the measurement of the synoptic scale wind over the ocean mesoscale and microscale features of the turbulent winds over the ocean are related to the synoptic xscale winds in terms of published spectral forms for the microscale a mesoscale valley and published values of u var u var v and z l as defined in the text and as obtained for moderate to gale force winds the frequencies involved correspond to periods longer than 1 hour and extend to the microscale which starts at a period near 2 min or so and continues to the kolmogorov inertial range nondimensional spectra that span both the mesoscale and the microscale are derived as a function of u f nz and z l where z is 10 m l is the monin obukhov stability length and is evaluated at 10 m for the same different values of z l produce a range of values of u which in turn result in variations of the eddy structure of the mesoscale and microscale spectra both conventional anemometer averages and remotely sensed winds contain a random component of the mesoscale wind in their values these components are differences and not errors when winds are compared and quantitative values for these differences are given ways to improve the measurement of the synoptic scale wind by transient ships data buoys and scatterometers on future spacecraft are described these ways are longer averaging times for ships and data buoys depending on the synoptic conditions and pooling spacecraft data to form superobservations design considerations for future remote sensing systems are given

short wave directional properties in the vicinity of atmospheric and oceanic fronts 1 the author estimated and investigated mean wave directions and directional spread parameters of 0 505 hz ocean waves using data from 24 5 mhz hf ocean radar the author described temporal and spatial variabilities of the short wave field the short wave direction is a good indication of wind direction the spread parameter was related to the variability of wind direction the author examined the case that an atmospheric front or an oceanic front exists in the hf ocean radar observation area in the case of an atmospheric front the short wave direction changed with the passage of the atmospheric front furthermore the complicated frontal structure which cannot be verified from a weather chart was revealed narrow directional spread was observed in the vicinity of the convergent front which was reproduced using a simplified model based on the wave action conservation law the result shows that wave refraction associated with a frontal convergent zone is important in determining the spatial variability of short wave directional properties

remote sensing of wind speed at sea surface level using hf skywave echoes from decametric waves using an hf skywave radar to study the decametric sea waves it appears that their amplitudes do not saturate as the wind speed increases a measurement method based on the kahma sea wave spectrum is proposed and radar estimations of the wind speed are compared with in situ measurements performed on board a ship the rms difference between the two measurements is 2 5m s and is probably mainly due to the spatial variability in the wind speed

an empirical relation between ocean surface wind direction and the bragg line ratio of hf radar sea echo spectra twelve days of tests with six u s air force oth b over the horizon radars produced a large surface wind direction data set covering much of the north atlantic and pacific oceans we compare wind directions derived from the sea echo bragg line ratio with concurrent in situ measurements made by ships and buoys and with the national meteorological center nmc global data assimilation system model using 1900 such comparisons we derive an empirical model for the dependence of surface wind direction on the bragg line ratio of hf radar sea echoes the rms difference between the empirical model and the combined nmc and in situ data is about 33 when only very high quality radar data are used the rms difference between the radar and buoy measurements alone is 24 the pattern of surface streamlines derived from 1 day s radar measurements over the northeastern pacific ocean closely matches that derived from the nmc model

fault distribution and timing in the central irish sea basin well data analysis and the interpretation of 2d and 3d seismic reflection data provide valuable insights into the distribution and timing of fault activity within the central irish sea basin cisb structural and stratigraphic relationships have been used to constrain the timing of fault movements and to interpret the mapped fault patterns in terms of the tectonic evolution of the area four main fault trends are identified at the top lower triassic sherwood sandstone group level i a ne sw fault trend that parallels the basin bounding faults and is believed to be of mesozoic age ii a pervasive system of north south trending faults that cross cut the earlier ne sw trending faults which manifests evidence of later mesozoic extension followed by post oligocene transpressional fault reactivation iii a nne ssw trending steeply dipping fault set iv a wnw ese trending conjugate extensional set that formed perpendicular to the nne ssw trending transpressional faults during late tertiary dextral shearing early tertiary axial centred basin inversion and regional exhumation have resulted in the elevation of the sherwood sandstone reservoir to shallow structural levels within the basin continued fault reactivation into late tertiary time has resulted in the compartmentalization of mapped structural closures and suggests that trap integrity is a major exploration risk factor in the cisb the central irish sea basin cisb is a ne sw trending graben located between the kish bank basin to the nw and the st george s channel and cardigan bay basins to the se fig la the cisb forms part of a linked system of mesozoic basins between the uk and ireland which also

the variscan fold thrust belt of southeast ireland and its control on early mesozoic extension and deposition a method to predict the sherwood sandstone

sedimentation in an actively tilting half graben sedimentology and stratigraphy of late tournaisian visean mississippian lower carboniferous carbonate rocks in south county wexford ireland the wexford basin south eastern ireland is a ne sw trending sedimentary basin containing carbonates and evaporites deposited during the late tournaisian and visean two separate depositional areas are defined on the basis of facies and facies associations sediments were deposited in inner ramp lagoonal and peritidal environments near rosslare and in a more open marine shallow to moderately deep water mid to outer ramp environment in the western area around duncormick thick breccia deposits that occur in the wexford basin formed as a result of i fault movement that produced syn sedimentary debris flows in the late chadian breccia type i ii dissolution of anhydrite gypsum and subsequent collapse of sedimentary strata breccia type ii and iii fracturing and brecciation of porous rock caused by the movement of high temperature late diagenetic fluids along fault planes breccia type iii the ne sw facies polarity displayed by both sedimentary successions was the result of nw se extension and the reactivation of the ne sw trending wexford boundary fault during the chadian extension at the se margin of the basin with downthrow to the nnw gave the basin a half graben character thickening of the debris flow deposits to the sw suggests that while the half graben was being tilted it also underwent a ne sw block rotation due to an axial component of that normal fault

hf bistatic ocean doppler spectra simulation versus experimentation we simulate the doppler spectra that can be obtained under experimental conditions from bistatic high frequency oceanic radar for this we combine the bistatic second order theory with the characteristics of the full radar system such as antenna patterns range attenuation and postprocessing of the received signal because of the sharp variation of the bistatic geometry at short range we show that it is crucial to take these effects into account for the correct interpretation of the first order bragg peaks the second order spectrum is more robust to the system characteristics but can under some conditions also suffer from its artifacts especially in the vicinity of the secondary peaks a comparison is made with experimental spectra acquired recently with a wellen radar system on the mediterranean coast the wave watch iii model is used to simulate directional wave height spectra after a preliminary validation with in situ buoy measurements experimental and simulated doppler spectra agree generally well except in the case where the directional wave spectrum has little energy in the line of sight of the radar

late cenozoic reorganization of the arabia eurasia collision and the comparison of short term and long term deformation rates the arabia eurasia collision deforms an area of 3 000 000 km2 of continental crust making it one of the largest regions of convergent deformation on earth there are now estimates for the active slip rates total convergence and timing of collision related deformation of regions from western turkey to eastern iran this paper shows that extrapolating the present day slip rates of many active fault systems for 3 7 million years accounts for their total displacement this result means that the present kinematics of the arabia eurasia collision are unlikely be the same as at its start which was probably in the early miocene 16 23 ma or earlier in some but not all active fault systems short term 10 year and long term 5 million year average deformation rates are consistent there is little active thickening across the turkish iranian plateau and possibly the interior of the greater caucasus these are two areas where present shortening rates would need more than 7 million years to account for the total crustal thickening and where there are structural and or stratigraphic data for pre late miocene deformation we suggest that once thick crust up to 60 km built up in the turkish iranian plateau and the greater caucasus convergence took place more easily by crustal shortening in less elevated regions such as the zagros simple folded zone the south caspian region and foothills of the greater caucasus or in other ways such as westward transport of turkey between the north and east anatolian faults the time and duration of this changeover are not known for certain and are likely be diachronous although deformation started or intensified in many of the currently active fault systems at 5 2 ma

recurrence of volcanic activity along the roman comagmatic province tyrrhenian margin of italy and its tectonic significance 1 the roman comagmatic province rcp developed along the nw se striking extensional tyrrhenian margin of italy since middle pleistocene and includes ultrapotassic small eruptive centers and large volcanic districts by means of a review and statistical analysis of a large data set of radiometric ages we demonstrate that in the rcp major eruptive cycles occurred at different volcanic districts almost simultaneously and with an almost constant recurrence time our analysis started with the alban hills volcanic district where a detailed 40ar 39ar chronology of the eruptive cycles has been recently achieved and then extended to include a database of 264 radiometric ages of the rcp volcanics published since 1980 statistical treatment of the data set shows a marked non poissonian behavior of volcanic activity through the whole magmatic province with climax of each major eruptive cycle occurring simultaneously at the different districts approximately every 48 kyr the concomitant eruption of many volcanic districts spreading over a 250 km long chain implies a control mechanism acting at a regional scale after discussing the possible relationship between tectonics sea level changes and volcanic activity we hypothesize that constant rates of slab retreat during middle pleistocene could have been a key factor controlling the rate of magma upwelling and the major cycles of recharge of the magma chambers as a working hypothesis we propose that the duration of the cycles may be related to 1 progressive weakening of the crust due to magma underplating or 2 cyclic injection of convective plumes into the mantle wedge

source rock burial history and seal effectiveness key facets to understanding hydrocarbon exploration potential in the east and central irish sea basins the timing of hydrocarbon generation from carboniferous source rocks and the lack of evapo rites within the triassic mercia mudstone group seal sequence have contributed significantly to the lack of exploration success in the triassic sherwood sandstone play of the central irish sea basin apatite fission track analysis afta combined with vitrinite reflectance data from the central irish sea basin and adjacent areas indicates that maximum burial and heating of the carboniferous section was achieved by the early cretaceous the long residence period for trapped hydrocarbons generated in the early cretaceous combined with the ineffectiveness of the mercia mudstone group seal caused by the absence of annealing halites and the presence of thief sandstones led to hydrocarbon loss through trap breaching during subsequent tectonic events in contrast maximum burial of carboniferous source rocks in the central east irish sea hydrocarbon province was achieved in the late cretaceous early tertiary giving a shorter residence period for generated hydrocarbons the combination of a short residence period and the presence of a halite bearing mercia mudstone seal sequence significantly improved hydrocarbon retention within the sherwood sandstone reservoir if traps were episodically breached during the late tertiary they were recharged by the inversion process which caused gas expansion spill from charged traps and lateral remigration of hydrocarbons updip the inversion related pressure drop also caused retrograde condensate dropout from gas accumulations to provide a supply of late condensate for preferential spill and remigration

observations of hurricane hortense with two over the horizon radars hurricane hortense was observed in the atlantic ocean on 12 september 1996 by two high frequency over the horizon radars in texas and virginia looking at backscatter from the ocean surface dual radar coverage permits construction of an unambiguous surface wind direction field and a vector surface current field with about 15 km resolution in the storm s vicinity the known location of a storm band coincides with a region of surface convergence indicated by the radar the surface current field lags the wind field by about 3 h and shows the strongest ocean response to the right of the storm track with near inertial rotation in the storm s wake analysis of surface wave directionality shows that it depends on the recent wind direction history at each point

stratigraphic and structural analysis of the late palaeozoic mesozoic of ne wales and liverpool bay implications for hydrocarbon prospectivity interpretation of seismic lines from the offshore ne wales area has provided information on the structural and stratigraphic evolution of the southern part of morecambe liverpool bay basin wide megasequence boundaries are present between the dinantian and overlying sequences and between the upper carboniferous and permo triassic megasequences geological information obtained from seismic lines has been used to construct an e w geological cross section and a basin analysis summary chart for the ne wales cheshire onshore area stratigraphic interpretations have been considered in an assessment of the petroleum potential of the region the distribution of carboniferous oil and gas prone source rocks is a key element in predicting hydrocarbon accumulations source rock maturity may have been reached in the offshore area prior to a phase of inversion and uplift during tertiary times fault controlled hydrocarbon traps generated during triassic jurassic rifting were modified during tertiary inversion and new structures were generated

a hybrid beam forming and direction finding method for wind direction sensing based on hf radar recent studies indicate that the poor antenna sidelobe level of phased array high frequency hf radars degrades the performance of bragg ratio estimation for wind direction measurements to explore this issue this paper improves the previous model of wind direction estimation for phased array hf radars and the effect of unsatisfactory array patterns on bragg ratio estimation is theoretically analyzed moreover a hybrid beam forming and direction finding method in which wind direction is measured by reducing the influence of unsatisfactory array patterns on bragg ratio estimation is proposed for multifrequency hf radars installed along the coast of zhejiang province in china the procedure for implementing this scheme is also presented in detail wind directions derived from 8 05 10 7 16 8 and 19 2 mhz radar data are compared with measurements collected with anemometers at three sampling locations to verify the proposed method and the measurements with root mean square errors from 19 5 to 26 6 show that this strategy is effective for wind direction measurements we recommend adopting the proposed method or using similar approaches to estimate wind direction based on hf radars especially in situations where the array pattern is not sufficiently narrow

hydrocarbon prospectivity in the irish sea area insights from recent exploration of the central irish sea peel and solway basins abstract compared with the prolific success of the triassic play in the east irish sea basin eisb the lack of hydrocarbon discovery in neighbouring permo triassic basins of the irish sea has been an enigma however recent exploration of the peel solway and central irish sea basins has provided new insights into the geology of these basins and the controls upon hydrocarbon prospectivity in the irish sea area regional seismic interpretation suggests that 12 of the 15 exploration wells drilled in the basins adjacent to the eisb tested valid structural closures at top triassic reservoir level re evaluation of the irish sea petroleum system reveals that although effective reservoirs occur in the lower middle triassic ormskirk sandstone formation and evaporites in the middle upper triassic mercia mudstone group provide a regional top seal the major factor controlling hydrocarbon prospectivity is the limited presence of effective source rocks in the underlying carboniferous section a further control upon prospectivity is the timing of hydrocarbon migration from those areas where carboniferous source rocks were deposited and preserved the namurian basinal marine oil and gas prone shales which form the principal source of hydrocarbons for the triassic play in the eisb are restricted to an east west fairway extending from the eisb into the kish bank basin rocks of this age are absent from the peel and solway basins as a result of variscan uplift and erosion however palaeogeographical reconstructions based on well and outcrop data suggest that even if preserved the depositional environment was not conductive to the formation of marine oil and gas prone source rocks well and seismic data suggest that rocks of namurian age were not deposited in the central irish sea area which remained high during much of dinantian and namurian time potential source rock development in the central irish sea area is therefore limited to the westphalian section which is organically lean and dominated by intertinitic kerogens potential hydrocarbon traps in the central irish sea peel and solway basins formed largely as a result of early cretaceous tectonism and were subsequently modified by fault reactivation during tertiary uplift phases trap formation appears to postdate the most likely timing of hydrocarbon charge which this study suggests would have occurred in late triassic and jurassic time hydrocarbon entrapment in the eisb may have been favoured by limited early cretaceous uplift coupled with renewed hydrocarbon generation and re migration during early tertiary time it is concluded that the remaining prospectivity of the triassic play in the irish sea area is likely to be restricted to the proven play fairway within the eisb

role of the kazerun fault zone in the formation and deformation of the zagros fold thrust belt iran 1 the kazerun fault is a n s trending fault zone which obliquely truncates the nw se trending zagros fold thrust belt this active fault zone is an ancient structural lineament which has controlled the structure sedimentation and subsidence of the central part of the zagros since the early cambrian and has had an influence on the formation of the hydrocarbon system of the belt the kazerun fault limited the distribution of the cambrian hormuz salt the major decollement horizon that separates the precambrian basement from the thick sedimentary cover to the west its later reactivation with other n s trending fault zones e g the izeh fault zone during the cretaceous resulted in major sedimentary thickness and facies variations along the belt this study presents a new interpretation for the evolution of the kazerun fault zone based on field evidence and a review of various published and unpublished data it is argued that at the surface the fault zone is delineated by four north south trending segments and that marked differences occur in the distribution of deformation on either side of the fault segments in the late tertiary during this time these segments acted as transfer faults lateral ramps linking different segments of the zagros deformation fronts

the development of irish offshore sedimentary basins a variety of ensialic mesozoic and cenozoic sedimentary basins surround ireland three main periods of basin development occurred the first in the permo triassic produced a series of small rift basins which nucleated along reactivated generally caledonian structures the second in the mid and late jurassic represents a period of crustal extension and rifting the third phase reflects thermal subsidence of cretaceous and tertiary age and coincides with seafloor spreading in the north atlantic the basins developed in response to general east west extension simple extensional structures accompanied by crustal thinning dominated in the north south trending porcupine basin the ne sw oriented basins in the celtic sea slyne erris donegal and rockall areas developed in a transtensional setting until early cretaceous times the goban spur basins at the confluence of regional structural trends and adjacent to the continent ocean boundary are dominated by transtensional structures the effects of early tertiary alpine compression are seen especially in the celtic sea basins the basins whilst having some broad geological similarities which reflect eustatic sea level variations differ in their detailed evolution each basin experienced unique facets of local structural control tectonic history and facies distribution