Mesoscale nocturnal jetlike winds within the planetary boundary layer over a flat,open coast

Mesoscale nocturnal jetlike winds have been observed over a flat, open coast. They occur within the planetary boundary layer between 100 and 600 m. At times the wind shear may reach 15 m s^-1 per 100 m. Unlike the common low-level jet that occurs most often at the top of the nocturnal inversion and only with a wind from the southerly quadrant, this second kind of jet exists between nocturnal ground-based inversion layers formed by the cool pool, or mesohigh, and the elevated mesoscale inversion layer over the coast. It occurs mostly when light % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaiikaiabgs% MiJkaaiwdacqGHsislcaaI2aGaaeyBaiaabccacaqGZbWaaWbaaSqa% beaacqGHsislcaaIXaaaaOGaaiykaaaa!3FCF!\[( \leqslant 5 - 6{\text{m s}}^{ - 1} )\] geostrophic winds blow from land to sea and when the air temperature over adjacent seas is more than 5 °C warmer than that over the coast. This phenomenon may be explained by combined Venturi and gravity-wind effects existing in a region from just above the area a few kilometres offshore to 100–600 m in height approximately 40–50 km inland because this region is sandwiched between the aforementioned two inversion layers.     

From subduction to transform motion: a seabeam survey of the Hellenic trench system

Preliminary results of a multi-narrow beam survey of the Hellenic trench system, in the Eastern Mediterranean, are presented. The southwestern Ionian branch is divided in small basins, partly filled with Pleistocene sediments. The morphology suggests that the basins are deformed by a compressional stress acting roughly perpendicularly to the trench along N50°E. This direction is the direction of the regional slip vector of the shallow thrust-type earthquakes. The structure of the southeastern Pliny-Strabo branch is quite different. Narrow en-e´chelon slots, oriented N40°E, have been mapped within the main troughs oriented N60°E. The regional earthquake slip vector is also oriented along N40°E. We conclude that the Hellenic trench system is an active subduction system, dominated by thrust along the Ionian branch and by transform motion along the Pliny-Strabo branch.     

Determination of the momentum flux at the air-sea interface under variable meteorological and oceanographic conditions: Further application of the wind-wave interaction method

Simultaneous observations of wind, wave, and stability parameters made recently by several authors provide an evaluation of the contribution of these factors to the determination of wind stress on the sea surface. It is shown that under diabatic conditions the wind-wave interaction method of determining wind stress is superior to the method utilizing correction for stability. The implication is that the contribution from waves is more important to the stress than that from stability. Thus, the wind-wave interaction method may be applicable under a variety of conditions. For general meteorological-oceanographic applications, a nomograph is also provided for estimating the wind stress from commonly available wind and wave parameters.     

Variations of b‐values at the western edge of the Ryukyu Subduction Zone,north‐east Taiwan

Using earthquakes relocated in north‐east Taiwan, we estimated b‐value distribution along a cross‐section located near the Ryukyu slab edge, and four b‐value anomalous areas are evidenced: (1) a high b‐value body lying on top of a low Vp, low Vs and high Vp/Vs sausage‐like body was considered as a region of enhanced partial melt or water supply above which seismicity occurs; (2) beneath the Ilan Plain, an anomalous area characterized by b‐values slightly higher than 1.1 might give evidence to the magma conduits to the Kueishantao Island; (3) above the Ryukyu Wadati‐Benioff zone, at depths ranging from 90 to 110 km, a high b‐value anomaly might correspond to the depth where dehydration occurs in the subducting oceanic plate; and (4) a low b‐value area located within the Ryukyu slab, at depths ranging from 70 to 90 km, might be linked to the compressive mechanisms shown by focal mechanisms and the bending of the subducting plate.     

Petrogenesis of the Northwest Africa 4898 high‐Al mare basalt

Northwest Africa (NWA) 4898 is the only low‐Ti, high‐Al basaltic lunar meteorite yet recognized. It predominantly consists of pyroxene (53.8 vol%) and plagioclase (38.6 vol%). Pyroxene has a wide range of compositions (En_12–62Fs_25–62Wo_11–36), which display a continuous trend from Mg‐rich cores toward Ca‐rich mantles and then to Fe‐rich rims. Plagioclase has relatively restricted compositions (An_87–96Or_0–1Ab_4–13), and was transformed to maskelynite. The REE zoning of all silicate minerals was not significantly modified by shock metamorphism and weathering. Relatively large (up to 1 mm) olivine phenocrysts have homogenous inner parts with Fo ~74 and sharply decrease to 64 within the thin out rims (~30 μm in width). Four types of inclusions with a variety of textures and modal mineralogy were identified in olivine phenocrysts. The contrasting morphologies of these inclusions and the chemical zoning of olivine phenocrysts suggest NWA 4898 underwent at least two stages of crystallization. The aluminous chromite in NWA 4898 reveals that its high alumina character was inherited from the parental magma, rather than by fractional crystallization. The mineral chemistry and major element compositions of NWA 4898 are different from those of 12038 and Luna 16 basalts, but resemble those of Apollo 14 high‐Al basalts. However, the trace element compositions demonstrate that NWA 4898 and Apollo 14 high‐Al basalts could not have been derived from the same mantle source. REE compositions of its parental magma indicate that NWA 4898 probably originated from a unique depleted mantle source that has not been sampled yet. Unlike Apollo 14 high‐Al basalts, which assimilated KREEPy materials during their formation, NWA 4898 could have formed by closed‐system fractional crystallization.     

Observation of saturnian stream particles in the interplanetary space

In January 2004 the dust instrument on the Cassini spacecraft detected the first high-velocity grain expelled from Saturn - a so-called stream particle. Prior to Cassini’s arrival at Saturn in July 2004 the instrument registered 801 faint impacts, whose impact signals showed the characteristic features of a high-velocity impact by a tiny grain. The impact rates as well as the directionality of the stream particles clearly correlate with the sector structure of the interplanetary magnetic field (IMF). The Cosmic Dust Analyser (CDA) registered stream particles dominantly during periods when the IMF direction was tangential to the solar wind flow and in the prograde direction. This finding provides clear evidence for a continuous outflow of tiny dust grains with similar properties from the saturnian system. Within the compressed part of co-rotating interaction regions (CIRs) of the IMF, characterized by enhanced magnetic field strength and compressed solar wind plasma, CDA observed impact bursts of faster stream particles. We find that the bursts result from the stream particles being sped up inside the compressed CIR regions. Our analysis of the stream-particle dynamics inside rarefaction regions of the IMF implies that saturnian stream particles have sizes between 2 and 9 nm and exit the saturnian systems closely aligned with the planet’s ring plane with speeds in excess of 70 km s⁻¹.     

Long-term polar motion prediction using normal time–frequency transform

This paper presents normal time–frequency transform (NTFT) application in harmonic/quasi-harmonic signal prediction. Particularly, we use the normal wavelet transform (a special NTFT) to make long-term polar motion prediction. Instantaneous frequency, phase and amplitude of Chandler wobble, prograde and retrograde annual wobbles of Earth’s polar motion are analyzed via the NTFT. Results show that the three main wobbles can be treated as quasi-harmonic processes. Current instantaneous harmonic information of the three wobbles can be acquired by the NTFT that has a kernel function constructed with a normal half-window function. Based on this information, we make the polar motion predictions with lead times of 1 year and 5 years. Results show that our prediction skills are very good with long lead time. An abnormality in the predictions occurs during the second half of 2005 and first half of 2006. Finally, we provide the future (starting from 2013) polar motion predictions with 1- and 5-year leads. These predictions will be used to verify the effectiveness of the method proposed in this paper.     

Simulation of probability distributions commonly used in hydrological frequency analysis

Random variable simulation has been applied to many applications in hydrological modelling, flood risk analysis, environmental impact assessment, etc. However, computer codes for simulation of distributions commonly used in hydrological frequency analysis are not available in most software libraries. This paper presents a frequency‐factor‐based method for random number generation of five distributions (normal, log–normal, extreme‐value type I, Pearson type III and log‐Pearson type III) commonly used in hydrological frequency analysis. The proposed method is shown to produce random numbers of desired distributions through three means of validation: (1) graphical comparison of cumulative distribution functions (CDFs) and empirical CDFs derived from generated data; (2) properties of estimated parameters; (3) type I error of goodness‐of‐fit test. An advantage of the method is that it does not require CDF inversion, and frequency factors of the five commonly used distributions involves only the standard normal deviate. Copyright © 2006 John Wiley & Sons, Ltd.     

Efficient methods of discharge measurements in rivers and streams based on the probability concept

Regularities exist in fluid flows and can be represented by a set of constants. These constants are functions of the parameter of a probability distribution that exhibits resilience and stability under various flow conditions. Together, these regularities form a network and interact with each other, such that if one is known then the others can be determined from it. The regularities and their network explain the various fluid‐flow phenomena and can be used in analysis of rivers and streams. For example, they can be used as the basis to develop simple and efficient methods of discharge measurements as presented herein, which only require velocity sampling at a single point on a water surface or a few points on a single vertical. Because of their simplicity and the short time requirement, these methods can be easily automated for collecting discharge data in unsteady, high flows that are badly needed for real‐time flow forecasting and design of flood control structures, and for advancing the fundamental, scientific knowledge in hydrology. Copyright © 2005 John Wiley & Sons, Ltd.