华北地台北缘中段中上志留统与白乃庙群接触关系及其滑断构造

华北地台北缘中段中上志留统与中元古代自乃庙群接触关系为角度不整合,且沿角度不整合面发生了构造叠加作用,产生了滑断构造。该滑断构造具有宏观、微观变形组构,并且控制了一系列金矿点(矿化点)的分布,是一条重要的金矿化带。     

对1991—1992年厄尔尼诺事件形成的一种看法

本文对１９９１－１９９２年厄尔尼诺事件前兆及形成过程进行了分析，与１９８２－１９８３年和１９８６－１９８７年厄尔尼诺事件进行了对比。对自西向东传播的厄尔尼诺事件的形成特点及传播规律进行了解释。     

Investigating the correlation between radar backscatter and in situ soil property measurements

Utilizing remote sensing techniques to extract soil properties can facilitate several engineering applications for large-scale monitoring and modeling purposes such as earthen levees monitoring, landslide mapping, and off-road mobility modeling. This study presents results of statistical analyses to investigate potential correlations between multiple polarization radar backscatter and various physical soil properties. The study was conducted on an approximately 3 km long section of earthen levees along the lower Mississippi river as part of the development of remote levee monitoring methods. Polarimetric synthetic aperture radar imagery from UAVSAR was used along with an extensive set of in situ soil properties. The following properties were analyzed from the top 30–50 cm of soil: texture (sand and clay fraction), penetration resistance (sleeve friction and cone tip resistance), saturated hydraulic conductivity, field capacity, permanent wilting point, and porosity. The results showed some correlation between the cross-polarized (HV) radar backscatter coefficients and most of these properties. A few soil properties, like clay fraction, showed similar but weaker correlations with the co-polarized channels (HH and VV). The correlations between the soil properties and radar backscatter were analyzed separately for the river side and land side of the levee. It was found that the magnitude and direction of the correlation for most of the soil properties noticeably differed between the river and the land sides. The findings of this study can be a good starting point for scattering modelers in a pursuit of better models for radar scattering at cross polarizations which would include more diverse set of soil parameters.     

Modeling and mapping aboveground biomass of the restored mangroves using ALOS-2 PALSAR-2 in East Kalimantan,Indonesia

Accurate estimation of forest aboveground biomass (AGB) using remote sensing is a requisite for monitoring, reporting and verification (MRV) system of the United Nations Programme on Reducing Emissions from Deforestation and Forest Degradation. However, attaining high accuracy remains a great challenge in the diverse tropical forests. Among available technologies, l-band Synthetic Aperture Radar (SAR) estimates AGB with reasonably high accuracy in the terrestrial tropical forests. Nevertheless, the accuracy is relatively low in the mangrove forests. In this context, the study was carried out to model and map AGB using backscatter coefficients of Advanced Land Observing Satellite-2 (ALOS-2) Phased Array l-band SAR-2 (PALSAR-2) in part of the restored mangrove forest at Mahakam Delta, Indonesia. PALSAR-2 data was acquired with image scene observation during the peak low tide on 30 July 2018 from Japan Aerospace Exploration Agency. The forest parameters namely tree height and diameter at breast height were measured from 71 field plots in September-October 2018. The parameters were used in mangrove allometry to calculate the field AGB. Finally, HV polarized backscatter coefficients of PALSAR-2 were used to model AGB using linear regression. The model demonstrated a comparatively high performance using three distinct methods viz. independent validation (R² of 0.89 and RMSE of 23.16 tons ha⁻¹), random k-fold cross validation (R² of 0.89 and RMSE of 24.59 tons ha⁻¹) and leave location out cross validation (LLO CV) (R² of 0.88 and RMSE of 24.05 tons ha⁻¹). The high accuracy of the LLO CV indicates no spatial overfitting in the model. Thus, the model based on LLO CV was used to map AGB in the study area. This is the first study that successfully obtains high accuracy in modeling AGB in the mangrove forest. Therefore, it offers a significant contribution to the MRV mechanism for monitoring mangrove forests in the tropics and sub-tropics.     

中祁连东段花石山群与湟中群之间不整合关系讨论

中祁连地块东段花石山群与湟中群之间的接触关系,前人一般认为是平行不整合或整合关系。但我们对煌中县东岔沟剖面花石山群、但中群和惶源群的沉积、变形、变质特征研究表明：花石山群与下伏惶中群之间存在着沉积环境。构造变形、变质作用的间断或不连续性,接触部位上、下地层产状也不一致。因此认为花石山群与下伏惶中群可能为角度不整合关系。这一角度不整合的确定使得已经建立起来并为广泛接受的中祁连地块东段前寒武纪地展格架等问题需要重新审视和研究。     

Question of the pitch-roll buoy response to ocean waves as a simple harmonic oscillator?

The assumption that the East and North deck slopes of a pitch–roll buoy respond to East and North sea slopes as simple harmonic oscillators is routinely made by the National Data Buoy Center (NDBC) and others producing directional wave data. Although directional wave data derived with this assumption usually appear to be of good quality, the validity of the assumption has not previously been more directly demonstrated. In this paper, a method is proposed to judge the validity of the assumption for any set of time series records of buoy angular motion. The proposed method is applied to 200 record sets taken by an NDBC buoy located at ocean station 46024, and to five record sets taken by another NDBC buoy at 46051. For the 46024 data, it was demonstrated that the simple harmonic oscillator assumption was near perfectly valid. For the smaller 46051 data set, the simple harmonic oscillator assumption was shown to be slightly less valid.     

一种反演雷达波束内不均匀反射率场的方法

本文从原始雷达方程出发,提出了一种雷达加密观测方案和退卷积的数据反演方法,以实现雷达天线波束内的反射率不均匀结构信息的提取。反演方法的数值试验表明,此反演方法比常规测量方法在角分辨率方面提高约３倍,对波束内尺度为０．５８－２．０ＨＷ（ＨＷ是天线３ｄＢ波束宽度）的反射率变化有明显的反演能力。观测数据的测量误差对反演质量的影响也进行了计算和分析。本文还讨论了反演方法对雷达观测中的一些技术参数的要求。这些结果对于提高雷达尤其是星载微波主被动遥感器在测量降水量和云中含水量等参数中的精度有重要作用和现实意义。     

Using ADV backscatter strength for measuring suspended cohesive sediment concentration

Laboratory experiments were conducted at two institutes to reveal the relationship between acoustic backscatter strength and suspended sediment concentration (SSC). In total, three acoustic Doppler velocimeters (ADVs) with different frequencies (5, 10 and 16 MHz) were tested. Two different commercial clays and one natural sediment from Clay Bank site in the York River were checked for acoustic responses. The SSCs of selected sediments were artificially changed between a selected low and a high value in tap or de-ion water. Each ADV showed quite different backscatter responses depending on the sediment type and SSC. Not all devices had a good linear relationship between backscatter strength and SSC. Within a limited range of SSC, however, the backscatter strength can be well correlated with the SSC. Compared with optical backscattering sensor (OBS), the fluctuation of ADV backscatter signals was too noisy to be directly converted to the instantaneous changes of SSC due to high amplification ratio and small sampling volume. For the more accurate signal conversion for finding the fluctuation of SSC, the ensemble average should be applied to increase the signal-to-noise ratio. There are unexpected responses for the averaged backscatter wave strength: (1) high signals from small particles but low signals from large particles; and (2) two linear segments in calibration slope. These phenomena would be most likely caused by the different gain setting built in ADVs. The different acoustic responses to flocculation might also contribute somewhat if flocs are tightly packed. This study suggests that an ADV could be a useful instrument to estimate suspended cohesive sediment concentration and its fluctuation if the above concerns are clarified.     

Relationships between multibeam backscatter,sediment grain size and Posidonia oceanica seagrass distribution

The use of data, including bathymetry, backscatter intensity and the angular response of backscatter intensity, collected using multibeam sonar (MBS) systems to recognise seabed types was evaluated in the inner shelf of central western Sardinia (western Mediterranean sea), a site characterised by a complex seabed including sandy and gravelly sediments, Posidonia oceanica seagrass beds growing on hardgrounds (i.e. biogenic carbonates) and sedimentary substrates.