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91.
Jessica R. Rodysill James M. Russell Satria Bijaksana Erik T. Brown La Ode Safiuddin Hilde Eggermont 《Journal of Paleolimnology》2012,47(1):125-139
Variations in the location and strength of convection in the Western Pacific Warm Pool (WPWP) have a profound impact on the
distribution and amount of global rainfall. Much of the variability in WPWP convection is attributed to variations in the
El Ni?o-Southern Oscillation, for which the long-term trends and forcing mechanisms remain poorly understood. Despite the
importance of WPWP convection to global climate change, we have very few paleohydrological reconstructions from the region.
Here we present a new paleolimnologic and paleohydrologic record spanning the past 1,400 years using a multi-proxy dataset
from Lake Logung, located in East Java, Indonesia that provides insights into centennial-scale trends in warm pool hydrology.
Organic matter δ13C data indicate that East Java became wetter over the last millennium until ca. 1800 Common Era (CE), consistent with evidence
for the southward migration of the Intertropical Convergence Zone (ITCZ) during this time. Superimposed on this long-term
trend are four decade- to century-scale droughts, inferred from organic matter δ13C and calcite abundance data. They are centered at 1030, 1550, 1830, and 1996 CE. The three more recent droughts correlate
with hydrologic anomalies documented in other proxy records from the WPWP region on both sides of the equator, and the two
most recent droughts correlate in time with historically documented periods of multiple, intense El Ni?o events. Thus, our
record provides strong evidence that century-scale hydrologic variability in this region relates to changes in the Walker
Circulation. Human activity within the lake catchment is apparent since 1860 CE. 相似文献
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Doan Van Binh Sameh A. Kantoush Tetsuya Sumi Nguyen Phuong Mai Trieu Anh Ngoc La Vinh Trung Tran Dang An 《水文研究》2021,35(2):e14030
The hydrogeomorphology of the Vietnamese Mekong Delta (VMD) has been significantly altered by natural and anthropogenic drivers. In this study, the spatiotemporal changes of the flow regime were examined by analysing the long-term daily, monthly, annual and extreme discharges and water levels from 1980 to 2018, supported by further investigation of the long-term annual sediment load (from the 1960s to 2015), river bathymetric data (in 1998, 2014 and 2017) and daily salinity concentration (from the 1990s to 2015) using various statistical methods and a coupled numerical model. Then, the effects of riverbed incision on the hydrology were investigated. The results show that the dry season discharge (i.e., in March–June) of the Tien River increased by up to 23% from the predam period (1980–1992) to the postdam period (1993–2018) but that the dry season water level at My Thuan decreased by up to −46%. The annual mean and monthly water levels in June at Tan Chau and in January and June–October at My Thuan in the Tien River decreased statistically, even though the respective discharges increased significantly. These decreased water levels instead of the increased discharges were attributed to the accelerated riverbed incision upstream from My Thuan, which increased by more than three times, from a mean rate of −0.16 m/year (−16.7 Mm3/year) in 1998–2014 to −0.5 m/year (−52.5 Mm3/year) in 2014–2017. This accelerated riverbed incision was likely caused by the reduction in the sediment load of the VMD (from 166.7 Mt/year in the predam period to 57.6 Mt/year in the postdam period) and increase in sand mining (from 3.9 Mm3 in 2012 to 13.43 Mm3 in 2018). Collectively, the decreased dry season water level in the Tien River is likely one of the main causes of the enhanced salinity intrusion. 相似文献
96.
Laštovička Jan Burešová Dalia Boška Josef Bremer Jurgen Märcz Ferenc 《Studia Geophysica et Geodaetica》1997,41(2):171-180
Data from four A3 radio wave circuits in central Europe are used to analyse the representativeness of the ionization and gravity wave activity pattern in the lower ionosphere (85 – 100 km) in the CRISTA experiment interval (3 – 12 November 1994) for the given conditions. It has been found that the CRISTA experiment interval was run under conditions, which are highly representative both of October – November 1994 and autumn, low-moderate solar activity, the descending phase of solar cycle conditions, i.e. CRISTA measurements may be considered to provide values identical with, or close to climatological values (at least for central Europe, h = 85 – 100 km). 相似文献
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关于西非荒漠化的本质和特征存在着许多看法。该文将追溯其历史,回顾荒漠化对气候影响的研究现状,并介绍一些有关研究结果。对荒漠化的认识通常为“沙漠”的扩张,是一个总体上不可逆转的人为过程。其过程与地表反照率增强,风沙加大以及土地生产力下降相联系。研究表明,在最近16年里撒哈拉沙漠的边界和萨赫勒植被均变化不大,从植被水分有效利用率来看,“生产力”没有系统性降低,地表反照率也没有多少改变。自20世纪50年 相似文献
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Askania La Maison Werke 《Journal of Geodesy》1951,25(1):116
Sans résumé
The online version of the original article can be found at 相似文献
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