Karroo basalts of the Tuli Syncline,Rhodesia

Karroo (Triassic-Jurassic) sediments and lavas occupy a N.N.E.-trending trough known as the Tuli Syncline 230 km in length by 45 km wide along the southern margin of Rhodesia. The structure is fault bounded, especially on the north, and comprises a sequence of gently inward dipping lava flows cut by numerous E-W and N.N.E. striking dolerite dykes. The igneous rocks have been subdivided on the basis of mineralogy and chemistry into a stratigraphic sequence of limburgites near the base, olivine basalts and upper augite-plagio-clase-phyric basalts. In addition, rare shoshonite and absarokite types occur. Twentyfour new silicate analyses are comparable to those from rocks in the neighbouring Nuanetsi Province of Rhodesia, and show strong affinities to the northern province Karroo basalts of southern Africa as defined by Cox,McDonald andHornung (1967).     

分布式水文-土壤-植被模式的改进及气候水文Off-line模拟试验

文中对引进的高分辨率 (94 2 .5m× 94 2 .5m)分布式水文 土壤 植被模式 (DHSVM) ,针对海、滦河流域的特点进行了改进 ,主要包括 :(1)改变蒸散发模拟方法 ,用改进的Penman Monteith模式模拟海滦河流域的蒸发 ,较好地模拟出 1a内的两个峰值 ,最大值出现在 4～ 6月 ,次大值出现在 7～ 8月 ;(2 )改变水文模式结构 ,用多站点气候观测资料内插到模式网格点 ,充分实现了分布式水文模拟 ;(3)发展新的水文、植被、土壤参数化方案 ,对 33个参数分区计算和确定 ,并重点对土壤孔隙度 φ、土壤蓄水能力θfc、叶面指数LAI、随机阻抗γs 等 11个参数进行调试和修订 ,提高了水文模拟精度。用改进的DHSVM模式分别对滦河、桑干河流域蒸散发、地下水位、土壤湿度、土壤水下渗、产流、汇流与径流等水文过程进行Off line模拟试验 ,模拟结果与实测值一致性较好 ,滦河流域 1979～ 1991年、桑干河流域 1979～ 1987年水文模拟效率系数分别为 0 .89和 0 .82 ,均高于国内其他相关研究     

Stratal patterns: a proposal of classification and examples from the Dolomites

Abstract A classification of stratal patterns is proposed from outcrop analysis of the Middle-Upper Triassic succession of the Dolomites (northern Italy). Stratal patterns are classified into two groups: stratal discontinuities and internal geometries. The stratal discontinuities are further subdivided into unconformities and synsedimentary stratal discontinuities on the basis of whether significant time is missing at the discontinuity. Internal geometries are further subdivided into planes and internal patterns.     

水文模式DHSVM与区域气候模式RegCM2/China嵌套模拟试验

本研究在改进水文 -土壤 -植被模式DHSVM ,用气候观测资料驱动DHSVM进行模拟试验的基础上 ,建立了区域气候模式RegCM2 /China与水文模式DHSVM的嵌套系统 ,将区域气候模式对中国和东亚地区控制试验 (目前气候情景 )和敏感性试验 (未来 2×CO2 气候情景 )结果用双线性插值方法降尺度 (downscaling)到滦河、桑干河流域的 8个气象站点 ,然后再用数字高程模式DEM插值到DHSVM的细网格点 ,驱动水文模式进行嵌套模拟试验。试验结果表明 ,滦河、桑干河流域在未来大气中CO2 浓度加倍情况下 ,地面气温呈一致的增加趋势 ,年平均气温增加2 .8℃ ;两流域未来降水也呈增加趋势 ,滦河、桑干河流域年降水量分别增加 6mm和 4 6mm ;两流域未来蒸发量有所增加 ,年均蒸发量增加 2 9mm ;未来滦河流域年径流深减少 2 7mm ,流量减少 14 .72× 10 8m3 ,桑干河流域径流深增加 2 6mm ,流量增加 12 .2 2× 10 8m3 ,两流域合计 ,流量减少 2 .5× 10 8m3 ;未来滦河、桑干河流域径流深趋向一致 ,分别为 74和 71mm ,约为全国目前平均径流深 2 84mm的 1/ 4。可见 ,两流域未来总体上仍呈现暖干化趋势。本研究发展的嵌套模式系统具有一定的预测能力 ,而且通过参数移植 ,可应用于中国其他流域     

Recovery of the highly acidified Clearwater Lake watershed, Ontario, Canada, simulated with the ILWAS model

The Integrated Lake Watershed Acidification Study (ILWAS) model was used to simulate the recovery of the highly acidified Clearwater Lake, Ontario. Recovery started in the mid-1970s and continued through the 1980s in response to an estimated 30–50% decrease in S deposition from smelter emissions in nearby Sudbury, Ontario. Appreciable recovery of Clearwater Lake between the mid-1970s and 1987 is simulated by the ILWAS model, as indicated by a 50% decrease in SO⁻₄ concentration, an 80% decrease in total Al concentration, an increase in acid-neutralizing capacity (ANC) from −60 to −17 μeq/l, and an increase in pH from 4.2 to 4.8. These decreases in acidic constituents are in good agreement with monitoring data. Long-term simulations indicate that deacidification may continue until 2020, if S deposition rates remain at or less than the 1987 level. Simulations for years beyond 2020 yield yearly average ANC values of 18–40 μeq/l and pH values of 6.2–6.6, which are comparable to the estimated pre-smelter pH of 6.0–6.5 for Clearwater Lake. The agreement between simulated and monitoring data for the first 10 a of recovery and the simulated long-term recovery of the lake to its presmelter level of acidity lend confidence in the capability of numerical models to simulate the reversibility of watershed acidification and suggest that some highly acidic watersheds may eventually recover, given substantial decreases in acid deposition.     

Possible Impacts of Global Warming on the Hydrology of the Ogallala Aquifer Region

The Ogallala or High Plains aquifer provides water for about 20% of the irrigated land in the United States. About 20 km³ (16.6 million acre-feet) of water are withdrawn annually from this aquifer. In general, recharge has not compensated for withdrawals since major irrigation development began in this region in the 1940s. The mining of the Ogallala has been pictured as an analogue to climate change in that many GCMs predict a warmer and drier future for this region. In this paper we attempt to anticipate the possible impacts of climate change on the sustainability of the aquifer as a source of water for irrigation and other purposes in the region. We have applied HUMUS, the Hydrologic Unit Model of the U.S. to the Missouri and Arkansas-White-Red water resource regions that overlie the Ogallala. We have imposed three general circulation model (GISS, UKTR and BMRC) projections of future climate change on this region and simulated the changes that may be induced in water yields (runoff plus lateral flow) and ground water recharge. Each GCM was applied to HUMUS at three levels of global mean temperature (GMT) to represent increasing severity of climate change (a surrogate for time). HUMUS was also run at three levels of atmospheric CO₂ concentration (hereafter denoted by [CO₂]) in order to estimate the impacts of direct CO₂ effects on photosynthesis and evapotranspiration. Since the UKTR and GISS GCMs project increased precipitation in the Missouri basin, water yields increase there. The BMRC GCM predicts sharply decreased precipitation and, hence, reduced water yields. Precipitation reductions are even greater in the Arkansas basin under BMRC as are the consequent water yield losses. GISS and UKTR climates lead to only moderate yield losses in the Arkansas. CO₂-fertilization reverses these losses and yields increase slightly. CO₂ fertilization increases recharge in the base (no climate change) case in both basins. Recharge is reduced under all three GCMs and severities of climate change.     

Simulations of mesospheric and thermospheric IR radiance measured in the CIRRIS-1A shuttle experiment

Comprehensive simulations of upper atmospheric limb radiance from 2.5 to 25 μm, carried out using a moderate-resolution non-LTE code and a series of model atmospheres, are compared with data from the 1991 CIRRIS-1A shuttle experiment. Good agreement, typically within a factor of two, is found at most wavelengths over a five-order-of-magnitude range in spectral radiance. The comparisons yield information on the temperature profile, the production and concentrations of odd-oxygen and odd-hydrogen species in the mesopause region and NO in the thermosphere, and the kinetics of CO₂ vibrational states.     

Jebel Marra,a dormant volcano in Darfur Province,Western Sudan

The geology of the Tertiary-Recent Marra mountains is shown on photogeological maps and described using data from short field visits and from previous literature. The 200 km long mass is aligned N-S parallel to basement trends; it comprises a stratified complex 2000 m thick of olivine basalts, pyroclastics and trachytes. Coarse detrital deposits testify to concomitant erosion. The spectacular Deriba caldera contains a deep crater lake and associated hot springs and fumeroles. The Marra mountains lie at the intersection of two transcontinental tectono-volcanic zones, ENE from Cameroon to Red Sea and SSE from Libya to Kenya.