Hα Doppler brightening and Lyman-α Doppler dimming in moving Hα prominences

We consider the effect that coherent motion has on the observed brightness of moving clouds above the photosphere. We find that steady state clouds (constant N _e and T _e ) that are moving perpendicular to the line of sight will appear brighter in H for speeds between 8 and 100 km/sec and dimmer for speeds greater than 135 km/sec. The brightening and dimming are due to apparent Doppler shifts of the respective H absorption and the Lyman- emission profiles seen by the absorption profile of the moving cloud.We apply this analysis, along with optical depth and geometrical considerations, to the observed brightness variations of the 1 March 1969 limb eruptive prominence. We find that all of the observed brightening and dimming can be explained by the motions, and that no significant change in the prominence N _e or T _e was necessary during the observed H event. This conclusion is significant in interpreting an X-ray burst that began as the prominence velocity increased abruptly at the time of maximum H intensity. The thermal X-ray peak occurred 150 sec later when the prominence had become faint again. There was no associated flare that was visible in H. We discuss the relative brightness of H and D ₃ in a specific moving prominence knot.We note that the observed range of limb speeds (30–150 km/sec) may be due to the combined H Doppler brightening and Lyman- dimming effects. We also discuss generally the H brightness of disk surges (bright and dark) and flares, and sprays and puffs that occur at or near the limb.Now at the Dept. of Physics and Astrophysics, University of Colorado, and High Altitude Observatory (NCAR) Boulder, Colo., U.S.A.     

Do conservative solutes migrate at average pore-water velocity?

According to common understanding, the advective velocity of a conservative solute equals the average linear pore-water velocity. Yet direct monitoring indicates that the two velocities may be different in heterogeneous media. For example, at the Camp Dodge, Iowa, site the advective velocity of discrete Cl- plumes was less than one tenth of the average pore-water velocity calculated from Darcy's law using the measured hydraulic gradient, effective porosity, and hydraulic conductivity (K) from large-scale three-dimensional (3D) techniques, e.g., pumping tests. Possibly, this difference reflects the influence of different pore systems, if the K relevant to transient solute flux is influenced more by lower-K heterogeneity than a steady or quasi-steady water flux. To test this idea, tracer tests were conducted under controlled laboratory conditions. Under one-dimensional flow conditions, the advective velocity of discrete conservative solutes equaled the average pore-water velocity determined from volumetric flow rates and Darcy's law. In a larger 3D flow system, however, the same solutes migrated at approximately 65% of the average pore-water velocity. These results, coupled with direct observation of dye tracers and their velocities as they migrated through both homogeneous and heterogeneous sections of the same model, demonstrate that heterogeneity can slow the advective velocity of discrete solute plumes relative to the average pore-water velocity within heterogeneous 3D flow sytems.     

Utility of the Hadley Centre sea ice and sea surface temperature data set (HadISST1) in two widely contrasting coral reef areas

The HadISST1 sea surface temperature data set is examined for two contrasting areas: the Chagos Archipelago, central Indian Ocean which has a small (approximately 3 degrees C) annual temperature fluctuation, and Abu Dhabi in the southern Arabian Gulf whose annual air temperature fluctuation of approximately 24 degrees C is the largest known for coral reef habitats. The HadISST1 data are shown to match air temperature records closely, both in terms of annual moving averages and residual analysis. Temperatures in 1998 caused massive mortality of corals in the Indian Ocean: sea surface temperature (SST) values causing this were 33.8 degrees C in the Arabian Gulf at a time when average daily air temperature was over 40 degrees C, while in Chagos the SST lethal to corals was 29.8-29.9 degrees C, when air temperatures peaked at about 31 degrees C. The HadISST1 record was searched back to 1870 for previous abnormal peaks: one of 29.7 degrees C was found for Chagos SST in 1972, though this did not cause coral mortality. Analysis of 12-month running means of the residuals from the annual cycle show that, between 1870 and 1999, the largest SST deviations occurred between October 1997 and May 1998 in Chagos and between August 1998 and July 1999 near Abu Dhabi. The event of 1998-1999 was the largest in these regions for at least 130 years. SSTs have risen over the last three decades at rates of about 0.22 degrees or 0.23 degrees per decade in both locations.     

Un Pachyerymnoceras arabique dans le Callovien supérieur du Dahar (Sud tunisien), nouvel élément de datation du membre Ghomrassène (formation Tataouine) ; corrélations avec l'Arabie Saoudite et le Moyen-Orient

The first ammonite discovered at the base of the Ghomrassène Member of the Tataouine Formation belongs to a species of Pachyerymnoceras from the Latest Callovian (Solidum Zone) of the Arabian province. The underlying Krechem el Miit Member is also dated Late Callovian, with a fauna of Pachyerymnoceras from the Lower Athleta Zone in Algeria. The associated faunas (echinids, brachiopods) are the same, as well as the faunas of the overlying Ksar Haddada Member, which is dated also Late Callovian, referring to the brachiopods faunal succession in Saudi Arabia. Correlations with other areas in Tunisia, Saudi Arabia and Middle East underline the same sedimentary evolution during a second-order transgressive half-cycle. To cite this article: R. Enay et al., C. R. Geoscience 334 (2002) 1157–1167.

Résumé

La première ammonite découverte à la base du membre Ghomrassène de la formation Tataouine est un Pachyerymnoceras de la partie supérieure du Callovien supérieur (Zone à Solidum) de la province arabique. Le membre Krechem el Miit sous-jacent est aussi daté du Callovien supérieur par des Pachyerymnoceras connus dans la partie inférieure de la Zone à Athleta en Algérie. La faune associée (échinides, brachiopodes) est la même que celle du membre Ksar Haddada sus-jacent, daté également du Callovien supérieur par référence à la succession des brachiopodes en Arabie Saoudite. Les corrélations avec les autres régions de Tunisie, l'Arabie Saoudite et le Moyen-Orient mettent en évidence une même évolution sédimentaire au cours d'un demi-cycle transgressif de deuxième ordre. Pour citer cet article : R. Enay et al., C. R. Geoscience 334 (2002) 1157–1167.     

Quantifying Exploration Sufficiency While Accommodating Judgment

A computationally efficient method to direct and evaluate the sufficiency of site characterization data is demonstrated on two synthetic subsurface geometries. This method, entitled reliability-based exploration (RBE), combines three-dimensional subsurface analysis and uncertainty in the geologic data to produce a quantifiable measure of data sufficiency, which is directly related to the probability of project success. The RBE approach is illustrated with a three-dimensional finite element soil deformation model, where interfaces separating geologic units are the subsurface data of interest. The RBE method begins with a prior model of the subsurface, which can include geologic judgement. As new information is collected at a site, the prior subsurface model is updated with site data. During the RBE analysis, both a probability of project success and the location of the next boring are computed. The robustness of this computation is illustrated with a practical example of the automatic exploration of two different pinching geometries. The subsurface geometry is imposed on these two sites to demonstrate the importance of geology on the computed results. A comparison of the modeled subsurface and the true (or defined) subsurface at each site shows a close match directly below the proposed structure, where calculated settlement is most sensitive to uncertainty in geology. The study demonstrated that to achieve the same exploration sufficiency more data are required at the site with abruptly changing subsurface geometry than at the site with gradually changing geometry.     

Anthropogenic, Climatic, and Hydrologic Trends in the Kosi Basin, Himalaya

A great debate exists concerning theinfluence of land-use and climatic changes onhydrology in the Himalayan region and its adjacentplains. As a representative basin of the Himalayas, westudied basinwide land-use, climatic and hydrologictrends over the Kosi Basin (54,000 km²) in themountainous area of the central Himalayan region. Theassessment of anthropogenic inputs showed that thepopulation of the basin grew at a compound rate ofabout one percent per annum during the past fourdecades. The comparison of land-use data between thesurveys made during the 1960s and 1978–1979 did notreveal noticeable trends in land-use change. Theanalysis of meteorological and hydrological timeseries from 1947 to 1993 showed some increasingtendency of temperature and precipitation. Thestatistical tests of hydrologic trends indicated anoverall decrease in discharge on the Kosi River andits major tributaries. The decreasing trends ofstreamflow were more significant during the low-flowmonths. The statistical analysis of homogeneityshowed that the climatic as well as the hydrologictrends were more localized in nature lacking adistinct basinwide significance.     

应力状态对膨胀土SWCC的影响研究

探讨了应力对膨胀土的土-水特征曲线的影响。试验研究表明：膨胀土的首次干湿循环过程的“滞后”现象明显。应力状态对膨胀土的土-水特征曲线影响显著,与常规试验方法相比,一维固结状态和各向等压应力状态下的土-水特征曲线更具线性关系,干湿循环甚至出现了逆向回滞现象。