surface wind response to oceanic fronts 1 the response of surface winds to ocean fronts characterized by sharp gradients in both sea surface temperature sst and ocean currents was analyzed using scatterometer nscat and quikscat wind data and gulf stream path positions in conjunction with simulations made with the pennsylvania state university psu national center for atmospheric research ncar mesoscale model mm5 all match ups between each scatterometer pass and the gulf stream path were visually examined and only those for which the wind field was free of atmospheric fronts or large curvature over a reasonably straight segment of the gulf stream were selected ten match ups met these criteria for the period studied from 16 september 1996 to 29 june 1997 for nscat and from 24 july 1999 to 31 december 2000 for quikscat changes in the modeled surface wind field across the front in each of the ten cases agree well with changes in the observed winds our findings suggest that the perturbation pressure gradient resulting from the thermal forcing by the front accounts for the decrease in wind speed when moving from warm to cold water and the increase observed in the converse in the cases examined the adjustment of the surface wind to the front occurred as a result of the vertical motion induced by horizontal divergence convergence and advection in the marine atmospheric boundary layer mabl the dynamical forcing associated with strong surface currents is also shown to modify scatterometer derived winds finally the numerical simulations suggest that the dynamical and thermal effects are very nearly additive

interannual variability in the north atlantic ocean s temperature field and its association with the wind stress forcing abstractspectral analyses of the north atlantic temperature field in the simple ocean data analysis soda reanalysis identify prominent and statistically significant interannual oscillations along the gulf stream front and in large regions of the north atlantic a 7 8 yr oscillatory mode is characterized by a basinwide southwest to northeast oriented propagation pattern in the sea surface temperature sst field this pattern is found to be linked to a seesaw in the meridional dipole structure of the zonal wind stress forcing taux in the subpolar gyre the sst and taux fields of this mode are shown to be in phase opposition which suggests a cooling effect of the wind stress on the upper ocean layer over all this mode s temperature field is characterized by a strong equivalent barotropic component as shown by covariations in ssts and sea surface heights and by phase coherent behavior of temperature layers at depth with the sst field recent improvements of multivariate singular spectrum analysis

geothermometry of exsolved augites from the laramie anorthosite complex wyoming exsolved augite pyroxenes from the ferromonzonite border facies of the ferrosyenite in the laramie anorthosite complex have been studied with the transmission electron microscope and the electron microprobe to determine their exsolution histories the lindsley and andersen 1983 geothermometer gives initial crystallization temperatures of 1000 c for the bulk augite crystal wo32 en22 fs46 exsolved lamellae are predominantly pigeonites with very low calcium contents wo1 3 en23 24 fs71 74 and have formation temperatures estimated to be in the range of 600 to 975 c the uniform compositions of lamellae and hosts despite the range in lamellar size and orientation suggest that either 1 the ferromonzonite experienced an extended plateau in cooling or a reheating event at 600 to 650 c or 2 the pyroxenes recorded a blocking temperature two feldspar geothermometry on exsolved feldspars also records 600 c and suggests that these low temperatures are not blocking temperatures

a coupled decadal prediction of the dynamic state of the kuroshio extension system abstractbeing the extension of a wind driven western boundary current the kuroshio extension ke has long been recognized as a turbulent current system rich in large amplitude meanders and energetic pinched off eddies an important feature emerging from recent satellite altimeter measurements and eddy resolving ocean model simulations is that the ke system exhibits well defined decadal modulations between a stable and an unstable dynamic state here the authors show that the decadally modulating ke dynamic state can be effectively defined by the sea surface height ssh anomalies in the 31 36 n 140 165 e region by utilizing the ssh based ke index from 1977 to 2012 they demonstrate that the time varying ke dynamic state can be predicted at lead times of up to 6 yr this long term predictability rests on two dynamic processes 1 the oceanic adjustment is via baroclinic rossby waves that carry interior wind forced anomalies westward into the ke region and 2 the low frequency ke variability influenc

river channel changes in the rhone delta france since the end of the little ice age geomorphological adjustment to hydroclimatic change and natural resource management abstract this study provides a representative example of a river affected by artificial width contraction and consequent bed incision in a context of sea level rise geomorphological adjustment in the rhone catchment since the final stage of the little ice age has been induced by hydroclimatic change and human disturbances these adjustments are examined to highlight the response of two sand bed distributary channels of the rhone delta by using methods such as sedimentological evidence historical sources planimetric resurvey repeated longitudinal and cross profiling and hydraulic data the geomorphological and hydraulic responses to channel changes are characterised and their consequences assessed it is shown that the reduction of sediment yield is a combined effect of a decrease of flood frequency sediment dredging and building of dams on the rhone river and its tributaries the combination of decreased catchment sediment yield artificial width contraction increased stream power and boundary shear stress is the cause of channel incision of the rhone river in the coastal zone the increase of the rhone river s stream power has facilitated the transport of sediment down to the subdeltas engineering works designed to stabilise the planform and to limit overbank flooding caused 1 channel entrenchment thus 2 the destabilization of infrastructure e g bridges quays along the river 3 the lowering of the phreatic water table in the floodplain which in turn induced 4 soil salinization change in salt wedge position eventually the channelization led to 5 an increase of the flood hazard and risks because although more rare the inundations have become more destructive however the contribution of the large flood events is negligible in terms of progressive channel in filling because of their low frequency finally no relation exists between the vertical adjustment of the rhone channel through entrenchment and relative sea level which rose at a rate of up to 2 mm year 1 during the 20th century clearly natural resource management in particular engineering activities were the main cause of the river channel changes that occurred during the last century

signature of the agulhas current in high resolution satellite derived wind fields abstract 5 years of systematic envisat advanced synthetic aperture radar asar acquisitions and 8 years of observations from the jason 2 altimeter are used to investigate the signature of the agulhas current on high resolution between 1 and 5 km satellite derived winds the satellite wind observations are analysed together with co located ocean current sea surface temperature sst and significant wave height information satellite derived winds cannot be considered current relative over the agulhas current sar and altimeter winds increase in magnitude over the agulhas current in all up down and cross current wind conditions with contributions from both the ocean surface current and sst when winds blow against the current strong accelerations in satellite winds are observed at the agulhas current s inshore front with the strongest winds observed 10 km offshore from the location of maximum sst gradient the strong sst gradient appears to drive a thermal wind with a magnitude of about 1 m s and which intensifies abates the predominant alongfront winds at the agulhas current s northern wall the sar dataset shows abnormally high increases in wind speeds during up current conditions in comparisons to the jason 2 derived winds we argue that these differences are caused by the inability of the cmod type algorithms to taken into account the wave field and provide accurate wind speed estimates in conditions where wave height exceed the expected value for a given wind speed our analysis suggests that wave current interactions in regions of strong current shear produce enhanced sea surface roughness signatures and lead to artificially high estimates of sar derived wind speeds there is future potential in using high resolution sar imagery to map strong ocean current fronts and thus improve our ability to monitor ocean surface currents from space

intensification of ocean fronts by down front winds abstract many ocean fronts experience strong local atmospheric forcing by down front winds that is winds blowing in the direction of the frontal jet an analytic theory and nonhydrostatic numerical simulations are used to demonstrate the mechanism by which down front winds lead to frontogenesis when a wind blows down a front cross front advection of density by ekman flow results in a destabilizing wind driven buoyancy flux wdbf equal to the product of the ekman transport with the surface lateral buoyancy gradient destabilization of the water column results in convection that is localized to the front and that has a buoyancy flux that is scaled by the wdbf mixing of buoyancy by convection and ekman pumping suction resulting from the cross front contrast in vertical vorticity of the frontal jet drive frontogenetic ageostrophic secondary circulations ascs for mixed layers with negative potential vorticity the most frontogenetic ascs select a preferred cross front width and do not translate with

boundary layer mechanisms in extratropical cyclones this paper revisits the mechanism for the interaction of the boundary layer with extratropical cyclones two diagnostic approaches are compared ekman pumping and potential vorticity ekman pumping derives from the boundary layer stress which induces convergence and ascent boundary layer potential vorticity contains in a single quantity both the vorticity and stratification these quantities are compared for an idealized extratropical cyclone life cycle simulated with the met office unified model a significant component of the boundary layer stress and thus ekman pumping at occlusion is forced by the cold conveyor belt jet in the unstable boundary layer in contrast much of the boundary layer depth averaged potential vorticity is contained within the stable warm sector region inversion of the warm sector pv indicates a small local deepening of about 2 5 hpa moreover switching off the boundary layer mixing in the unstable cold sector has much more impact than in the stable warm sector the sensitivity of the cyclone and its boundary layer to basic state jet strength is then investigated the maximum friction velocity scales closely with the initial maximum jet strength this demonstrates the important role of the large scale flow in organizing the boundary layer structure changes in the minimum pressure produced by altering the boundary layer parametrization correspond closely to changes in the surface stress averaged over the cyclone different operational changes to the boundary layer scheme produce small and compensating changes to the cyclone minimum pressure over three days crown copyright 2007 reproduced with the permission of the controller of hmso published by john wiley sons ltd

sea level pressure minimum along the kuroshio and its extension abstractatmospheric effects of sea surface temperature sst fronts along the kuroshio and kuroshio extension k ke are investigated by examining spatial characteristics of the climatological sea level pressure slp surface winds and surface heat flux q fields based on an in situ observation dataset a hydrostatic effect of the sst front is observed during the northwesterly monsoon characterized by a westward extending low slp wedge trough slightly south of the peak in q along the k ke ageostrophic surface westerlies crossing slp isobars toward a trough center are found north of the low slp wedge apparently because of the eastward acceleration by the vertical mixing effect this feature of the ageostrophic winds is less pronounced south of it a north south asymmetry arising as vertical mixing accelerates decelerates eastward ageostrophic winds north south of it while the slp trough near the sst front is found nearly year round except for summer its meridional location seasonally migrates pr

channel metamorphosis floodplain disturbance and vegetation development ain river france abstract the purpose of this paper is to describe and explain channel metamorphosis of the ain river in east central france and the effects of this metamorphosis on floodplain disturbance and vegetation development the ain river is a 195 km long stream originating in the jura mountains which flows into the rhone river between lyon france and geneva switzerland the lower 40 km of the ain river beyond the mountain front are situated in a valley of outwash deposits where the floodplain is 0 2 to 1 2 km wide a complex mosaic of floodplain landscape units has developed maps dating back to 1766 and six sets of aerial photographs dated between 1945 and 1991 were used to document changes in channel pattern aerial photos and field surveys were used to compile maps of landscape units based on dominant vegetation life forms species and substrate six maps dated between 1945 and 1991 were digitized in arc info and an overlay was generated to determine the changes in landscape units as related to channel disturbance change from a braided to a single thread meandering channel probably took place in the period 1930 1950 the process of river entrenchment has occurred throughout the holocene but has accelerated in the present century due to shortening of the river course construction of lateral embankments and vegetation encroachment following reservoir construction and cessation of wood cutting and grazing the increase in horizontal channel stability coupled with channel entrenchment have decreased floodplain disturbance and lowered the water table by approximately one meter pioneer and disturbance dependent landscape units have experienced a more terrestrial like succession to an alluvial forest abandoned channels have also been replaced by alluvial forests on poorly drained soils shrub swamp communities of willow and hydrophytic herbaceous plants have been replaced by mixed forests of ash alder black poplar and oak on well drained alluvial soils ash and oak dominated hardwood forests have declined in favor of mesophytic stands of black poplar all types of vegetation but particularly dry grasslands shrublands have been cleared for mines campgrounds agriculture and other types of development using several measures landscape diversity decreased between 1945 and 1991

the influence of sea surface temperature on surface wind in the eastern equatorial pacific weekly to monthly variability abstract temporal correlations between near equatorial surface wind and sea surface temperatures sst at 11 w in the eastern pacific ocean are investigated using data from an array of moored sensors between 5 n and 5 s the signature of tropical instability waves with periods of 20 30 days is apparent in time series of sst and both the meridional and zonal wind components results indicate the existence of a band of pronounced horizontal divergence in the surface wind field associated with the large meridional sst gradient equatorial front normally located just north of the equator perturbations of the equatorial front by the instability waves induce fluctuations in the overlying winds evidence of the air sea coupling is stronger in time series of the meridional gradients of wind and sst than between time series of the variables themselves the meridional differencing serves as a high pass filter in the space domain which removes planetary scale wind fluctuations that are unrelated to the local sst

atmospheric responses to kuroshio sst front in the east china sea under different prevailing winds in winter and spring abstractatmospheric responses to the kuroshio sst front in the east china sea under different prevailing winds are examined using high resolution observations and numerical modeling satellite data reveal a significant in phase relationship between sst and surface wind speed indicative of ocean to atmosphere influence the atmospheric response varies according to the relative surface wind direction with respect to the sst front orientation under the alongfront condition low high slp anomalies are found on the warmer colder flank of the front accompanied by surface wind convergence divergence enhanced precipitation and frequent cumulus convection appear over the warm kuroshio suggesting an atmospheric response extending into the free troposphere under the cross front condition when the air blows from cold to warm warm to cold sst divergence convergence is located directly over the sst front and its magnitude is proportional to the downwind sst gradient under such prevailing winds the

atmospheric circulations induced by a midlatitude sst front a gcm study the atmospheric effects of sea surface temperature sst anomalies over and near western boundary currents are a matter of renewed interest the general circulation model gcm of the laboratoire de meteorologie dynamique lmd z has a zooming capability that allows a regionally increased resolution this gcm is used to analyze the impact of a sharp sst front in the north atlantic ocean two simulations are compared one with climatological ssts and the other with an enhanced gulf stream front the results corroborate the theory developed previously by the present team to explain the impact of oceanic fronts in this theory the vertical velocity at the top of the atmospheric boundary layer has two components mechanical and thermal it is the latter that is dominant in the tropics while in midlatitudes both play a role in determining the wind convergence above the boundary layer the strengthened sst front does generate the previously predicted stronger ascent above the warmer water south of the front and stronger descent above the colder waters to the north in the gcm simulations the ascent over the warm anomalies is deeper and more intense than the descent

influence of small scale north atlantic sea surface temperature patterns on the marine boundary layer and free troposphere a study using the atmospheric arpege model a high resolution global atmospheric model is used to investigate the influence of the representation of small scale north atlantic sea surface temperature sst patterns on the atmosphere during boreal winter two ensembles of forced simulations are performed and compared in the first ensemble hres the full spatial resolution of the sst is maintained while small scale features are smoothed out in the gulf stream region for the second ensemble smth the model shows a reasonable climatology in term of large scale circulation and air sea interaction coefficient when compared to reanalyses and satellite observations respectively the impact of small scale sst patterns as depicted by differences between hres and smth shows a strong meso scale local mean response in terms of surface heat fluxes convective precipitation and to a lesser extent cloudiness the main mechanism behind these statistical differences is that of a simple hydrostatic pressure adjustment related to increased sst and marine atmospheric boundary layer temperature gradient along the north atlantic sst front the model response to small scale sst patterns also includes remote large scale effects upper tropospheric winds show a decrease downstream of the eddy driven jet maxima over the central north atlantic while the subtropical jet exhibits a significant northward shift in particular over the eastern mediterranean region significant changes are simulated in regard to the north atlantic storm track such as a southward shift of the storm density off the coast of north america towards the maximum sst gradient a storm density decrease is also depicted over greenland and the nordic seas while a significant increase is seen over the northern part of the mediterranean basin changes in rossby wave breaking frequencies and weather regimes spatial patterns are shown to be associated to the jets and storm track changes

investigating the local atmospheric response to a realistic shift in the oyashio sea surface temperature front abstractthe local atmospheric response to a realistic shift of the oyashio extension sst front in the western north pacific is analyzed using a high resolution hr 0 25 version of the global community atmosphere model version 5 cam5 a northward shift in the sst front causes an atmospheric response consisting of a weak surface wind anomaly but a strong vertical circulation extending throughout the troposphere in the lower troposphere most of the sst anomaly induced diabatic heating is balanced by poleward transient eddy heat and moisture fluxes collectively this response differs from the circulation suggested by linear dynamics where extratropical sst forcing produces shallow anomalous heating balanced by strong equatorward cold air advection driven by an anomalous stationary surface low to the east this latter response however is obtained by repeating the same experiment except using a relatively low resolution lr 1 version of cam5 comparison to observations suggests that the hr respo

geochemical relationships between anorthosite and associated iron rich rocks laramie range wyoming rocks enriched in iron oxide and mafic silicates are commonly present as minor volumes of proterozoic anorthosite complexes in the laramie range wyoming anorthositic rocks gabbros and iron oxide ore have been chemically analyzed to determine if the spatial association is a result of genetic relationships between the rock types variations in abundances of ree th sc and sr in whole rock and in mineral separates from anorthositic rocks provide evidence for the presence of trapped intercumulus liquid initial 87sr 86sr ratios in apatites separated from iron oxide ore 0 70535 0 00004 are analogous to initial 87sr 86sr ratios in laramie range anorthosite 0 70531 and 0 70537 in addition ree abundances in calculated parental liquids for both anorthositic rocks and iron ore are similar providing further evidence for a comagmatic relationship trace element and textural characteristics of spatially associated laramie range gabbros indicate that they are not mixtures of the trapped liquid and cumulus components which formed anorthositic rocks it is suggested that gabbros are early differentiation products of a high al gabbroic magma which subsequently crystallized large volumes of plagioclase to produce the anorthosite massif

satellite measurements reveal persistent small scale features in ocean winds four year averages of 25 kilometer resolution measurements of near surface wind speed and direction over the global ocean from the quikscat satellite radar scatterometer reveal the existence of surprisingly persistent small scale features in the dynamically and thermodynamically important curl and divergence of the wind stress air sea interaction over sea surface temperature fronts throughout the world ocean is evident in both the curl and divergence fields as are the influences of islands and coastal mountains ocean currents such as the gulf stream generate distinctive patterns in the curl field these previously unresolved features have important implications for oceanographic and air sea interaction research

midlatitude wind stress sea surface temperature coupling in the vicinity of oceanic fronts the influences of strong gradients in sea surface temperature on near surface cross front winds are explored in a series of idealized numerical modeling experiments the atmospheric model is the naval research laboratory coupled ocean atmosphere mesoscale prediction system coamps model which is fully coupled to the regional ocean modeling system roms ocean model a series of idealized two dimensional model calculations is carried out in which the wind blows from the warm to cold side or the cold to warm side of an initially prescribed ocean front the evolution of the near surface winds boundary layer and thermal structure is described and the balances in the momentum equation are diagnosed the changes in surface winds across the front are consistent with previous models and observations showing a strong positive correlation with the sea surface temperature and boundary layer thickness the coupling arises mainly as a result of changes in the flux richardson number across the front and the strength of the coupling coefficient grows quadratically with the strength of the cross front geostrophic wind the acceleration of the winds over warm water results primarily from the rapid change in turbulent mixing and the resulting unbalanced coriolis force in the vicinity of the front much of the loss gain of momentum perpendicular to the front in the upper and lower boundary layer results from acceleration deceleration of the flow parallel to the front via the coriolis term this mechanism is different from the previously suggested processes of downward mixing of momentum and adjustment to the horizontal pressure gradient and is active for flows off the equator with sufficiently strong winds although the main focus of this work is on the midlatitude strong wind regime calculations at low latitudes and with weak winds show that the pressure gradient and turbulent mixing terms dominate the cross front momentum budget consistent with previous work

ocean atmosphere covariability in the western arabian sea abstract the western arabian sea exhibits strong spatial variability in sea surface temperature sst during the southwest monsoon with changes in sst that can exceed 5 c over 200 km exploration of satellite based and in situ data shows a strong connection between mesoscale sst features and changes in the atmospheric boundary layer the fundamental relationship is that of weak strong wind velocities overlying cold warm sst features there are also coherent changes in other near surface meteorological parameters such as the air sea temperature difference and relative humidity indicating changes in the stability of the planetary boundary layer over the mesoscale sst features these relationships are similar to those recently reported over the equatorial pacific tropical instability wave region this observed covariability of atmospheric boundary layer structure and sst results in variations of the surface heat and moisture fluxes latent heat flux is modified by changes in relative humidity principa

paleomagnetism of the middle proterozoic laramie anorthosite complex and sherman granite southern laramie range wyoming and colorado we present the results of a combined paleomagnetic and 40ar 39ar geochronologic investigation of the middle proterozoic laramie anorthosite complex and sherman granite in the southern laramie range of wyoming and colorado anorthosites and monzosyenites of the laramie anorthosite complex yield a well defined characteristic magnetization of northeast declination d and moderate negative inclination i although antipodal normal and reverse polarity magnetizations are present at three sites a grand mean direction from 29 of 35 sites in the complex is d 44 6 i 48 7 k 77 4 95 3 1 alternating field af and thermal demagnetization behavior and rock magnetic experiments indicate that magnetization is carried by low ti titanomagnetite of single or pseudo single domain character that occurs as elongate to rod shaped inclusions in plagioclase and potassium feldspar the sherman granite contains a dual polarity magnetization that is less well defined than that of the laramie anorthosite complex but similar in declination and inclination d 53 1 i 48 1 k 46 5 95 7 6 n 8 14 sites rock magnetic data indicate the primary carrier of remanence in sherman granite is magnetite the 40ar 39ar geochronologic data from sherman granite hornblende biotite and microcline indicate that subsolidus cooling was moderate to relatively rapid through the range of temperatures over which magnetization was blocked and that the age of remanence is about 1415 ma microcline data indicate that the laramie anorthosite complex and sherman granite have probably not been thermally remagnetized paleomagnetic poles from the laramie anorthosite complex and sherman granite are indistinguishable at the 95 confidence level and individual virtual geomagnetic poles vgps from both units are combined to provide a mean pole at 215 0 e 6 7 s k 46 9 a95 3 5 n 37 vgps the location of this pole is similar to paleomagnetic poles derived from 1480 ma to 1450 ma intrusions elsewhere in north america but it plots significantly north of those from middle proterozoic sedimentary strata of the belt supergroup and sibley group in addition to the characteristic magnetization samples from some sites in sherman granite contain a remanence of southeast declination and shallow negative inclination d 154 9 i 16 0 k 90 6 95 9 7 n 4 sites this secondary magnetization was probably acquired during late paleozoic time

on the coupling of wind stress and sea surface temperature a simple quasi equilibrium analytical model is used to explore hypotheses related to observed spatial correlations between sea surface temperatures and wind stress on horizontal scales of 50 500 km it is argued that a plausible contributor to the observed correlations is the approximate linear relationship between the surface wind stress and stress boundary layer depth under conditions in which the stress boundary layer has come into approximate equilibrium with steady free atmospheric forcing warmer sea surface temperature is associated with deeper boundary layers and stronger wind stress while colder temperature is associated with shallower boundary layers and weaker wind stress two interpretations of a previous hypothesis involving the downward mixing of horizontal momentum are discussed and it is argued that neither is appropriate for the warm to cold transition or quasi equilibrium conditions while one may be appropriate for the cold to warm transition solutions of a turbulent large eddy simulation numerical model illustrate some of the processes represented in the analytical model a dimensionless ratio a is introduced to measure the relative influence of lateral momentum advection and local surface stress on the boundary layer wind profile it is argued that when a 1 and under conditions in which the thermodynamically induced lateral pressure gradients are small the boundary layer depth effect will dominate lateral advection and control the surface stress

deep atmospheric response to the spring kuroshio over the east china sea abstractthe atmospheric response to the spring kuroshio front over the east china sea is investigated using a suite of high resolution satellite data and a regional atmospheric model the atmospheric response appears to extend beyond the marine atmospheric boundary layer with frequent occurrence of cumulus convection in spring quick scatterometer quikscat wind speed shows a clear effect of sea surface temperature sst with high low wind speed observed over the warm cold tongue this in phase relationship between sst and surface wind speed is indicative of sst influence on the atmosphere wind convergence is found on the warmer flank of the kuroshio front accompanied by a narrow rainband the analysis of satellite borne radar measurements indicates that deep convection appears over the kuroshio warm tongue in the spring season with enhanced convective precipitation frequent occurrence of cumulus convection and increased precipitation cloud tops in altitude these deep convective activities

late holocene floodplain incision and alluvial fan formation in the central grampian highlands scotland chronology environment and implications a section cut across an alluvial fan and the underlying floodplain terrace in the central grampian highlands provides an unusually complete record of late holocene events at ca 2 7 2 4 cal kyr bp floodplain aggradation was replaced by net floodplain incision pollen evidence and charcoal counts provide no evidence for contemporaneous anthropogenic landscape change and the timing of the transition suggests that it reflects an increase in high magnitude erosive flood events following overall climatic deterioration the overlying fan was deposited by torrential hyperconcentrated flows during three brief storm generated depositional events at ca 2 2 2 1 1 9 1 8 and 0 9 0 7 cal kyr bp separated and succeeded by prolonged periods of stability and peat accumulation during these three events a cumulative total of ca 6750 m3 of sediment was deposited probably in no more than a few hours over a timescale of two millennia these findings imply that proposed links between human activity and the development of alluvial fans or debris cones require reassessment and that different elements of the holocene alluvial landscape have responded in different ways to the same climatic inputs aggregation of dating evidence relating to aggradation or incision of alluvial landforms at different scales therefore may produce misleading results copyright 1999 john wiley sons ltd

channel incision gravel mining and bedload transport in the rhone river upstream of lyon france canal de miribel the miribel canal is a former arm of the rhone embanked between 1848 and 1857 over a length of 18 km to improve navigation at low discharges the impact of this was a hydraulic tilting of the long profile characterised by 4 m of degradation upstream and 4 6 m of aggradation of bedload downstream this phenomenon increased downstream flooding since 1937 a diversion dam has controlled upstream water input thus reducing the transit of the pebble bedload however excessive harvesting of sands and gravels occurred between 1970 and 1980 resulting in a general lowering of the river bed and the accompanying water table with ecological consequences in the alluvial plain and for water supply this development made it all the more necessary to obtain knowledge about the bedload discharges passing through the miribel canal and more broadly about the hydraulic conditions as functions of the varying discharge calculation of shear stresses and grain size measurements on the lateral bars after several floods in 1989 90 show that movement of bed material is initiated at a discharge of 440 m3 s 1 equalled or exceeded 40 days year 1 and becomes general at 550 m3 s 1 equalled or exceeded 30 days year 1 transport discharge is thus relatively frequent and involves distal fluvio glacial deposits composed of fine grained materials potential transport calculated by the meyer peter formula is around 60 000 t year 1 for the range of discharges between 440 and 850 m3 s 1 for these discharge values the canal experiences a loss of materials without replacement from upstream for higher rates of discharge the floodgates let through an unknown quantity of materials which partially make up the loss gravel harvesting ceased in 1991 but the diversion dam will have to be operated in a different way in order to increase the input of bedload into the canal

the effects of mesoscale ocean atmosphere coupling on the large scale ocean circulation abstract small scale variation in wind stress due to ocean atmosphere interaction within the atmospheric boundary layer alters the temporal and spatial scale of ekman pumping driving the double gyre circulation of the ocean a high resolution quasigeostrophic qg ocean model coupled to a dynamic atmospheric mixed layer is used to demonstrate that despite the small spatial scale of the ekman pumping anomalies this phenomenon significantly modifies the large scale ocean circulation the primary effect is to decrease the strength of the nonlinear component of the gyre circulation by approximately 30 40 this result is due to the highest transient ekman pumping anomalies destabilizing the flow in a dynamically sensitive region close to the western boundary current separation the instability of the jet produces a flux of potential vorticity between the two gyres that acts to weaken both gyres

processes shaping the frontal scale time mean surface wind convergence patterns around the kuroshio extension in winter abstracthigh resolution satellite observations and numerical simulations have revealed that climatological mean surface wind convergence and precipitation are enhanced locally around the midlatitud

channel changes due to river regulation the case of the piave river italy this paper deals with the channel changes of the piave river in the eastern alps italy which have occurred during this century in response to human interventions in the fluvial system the flow regime and the sediment supply of the river have been considerably altered by hydroelectric dams flow diversions and gravel mining in addition river dynamics have been affected by the construction of streambank protection structures to document these changes a historical analysis was performed using maps and aerial photographs morphological features that were examined included planform configuration channel width braiding index and bed elevation the results indicate that as a consequence of decreases in the flows and sediment supply remarkable channel changes have occurred in the river during this century especially during recent decades the channel has undergone a general narrowing with a decrease in average width to 35 per cent of its initial value while the braiding index has decreased from about 3 to 1 5 in several reaches the planform pattern has changed from braided to wandering the observed trends of channel change suggest that the river has not yet reached a new equilibrium condition and it may therefore be predicted that reductions in width and braiding intensity are likely to continue in the immediate future copyright 1999 john wiley sons ltd

northern hemisphere winter atmospheric transient eddy heat fluxes and the gulf stream and kuroshio oyashio extension variability abstractspatial and temporal covariability between the atmospheric transient eddy heat fluxes i e t and q in the northern hemisphere winter january march and the paths of the gulf stream gs kuroshio extension ke and oyashio extension oe are examined based on an atmospheric reanalyses and ocean observations for 1979 2009 for the climatological winter mean the northward heat fluxes by the synoptic 2 8 days transient eddies exhibit canonical storm tracks with their maxima collocated with the gs and ke oe the intraseasonal 8 days 3 months counterpart while having overall similar amplitude shows a spatial pattern with more localized maxima near the major orography and blocking regions lateral heat flux divergence by transient eddies as the sum of the two frequency bands exhibits very close coupling with the exact locations of the ocean fronts linear regression is used to examine the lead lag relationship between interannual changes in the northward heat fluxes by the transient

western boundary currents and frontal air sea interaction gulf stream and kuroshio extension abstract in the northern hemisphere midlatitude western boundary current wbc systems there is a complex interaction between dynamics and thermodynamics and between atmosphere and ocean their potential contribution to the climate system motivated major parallel field programs in both the north pacific kuroshio extension system study kess and the north atlantic climate variability and predictability clivar mode water dynamics experiment climode and preliminary observations and analyses from these programs highlight that complexity the gulf stream gs in the north atlantic and the kuroshio extension ke in the north pacific have broad similarities as subtropical gyre wbcs but they also have significant differences which affect the regional air sea exchange processes and their larger scale interactions the 15 yr satellite altimeter data record which provides a rich source of information is combined here with the longer historical record from in situ data to describe and compare the curr

medium and short term channel planform changes on the rivers tay and tummel scotland abstract channel planform change was analysed using a variety of data sources for the medium term 25 years and

interannual modulations of oceanic imprints on the wintertime atmospheric boundary layer under the changing dynamical regimes of the kuroshio extension abstractthe kuroshio extension ke fluctuates between its different dynamic regimes on quasi decadal time scales in its stable unstable regime the ke jet is strengthened weakened and less more meandering the present study investigates wintertime mesoscale atmospheric structures modulated under the changing ke regimes as revealed in high resolution satellite data and data from a particular atmospheric reanalysis era interim in the unstable ke regime a positive anomaly in sea surface temperature sst to the north of the climatological ke jet accompanies positive anomalies in upward heat fluxes from the ocean surface wind convergence and cloudiness as revealed in the atmospheric reanalysis these positive anomalies coincide with local lowering of sea level pressure weaker vertical wind shear warming and thickening of the marine atmospheric boundary layer mabl anomalous ascent and convective precipitation in the stable ke regime by contrast the corresponding imprints of sharp sst

low frequency variability in the midlatitude atmosphere induced by an oceanic thermal front abstract this study examines the flow induced in a highly idealized atmospheric model by an east west oriented oceanic thermal front the model has a linear marine boundary layer coupled to a quasigeostrophic equivalent barotropic free atmosphere the vertical velocity at the top of the boundary layer drives the flow in the free atmosphere and produces an eastward jet parallel to the oceanic front s isotherms a large gyre develops on either side of this jet cyclonic to the north and anticyclonic to the south of it as the jet intensifies during spinup from rest it becomes unstable the most unstable wave has a length of about 500 km it evolves into a meander and eddies detach from the eastern edge of each gyre the dependence of the atmospheric dynamics on the strength t of the oceanic front is studied the gulf stream and kuroshio fronts correspond roughly in the scaling used here to t 7 c for weak fronts t 4 c the circulation is steady and exhibits two large antisymmetric gyres sepa

ocean frontal effects on the vertical development of clouds over the western north pacific in situ and satellite observations abstract a suite of shipboard and satellite observations are analyzed and synthesized to investigate the three dimensional structure of clouds and influences from sea surface temperature fronts over the western north pacific sharp transitions are observed across the kuroshio extension ke front in the marine atmospheric boundary layer mabl and its clouds the ocean s influence appears to extend beyond the mabl with higher cloud tops in altitude along the ke front than the surroundings in winter intense turbulent heat release from the ocean takes place on the southern flank of the ke front where the cloud top penetrates above the mabl and reaches the midtroposphere in this band of high cloud tops frequent lightning activity is observed the results of this study suggest a sea level pressure mechanism for which the temperature gradient in the mabl induces strong surface wind convergence on the southern flank of the ke front deepening the clouds there in early summer sea fog frequently occurs on

observations of sst induced perturbations of the wind stress field over the southern ocean on seasonal timescales the surface wind stress response to sea surface temperature sst over the latitude range 308 608 si n the southern ocean is described from the national aeronautics and space administration s quikscat scatterometer observations of wind stress and reynolds analyses of sst during the 2 yr period august 1999 to july 2001 while ocean atmosphere coupling at midlatitudes has previously been documented from several case studies this is the first study to quantify this relation over the entire southern ocean the spatial structures of the surface wind perturbations with wavelengths shorter than 108 latitude by 308 longitude are closely related to persistent spatial variations of the sst field on the same scales the wind stress curl and divergence are shown to be linearly related respectively to the crosswind and downwind components of the sst gradient the curl response has a magnitude only about half that of the divergence response this observed coupling is consistent with the hypothesis that sst modification of marine atmospheric boundary layer mabl stability affects vertical turbulent mixing of momentum inducing perturbations in the surface winds the nonequivalence between the responses of the curl and divergence to the crosswind and downwind sst gradients suggests that secondary circulations in the mabl may also play an important role by producing significant perturbations in the surface wind field near sst fronts that are distinct from the vertical turbulent transfer of momentum the importance of the wind stress curl in driving ekman vertical velocity in the open ocean implies that the coupling between winds and sst may have important feedback effects on upper ocean processes near sst fronts

influence of the meridional shifts of the kuroshio and the oyashio extensions on the atmospheric circulation abstract the meridional shifts of the oyashio extension oe and of the kuroshio extension ke as derived from high resolution monthly sea surface temperature sst anomalies in 1982 2008 and historical temperature profiles in 1979 2007 respectively are shown based on lagged regression analysis to significantly influence the large scale atmospheric circulation the signals are independent from the enso teleconnections which were removed by seasonally varying asymmetric regression onto the first three principal components of the tropical pacific sst anomalies the response to the meridional shifts of the oe front is equivalent barotropic and broadly resembles the north pacific oscillation western pacific pattern in a positive phase for a northward frontal displacement the response may reach 35 m at 250 hpa for a typical oe shift a strong sensitivity since the associated sst anomaly is 0 5 k however the amplitude but not the pattern or statistical significance strongly depends on the lag and an

petrographical characteristics of the koperberg suite south africa an analogy to massif type anorthosites a swarm of anorthositic dioritic intrusives collectively termed the koperberg suite is scattered over an area of about 3000 km2 in the northwestern cape province namaqualand south africa the intrusive suite is renowned for its associated magmatic copper sulphide deposits transgressive field relationships and the preservation of primary igneous features suggest emplacement of the suite after the main metamorphic event which has been dated at c 1200 ma the distribution of the intrusions seems to have been controlled by vertical shearing which is manifested by antiformal disruptions steep structures in the country rocks post intrusion movement along some of these structures is deemed responsible for metamorphic textures in some mafic bodies igneous breccias associated with some intrusions present evidence of explosive tectonics at the time of emplacement the rock types which compose the mafic suite include andesine anorthosite leucodiorite hypersthene and mica diorite hypersthenite and glimmerite the occurrence of composite intrusions with two or more mafic varieties and the modal gradation between the rock types suggest consanguinity the anorthosite appears to be the oldest member of the series followed by increasingly more mafic varieties such as leucodiorite hypersthene diorite norite and hypersthenite owing to the presence of virtually monomineralic rock types various differentiation trends are recognized series that are dominated by hypersthene brown mica iron titanium oxides and amphibole can thus be delineated microprobe analyses of the major silicates indicate plagioclase compositions of andesine en58 68 for hypersthene and brown mica compositions on the biotite phlogopite boundary the predominance of anorthosite and leucodiorite in the suite suggest an affinity with the massif type anorthosite kindred this relation is supported by other criteria such as the preponderance of hypersthene the age of emplacement the sequence of intrusion en an ratios of plagioclase and hypersthene and the association of syenitic rocks as well as iron titanium oxide and apatite rich assemblages it is provisionally proposed that the okiep district represents the lower levels of an anorthosite complex of the massif type

neodymium strontium and lead isotopes in the maloin ranch pluton wyoming implications for the origin of evolved rocks at anorthosite margins abstract neodymium strontium and lead isotopic data are used in this study to investigate the origin of chemically evolved rocks in the maloin ranch pluton a composite body that borders and intrudes the laramie anorthosite the range of rock types present is similar to that found at the margins of proterozoic anorthosites throughout the world in the maloin ranch pluton these include ferrodiorite at the base of the intrusion overlain progressively by fine grained monzonite monzosyenite and porphyritic granite biotite gabbro and fine grained granitic dikes are present locally at various levels of this sequence the origin of the evolved rocks and their possible relation to associated anorthositic bodies has been much debated in the maloin ranch pluton each rock type has distinct isotopic characteristics which together with trace element data previously reported suggest different source characteristics for each member strontium and neodymium isotopic data for maloin ranch ferrodiorite and laramie anorthositic rocks show considerable overlap consistent with a comagmatic relation biotite gabbro is chemically and isotopically the most primitive rock type in the maloin ranch pluton the data suggest that biotite gabbro has a mantle source but has undergone extensive fractionation in the crust our results suggest that the remainder and bulk of the intrusion formed by partial melting of the lower crust due to the emplacement of the laramie anorthosite maloin ranch fine grained monzonite is chemically more evolved than the underlying ferrodiorite i e lower mg higher silica and alkalis yet has more primitive isotopic characteristics lower isr higher epsilonnd formation of fine grained monzonite by in situ fractionation of ferrodiorite is precluded by both the isotopic data and by mass balance the isotopic data do not rule out formation of fine grained monzonite by fractionation or contamination of ferrodiorite at depth but this model requires that the ferrodiorite is isotopically heterogeneous and that very large volumes of ferrodiorite were present alternatively trace element and isotopic characteristics of the fine grained monzonite are explained by partial melting of mantle derived lower crust added to the margin of the archean wyoming craton at about 1 8 ga neodymium strontium and lead isotope data for maloin ranch monzosyenite and porphyritic granite also suggest a lower crustal source these data indicate a 1 8 ga source component for the maloin ranch monzosyenites but do not require input of archean crust from the wyoming province to the north

response of surface wind divergence to mesoscale sst anomalies under different wind conditions abstractthe response of the atmospheric boundary layer to mesoscale sea surface temperature sst is often characterized by a link between wind stress divergence and downwind sst gradients in this

strontium isotopic constraints on the origin of proterozoic anorthosites abstract the proterozoic giles complex central australia contains an almost complete range of anorthosite types from minor or major layers in gabbronorite intrusions to large anorthosite troctolite bodies to small orthopyroxene anorthosite massifs each type has a distinctive sr isotopic signature anorthosite dominated masses have a regular relationship between ferromagnesian mineralogy initial 87 sr 86 sr and anorthite contents in plagioclase anorthosite troctolite bodies have significant olivine relatively low initial 87 sr 86 sr 0 7038 0 7043 and an 50 69 orthopyroxene dominant anorthosites have relatively high 87 sr 86 sr 0 7045 0 7063 and an 45 60 the pattern is found worldwide detailed study of one intrusion demonstrates that contamination by wall rock granulite produces the higher 87 sr 86 sr values anti correlation between 87 sr 86 sr and an and determines olivine orthopyroxene proportions olivine bearing anorthosites form from a primary aluminous tholeiite magma with plagioclase dominating the liquidus progressive contamination of this parent magma produces a gradation to orthopyroxene anorthosites

the atmospheric response to weak sea surface temperature fronts abstractthe response of the atmospheric boundary layer to fronts of sea surface temperature sst is characterized by correlations between wind stress divergence and the downwind component of the sst gradient and between the wind stress curl and the crosswind component of the sst gradient the associated regression or coupling coefficients for the wind stress divergence are consistently larger than those for the wind stress curl to explore the underlying physics the authors introduce a linearized model of the atmospheric boundary layer response to sst induced modulations of boundary layer hydrostatic pressure and vertical mixing in the presence of advection by a background ekman spiral model solutions are a strong function of the sst scale and background advection and recover observed characteristics the coupling coefficients for wind stress divergence and curl are governed by distinct physics wind stress divergence results from either large scale winds crossing the front or from a thermally direct

influences of channelization on discharge of suspended sediment and wetland vegetation in kushiro marsh northern japan abstract the effects of wetlands on hydrology water quality and wildlife habitat are internationally recognized protecting the remaining wetlands is one of the most important environmental issues in many countries however wetlands in japan have been gradually shrinking due to agricultural development and urbanization which generally lowers the groundwater level and introduces suspended sediment and sediment associated nutrients into wetlands we examined the influences of channelization on discharge of suspended sediment and wetland vegetation in hokkaido northern japan the impact of river channelization was confirmed not only by the sediment budgets but also by river aggradation or degradation after the channelization and by the resultant vegetational changes the budgets of suspended sediment demonstrated that wash load was the predominant component accounting for 95 of the total suspended load delivered into the wetland this suspended sediment was primarily transported into the wetland by flooding associated with heavy rainfall twenty three percent of the wash load and 63 of the suspended bed material load were deposited in the channelized reach which produced aggradation of about 2 m at the end of the reach a shorting of the length of the channel due to channelization of a meandering river steepened the slope and enhanced the stream power to transport sediment this steepening shifted the depositional zones of fine sediment 5 km downstream and aggraded the riverbed development of the watershed may increase not only the water discharge but also the amount of suspended sediments the aggradation reduced the carrying capacity of the channel and caused sediment ladened water to flood over the wetlands the fine sediment accumulated on the wetlands gradually altered the edaphic conditions and wetland vegetation a low percentage 10 to 15 of organic contents of wetlands soil is more evidence indicating that the present condition is far different from normal original vegetation such as sedges and alnus japonica were disappearing from the adjacent areas of the river channel and were being replaced by willow trees salix spp

on the role of sea surface temperature gradients in forcing low level winds and convergence in the tropics abstract we examine the importance of pressure gradients due to surface temperature gradients to low level p 700 mb flow and convergence in the tropics over time scales 1 month the latter plays a crucial role in determining the distribution of cumulonimbus convection and rainfall our approach is to consider a simple one layer model of the trade cumulus boundary layer wherein surface temperature gradients are mixed vertically consistent with ecmwf analyzed data the top of the layer is taken at 700 mb the influence from higher levels is intentionally suppressed by setting horizontal pressure gradients and frictional stresses to zero at the top of the layer horizontal convergence within the layer is taken up by cumulonimbus mass flux however the development of the cumulonimbus mass flux is associated with a short relaxation time o hr roughly the development time for such convection during this short time horizontal convergence acts to redistribute mass so as to reduce horizontal pressur

a semi geostrophic model incorporating well mixed boundary layers semi geostrophic theory has proved a powerful framework for understanding the dynamics of mid latitude weather systems however one limitation is the lack of a realistic boundary layer representation semi geostrophic theory can be modified to include an atmospheric boundary layer by replacing the geostrophic wind with the geotriptic or ekman balanced value in the substantive derivative and appropriately approximating the momentum diffusion term the so called semi geotriptic theory however until now solutions of the semi geotriptic equations using predictor corrector methods have not been possible for the important case of well mixed boundary layers existing predictor corrector methods require a brunt vaisala frequency greater than zero to be solvable here we describe a method of incorporating well mixed boundary layers into semi geotriptic theory we modify the hydrostatic relationship by including a small horizontal diffusion of vertical velocity this enables the formation of a well posed predictor corrector method given well mixed boundary layers are a ubiquitous feature of the lower atmosphere the modification increases the usability of the model calculations are also performed at much higher vertical resolution than before the revised semi geotriptic model is compared with a hydrostatic primitive equation model for a test case of a two dimensional idealized diurnal cycle of a sea breeze the performance of the revised semi geotriptic model in the growth phase of the sea breeze is improved as a well mixed boundary layer is now permitted the additional vertical resolution captures the capping inversion and the sea breeze circulation better the hydrostatic primitive equation model is shown to produce inertial oscillations that persist beyond the evening decay of the boundary layer until the following morning in contrast the semi geotriptic model decays following the boundary layer state in a more realistic way the semi geotriptic model thus demonstrates its usefulness as a critical tool in understanding boundary layer dynamics coupling issues in operational models copyright 2010 royal meteorological society and crown copyright

a partisan review of proterozoic anorthosites most anorthosites of the massif type crystallized in the episode 1 7 1 2 gyr with a pronounced peak of the age distribution near 1 4 gyr they were emplaced anorogenically at depths as shallow as 7 km where the ambient temperature of country rocks was probably less than 250 c depths of emplacement may have been as great as 25 km or more in rare cases the greater depths of equilibration estimated from granulite facies metamorphism may be incorrectly interpreted as emplacement depths but in any case they are demonstrably not required or characteristic of anorthosite emplacement penetrative deformation and metamorphism of anorthosites are post emplacement accidents of the local geologic history and are not directly caused by the presence of anorthosites granitic rocks mangerite charnockite suite associated with anorthosite are in general later or contemporaneous products of crustal anatexis with chemical and isotopic signatures distinct from the anorthosites and their residua such granitic rocks should not therefore be summed with the anorthositic rocks to obtain bulk compositions the magmas that produced most anorthosites were dry as shown by high temperature mineralogy and anhydrous mineral assemblages in contact aureoles residua from their crystallization are ferrodiorites to ferrosyenites typical of closed system fractionation these residua were locally and frequently ejected into contemporaneously molten granite where they formed pillows and cooled rapidly the overall chemistry of anorthosites and residua is broadly tholeiitic and consistent with derivation from the mantle olivine bearing magmas locally ranged from leucotroctolite anorthosite to later but coexisting picrite or melatroctolite in the same pluton confirming a wide spectrum of magma types a signal feature of troctolitic and noritic magmas is their low augite content implying high content of spinel component large anorthosite complexes such as nain and harp lake consist of many plutons representing repeated injections of separate magma batches with varying chemistry the abundant true anorthosites richer in plagioclase than magmas cosaturated with a mafic phase must represent plagioclase enrichment by either mechanical or chemical processes or both the role of kinetics in nucleation and solidification of such rocks may be centrally important it is proposed that hyperfeldspathic plagioclase supersaturated liquids were generated by quasi isothermal extraction of mafic minerals from tholeiitic magma enroute to and at the site of emplacement and that such a kinetic process was uniquely permitted in an environment of aborted continental rifting anorthositic rocks may have much to say about the episodic versus continuous geochemical evolution of the earth s mantle

mesoscale response to a meandering surface temperature interface abstract mesoscale variation of the boundary layer bl front produced by a surface temperature interface depends upon the scale of meander along that interface for a relatively large scale meander the circulations are quasi two dimensional relative to the local interface boundary and a meander signature appears in the bl structure for a relatively small scale meander alongfront blending eliminates organization about individual meanders to produce a quasi two dimensional circulation and gradients oriented perpendicular to the mean front the fundamental atmospheric scale controlling this transition is the mesoscale deformation radius which depends upon the warm side bl depth with strong large scale geostrophic forcing however the resulting alongfront advection length scale increases the meander size required to approach the large scale limit large scale meanders typically create two local maxima of vertical velocity whereas small scale meanders develop a single maximum on the warm side of the f

the atmospheric circulation over the north atlantic as induced by the sst field spectral analyses of the sea surface temperature sst in the simple ocean data analysis soda reanalysis for the past half century identify prominent and statistically significant interannual oscillations in two regions along the gulf stream front over the north atlantic a model of the atmospheric marine boundary layer coupled to a baroclinic quasigeostrophic model of the free atmosphere is then forced with thessthistoryfromthesodareanalysis twoextremestatesarefoundintheatmosphericsimulations 1 an eastward extensionofthe westerly jetassociatedwith thefront which occurs mainly during boreal winter and 2 a quiescent state of very weak flow found predominantly in the summer this vacillation of the oceanicfront induced jet in the model is found to exhibit periodicities similar to those identified in the observed gulf stream sstfront itself in addition a close correspondence is found between interannualspectralpeaksin the observed north atlantic oscillation nao index and the soda induced oscillations in the atmospheric model in particular significant oscillatory modes with periods of 8 5 4 2 and 2 8 yr are found in both observedandsimulatedindicesandareshowntobehighlysynchronizedandofsimilarenergyinbothtimeseries theseoscillatorymodesinthesimulationsareshowntobesuppressedwheneither i thegulfstream frontor ii its interannual oscillations are omitted from the sst field moreover these modes also disappear when iii the sst front is spatially smoothed thus confirming that they are indeed induced by the oceanic front

classification of mafic clasts from mesosiderites implications for endogenous igneous processes we have analyzed thirteen igneous pebbles from the vaca muerta eet87500 and bondoc mesosiderites by electron microprobe and instrumental neutron activation and combined these data with literature data for forty three analyzed mesosiderite clasts we classify these well characterized clasts into the following five principal groups 1 1 polygenic and monogenic cumulates 39 are coarse grained gabbros that are highly depleted in incompatible elements relative to h chondrites they formed at moderate depth either as residues of low degree partial melting of pre existing cumulate eucrites or as cumulates from parent melts similar to cumulate eucrites 2 2 polygenic basalts 30 are finer grained rocks with positive europium anomalies la lu ratios 1 and lower rare earth element abundances than basaltic eucrites it seems likely that these rocks were formed near their parent body surface by remelting mixtures of major amounts of basaltic eucrites and lesser amounts of cumulate eucrites 3 3 quench textured rocks comprise two compositional groups a those which resemble basaltic eucrites 5 and b those which resemble cumulate eucrites 2 the quench textured rocks are probably monogenic they formed most likely when small scale impacts at their parent body surface totally melted small amounts of basaltic or cumulate eucrite material 4 4 monogenic basalts 11 resemble basaltic eucrites and formed by endogenous igneous processes on the mesosiderite parent body mpb the monogenic basalts and those quench textured rocks that resemble basaltic eucrites in composition plot subparallel to the nuevo laredo trend eucrites on diagrams of incompatible element concentration vs mg previous work has shown that the nuevo laredo trend eucrites were probably produced by fractional crystallization it seems likely that the monogenic basalts from the mpb had a similar origin 5 5 ultramafic rocks are cumulates consisting mainly of large crystals of orthopyroxene 9 or olivine 4 orthopyroxenite clasts closely resemble diogenites and were formed most likely by endogenous igneous processes olivine crystals vary significantly in major element composition some may be endogenous but others may have been derived from the disrupted mantle of a different parent body

the influence of sea surface temperature on surface wind in the eastern equatorial pacific seasonal and interannual variability abstract the climate of the eastern pacific exhibits a pronounced equatorial asymmetry boundary layer air originating in the southern hemisphere trades crosses the equator and flows into the intertropical convergence zone itcz whose southern limit is nearly always located at least 4 to the north of the equator the sea surface temperature sst distribution is characterized by a prominent cold tongue centered 1 s a strong frontal zone centered 2 n and a warm eastward current centered near 5 n the surface wind field exhibits a pronounced horizontal divergence as the air flows northward across the oceanic frontal zone these features vary in strength in response to the annual cycle and the el nino southern oscillation phenomenon the northward cross equatorial surface winds the cold tongue and the frontal zone all tend to be strongest during the cold season july through november during the cold season of the coldest years when the cold tongue is most prominent the cross equatorial flow t

geochemistry and petrogenesis of the laramie anorthosite complex wyoming abstract a geochemical investigation of the laramie anorthosite complex determined that monsonite associated with the complex are characterized by positive eu anomalies and display a regular variation in composition with distance from the monzonite county rock contact anorthositic rocks have major and trace element abundance typical of similar complexes the internal variations in the monzonite were produced by in situ fractionation and contamination the data indicate that anorthosite and monzonite cannot be comagmatic it is proposed that the anorthosite and monzonite of the complex evolved from two distinct magmas and that two stages of anatectic melting contributed to the evolution of the monzonite an initial stage of partial melting was induced by intrusion of a gabbroic anorthosite magma into the lower crust a second partial melting event occurred after emplacement where heat from the intrusions melted country rocks resulting in extensive contamination ofthe monzonite

the response of the pacific storm track and atmospheric circulation to kuroshio extension variability an index of the kuroshio extension front strength is produced using a maximum covariance analysis between sea surface temperature sst and sea surface height ssh gradient observations and composites of the atmospheric state are presented during its positive and negative phases using reanalysis data 1992 2011 it is found that when the kuroshio extension is less more meandering with a stronger weaker sst front the atmospheric heat transport by transient eddies is increased in the western eastern pacific region consistent with an increase decrease in low level baroclinicity analysis of the eddy mean flow interaction shows that this zonal shift in heat transport forces anomalous barotropic flow in the eastern pacific where blocking frequency is strongly influenced the above relationships cannot be reconciled with the known response of the north pacific storm track to remote forcing from the tropical pacific nor can they be explained by the response of the ocean to atmospheric forcing via surface heat fluxes or winds rather the zonal shift in the storm track highlighted here and the associated changes in the large scale circulation are interpreted as a response to the interannual variability of the kuroshio extension front

storm track response to ocean fronts in a global high resolution climate model synoptic atmospheric eddies are affected by lower tropospheric air temperature gradients and by turbulent heat fluxes from the surface in this study we examine how ocean fronts affect these quantities and hence the storm tracks we focus on two midlatitude regions where ocean fronts lie close to the storm tracks the north west atlantic and the southern ocean an atmospheric climate model of reasonably high resolution 50 km is applied in a climate length 60 year simulation in order to obtain stable statistics simulations with frontal structure in the sea surface temperature sst in one of the regions are compared against simulations with globally smoothed sst we show that in both regions the ocean fronts have a strong influence on the transient eddy heat and moisture fluxes not just in the boundary layer but also in the free troposphere local differences in these quantities between the simulations reach 20 40 of the maximum values in the simulation with smoothed sst averaged over the entire region of the storm track over the ocean the corresponding differences are 10 20 the effect on the transient eddy meridional wind variance is strong in the boundary layer but relatively weak above that the potential mechanisms by which the ocean fronts influence the storm tracks are discussed and our results are compared against previous studies with regional models aquaplanet models and coarse resolution coupled models

extreme differentiation in the proterozoic gjerstad morkeheia complex of south norway the gjerstad morkeheia complex contains a series of highly differentiated iron and alkali enriched intrusions the rocks range from basic to acid compositions and were variably mylonitised under anhydrous conditions before being metamorphosed and hydrated at upper amphibolite facies grade they now form a series of ironenriched metagabbros metadiorites and granodioritic gneisses together with granitic and charnockitic augen gneisses the augen formed by shearing of original megacrysts in the igneous rocks a major mylonite zone formed at the same time

atmospheric response to a midlatitude sst front alongfront winds abstractsatellite observations and modeling studies show that midlatitude sst fronts influence the marine atmospheric boundary layer mabl and atmospheric circulation here the weather research and forecasting wrf mesoscale model is used to explore the atmospheric response to a midlatitude sst front in an idealized dry two dimensional configuration with a background wind oriented in the alongfront direction the sst front excites an alongfront wind anomaly in the free atmosphere with peak intensity just above the mabl this response is nearly quasigeostrophic in contrast to the inertia gravity wave response seen for cross front background winds the free atmosphere response increases with the background wind in contrast to previously proposed sst frontal mabl models the mabl winds are nearly in ekman balance however a cross front wind develops in the mabl as a result of friction and rotation such that the mabl cross front rossby number e 0 2 the mabl vorticity balance and scaling arguments

diagnostics for near surface wind response to the gulf stream in a regional atmospheric model abstractthe mechanisms acting on near surface winds over the gulf stream are diagnosed using 5 yr outputs of a regional atmospheric model the diagnostics for the surface layer momentum vector its curl and its convergence are developed with a clear separation of pressure adjustment from downward momentum inputs from aloft in the surface layer system the results suggest that the downward momentum mixing mechanism plays a dominant role in contributing to the annual mean climatological momentum curl whereas the pressure adjustment mechanism plays a minor role in contrast the wind convergence is mainly due to the pressure adjustment mechanism this can be explained by the orientation of background wind to the sea surface temperature front the diagnostics also explain the relatively strong seasonal variation in surface layer momentum convergence and the small seasonal variation in curl finally the surface layer response to other western boundary currents is examined using a reanalysis dataset

causes of river bed degradation river bed degradation can proceed downstream as well as upstream depending upon the cause of degradation the causes of downstream progressing degradation are primarily related to changes in independent river channel variables such as increase in water discharge decrease in size of bed material and decrease in bed material discharge the causes of upstream progressing degradation are all related to an imposed increase in river slope which can occur as a result of natural river behavior or by man made changes study of various case histories indicates that river slopes are increased by lowering a base level by decreasing the length of a river or by removal of a control point case histories also show that downstream and upstream progressing degradation can act in combination along a river system downstream progressing degradation along the main stream of a river system can initiate upstream progressing degradation on a tributary

high resolution satellite measurements of the atmospheric boundary layer response to sst variations along the agulhas return current abstract the marine atmospheric boundary layer mabl response to sea surface temperature sst perturbations with wavelengths shorter than 30 longitude by 10 latitude along the agulhas return current arc is described from the first year of sst and cloud liquid water clw measurements from the advanced microwave scanning radiometer amsr on the earth observing system eos aqua satellite and surface wind stress measurements from the quikscat scatterometer amsr measurements of sst at a resolution of 58 km considerably improves upon a previous analysis that used the reynolds sst analyses which underestimate the short scale sst gradient magnitude over the arc region by more than a factor of 5 the amsr sst data thus provide the first quantitatively accurate depiction of the sst induced mabl response along the arc warm cold sst perturbations produce positive negative wind stress magnitude perturbations leading to short scale perturbations in the wind stress curl and divergence fields that are li

atmospheric response to mesoscale sea surface temperature anomalies assessment of mechanisms and coupling strength in a high resolution coupled model over the south atlantic many aspects of the coupling between the ocean and atmosphere at the mesoscale on the order of 20 100 km remain unknown while recent observations from the southern ocean revealed that circular fronts associated with oceanic mesoscale eddies leave a distinct imprint on the overlying wind cloud coverage and rain the mechanisms responsible for explaining these atmospheric changes are not well established here the atmospheric response above mesoscale ocean eddies is investigated utilizing a newly developed coupled atmosphere ocean regional model consortium for small scale modeling regional ocean modelling system cosmo roms configured at a horizontal resolution of 10 km for the south atlantic and run for a 3 month period during austral winter of 2004 the model simulated changes in surface wind cloud fraction and rain above the oceanic eddies are very consistent with the relationships inferred from satellite observations for the same region and time from diagnosing the model s momentum balance it is shown that the atmospheric imprint of the oceanic eddies are driven by the modification of vertical mixing in the atmospheric boundary layer rather than secondary flows driven by horizontal pressure gradients this is largely due to the very limited ability of the atmosphere to adjust its temperature over the time scale it takes for an air parcel to pass over these mesoscale oceanic features this results in locally enhanced vertical gradients between the ocean surface and the overlying air and thus a rapid change in turbulent mixing in the atmospheric boundary layer and an associated change in the vertical momentum flux

atmospheric response to sea surface temperature mesoscale structures recent studies have revealed that strong sea surface temperature sst fronts on the scale of a western boundary current significantly affect not just the marine boundary layer but the entire troposphere this has aroused renewed interest in air sea interactions the present study investigates the atmospheric response to fixed sst anomalies associated with mesoscale oceanic eddies and submesoscale filaments using idealized simulations our main result is that in weak wind conditions the vertical velocity in the planetary boundary layer pbl is linearly proportional to the sst laplacian this is established by a quantitative analysis in the spatial space as well as in the spectral space comparing the responses to two different sst fields shows that vertical velocities are much more intense when the submesoscales are more energetic these results hold for different configurations of the atmospheric large scale state and for different pbl parameterizations surface winds play the role of low pass filter and reduce the response at the smaller scales to our knowledge this study is the first to clearly reveal the high impact of oceanic submesoscales on the atmospheric boundary layer at midlatitudes as well as the direct link between the vertical velocity and the sst laplacian

balanced models of boundary layer convergence in the tropics positive sea surface temperature anomalies are often coupled to the well mixed boundary layer the boundary layer then typically forces convergence and ascent the ascent can trigger moist convection established diagnostic models of boundary layer convergence employ the steady state ekman geotriptic balance here we extend the steady state balance to include non stationarity within an idealised one dimensional shallow water framework we identify three time varying balanced models planetary geotriptic pgt and semi geotriptic sgt a and sgt b these models are verified against the shallow water swe model the pgt model has prognostic mass and diagnostic momentum whereas the sgt models also include prognostic momentum the sgt models have separate ekman balanced and advecting winds the friction term in the sgt a model is a function of twice the balanced wind minus the advecting wind we show that the sgt a model has stable solutions in time and is between first and second order accurate in contrast the sgt b model s friction is a function of just the advecting wind although second order accurate the sgt b is also unstable and thus unusable for cases of significant nonlinear advection the sgt a model predicts more accurate convergence than the pgt model however the sgt a model has a less accurate geopotential field than the pgt model after a period the swe model breaks down into near grid scale gravity waves and the solutions are no longer numerically reliable the sgt a and pgt models then maintain a smooth solution with the gravity waves filtered out and thus give a more robust evolution in convergence for cases of diurnal forcing with a fast frictional time scale the sgt a model follows the growth phase of the swe model more closely than the pgt model copyright 2012 royal meteorological society and british crown copyright the met office

global analysis of the pressure adjustment mechanism over sea surface temperature fronts using airs aqua data 1 we investigate the signatures of atmospheric pressure adjustment mechanism for surface wind convergence divergence over major sea surface temperature sst frontal regions using global observations of satellite sounding and scatterometer lower tropospheric air thickness which includes a sea level pressure component modified by air temperature in the marine atmospheric boundary layer is analyzed and the relation between the laplacian of the thickness and wind convergence are examined among four sst frontal regions in mid latitudes correlation between the thickness laplacian and wind convergence is the largest over the gulf stream followed by those for the agulhas return current and for the brazil malvinas current and relatively small but still significant over the kuroshio oyashio extension these correlations strongly suggest that the pressure adjustment mechanism ubiquitously plays an important role in air sea interaction over the global sst frontal regions furthermore air temperatures in the first two regions exhibit sst relating signatures even in the mid troposphere

covariations of sea surface temperature and wind over the kuroshio and its extension evidence for ocean to atmosphere feedback abstract satellite microwave measurements are analyzed revealing robust covariability in sea surface temperature sst and wind speed over the kuroshio extension ke east of japan ocean hydrodynamic instabilities cause the ke to meander and result in large sst variations increased reduced wind speeds are found to be associated with warm cold sst anomalies this positive sst wind correlation in ke is confirmed by in situ buoy measurements and is consistent with a vertical shear adjustment mechanism namely an increase in sst reduces the static stability of the near surface atmosphere intensifying the vertical turbulence mixing and bringing fast moving air from aloft to the sea surface south of japan the kuroshio is known to vary between nearshore and offshore paths these paths are very persistent and can last for months to years as the kuroshio shifts its path coherent wind changes are detected from satellite data in particular winds are high south of tokyo when the kuroshio takes the near

changes in the magnitude and transformation of flood waves subsequent to the channelization of the raba river polish carpathians alterations in flood flows of the raba river are examined to determine the influence exerted on flood waves by changing morphological conditions with stable vertical channel position the river increased its sinuosity during the 1920s to 1940s and the change was accompanied by a growing tendency to flood wave attenuation the temporal change in flood wave transformation is typical of a developing low flow system subsequently streambed degradation has been induced due to channnelization works which straightened and narrowed the river flood waves became progressively more flashy as channel incision progressed the increase in magnitude of flood waves passing the deepened reach was greatest for bankfull flows and diminished for lower in bank flows and higher overbank flows the tendency to magnification of peak discharges has been also found in other carpathian rivers which were considerably degraded in the 20th century in response to channelization introducing an empirically found correcting factor into the analysis of the ratio of outflow to inflow peak discharges shows how the conditions of peak flow transformation in a reach have changed since the beginning of the study period a marked coincidence between changes in vertical channel location and variations in the corrected peak discharge ratio proves channel changes to be a very important reason for the growing flood hazard in southern poland gradient oversteepening and channel narrowing caused by channelization lead to formation of a river system having a steep straight narrow and deep channel such a morphology distinguishes the system from natural low flow and high flow systems reduced floodplain water storage and self acceleration of flow concentrated in a channel zone make flood waves progressively more flashy on their way down the channelization formed system

petrogenesis of mesoproterozoic oak creek and west mccoy gulch plutons colorado an example of cumulate unmixing of a mid crustal two mica granite anorogenic affinity abstract the 1 44 ga old oak creek batholith is a composite suite of foliated granitoid intrusions consisting of two main facies 1 a porphyritic facies ranging from quartz monzonite to monzogranite and 2 a medium grained leucogranite the porphyritic facies comprises most of the batholith and is distinctly rich in feldspar the medium grained facies is more silica rich and it occurs as small irregular bodies within the porphyritic facies occurring 20 km to the west the west mccoy gulch stock is a 1 46 ga unfoliated pluton that is similar to the medium grained facies at oak creek based on several independent thermobarometers the batholith is estimated to have been emplaced at 11 to 14 km 3 to 4 kbar near liquidus temperatures were at 880 60 c and for more evolved members solidus temperatures were 650 20 c the estimated oxygen fugacity at 2 log units above qfm is typical of other magnetite series granites compared to most granites these granites contain high fe mg ratios high k and ree concentration and low mg and ca concentrations the least differentiated portions of the medium grained facies at oak creek and the west mccoy gulch pluton could have formed by 20 30 aggregate melting of calc alkaline tonalite to granodiorite other models including derivation from melt depleted granulite are precluded the porphyritic facies at oak creek has large variations in elements that concentrate both in mafic minerals fe mg ti cr and sc and feldspars ba sr and these elements from fairly linear plots in harker diagrams element modeling combined with the field evidence suggests that this unit formed by variable unmixing of magmatic cumulate crystals and evolving liquid the medium grained facies is interpreted as being a more evolved melt derived from the crystal rich porphyritic facies the west mccoy gulch pluton could have formed in a similar manner to the medium grained facies by crystal fractionation from a non exposed parent cumulate evolved melt unmixing may be a predominately mid crustal phenomenon most a type granites are homogeneous shallow intrusions but may represent fractionated liquids derived from crystal rich fractions such as that exposed in the oak creek batholith

on the importance of midlatitude oceanic frontal zones for the mean state and dominant variability in the tropospheric circulation 1 observations indicate that midlatitude weather systems are organized into storm tracks near oceanic frontal zones with pronounced sea surface temperature sst gradients a pair of atmospheric general circulation model experiments with zonally uniform sst profiles prescribed show that their observed collocation is not fortuitous in one experiment a storm track is anchored around a midlatitude sst front that maintains near surface thermal gradients and energizes eddies westerly momentum transport by eddies produces a well defined polar front jet along the front even in winter when a subtropical jet stream intensifies in the other experiment removal of the sst front leads to a substantial weakening in eddy activity and the pfj especially in winter it also leads to a weakening of the annular mode the dominant mode of westerly jet variability and its notable structural distortion in winter though idealized our experiments suggest the importance of midlatitude oceanic fronts for the tropospheric circulation and its variability

two types of surface wind response to the east china sea kuroshio front abstracteffects of the sea surface temperature sst front along the east china sea kuroshio on sea surface winds at different time scales are investigated in winter and spring the climatological vector wind is strongest on the sst front while the scalar wind speed reaches a maximum on the warm flank of the front and is collocated with the maximum difference between sea surface temperature and surface air temperature sst sat the distinction is due to the change in relative importance of two physical processes of sst wind interaction at different time scales the sst front induced sea surface level pressure slp adjustment sf slp contributes to a strong vector wind above the front on long time scales consistent with the collocation of baroclinicity in the marine boundary layer and corroborated by the similarity between the thermal wind and observed wind shear between 1000 and 850 hpa in contrast the sst modulation of synoptic winds is more evident on the warm flank of the sst front large ther

bed level adjustments in the arno river central italy abstract two distinct phases of bed level adjustment over the last 150 years are identified for the principal alluvial reaches of the arno river upper valdarno and lower valdarno the planimetric configuration of the river in these reaches is the result of a series of hydraulic works canalization rectification artificial cut offs etc carried out particularly between the 18th and the 19th centuries subsequently a series of interventions at basin level construction of weirs variations in land use intense instream gravel mining after world war ii and the construction of two dams on the arno river caused widespread degradation of the streambed since about 1900 total lowering of the channel bed is typically between 2 and 4 m in the upper valdarno reach and between 5 and 8 m in some areas of the lower valdarno reach bed level adjustments with time are analyzed for a large number of cross sections and described by an exponential decay function this analysis identified the existence of two main phases of lowering the first triggered at the end of the past century the second triggered in the interval 1945 1960 and characterized by more intense degradation of the streambed the first phase derived from changes in land use and land management practices the second phase is the result of the superimposition of two factors intense instream mining of gravel and the construction of the levane and la penna dams

observations of coupling between surface wind stress and sea surface temperature in the eastern tropical pacific satellite measurements of surface wind stress from the quikscat scatterometer and sea surface temperature sst from the tropical rainfall measuring mission microwave imager are analyzed for the three month period 21 july 20 october 1999 to investigate ocean atmosphere coupling in the eastern tropical pacific oceanic tropical instability waves tiws with periods of 20 40 days and wavelengths of 1000 2000 km perturb the sst fronts that bracket both sides of the equatorial cold tongue which is centered near 1 8s to the east of 1308w these perturbations are characterized by cusp shaped features that propagate systematically westward on both sides of the equator the space time structures of these sst perturbations are reproduced with remarkable detail in the surface wind stress field the wind stress divergence is shown to be linearly related to the downwind component of the sst gradient with a response on the south side of the cold tongue that is about twice that on the north side the wind stress curl is linearly related to the crosswind component of the sst gradient with a response that is approximately half that of the wind stress divergence response to the downwind sst gradient the perturbed sst and wind stress fields propagate synchronously westward with the tiws this close coupling between sst and wind stress supports the wallace et al hypothesis that surface winds vary in response to sst modification of atmospheric boundary layer stability