风速切变线上重力惯性波的不稳定发展

本文采用P坐标系中的线性化方程组,讨论了切变线对重力惯性波和重力波不稳定发展条件的影响。     

大地水准面起伏对重力归算的影响研究

针对目前重力探测中重力改正时常用的两个高程参考系统存在偏差这一事实,选取两个大地水准面起伏变化较大的剖面区域,分析大地水准面起伏对重力归算的影响。结果表明,剖面跨度和剖面大地水准面起伏梯度都会对布格重力异常产生影响,所以当重力探测区域大地水准面起伏差距较大时,大地水准面与参考椭球面之间的差异对重力归算的影响比较突出,在利用布格重力异常反演、解释地壳密度结构时,大地水准面起伏的影响必须考虑。     

“6.1”芦山地震作用下宝兴新华村滑坡动力响应与失稳过程离散元模拟

斜坡浅表层是各类地震地质灾害发育的潜在破坏位置,坡面形态和坡体结构往往造成斜坡动力响应及破坏的复杂化。为探究不稳定斜坡浅表潜在滑动层动力响应特征与失稳过程,以芦山M_s6.1级地震触发的新华村滑坡为例,基于现场调查采用离散元方法建立了二维计算模型,分析了该斜坡潜在滑动层及坡面形态的动力响应特征并对其失稳过程进行了模拟。结果表明：(1)斜坡浅表潜在滑动层具有强烈动力放大效应;(2)微地貌对于潜在不稳定斜坡坡面的放大效应具有明显的影响,浅表潜在滑动层水平向及竖直向加速度在凸出部位的放大效应显著,凹陷部位相较于凸出部位放大效应较低;(3)研究揭示新华村滑坡在微地貌的作用下凸起地形呈现先于凹陷地形遭受破坏,其失稳过程分为震动放大局部震裂-凸出地形破坏-凹陷地形破坏-完全破坏整体下滑-重力堆积5个阶段。该研究结果有助于提升防灾人员对地震诱发潜在不稳定斜坡失稳的认识,为防灾减灾提供理论和数据支撑。     

地形作用下有限振幅Rossby波的稳定性分析

本文用微分方程定性理论方法分析了地形对有限振幅Rossby波的稳定性影响。结果表明:地形北坡有利于波动出现不稳定,南坡使波动稳定;西坡使导式波动不稳定但使曳式波动稳定,东坡使导式波动稳定但使曳式波动不稳定。     

Lagrange变分和大气中惯性重力内波的稳定性

本文利用Lagrange变分导出了惯性重力内波的波作用量方程,这种方程与用KWB方法所得到的惯性重力内波的波作用量方程在形式上有所不同,但所得到的结果却与观测事实是一致的。     

GT-2A航空重力仪精度评定

选择地形平坦的实验区A和地形起伏较大的实验区B,采用GT-2A航空重力测量数据和高精度地面重力测量数据,依据测线网交叉点平差方法评定GT-2A航空重力仪的内符合精度,通过地面重力与航空重力延拓结果的比对实验评定其外符合精度。结果表明,GT-2A重力扰动测量结果的内符合精度优于1 mGal,外符合精度在实验区A优于2 mGal,在实验区B优于3 mGal。     

融合多源数据的局部重力场建模中线性化误差的研究

引入高阶重力场模型作为参考场,削弱局部重力场逼近中线性化误差的影响。以实测的陆地重力异常、船载重力异常及航空重力扰动为基础数据,基于泊松小波径向基函数分析不同参考场对局部重力场逼近的影响。结果表明,引入高阶全球重力场模型代替GRS80参考椭球正常场作为参考场,能更为准确地逼近真实的重力场,有效削弱线性化误差的影响。相比于基于GRS80正常场构建的似大地水准面模型,基于DGM1S重力场模型为参考场构建的似大地水准面的精度,在地形起伏较大的德国、英国及挪威区域分别提高了1.5 mm、3.3 mm和9.0 mm。     

ASTER GDEM垂直精度评价及其在重力地形改正中的适用性

利用重力剖面的GPS数据对ASTER GDEM模型进行垂直精度评估,并对其在重力地形改正中的适用性进行讨论。结果表明,ASTER GDEM模型在贵阳-维西和金川-犍为两个重力剖面中,与实测GPS高程相比标准差分别为14.93 m和18.02 m,模型起伏与实测数据具有较好的一致性。在小比例尺中、远区及大比例尺远区重力地形改正中,ASTER GDEM模型数据的适用性较好。     

利用重力多尺度分解资料反演青藏高原东北缘地壳厚度

通过重力异常分解模型,选用小波基函数“bior3.7”,分解得出青藏高原东北缘布格重力异常资料的小波4阶近似成分,利用其主要由莫霍面产生的布格重力异常,以6条人工地震剖面信息做初始控制条件,反演得出青藏高原东北缘的地壳厚度。     

陆地惯性重力测量静态试验研究

利用高精度捷联式惯性测量设备开展测定重力场的初步静态试验,并对静态惯性重力测量影响因素作初步探讨。静态测试表明,基于试验采用IMU内置的石英挠性加速度计,在稳定的观测环境下通过30 s的滑动平均滤波可以消除高频噪声,得到标准差约为1.5 mGal的重力观测值,但仪器自身的不稳定性和环境变化引起的漂移会使重力观测值呈线性增大的趋势。针对该变化,通过回归分析进行拟合,并结合初始重力已知点上观测得到的初始偏移量,在车载试验中对零速修正点上的静态重力测量误差进行补偿,使大多数点上的重力观测精度由12~20 mGal提升至优于2 mGal。     

陕西省城固县桔园乡山地坡面观测及低空探测气象资料的分析

本文通过陕西省城囿县山地实际考察资料的分析,旨在找出冬季山地逆温及暖带的分布规律,并为提高坡地柑桔种植上限高度提供依据,研究指出:当地逆温暖带高度为650—750米,坡地柑桔种植上限高度可达800米左右。     

NONLINEAR INERTIA—GRAVITY INTERNAL WAVE IN STRATIFIED FLUID

Based on the fundamental equations of geophysical fluid dynamics and on the consequence of verticaldensity stratification,travelling wave coordinates are used in this work to study the geometric topologicalstructures of nonlinear permanent wave in phase plane.Rigorous mathematical mechanics demonstratethat the solution of permanent solitary wave does not exist.Hamilton functions and "action-angle" varia-bles are used to express the travelling wave system in the simplest form and the analytic solution of the nonlinear inertia-gravity internal wave is obtained.     

西藏高原切变线云系中雨以上降水的卫星云图分析

本文利用1974～1980年7年6～9月份152次中雨以上降水的卫星云图资料,着重分析了91次西藏高原切变线云系中雨以上降水过程的卫星云图形态和造成中雨以上降水的高原南部和北部云系侵入高原的路径,从而觅求出造成西藏高原中雨以上降水的切变线云系的卫星云图,以便于高原天气分析和预报中使用。     

The Structure and Formation Mechanism of a Sea Fog Event over the Yellow Sea

In this paper, a heavy sea fog event occurring over the Yellow Sea on 11 April 2004 was investigated based upon observational and modeling analyses. From the observational analyses, this sea fog event is a typical advection cooling case. Sea surface temperature(SST) and specific humidity(SH) show strong gradients from south to north, in which warm water is located in the south and consequently, moisture is larger in the south than in the north due to evaporation processes. After fog formation, evaporation process provides more moisture into the air and further contributes to fog evolution. The sea fog event was reproduced by the Regional Atmospheric Modeling System(RAMS) reasonably. The roles of important physical processes such as radiation, turbulence as well as atmospheric stratification in sea fog’s structure and its formation mechanisms were analyzed using the model results. The roles of long wave radiation cooling, turbulence as well as atmospheric stratification were analyzed based on the modeling results. It is found that the long wave radiative cooling at the fog top plays an important role in cooling down the fog layer through turbulence mixing. The fog top cooling can overpower warming from the surface. Sea fog develops upward with the aid of turbulence. The buoyancy term, i.e., the unstable layer, contributes to the generation of TKE in the fog region. However, the temperature inversion layer prevents fog from growing upward.     

Variation of Thornthwaite moisture index in Hengduan Mountains,China

The Thornthwaite moisture index, an index of the supply of water(precipitation) in an area relative to the climatic demand for water(potential evapotranspiration), was used to examine the spatial and temporal variation of drought and to verify the influence of environmental factors on the drought in the Hengduan Mountains, China. Results indicate that the Thornthwaite moisture index in the Hengduan Mountains had been increasing since 1960 with a rate of 0.1938/yr. Annual Thornthwaite moisture index in Hengduan Mountains was between –97.47 and 67.43 and the spatial heterogeneity was obvious in different seasons. Thornthwaite moisture index was high in the north and low in the south, and the monsoon rainfall had a significant impact on its spatial distribution. The tendency rate of Thornthwaite moisture index variation varied in different seasons, and the increasing trends in spring were greater than that in summer and autumn. However, the Thornthwaite moisture index decreased in winter. Thornthwaite moisture index increased greatly in the north and there was a small growth in the south of Hengduan Mountains. The increase of precipitation and decrease of evaporation lead to the increase of Thornthwaite moisture index. Thornthwaite moisture index has strong correlation with vegetation coverage. It can be seen that the correlation between Normalized Difference Vegetation Index(NDVI) and Thornthwaite moisture index was positive in spring and summer, but negative in autumn and winter. Correlation between Thornthwaite moisture index and relative soil relative moisture content was positive in spring, summer and autumn, but negative in winter. The typical mountainous terrain affect the distribution of temperature, precipitation, wind speed and other meteorological factors in this region, and then affect the spatial distribution of Thornthwaite moisture index. The unique ridge-gorge terrain caused the continuity of water-heat distribution from the north to south, and the water-heat was stronger than that from the east to west part, and thus determined the spatial distribution of Thornthwaite moisture index. The drought in the Hengduan Mountains area is mainly due to the unstable South Asian monsoon rainfall time.     

Numerical simulation of wave field in the South China Sea using WAVEWATCH III

Wave fi elds of the South China Sea(SCS) from 1976 to 2005 were simulated using WAVEWATCH III by inputting high-resolution reanalysis wind fi eld datasets assimilated from several meteorological data sources. Comparisons of wave heights between WAVEWATCH III and TOPEX/Poseidon altimeter and buoy data show a good agreement. Our results show seasonal variation of wave direction as follows: 1. During the summer monsoon(April–September), waves from south occur from April through September in the southern SCS region, which prevail taking about 40% of the time; 2. During the winter monsoon(December–March), waves from northeast prevail throughout the SCS for 56% of the period; 3. The dominant wave direction in SCS is NE. The seasonal variation of wave height H s in SCS shows that in spring, H s ≥1 m in the central SCS region and is less than 1 m in other areas. In summer, H s is higher than in spring. During September–November, infl uenced by tropical cyclones, H s is mostly higher than 1 m. East of Hainan Island, H s 2 m. In winter, H s reaches its maximum value infl uenced by the north-east monsoon, and heights over 2 m are found over a large part of SCS. Finally, we calculated the extreme wave parameters in SCS and found that the extreme wind speed and wave height for the 100-year return period for SCS peaked at 45 m/s and 19 m, respectively, SE of Hainan Island and decreased from north to south.     

青藏高原500hpa暖性高压生成的热成风适应机制

本文利用热成风适应原理,采取分解分析法对青藏高原500hpa暖性高压的生成机制作了一些定性和定量的讨论。结果表明:在扰动的水平尺度大于热成风适应的特征尺度的条件下,当源地有明显的负值非热成风涡度出现时,流场将向温度场适应,而温度场由于高原的加热作用存在暖中心或暖脊,则适应的结果在高原大气500hpa形成暖性高压,并伴随高层辐合,低层辐散及下沉运动。     

利用地震层析成像研究地幔非对称结构

利用Su,Vasco,Hilst,Grand等提供的地震层析成像模型，根据实验室结果外推得到的地震波速度异常与密度异常之间的线性关系，将地幔进行分层，网络化处理，计算了地幔各层异常密度，密度异常质心和全地幔密度异常质位置。结果表明，地幔密度异常表现出的总体特征是：整体地幔密度异常为负值，上地幔异常大，中，下地幔密度异常较小；地幔整体和多数分层密度异常质心分布在北半球。这一结果反映，现今地幔热动力学演化呈现出南半球膨胀和北半球收缩的非对称基本格局。     

基于GridMet模型的浙江省温湿指数空间分布及地形影响分析

温湿指数是气候舒适度评价模型之一,通过温度与湿度的组合反映人体与周围环境的热量交换,本文利用2003-2018年浙江省及其周边71个气象站点月平均气温、地面水汽压数据,以及MODIS水汽产品,基于GridMet模型模拟了浙江省各月温湿指数空间分布（100 m×100 m）,分析了浙江省温湿指数随地形因子（海拔、坡度、坡向）变化的特征;讨论了各地形因子对温湿指数空间分布的影响程度。结果表明：① 海拔、坡度、坡向3个地形因子中,1月温湿指数随坡向的变化最大,7月最小;② 同坡向上,坡度变化对1月温湿指数影响较大,而海拔变化则是对7月影响最大;③ 南坡1月温湿指数随海拔和坡度增加均略为增加,南坡其他月份及北坡各月均为随海拔和坡度增加温湿指数减小;④ 北坡相对于南坡而言,海拔和坡度对温湿指数的影响更为明显。浙江大部分山区由于地形影响,夏季较为“舒适”,适宜建立避暑消夏的旅游项目。     

应用地球物理资料对胶南地体构造特征的探讨

本文根据新的地球物理资料和地体构造的研究成果,探讨了胶南地体构造的深部特征和依据。胶南地体处在华北地台与扬子地台之间构造缝合带上,它应为秦岭造山带越过郯庐断裂的向东延伸部分;五荣断裂为其北界,赣榆黄海断裂为南界。胶南地体可能是在秦岭造山过程中两大板块碰撞增生形成。胶南重力低不仅与地幔低凹有关,而且与该地体内广泛发育的密度较小的花岗岩类岩石及低密度值的元古界胶南群内混合岩、片麻岩、变粒岩等岩石密切相关。