半参数回归与模型精化

就一般情况给出了半参数平差的算法,并结合一种特定的情况,讨论了正规化矩阵半正定时的计算方法,给出了相应的公式。最后构造了一个模拟的平差问题,对半参数法和最小二乘法的计算结果进行了比较。计算表明,半参数法能够发现并识别模型误差或观测值中的系统误差     

Sensitivity of soil parameters in unsaturated zone modelling and the relation between effective,laboratory and in situ estimates

Simulation of soil moisture content requires effective soil hydraulic parameters that are valid at the modelling scale. This study investigates how these parameters can be estimated by inverse modelling using soil moisture measurements at 25 locations at three different depths (at the surface, at 30 and 60 cm depth) on an 80 by 20 m hillslope. The study presents two global sensitivity analyses to investigate the sensitivity in simulated soil moisture content of the different hydraulic parameters used in a one‐dimensional unsaturated zone model based on Richards' equation. For estimation of the effective parameters the shuffled complex evolution algorithm is applied. These estimated parameters are compared to their measured laboratory and in situ equivalents. Soil hydraulic functions were estimated in the laboratory on 100 cm³ undisturbed soil cores collected at 115 locations situated in two horizons in three profile pits along the hillslope. Furthermore, in situ field saturated hydraulic conductivity was estimated at 120 locations using single‐ring pressure infiltrometer measurements. The sensitivity analysis of 13 soil physical parameters (saturated hydraulic conductivity (K_s), saturated moisture content (θ_s), residual moisture content (θ_r), inverse of the air‐entry value (α), van Genuchten shape parameter (n), Averjanov shape parameter (N) for both horizons, and depth (d) from surface to B horizon) in a two‐layer single column model showed that the parameter N is the least sensitive parameter. K_s of both horizons, θ_s of the A horizon and d were found to be the most sensitive parameters. Distributions over all locations of the effective parameters and the distributions of the estimated soil physical parameters from the undisturbed soil samples and the single‐ring pressure infiltrometer estimates were found significantly different at a 5% level for all parameters except for α of the A horizon and K_s and θ_s of the B horizon. Different reasons are discussed to explain these large differences. Copyright © 2004 John Wiley & Sons, Ltd.     

海南岛4—9月短时强降水的天气型和环境参数特征

利用海南岛加密自动站逐小时降水资料、ERA5再分析资料,对海南岛短时强降水日环流配置进行了天气学分型,并进一步探讨了各天气型下海南岛短时强降水的时空分布、环流形势和关键环境参数特征。结果表明：(1)海南岛短时强降水有明显的日变化特征,呈单峰型,主要出现在15:00—19:00。(2)海南岛短时强降水的天气型主要有南海低压槽、华南沿海槽、西南低压槽和冷锋型。(3)南海低压槽、华南沿海槽、西南低压槽和冷锋型短时强降水分别占37%,31%,16%和16%。南海低压槽和华南沿海槽型主要出现在7、8和9月;西南低压槽型除9月外,其余各月份均可能出现;冷锋型绝大多数出现在4、5月。(4)南海低压槽和华南沿海槽型整层湿度条件都较好,不稳定能量较大,垂直风切变较弱。西南低压槽型不稳定能量较大,湿度条件一般,垂直风切变较弱。冷锋型存在明显的上干下湿特征,垂直风切变最大,0～6 km风速差75%分位大于10 m/s,不稳定能量最小。     

考虑裂尖塑性区影响的水力压裂缝高计算模型

储层可压性的准确评价是储层压裂设计和压后产能评估的重要前提。目前,采用岩石力学参数进行页岩可压裂性评价取得了较好的现场应用效果。因此,如何准确获取岩石力学参数成为至关重要的问题。通过建立一种基于物理信息约束的神经网络模型,该模型采用物理和数据双驱动,仅使用少量数据就能够实现岩石力学参数的准确预测。为验证模型性能的优异性,采用人工神经网络、随机森林和XGBoost模型与之进行对比。结果表明,物理信息约束的神经网络在少量数据下预测岩石力学参数的平均准确率高于95%,性能远优于其他模型。采用物理信息约束的神经网络预测得到弹性模量、泊松比、抗拉强度和断裂韧性4种岩石力学参数,基于岩石力学参数对储层可压性的影响,建立了基于脆性指数和力学参数的可压性评价方法。最后,以渤海湾盆地沧东凹陷K2段不同储层可压性为例进行验证。结果表明：研究区整体可压性较好,其中,纹层状混合质页岩可压裂指数高于0.7,可压性良好;纹层状长英质页岩、厚层状灰云质页岩和薄层灰云质页岩可压裂指数均处在0.4~0.7,可压性中等。评价结果与实际施工现场各储层日采油量进行对比,证实了可压性智能评价方法的可靠性,该方法可以推广至页岩储层可压性评价工作中。

     

南极洲纳尔逊冰帽的某些动力学特征*

纳尔逊冰帽是南设得兰群岛的一个小冰帽,受海洋性气候影响冰帽上降水丰富,冰温较高。冰帽表面运动速度完全由冰帽表面形态和冰帽底床形态所控制,其中E剖面更为复杂。冰帽驱动应力基本小于100kPa.由V/Z～Za曲线得到在V/7为0.6～3×10^-9范围内的流动参数:n约为1;B≈4.3×10¹⁰dynescm^-2sec.这表明在低应力区,冰体流动更接近牛顿流体。     

2006年6月10日浙江飑线FY-2C卫星云图特征

利用国际卫星云气候计划（International Satellite Cloud Climate Program,简称ISCCP）提供的1998—2007年共10 a的深对流路径跟踪资料,统计分析了影响江淮地区对流系统（Convection system,简称CS）的时空分布及其参数特征。结果表明：影响江淮地区的CS主要集中在春夏两季,大多生成于江淮本地及我国中西部地区,呈现以江淮地区为中心的带状分布特征,越靠近江淮区域CS分布越为密集。依据源地不同,将影响江淮地区的CS分为5类,受气候条件与地形地貌的共同作用,各源地CS参数特征差异显著,总体来说CS的水平尺度越大,其生命史、对流云团(Convective clusters,简称CC)数目及水平云温度梯度也越大。其中江淮中心区域（MID）区域CS水平尺度、生命史和CC数目的平均值均为最小;东南（SE）区域CS生命周期以中长周期为主,水平尺度、最大对流比和云温度梯度的平均值最大。梅雨期内江淮地区对流活动频繁,CS的水平尺度大、生命史长、CC数目多。

     

基于遥感监测的城市热岛研究进展

全球正经历快速、高强度的城市化,导致城市热岛加剧,并对城市、区域乃至全球许多的生态环境要素直接或间接地产生多方面的影响,与人类福祉密切相关。遥感具有宽覆盖、信息量大、重复观测周期短等优点,已成为地表城市热岛(Surface Urban Heat Island, SUHI)监测广泛采用的一种方法。针对前人相关研究对热红外数据源、监测指标及SUHI时空变化规律尚缺乏系统总结且内容需要更新等问题,本文首先分类评述了SUHI遥感监测所采用的热红外遥感数据源。其次将现有的SUHI监测指标分为土地覆盖类型驱动型、地表温度格局驱动型及两者复合驱动型3类来述评,详细介绍了它们的计算方法、应用案例及优缺点;并从日间变化、夜间变化及昼夜对比的变化3个方面述评了SUHI的年内时空变化规律;归纳了其年际变化规律。最后,依据现有研究结论中相互冲突或尚需深化的地方,指出几个潜在的关键问题或研究方向。     

金华市水资源承载力分析

从生态学角度出发,提出水资源承载力是在社会发展的某一阶段和生态系统良性循环的条件下,水资源对人类活动的最大支撑能力。指出目前金华市的水荒不是水源型缺水,而是水质型缺水和工程型缺水。根据20多年的历史数据和2020年全面建设小康社会的标准,利用系统动力学(SD)模型,仿真研究了金华市未来政策实施后水资源承载力的动态变化过程。同时指出,对于金华市来说,单方面追求经济的快速发展、以牺牲环境作为代价的高方案和把环境保护作为首要目标、经济慢速发展的低方案都是不可取的,只有经济发展和环境保护同时兼顾的中方案才是首选方案。     

Wave runup on a concentric twin perforated circular cylinder

The regular wave interaction with a twin concentric porous circular cylinder system consisting of an inner impermeable cylinder and an outer perforated cylinder was studied through physical model and numerical model studies. The experiments were carried out on the twin concentric cylinder model in a wave flume to study the wave runup and rundown at the leading and trailing edges of the perforated cylinder. It was found that the maximum wave runup on the perforated cylinder is almost same as the incident wave height. The experimental results were used to develop the predictive formulae for the wave runup and rundown on the perforated cylinder, which can be easily used for design applications. The wave runup profiles around the perforated cylinder for different values of ka and porosities were studied numerically using Green's Identity Method. The results of the numerical study are presented and compared with the experimental measurements.     

Development and application of an operational tide and storm surge prediction model for the seas around Taiwan

Storm surges are abnormal rises in sea level along coastal areas and are mainly formed by strong wind and atmospheric depressions.When storm surges coincide with high tide,coastal flooding can occur.Creating storm surge prediction systems has been an important and operational task worldwide.This study developed a coupled tide and storm surge numerical model of the seas around Taiwan for operational purposes at the Central Weather Bureau.The model was calibrated and verified by using tidal records from seas around Taiwan.Model skill was assessed based on measured records,and the results are presented in details.At 3-minute resolution,tides were generally well predicted,with the root mean-square errors of less than 0.11 m and an overall correlation of more than 0.9.Storms(winds and depressions) were introduced into the model forcing by using the parameter typhoon model.Five typical typhoons that threatened Taiwan were simulated for assessment.The surges were well predicted compared with the records.