CHARACTERIZATION AND CAUSAL ANALYSIS OF TEMPORAL AND SPATIAL VARIATION IN DRY-WET CONDITIONS IN AUTUMN IN SOUTHWEST CHINA

Based on the daily precipitation and temperature data of 97 stations in Southwest China(SW China) from1960 to 2009, a dry-wet index is calculated. The spatiotemporal variation characteristics of dry-wet conditions,precipitation and temperature are studied. Then the abnormal atmospheric circulation characteristics are discussed using reanalysis data. The results show that SW China has exhibited an overall trend of autumnal drought since the late1980 s, and this drought trend became more significant early in the 2000 s, especially in the eastern SW China. Autumnal dry-wet variation in southwestern China showed two major modes: consistent change across the entire region and opposing changes in the eastern and western regions. The spatial distribution of dry-wet anomalies was more significantly affected by precipitation, while temporal variation in dry-wet conditions was more strongly influenced by temperature. The former mode is affected by the anomalies of the precedent SST near the Western Pacific Warm Pool,the Western Pacific Subtropical High, the East Asian Trough and the South Trough. The latter mode is related to the wind anomalies in the eastern SW China and the vertical movement in the western and eastern SW China. These are the main influencing factors for the autumn dry-wet variation in SW China, which are of great significance to the prediction of drought.

Genetic Analysis of Heading Date of Japonica Rice Cultivars in Southwest China

Heading date of 26 native japonica rice cultivars in southwest China was investigated,and their basic vegetative growth(BVG),photoperiod-sensitivity(PS) and temperature-sensitivity(TS) were analyzed under artificial short-day and natural long-day conditions in Nanjing,as well as artificial high-temperature and natural low-temperature conditions in winter in Hainan.The results showed that the PS and TS varied among different cultivars.The BVG of all the japonica cultivars was well situated,but differed within cultivars.Regression analysis showed a significant correlation between heading date and PS,indicating that PS was the main factor affecting heading date of japonica cultivars in southwest China.Genetic analysis was conducted on these 26 cultivars using a set of heading date near isogenic lines as test lines.All the japonica cultivars carried the dominant early-heading gene Ef-1 or Ef-1t,and most of these cultivars carried the dominant photoperiod sensitivity allele E1 or E1t,the PS of which was slightly weaker than E1.For the Se-1 locus,these cultivars mainly carried recessive photoperiod insensitivity gene Se-1e.In addition,the PS of 22 japonica cultivars could be repressed or weakened by the recessive allele hd2,inhibiting the expression of E1 and Se-1.These results indicated that the genotypes of heading date determined different PS and well situated BVG in japonica rice cultivars in southwest China.

Climatic Analysis of Continuous Rain in Southwest of Shandong

The continuous rain data from 1961 to 2007 in Heze city was analyzed in this paper.The results showed that continuous rain increased from north to south.Continuous rain processes took place most frequently in summer,next in autumn,and the least in winter.Using wavelet to analyze the sequence of seasonal and annual continuous rain,it had a 5 years cycle oscillation at 2Y(year) level and a 20 years cycle oscillation at 10Y level.An abrupt climate change of continuous rain took place in 1986.Continuous rain was in a more period from 2001 to 2010 and would decrease gradually within the period.

Geotechnical properties and stability of the submarine canyon in the northern South China Sea

The upper part of the continental slope in the northern South China Sea is prone to submarine landslide disasters,especially in submarine canyons.This work studies borehole sediments,discusses geotechnical properties of sediments,and evaluates sediment stability in the study area.The results show that sediment shear strength increases with increasing depth,with good linear correlation.Variations in shear strength of sediments with burial depth have a significantly greater rate of change in the canyon head and middle part than those in the canyon bottom.For sediments at the same burial depth,shear strength gradually increased and then decreased from the head to the bottom of the canyon,and has no obvious correlation with the slope angle of the sampling site.Under static conditions,the critical equilibrium slope angle of the sediments in the middle part of the canyon is 10°to 12°,and the critical slope angle in the head and the bottom of the canyon is 7°.The results indicate that potential landslide hazard areas are mainly distributed in distinct spots or narrow strips on the canyon walls where there are high slope angles.

Role of hydro-geochemical functions on karst critical zone hydrology for sustainability of water resources and ecology in Southwest China

Focusing on sustainability of water resources and ecology in the complex karst critical zone, we illustrated functions of the hydro-geochemical analysis on hydrology from the aspects of connection and interaction among hydrology–vegetation–soils/rock fractures along the karst subsurface profile. We reviewed isotopic and geochemical interpretations on tracing water sources for plant uptake, quantifying watershed outlet flow composition and residence times, and evaluating long-term evolution among climate–landscape–hydrology in the karst critical zone. In this paper, the application of the hydro-geochemical analysis on the above aspects in the karst areas of southwest China was summarized.

Comparative Analysis of Two Rainstorms in the Southwest of Hunan Province

Using NCEP 1° × 1° reanalysis data within 6 h, conventional observational data, data from regional automatic rainfall stations, satellite cloud pictures and Doppler radar data, we compared the physical conditions, dynamic and thermodynamic characteristics of two rainstorms in the southwest of Hunan Province on May 12 and June 15 in 2011. The results showed that the first process was triggered by strong cold air under unstable potential, while the second process was caused by shear line appearing from the east; during the first process, cold air divided into many parts and moved towards south, rainfall was uniform and lasted for a long time, while rainfall was relatively concentrated and strong, and lasted for a short time during the second process; the peak of K index appeared only during the second process; no sign of heavy rainfall was found from satellite cloud pictures and radar echo pictures during the first process, while obvious cloud cluster and echo ribbons could be found from satellite cloud pictures and radar echo pictures during the second process, which were the sign of heavy rainfall; slow movement of echo or little movement resulted in the second rainstorm, and constant echo intensity was the main reason for the occurrence of the second rainstorm. In addition, there was low-level southwest jet during the two processes, which provided favorable conditions for the transportation of water vapor and energy during the two processes. However, there was a great difference between the two rainstorms in the intensity and thickness of low-level jet, that is, the intensity and thickness of low-level jet during the first process were obviously weaker than these during the second process.

Current Stress State on Part of Active Fault Planes in Southwest China and Its Relationship with Unstable Deformation of Faults

In this paper,a comprehensive analysis was made for Southwest China using the data of in situ stress measurements,the geometric elements of main active faults,the data of micro-displacements and the energy release of Ms≥5.0 earthquakes near those active faults.The result shows that in measuring regions with lower earthquake energy release and smaller micro-displacement of faults,the value would be higher,and vice versa.

Deep learning-based subseasonal to seasonal precipitation prediction in southwest China:Algorithm comparison and sensitivity to input features

The prediction of precipitation at subseasonal to seasonal(S2S)timescales remains an enormous challenge because of the gap between weather and climate predictions.This study compares three deep learning algorithms,namely,the long short-term memory recurrent(LSTM),gated recurrent unit(GRU),and recurrent neural network(RNN),and selects the optimal algorithm to establish an S2S precipitation prediction model.The models were evaluated in four subregions of the Sichuan Province:the Plateau,Valley,eastern Basin,and western Basin.The results showed that the RNN model had better performance than the LSTM and GRU models.This could be because the RNN model had an advantage over the LSTM model in the transformation of climate indices with positive and negative variations.In the validation of test datasets,the RNN model successfully predicted the precipitation trend in most years during the wet season(May-October).The RNN model had a lower prediction bias(within±10%),higher sign accuracy of the precipitation trend(~88.95%),and greater accuracy of the maximum precipitation month(>0.85).For the prediction of different lead times,the RNN model was able to provide a stable trend prediction for summer precipitation,and the time correlation coefficient score was higher than that of the National Climate Center of China.Furthermore,this study proposed a method to measure the sensitivity of the RNN model to different input features,which may provide unprecedented insights into the nonlinear relationship and complicated feedback process among climate systems.The results of the sensitivity distribution are as follows.First,the Niño 4 and Niño 3.4 indices were equally important for the prediction of wet season precipitation.Second,the sensitivity of the snow cover on the Tibetan Plateau was higher than that in the Northern Hemisphere.Third,an opposite sensitivity appeared in two different patterns of the Indian Ocean and sea ice concentrations in the Arctic and the Barents Sea.

Emergency road network structure and planning optimization in mountainous regions in Southwest China under earthquake scenarios

Emergency road networks(ERNs),an important part of local disaster prevention systems,can provide security to residents and their property.Exploring the ERNs structure is of great significance in terms of promoting disaster prevention and establishing road safety in dangerous mountainous areas.This study considered the ERNs of the Kangding section of the Dadu River Basin as the area for a case study.Complex Network Analysis was used to examine the relationship between the four characteristic indicators of mountain roads and the degree of earthquake impacts under the Lushan,Wenchuan,and Kangding Earthquake scenarios.Based on the analysis results,the southwest mountain road network was evaluated;then,computer simulations were used to evaluate the structural changes in the road network after index changes.The network was optimized,and the corresponding emergency avoidance network was proposed to provide a reference for the establishment of the mountainous ERN.The results show that the overall completeness of the mountainous ERNs in Southwest China is poor and prone to traffic accidents.Moreover,the local stability is poor,and the network is susceptible to natural hazards.The overall structure of the road network is balanced,but that of certain road sections is not.Road sections with different attributes present a“gathering-scattering”spatial distribution,i.e,some sections are clustered together while others are far apart.Accordingly,a planning optimization strategy is proposed to better understand the complexity and systematic nature of the mountainous ERN as a whole and to provide a reference for disaster prevention and mitigation planning in mountainous regions in Southwest China.

Characteristics of super drought in Southwest China and the associated compounding effect of multiscalar anomalies

In recent decades,Southwest China(SWC)has suffered from frequent super droughts,leading to severe economic losses and ecological degradation.This study investigates the characteristics of super droughts in SWC during 1961-2022,reveals the compounding effect of multiscalar anomalies,and explores the plausible atmospheric circulation mechanisms responsible.The nature of super drought is a compound drought caused by the superposition of extreme drought events across multiple time scales.By contrasting the typical drought cases in 2006 and 2022,the decisive role of multiscalar drought compounding is confirmed.Based on the Comprehensive Multiscalar Index(CMI),multiple super drought events in SWC were identified to be temporally clustered during 2006-2014.Among them,the decadal background of enhanced evaporation and precipitation deficit at long time scales is a necessary condition for shaping the overall pattern of super droughts,while the precipitation and evaporation anomalies at short time scales trigger the outbreak of super droughts,determining the exact timing of occurrence.These events include August-September 2006,November 2009 to May 2010,July-October 2011,April-May 2012,January-April 2013,etc.Statistical results suggest that the contribution of superposed precipitation anomalies to super drought is 2.4 times that of evaporation.As regards the circulation mechanisms affecting multiscalar precipitation,the anomalous spatial patterns at short-term and long-term scales are similar,featuring the cyclonic circulation over the South China Sea and the northeasterly wind anomalies together with the subsidence center over SWC.During 2006-2014,the possible causes for the cross-seasonal persistent precipitation reduction in SWC are the extreme negative phase of the Pacific Decadal Oscillation(PDO)in the North Pacific as well as the pronounced warming of the warm pool in the western Pacific.The key dynamic processes are outlined as follows.On the one hand,the negative PDO phase generates anomalous anticyclonic circulation in the North Pacific,with the northeasterly winds on its southwest flank extending to Southeast Asia,hindering moisture transport into SWC.On the other hand,the warming of the warm pool excites anomalous cyclonic circulation to its northwest,also giving rise to northeasterly wind anomalies over SWC.Meanwhile,the ascending motion over the warm pool region diverges at upper levels with outflows converging aloft over SWC,which further induces compensating downward motion there.The combined effect of the above two remote forcings establishes a climatic background state unfavorable for precipitation over SWC at long time scales,thus constituting a crucial prerequisite for the superimposition of short-term precipitation anomalies to develop into super droughts.

Quantitative analysis of planation surfaces of the upper Yangtze River in the Sichuan-Yunnan Region, Southwest China

Identification of the planation surfaces (PSs)is key for utilizing them as a reference in studying the long- term geomorphological evolution of the Upper Yangtze River Basin in the Sichuan-Yurman region,Southwest China.Using a combined method of DEM-based fuzzy logic and topographic and fiver profiles analysis and based on a comprehensive analysis of four morphometfic parameters:slope,curvature,terrain raggedness index, and relative height,we established the relevant fuzzy membership functions,and then calculated the membership degree (MD)of the study area.Results show that patches with a MD>80% and an area>0.4 km^2 correspond well to the results of Google Earth and field investigation,representing the PS remnants.They consist of 1764 patches with an altitude,area,mean slope,and relief of mostly 2000-2500 m above sea level (asl),0-10 km^2,4°-9°,0-500 m,respectively,covering 9.2% of the study area's landscape,dipping to southeast,decreasing progressively from northwest to southeast in altitude,and with no clear relation between each patch's altitude and slope,or relief.All these results indicate that they are remnants of once regionally continuous PSs which were deformed by both the lower crust flow and the faults in upper crust,and dissected by the network of Upper Yangtze River.Additionally,topographic and river profiles analysis show that three PSs (PS1-PS3)well developed along the main valleys in the Yongren-Huili region, indicating several phases of uplift then planation during the Late Cenozoic era.Based on the incision amount deduced from projection of relict river profiles on PSs, together with erosion rates,breakup times of the PS 1,PS2,and PS3 were estimated to be 3.47 Ma,2.19 Ma,and 1.45 Ma,respectively,indicating appearance of modem Upper Yangtze River valley started between the Pliocene to early Pleistocene.

Prediction for Potential Landslide Zones Using Seismic Amplitude in Liwan Gas Field, Northern South China Sea

The Liwan(Lw) gas field located in the northern slope of the South China Sea(SCS) is extremely complex for its seafloor topograghy, which is a huge challenge for the safety of subsea facilities. It is economically impractical to obtain parameters for risk assessment of slope stability through a large amount of sampling over the whole field. The linkage between soil shear strength and seabed peak amplitude derived from 2D/3D seismic data is helpful for understanding the regional slope-instability risk. In this paper, the relationships among seabed peak, acoustic impedance and shear strength of shallow soil in the study area were discussed based on statistical analysis results. We obtained a similar relationship to that obtained in other deep-water areas. There is a positive correlation between seabed peak amplitude and acoustic impedance and an exponential relationship between acoustic impedance and shear strength of sediment. The acoustic impedance is the key factor linking the seismic amplitude and shear strength. Infinite slope stability analysis results indicate the areas have a high potential of shallow landslide on slopes exceeding 15? when the thickness of loose sediments exceeds 8 m in the Lw gas field. Our prediction shows that they are mainly located in the heads and walls of submarine canyons.

Quantitative Risk Analysis of a Rainfall-Induced Complex Landslide in Wanzhou County,Three Gorges Reservoir,China

On 4 April 2013,a 1.5 million cubic meter landslide occurred in Sunjia Town,Wanzhou County,Three Gorges Reservoir,China.After initiation,the Sunjia landslide traveled about 30 m toward the northeast and destroyed most of the infrastructure in its path.The landslide was triggered by heavy rainfall and previous slope excavations,but this slope also displayed a complicated failure process:the overlying earth slope first deformed and then induced sliding along underlying rock surfaces.Surface displacements that resulted from continuous creeping of the post-event slope were observed by an emergency monitoring system that revealed the disequilibrium state of the slope.To discuss the stability and future movements of the remaining unstable debris deposits,we developed a geotechnical model of the post-slide slope,calculated how it can slide again in an extreme rainfall scenario,and estimated the potential runout distance using the Tsunami Squares method.We then estimated the number of people and the value of the infrastructure threatened by this potential landslide.Lastly,we analyzed the vulnerability of elements at risk and quantitatively evaluated the hazard risk associated with the most dangerous scenario.This quantitative risk analysis provides a better understanding of,and technical routes for,hazard mitigation of rainfallinduced complex landslides.

西南地区东部前后冬气温反位相异常特征及成因分析

利用西南地区东部台站观测和ERA5再分析等资料,分析该地区冬季气温前后冬反位相异常转折(以下简称异常转折)特征及其成因。结果表明:该地区冬季气温在2000年以后易出现前冷后暖(P1型)的异常转折变化,而前暖后冷(P2型)则在20世纪70年代出现最多。冬季气温发生异常转折时,500 hPa位势高度场上反映出青藏高原高度场是最为关键的环流系统,甚至超过了乌拉尔山阻塞高压的影响。200 hPa风场上,西风急流等系统通过影响东亚冬季风进而影响冬季气温季节内变化。海平面气压场上,当蒙古高压在冬季呈显著前强后弱异常变化时,冬季气温易出现P1型异常转折,反之易出现P2型异常转折。冬季气温季节内发生异常转折时,北大西洋、赤道中东太平洋和赤道印度洋海温均表现出较为明显异常信号;当前期夏、秋季这三个海域海温异常偏高时,冬季气温易出现P1型异常转折,反之则易出现P2型异常转折,夏、秋季异常海温可作为预测前兆信号。

西南地区工业遗产时空分布特征及其影响因素

工业遗产承载着人类社会的变革,也记载着城市的历史,对其时空分布特征及影响因子的研究是保护和活化利用的重要依据。西南地区自然地理环境独特,使得其工业发展同中东部地区相比有自身的特殊性。选取西南地区48处国家级工业遗产为主要研究对象,运用GIS空间分析等方法分析工业遗产的时空分布特征及其影响因素。结果表明:(1)从时间分布看,西南地区工业遗产具有时间跨度大、历史延续性强、阶段性突出的特征,且以近现代工业遗产为主;(2)西南地区工业遗产在空间分布上呈“东多西少”的不均衡态势,其空间分布类型为集聚型,表现出“大集中、小分散”“东密西疏”的聚集特征,形成了“一核一副、带状分布”的分布格局;(3)在影响因素方面,西南地区的工业遗产分布受自然地理、社会经济、历史环境和政府政策等多方面因素的共同影响。研究成果形成西南地区工业遗产时空分布及其内在机制的地域特征的前沿探索研究,对西南地区工业遗产研究具有基础作用。

西南民族地区文旅融合发展的影响因素及组态路径--基于模糊集定性比较分析的云南省实证研究

探究西南民族地区文旅融合发展的组态路径对于促进西南民族地区文旅融合的高质量发展具有重要意义。通过归纳演绎得出西南民族地区文旅融合发展的影响因素,并借助模糊集定性比较分析方法研究云南省16个市州文旅融合发展的案例发现,单个影响因素并不构成西南民族地区文旅融合发展的必要条件,但也发挥着较普适的作用;政府与城镇化逻辑下依托需求驱动型、需求主导下依托政府与城镇化驱动型、需求与人才双元逻辑下依托政府及城镇化驱动型、多元合力驱动型四种组态路径,可助推西南民族地区文旅融合的高质量发展。

浙西南山区填方边坡加固措施及稳定性分析

以浙西南山区填方边坡区为研究对象,结合室内试验分析水泥土的力学性质;采用有限差分软件的强度折减法和极限平衡法,研究搅拌桩结构参数变化对加固边坡的影响规律,分析搅拌桩加固后边坡的稳定性。结果表明,水泥可提高土体的强度,但效果有限;增加围压,水泥土由脆性破坏逐渐转为塑性破坏;改变桩水平分布数量,对提高边坡稳定性效果不显著;改变桩加固位置对边坡稳定性的影响较大,选取合适的加固位置是加固边坡的关键。

西南屯堡聚落研究热点与趋势——基于CiteSpace的知识图谱分析

屯堡聚落作为中国历史上较为特殊的聚落类型广泛分布于西南地区。目前,针对西南屯堡聚落研究的综述性成果极少,利用CiteSpace对截至2023年末的研究文献进行了可视化分析。研究结果显示:西南屯堡聚落研究在发文量、关键词热点及突现、研究时区等方面显示出3个阶段的特点;总体而言,保护发展“传统聚落”与辨析探究“屯堡文化”是西南屯堡聚落研究领域的重要支撑点。目前研究热点为多学科交叉聚焦屯堡聚落空间解析与利用,以乡村振兴为政策实施路径,新兴屯堡旅游等相关产业。未来西南屯堡聚落研究的发展方向包括:以屯堡聚落空间为载体,建设更有文化价值和景观价值的特色风貌空间;充分利用屯堡旅游资源,实现乡村振兴发展和建设美丽乡村;以滇黔古道为屯堡遗产廊道线索,拓展黔中地区以外的区域性研究、线性遗产研究及区域发展研究。

中韩城市馆屋盖结构设计

中韩城市馆屋盖结构呈双向自由曲面形态,大空间区域的竖向主受力方向采用单向张弦梁结构,由张弦梁上弦及其平面外的刚性连接系杆共同组成水平刚度较大的单层正交刚架。各榀张弦梁的几何参数随建筑外形变化,跨度主要为45 m、72~90 m。设计时考虑了结构的风荷载和雪荷载敏感性,以及可能存在的极端降温工况,明确了适用于本项目的索松弛控制指标,通过分析验证了结构整体和关键节点的受力性能。

2010年西南特大干旱及典型场次旱灾对比分析

2009年10月—2010年4月,我国西南地区遭受了秋冬春三季连旱,耕地受旱面积、受灾人口和农村饮水困难情况都达到了近10年来该地区的最高水平,受灾率和成灾率均为1943年以来的最大值。通过历史场次旱灾对比分析发现,西南干旱并非偶然发生的现象,1951—1990年该地区同时发生干旱的次数为12次,且有缓慢加重的趋势。以云南为例,本次灾害与1963年旱灾在时空分布、灾害成因和灾情方面较为相似。这些研究成果对于认清西南地区干旱特性与旱灾的时空分布和演变规律,加强抗旱减灾体系建设以及政策的制定等,都具有重要的参考价值。