Quasi-specular sea scatter with modified reflection coefficient

The paper deals with the relationship between the sea surface wind speed (U) and the backscattering coefficient (σ⁰) for microwave frequencies and quasi specular range of angles. Valenzuela’s effective reflection coefficient based on the theory of scattering of electromagnetic waves from rought dielectric surfaces has been introduced in the expression of backscattering coefficient and the final result compared with the σ⁰-U relationship derived fromSEASAT scatterometer and concurrent sea truth data.     

Parameterization of sea surface drag under varying sea state and its dependence on wave age

Momentum and energy exchange at air–sea interface through wind stress is very important for air–sea interaction studies, ocean modeling, and climate studies. The accurate representation of wind stress, in terms of drag coefficient, is a key factor in estimating the momentum transfer at the interface. The drag coefficient, in general, estimated using bulk formulae does not take into account the influence of wave age. This study examines the dependence of wave age on computed surface drag coefficient obtained by combining the Toba 3/2-power law with Froude number scaling, resulting in a new drag formulation (hereafter referred as RP formulation). We demonstrate that our proposed formulation is in good conjunction with established theories for both young and mature waves. Our investigation shows the theoretical formulation advocated earlier by Guan and Xie (hereafter referred as GX) overestimated the surface drag for mature waves as wind speed tends to increase. In addition, the formulation by GX was not verified by observational data. In the present work, for validation purpose, we use time series measurement of meteorological and oceanographic data from a deep water location in the Indian Ocean which was tested with both RP and GX formulations. We find that the proposed RP formulation, which embeds the 3/2 power of wave-age, shows a better match for both young and mature waves with the results of Janssen compared to the hypothesis of conventional wave age used by GX.     

Wind sedimentation in the Jafurah sand sea, Saudi Arabia

The Jafurah sand sea of the Eastern Province of Saudi Arabia extends along the Arabian Gulf coastline from Kuwait in the north to the Rub Al Khali in the south, a distance of about 800 km. Sand drifts southward to south-eastward from regions of high wind energy in the north to low wind energy in the south. The aeolian landscape is zoned, with areas of deflation, transport and deposition from north to south. Drift rates in the zone of transport, near Abqaiq, range from 2 m³ m-w^-1 yr^-1 on sabkhas, to 29 m³ m-w^-1 yr^-1 on the crests of dunes. Average drift rates of approximately 18 m³ m-w^-1 yr^-1 observed during the study can cause about 1 m of accumulation per 5500 yr in a 100 km zone of deposition downwind, not including the bulk transport represented by the forward advance of dunes. Dune advance ranged from 23 m (2.9 m high dune) to 3 m (23 m high dune) during April-October 1980. The study area consists of dune, interdune, sand sheet and siliciclastic sabkha terrains, each of which is characterized by differing drift rates, and differing rates of erosion or deposition. Sedimentation occurs by lateral movement of dunes and interdunes, and vertical accretion by sand sheets and sabkhas.     

Prediction by regression and intrarange data scatter in surface-process studies

Modeling is a major component of contemporary earth science, and regression analysis occupies a central position in the parameterization, calibration, and validation of geomorphic and hydrologic models. Although this methodology can be used in many ways, we are primarily concerned with the prediction of values for one variable from another variable. Examination of the literature reveals considerable inconsistency in the presentation of the results of regression analysis and the occurrence of patterns in the scatter of data points about the regression line. Both circumstances confound utilization and evaluation of the models. Statisticians are well aware of various problems associated with the use of regression analysis and offer improved practices; often, however, their guidelines are not followed. After a review of the aforementioned circumstances and until standard criteria for model evaluation become established, we recommend, as a minimum, inclusion of scatter diagrams, the standard error of the estimate, and sample size in reporting the results of regression analyses for most surface-process studies.     

青藏铁路沿线的大风特征及风压研究

选取青藏高原及周边66个气象站资料, 分析了青藏高原及青藏铁路沿线1971-2000年大风日数的空间分布特征及建站以来大风和风向特征, 计算了百年一遇的最大风速和风压. 分析发现: 青藏高原大风日数主要集中在青藏铁路沿线地区, 年际和年代际变化明显; 铁路沿线极端最大风速和历年平均最大风速都出现在铁路中部的托托河, 风向多为偏西风; 铁路沿线50 a、 100 a一遇的10 min平均最大风速和风压都出现在安多地区. 以新疆达扳城为参考站, 推算出青藏铁路沿线各站的列车停驶临界风速. 为确保列车运营安全, 建议在昆仑山口至错那湖间的高山地段风口和列车转弯处建造防风设施.     

山东地区风电场功率特性及其负荷相关性分析

随着山东省风电装机容量的快速增加和风电场规模的不断扩大,风电对电网安全运行的影响日益显现。风力发电是一种特殊的电力,它以自然风为原动力,风资源的随机性和间歇性决定了风电机组的输出特性也是波动和间歇的。本文通过对风电有功功率的波动特性及功率特性进行分析,仿真了不同容量风电入网对电网有功功率平衡的影响,总结了山东地区风电入网后电网有功功率呈现的特点,这对指导大规模风电入网运行的发电计划有参考价值。     

风电场风资源代表年分析法

针对代表年常规方法的局限性,采用风速年景划分法对风场风资源代表年进行订正。该方法弥补了常规方法的不足,且计算简单,便于应用。     

Rising sea level

Predictions suggest that the world sea level will rise dramatically in the twenty-first century as a result of atmospheric and oceanic warming arising from the 'greenhouse effect'. Changing sea level is nothing new to the geologist, but rapid rates of rise over short periods and potentially devastating impacts present a major challenge to society in the need to provide effective management of global biogeochemical cycles.     

Comparison of electron density models with incoherent scatter radar observations at the equator

This paper points out certain discrepancies when the incoherent scatter radar observations at Jicamarca and the electron density models, (the Bent andiri) were compared. In all cases the bottomside semi-thickness of the observed profile was significantly greater than that of both Bent andiri models. The decay constants associated with the topside ionosphere for the observed profiles were generally greater than that of the two models, the difference being more pronounced in theiri model. The results call for a revision of the models so that they accurately represent the electron density distribution at the equator.     

A new technology for the measurement of the sea level and the sea state

A considerable proportion of the world population lives and works on or near coasts. Therefore, knowledge of the physical processes which affect the coast is very important. These include the tides of the sea and the oceanic and meteorological circulation patterns that cause variations of the sea level and generate waves. The sea level is measured by tide-gauges, while the height of waves may be determined by a variety of special devices. Radar systems have been applied for the sea level and wave measurements since the late 1990s. This paper presents results from a field test or such a radar application and aims to give the reader help and support in the selection of an appropriate radar-gauge system to measure sea level and sea state. The underlying physical principles of radar and its application in distance measurements are not subjects of this paper.     

Blast vibration control in the presence of delay scatter and random fluctuations between blastholes

It is becoming increasingly important, from an environmental viewpoint, to minimize vibrations induced in urban dwellings by blasting. The present study illustrates how the delay interval between blastholes can be chosen to control and minimize the vibration energy within the structural response band of most houses. In particular, it is shown that the only possibility of reducing such energy is to employ a delay interval in the range 10–35 ms. However, the induced vibrations are also dependent upon the accuracy of the delay initiators as well as the level of random fluctuations between each blasthole signature. It is shown that only very accurate electronic delays give the possibility of utilizing fully the delay sequence in order to control structural vibrations. If the vibration emission from each blasthole is totally uncorrelated with that of any other blasthole then the resulting amplitude spectrum of the blast will be totally unpredictable. This situation occurs irrespective of the delay initiation sequence or its accuracy. Under these conditions it is impossible to predict the blast-induced energy lying within the structural response band.     

Crustal structure of the Balearic sea

Within the frame of the German-French project ANNA-1970, two long refraction profiles were investigated north and south of the island of Majorca.

For the southern Balearic Basin an oceanic crust can be derived from the travel-time curves consisting of a 4.0 km thick Cenozoic sedimentary layer with: V_p = 2.35 (km/sec) + 0.35 (sec⁻¹) × Z (km) and a 5 km thick layer with: V_p = 4.0 (km/sec) + 0.28 (sec⁻¹) × Z (km)

The transition to the upper mantle takes place at a depth of 12 km. Directly south of Majorca a crustal thickening was measured which may be caused by the process of crustal shortening. P]In the northern Balearic Basin a faulted transitional type of crust has been observed indicating probably an embryonic and juvenile ocean expansion.     

Time dependence of axial pile response

This communication describes an approximate method for generalizing homogeneous, linearly elastic, subgrade type solutions of axial pile response to account for soil creep behaviour. The method is very simple to apply and can be used in conjunction with either analytical or numerical elastic solutions. Exact solutions for limiting cases and finite difference solutions in both space and time are presented to confirm that errors introduced by the approximations are small. Because of the theoretical basis of this approach it is anticipated that method can be used with other pile problems, lateral and axial, for both subgrade adn continuum idealizations. Methods for generalizing the results to more complex conditions such as non-homogeneity or time varying loads are given.     

Orientation dependence of luminescence in plagioclase

The orientation dependence of the luminescence of a well-characterized plagioclase crystal at room temperature and 40 K is reported. A beam of H ⁺ ions was used to provide the excitation. Ion beam luminescence provides emissions effectively from the bulk of the material, and therefore minimizes the contribution to the luminescence from atypical regions. The intensity of the luminescence is strongly orientation-dependent. The intensity and photon energy, particularly of the red/infrared and yellow emission bands, vary significantly. We interpreted this as resulting from Fe ³⁺ and Mn ²⁺ activator ions, respectively, on crystallographic sites with low point symmetry. An emission at 860 nm was also significantly orientation-dependent. The blue luminescence showed the least variability. At room temperature, a 350 nm near-UV emission was noted, whereas at 40 K, emissions were at 240, 260, 300 and 340 nm. UV emissions may result from Na ⁺ diffusion along interfaces within the plagioclase, notably albite-law (010) twins. This variability has significant consequences for the use of single-crystal quantitative luminescence techniques. We have also studied the dependence of the peak intensities and profiles during prolonged ion beam bombardment with heavier (He ⁺) ions. Broadening of the red-infrared emission is interpreted as reflecting growing amorphization of the sample.     

Frequency dependence of equatorial ionospheric scintillations

Simultaneous observations of amplitude scintillations at 40 MHz, 140 MHz and 360 MHz radiated from ATS-6 satellite at 34° E longitude were made at Ootacamund near the magnetic equator in India. It has been found that the frequency variation of scintillation index (S ₄) isS ₄ ∞f ^?n , withn being about 1·2 only for weak scintillations, i.e., so long as the scintillation index does not exceed 0·6 at the lower frequency. For strong scintillations (S ₄>0·6) where multiple scattering may be present, the exponentn itself is a function of the intensity of scintillation, the scintillation indices at two frequencies are related by:S ₄(f ₁)=S ₄(f ₂) exp [1·3 log(f ₂/f ₁)(1?S ₄(f ₂)] so long asf ₂/f ₁≤3. Thus knowing scintillation index at a given frequency one can estimate the scintillation index at another frequency. This will be of significant importance for communication problems. Evidence is also shown for the reversal of the frequency law in cases of intense scintillations.