一种初始方程中应用实测风进行风场初值化的方法

本文提出一种利用实测风场、高度场、温度场和地面三小时气压变化资料,考虑风场和质量场之间基本满足准地转平衡关系,大气具有准无辐散性,但又保留一部分与地面气压变化相应散度的地转偏差,将以实测的等压面风场插到σ坐标的风场进行订正的初值化方法,并用一个单时资料进行初步试验.文中还对风场初值化问题进行了讨论.     

声波探查砼裂缝深度的数学分析与实践

本文仅就声波探查砼裂缝深度的可行性从数学角度进行了分析与论证,并给出了工程实例。     

The role of wind direction in eolian transport on a narrow sandy beach

Comparison of eolian transport during five high-velocity wind events over a 29 day period on a narrow estuarine beach in Delaware Bay, New Jersey, USA, reveals the temporal variability of transport, due to changes in direction of wind approach. Mean wind speed measured 6 m above the dune crest for the five events ranged from 8·5 to 15·9 ms^?1. Mean wind direction was oblique to the shoreline (63° from shore-normal) during one event but was within 14° of shore-normal during the other events. Eolian transport is greatest during low tide and rising tide, when the beach source area is widest and when drying of surface sediments occurs. The quantity of sediment caught in a vertical trap for the five events varied from a total of 0·07 to 113·73 kgm^?1. Differences in temperature, relative humidity and moisture and salt content of surficial sediments were slight. Mean grain sizes ranged from 0·33 to 0·58 mm, causing slight differences in threshold shear velocity, but shear velocities exceeded the threshold required for transport during all events. Beach width, measured normal to the shoreline, varied from 15·5 to 18·0 m; beach slope differed by 0·5°. The oblique wind during one event created a source width nearly double the width during other days. Beach slope, measured in the direction of the wind, was less than half as steep as the slope measured normal to the shoreline. The amount of sand trapped during the oblique wind was over 20 times greater than any other event, even those with higher shear velocities. The ability of the beach surface to supply grains to the air stream is limited on narrow beaches, but increased source width, due to oblique wind approach, can partially overcome limitations of surface conditions on the beach.     

广义帕累托分布在广东重现期风速计算中的应用

利用广东省86个国家气象观测站建站以来近70a的逐月最大风速序列和近20a(1999—2018年)的逐月最大风速序列,基于POT抽样法,分别采用三参数广义帕累托分布函数对各站的重现期风速进行了概率计算,计算过程中三参数广义帕累托分布函数分别采用矩估计(MOM)、极大似然估计(MLE)、似然矩估计(LM)和概率权矩估计(PWM)等4种参数估计方法,结合表征参数估计优良性的指标:均方根误差RMSE、拟合相对偏差和显著性水平为0.05的科莫戈洛夫检验拟合适度指标K_f对拟合效果进行检验,结果表明:基于POT抽样的概率权矩估计(PWM)拟合效果最好。     

An Imaging Photon Counting Intensified CCD for High Speed Photometry

The scientific performance evaluation of a photon countingimaging system is presented. The detector is constituted by an ICCD camera with RbTe photocathode(optimized for UV radiation), and dedicated electronics for the acquisition and analysis ofthe events. For each photon event on the CCD, a real-time centroid calculation is performed, inorder to reach spatial resolution down to 25 m FWHM. The system has been tested usingthe 182 cm telescope of the Asiago Observatory.A standard stars field through U Johnson filter,and the Crab pulsar (PSR 0531+21) were observed. From the photometric data, relative magnitudes of the standard stars have been derived, showing a goodlinearity of the detector in the range of flux under consideration, as expected fromprevious laboratory measurements.The pulsar's data have been processed by FFT and epoch foldingtechniques to testthe detector's timing performances in the highest resolutionmode (4.512 ms).These observations show that a space resolved time analysis ofperiodic sources can be performed with 10^-7 s accuracy.     

Comments on: ‘The Neutral, Barotropic Planetary Boundary Layer, Capped by a Low-Level Inversion’ by G. D. Hess, Boundary-Layer Meteorology (2004) 110, pp. 319–355

Precision measurements indicate that the stability capping of the neutral planetary boundary layer (PBL) that leads to a reduced PBL height is caused by the very stable upper part of the PBL, rather than by an overlying inversion. Radiative processes related to liquid water in boundary-layer clouds seem to play the key role for the formation of the stable upper PBL. The famous Leipzig Profile – generally considered as an example of a neutral PBL – has been included in Hess’s analysis because its PBL height is considerably lower than the ca. 3000 m to be expected by numerical models in truly neutral conditions. An analysis of the original observations reveals that the Leipzig PBL was stable and that it can be consistently treated as a ‘normal’ stable PBL with a height of ca. 700 m. A further finding is that the super-geostrophic PBL wind speed maxima predicted by almost all models are not observed in near-steady-state conditions. For the ‘ranking’ of analytical models versus numerical models, the comparisons with measurements show that the analytical models perform comparably well and even partially better than the numerical models.     

珠穆朗玛峰北坡山谷太阳辐射和大气的特征与分析

2006年5月27日～6月30日HEST2006大气科学实验对珠峰北坡山谷的辐射(总辐射、净辐射)和温、湿度、风等进行了综合观测.沿珠峰北坡山谷布设了3个观测站,3个测站的辐射、温度、风都表现出明显的日变化规律,它们在08:00或09:00(地方时,下同)达到极大值.3个测站总辐射和净辐射的日变化都七匕较一致.从日变化最大值出现的时间来看,各站的辐射通量早于气温,气温早于风速.3个测站中任意2站之间辐射(总辐射、净辐射)最大值之比与温度和风速最大值之比均比较接近.因辐射状况、地形结构、大气温度等不同,远离珠峰区域的风一天之内多次改变风向,靠近珠峰区域则24h都为南风.珠峰北坡山谷不同区域风向风速变化存在明显时差,南风强于北风,且持续时间长.研究表明,辐射能量对于珠峰北坡大气运动具有重要的驱动作用,是控制和改变其大气运动方式最基本、最重要的因子.净辐射在不同区域风向转变或风速变化过程中起着决定性的作用.     

濮阳近50a风速变化特征及突变分析

利用线性分析方法,分析了濮阳近50 a平均风速、大风日数的变化特征,并利用滑动的t检验法分析了风速突变,结果显示:年平均风速以0.498(m/s)/10 a的倾向率减少,大风和扬沙日数分别以2.7 d/10 a和5.6 d/10 a的倾向率减少;平均风速,大风、扬沙日数在20世纪80年代初期发生突变。     

对建筑场地类别划分方法的探讨

判定场地类别是岩土工程勘察要解决的主要问题之一。科学地确定场地类别可以用来指导建筑抗震设计。判定场地类别的方法目前主要依据规范法进行。在按规范法进行判定场地类别时,由于场地沉积土层的差异、建筑物基础埋深的不同或采用基础型式的不同、场地标高的不同,有时会产生一些矛盾。对这些矛盾提出了初步解决的建议,供业内人士参考及批评指正。     

Pulsatory characteristics of wind velocity in sand flow over typical underlying surfaces

Pulsatory characteristics of wind velocity in sand flow over Gobi and mobile sand surface have been investigated experimentally in the wind tunnel. The primary goal of this paper is to reveal the relation- ship between pulsatory characteristics of instantaneous wind speed in sand flow and the motion state of sand grains. For a given underlying surface, pulsation of wind velocities in sand flow on different heights has a good correlation. As the space distance among different heights increases, fluctuation of instantaneous wind speed presents a decreasing trend and its amplitude is closely related to the mo- tion state of sand grains and their transport. Pulsatory intensity increases with the indicated wind speed, but its relative value does not depend on it, only agrees with height.