTEs, maximum temperatures higher than 35℃） are studied with a focus on the long-term trends. Although the number of HTE days display well-defined sandwich spatial structures with significant decreasing trends in central China and increasing trends in northern China and southern China, the authors show that the decrease of HTE days in central China occurs mainly in the early period before the 1980s, and a significant increase of HTE days dominates most of the stations after the 1980s. The authors also reveal that there is a jump-like acceleration in the number of HTE days at most stations across China since the mid 1990s, especially in South China, East China, North China, and northwest China.     

THE DIAGNOSTIC ANALYSIS OF THE RAPID CHANGE IN TROPICAL CYCLONES INTENSITY BEFORE LANDFALL IN SOUTH CHINA

1 INTRODUCTION Sudden changes in the intensity of the tropical cyclone (TC) are a difficult issue to be tackled.Few of the previous works dealt with the characteristics of large-scale circulation background of TCs that experience sudden intensity changes prior to landfall. Studies that do address the issue are only case-based, which do not isolate large-scale circulation background common to all cases,whether it be favorable or not. By diagnostically studying large-scale characteristics of two categories of TCs, one intensifying and the other weakening, suddenly, before making landfall on the area of South China, the current work attempts to support the prediction of TC intensity.     

用于ENSO预报的计算机模拟

ENSO(厄尔尼诺/南方涛动)现象是全球气候中最大的年际变动.由于ENSO对区域和全球气候及经济都有重大影响,因此近年来已引起了人们广泛的关注.为期10年的TOGA(热带海洋全球大气)计划的实施,已使监测和预报ENSO成为现实.在TOGA计划实施中建立的观测网,如在太平洋的热带大气海洋观测浮标阵,可实时监测ENSO,并为模式的验证和初始化提供资料.     

让雄伟的长城走向世界把古老的长城留给子孙

今年9月．是邓小平同志“爱我中华．修我长城”题词发表二十周年．今天,我们大家相聚在一起．召开这个纪念大会．很有意义。首先．我想在这里就小平同志这8个宇题词的深刻内涵谈一谈自己的理解。我认为这个题词不仅仅是为长城修缮题写的,前提是“爱我中华”。因为爱我中华．所以才修长城．用对长城的保护来体现对中华的热爱。     

詹公天佑 长城保护的先驱

2009年10月11日,中华人比共和国60周年国庆。 2009年10月2日,京张铁路通车典礼百年纪念。     

虚拟环境下长城文化景观的综合展示设计

长城是中华文明的厚重载体,更是享誉全球的世界文化遗产。如何利用现代新技术让更多人更全面更深入地了解长城、认识长城、感受长城,是长城保护与宣传的重要内容。本文提出了一种利用地理信息、互联网、全景摄影、多媒体和虚拟场景等多种技术,综合展示长城文化遗产、历史遗迹、环境景观和文化价值等的展示方案,为观众提供沉浸式的体验,推进长城文化宣传和展示,为长城资源旅游推介、价值探索、保护利用探讨新的模式。