1965—2017年东江中上游流域气温变化特征分析          下载免费PDF全文

曾钦文  潘心顺  魏璐  董彤 《气象与减灾研究》2019,42(1):24-31

利用东江中上游江流域8个气象站1965—2017年逐日气温资料,采用线性趋势分析、小波分析和Mann-Kendall突变检验等方法分析了东江中上游流域气温的变化特征。结果表明：1965—2017年东江中上游流域年平均气温以0.17 ℃/(10 a)速率显著上升;秋季平均气温上升最显著,冬季、夏季次之,春季不显著;年高温日数以3 526 d/(10 a)的速率显著增多。年与季平均气温和年高温日数均存在突变,各气象站年与季平均气温均大致呈自南向北依次递减分布。上游的高温日数略多于中游。各气象站年平均气温上升趋势均显著,春、夏季均以连平为中心上升幅度最大,秋季为上升趋势最明显的季节,冬季以连平为中心上升趋势最显著。各气象站年高温日数增多趋势均显著,增幅最大为连平,最小为龙川。年平均气温存在4、8—9、13—14、18—19 a的周期变化,高温日数存在2、6、10—11、25—26 a的周期变化。  相似文献   

A nonparametric view of generalized covariances for kriging     

Noel Cressie 《Mathematical Geology》1987,19(5):425-449

Fitting trend and error covariance structure iteratively leads to bias in the estimated error variogram. Use of generalized increments overcomes this bias. Certain generalized increments yield difference equations in the variogram which permit graphical checking of the model. These equations extend to the case where errors are intrinsic random functions of order k, k=1, 2, ..., and an unbiased nonparametric graphical approach for investigating the generalized covariance function is developed. Hence, parametric models for the generalized covariance produced by BLUEPACK-3D or other methods may be assessed. Methods are illustrated on a set of coal ash data and a set of soil pH data.  相似文献   

乌塘鳢Bostrichthys　sinensis（Lacépède）的年龄研究     

叶富良  张健东  朱龙  苏乃萍 《广东海洋大学学报》1994,(2)

研究乌塘鳢年龄的鉴定材料采用胸鳍支鳍骨。结果表明：胸鳍支鳍骨上骨化环的数目与年轮数目相一致，体长频率分布与各年龄组体长分布曲线基本相符。用胸鳍支鳍骨的骨化环来鉴定乌塘鳢的年龄是可信的。  相似文献   

21世纪云南第1次大震活跃期的趋势预测     

罗葆荣 《天文研究与技术》2003,(3):69-72

在太阳活动与地震活动相关研究的基础上指出:在周期性太阳活动的调控下,地震活动也显示出与太阳活动相关的周期性变化。云南22年的地震周期在20世纪形成了4个大震活跃期和4个相对平静期。根据地震活动和太阳活动的若干相关规律,对云南地区在本世纪第1次大震活跃期的到来作了趋势性预测:云南在本世纪第1次大震活跃期的第1个大震(M=7.0左右)将于2012年到来,那时正是太阳活动第24周下降段的开始,离上次大震活跃期的最后一个大震(丽江,M=7.0,1996年)恰好是16年。在该大震活跃期里,还将发生若干个M=7.0左右的大震和一些较小的地震,其大震爆发的时间将遵循Tx=(Tn-Tn-1)1/2(a年)的非线性经验规律发生。  相似文献   

中国东北及邻近地区夏半年极端暖事件的时空和环流特征分析     

付强  石剑  徐梦阳  艾阳  钱维宏 《热带气象学报》2022,38(1):101-112

夏半年（5—10月）是我国东北农作物生长的关键期,但偏高的气温尤其是大范围极端偏暖事件会对农业生产造成不良影响。基于强度、范围和持续时间等指标,对1980—2019年夏半年发生在我国东北及其邻近地区的16个极端暖事件进行分析。结果表明,东北及邻近地区的极端暖事件的强度和频率呈明显增加的趋势,夏初（5—6月）和秋初（9—10月）发生的暖事件频次较多。地面极端增暖事件发生时,东北区域的西北侧大陆地面低压异常和东侧西北太平洋海上高压异常导致东北地区出现异常偏南风及暖平流;对流层至平流层呈现出准正压的结构,最大位势高度异常中心多出现在250 hPa附近,其下方的正温度异常（暖气柱）会延伸到地面,有利于地面异常增温。暖事件发生时,地面增暖区位于对流层上层急流入口区的左侧,利于下沉气流出现。上述大气温压场扰动结构和环流特征通过影响短波辐射和绝热增温过程,共同导致地面极端暖事件的发生。在预报意义上,有90%以上的东北极端暖事件可以在250 hPa上至少提前10天追踪到位势高度的扰动信号。   相似文献   

基于神经网络和多标度特征分析的古滑坡变形预测及趋势评价     

田倩  吴健  赵东 《大地测量与地球动力学》2022,42(10):1056-1062

提出一种新的古滑坡变形预测方法。首先结合集合经验模态分解(EEMD)和奇异值分解(SVD)对古滑坡变形数据进行分解,然后利用分项组合神经网络预测古滑坡复活区的变形,最后利用多重分形消除趋势波动分析(MF-DFA)进行古滑坡多标度趋势评价。以王家坡滑坡为例分析本文方法的有效性。结果表明,组合分解模型EEMD-SVD较单项分解模型具有更强的数据分解能力,可有效实现滑坡变形数据的信息分解;基于神经网络的分项组合预测模型适用于滑坡变形预测,所得预测结果的相对误差基本在2%左右,预测精度较高,且外推预测显示滑坡变形仍会进一步增加,增加速率为1.23~1.36 mm/周期;MF-DFA模型的多标度特征分析结果显示,滑坡变形具有多重分形特征,变形有进一步增加的趋势,这与预测结果较为一致,可佐证前述预测结果的准确性。  相似文献   

Research Progress of Relative Humidity and Its Changing Annual Cycle     

Da Nian  Qimin Deng  Zuntao Fu 《地球科学进展》2018,33(7):762-774

Studies on the characteristics of relative humidity annual cycle change include the frequency, phase, and amplitude of the time series and their changes. The effective diagnosis of the relative humidity annual cycle can provide important help in the monitoring and regulation of seasonal haze, the spatial distribution of epidemic outbreaks and their prevention and control, and the real-time forecasting and decision-making of monsoon precipitation. Different from studies on the trend of the relative humidity, the diagnosis in the annual cycle is scarce. This paper summarized the research status of relative humidity and its annual cycle, introduced several current methods for extracting common signals, and evaluated the feasibility of these methods for extracting annual cycle signals. Due to the time-varying characteristics of the annual cycle of relative humidity and complex structures such as asymmetric triangular waves, square-like waves, and state transients, harmonic-based extraction methods are difficult to succeed. The nonlinear signal extraction method with high noise immunity will solve this problem. At present, the relative humidity annual cycle studies urgently need to be improved and improve the quality of relative humidity observation data, accurately extract and quantify the time-varying characteristics and complex structure of the annual cycle. Moreover, combining the dynamic process and statistical analysis, we also need to study the physical mechanism of the change of relative humidity annual cycle (frequency, phase, amplitude, etc.) in China.  相似文献   

Composite methodology for interpreting sediment transport pathways from spatial trends in grain size: A case study of the Lithuanian coast          下载免费PDF全文

Milda Kairytė  Rodney L. Stevens 《Sedimentology》2015,62(3):681-696

To achieve a more robust interpretation of sediment conditions and transport based on grain size, this study combines the perspectives of two different interpretation techniques that have been developed separately and applied in the literature: (i) ‘grain size trend analysis’ interprets changes between interrelated sampling sites assuming that sediment in the direction of transport should become either coarser, better sorted and more positively skewed, or finer, better sorted and more negatively skewed; and (ii) the ‘population anomalies’ method, which estimates the balance between erosion and accumulation processes at each sampling site based on individual site deviations compared with average values for grain‐size parameters in the area of interest. The simultaneous use of both approaches enables sedimentological conditions and transport alternatives to be distinguished. This improvement is necessary because site‐specific changes and general textural trends provide information that complements the strengths and weaknesses of each perspective. The methods are implemented here using two‐dimensional Geographic Information System tools and illustrated for the Lithuanian coast. Grain‐size characteristics of 712 surface samples of sandy sediments are used to interpret sediment transport pathways and predominant sedimentological conditions in the Lithuanian coastal zone. In general, coast‐parallel sediment transport dominates the entire investigation area, although wave‐induced movement perpendicular to the coastline is inferred in the shallow nearshore zone. The deepest areas offshore are characterized by sea floor erosion in the north, whereas an accumulation zone occurs in the relatively deep central part of the study area.  相似文献   

光谱指数趋势面的城市地表温度降尺度转换     

王祎婷  谢东辉  李亚惠 《遥感学报》2014,18(6):1169-1181

针对城市及周边区域建造区和自然地表交织分布的特点,探讨了利用归一化植被指数(NDVI)和归一化建造指数(NDBI)构造趋势面的地表温度(LST)降尺度方法,以北京市市区及周边较平坦区域为例实现了LST自960 m向120 m的降尺度转换。分析了LST空间分布特征及NDVI、NDBI对地物的指示性特征;以北京市四至六环为界分析NDVI、NDBI趋势面对地表温度的拟合程度及各自的适用区域;在120 m、240 m、480 m和960 m 4个尺度上评价了NDVI、NDBI和NDVI+NDBI趋势面对LST的拟合程度和趋势面转换函数的尺度效应;对NDVI、NDBI和NDVI NDBI等3种方法的降尺度结果分覆盖类型、分区域对比评价。实验结果表明结合两种光谱指数的NDVI NDBI方法降尺度转换精度有所改善,改善程度取决于地表覆盖类型组合。  相似文献   

海南昌化江入海口底表沉积物粒度特征及输运趋势     

王雪木  瞿洪宝  熊元凯  吕琳  胡克 《现代地质》2022,36(1):88-95

对海南岛昌化江入海口110个底表沉积物样品进行了粒度分析,并利用二维沉积物粒径趋势分析模型对沉积物粒度参数开展趋势分析.研究结果表明,按照Folk沉积物分类三角图解法,昌化江入海口外底表沉积物可划分为含砾砂、砂、砾质泥质砂、砂质砾、粉砂、泥、砂质泥、砾质砂、砂质粉砂和粉砂质砂共10种沉积物类型,其中砂和砾组分的分布范围...  相似文献