基于DEM的山区旱灾风险评价模型——以西南地区为例

旱灾研究中,地形导致的水热再分配容易造成地域间旱灾灾情的明显差异,因此地形因子对于旱灾风险的准确评价及灾情的客观评估至关重要。采用气象站点观测数据和DEM数据,通过模拟复杂地形影响下的下垫面真实水分情况,加入地形因子的影响,建立了以干旱致灾因子(水分条件)、孕灾环境(地形)、承灾体(农作物脆弱性曲线)综合的旱灾风险评价三度模型;并以地形复杂、旱灾多发的西南地区为例,编制了旱灾风险等级图,以期为客观评估旱灾灾情,有效开展区域旱灾风险防范提供科学依据。     

三峡上游地区一次西南涡暴雨过程中尺度特征诊断和数值模拟

结合高空、地面实况观测数据以及1°×1°NCEP客观再分析资料,对2009年6月28日20时至29日20时(北京时)发生在三峡上游地区的一次区域暴雨过程进行了中尺度特征诊断,结果表明本次过程是东北低涡和副高稳定少动的大尺度环流背景形势下,由于高原低值系统在东移过程中与西南涡结合而产生的强降水天气过程。高原上不稳定能量的扰动和下传为西南涡的产生提供了必要能量条件,高低层的水汽平流和水汽辐合的交汇地带与最强降水带存在较好的一致性。另外,利用WRF中尺度数值模式对该次过程进行了数值模拟,结果显示在同化了地面和高空常规观测资料后,模式模拟效果得到明显改善,模拟降水能够大致体现该次过程的总的降水演变和分布情况,但后期模拟降水偏大。数值诊断结果发现,盆地西部与上升气流相伴的正涡度柱的演变过程与强降水的发生过程密切相关,该因子对于正确预报降水发生时间具有指示意义。     

1961~2015年西南地区降水及洪涝指数空间分布特征

利用西南地区98个气象站连续完整的日降水序列数据,整合降水强度、持续性指数及等级指数形成降水指数体系并研究该区域降水及洪涝指数的空间分布特征,得到以下主要结论：（1） 1961~2015年,西南地区年降水量（PRCPTOT）与极端降水量（R95PTOT）都呈现出“东多西少、南多北少”的分布形态;持续降水日数（CWD）则表现为“南高北低、西高东低”的分布格局。区域多年平 均PRCPTOT、R95PTOT、CWD分别以-13.12 mm/10 a、1.34 mm/10 a、-0.29 d/10 a的速率变化。（2）西南地区不同等级降水日数具有相似的空间分布特征,均呈现出“南高北低、东高西低”的分布形态。（3）西南地区洪涝强度指数呈由东北向西南递减的分布特征;降水总量越多的地区,洪涝强度反而越低,主要由于单站洪涝强度表征的是降水的波动情况,降水量越多波动越不明显。21世纪以来,该 地区洪涝等级以重级为主,2010年以来连续多年出现特重级洪涝。此外,洪涝强度越大,区域性年度灾害等级越高。该研究对于掌握西南地区极端气候变化规律,从而服务于防灾减灾具有一定的理论意义。     

攀西区域涉重金属典型企业周边环境特征及潜在生态风险

通过对攀西区域安宁河流域的7个断面底泥以及该区域17家典型涉重金属工业周边土壤进行环境质量状况调查和生态风险评价,结果显示,底泥中6种重金属砷、铬、铅、镉、汞和钒含量在凉山州境内特别是冕宁县断面含量最高,污染最重,攀枝花境内米易县部分含量较低;底泥中铅、镉和砷等出现了中重度污染,且钒和铬含量、砷和镉含量之间分别呈极显著和显著相关,同源性特征明显,土壤中镉超标范围最广,超标程度最重且呈面状重度风险,钒和汞超标范围较大,汞出现较重风险,其余为低度风险。     

New particle formation observed from a rain shadow region of the Western Ghats,India

Abstract

This study reports on new particle formation (NPF) and characteristic features observed from a rural site falling in the rainshadow of the Western Ghats in peninsular India. A total of 35 NPF events observed during August 2018 - January 2019 are classified and analyzed here. The apparent formation rates ranged from 0.2 to 10.0?cm^–3 s^–1, while the growth rates of nucleation mode particles ranged from 1.2 to 13.8?nm h^–1. The frequency of occurrence was least during August (core monsoon) and highest during post-monsoon. The local winds were calm and southeasterly to easterly (from the urban centre) supplying the essential precursor gases during October and November, leading to a frequent occurrence of nucleation events. Observations suggest that an increased condensation sink could limit the NPF while promoting Aitken mode growth. The newly formed particles accounted for about 10–80% of the total aerosol concentration. These newly formed particles were able to act as cloud condensation nuclei after growing to approximately 50?nm with an average activation fraction of 0.4.     

Palaeorunoff estimations achieved from palaeoclimatic information for the southwest part of the North China Plain: an attempt to apply a climatological approach to palaeohydrology

Palaeoclimatic scenario projecting annual temperature and annual precipitation is firstly formalized with data available and speculations for the southwest part of the North China Plain (35- 37°N, 115-119°E) during the last 25000 years. Then, with three regression equations relating annual runoff to annual precipitation and derived with data of modern hydrological and meteorological records, values of annual runoff are calculated in terms of the corresponding values of annual precipitation from this palaeoclimatic scenario for this region during this temporal interval. These results indicate that runoff is the most during 8000-3000a B.P. and the least during 25000-12000 a B. P.; runoff occurring during 12000-8000 a B.P. and during 3000-0 a B.P. is less than the one occurring during 8000-3000 a B.P. and more than the one occurring during 25000-12000 a B. P.; and the runoff occurring during 25000-12000 a B. P., 12000-8000 a B. P., and 3000-0 a B.P. is respectively 43, 46 and 66 percent of the one occurring during 8000-3000 a B.P. Values of bankfull discharge for palaeochannels of the Yellow River flowing in this region during the same interval are calculated from available estimates of slope of stream-bed of these palaeochannels with a regression equation relating bankfull discharge to slope of stream-bed and ratios of bankfull-discharge are further calculated from these values for different groups of palaeochannel formed during different time spans embraced in this interval. To conduct a cross-check, these values and ratios of bankfull-discharge are compared to the corresponding values and ratios of runoff occurring during roughly the same time spans. The same direction and similar relative magnitude of changes of the surface water occurring in this region during the last 25000 years are indicated by these comparisons.     

Historical perspectives on contemporary human–environment dynamics in southeast Africa

The human communities and ecosystems of island and coastal southeast Africa face significant and linked ecological threats. Socioecological conditions of concern to communities, governments, nongovernmental organizations, and researchers include declining agricultural productivity, deforestation, introductions of non-native flora and fauna, coastal erosion and sedimentation, damage to marine environments, illegal fishing, overfishing, waste pollution, salinization of freshwater supplies, and rising energy demands, among others. Human–environment challenges are connected to longer, often ignored, histories of social and ecological dynamics in the region. We argue that these challenges are more effectively understood and addressed within a longer-term historical ecology framework. We reviewed cases from Madagascar, coastal Kenya, and the Zanzibar Archipelago of fisheries, deforestation, and management of human waste to encourage increased engagement among historical ecologists, conservation scientists, and policy makers. These case studies demonstrate that by widening the types and time depths of data sets we used to investigate and address current socioecological challenges, our interpretations of their causes and strategies for their mitigation varied significantly.     

西南地区陆地植被生态系统NPP时空演变及驱动力分析

研究西南地区陆地植被生态系统净初级生产力(NPP)的时空演变特征及其驱动力,对区域生态环境保护具有重要的现实意义.利用2000～2021年MODIS NPP、1999～2021年基于站点的气象数据和2000～2020年土地利用类型等数据,结合主成分分析、残差分析、Theil-Sen Median趋势分析和偏相关分析等方法,研究西南地区陆地植被生态系统NPP时空演变及其对驱动力的响应特征.结果表明,时间上,2000～2021年西南地区植被NPP呈波动上升趋势,速率为3.54g·(m²·a)^-1.气候变化和人类活动影响下,农田、草地和森林生态系统NPP均呈上升趋势,但农田生态系统NPP的上升趋势最为显著.空间上,西南地区植被NPP呈上升趋势的面积占比为89.06%,显著上升和极显著上升的区域主要分布在广西南部、四川东部、重庆西部,以及云南和贵州交界处.气候变化和人类活动对西南地区植被生长具有双重影响,气候变化和人类活动影响下农田生态系统NPP呈上升趋势的面积占比均高于草地和森林生态系统.西南地区植被NPP与各气象因子的相关性呈明显地域差异.区域尺...     

西南丘陵区村镇典型供水水源有机物分布特征及对饮水水质的影响

以西南丘陵区村镇典型供水水源原水及其净化水为研究对象,分析了水质净化常规工艺前后其有机污染物分布特征及对饮水水质的影响.结果表明:该区域村镇供水水源属微污染水源水体,有机污染物以溶解性中小分子有机物为主,占有机物总量的50%~80%.共检测到53种共14类有机物,主要为烷烃、酯、酚、苯类物质,占有机物总量的80%~90%左右,有机酸、烯烃、醇和醛含量较小.有机物中二氯甲烷、苯酚、邻苯二甲酸二丁酯含量较高,并且出现了除草剂、食品添加剂、抗生素等污染物,如特丁津、2,6-二叔丁基对甲酚、萘啶酸等.水质净化常规工艺主要去除相对分子质量10×10~3的有机物,小分子量有机物中有机酸类去除效果较好,但烷烃、酯、酚、苯类有机物去除效果较差.     

西南丘陵区保护性耕作下小麦农田土壤呼吸及影响因素分析

为了探讨保护性耕作对旱作农田土壤呼吸的影响,采用LI6400-09呼吸室在重庆北碚西南大学试验农场对平作(T)、垄作(R)、平作+覆盖(TS)、垄作+覆盖(RS)这4种处理下的西南紫色土丘陵区小麦/玉米/大豆套作体系中小麦作物生长季节的土壤呼吸及其水热生物因子进行了测定和分析.结果表明,小麦生殖生长阶段农田土壤呼吸速率变化范围为1.100～2.508μmol.(m2.s)-1,各处理的土壤呼吸速率差异显著,表现为RS>R>TS>T.各处理10 cm土层的土壤温度表现为T>R>TS>RS.土壤呼吸与土壤温度的关系符合指数函数,Q10值分别为1.25、1.20、1.31和1.26.5 cm土层的土壤含水量高低排序为TS>RS>T>R.土壤水分与土壤呼吸以抛物线曲线拟合最好,说明存在土壤呼吸最强的土壤含水量点,本研究得出小麦生殖生长阶段在土壤含水量的响应阈值为14.80%～17.47%.土壤动物中优势类群为弹尾目和螨目,与土壤呼吸存在一定相关性,对照处理和垄作下相关性高,而秸秆覆盖的处理土壤呼吸与土壤动物没有明显的相关性.