EnKF协方差膨胀算法对雷达资料同化的影响研究

基于集合卡尔曼滤波(EnKF)方法同化模拟雷达径向风和回波,引入具有时空自适应理论优势的贝叶斯膨胀算法,通过与常数膨胀算法的对比,分析了两种协方差膨胀算法对EnKF同化效果的影响。结果表明:在对流区域的北侧,由贝叶斯膨胀算法分析得到的回波在水平和垂直结构上均增强;在对流区域,由贝叶斯膨胀算法分析得到的各变量的集合离散度增大,均方根误差减小,水平和垂直速度增大,冷池强度减弱;模拟还发现贝叶斯膨胀算法提高了强对流系统的模拟效果,回波强度增强,阵风锋区内水平和垂直风速增大。这表明贝叶斯膨胀算法有效地改进了基于常数膨胀算法的EnKF同化雷达资料的效果。     

Sources of uncertainty in liquefaction triggering procedures

Uncertainties in observed data and in processing field and laboratory tests are major concerns. Assigning reasonable coefficients of variation to the parameters in the conventional analyses indicates that a site with deterministic factors of safety of 1.5 can actually have liquefaction triggering probability above 20%. About a third of the variance comes from uncertainty in the load, which is independent of the resistance. Researchers have traditionally presented the results of case studies in the form of charts showing instances in which liquefaction did and did not occur and have developed relations to separate the two. Although the original researchers developed the separations informally, recent work has applied statistical methods. These give the sampling distributions of the observed data rather than the probability of triggering given the data. Researchers have addressed this issue using Bayesian methods, adopting non-informative priors. Published curves of liquefaction probabilities can be interpreted as likelihood ratios. Other independent work demonstrates that geological, meteorological, and historical data can be used to develop prior probabilities, so it may not be necessary to assume a non-informative prior. The actual prior can then be combined with the likelihood ratios to provide rational probabilities of liquefaction. We recommend that researchers publish their likelihood ratios and allow engineers faced with particular sites to use those to update their own priors.     

基于现场观测资料的卫星海表盐度网格化产品误差分析与质量评估

自欧洲土壤湿度和盐度卫星SMOS和美国宝瓶座盐度卫星Aquarius相继发射之后,多个数据中心发布了两颗卫星的海表盐度网格化产品,其中包括法国海洋研究院SMOS卫星数据小组发布SMOS Locean L3盐度产品、西班牙巴塞罗那专家中心发布SMOS BEC L4盐度产品和美国宇航局喷气动力实验室发布AquariusV3.0 CAP L3盐度产品。本文利用精确盐度现场观测资料从产品精度和模拟海洋现象能力两个方面对以上3种产品质量进行了评估。研究表明:(1) 在精度方面,与盐度现场资料相比,Aquarius CAP 产品质量最高,产品盐度偏差和均方根误差全年稳定且偏差较小,部分海域达到了设计精度;SMOS两种卫星产品在全球海域偏差较不稳定,个别月份出现异常偏差值;SMOS产品在低纬和开阔海域的数据质量相对较高,但在高纬海域仍存在较大误差,需要进一步提升;(2) 在刻画海洋现象方面,Aquarius产品在热带太平洋较好刻画了淡池东缘盐度锋,SMOS BEC产品的刻画能力次之,SMOS Locean产品在热带太平洋充满了小尺度噪音,描述物理现象方面表现偏差。     

Particulate n-alkanes and fatty acids in the Changjiang river system

Particulate samples were collected from the Changjiang river system during a flood period, in May 1997, and POC, stable isotope and lipids associated with particles were examined. Results showed the decrease (0.84% ～ 1.88%) of organic carbon content from the upper reaches to the estuary.δ13C values of particulate organic carbon was in the range of -24.9×10-3 to -26.6×10-3, which were close to the isotopic signature of continental C3 vegetation. Total particulate n-alkanes concentrations varied from 1.4 to 10.1μg/dm3,or from 23.7 to 107μg/g of total suspended matter. Fatty acids were present in all the samples, from 1.4 to 5.4μg/dm3, with saturated and unsaturated straight-chain and branched compounds in the carbon number range from C12 to C30. Both δ13C and the ratio of carbon content to nitrogen content indicate the predominance of terrestrial inputs (soil organic matter) among the particles. The biomarker approach has been used to identify the relative portion of terrigenous and autochthonous fraction in the particulate samples. The distribution of fatty acids suggests a striking phytoplanktonic and microbial signal in most particle samples. The terrestrial alkanes are used to estimate the contribution of terrestrial inputs along the mainstream.     

Atmospheric remote sensing constraints on direct sea-air methane flux from the 22/4b North Sea massive blowout bubble plume

A new airborne remote sensing approach to estimate an upper limit of the direct sea-air methane emission flux was applied over the 22/4b blowout site located at N57.92°, E1.63° in the North Sea. Passive remote sensing data using sunglint/sunglitter geometry were collected during instrumental tests with the Methane Airborne MAPper – MAMAP – instrument installed aboard the Alfred Wegener Institute (AWI) Polar-5 aircraft on 3. June 2011. MAMAP is a passive short wave infrared (SWIR) remote sensing spectrometer for airborne measurements and retrieval of the atmospheric column-averaged dry air mole fractions of methane (XCH₄) and carbon dioxide (XCO₂). In addition to MAMAP a fast CH₄ in-situ analyzer (Los-Gatos Research Inc. RMT-200), two 5-hole turbulence probes and the Polar-5 basic sensor suite comprising different temperature, pressure, humidity and camera sensors were installed aboard the aircraft. The collected MAMAP remote sensing data acquired in the vicinity of the 22/4b blowout site showed no detectable increase in the derived XCH₄ (with respect to the atmospheric background). Based on the absence of a detectable XCH₄ column increase, an approximate top-down upper-limit for the direct atmospheric 22/4b blowout CH₄ emissions from the main bubble plume of less than 10 ktCH₄/yr has been derived. The constraint has been determined by comparing XCH₄ information derived by the remote sensing measurements with results obtained from a Gaussian plume forward model simulation taking into account the actual flight track, the instrument sensitivity and measurement geometry, as well as the prevailing atmospheric conditions.     

用天气雷达回波强度资料估测降水

利用2004年兴义多普勒雷达体扫复合仰角的强度回波资料及自动站雨量资料,在贵州省黔西南地区进行降水估测。综合考虑了地理环境、气候、距雷达中心距离等3个因素,对下属的8县1市进行降水估测,运用了不同仰角进行多次实验,最后运用最小二乘法得到该区域的Z-I(反射率因子-降水)关系,选取2005年1-7月的部分资料进行检验对比,并对降水误差从地理环境、雷达性能等多个方面进行分析。结果表明,用此方法得出的Z-I适用性较好,准确率较高,为降水估测提供了较可靠的判据。     

甘孜州九龙县水土流失评价研究

本文以九龙县为研究区,根据沟壑密度、坡度、植被盖度、土地利用类型和高程5个因子,结合ARC-GIS空间分析功能和MATLAB数学建模编程的功能,应用GA-BP模型(遗传算法优化BP神经网络)对研究区的水土流失进行非线性智能定量评价,并与层次分析法的结果对比分析,阐述了GA-BP模型的优越性。本次研究可以为九龙县水土流失预防和治理提供有益的参考。     

X波段双线偏振雷达不同衰减订正方法对比及其对降水估测影响研究

文中分析了X波段双线偏振雷达衰减订正各种方法的特点,考虑到差传播相移率(KDP)作为衰减订正的一种有效途径,以及由于KDP值较小,数据质量不稳定,往往导致订正误差较大,因此提出了同时利用水平反射率因子ZH与KDP进行衰减订正的ZH-KDP综合法.基于同样的考虑,在随后利用ZH、KDP进行降水估测时,提出了ZH-KDP-R综合估测方法.利用中国科学院寒区旱区环境与工程研究所和成都锦江电子系统工程有限公司,在研制3.2 cm波长同时收发式多普勒偏振天气雷达过程中,2005年8月在平凉外场试验取得的一批观测资料,对提出的衰减订正综合法及降水估测综合法的效果进行了分析检验,结果表明,ZH-KDP综合法对ZH、ZDR有稳定的订正效果,并且订正速度快,能够达到实时运行的要求.2005年8月11日15:08:03-22:05:46,间隔5-12 min不等,雷达开机取得了连续的观测资料,通过对这次降水过程的对比分析表明,ZH-KDP-R综合估测法比单因子KDP-R法、Z-R关系法,适用估测的降水强度变化范围广,与自动雨量记的观测结果较为吻合.Z-R关系法中,利用订正后的ZH值,比利用订正前的ZH值,降水估测值与雨量记实测值的误差明显减小,说明衰减订正后的雷达数据质量有明显的改善.     

滑坡灾害防治工程中施工组织设计对工程投资概算影响的研究

本文通过对具体地质灾害防治工程初步设计阶段的施工组织设计与工程投资概算之间关系分析, 指出施工组织对工程投资概算的影响不小于工程设计和地质勘查资料的影响, 施工组织设计对概算可靠度的提高有很重要的意义。