Q-factor estimation in CMP gather and the continuous spectral ratio slope method

The attenuation factor or quality factor(Q-factor or Q) has been used to measure the energy attenuation of seismic waves propagating in underground media. Many methods are used to estimate the Q-factor. We propose a method to calculate the Q-factor based on the prestack Q-factor inversion and the generalized S-transform. The proposed method specifies a standard primary wavelet and calculates the cumulative Q-factors; then, it finds the interlaminar Q-factors using the relation between Q and offset(QVO) and the Dix formula. The proposed method is alternative to methods that calculate interlaminar Q-factors after horizon picking. Because the frequency spectrum of each horizon can be extracted continuously on a 2D time–frequency spectrum, the method is called the continuous spectral ratio slope(CSRS) method. Compared with the other Q-inversion methods, the method offers nearly effortless computations and stability, and has mathematical and physical significance. We use numerical modeling to verify the feasibility of the method and apply it to real data from an oilfield in Ahdeb, Iraq. The results suggest that the resolution and spatial stability of the Q-profile are optimal and contain abundant interlaminar information that is extremely helpful in making lithology and fluid predictions.

Spatio-temporal Variation Characteristics of Extreme Climate Events and Their Teleconnections to Large-scale Ocean-atmospheric Circulation Patterns in Huaihe River Basin,China During 1959–2019

Huaihe River Basin(HRB) is located in China’s north-south climatic transition zone,which is very sensitive to global climate change.Based on the daily maximum temperature,minimum temperature,and precipitation data of 40 meteorological stations and nine monthly large-scale ocean-atmospheric circulation indices data during 1959–2019,we present an assessment of the spatial and temporal variations of extreme temperature and precipitation events in the HRB using nine extreme climate indices,and analyze the teleconnection relationship between extreme climate indices and large-scale ocean-atmospheric circulation indices.The results show that warm extreme indices show a significant(P < 0.05) increasing trend,while cold extreme indices(except for cold spell duration) and diurnal temperature range(DTR) show a significant decreasing trend.Furthermore,all extreme temperature indices show significant mutations during 1959-2019.Spatially,a stronger warming trend occurs in eastern HRB than western HRB,while maximum 5-d precipitation(Rx5day) and rainstorm days(R25) show an increasing trend in the southern,central,and northwestern regions of HRB.Arctic oscillation(AO),Atlantic multidecadal oscillation(AMO),and East Atlantic/Western Russia(EA/WR) have a stronger correlation with extreme climate indices compared to other circulation indices.AO and AMO(EA/WR) exhibit a significant(P < 0.05) negative(positive)correlation with frost days and diurnal temperature range.Extreme warm events are strongly correlated with the variability of AMO and EA/WR in most parts of HRB,while extreme cold events are closely related to the variability of AO and AMO in eastern HRB.In contrast,AMO,AO,and EA/WR show limited impacts on extreme precipitation events in most parts of HRB.

基于Sen+Mann-Kendall的北京植被变化趋势分析

基于1998年到2011年长时序SPOTVEGETATION归一化植被指数数据,采用一元线性回归斜率变化法和Sen+Mann-Kendall法对北京地区的植被变化趋势做了时空分析。实验结果表明:在1998年到2011年期间,北京市城区、延庆县、怀柔区和平谷区的植被变化趋势显著上升;而植被恶化区则集中在北京市城区北部、东部和南部,并以马蹄形包围北京市区。两种方法实验结果在植被上升(下降)区域具有一致性。同时,Sen+Mann-Kendall法以其良好的抗噪性和对数据分布无要求性可广泛应用到其他区域的植被变化趋势分析中。

Sen’s斜率估计与Mann-Kendall法在设备运行趋势分析中的应用

基于某企业设备运行时轴承状态自上次检修以来的历史数据,采用Sen’s斜率估计与Mann-Kendall检验相结合的方法对其运行趋势进行分析,并与一元线性回归法分析结果相比较。结果表明,Sen’s斜率估计与Mann-Kendall法相结合,适用于设备运行状态的趋势分析,可在基于状态监测的预防性维修工作中推广应用。

Estimating trends of the Mediterranean Sea level changes from tide gauge and satellite altimetry data (1993-2015)

The impact of climate change on sea level has received a great deal of attention by scientists worldwide. In this context, the problem of sea levels on global and regional scales have been analyzed in a number of studies based on tide gauges observations and satellite altimetry measurements. This study focuses on trend estimates from 18 high-quality tide gauge stations along the Mediterranean Sea coast. The seasonal Mann-Kendall test was run at a 5% significance level for each of the 18 stations for the period of 1993-2015 (satellite altimetry era). The results of this test indicate that the trends for 17 stations were statistically significant and showed an increase (no significant trend was observed only at one station). The rates of sea level change for the 17 stations that exhibit significant trends, estimated using seasonal Sen's approach, range after correction for Vertical Land Motion (VLM) from 1.48 to 8.72 mm/a for the period 1993-2015. Furthermore, the magnitude of change at the location of each tide gauge station was estimated using the satellite altimetry measurements. Thus, the results obtained agree with those from the tide-gauge data analysis.

东北三省NDVI时空变化特征及对气候因子的响应

中国东北地区是全球气候变化最敏感的区域之一,了解植被的时空变化及对气候因子的响应对东北地区生态环境的构建和评价具有重要意义,对全球气候变化的响应也具有重要的指示作用。基于MODIS归一化差值植被指数(NDVI),利用Theil-Sen斜率估计、Mann-Kendall检验和Hurst指数开展2000—2021年东北三省NDVI时空演变特征及未来变化趋势研究,并通过相关分析方法研究NDVI对气候因子的响应。结果表明:2000—2021年NDVI整体均值为0.391,季节上呈现出春冬季低、夏秋季高的变化趋势,空间上呈现出西低东高的变化趋势;2000—2021年,NDVI年均增长率为0.003 a~(-1),而2010—2021年,NDVI整体呈现极显著上升趋势,年均增长率为0.006a~(-1);东北三省86.93%面积的NDVI在未来可持续增长,表明未来植被生长态势较好;相关分析表明,NDVI与气候因子在空间尺度上存在依赖性,气温与NDVI有更好的相关性;在东北三省大部分地区,气温和降水均对NDVI变化有正贡献,且两者的贡献相当,但在空间上存在着差异。

华北地区干旱时空变化及其对植被NDVI的影响

采用2000−2020年华北地区90个气象站点气象观测数据构建标准化降水蒸散指数(SPEI),选取30m空间分辨率的归一化植被指数栅格数据提取归一化植被指数(NDVI),量化植被覆盖情况,采用Sen’s斜率估计、Mann-Kandall检验、相关性分析、Copula-Bayesian条件概率公式等对华北地区植被干旱敏感性进行分析。结果表明:(1)华北大部分地区SPEI值呈极显著增长,华北北部部分地区SPEI值呈极显著下降;华北西部及北部地区NDVI值呈极显著增长,其余地区呈极显著下降;(2)华北地区干旱与植被以不显著空间集聚为主,小部分地区出现干旱与植被呈高值集聚和低值集聚;(3)华北地区总体上年尺度SPEI与NDVI相关性较好,植被对干旱的响应速度较慢,敏感程度较低,河南部分地区月尺度SPEI与NDVI相关性较好,植被对干旱敏感程度较高,NDVI与SPEI的联合分布函数最符合Clayton Copula函数;(4)华北地区植被低覆盖度出现的可能性随着干旱程度减轻而不断减少,较低覆盖度出现的可能性在极旱至中旱时不断增加,从中旱至轻旱时不断减少,植被中覆盖度、较高覆盖度和高覆盖度的可能性都随着干旱减轻而增加。

Trend Analysis of Rainfall in Ganga Basin, India during 1901-2000

Shortage of water in the river in relation to rainfall change plays a pivotal role in water sharing like Ganga. In attempt to understand the rainfall changes, Mann-Kendall test and Sen’s slope estimation on hundred years’ (1901-2000) rainfall data of 236 districts in entire Ganga basin were run. Half of the districts showed a decreasing trend in annual rainfall in which 39 districts were statistically significant. During pre-monsoon (Jan.-May), 78% of the total districts showed the decreasing trend with the significance of 54 districts. A majority of the districts under the Kosi, Gandak and Sone sub-basins showed the significant negative trend in annual, pre-monsoon and post-monsoon season. So, there need some districts’ and sub-basins’ wise strategies to cope with the situation in the context of climate change.

Detecting Changes in Hydro-Climatic Variables during the Last Four Decades (1975-2014) on Downstream Kaduna River Catchment, Nigeria

This study aimed to detect trends in the long-term hydro-climatic series using non-parametric methods. The annual and seasonal linear trends of rainfall, temperature, runoff, water level and evaporation were analysed for stations in downstream Kaduna River Basin during 1975-2014. The non-parametric Mann-Kendall and Sen’s estimator of slope procedures were adopted to identify if there exists an increasing or decreasing trend with their statistical significance at 95% level of confidence. The datasets were checked to account for auto-correlation prior to determining trends using Mann-Kendall test. The existence of abrupt changes was detected by means of Cumulative Sum Charts and Bootstrapping analysis. The results of study indicated increasing trends for seasonal and annual temperature and runoff series. Water level and evaporation revealed statistically decreasing trends both on annual and seasonal periods. However, for the period 1975 to 2014 no significant distinctive trend was observed for rainfall at the investigated stations. Change-points in time series were identified in all the investigated hydro-climatic records for the sub-basin. Generally, the detection of the trend for hydro-climatic variables by Mann-Kendall test conforms to Sen’s test results. It is concluded that the basin is sensitive to climate variability and water stress impacts which will affect food security. So, it would be necessary to make adjustments in the adaptive water-use strategies being adopted at present in the catchment.

Trend in Observed and Projected Maximum and Minimum Temperature over N-W Himalayan Basin

Recently, study in past trends of climate variables gained significant consideration because of its contribution in adaptions and mitigation strategies for potential future changes in climate, primarily in the area of water resource management. Future interannual and inter-seasonal variations in maximum and minimum temperature may bring significant changes in hydrological systems and affect regional water resources. The present study has been performed to observe past(1970-2010) as well as future(2011-2100)spatial and temporal variability in temperature(maximum and minimum) over selected stations of Sutlej basin located in North-Western Himalayan region in India. The generation of future time series of temperature data at different stations is done using statistical downscaling technique. The nonparametric test methods, modified Mann-Kendall test and Cumulative Sum chart are used for detecting monotonic trend and sequential shift in time series of maximum and minimum temperature. Sen's slope estimator test is used to detect the magnitude of change over a period of time on annual and seasonal basis. The cooling experienced in annual TMax and TMin at Kasol in past(1970-2010) would be replaced by warming in future as increasing trends are detected in TMax during 2020 s and 2050 s and in TMin during 2020 s, 2050 s and 2080 s under A1 B and A2 scenarios. Similar results of warming are also predicted at Sunnifor annual TMin in future under both scenarios which witnessed cooling during 1970-2010. The rise in TMin at Rampur is predicted to be continued in future as increasing trends are obtained under both the scenarios. Seasonal trend analysis reveals large variability in trends of TMax and TMin over these stations for the future periods.

A Trend Analysis of Temperature and Rainfall to Predict Climate Change for Northwestern Region of Bangladesh

Bangladesh is one in all the foremost climate vulnerable countries of the world. In recent years, climate change studies over the country get plenty of attention by the researchers and policy makers. A substantial quantity of global climate change studies over the country use climate models to estimate future projections and uncertainties. Maximum temperature, precipitation and their potential future changes are evaluated in an ensemble of the 5th Phase Coupled Model Inter-comparison Project (CMIP5) within the Intergovernmental Panel on Climate Change (IPCC) diagnostic exercise for the Fifth Assessment Report (AR5) and the available historical data collected by the Bangladesh Meteorological Department (BMD) during the period 1981-2008 in the north-western region of Bangladesh and also the comparison between these two values. It has been found that average maximum temperature shows a positive trend of increase at a rate of 0.29°C and 5.3°C per century respectively, for BMD data and MPI-ESM-LR (CMIP5) model data. But the rainfall is decreasing at a rate of 8.8 mm and 40.1 mm per century respectively for BMD data and MPI-ESM-LR (CMIP5) model data. It is seen that July was the maximum monsoon rainfall month and January was the lowest rainfall month. The peak frequency is slightly smaller than 12 months, which indicates that the major events are occurring before ending a year compared to the previous year. According to MPI-ESM-LR (CMIP5) model data, future normal temperature on north-western region will be increased at a rate of 1.62°C during the period 2040-2100.

Mediterranean Sea level trends from long-period tide gauge time series

The main purpose of this study is to highlight, on the basis of statistical tests, the significant long-term changes of the Mediterranean Sea level, through the analysis of historical tide gauge records. In this framework, 14 tide gauge monthly series selected from the Permanent Service of the Mean Sea Level(PSMSL) database were used. The search for the presence or not of trends within these series, that have a temporal coverage from 59 to 142 years, was carried out using the Mann-Kendall test and the Sen’s slope estimator. The obtained results show that the Split Rt Marjana series are the only ones which does not exhibit a significant trend. The other 13 series show significant increasing trends. This result seems sufficient to suppose the presence, in the past century, of a new climatic phase on the scale of the Mediterranean basin, where the rising sea level is one of the consequences.

Inter-annual variation of streamflow,precipitation and evaporation in a small humid watershed(Chengcun Basin,China)

For sustainable water resource management,it is important to determine the relationship between streamfl ow and other variables that infl uence availability of water resources.However,many catchments do not have suffi cient data to allow for a more detailed study of these relationships.We faced a similar challenge in the Chengcun Basin(limited historical data: from 1986–1999); and therefore we used a new approach to overcome this.We found that,using nonparametric trend methods in conjunction with the climate elasticity analyses and the 2D visualization of hydrologic data,it is possible to assess the relationships between streamfl ow and other hydro-climatic variables.In the past,streamfl ow trends in the basin were more correlated with precipitation than with potential evapotranspiration(PET).In addition,there is a gradual shift in the hydrological regime of the catchment,which may affect the occurrence of available water resources and activities that depend on them.In addition,based on our climate sensitivity analyses,the streamfl ow is dependent and more sensitive to variations in precipitation than to PET(δQ=0.79δP+0.42δE; precipitation elasticity,ε P=1.32; PET elasticity,ε E=-2.10).Therefore pending more detailed studies,the use of our approach will provide a rapid means to assess the variation of water resources(streamfl ow)in a watershed.In the future,we hope to carry out related research in other watersheds and also perform a more detailed studies to improve upon the results of this study.

Variation characteristics of extreme precipitation from 1955 to 2015 in Shijiazhuang City,Hebei Province

In order to give guidelines for the execution of countermeasures in response to extreme precipitation events.the tempo-spatial variation characteristics of extreme precipitationare are analyzed by 11 extreme precipitation indexes during the past 60 years(1955-2015)in Shijiazhuang City.The results showed that the extreme precipitation of Shijiazhuang City generally showed a downward trend in the past 60 years,and the wet day precipitation(PRCPTOT)exhibited the most obvious downward trend.There were significant spatial differences in the trend of extreme precipitation indexes.According to the spatial superposition of the historical trend of extreme precipitation index and Hurst index,the extreme precipitation intensity indexes in most areas of Shijiazhuang city will continue to decline in the future,and the extreme precipitation intensity indexes in some central areas will continue to rise.

Analysis of Trends in Drought with the Non-Parametric Approach in Vietnam: A Case Study in Ninh Thuan Province

A quantitative study was used in the study of the tendency to change drought indicators in Vietnam through the Ninh Thuan province case study. The research data are temperature and precipitation data of 11 stations from 1986 to 2016 inside and outside Ninh Thuan province. To do the research, the author uses a non-parametric analysis method and the drought index calculation method. Specifically, with the non-parametric method, the author uses the analysis, Mann-Kendall (MK) and Theil-Sen (Sen’s slope), and to analyze drought, the author uses the Standardized Precipitation Index (SPI) and the Moisture Index (MI). Two Softwares calculated in this study are ProUCL 5.1 and MAKENSEN 1.0 by the US Environmental Protection Agency and Finnish Meteorological Institute. The calculation results show that meteorological drought will decrease in the future with areas such as Phan Rang, Song Pha, Quan The, Ba Thap tend to increase very clearly, while Tam My and Nhi Ha tend to increase very clearly short. With the agricultural drought, the average MI results increased 0.013 per year, of which Song Pha station tended to increase the highest with 0.03 per year and lower with Nhi Ha with 0.001 per year. The forecast results also show that by the end of the 21st century, the SPI tends to decrease with SPI 1 being −0.68, SPI 3 being −0.40, SPI 6 being −0.25, SPI 12 is 0.42. Along with that is the forecast that the MI index will increase 0.013 per year to 2035, the MI index is 0.93, in 2050 it is 1.13, in 2075 it will be 1.46, and by 2100 it is 1.79. Research results will be used in policymaking, environmental resources management agencies, and researchers to develop and study solutions to adapt and mitigate drought in the context of variable climate change.

The Impact of Climate Change on Rainfall Patterns in Ghana:A Zoning Adaptation Strategy through Developing Agroforestry

As a developing country in Africa,the effect of climate change is one of the sufferings of Ghana.The effect is much felt in rainfall variability because of the country over reliance on rainfall for agriculture.While various researches have studied the impact of climate change in Ghana,few among them have extended to its impact on rainfall pattern across all the ecological zones in the country.The trends in the rainfall from seven selected meteorological stations across all the ecological zones were analyzed using data from the NASA satellite.The Mann-Kendall and Sen’s Slope Test were used for the analysis.The study found decreasing trend in most of the monthly and yearly rainfall pattern across the ecological zones,and suggested cashew agroforestry as a zoning adaptation strategy.

Assessment of Meteorological Drought in Climate Variability Context within the Comoe River Transboundary Watershed

In the context of climate variability resulting in a decrease in rainfall with a severe drought, a spatio-temporal study of this phenomenon remains imperative for the efficient management of water resources. This paper aims to assess the long-term rainfall drought trend and breakpoints within the Comoe River watershed. From monthly rainfall data series (1960-2000), Standardized Precipitation Index (SPI) values were calculated for a time scale of 3 months (SPI.3). Statistical tests for breaks (CUSUM, and t-Student) and trends (Man-Kendall and Linear Regression) as well as the Sen’ slope method for estimating the magnitude of trends was applied. The breaks dates observed are mostly located after the 1970s. Based on SPI.3 values below the threshold of 0.84 chosen as an indicator of drought, rarely has more than half of the catchment area been affected by drought. The average watershed affected is about 20% over the study period (1960-2000). The most representative years, in terms of spatial expansion of the drought, in decreasing order of importance are: 1983, 1992, 1972 and 1982. The years 1982 and 1983 stand out for their exceptional condition, as the drought-affected 50% to 90% of the total catchment area. SPI.3 series from 1960 to the various break dates recorded slopes between -0.01 and 0.00 with a slight drought trend for most of the catchment. After the break periods, almost the entire northern part of the basin is characterized by slight moisture with Sen’s slopes between 0.000 and 0.005. The southern part will remain slightly subject to normal rainfall conditions.

四川省近60年降水时空演变规律

根据四川省30个气象站点1958—2017年的逐日降水资料,采用滑动平均法、Mann-Kendall趋势检验法、Sen′s坡度估算法、小波分析法和相对重要性分析法,研究了年际尺度和年内尺度上的降水变化特征及影响年际降水变化的主导因素。结果表明:①降水量的年际分布不均匀,降水序列波动性较大,并以每年0.198 mm的速率减少。②年际间丰枯年份交替变化且分配较为均匀,变化主周期为28年,同时存在13年和8年两个次周期。③降水量空间分布差异大,整体上东多西少、南多北少,且由东南向西北逐渐减少;降水中心位于乐山市西部。④年降水集中于夏季,秋季次之,其中春夏两季降水量呈上升趋势,秋冬两季降水量呈下降趋势,总体上看四季降水量变化趋势不明显;7月降水量最大,相应尺度上的月降水量与日降水量呈对称分布。⑤降水年际变化主要受降水强度和降水频率的共同影响,以降水频率影响占主导的区域分布在西部的高山高原地区,以降水强度影响占主导的区域则集中于东部盆地地区。

中国主要城市居民住房支付能力演化特征研究

运用房价收入比、滑动T检验和Sen’s斜率估计等方法,对中国27个大中城市2001—2019年的居民住房支付能力演化特征进行了研究,分析了城市居民住房支付能力演化特征与中国房地产调控的关联性。结果表明:(1)中国主要城市的居民住房支付能力在研究期内总体呈较明显的减弱趋势,居民住房支付能力等级“持续下降”和“越级下降”的现象较普遍,居民住房支付能力呈“加速下降”演化特征的城市占比达18.52%。(2)不同城市在居民住房支付能力等级演化特征、房价收入比演化阶段及阶段性演化趋势3个维度上存在较明显的差异性。(3)总体而言,城市居民住房支付能力演化阶段与中国房地产调控政策做出重大调整和地方出台重要房地产调控政策的时间点存在较强关联,住房支付能力的阶段性演化趋势与中国房地产发展情况相一致。研究呼吁建立健全城市居民住房支付能力评估监测制度,及时掌握主要城市居民住房支付能力及其演化规律。坚持“房住不炒”和“稳房价”的总体定位,科学合理制定房地产调控的“一揽子”政策,分区、分类推进城市居民住房支付能力提升工程。

1960-2011年河西走廊地表干湿状况的时空变化及影响因素

[目的]为了探讨河西走廊地区地表干湿状况对气候变化的响应。[方法]利用河西走廊地区14个气象站1960—2011年逐日气象数据,基于FAO推荐的Penman—Monteith模型计算河西走廊各气象站的参考蒸散量和湿润指数,采用Sen’s斜率和Mann—Kendall趋势检验方法,分析河西地区地表干湿的时空变化特征,探讨影响湿润指数变化的主导因子。[结果]河西走廊地表多年平均干湿指数为0.00~0.56,且52a来河西走廊湿润指数整体呈增加趋势;湿润指数的变化具有明显地域性差异。各季节湿润指数亦整体呈增加趋势,以冬季增幅最大,秋、春次之,而夏季变化最小。[结论]河西走廊地区气候属于干旱,52a来湿润指数略有增大,其主要原因是降水的增加和风速的减小。