Excess in precipitation as a cause for settlement decline along the Israeli coastal plain during the third millennium BC     

Avraham Faust  Yosef Ashkenazy 《Quaternary Research》2007,68(1):37-44

Although the relations between climate and settlement are not straightforward, there is a general agreement that arid conditions are less favorable for human settlement in the semiarid Near East than humid conditions. Here we show that humid conditions resulted in the abandonment of settlements along the Israeli coastal plain. We first present archaeological evidence for a drastic decline in settlement along the Israeli coast during most of the third millennium BC (Early Bronze Age II-III). Then, based on archaeological and climatic evidence, we link this decline to an environmental change occurring at that time. We propose that increased precipitation intensified the already existing drainage problems and resulted in flooding, which led to the transformation of arable land into marshes and to the spread of diseases, gradually causing settlement decline and abandonment.  相似文献   

    

Matthew E. Kirby  Christopher J. Poulsen  Steve P. Lund  William P. Patterson  Liam Reidy  Douglas E. Hammond 《Journal of Paleolimnology》2004,31(3):275-293

Southern California faces an imminent freshwater shortage. To better assess the future impact of this water crisis, it is essential that we develop continental archives of past hydrological variability. Using four sediment cores from Lake Elsinore in Southern California, we reconstruct late Holocene (3800 calendar years B.P.) hydrological change using a twentieth-century calibrated, proxy methodology. We compared magnetic susceptibility from Lake Elsinore deep basin sediments, lake level from Lake Elsinore, and regional winter precipitation data over the twentieth century to calibrate the late Holocene lake sediment record. The comparison revealed a strong positive, first-order relationship between the three variables. As a working hypothesis, we suggest that periods of greater precipitation produce higher lake levels. Greater precipitation also increases the supply of detritus (i.e., magnetic-rich minerals) from the lake's surrounding drainage basin into the lake environment. As a result, magnetic susceptibility values increase during periods of high lake level. We apply this modern calibration to late Holocene sediments from the lake's littoral zone. As an independent verification of this hypothesis, we analyzed ¹⁸O_(calcite), interpreted as a proxy for variations in the precipitation:evaporation ratio, which reflect first order hydrological variability. The results of this verification support our hypothesis that magnetic susceptibility records regional hydrological change as related to precipitation and lake level. Using both proxy data, we analyzed the past 3800 calendar years of hydrological variability. Our analyses indicate a long period of dry, less variable climate between 3800 and 2000 calendar years B.P. followed by a wet, more variable climate to the present. These results suggest that droughts of greater magnitude and duration than those observed in the modern record have occurred in the recent geological past. This conclusion presents insight to the potential impact of future droughts on the over-populated, water-poor region of Southern California.  相似文献   

  总被引：21，自引：0，他引：21  

Jason Evans  Roland Geerken 《Journal of Arid Environments》2004,57(4):535

In this study we present a technique to discriminate between climate or human-induced dryland degradation, based on evaluations of AVHRR NDVI data and rainfall data. Since dryland areas typically have high inter-annual rainfall variations and rainfall has a dominant role in determining vegetation growth, minor biomass trends imposed by human influences are difficult to verify. By performing many linear regression calculations between different periods of accumulated precipitation and the annual NDVI_max, we identify the rainfall period that is best related to the NDVI_max and by this the proportion of biomass triggered by rainfall. Positive or negative deviations in biomass from this relationship, expressed in the residuals, are interpreted as human-induced. We discuss several approaches that use either a temporally fixed NDVI peaking time or an absolute one, a best mean rainfall period for the entire drylands or the best rainfall period for each individual pixel. Advantages and disadvantages of either approach or one of its combinations for discriminating between climate and human-induced degradation are discussed. Depending on the particular land-use either method has advantages. To locate areas with a high likelihood of human-induced degradation we therefore recommend combining results from each approach.  相似文献   

降雨对张家口地震台伸缩仪干扰特征的研究     

马兴国  王勤彩  乔子云  马喜龙 《高原地震》1997,(2)

张家口伸缩仅受降雨干扰,不但与降雨量有关,而且与季节和降雨的方式等也有密切的关系。夏、秋季节持续或突降大雨后,两天左右引起应变量明显的变化,可用2．5倍毫米应变均方差,识别干扰和异常,有较大的使用价值。  相似文献   

    

Tamara Tokarczyk  Wiwiana Szalińska 《水文科学杂志》2013,58(9):1675-1689

Abstract

The combined analysis of precipitation and water scarcity was done with the use of the Standardized Precipitation Index (SPI) and the Standardized Runoff Index (SRI), developed as a monthly, two-variable SPI-SRI indicator to identify different classes of hydrometeorological conditions. Stochastic analysis of a long-term time series (1966–2005) of monthly SPI-SRI indicator values was performed using a first-order Markov chain model. This provided characteristics of regional features of drought formation, evolution and persistence, as well as tools for statistical long-term drought hazard prediction. The study was carried out on two subbasins of the Odra River (Poland) of different orography and land use: the mountainous Nysa K?odzka basin and the lowland, agricultural Prosna basin. Classification obtained with the SPI-SRI indicator was compared with the output from the NIZOWKA model that provided identification of hydrological drought events including drought duration and deficit volume. Severe and long-duration droughts corresponded to SPI-SRI Class 3 (dry meteorological and dry hydrological), while severe but short-term droughts (lasting less than 30 days) corresponded to SPI-SRI Class 4 (wet meteorological and dry hydrological). The results confirm that, in Poland, meteorologically dry conditions often shift to hydrologically dry conditions within the same month, droughts rarely last longer than 2 months and two separate drought events can be observed within the same year.  相似文献   

MGCPN：基于IMERG数据的青藏高原地区降水临近预报的高效深度学习模型     

Mingyue LU  Zhiyu HUANG  Manzhu YU  Hui LIU  Caifen HE  Chuanwei JIN  Jingke ZHANG 《Journal of Meteorological Research》2024,25(4):693-707

在青藏高原地区,由于雨量计的分布稀疏和布局不均,直接影响了该地区的降水预报的准确性。针对这一问题,本文提出了生成对抗网络结合卷积长短时记忆网络（GAN-ConvLSTM）的降水临近预报模型（MGCPN）。该模型依托全球降水测量任务（GPM）下的综合多卫星反演数据（IMERG）,能够为未来30至300分钟提供高时空分辨率的降水预报。研究成果表明,MGCPN模型有效缓解了深度学习模型方法随着预测时间延长而出现的降水量低估和结果模糊的问题。此外,通过融合地表特征数据的多源时空数据集进行训练和预测,进一步提升了模型的准确度。本研究基于MGCPN模型实现了对GPM数据的准确临近预测,为青藏高原地区的降水研究与预报工作提供了宝贵的支撑。此外,研究结果表明MGCPN模型在多个评价指标上都具有显著优势;在在命中率、临界成功指数、海德克技能得分以及平均绝对误差等指标上,MGCPN模型的表现超越了其他对比模型,特别是在命中率指标上,MGCPN模型相比卷积门控循环单元（ConvGRU）、ConvLSTM以及小型注意力U-Net（SmaAt-UNet）分别提高了约33%、19%和8%。

  相似文献   

基于极端降水排序法的铜仁降水致灾预警阈值方法初探     

谢仁波  何历洪  代瑞华  符晴 《中低纬山地气象》2024,48(5):81-86

摘 要：【目的】基于铜仁市10个国家级台站1991-2020年的逐日降水资料,分析了铜仁日雨量、连续降水量、连续降水日数3个降水评价指标的稳定性,给出降水灾害的最优预警阈值。【方法】计算GB/T 33669-2017排序法、水文排序法、10倍年数取值排序法3种算法的极端降水指标阈值,并对3个降水评价指标致灾风险进行分析讨论。【结果】（1）根据GB/T 33669-2017排序法得出的铜仁极端降水指标阈值明显大于该区域自然资源的承受能力,分年提取样本会漏掉许多重要信息。（2）根据水文排序法得出的极端降水指标阈值总体优于国标排序法,但仍有重要信息遗漏。（3）10倍年数排序法得出的极端降水指标阈值,既与自然资源承载能力较为匹配,又能避免了重要信息遗漏。【结论】铜仁1日最大降水量、连续降水日数和连续降水量年际间变化大,稳定度差,国标法或每年等量样本入选排序法漏掉的重要信息多,不适合用于本市致灾阈值的计算。用10倍年数基本资料排序法得出的极端降水阈值,既可以保证重要信息入选,又与自然资源承载能力较为匹配,还与前人的研究最为接近,可以优先推荐为铜仁降水监测指标的灾害预警阈值。  相似文献   

青藏高原和西南地区60年不同等级昼夜降雨日数的变化特征     

李卓敏  巩远发  向楠 《气候与环境研究》2023,16(4):367-384

利用国家气象科学数据中心的青藏高原81个站和西南地区80个气象站点的逐日昼夜降水量资料,统计分析了1961～2020年60年来两个地区不同量级昼夜降雨日数及其差异的年变化、年际变化（趋势）特征。结果表明：（1）青藏高原和西南地区不同等级昼夜降水日数年变化都是在5月迅速增多,11月显著减少;两个地区的降雨日数昼夜差异大的月份均在5～10月,大雨和暴雨日数在5～10月的贡献更大,青藏高原暴雨日数占全年暴雨日数的85%以上、大雨占比90%以上,西南地区这两个量级降水占比分别为93%和86%;两个地区雨季夜间发生极端强降水（暴雨）的概率远大于白天。（2）两个地区雨季不同量级昼夜降水日数差异显著。三江源和青藏高原东南部昼夜都是小雨、中雨的频次多,大雨仅夜间在西藏东南部及三江源东侧发生较多;暴雨仅在青藏高原东部多发,夜间发生的站点明显多于白天。西南地区昼夜小雨和中雨发生率较高的地区包括川中区域、川西边缘山地和云南西南部;大雨在云南西南部白天易于发生,川中则是夜间易于发生;暴雨以上量级的典型多发区为四川中东部、重庆西部、贵州中南部。（3）两个区域雨季昼夜分等级降雨日数的年际变化总体趋势有明显的不同。青藏高原地区除了夜间小雨日数为显著减少外,其余的不同量级昼夜降雨日数都显著增加,夜间的增加趋势均大于白天,大雨和暴雨在夜间的增加趋势几乎是白天的2倍。与青藏高原不同的是,西南地区小量级降水（小雨—中雨—大雨）日数总体呈显著减少趋势,其中夜间的小雨日数减幅最大,为白昼的2倍左右;大量级降水（暴雨—大暴雨）日数则是相反的增加趋势,且夜间增加趋势大于白天。  相似文献   

河南降水及最长连续无降水日数时空特征     

王明军侯振雨  沈素芹 《河南气象》2003,(2):18-19

利用河南省均匀分布的50个台站自建站至1997年近50年的定时降水资料，分析了河南省日小雨、日中雨、日大雨降水过程出现次数和最长连续无降水日数，结果显示，河南省日小雨、日中雨降水过程一年四季均可出现，日大而过程主要出现在3～11月份，冬季仅在豫南一些台站出现，各级降水过程出现次数季节性变化明显，冬季出现最少，夏季出现最多，其地理分布随测站纬度、拔海高度、地形地貌不同有较大差异；最长连续无降水日数也有明显的季节性变化特点，其最大值多出现在冬季，春秋次之，夏季最小，地理位置差异也较明显。  相似文献   

A tree-ring based precipitation reconstruction for the Mohe region in the northern Greater Higgnan Mountains,China, since AD 1724     

Tongwen Zhang  Yujiang YuanWenshou Wei  Shulong YuRuibo Zhang  Feng ChenHuaming Shang  Li Qin 《Quaternary Research》2014

August–July precipitation has been reconstructed back to AD 1724 for the Mohe region in the northern Greater Higgnan Mountains, China, using Pinus sylvestris var. mongolica tree-ring width. The reconstruction explains 39% of the variance in the precipitation observed from AD 1960–2008. Some droughts noted in historical documents are precisely captured in our reconstruction. Wet periods occurred during the periods of AD 1734–1785, AD 1805–1830, AD 1863–1880, AD 1922–1961, and AD 1983–1998; while the periods of AD 1786–1804, AD 1831–1862, AD 1881–1921, and AD 1962–1982 were relatively dry. Power spectral and wavelet analyses demonstrated the existence of significant 24-yr, 12-yr, and 2-yr cycles of variability. The results of the spatial correlations suggest that our reconstruction contains climatic signals for the southern Stanovoy Range and the northern Greater Higgnan Mountains. The positive correlations between the new reconstructed precipitation series and two precipitation reconstructions indicate that our precipitation reconstruction captures broad-scale regional climatic variations. A comparison between the weakening tendency of summer monsoon and the dry period of our reconstruction reveals that the annual precipitation in the Mohe region is partly influenced by the East Asian Summer Monsoon.  相似文献