低涡和副热带高压共同影响下的暴雨落区分析

应用常规观测资料和NCEP 1°×1°再分析资料,分析低涡和副热带高压共同影响下的暴雨过程,发现暴雨落区并不与低涡位置及路径一致,因而不能简单的按其位置和路径预报暴雨落区,应着眼于暴雨发生的物理机理,注意分析影响系统的空间结构、发展阶段和地面形势的演变特征。在有锋面系统影响时,初始对流往往由锋面触发,因此,暴雨的第一落区在锋面附近。冷锋触发的暖区暴雨随后出现,不需强的动力辐合条件,可能远离低涡中心,而是位于副热带高压边缘的高温湿舌内。另外,应密切关注周边初生的对流云团及其移入时造成的暴雨。     

CORRELATION ANALYSIS OF THE WESTERN PACIFIC SUBTROPICAL HIGH AND EASTERN ASIAN SUMMER MONSOON SYSTEM BASED ON FUZZY SYSTEMS AND DYNAMICAL MODEL INVERSION FORECAST

Based on the adaptive network fuzzy inference system (ANFIS), methods to filter out the noise of impact factors from the main signal are discussed. Focusing on the abnormal weather conditions in 2010, we use the delay-relevant method to analyze the five members of the summer monsoon system that had the largest effect on the subtropical high anomalies from the observational data. ANFIS is suitable for research and simulation of subtropical highs that are difficult to describe accurately with dynamics, allowing the effect of five factors on the subtropical high anomalies to be examined. Our results show that the Mascarene cold high, the Indian monsoon latent heat flux, and the South China Sea monsoon trough had the largest effect on the subtropical high anomalies. Diagnostic analysis, with genetic algorithms (GA) and dynamical reconstruction theory, reconstructed the nonlinear dynamical model of the subtropical high and its main factors objectively and accurately from the sequence of observations in 2010. Furthermore, a dynamically extended forecast experiment is performed. The forecasts for the subtropical high area index, the Mascarene cold high index, the Indian monsoon latent heat flux, and the South China Sea monsoon trough index all show a strong short-term effect over less than 25 days. The forecasting trend is accurate, and the error rate is no more than 7%. Our results provide new insight and methods for research on the association between the western Pacific subtropical high and the East Asian summer monsoon system, and for the prediction of the western Pacific subtropical high index.     

The Influence of Plantation on Soil Carbon and Nutrients: Focusing on Tibetan Artificial Forests

As terrestrial ecosystem carbon (C) sinks, plantation ecosystems play essential roles in species diversity protection, resource supply and climate change. Artificial afforestation is of great important in improving the ecological condition, economic development and production in Tibet. Forests can improve soil property changes, yet the understanding of how plantations influence soil C and nutrient conditions in Tibet is still insufficient. This review combines with previous studies to explore the characteristics of soil nutrients, involving nitrogen (N) and phosphorus (P) on Tibetan poplar plantations. Generally, plantations have better abilities in improving the soil C and N cycles, and enhancing the soil stability. In this review, we further analyze the factors, including the modality of land-use, afforested period, tree species, climate factors and soil properties, which may affect the soil C and nutrients. (1) The patterns of land-use affect the accumulation of soil organic matter, thus influence the accumulation of soil C and nutrients; (2) Soil C and N increase with the years of artificial forests, while soil P is on the contrary; (3) The effects of different tree species on soil C and nutrients vary widely; (4) In terms of climate, the C sink of Tibetan plantation soil is most likely to be affected by precipitation, while the nutrient is more likely to be influenced by temperature; (5) Among soil properties, the most related factor to C is soil texture. Furthermore, our review pointed out that future research on soil ecological functions should be focused on soil microbes on Tibet plantation. At the end, we concluded three major challenges for the future research. Therefore, this review contributes to a better understand the effects of plantation on soil C and nutrients on the Tibetan Plateau.     

西北太平洋累积气旋能量的年代际变化

利用1949—2011年CMA-STI热带气旋最佳路径数据集,分析了西北太平洋累积气旋能量(ACE)的年代际变化特征。结果表明,西北太平洋热带气旋(ACE)的年代际变化主要分为1957—1967高值期、1976—1986过渡期和1998—2008低值期。其中强热带风暴(STS)、台风(TY)和超强台风(SuperTY),特别超强台风是决定成分。副热带高压偏弱,垂直风切变偏小,低纬度低空正涡度异常偏东以及低纬度海表面温度(SST)正异常偏东等背景场的年代际特征,有利于形成ACE的年代高值期。     

Variability of tropical cyclone in high frequent occurrence regions over the western North Pacific

In this study, three high frequent occurrence regions of tropical cyclones(TCs), i.e., the northern South China Sea(the region S), the south Philippine Sea(the region P) and the region east of Taiwan Island(the region E), are defined with frequency of TC's occurrence at each grid for a 45-year period(1965–2009), where the frequency of occurrence(FO) of TCs is triple the mean value of the whole western North Pacific. Over the region S, there are decreasing trends in the FO of TCs, the number of TCs' tracks going though this region and the number of TCs' genesis in this region. Over the region P, the FO and tracks demonstrate decadal variation with periods of 10–12 year, while over the region E, a significant 4–5 years' oscillation appears in both FO and tracks. It is demonstrated that the differences of TCs' variation in these three different regions are mainly caused by the variation of the Western Pacific Subtropical High(WPSH) at different time scales. The westward shift of WPSH is responsible for the northwesterly anomaly over the region S which inhibits westward TC movement into the region S. On the decadal timescale, the WPSH stretches northwestward because of the anomalous anticyclone over the northwestern part of the region P, and steers more TCs reaching the region P in the greater FO years of the region P. The retreating of the WPSH on the interannual time scale is the main reason for the FO's oscillation over the region E.     

两次副高边缘特大暴雨对比分析

利用常规资料、地面加密自动观测资料、NCEP/NCAR的1°×1°每6h再分析资料及多普勒雷达资料,对2011年6月16日（简称6.16过程）及2008年7月31日（简称7.31过程）发生在粤东南两次副高边缘特大暴雨进行对比分析。结果表明：6.16过程主要是受高空短波槽和偏南风急流共同影响而产生的,较厚的暖云层、深厚的湿层等使该过程降水范围更广;7.31过程主要是受对流中层扰动诱发产生的,为局地性强降水。雷达回波均表现为强的反射率因子,回波发展迅速且移动缓慢;6.16过程回波图上出现有界弱回波区（BWER）等超级单体风暴特征。     

The Relationship between the East Asian Subtropical Westerly Jet and Summer Precipitation over East Asia as Simulated by the IAP AGCM4.0

Based on a 30-year Atmospheric Model Intercomparison Project（AMIP） simulation using IAP AGCM4.0, the relationship between the East Asian subtropical westerly jet（EASWJ） and summer precipitation over East Asia has been investigated, and compared with observation. It was found the meridional displacement of the EASWJ has a closer relationship with the precipitation over East Asia both from model simulation and observation, with an anomalous southward shift of EASWJ being conducive to rainfall over the Yangtze-Huaihe River Valley（YHRV）, and an anomalous northward shift resulting in less rainfall over the YHRV. However, the simulated precipitation anomalies were found to be weaker than observed from the composite analysis, and this would be related to the weakly reproduced mid-upper-level convergence in the mid-high latitudes and ascending motion in the lower latitudes.     

江淮流域夏季降水的准两年振荡特征及其关联因子分析

利用1951—2010年我国江淮流域11个测站夏季(6—8月)降水资料和NCAR提供的北半球月平均海平面气压场资料以及相关的西太平洋副高指数资料,采用Morlet小波变换、交叉小波变换及相关分析等方法讨论了降水准两年振荡现象的年际变化规律及其与东亚夏季风、副高的关系。结果表明,准两年振荡分量在江淮地区夏季降水场的年际振荡中十分重要,且经历了由强到弱再到强的变化过程;同时降水与夏季风强度及副高脊线位置的准两年变化均存在较好的同期相关,彼此间的相互影响还体现在年际尺度上,并分别在4 a和1 a时间尺度上有明显的滞后、超前关系。     

The response of the East Asian summer monsoon to strong tropical volcanic eruptions

A 600-year integration performed with the Bergen Climate Model and National Centers for Environmental Prediction/National Center for Atmospheric Research （NCEP/NCAR） reanalysis data were used to investigate the impact of strong tropical volcanic eruptions on the East Asian summer monsoon （EASM） and EASM rainfall.Both the simulation and NCEP/NCAR reanalysis data show a weakening of the EASM in strong eruption years.The model simulation suggests that North and South China experience droughts and the Yangtze-Huaihe River Valley experiences floods during eruption years.In response to strong tropical volcanic eruptions,the meridional air temperature gradient in the upper troposphere is enhanced,which leads to a southward shift and an increase of the East Asian subtropical westerly jet stream （EASWJ）.At the same time,the land-sea thermal contrast between the Asian land mass and Northwest Pacific Ocean is weakened.The southward shift and increase of the EASWJ and reduction of the land-sea thermal contrast all contribute to a weakening of the EASM and EASM rainfall anomaly.     

华南亚热带中部山地垂直植被带表土孢粉散布规律与气候相关性

孢粉学分析是古生态与古气候定量重建的重要指标之一,建立现代表土孢粉与植被之间的定量关系是利用地层孢粉准确解释古生态与古气候变化的前提条件。基于华南亚热带中部山地垂直植被带采集的113个现代表土和苔藓孢粉样品,采用典型对应分析方法（Canonical Correspondence Analysis, CCA）,探讨研究区不同海拔表土孢粉种类散布规律与气候因子之间的关系。主要得出以下结论：1）华南亚热带中部地区现代表土孢粉组合中乔木类以壳斗科栲属、常绿栎属、松属、杉木属和大戟科等种类占绝对优势,草本植物花粉以禾本科、蒿属、菊科和莎草科为主,蕨类孢子以三缝孢子、芒萁属、水龙骨科和单缝孢子为主。2）研究区低海拔至高海拔的孢粉组合呈现以下变化规律：低海拔地区（0~702 m）孢粉组合以栲属、常绿栎属、松属、野桐属、枫香属、茜草科以及禾本科花粉为主;中海拔（703~1 299 m）山坡的优势孢粉为栲属、杉木属、松属和常绿栎属;高海拔地区（1 300~1 600 m）以栲属、常绿栎属、水青冈属、杜鹃花科以及松属花粉最为丰富,表土孢粉组合变化过程与现代植被群落优势种类有较好的一致性。3）CCA分析结果显示,控制研究区域主要表土孢粉分布的气候因子为年均降雨量（MAP）、最热月降水（Mpwa）和最热月温度（Mtwa）;松属、杉木属、栲属、常绿栎属、山茶科、水青冈属和落叶栎属等高百分比含量的花粉所对应的气候特征较为明显。4）低海拔地区的优势种属栲属、常绿栎属等以及相对高海拔的松属、杉木属和水青冈属等能较好地反映气候因子对植被空间分布的影响。因此,文章揭示了华南亚热带中部地区表土孢粉在垂直植被带上具有明显差异,孢粉散布规律可能与研究区植被组成、生境、花粉形态与传播媒介等因素有关,能为利用化石孢粉数据进行古生态与古气候定量重建提供参考资料。