Is the Isentropic Surface Always Impermeable to the Potential Vorticity Substance?

The impermeability of isentropic surfaces by the potential vorticity substance (PVS) has often been used to help understand the generation of potential vorticity in the presence of diabatic heating and friction.In this study,we examined singularities of isentropic surfaces that may develop in the presence of diabatic heating and the fictitious movements of the isentropic surfaces that are involved in deriving the PVS impermeability theorem.Our results show that such singularities could occur in the upper troposphere as a result of intense convective-scale motion,at the cloud top due to radiative cooling,or within the well-mixed boundary layer.These locally ill-defined conditions allow PVS to penetrate across an isentropic surface.We conclude that the PVS impermeability theorem is generally valid for the stably stratified atmosphere in the absence of diabatic heating.     

凝结加热对对称不稳定影响的数值研究

将对流凝结加热引入到一准两维的非静力数值模式中，然后用该模式研究了凝结加热对对称不稳定的影响。试验结果表明：加入对流凝结加热后，可使基本状态是对称稳定的扰动得以发展，并产生向暖区移动的不稳定扰动。而加热振幅及加热廓线的垂直分布对不稳定扰动的发展、演变、移动及结构都有显著的影响。     

Anomalies of Thermomagnetic Characteristics of Lower Cretaceous Red-Beds in the Tadjik Depression (Southern Tien-Shan)

The paper features data on thermomagnetic characteristics of the red-bed sediments of the Lower Cretaceous of the Tadjik depression which turned out to be somewhat anomalous. The thermomagnetic characteristics of monolithic samples are stable under long-term heating (2–3 hours) at high temperature (600°–700°C). At the same time, the thermomagnetic characteristics of the powders, obtained from heated monolithic samples, display instability under even lesser temperatures. During heating at 600°–700°C, part of the hematite, dispersed in the rock, turns into stable maghemite. Disintegration of the monoliths changes the properties of the secondary maghemite - it becomes unstable to heating and at temperatures of 550°-600°C irreversibly changes into hematite.     

THE VITRINITE REFLECTANCE OF FAULT ROCKS FROM THE WENCHUAN EARTHQUAKE FAULT ZONE: CONSTRAINTS ON FRICTIONAL PROPERTIES OF THE FAULT DURING THE EARTHQUAKE

The temperature rise caused by frictional heating during seismic slip is able to indicate dynamic frictional properties of the seismic fault,which provides an approach to understand the dynamic process and energy budget of an earthquake.The residual indicators of frictional heating within the fault zone also can be taken as an evidence for seismic events.The vitrinite reflectance is a commonly-used geothermometer in the coal,oil and gas industries.It also has some potential applications in the studies of fault rock and fault mechanics.We studied vitrinite reflectance (VR) of fault rocks collected from surface outcrops of the Wenchuan earthquake fault zone in this paper.The measured data reveal that the VR of fault rocks are affected by fault motion,and there is a trend that the VR increases towards the fault core,which indicates the effects of frictional heating.The VR of fault rocks from the Bajiaomiao outcrop is much higher than those from the Shenxigou outcrop,which probably suggests the difference in fault activity at the two outcrops.Our study also suggests that systematic measurement of VR across the fault zone is helpful in identifying slip zones and determining their widths.From the VR measurement on an oriented specimen containing the slip surface of the Wenchuan earthquake from the Shenxigou outcrop,we observed anomalous high VR values in two black-colored slip zones of about 2mm in width near the slip surface.The numerical calculation shows that the maximum temperature rise on the fault plane near Shenxigou was probably less than 162℃ during the Wenchuan earthquake,which means the dynamic fault strength was quite low.These estimations are roughly in accord with the results from the high-velocity frictional experiments.     

Spatial structure of auroral day-time ionospheric electron density irregularities generated by a powerful HF-wave

We describe an experiment in satellite radio-wave probing of the ionosphere, modified by powerful waves from the HF heating facility at Tromsø (Norway) in May 1995. Amplitude scintillations and variations of the phase of VHF signals from Russian navigational satellites passing over the heated region were observed. We show that both large-scale electron density irregularities (several tens of kilometers in size) and small-scale ones (from hundreds of meters to kilometers) can be generated by the HF radiation. Maximum effects caused by small-scale irregularities detected in the satellite signals are observed in the directions sector approximately parallel to the geomagnetic field lines although large-scale structures can be detected within a much larger area. The properties of small-scale irregularities (electron density fluctuations) are investigated by applying a statistical analysis and by studying experimental and model mean values of the logarithm of the relative amplitude of the signal. The results indicate that satellite radio probing can be a supporting diagnostic technique for ionospheric heating and add valuable information to studies of effects produced by HF modification.     

Composition and pressure dependence of lattice thermal conductivity of (Mg,Fe)O solid solutions

We measured the lattice thermal conductivities of Fe_0.98O wüstite and iron-rich (Mg,Fe)O magnesiowüstite using the pulsed light heating thermoreflectance technique with a diamond anvil cell up to 61 GPa at 300 K. We found that the thermal conductivity of wüstite does not show a monotonic increase as a function of pressure, contrary to that of MgO periclase. Rocksalt (B1) to rhombohedral B1 transition is likely to induce an abnormal pressure response in the conductivity of wüstite. Our results also show that magnesiowüstite has a lower conductivity than that of MgO and FeO endmembers due to a strong iron impurity effect, which is well reproduced by a model considering phonon-impurity scattering in a binary solid solution.     

中国地区夏季平均加热率的时空分布特征

The latitude-altitude distributions of radiative fluxes and heating rates are investigated by utilizing CloudSat satellite data over China during summer. The Tibetan Plateau causes the downward shortwave fluxes of the lower atmosphere over central China to be smaller than the fluxes over southern and northern China by generating more clouds. The existence of a larger quantity of clouds over central China reflects a greater amount of solar radiation back into space. The vertical gradients of upward shortwave radiative fluxes in the atmosphere below 8 km are greater than those above 8 km. The latitudinal-altitude distributions of downward longwave radiative fluxes show a slantwise decreasing trend from low latitudes to high latitudes that gradually weaken in the downward direction. The upward longwave radiative fluxes also weaken in the upward direction but with larger gradients. The maximum heating rates by solar radiation and cooling rates by longwave infrared radiation are located over 28-40°N at 7-8 km mean sea level (MSL), and they are larger than the rates in the northern and southern regions. The heating and cooling rates match well both vertically and geographically.     

Model test of stratum failure and pore pressure variation induced by THF hydrate dissociation

ABSTRACT

A model test program for studying soil stratum failure and pore pressure variation during tetrahydrofuran (THF) hydrate dissociation considering the effects of heating and drainage conditions is presented in this paper. The temperature and pore pressures are recorded during heating. Test results show that the THF hydrate would dissociate to be liquid and then gas when heating. Once pore pressure generated by the flow of released gas/water exceeded the strength of over layer, the layered fractures and soil-gas/water mixture outburst would occur. The high heating temperature and low permeability of over layer both cause excess pore pressure generation and more serious stratum failures.     

登陆台风不连续北跳与暴雨的数值模拟研究

利用MM4（PSU/NCAR）模式，对1992年8月31日20时～9月1日20时登陆台风暴雨过程进行了数值试验研究。结果表明；登陆台风的不连续北跳与西风槽和积云对流潜热反馈有关。倒槽南部雨区内积云对流的发展加大了对台风倒槽内的水汽、动量、热量等输送，使倒槽内降水增幅。积云对流潜热反馈对高低空急流以及台风的移动都有很大的影响。     

黄河三角洲城市建设规划中气候资源的利用

在对黄河三角洲1961～2000年40年气候资源调查分析的基础上，以其中心城市东营为例，进一步分析了风向在城市布局规划中的指导作用，用统计方法估算了不同频率和高程的风载荷，对日照间距系数、采暖通风和空调室外气象参数等进行计算，为城市建设部门充分应用风、光、热等气候资源条件，趋利避害，进行合理规划设计，提供科学依据。