Study of spatial distribution of sandy desertification in North China in recent 10 years

Sandy desertification is a land degradation characterized by wind erosion, mainly resulted from the excessive human activities in arid, semiarid and part of sub-humid regions in North China. It is one of main kinds of desertification/land degradation as well as water-soil erosion and salinization in China. Rapid and continuous spread of sandy desertification during last 50 years has created a major environmental and socio-economic problem in North China. Remote sensing monitored results in 2000 showed that the sandy desertified land area has been 38.57 × 10⁴ km². The area of potential to slightly sandy desertified land is 13.93 × 10⁴ km², moderately land 9.977 ×10⁴ km², severely land 7.909 × 10⁴ k² and very severely land 6.756 × 10⁴ km². Sandy desertification mainly occurs in the semi-arid mixed farming-grazing zone and its northern rangeland zone, semi-arid dryland rainfed cropping zone and arid oasis-desert margin zone. The average annually developmental rate of sandy desertified land increased from 2,100 km² · a^-1 in 1976–1988 to 3,600 km² · a^-1 in 1988–2000. The basic status of sandy desertification in North China is “overall deterioration, while local rehabilitation”. Already achieved rehabilitation results and monitoring assessment show that about 60% of desertified land in North China can be restored under the conditions of rational land-use ways and intensity.

     

Preliminary reconstruction of the desert and sandy land distributions in China since the last interglacial period

The desert and sandy land are the products of arid climate. The spatial distribution of modern deserts and sandy land in China and their relation to climate show following characteristics: arid and hyper-arid desert zones, at isohyet of less than 200 mm, are dominated by mobile dunes; semi-arid steppe and arid desert steppe with the precipitation between 200-400mm, are dominated by semi-fixed and fixed sand dunes; the precipitation of sub-humid forest grassland and humid forest zones with scattered fixed sand land is higher than 400 mm. With this as reference, in combination with considerable amount of paleoclimatic data in desert regions and adjacent regions, the distributions of desert and sandy land in China during the last interglacial period, the last glacial maximum (LGM), and the Holocene megathermal, were preliminarily reconstructed. The results compared with that of today show that the distribution of desert and sandy land in China was greatly dwindled during last interglacial period, and the mobile dune area was about two-thirds of that of today's, but greatly expanded during LGM. However, the dwindling area of desert and sandy land in the Holocene megathermal was smaller than that in the last interglacial period. The forcing mechanism was mainly related to the changes of East Asian winter and summer monsoon, south-northward swing of the westerlies and the variations of the Qinghai-Tibet Plateau monsoon intensity caused by global climate changes during the cold and warm intervals since the last interglacial period.     

我国对流层二氧化碳非均匀动态分布特征及其成因

人类活动导致大气中温室气体浓度上升,是全球气候变暖的主要原因之一.本文针对已经连续运行13年的AIRS（Atmospheric Infrared Sounder）卫星反演的对流层中层CO₂浓度资料,利用地基观测结果对其进行验证,同时结合多种相关资料对我国区域CO₂浓度的时空分布及季节变化进行研究.结果显示：北半球30°N—60°N是CO₂浓度高值带,低值中心主要出现在15°S—15°N,140°W向东至100°E的低纬地区.地基观测与AIRS卫星反演结果基本一致,年增长率约为1.926 ppmv·a^-1.我国区域CO₂浓度空间分布上呈现北高南低的非均匀分布特征,4个高值中心分别位于东北地区西南部、内蒙古西部、新疆地区东部和西部,低值中心在云南和西藏地区.我国区域CO₂浓度有明显的季节变化特征,最高值出现在春季,冬夏季次之,秋季最低,其季节演变特点与风场的输送、降水量的清除和植被的吸收等密切相关.

     

华北地区中强震前卫星红外亮温变化研究

应用相对功率谱估计方法对华北地区中强地震前静止气象卫星热红外遥感亮温资料进行时频分析, 结果表明: 华北5级以上地震发生前存在显著的亮温热异常, 震前1个月左右异常开始出现, 高值幅值持续时间超过20天, 功率谱幅值最高可以达到平均值的7倍以上, 且发震区域一般位于异常区边缘或异常区域内的断层上。     

华北北部地区地下水10年准周期及其与地震活动关系分析

1966年以来华北北部发生5．0级以上地震16次,根据时间上的密集程度可分为5个地震丛。地下水资料经过排出地下水超采造成的趋势下降干扰后,多井地下水资料呈现出10年准周期变化的同步性特征。地震丛发生在地下水多年周期的高值段,低值年份则没有中强以上地震发生。将10年准周期按一定规则分成低值段、上升段、高值段和下降段,在地下水10年周期4个时段的发震概率分别为0％、25％、50％、25％。     

How the spatial distribution of grass contributes to controlling hillslope erosion

The aim of this study was to investigate how the spatial distribution of grass influenced run-off and erosion from a hillslope with loess and cinnamon soils in the rocky area of Northern China. We set up a trial to test the two soils with different treatments, including bare soil (BS), grass strips on the upper (UGS) and lower (DGS) parts of the slope, grass cover over the entire slope (GS), and a grass carpet on the lower part of the slope (GC), under simulated rainfall conditions. The results showed that the run-off coefficients for the loess and cinnamon soils decreased by between 4% and 20% and by between 2% and 37%, respectively, when covered with grass. Grass spatial distribution had little effect on the run-off, but more effect on erosion than vegetation coverage degree. The most effective location of grass cover for decreasing hillslope erosion was at the foot, and the high efficiency was mainly due to controlling of rill formation and sediment deposition. The soil loss from GS, DGS, and GC on the loess and cinnamon soils was between 77% and 93% less and 55% and 80% less, respectively, compared with the loss from BS. However, the soil characteristics had little effect on soil erosion for well-vegetated slopes. The results highlight the importance of vegetation re-establishment at the foot of hillslope in controlling soil erosion.     

近30年三江源地区湖泊变化图谱与面积变化

以近30年的40景Landsat MSS/TM/ETM+、CBERS CCD遥感影像为数据源,采用植被指数法结合人工目视解译,分为四个时期对三江源地区湖泊进行了遥感水体检测.选取面积在15km2以上、总面积占研究区湖泊总面积的90%左右的24个湖泊作为典型湖泊,建立该地区湖泊的变化图谱,并引入湖泊萎缩强度指数对湖泊的面积变化及空间分布特征进行分析.结果表明,以第三时期(1999-2002年)为界,这24个湖泊总体上经历了先萎缩后扩张的过程,且萎缩的程度大于扩张的程度,近30年来湖泊总面积缩小了65.76km2.本文研究结论可为三江源地区对气候变化响应研究提供参考,并对区域水资源合理利用提供科学依据.     

AIC analysis of categorizing data for earthquakes and velocity structures in North China

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大华北地块区地震大形势研究

分析了大华北区历史地震活动分期与现代地震活动特点,讨论了大华北区及其相关区带不同地震活动幕地震空间活动特征。认为大华北地块区目前处在第四活动期的调整活动阶段,未来几年可能进入新的地震活跃幕,地震活动以5-6级地震为主,主要活动地区为燕渤带和鲁东—南黄海地块区。     

The current strain distribution in the North China Basin of eastern China by least-squares collocation

In this paper, the velocities of 154 stations obtained in 2001 and 2003 GPS survey campaigns are applied to formulate a continuous velocity field by the least-squares collocation method. The strain rate field obtained by the least-squares collocation method shows more clear deformation patterns than that of the conventional discrete triangle method. The significant deformation zones obtained are mainly located in three places, to the north of Tangshan, between Tianjing and Shijiazhuang, and to the north of Datong, which agree with the places of the Holocene active deformation zones obtained by geological investigations. The maximum shear strain rate is located at latitude 38.6°N and longitude 116.8°E, with a magnitude of 0.13 ppm/a. The strain rate field obtained can be used for earthquake prediction research in the North China Basin.     

Temporal and spatial variation characteristics of present stress field in the northern area of North China

From focal mechanism solutions of the earthquakes in the northern part of North China during the period of 2002～2006,the directions of principal stress axes in 4 stress sub-districts are analyzed using a grid test method.The characteristic of present crustal stress directions is discussed.Based on this result and on the focal mechanism solutions calculated for some events in the period of 1977～1998,in combination with some other study results,the temporal variation of present crustal stress directions in the northern part of North China is investigated.The re-sults confirm that the direction of crustal principal stress in some regions had somewhat rotated after the 1976 Tangshan M7.8 earthquake.The mean P axes of the focal mechanism solutions rotated clockwise not only in Tangshan sub-district,but also in Beijing and Xingtai sub-districts after the Tangshan earthquake.In Beijing and Xingtai sub-districts the orientations of principal stress axes in the period of 2002～2006 are consistent with that before the Tangshan earthquake,implying that the stress orientations has rotated back to the state before the Tang-shan earthquake in these two sub-districts.The directions of the mean P axes are nearly E-W in Tangshan sub-dis-trict since the M7.8 earthquake.The present stress field in the sub-district northwest to Beijing,or in the western part of the Zhangjiakou-Bohai fault zone,is relatively stable during the time period concerned in this study.Because of the limitation of data,this paper only states a possible variation of stress field in the northern part of North China in the recent decades.     

华北北部地区现今应力场时空变化特征研究.

依据2002——2006年的中小地震资料,利用格点尝试法分析计算了华北北部4个应力小区的平均主应力轴,讨论了华北北部地区的现今应力场特征.在此基础上,对1977——1998年研究区内的单个地震震源机制解进行了进一步的分析计算,并结合以往的研究结果,研究了华北北部地区现今应力场随时间的变化特征,结果印证了唐山地震前后,唐山震源区及其邻近地区应力场主应力方向出现的转动和变化的现象:1976年唐山发生7.8级地震后,唐山震源区及其邻近的北京地区和邢台地区震源机制解的平均P轴可能顺时针转动了约15deg;——30deg;。北京地区和邢台地区近期（2002——2006年）的平均主应力轴与唐山地震前的综合断层面解较为一致,这两个地区应力场似乎转回到唐山地震前的状态. 而唐山区震源机制解的平均P轴在地震后则一直稳定在EW向上。位于张家口——渤海断裂带西段的京西北地区,其现今应力场则相对比较稳定,唐山地震前后主应力方向没有太大变动。鉴于数据资料等方面的原因,本文的研究结果仅仅是初步给出了华北北部地区应力场近几十年来一种可能的调整变化图象。      

近期华北地震大形势的统计分析

文章在３－５年较长时间尺度概率估计的前提下，力争对未来较短时期（１－２年）各区，带地震活动趋势进行定量分析，特别着重于地震总活动水平的比较及年量大震级的预测。     

Preliminary Study on Two Newly-Generated Seismotectonic Zones in North and Southwest China

In previous seismotectonic studies,the emphasis was placed on the inherited active fault zones.In the recent tectonic stage that essentially keeps in step with the current regional geologic environment and the stress field,however,there are also some newly generated fault zones.By studying the seismicity in North and Southwest China,it has been known that the NE-trending Tangshan-Hejian-Cixian and NW-trending Tengchong-Gengma-Lancang seismic zones are just two newly generated fault zones.As distinguished from the inherited fault zones,they are called the newly generated seismotectonic zones.This paper deals with the existence of these two seismogenic zones from their seismicity and geological structures,gives a preliminary analysis of their characteristics,and shows their significance.     

Cropland cover change in Northeast China during the past 300 years

Land use/cover change induced by human activities has emerged as a “global” phenomenon with Earth system consequences. Northeast China is an area where the largest land cultivation activities by migrants have happened in China during the past 300 years. In this paper, methods including documentary data calibration and multi-sourced data conversion model are used to reconstruct historical cropland cover change in Northeast China during the past 300 years. It is concluded that human beings have remarkably changed the natural landscape of the region by land cultivation in the past 300 years. Cropland area has increased almost exponentially during the past 300 years, especially during the past 100 years when the ratio of cropland cover changed from 10% to 20%. Until the middle of the 19th century, the agricultural area was still mainly restricted in Liaoning Province. From the late 19th century to the early 20th century, dramatic changes took place when the northern boundary of cultivation had extended to the middle of Heilongjiang Province. During the 20th century, three agricultural regions with high ratio of cropland cover were formed after the two phases of spatial expansion of cropland area in 1900s–1930s and 1950s–1980s. Since 1930s–1940s, the expansion of new cultivated area have invaded the forest lands especially in Jilin and Heilongjiang Provinces. Supported by National Natural Science Foundation of China (Grant No. 40571165) and Innovation Foundation of Chinese Academy of Sciences (Grant No. KZCX2-YW-315)     

福建水库空间分布特征:沿海密度高水量少、内陆密度低水量多

水库是福建重要的水资源.通过2013-2015年遥感影像结合Google Earth和天地图提取福建水库3353座,分布在81个县区,总面积647.51 km2,约占全省土地面积的0.5%;其中面积≤1 km2水库3248座,总面积197.16 km2,面积1 km2水库105座,总面积450.35 km2.基于经验公式估算总蓄水量188.18亿m3,其中小型水库3078座(91.80%),蓄水总量37.06亿m3(19.69%),大中型水库275座(8.20%),蓄水总量151.12亿m3(80.31%).从空间分布格局来看,福建水库水资源空间分布不均,沿海六市水库密度大于三个内陆市,大中型水库主要分布于福建西北部,蓄水量呈现西北多、东南少的特点.单位陆地面积水库数量沿海城市县区均多于内陆,而单位人口水库数量则相反;单位面积水库蓄水量沿海与内陆差异不大,而人均蓄水量则沿海大部分县区远小于内陆.仅以水库作为供水水源,不能满足沿海地区用水,但内陆地区供水充足.水库蓄水对河流水体的平均滞留时间为0.053~0.341 a,除晋江流域受水库蓄水强烈影响外,其他流域受水库中等程度影响.     

大华北地区二种不同空间分布类型的地震活动性分析

对大华北地区地震资料相对可靠的20世纪以来第三、第四活动期的地震活动做了分析,发现前后二地震活动期有着不同的空间分布类型, 但彼此联系密切又相对完整。通过对比研究发现, 二个活动期地震活动的主体区域基本上互不重复, 地震活动有等间距发生的特征, 认为这一现象对于分析今后地震活动的地点具有重要意义。     

基于GRACE的空间约束方法监测华北平原地下水储量变化

华北平原作为我国重要的工农业基地和政治经济中心,面临着严重的水资源危机.因此,开展对华北平原地下水储量变化的监测工作具有重要现实意义与科学价值.本文基于GRACE重力卫星的空间约束方法,研究了华北平原地下水储量变化的时空分布规律,并与地面水井实测与地下水模型结果进行了综合比较和分析.结果表明：2002—2014年,华北平原地下水存在明显的长期亏损,GRACE估计的亏损速率为-7.4±0.9 km³·a^-1,而地面水井资料估计的浅层地下水亏损速率为-1.2 km³·a^-1.对比两者之间的差异可以发现,华北平原的地下水亏损以深层地下水为主.2002—2008年,GRACE估计的华北平原地下水亏损速率为-5.3±2.2 km³·a^-1,这与华北平原两个地下水模型得到的平均亏损速率-5.4 km³·a^-1十分吻合.通过华北平原区域地下水模型的独立验证,说明GRACE可以有效评估华北平原的地下水储量变化趋势.除了长期亏损的趋势项之外,华北平原地下水还存在明显的年际变化特征,并与该地区年降雨量变化特征一致.在降雨偏少的2002年、2005—2009年和2014年,华北平原地下水储量显著减少.在空间分布上,GRACE结果表明,华北平原的地下水储量减少主要发生在山前平原和中部平原区,这也与水井实测资料和区域地下水模型结果较为吻合.与GRACE和区域地下水模型相比,目前的全球水文模型仍无法准确估计华北平原地下水变化的空间分布和亏损速率.上述研究表明,GRACE提供了评估华北平原地下水储量变化的重要监测手段.

     

Temporal and spatial distribution of dam failure events in China

Reservoirs play a vital role in economic development and flood control. Nevertheless, both human and natural factors may lead to dam failures with catastrophic consequences. Analyzing the data of dam failure events from 1954 to 2003 and using the method of energy spectrum analysis, this paper studies the periodicity of dam failures. The rate of failure of different dam ages is analyzed. The climate is the main factor affecting the rate of dam failure. Climate diagrams are used to analyze the spatial distribution of dam failure events in China. High rate of dam failure occurs with 25-year and 12.5-year periods. The distribution of the percentage of dam failure shows an L-shape as a function of service age. The first 5 years of operation is known as the ＂infant period＂, during which, the probability of dam failure is much higher than during any other periods. The failure rate in areas near or north to the 400 mm annual isopluvial line is notably higher than other areas. In areas with high temperature difference among seasons have a high annual average dam failure rate.     

华北地区未来强震概率统计分析

应用泊松模型的极值分布对华北地区的地震活动趋势进行估计和分析,结果表明,2008年前华北地区发生6级以上地震的危险性较大;2005年地震活动短期内可能还会持续目前较弱的态势,但未来1~2年内华北地区地震活动很有可能明显增强。