建筑群对城市冠层动力、热力效应的数值试验研究

利用中尺度模式MM5,分别耦合传统的边界层参数化方案和城市冠层参数化方案,模拟了2001年冬季北京冠层大气的动力、热力特征,并和观测资料进行了对比分析.分析结果表明,城市冠层参数化方案更能细致描述建筑群对城市冠层大气的动力、热力作用.由于建筑群的动力、热力作用,使北京城区的温度升高,风速减小,湍流动能增强,形成了明显的增温区、阻风区和湍能增强区,中心均位于城区高大建筑群附近,并向郊区递减.     

Characterization of volcanic thermal anomalies by means of sub-pixel temperature distribution analysis

The simultaneous solution of the Planck equation (involving the widely used “dual-band” technique) using two shortwave infrared (SWIR) bands allows for an estimate of the fractional area of the hottest part of an active lava flow (f _h) and the background temperature of the cooler crust (T _c). The use of a high spectral and spatial resolution imaging spectrometer with a wide dynamic range of 15 bits (DAIS 7915) in the wavelength range from 0.501 to 12.67 μm resulted in the identification of crustal temperature and fractional areas for an intra-crater hot spot at Mount Etna, Italy. This study indicates the existence of a relationship between these T _c and f _h extracted from DAIS and Landsat TM data. When the dual band equation system is performed on a lava flow, a logarithmic distribution is obtained from a plot of the fractional area of the hottest temperature vs. the temperature of the cooler crust. An entirely different distribution is obtained over active degassing vents, where increases in T _c occur without any increase in f _h. This result indicates that we can use scatter plots of T _c vs. fh to discriminate between different types of volcanic activity, in this case between degassing vents and lava flows, using satellite thermal data.     

Perspectives on present-day sea level change: a tribute to Christian le Provost

In this paper, we first discuss the controversial result of the work by Cabanes et al. (Science 294:840–842, 2001), who suggested that the rate of past century sea level rise may have been overestimated, considering the limited and heterogeneous location of historical tide gauges and the high regional variability of thermal expansion which was supposed to dominate the observed sea level. If correct, this conclusion would have solved the problem raised by the IPCC third assessment report [Church et al, Cambridge University Press, Cambridge, pp 881, 2001], namely, the factor two difference between the 20th century observed sea level rise and the computed climatic contributions. However, recent investigations based on new ocean temperature data sets indicate that thermal expansion only explains part (about 0.4 mm/year) of the 1.8 mm/year observed sea level rise of the past few decades. In fact, the Cabanes et al.’s conclusion was incorrect due to a contamination of abnormally high ocean temperature data in the Gulf Stream area that led to an overestimate of thermal expansion in this region. In this paper, we also estimate thermal expansion over the last decade (1993–2003), using a new ocean temperature and salinity database. We compare our result with three other estimates, two being based on global gridded data sets, and one based on an approach similar to that developed here. It is found that the mean rate of thermosteric sea level rise over the past decade is 1.5±0.3 mm/year, i.e. 50% of the observed 3 mm/year by satellite altimetry. For both time spans, past few decades and last decade, a contribution of 1.4 mm/year is not explained by thermal expansion, thus needs to be of water mass origin. Direct estimates of land ice melt for the recent years account for about 1 mm/year sea level rise. Thus, at least for the last decade, we have moved closer to explaining the observed rate of sea level rise than the IPCC third assessment report.     

Synergy of multiple geophysical approaches to unravel explosive eruption conduit and source dynamics - A case study from Stromboli

An effective approach to understanding the dynamics of explosive volcanic eruptions and the conduit systems that drive them is through synergy of multiple data sets. Three data sets that lend themselves to ease of integration are seismic, infrasonic and thermal. Although approaches involving these data have been used to record volcanological phenomena since 1862, 1955 and 1965, respectively, their integrated use has only developed since 1999. When combined, these three data sets allow constraint of shallow system geometry and the dynamics of the explosive events that occur within that system. Using Stromboli volcano (Italy) as a case study, we review the complete range of geochemical and geophysical studies that can be applied. In doing so, we aim to show how integration of these diverse studies allows insights into a plumbing system and the dynamics of the eruptive activity that the system feeds. When combined at Stromboli, these data provide constraint of multiple system parameters including chamber depths, gas and magma fluxes, shallow system magma residence times, explosion source depths, and the rise/ejection velocities of ascending gas slugs and ejecta. In turn, these results allow various conduit and eruption dynamic models to be applied and tested.The persistent and repeated mildly explosive events that characterize Stromboli have been modeled in terms of the coalescence of gas within the magma to form large gas slugs that ascend the remaining portion of the conduit to burst at the free surface. Our integrated seismic, infrasonic and thermal data sets indicate that gas coalescence occurs at a depth of ∼260 m, with a typical event frequency of ∼9/h. Infrasonic and thermal data show the explosion source to be located 20-220 m below the vent. Thermal data give emission velocities for the ejected fragments of 8-20 m/s, which converts to gas jet velocities of 23-39 m/s. Tracking these parameters in space and time shows that, although eruptions at Stromboli can be grouped into two characteristic types (simple and complex-each of which characterizes a particular crater, NE and SW, respectively), events within each type show significant short-term variability. The system does, however, appear robust, maintaining its characteristic strombolian eruption style after significant effusive phases and more energetic explosive events.     

塔里木北缘前寒武基底隆升剥露史：来自磷灰石裂变径迹的证据

库鲁克塔格隆起位于塔里木盆地北缘,广泛出露前寒武基底岩石。辛格尔村附近出露的太古宙杂岩,包括灰色片麻岩、角闪岩、片岩、混合岩和大理岩。新元古代地层出露在库鲁克塔格隆起西部的兴地、西山口、辛格尔和杀马山附近,不整合在古元古代和中元古代的片麻岩、角闪岩和片岩之上,并被早古生代的地层不整合。因此,该地区是了解塔里木盆地前寒武基底热演化史的理想地区。本研究的目的是为了探索:①塔里木基底岩石最初于何时剥露于地表?②塔里木基底剥露以后是否经历过再次埋藏和剥露?③塔里木基底岩石构造热演化过程对大陆边缘不同构造事件的响应。为了获取塔里木北缘剥露史和冷却过程信息,我们开展了裂变经迹的研究。含磷灰石的样品采自库鲁克塔格隆起的兴地断裂两侧。样品池年龄介于146.0±13.4和67.6±6.7Ma 之间,平均经迹长度介于.11.79±0.14和13.89±0.27μm之间。根据样品年龄和样品所处的构造位置,样品可以分为3组。A 组样品包括 F2、F3、F4、F5和 F8,裂变经迹表观年龄约100～110Ma,通常位于未遭断层变形的地区。B 组样品包括 F7、F9和 F10,裂变经迹表观年龄小于80Ma,构造上位于断层上盘并靠近断层。C 组样品 F11具有最大的裂变经迹表观年龄146.0±13.4Ma。热模拟表明,库鲁克塔格地区的隆升剥露作用可以划分为四期,分别是早侏罗世晚期(180Ma)、晚侏罗世—早白垩世(144～118Ma)、晚白垩世早期(94～82Ma)和新生代晚期(约10Ma)。裂变经迹记录的库鲁克塔格多阶段隆升作用,是对亚洲南缘多期地体碰撞增生的响应。     

Analysis of rock drainage and cooling experiments for underground cryogenic LNG storage

Hydrogeological monitoring was conducted around a pilot cavern for underground cryogenic LNG (Liquefied Natural Gas) storage. The monitoring was mainly focused on the operation of a drainage and recharge system. After the operation of the drainage system commenced, the drainage rate decreased rapidly in the initial stages and then decreased gradually. Hydrogeological monitoring revealed that the rock drainage system operated effectively. During drainage, the water table was maintained below the cavern roof. The recharge for ice-ring formation was performed in two phases. The first phase involved the cessation of pumping in downward-drainage holes and the second involved the closure of upward boreholes. Since the water table was maintained below the cavern roof, artificial recharge was planned at first. However, it was not implemented due to heavy rainfall in the recharge stage. On the basis of hydrogeological monitoring and hydraulic tests, it was found that the fractures above the roof and on the right wall of the pilot cavern mainly affected seepage into the cavern and thermal variation due to the storage of liquid nitrogen. Thermal variation was examined by the thermometers installed around the pilot cavern. The cooling and thawing processes reveal the characteristics of thermal distribution in the rock and the 0 °C isotherm. The cooling phase lasted for six months, and the 0 °C isotherm progressed in time after the injection of liquid nitrogen into the cavern. The isotherm propagated up to about 4 m from the floor and the sidewall of the cavern and about 3 m from the cavern roof. The cooling rate of the rock mass above the cavern roof was lower than that of the other cavern sides due to the gaseous space in the upper part of the containment. The fractures were analyzed and considered for thermal modeling. A two-dimensional finite element analysis was performed to compare the field monitoring at the pilot cavern. The numerical modeling shows the distance between the ice ring and heat transfer pattern of the fractures around the pilot cavern. The propagation of the measured and calculated 0 °C isotherm reveals that the water-conveying joint on the right wall might affect thermal propagation through a thermal pipe.     

2005年10月8日巴基斯坦7.8级地震热红外异常

收集了2005年巴基斯坦7.8级地震区Noaa17/AVHRR的2004-2005年的热红外遥感资料,并进行地表温度反演,得到了以震中为中心7°×7°范围的地表温度值。经热红外图像解译与构造关系对比分析,表明热红外解译图像与构造分布具有一致性。震源区地表温度时间序列显示:震前大约3个月内震源区存在明显的热红外异常。     

Crustal attenuation in the Southern Andean retroarc (38°–39°30′ S) determined from tectonic and gravimetric studies: The Lonco-Luán asthenospheric anomaly

The western retroarc of the Southern Andes between 38° and 40° S is formed by a NNW-elongated ridge not associated with stacked thrust sheets. On the contrary, during the last 4–3 Ma this ridge was affected by extensional deformation, regional uplift and related folding on a very broad scale. Receiver function analysis shows that the drainage divide area and adjacent retroarc lie over an attenuated crust. Expected crustal thickness at these latitudes is around 38 km, whereas in this part of the retroarc the thickness is less than 32 km. The causes for such attenuation have been linked to a moderate steepening of the subducted Nazca plate beneath the South American plate, which is suggested by a westward shift and narrowing of the magmatic arc during the last 4 to 5 Ma. Gravimetric studies show that the upper plate did not react homogeneously to slab steepening, but ancient sutures and lithospheric discontinuities deeply buried under Mesozoic to Cenozoic sequences in the retroarc were locally reactivated. These processes resulted in an asthenospheric anomaly that correlates at the surface with the area of Pliocene to Quaternary doming, widespread extension and three radial troughs. Two of the troughs have accommodated substantial amounts of extension, but the third was probably aborted at an early stage. Moreover, the presence of an anomalous concentration of calderas and large volcanic centers over the proposed asthenospheric anomaly, and their age distribution, may indicate minor migration of the asthenospheric anomaly between 4 and 2 Ma through the western South American plate.     

Specific variations of air temperature and relative humidity around the time of Michoacan earthquake M8.1 Sept. 19, 1985 as a possible indicator of interaction between tectonic plates

The recent development of the Lithosphere–Atmosphere–Ionosphere (LAI) coupling model and experimental data of remote sensing satellites on thermal anomalies before major strong earthquakes have demonstrated that radon emanations in the area of earthquake preparation can produce variations of the air temperature and relative humidity. Specific repeating pattern of humidity and air temperature variations was revealed as a result of analysis of the meteorological data for several tens of strong earthquakes all over the world. The main physical process responsible for the observed variations is the latent heat release due to water vapor condensation on ions produced as a result of air ionization by energetic α-particles emitted by ²²²Rn. The high effectiveness of this process was proved by the laboratory and field experiments; hence the specific variations of air humidity and temperature can be used as indicator of radon variations before earthquakes.We analyzed the historical meteorological data all over the Mexico around the time of one of the most destructive earthquakes (Michoacan earthquake M8.1) that affected the Mexico City on September 19, 1985. Several distinct zones of specific variations of the air temperature and relative humidity were revealed that may indicate the different character of radon variations in different parts of Mexico before the Michoacan earthquake. The most interesting result on the specific variations of atmosphere parameters was obtained at Baja California region close to the border of Cocos and Rivera tectonic plates. This result demonstrates the possibility of the increased radon variations not only in the vicinity of the earthquake source but also at the border of interacting tectonic plates. Recent results on Thermal InfraRed (TIR) anomalies registered by Meteosat 5 before the Gujarat earthquake M7.9 on 26 of January 2001 supports the idea on the possibility of thermal effects at the border of interacting tectonic plates.     

Testing satellite and ground thermal imaging of low-temperature fumarolic fields: The dormant Nisyros Volcano (Greece)

The Nisyros Volcano (Greece) was monitored by satellite and ground thermal imaging during the period 2000–2002. Three night-scheduled Landsat-7 ETM⁺ thermal (band 6) images of Nisyros Island were processed to obtain land surface temperature. Ground temperature data were also collected during one of the satellite overpasses. Processed results involving orthorectification and 3-D atmospheric correction clearly show the existence of a thermal anomaly inside the Nisyros Caldera. This anomaly is associated mainly with the largest hydrothermal craters and has land surface temperatures 5–10 °C warmer than its surroundings. The ground temperature generally increased by about 4 °C inside the main crater over the period 2000–2002. Ground thermal images of the hydrothermal Stephanos Crater were also collected in 2002 using a portable thermal infrared camera. These images were calibrated to ground temperature data and orthorectified. A difference of about 0–2 °C was observed between the ground thermal images and the ground temperature data. The overall study demonstrates that satellite remote sensing of low-temperature fumarolic fields within calderas can provide a reliable long-term monitoring tool of dormant volcanoes that have the potential to reactivate. Similarly, a portable thermo-imager can easily be deployed for real-time monitoring using telemetric data transfer. The operational costs for both systems are relatively low for an early warning system.