利用水位资料反演华北地区构造应力场变化   总被引：9，自引：0，他引：9  

孙小龙  刘耀炜  晏锐 《地震》2011,31(2):42-49

本文选取华北地区观测条件较好的63口水位观测井资料, 运用小波分析法去除各井水位资料中的短期高频信息, 提取出能反映水位多年动态变化的趋势信息, 并利用各井水位趋势变化数据反演出华北地区多年构造应力场变化图像, 结合其它水文资料, 探讨了华北地区近年来的构造应力场变化特征。  相似文献   

基于AERONET和OMI数据分析中国北方典型地区气溶胶单次散射反照率的变化趋势     

康颖  王莉莉  辛金元  陶明辉  宋涛  巩崇水  王跃思  李广 《气候与环境研究》2019,24(5):537-551

气溶胶单次散射反照率（SSA）表征气溶胶吸收特性,很大程度上决定了气溶胶辐射强迫的正负,对准确评估气候变化中的气溶胶辐射强迫具有重要意义。根据2004年10月至2016年12月地基AERONET（AERosol RObotic NETwork）和OMI（Ozone Monitoring Instrument）卫星数据,分析了中国北方典型地区（北京、香河、兴隆和兰州郊区）SSA的变化趋势以及两组数据的一致性。4个站AERONET和OMI 的SSA年均值分别为:北京0.89±0.04和0.90±0.04,香河0.89±0.04和0.91±0.04,兴隆0.92±0.04和0.91±0.04,兰州0.91±0.04和0.90±0.04。4个站点SSA季节变化一致,夏季高冬季低。SSA年际变化趋势分析时,因有效数据较少且为非正态分布,用月中位数代替月均值,同时需对数据进行筛选和去季节变化,结果显示北京和香河均有地基和卫星有效数据时间尺度不同的情况,而兴隆OMI和兰州AERONET满足趋势分析要求。在研究期间,4站SSA均呈上升趋势,说明近年来中国北方气溶胶的吸收性减弱,散射特性增强,尤其北京四季地基和卫星数据均呈上升趋势,但香河秋冬吸收性增强。同时,对AERONET和OMI两种反演算法得到的SSA一致性进行分析。香河结果差异较大,仅30%的数据在误差±0.03的范围内,55%在±0.05的范围内;北京分别为46%（±0.03）和68%（±0.05）,兴隆分别为50%（±0.03）和76%（±0.05）,兰州数据一致性较好,分别为51%（±0.03）和86%（±0.05）,总体来说是受人为活动影响比较明显的地区,数据一致性较差。  相似文献   

The increasing predominance of extreme precipitation in Southwest China since the late 1970s          下载免费PDF全文

Guowei Zheng  Yang Li  Quanliang Chen  Xin Zhou  Guolu Gao  Minggang Li  Ting Duan 《大气和海洋科学快报》2022,15(5):100227

Extreme precipitation events cause severe environmental and societal damage worldwide. Southwest China (SWC) is sensitive to such effects because of its overpopulation, underdevelopment, and fragile ecosystems. Using daily observations from 108 rain-gauge stations, the authors investigated the frequency of extreme precipitation events and their contribution to total precipitation in SWC since the late 1970s. Results indicate that total precipitation is decreasing insignificantly, but rainfall-events frequency is decreasing significantly, whereas the region is experiencing more frequent and intense extreme precipitation events. Note that although fewer stations are statistically significant, about 60% of the rain-gauge stations show an increasing trend in the frequency and intensity of extreme precipitation. Furthermore, there is an increasing trend in the contribution of total extreme precipitation to total precipitation, with extreme precipitation becoming dominant in the increasingly arid SWC region. The results carry important implications for policymakers, who should place greater emphasis on extreme precipitation and associated floods and landslides when drafting water-resource management policies.摘要本文分析了中国西南20世纪70年代末以来极端降水事件的频率, 强度及其对总降水的贡献. 结果表明, 该地区约60%的降水站点极端降水的频率和强度正在增加, 而大多数站点总降水频率明显减少. 同时极端降水总量对总降水量的贡献有显著增加的趋势, 极端降水在日益干旱的中国西南地区变得更具主导性. 研究结果提醒应更加重视极端降水及其可能引发的次生灾害, 如洪水, 山体滑坡等.  相似文献   

Identification of trends in rainfall,rainy days and 24 h maximum rainfall over subtropical Assam in Northeast India     

Deepak Jhajharia  Brijesh K. Yadav  Sunil Maske  Surajit Chattopadhyay  Anil K. Kar 《Comptes Rendus Geoscience》2012,344(1):1-13

Trends in rainfall, rainy days and 24 h maximum rainfall are investigated using the Mann-Kendall non-parametric test at twenty-four sites of subtropical Assam located in the northeastern region of India. The trends are statistically confirmed by both the parametric and non-parametric methods and the magnitudes of significant trends are obtained through the linear regression test. In Assam, the average monsoon rainfall (rainy days) during the monsoon months of June to September is about 1606 mm (70), which accounts for about 70% (64%) of the annual rainfall (rainy days). On monthly time scales, sixteen and seventeen sites (twenty-one sites each) witnessed decreasing trends in the total rainfall (rainy days), out of which one and three trends (seven trends each) were found to be statistically significant in June and July, respectively. On the other hand, seventeen sites witnessed increasing trends in rainfall in the month of September, but none were statistically significant. In December (February), eighteen (twenty-two) sites witnessed decreasing (increasing) trends in total rainfall, out of which five (three) trends were statistically significant. For the rainy days during the months of November to January, twenty-two or more sites witnessed decreasing trends in Assam, but for nine (November), twelve (January) and eighteen (December) sites, these trends were statistically significant. These observed changes in rainfall, although most time series are not convincing as they show predominantly no significance, along with the well-reported climatic warming in monsoon and post-monsoon seasons may have implications for human health and water resources management over bio-diversity rich Northeast India.  相似文献   

GIS的未来之我见   总被引：1，自引：0，他引：1  

戴立乾  陈娜  杨军强 《地理空间信息》2011,9(1):73-74,78

对当前地理信息系统的发展动态进行了分析,提出了未来GIS的发展呈现出的新特点、云计算GIS的发展趋势以及GIS和人们的生活密切相关.  相似文献   

Can a 25-year trend in Soudano-Sahelian vegetation dynamics be interpreted in terms of land use change? A remote sensing approach   总被引：3，自引：0，他引：3  

Agnès Bégué  Elodie VintrouDenis Ruelland  Maxime Claden 《Global Environmental Change》2011,21(2):413-420

This study is based on the premise that, in the Sahel/Sudanian belt of Africa, the main determinants of interannual variation in vegetation dynamics are rainfall and land cover type. We analyzed the spatio-temporal sensitivity of the NOAA-AVHRR 8 km-resolution vegetation index (NDVI) to (i) annual rainfall variability (0.5° × 0.5° resolution) acquired over a 25-year period (1982-2006); and (ii) land use changes in the different eco-climatic regions of the Bani catchment in Mali (130 000 km²). During the period 1982-2006, there was no clear trend in rainfall over the catchment, whereas there was a strong positive trend in the NDVI, both when the NDVI values were corrected using annual rainfall variability and when they were not. We divided the catchment into three eco-climatic regions based on the relationship between the annual NDVI and rainfall. In each region, we analyzed the observed greening in relation to changes in land use after correcting for the effect of annual rainfall on the NDVI. Results show that there is a mixed level of agreement between the land cover changes at the grid cell scale and the spatial pattern of the NDVI trend. Increased cropping does not explain the increase in the annual NDVI, except in the Sahelian part of the catchment. We hypothesize that the natural vegetation dynamics related to the non-linear rainfall patterns during the 25-year study period were responsible for these results.  相似文献   

山西高温天气的环流特征及流型配置研究     

苗爱梅  贾利冬  李苗  范光海 《山西气象》2011,(1):4-11

利用1958年-2008年高低空气象观测资料以及山西省气象信息中心归档的109站1958年-2008年的原始气象记录月报表及其信息化产品资料,分别以最高气温≥35℃、≥37℃、≥40℃为指标,研究山西高温日的时空分布、变化趋势及环流特征。结果表明：a）山西高温日最早出现在4月中旬,最晚出现在9月中旬,≥35℃、≥37℃和≥40℃的高温日6月下旬最多;b）高温日数有随纬度、随海拔的升高而减少,有西部多于东部、南部多于北部、盆地多于山区的空间分布特征。≥40℃的高温区域主要集中在运城和临汾地区;C）1984年-2008年,35℃以上的高温日数整体呈上升趋势;1979年-2008年,30年间高温站次以153站次,10a的趋势增多。20世纪90年代以后,不仅高温日数增多,而且高温持续时间、强度、范围都有增强趋势;d）影响山西高温的500hPa环流形势主要有副高纬向性、副高经向型以及大陆高压（脊）控制型3类。在特定的流型配置下,T850≥25℃、T700≥13℃,T850≥26℃、T700≥14℃,T850≥28℃、T700≥15℃,T850≥32℃、T700≥16℃是山西省不同区域、不同风向影响时,≥35℃、≥37℃、≥40℃高温天气预报的临界值。  相似文献   

近55年来宾市雷暴日数特征分析   总被引：3，自引：1，他引：2  

黄翠珍  黄芳  李荣迪 《气象研究与应用》2011,32(3):88-91

采用1956～2010年广西来宾市国家基本气象站常规地面气象观测资料,对雷暴日数特征进行了统计分析。结果表明,来宾市年雷暴日数在46～106d,年平均雷暴日数为72．4d;来宾市一年中任何一天都有可能出现雷暴天气,其中6、7、8月雷暴日数最多,约占全年雷暴日数的57．4％。小波分析显示,来宾年雷暴活动具有较强的9年周期...  相似文献   

http://www.sciencedirect.com/science/article/pii/S1674987111000156   总被引：1，自引：0，他引：1  

Xiaohuan Xi  Zhongfang Yang  Yujun Cui  Shumei Sun  Chengguang Yu  Min Li 《地学前缘(英文版)》2011,2(2):115-123

Employing the Unit Soil Carbon Amount (USCA) approach, soil carbon storage was calculated across the Northeast Plain of China based on the Multi-purpose Regional Geochemical Survey conducted in 2004 – 2006 (MRGS). The results indicated that the soil organic carbon (SOC) storage in topsoil (0 – 0.2 m), subsoil (0 – 1 m) and deep soil (0 – 1.8 m) was 768.1 Mt, 2978.4 Mt and 3729.2 Mt with densities of 3327.8 t/km2, 12,904.7 t/km2 and 16,157.5 t/km2, respectively. These values were consistent with national averages, whereas the soil carbon densities showed a clear increasing trend from the southern area of the Northeast Plain (Liaoning), to the middle (Jilin) and the northern Plain (Heilongjiang) — particularly in terms of topsoil carbon density, which increased from 2284.2, to 3436.7 and 3861.5 t/km2, respectively. In comparison to carbon data obtained from the Second National Soil Survey in 1984 – 1986 (SNSS), the topsoil SOC storage values from the MRGS were found to have decreased by 320.59 Mt (29.4%), with an average annual decline of 16.0 Mt (l.73%) over the 20 years. In the southern, middle and northern areas of the plain, soil carbon densities decreased by 1060.6 t/km2, 1646.4 t/km2 and 1300.2 t/km2, respectively, with an average value of 1389.0 t/km2 for the whole plain. These findings indicate that the decrease in soil carbon density varied according to the different ecosystems and land use types. Therefore, ratios of soil carbon density were calculated in order to study the carbon dynamic balance between ecosystems, and to further explore distribution characteristics, as well as the sequestration potential of SOC.  相似文献   

Recent water quality trends and a comparison to sediment-core records for two riverine lakes of the Upper Mississippi River basin: Lake St. Croix and Lake Pepin     

Brenda Moraska Lafrancois  Suzanne Magdalene  D. Kent Johnson 《Journal of Paleolimnology》2009,41(4):603-622

Long-term water quality monitoring data from two riverine lakes in the Upper Mississippi River basin, Lakes St. Croix and Pepin, were analyzed to compare the long-term average water quality conditions and land use distributions, water quality trends and loads at lake inlets and outlets, trends from long-term versus short-term monitoring records, and the ability of paleolimnological cores to accurately infer lake water quality conditions. During the 1976–2004 period, the long-term average concentrations of nutrients, suspended solids, and chlorophyll-a were consistently lower at the Lake St. Croix inlet versus the Lake Pepin inlet, which drains a greater proportion of urban and agricultural runoff. Despite these differences, nutrient trends were similar at the inlets to both lakes; reductions in total phosphorus and ammonium concentrations were attributed to improvements in point source technologies, whereas increasing nitrate concentrations were attributed to both point source changes and nonpoint source increases. Despite improvements in several water quality variables, nitrate concentrations are increasing in both lakes, sediment trends indicate persistent nonpoint source inputs to Lake Pepin, and current total phosphorus concentrations remain well above pre-1950s levels in both lakes. Since urban development and agriculture are increasing in the Lake St. Croix and Lake Pepin Watersheds, continued point source regulation and additional nonpoint source control efforts will be needed to further improve water quality in these lakes. The 1976–2004 trends for most water quality variables were similar at inlet versus outlet sites on Lake St. Croix. Trends at Lake Pepin inlet versus outlet sites were less similar, but data availability limited the comparison to the 1993–2003 period. While the truncated data record highlighted short-term trends in both lakes, the full data record was most useful for exploring general patterns in water quality. Length of monitoring record affected our ability to detect trends at the inlets to both lakes, and altered the magnitude of detected trends. During the two decades of the 1980s and 1990s, paleolimnological estimates of retained phosphorus loads were similar to those estimated from recent water quality monitoring. These similarities support the use of paleolimnological approaches to infer past water quality conditions in Lakes St. Croix and Pepin. This is one of eight papers dedicated to the “Recent Environmental History of the Upper Mississippi River” published in this special issue of the Journal of Paleolimnology. D. R. Engstrom served as guest editor of the special issue.  相似文献