气候变化对西藏环境经济的可能影响

依据西藏一江两河（雅鲁藏布江、拉萨河、年楚河）地区40年的气象资料,分析了该地区的气候变化,指出一江两河地区气温有升高趋势,降水有减少趋势。同时还分析了气候变化对该地区农、牧业生产、水资源及环境的影响,探讨了为适应气候变化可采取的一些策略措施。     

云闪放电过程中雨滴增长的数值试验研究

利用二维数值模式,对雨滴在云闪放电条件下的增长进行了试验研究。分别讨论了在不同的电场、荷电量和电场角度时雨滴的增长演变及其运动状况。结果表明：二维模式中闪电放电对雨滴增长的影响与一维有明显不同。电场和荷电量作单因子变化时,雨滴在二维中随参量取值的增加变化较大。两者同时变化时,其乘积愈大雨滴增长幅度愈大。雨滴对电场角度绝对值变化的反应较为缓慢。其运动轨迹在不同的条件下均为准周期的。     

Upper Eocene ejecta of the New Jersey continental margin reveal dynamics of Chesapeake Bay impact

Evidence for the Chesapeake Bay Crater as the source for New Jersey continental margin ejecta is provided by fine-grained tektites and coarse-grained unmelted ejecta. The Upper Eocene ejecta deposit, now demonstrated to be part of the North American strewn field, occurs on the New Jersey continental margin at Ocean Drilling Program (ODP) Sites 904 and 903. The mineralogy, major oxide composition of the ejecta materials, and biostratigraphic age of the enclosing sediments link the origin of these ejecta to the recently recognized Chesapeake Bay impact crater, located only 330 km away. Sediments associated with the ejecta provide information about the dynamics of impact events. The 35-cm-thick ejecta-bearing layer can be subdivided into three subunits that indicate a sequence of events. Bottom subunit III documents sediment failure and deposition of gravel-sized fragments, middle subunit II records deposition of abundant sand-sized ejecta by gravity settling, and upper subunit I contains a 12-cm-thick sedimentary deposit containing rare silt-sized tektites and evidence of waning currents. These events are interpreted by linking sediment deposition to seismic ground motion and subsequent tsunami waves triggered by both the Chesapeake Bay impact and slope failures.     

硅微粉增韧环氧树脂的研究

增韧硅微粉是为增韧环氧树脂而研制开发的一种电工级专用填料。本文着重论述了硅微粉增韧的配方、工艺条件和增韧处理过程;通过对填充增韧硅微粉的环氧树脂固化物的冲击试验,证明了增韧硅微粉对环氧树脂具有明显的增韧效果;初步探讨了增韧硅微粉对环氧树脂增韧的机理。     

Surge in global metal mining threatens vulnerable ecosystems

Mining activities induce profound changes to societies and the environment they inhabit. With global extraction of metal ores doubling over the past two decades, pressures related to mining have dramatically increased. In this paper, we explore where growing global metal extraction has particularly taken effect. Using fine-grain data, we investigate the spatial and temporal distribution of mining of nine metal ores (bauxite, copper, gold, iron, lead, manganese, nickel, silver and zinc) across approximately 3,000 sites of extraction worldwide between 2000 and 2019. To approach the related environmental implications, we intersect mining sites with terrestrial biomes, protected areas, and watersheds categorised by water availability. We find that 79% of global metal ore extraction in 2019 originated from five of the six most species-rich biomes, with mining volumes doubling since 2000 in tropical moist forest ecosystems. We also find that half of global metal ore extraction took place at 20 km or less from protected territories. Further, 90% of all considered extraction sites correspond to below-average relative water availability, with particularly copper and gold mining occurring in areas with significant water scarcity. Our study has far-reaching implications for future global and local policy and resource management responses to mitigate the negative effects of the expected expansion of metal mining.     

Northern Hemisphere Sudden Stratospheric Warming and Its Downward Impact in Four Chinese CMIP6 Models

Using the World Meteorological Organization definition and a threshold-based classification technique,simulations of vortex displacement and split sudden stratospheric warmings(SSWs)are evaluated for four Chinese models(BCC-CSM2-MR,FGOALS-f3-L,FGOALS-g3,and NESM3)from phase 6 of the Coupled Model Intercomparison Project(CMIP6)with the Japanese 55-year reanalysis(JRA-55)as a baseline.Compared with six or seven SSWs in a decade in JRA-55,three models underestimate the SSW frequency by~50%,while NESM3 doubles the SSW frequency.SSWs mainly appear in midwinter in JRA-55,but one-month climate drift is simulated in the models.The composite of splits is stronger than displacements in both the reanalysis and most models due to the longer pulse of positive eddy heat flux before onset of split SSWs.A wavenumber-1-like temperature anomaly pattern(cold Eurasia,warm North America)before onset of displacement SSWs is simulated,but cold anomalies are mainly confined to North America after displacement SSWs.Although the lower tropospheric temperature also displays a wavenumber-1-like pattern before split SSWs,most parts of Eurasia and North America are covered by cold anomalies after split SSWs in JRA-55.The models have different degrees of fidelity for the temperature anomaly pattern before split SSWs,but the wavenumber-2-like temperature anomaly pattern is well simulated after split SSWs.The center of the negative height anomalies in the Pacific sector before SSWs is sensitive to the SSW type in both JRA-55 and the models.A negative North Atlantic Oscillation is simulated after both types of SSWs in the models,although it is only observed for split SSWs.     

IPCC AR6报告解读：气候变化与人类健康

IPCC近期发布了第六次评估报告（AR6）第二工作组（WGII）报告《气候变化：影响、适应和脆弱性》,其中第7章“健康、福祉和不断变化的社区结构”评估了气候变化对人类健康和福祉的当前影响以及未来风险,提出了应对气候变化的解决方案和适应策略。报告明确指出,气候变化对气候敏感传染病和慢性非传染性疾病,以及精神心理健康等的威胁正在增加,并表现出复合暴露和连锁事件的风险,且预计未来风险还会随着全球变暖而进一步加剧。实施积极和有效的气候变化适应措施并快速采取行动,将会在很大程度上减少和避免气候变化导致的健康风险,但不会完全消除所有风险。报告凸显了气候变化健康影响的严重性和紧迫性,未来需要加大对健康领域适应气候变化的科技创新、规划、行动和资金支持。     

Dynamic Characteristics of Granite Subjected to Intermediate Loading Rate

Summary A large diameter split Hopkinson pressure bar (SHPB) has been developed. This equipment is briefly described, together with a shaped striker that initiates a half-sine incident waveform to obtain the complete stress-strain relationship of the Bukit Timah granite at medium strain rate. Good constant strain rate was derived, and the dynamic complete stress-strain curves and energy absorption of the granite were measured at a strain rate between 20 and 60 per second. Repeated impact between 60–90% of the static strength of the granite was also conducted. Results from the tests show that the cumulative damage of the granite depends on the peak stress of the dynamic loads with a fixed duration. The dynamic fracture strength of the granite loaded at medium strain rate is directly proportional to the cube root of the strain rate. For the granite loaded at this strain rate, Youngs modulus is unchanged. Energy absorption of the samples loading to fragmentation determined its fragmented size distribution. At high strain rate, the rock possesses large energy absorption and the particle size of the fragments is much smaller.     

Diatom paleoecology of Laguna Zoncho,Costa Rica

We analyzed diatoms in a sediment profile from Laguna Zoncho in southern Pacific Costa Rica (lake elevation 1190 m asl, depth 2.6 m, area 0.75 ha) spanning some 3240 cal yr. Diatoms are common in the profile, which we subdivide into three zones. Zone C (3240–1020 cal yr B.P.) is dominated by Staurosira construens var. venter and Aulacoseira spp.; during this time, the lake was dilute and circumneutral. Benthic and acidophilous taxa increase gradually in the upper section of this zone. Zone B (1020–460 cal yr B.P.) almost totally lacks Aulacoseira, and instead is dominated by combinations of Eunotia minor, Encyonema lunatum, Gomphonema gracile, and Pinnularia braunii. Previous pollen and charcoal analysis indicates that this zone falls within the peak of prehistoric agricultural activity at the lake, but diatoms may also reflect climate change. During this period, the lake was likely shallower and more acidic, but not eutrophic. Finally, Zone A (460 cal yr B.P. to AD 1997) begins near a 1.5-cm tephra layer from nearby Volcán Barú; diatom assemblages are dominated by Aulacoseira spp., and suggest deepening of the lake and return to conditions similar to Zone C. This was a time of indigenous population decline and forest recovery in the Zoncho region, probably reflecting the impact of European diseases on the native population, although climate change and impacts of the tephra deposition cannot be wholly discounted.