seasonal changes in the hydrological and erosional response of a hillslope under dry mediterranean climatic conditions montes de malaga south of spain the mediterranean eco geomorphological system was analysed at one representative hillslope of the geological unit of montes de malaga province of malaga spain under dry mediterranean climatic conditions the research was divided into two stages first the eco geomorphological pattern of the slope and some physical properties of the soil were analysed second the hydrological and erosional response of the eco geomorphological system was analysed by applying simulated rainfall to the main elements of the system and using closed plots with different lengths this hydrodynamic analysis was carried out during two periods crucial for the mediterranean environment in hydrological terms the end of the dry season or the beginning of the active hydrodynamic season and the middle of the wet season the results show that i the hydrophobic behaviour of soil is the predominant runoff generation mechanism that accounts for sediment movement ii once soil was moistened in the wet season it lost its hydrophobicity and the saturation of soil became a predominant runoff generation mechanism and iii there was high variability in hillslope runoff with evident hydrological disconnections which made the hydrodynamic response of the eco geomorphological system complex due to the absence of a clear predominance of abiotic or biotic factors

upscale impact of mesoscale disturbances of tropical convection on 2 day waves abstractwestward propagating 2 day waves with embedded mesoscale disturbances contribute a large portion of synoptic variability of tropical convection over the western pacific it is of crucial im

circulation anomalies associated with tropical convection during northern winter abstract lagged cross correlations between outgoing longwave radiation olr and national meteorological center global analyses are utilized to isolate the preferred upper level and surface circulation anomalies associated with tropical convection during northern winter three intraseasonal time scales are studied 30 70 14 30 and 6 14 days in the 30 70 day band the upper level circulation signals are zonally elongated with zonal wavenumbers 0 2 dominant higher frequency signals are dominated by zonal wavenumbers 5 and 6 in the 14 30 day band convection over the eastern hemisphere is associated with upper level anticyclones in the subtropics and appears to be linked in some cases to midlatitude wave trains the strongest signals are for convection over africa australia and the eastern indian ocean only weak signals are seen for convection over indonesia in these regions of upper level easterlies olr anomalies peak prior to the maximum anomalies in wind suggesting forcing of the circulation b

geochemical alteration of pyrochlore group minerals pyrochlore subgroup primary alteration of uranpyrochlore from granitic pegmatites is characterized by the substitutions adyd acayo anayf acayo and anayoi i acayo alteration occurred at 450 650 c and 2 4 kbar with fluid phase compositions characterized by relatively low ana high aeah and high ph in contrast primary alteration of pyrochlore from nepheline syenites and carbonatites follows a different tre nd represented by the substitutions anayf adydand acayo adyd in carbonatites primary alteration of pyrochlore probably took place during and after replacement of diopside forsterite calcite by tremolite dolomite t ankerite at 300 550 c and 0 2 kbar under conditions of relatively low ahf low ana low aeah low ph and elevated activities of fe and sr microscopic observations suggest that some altered pyrochlor1es are transitional between primary and secondary alteration alteration paths for these specimens scatter around the trend anayf adyd alteration probably occurred at 200 350 c in the presence of a fluid phase similar in composition to the fluid present during primary alteration but with elevated activities of ba and rees mineral reactions in the system na ca fe nb o h indicate that replacement of pyrochlore by fersmite and columbite occurred at similar conditions with fluid conpositions having relatively low ana moderate aeah and moderate to high afeh secondary alteration 150 c is charactlerizedby the substitutions anayf adyd acayo adyd and acaxo adxdtogether with moderate to extreme hydration 10 15 wt h20 or 2 3 molecules per formula unit minor variations in the amounts of mg ai k mn fe sr ba and rees are commonly observed as a result of secondary alteration major cation exchange for k sr and ba is a feature of samples from laterite horizons overlying carbonatites in most cases u th and b site cations remain relatively constant radiogenic pb is typically lost via long te rm diffusion but in some grains of uranpyrochlore 25 90 of the pb is lost as a result of alteration

nari calcrete outcrop contribution to ancient agricultural terraces in the southern shephelah israel insights from digital terrain analysis and a geoarchaeological field survey a field survey revealed that byzantine and early arab ca 5th to 8th century c e agricultural systems in the semi arid region of the shephelah central israel were similar to runoff agricultural systems in the arid region of the negev southern israel this similarity led to the hypothesis that systems in the shephelah also function as runoff farms this hypothesis is not trivial since runoff values in semi arid regions are generally low due to intensive but short rainfall events and due to the presence of sink patches that absorb runoff on slope surface the aim of the current research is to examine whether runoff potential in a representative agricultural system in the shephelah is sufficient for sustaining runoff farming a geoarchaeological field survey and digital terrain analysis show that large nari calcrete outcrops on the footslopes generate high runoff values that improve water potential hydrological simulations and calculations show that 230 mm of direct rainfall generates a water potential equivalent to 300 mm of direct rainfall in view of these results it is reasonable to conclude that the presence of nari enabled runoff agricultural farming in the shephelah region even in drought years

human impacts on fluvial systems in the mediterranean region the long history of substantial human impacts on the landscape of the mediterranean region and their effects on fluvial systems is documented these effects have included impacts of deforestation and other land use changes agricultural terracing on a wide scale water transfers and irrigation schemes during the 20th century major changes were made directly to channels through channelisation construction of dams of various sizes and extraction of gravel and indirectly by reforestation these changes have caused a major phase of incision on some rivers runoff and soil erosion have been affected by types of crops and agricultural practices as well as by the varying extent of cultivation and grazing some recent agricultural practices involve wholescale relandscaping of the topography and alteration of surface properties of material the importance of analysing the connectivity within different land units and of the spatial position of human activity within a catchment is illustrated the analysis of connectivity is the key to understanding the variability of impact and the extent of propagation of effects

effects of soil and vegetation on runoff along a catena in semi arid spain runoff and infiltration were investigated on abandoned fields of patchy vegetation in semi arid spain during 15 months of natural rainfall and by rainfall simulations the aim was to ascertain sources and sinks of runoff and the effects of soils and plant cover soils of the catena developed from mica schists of the upper hillslopes fan deposits of the lower hillslopes and an alluvial terrace at the bottom runoff from natural events were from three sets of three pairs each of 10 2 m runoff plots the pairs of each set had different densities of plant cover the sets were vegetated with tussock grass stipa tenacissima a shrub anthyllis cytisoides and a bush retama sphaerocarpa nineteen natural rainfall events of intensities up to 18 mm h produced 400 mm of rain during the study period because the rainfall threshold for runoff production was about 20 mm only eight events produced runoff the rainfall simulations used a sprinkler that produced 50 mm h of rain for 30 minutes runoff was recorded each minute in 0 24 m2 bounded plots the depth and structure of the soil mantle provide the main controls on runoff rates which are lowest on the lower fan deposits and highest on the thin upslope soils the river bank terrace with a surface covered by crusts and mosses also yields relatively high runoff in general vegetation density varies inversely with runoff nevertheless shrub and bush litter favor runoff as does a particular spatial distribution of individual plants on the hillslope settling of the upper few centimeters of soils of the alluvial fan following cessation of cultivation 15 to 40 years ago has produced a near surface compacted layer favoring shallow subsurface runoff apparently contradictory results between runoff plots and rainfall simulations are the result of differing processes

mineralogy geochemistry and ore genesis of kanawa uranium mineralization hawal massif eastern nigeria terrane implications for uranium prospecting in nigeria and cameroon abstract the kanawa area eastern nigeria terrane ent located proximal to pan african shear zone has u prospects with an average u concentration of 0 1 wt samples taken from the fault breccia mylonite cataclasite and ore zone show increasing u contents of 2 2 6 7 ppm 4 7 ppm 36 253 ppm and 165 1000 ppm respectively u pb dating of magmatic zircons from the granite hosting the u prospect yield 206pb 238u concordia age of 603 5 9 ma suggesting pan african ediacaran age for the host granite in contrast zircon grains from the u ore zone yield 206pb 238u concordia age of 228 2 ma considered here as the estimated age of u mineralization an interpretation that need to be supported by additional data the pan african granite hosting kanawa u mineralization has very low u content u 1 0 6 7 ppm and therefore could not have been the main source of the u mineralization considering that the kanawa u ore zone shows broadly similar geochemical signature and yield roughly similar age with its spatially associated mesozoic rocks in area we suggest that the u mineralization was probably sourced from the mesozoic volcanics rocks uranium zr v may have been leached out from the mesozoic volcanic by hydrothermal fluid circulating along the channel ways provided by pan african wrench fault taken together our combined major and trace element data in conjunction with previously reported data of u mineralization from western cameroon allow us re evaluate the geochemical signatures of pan african granite hosting u mineralization in these regions and reassess their u potential in relation to some well known u deposits elsewhere in the world it is noteworthy that the kanawa u mineralization shows broadly similar geochemical features with the volcanic related streltsovskoye antei u deposit transbaikalia russia the highly evolved ekomedion granites in cameroon have high u and f content and exhibit geochemical features typical of u fertile granite suggesting that u mineralization ekomedion area was probably sourced from the granites in contrast pan african granites from kitongo have low u and f content and may not have been the primary source of the kitongo u mineralization as suggested for kanawa u mineralization the kitongo u mineralization was probably sourced from the mesozoic rocks in the area these chains of mesozoic volcanic and plutonic suites largely emplaced within pan african mega shear zones extend from nigeria into cameroon and niger and could be linked to other mega shear zones in egypt and saudi arabia where similar u mineralization have been reported this study therefore allows for an initial correlation of u occurrences and provides a framework for further regional investigation

observation of a quasi 2 day wave during toga coare abstract detailed structure of the quasi 2 day oscillation observed in the active phase of the madden julian oscillations during the intensive observation period of tropical ocean and global atmosphere coupled ocean atmosphere response experiment toga coare iop was described a variety of observational platforms is used including high resolution gms infrared histogram rain rate estimate from toga and mit radar measurements upper air soundings and boundary layer profiler winds from the integrated sounding system and surface data from the imet buoy the quasi 2 day mode had a westward propagation speed of 12 15 day 1 a horizontal wavelength of 25 30 longitude a coupling with the westward propagating n 1 inertio gravity waves was hypothesized from the space time power spectral distribution of the cloud field the wind disturbance structure was consistent with the hypothesis the vertical wave structure had an eastward phase tilt with height below 175 hpa and vice versa above indicating the wav

a model for the origin of the alkaline complexes of egypt the alkaline complexes in the nubian shield of egypt range in age from 554 to 89 myr bp refs 1 3 and where data are available have similar and primitive initial strontium ratios of 87sr 86sr ref 1 these intrusive complexes are similar with respect to petrography major element chemistry rare earth element distribution and other trace element distribution1 4 7 they are intimately associated with major lineaments in the nubian shield fig 1 8 it is likely that all of them had a similar origin not directly related to rifting and or doming we suggest here that the origin of these complexes is due to alkaline melts having been formed in the asthenosphere by shear heating caused by changes in plate motion these melts were emplaced along reactivated pan african fractures or pre existing zones of weakness

lateral moisture flow beneath a sandy hillslope without an apparent impeding layer part of a small drainage basin on the sevilleta national wildlife refuge about 25 km north of socorro nm was intensively instrumented with soil monitoring equipment to estimate natural ground water recharge soil moisture data were analysed with special attention to characterizing the influence of topography on the direction of vadose water flow paths in fine to medium aeolian sand moisture content data were obtained by the neutron scattering technique and hydraulic head data were obtained using tensiometers in addition tracer experiments were conducted on a sandy hillslope to delineate the flow paths of vadose water the results indicate that there is a strong lateral component to unsaturated flow on a hillslope even in the absence of apparent sublayers of much lower permeability darcian calculations estimate the long term steady deep flux beneath a concave location to be about 4 per cent of an assumed mean annual precipitation of 20 cm the deep soil water flux downward varied by several orders of magnitude during the 17 month period of record

tropical convection on 7 21 day timescales over the western pacific abstract evidence is presented to demonstrate that the oscillations of convection on 7 21 day timescales are an important component of the intraseasonal variability over the region spanning the equatorial western pacific to the subtropical south pacific in that area of the world these oscillations are largely confined to regions with high sea surface temperatures ssts or sst gradients consequently the patterns of 7 21 day variability of convection undergo significant changes as the el nin o southern oscillation reconfigures the distributions of sst a test is developed that detects episodes in which the 7 21 day oscillation of outgoing longwave radiation olr is particularly well defined for several cycles applying this test 29 episodes of high 7 21 day variability were defined based on this information the annual and longitudinal distribution of 7 21 day variability is discussed the 7 21 day oscillations of convection found at subtropical southern latitudes tend to have stronger wind shear i

the mobility of zirconium and other immobile elements during hydrothermal alteration abstract development of zircon and other zr phases in hydrothermal deposits indicates that zr can be highly mobile in these systems mobility is most common in but not restricted to f rich hydrothermal systems related to alkalic f rich igneous suites these suites can range from peralkaline through metaluminous to peraluminous a few examples are neither alkalic nor f rich three locations in the trans pecos magmatic province texas u s a demonstrate this hydrothermal zr mobility all three igneous systems are alkalic and f rich but vary in alkali al ratios peralkaline rhyolites and trachytes in the christmas mountains contain as much as 2100 ppm zr mostly in aegirine or arfvedsonite zircon is rare or absent fluorspar replacement deposits in limestone at contacts with the rhyolites contain as much as 38 000 ppm zr occurring as small disseminated zircons the deposits also are enriched in a variety of incompatible elements including be rare earth elements ree y nb mo hf pb th and u the sierra blanca intrusions a series of mildly peraluminous f rich rhyolite laccoliths contain as much as 1000 ppm zr mostly as zircon hydrothermal zircon occurs as overgrowths on magmatic grains as veinlets connected to overgrowths and in fluorspar replacement bodies in adjacent limestone the highest zr concentrations in fluorspar are 200 ppm metaluminous quartz monzonite from the infiernito caldera contains 400 600 ppm zr mostly as zircon euhedral zircon in quartz fluorite veins in the quartz monzonite indicates mobility of zr zirconium concentrations in the veins are unknown but the paucity of zircon suggests little zr enrichment relative to the host zircon and more rarely zirconolite occur in skarn in the ertsberg district of irian jaya indonesia unlike in texas related igneous rocks are metaluminous and the hydrothermal system was f poor worldwide hydrothermal zircon other zr phases and ti and al bearing phases occur in skarn epithermal precious metal veins volcanogenic massive sulfide deposits and mylonites we propose that differences in zr mineralogy of igneous source rocks is an important factor in determining the availability of zr to hydrothermal fluids although zr concentrations in the sierra blanca and christmas mountains rhyolites are similar zr enrichment in fluorspar was much greater in the christmas mountains we suggest that hydrothermal solutions could easily break down aegirine and arfvedsonite to release zr but that zircon was only moderately attacked therefore far more zr was available for transport and subsequent deposition in the christmas mountains than at sierra blanca availability of other trace elements probably is also governed by their mineral host although zr mobility is most common in f rich hydrothermal systems related to alkalic and f rich igneous systems mobility at ertsberg may have been promoted by sulfate complexing

ecogeomorphology in the australian drylands and the role of biota in mediating the effects of climate change on landscape processes and evolution

linking spatial patterns of soil organic carbon to topography a case study from south eastern spain a key uncertainty in our understanding of the global carbon cycle is the lateral movement of carbon through the terrestrial system soils are the major storage of carbon in the terrestrial biosphere and the inventory of soil organic carbon soc is required for greenhouse gas inventories and carbon mitigation projects the aim of this study is to characterize spatial patterns of the concentrations of topsoil total organic carbon toc in a semi arid mediterranean area in south eastern spain and to assess their relationship to topography we adopt a remote sensing based approach for the spectral determination and quantification of toc with a complete coverage of bare soil surfaces digital terrain analysis and geostatistical techniques are applied to analyze the spatial patterns of toc at different spatial scales we show that accumulation of topsoil soc is dependent on topographic position at the landscape scale with highest values found in valley bottoms at the hill slope scale differences among terrain classes exist regarding the topographic controls on soc while positive correlation between the topographic wetness index twi and toc can be observed on steep slopes that correlation is not significant on wide pediments small scale spatial variability is large on ridges steep slopes and valley bottoms while soc distribution on pediments is relatively homogeneous these differences are most likely governed by the presence of vegetation patches and variable runoff and sediment transport rates among the terrain classes the successful application of hyperspectral remote sensing for the spatial estimation of soc concentrations suggests that it is a promising technique to advance soc inventories in semi arid and arid regions

u series age and origin of two secondary uranium deposits central eastern desert egypt at two sites in the central eastern desert of egypt secondary uranium minerals are found at the surfaces of tabular fractured rock bodies which host primary uranium mineralization at depth at el atshan the host rock is a 28 m thick bostonite sill cutting siltstones and at el erediya the host rock is a 20 cm jasperoid vein cutting granite whereas the primary mineralization at depth is pre tertiary we obtain u series ages for the secondary mineralization at both sites of 80 000 to 140 000 yr we interpret this episode of uranium mobilization to have resulted from ground water saturation during humid oxygen isotope climatic stage 5 at both sites adsorbed uranium in the host rock immediately below the secondary ores is shown to have been the result of subsequent mobilization during the last 60 000 yr

structure and characteristics of submonthly scale waves along the indian ocean itcz this study examines wave disturbances on submonthly 6 30 day timescales over the tropical indian ocean during southern hemisphere summer using japanese reanalysis jra25 jcdas products and national oceanic and atmospheric administration outgoing longwave radiation data the analysis period is december february for the 29 years from 1979 1980 through 2007 2008 an extended empirical orthogonal function eeof analysis of daily 850 hpa meridional wind anomalies reveals a well organized wave train pattern as a dominant mode of variability over the tropical indian ocean daily lagged composite analyses for various atmospheric variables based on the eeof result show the structure and evolution of a wave train consisting of meridionally elongated troughs and ridges along the indian ocean intertropical convergence zone itcz the wave train is oriented in a northeast southwest direction from sumatra toward madagascar the waves have zonal wavelengths of about 3 000 5 000 km and exhibit westward and southwestward phase propagation individual troughs and ridges as part of the wave train sequentially travel westward and southwestward from the west of sumatra into madagascar meanwhile eastward and northeastward amplification of the wave train occurs associated with the successive growth of new troughs and ridges over the equatorial eastern indian ocean this could be induced by eastward and northeastward wave energy dispersion from the southwestern to eastern indian ocean along the mean monsoon westerly flow in addition the waves modulate the itcz convection correlation statistics show the average behavior of the wave disturbances over the tropical indian ocean these statistics and other diagnostic measures are used to characterize the waves obtained from the composite analysis the waves appear to be connected to the monsoon westerly flow the waves tend to propagate through a band of the large meridional gradient of absolute vorticity produced by the mean monsoon westerly flow this suggests that the monsoon westerly flow provides favorable background conditions for the propagation and maintenance of the waves and acts as a waveguide over the tropical indian ocean the horizontal structure of the wave train may be interpreted as that of a mixture of equatorial rossby waves and mixed rossby gravity wavelike gyres

two phases of cretaceous tertiary magmatism in the eastern desert of egypt paleomagnetic chemical and k ar evidence abstract paleomagnetic and radiometric data confirm the existence of two phases of igneous activity in the late mesozoic and cenozoic history of eastern egypt in the mid to late cretaceous the earlier and more extensive episode produced the wadi natash alkaline basalts and numerous small trachytic intrusions the ring complexes of abu khrug and gebel el kahfa were also emplaced at this time the mean paleopole position for the intrusive rocks is at 65 3 n 111 2 w a 95 11 4 31 sites chemical analyses of the trachytes show that they are enriched in nb zr and y and depleted in sr ba cr and ni suggesting either prolonged fractionation or limited partial fusion the second phase of activity during oligo miocene time is represented by small tholeiitic basalt flows on the red sea coast and along the nile valley the mean paleopole position for the flows is at 68 2 n 101 5 e a 95 27 8 3 sites the wide scatter is interpreted as reflecting secular variation the chronological and chemical data are used with studies of sedimentary formations coeval with the igneous rocks to apply a general model of continental rifting to the northern red sea the earlier alkaline phase of igneous activity is related to regional uplift while the second tholeiitic phase is associated with widening of the rift valley

upper crustal fluids in a large fault system microstructural trace element and oxygen isotope study on multi phase vein quartz at the bavarian pfahl se germany fault systems are zones of crustal weakness and are used as pathways for ascending hydrothermal fluids one impressive example is the more than 150 km long bavarian pfahl system at the sw boundary of the bohemian massif dextral ductile shearing of moldanubian basement has shaped a several hundred meter wide zone of mylonites and ultramylonites this setting was reactivated under brittle conditions and infiltrated by fluids resulting in a multi phase quartz lode structural analysis using scanning electron microscopy cathodoluminescence sem cl images has been carried out in combination with trace element and oxygen isotope analysis on quartz along the system three successive quartz phases have been distinguished due to their structural details and trace element contents cryptocrystalline quartz fabric in the first quartz phase results from crystallization from a silica gel whereas in phases ii and iii quartz precipitation is characterized by repeated fragmentation and sealing visible due to strongly varying cl intensities the 18o of bavarian pfahl quartz decreases from 13 8 in the nw to 8 5 in the se whereas quartz from the close by situated wolsendorf fluorite deposit shows 18o between 15 9 and 18 5 vs smow flat shale normalized rare earth element patterns point towards an upper crustal origin of the hydrothermal fluids the southeastern part of the bavarian pfahl is interpreted to represent a deeper crustal level with higher mineralization temperatures about 350 c compared to the rest of the pfahl 250 c

persistent north pacific circulation anomalies and the tropical intraseasonal oscillation abstract a composite analysis of multiyear 1985 93 global reanalyses produced by the ncep ncar and the nasa dao is used to show that the development of persistent north pacific pnp circulation anomalies during nh winter is linked to tropical intraseasonal oscillations the development is initiated over the tropical west pacific by anomalous convection characterized by an east west dipole structure one to two weeks prior to the extratropical onset time in both reanalyses as tropical heating moves eastward toward the central pacific anomalous divergent outflow associated with the local hadley circulation generates an anomalous rossby wave sink source in the subtropics consistent with the retraction extension of the pacific jet prior to onset the signature of the forced anomalies is a pair of cyclonic anticyclonic circulation anomalies centered near the node of the tropical heating dipole wave trains extending from the region of anomalous convection into the extratropics set the stage for th

genesis of secondary uranium minerals associated with jasperoid veins el erediya area eastern desert egypt uranium mineralization in the el erediya area egyptian eastern desert has been affected by both high temperature and low temperature fluids mineralization is structurally controlled and is associated with jasperoid veins that are hosted by a granitic pluton this granite exhibits extensive alteration including silicification argillization sericitization chloritization carbonatization and hematization the primary uranium mineral is pitchblende whereas uranpyrochlore uranophane kasolite and an unidentified hydrated uranium niobate mineral are the most abundant secondary uranium minerals uranpyrochlore and the unidentified hydrated uranium niobate mineral are interpreted as alteration products of petscheckite the chemical formula of the uranpyrochlore based upon the electron probe micro analyzer epma is a left text u 1 07 text ca 0 28 text pb 0 03 text na 0 21 text mg 0 02 right sigma 1 6 b left text nb 0 57 text si 0 62 text zr 0 35 text p 0 20 text fe 0 17 text al 0 06 text ti 0 03 right sigma 2 it is characterized by a relatively high zr content average zro2 6 6 wt the average composition of the unidentified hydrated uranium niobate mineral is text u left text u 1 89 text ca 0 49 text pb 0 13 text na 0 06 text mg 0 02 right sigma 2 59 text nb left text nb 1 31 text fe 0 34 text si 0 14 text p 0 10 text ti 0 05 text zr 0 03 text al 0 03 right sigma 2 0 where u and nb represent the dominant cations in the u and nb site respectively uranophane is the dominant u6 silicate phase in oxidized zones of the jasperoid veins kasolite is less abundant than uranophane and contains major u pb and si but only minor ca fe p and zr a two stage metallogenetic model is proposed for the alteration processes and uranium mineralization at el erediya the primary uranium minerals were formed during the first stage of the hydrothermal activity that formed jasperoid veins in el eradiya granite 130 160 ma this stage is related to the late jurassic early cretaceous phase of the final pan african tectono thermal event in egypt after initial formation of el erediya jasperoid veins a late stage of hydrothermal alteration includes argillization dissolution of iron bearing sulfide minerals formation of iron oxy hydroxides and corrosion of primary uranium minerals resulting in enrichment of u ca pb zr and si during this stage petscheckite was altered to uranpyrochlore and oxy petscheckite uranium was likely transported as uranyl carbonate and uranyl fluoride complexes with change of temperature and ph these complexes became unstable and combined with silica calcium and lead to form uranophane and kasolite finally at a later stage of low temperature supergene alteration oxy petscheckite was altered to an unidentified hydrated uranium niobate mineral by removal of fe

the role of crust thickness in runoff generation from microbiotic crusts contrary to humid areas where runoff takes place following the saturation of the soil column runoff in arid and semiarid zones takes place when rain intensities exceed the infiltration capability of the upper soil crust whether physical crust or microbiotic crust mc this type of overland flow known as hortonian overland flow hof is not fully understood especially in the case of mc in particular little is known regarding the effect of crust thickness and its fine silt and clay content on runoff generation with some scholars claiming that runoff generation is positively correlated with crust thickness and fine content in an attempt to determine the effect of crust thickness and to assess the role played by the silt and clay on runoff generation a set of field and lab experiments were undertaken on mcs inhabiting sand dunes in the negev desert israel these included sprinkling experiments coupled with measurements of the physical thickness silt and clay and biological chlorophyll protein total carbohydrates properties of 0 5 10 mm thick crusts the data showed that runoff generation took place on surfaces as thin as 0 5 0 7 mm only and was not correlated with the fine silt and clay content the implications for hof and for arid ecosystems are discussed copyright 2014 john wiley sons ltd

extratropical forcing of tropical wave disturbances along the indian ocean itcz the role of extratropical waves in the excitation of tropical waves on submonthly timescales is explored along the indian ocean intertropical convergence zone itcz during the austral summer using japanese reanalysis products and noaa outgoing longwave radiation data the analysis period is december february of 1979 1980 to 2008 2009 the submonthly tropical waves are regarded as a type of rossby wave propagating along the mean monsoon westerly flow they play an important role in modulating the indian ocean itcz convection the linkage between the tropical and extratropical waves which is responsible for the formation and strengthening of tropical waves is examined composite analysis results linked to the tropical wave train development show that the midlatitude rossby wave train progresses eastward and northeastward from the south atlantic into the subtropical indian ocean as a trough and ridge that form part of the midlatitude wave train approach the southern africa southwest indian ocean swio region a southwest northeast oriented wave train is subsequently established originating from this feature and is strengthened across the tropical indian ocean the midlatitude wave propagation toward the subtropics induces the growth of the trough and ridge over the swio wave activity flux diagnostics indicate that the amplified trough and ridge over the swio act as an energy source for northeastward amplification of the tropical waves through the wave energy dispersion process the results suggest that the propagation of the midlatitude wave toward the swio is the fundamental mechanism behind the development of the tropical waves along the indian ocean itcz

convectively coupled equatorial waves 1 convectively coupled equatorial waves ccews control a substantial fraction of tropical rainfall variability their horizontal structures and dispersion characteristics correspond to matsuno s 1966 solutions of the shallow water equations on an equatorial beta plane namely kelvin equatorial rossby mixed rossby gravity and inertio gravity waves because of moist processes the tilted vertical structures of ccews are complex and their scales do not correspond to that expected from the linear theory of dry waves the dynamical structures and cloud morphology of ccews display a large degree of self similarity over a surprisingly wide range of scales with shallow convection at their leading edge followed by deep convection and then stratiform precipitation mirroring that of individual mesoscale convective complexes ccews have broad impacts within the tropics and their simulation in general circulation models is still problematic although progress has been made using simpler models a complete understanding of ccews remains a challenge in tropical meteorology

channel floodplain connectivity during an extreme flood event implications for sediment erosion deposition and delivery the term connectivity has emerged as a powerful concept in hydrology and geomorphology and is emerging as an innovative component of catchment erosion modeling studies however considerable confusion remains regarding its definition and quantification especially as it relates to fluvial systems this confusion is exacerbated by a lack of detailed case studies and by the tendency to treat water and sediment separately extreme flood events provide a useful framework to assess variability in connectivity particularly the connection between channels and floodplains the catastrophic flood of january 2011 in the lockyer valley southeast queensland australia provides an opportunity to examine this dimension in some detail and to determine how these dynamics operate under high flow regimes high resolution aerial photographs and multi temporal lidar digital elevation models dems coupled with hydrological modeling are used to assess both the nature of hydrologic and sedimentological connectivity and their dominant controls longitudinal variations in flood inundation extent led to the identification of nine reaches which displayed varying channel floodplain connectivity the major control on connectivity was significant non linear changes in channel capacity due to the presence of notable macrochannels which contained a 3000 average recurrence interval ari event at mid catchment locations the spatial pattern of hydrological connectivity was not straight forward in spite of bankfull discharges for selected reaches exceeding 5600m 3 s 1 data indicate that the main channel boundary was the dominant source of sediment while the floodplains where inundated were the dominant sinks spatial variability in channel floodplain hydrological connectivity leads to dis connectivity in the downstream transfer of sediments between reaches and affected sediment storage on adjacent floodplains consideration of such variability for even the most extreme flood events highlights the need to carefully consider non linear changes in key variables such as channel capacity and flood conveyance in the development of a quantitative connectivity index copyright c 2013 john wiley sons ltd

differential responses of hillslope and channel elements to rainfall events in a semi arid area the degree of hydrological connectivity of hillslope elements in a semi arid climate was studied at the season and event timescales field data were obtained in rambla honda a medalus project field site situated in se spain on micaschist bedrock and with 300 mm annual rainfall the season timescale was assessed using correlation analysis between soil moisture and topographic indices the event timescale was studied by a quasi continuous monitoring of rainfall soil moisture runoff and piezometric levels results show that widespread transfers of water along the hillslope are unusual because potential conditions for producing overland flow or throughflow are spatially discontinuous and extremely short lived during extreme events runoff coefficients may be locally high ca 40 on slope lengths of 10 m but decrease dramatically at the hillslope scale 10 on slope lengths of 50 m two mechanisms of overland flow generation have been identified infiltration excess and local subsurface saturation from upper layers the former occurs during the initial stages of the event while the latter which is quantitatively more important takes place later and requires a certain time structure of rainfall intensities that allow saturation of the topsoil and the subsequent production of runoff hillslopes and alluvial fans function as runoff sources and sinks respectively permanent aquifers are lacking in rambla honda variable proportions of hillslope areas may contribute to flash floods in the main channel but their contribution to the formation of saturated layers within the sediment fill is very limited

statistical properties of episodes of enhanced 2 3 day convection in the indian and pacific oceans abstract using 9 yr of ir brightness temperature values as a proxy for tropical convection the climatology and statistics of the 2 3 day convective oscillation signal are examined these higher frequency oscillations are shown to have a very different spatial distribution than the signal associated with the 25 70 day intraseasonal oscillation making it quite unlikely that these oscillations simply represent a form of noise in the time series the characteristics of the oscillations are shown to be strong functions of latitude season and strength of the oscillation itself only the strongest of the 2 3 day oscillations prove to be in good agreement with the properties shown in previous studies which were based on smaller spatial and temporal domains these strong oscillations manifest a strong association with the intraseasonal oscillation and westerly wind bursts particularly in the deep tropics weaker oscillations on the other hand are found to be more stochastic and less dependent on larger sca

currents in monterey submarine canyon 1 flow fields of mean subtidal and tidal frequencies between 250 and 3300 m water depths in monterey submarine canyon are examined using current measurements obtained in three yearlong field experiments spatial variations in flow fields are mainly controlled by the topography shape and width of the canyon the mean currents flow upcanyon in the offshore reaches 1000 m and downcanyon in the shallow reaches 100 m amplitude isotherm oscillations and associated high speed rectilinear currents the 15 day spring neap cycle and a 3 day band are the two prominent frequencies in subtidal flow field neither of them seems directly correlated with the spring neap cycle of the sea level

behavior of one to two week summertime subtropical wind maxima over the south pacific during an enso cycle abstract the behavior of subtropical jet streaks over the australian south pacific region is investigated for four consecutive 6 month summer seasons november to april during the period 1985 89 the study is an extension of a recent one by ko and vincent hereafter referred to as kv in which jet streaks during the summer season of 1984 85 were examined ko and vincent found that the upper tropospheric zonal wind behaved in a quasi periodic manner with maxima recurring over the western south pacific at intervals between one and two weeks in the present study wind maxima are found to exhibit a 1 2 week periodic oscillation over the south pacific in all four years thus substantiating the finding by kv in addition a second set of jet streaks with a similar periodicity is found over the southern australian region it is also seen that the mean summertime position of the south pacific jet and its accompanying jet streaks are much farther cast during the el nino event of 1986 87 than they are in the

two day disturbances in the equatorial western pacific from november 1992 to february 1993 westward propagating disturbances with scales of 1000 1500 km frequented the equatorial western pacific they propagated at about 16 m s 1 and their passage was accompanied by a two day oscillation in high cloudiness their convection was most intense when the lower troposphere was cool and the level of free convection was relatively low the disturbances propagated westward at about 18 m s 1 faster than the lower tropospheric flow this rapid propagation may have been the result of a coupling between the disturbance s convection and the 20 m s 1 vertical mode the signal of this mode was apparent in vertical profiles of temperature and wind and the most intense convection began when the mode dynamically cooled the lower troposphere lowering the level of free convection

multiscale variability of deep convection in relation to large scale circulation in toga coare deep convection over the indo pacific oceanic warm pool in the tropical ocean global atmosphere coupled ocean atmosphere response experiment toga coare occurred in cloud clusters which grouped together in regions favoring their occurrence these large groups of cloud clusters produced large scale regions of satellite observed cold cloud top temperature this paper investigates the manner in which the cloud clusters were organized on time and space scales ranging from the seasonal mean pattern over the whole warm pool region to the scale of individual cloud clusters and their relationship to the large scale circulation and sea surface temperature sst the dominant convective variability was associated with the intraseasonal oscillation iso a large eastward propagating ensemble of cloud clusters marked the iso s progress the meridional structure of the iso was strongly affected by the seasonal cycle with a southward shift from the northern hemisphere in october november to the southern hemisphere in january february the sst had an intraseasonal signal in lagged quadrature with the cold cloudiness and rainfall in coare the sst increased decreased during the convectively suppressed active phases of the iso enhanced low level westerly winds occurred toward the later stages of the enhanced convection periods of the iso though not always centered at the equator the strongest westerlies tended to be located between two synoptic scale cyclonic gyres which were often not symmetric about the equator in the low level wind field this asymmetry in the anomalous equatorial low level westerlies may have different implications for the oceanic response in the coupled atmosphere ocean system than those centered on the equator the cyclonic gyres contained highly concentrated deep convection and in four cases the gyres developed into tropical cyclones within the envelope marking the convectively active phase of the iso cloud clusters were frequently concentrated into westward propagating disturbances with a local periodicity of similar to 2 days these 2 day disturbances have been identified in earlier spectral studies and appear to be related to westward propagating inertio gravity waves in coare they typically contained numerous cloud clusters which underwent a distinct diurnal cycle most of the cloud clusters embedded in the 2 day disturbances moved westward though some were stationary and a few moved eastward a cloud duster tracking program identified groups of clusters lime dusters that exhibited continuity in time and space in the most convectively active period of the iso the tracking program identified almost the entire iso cloud ensemble as a long lasting trackable superconvective system this observation indicates the lack of a distinct scale separation between convection and large scale disturbances during the most intense convective periods in coare

characteristics and origin of egyptian younger granites the post tectonic younger granite plutons of egypt are products of a single magmatic episode 603 to 575 m y ago which marked the end of a cratonizing process and the beginning of truly anorogenic activity in the egyptian red sea hills exposure of the nubian arabian shield prior to younger granite magmatism the region is interpreted as having been the locus of island arc small ocean basin development with later compressive coalescence of arcs and basins this early period was characterized by the formation of deformed eugeosynclinal sediantary and volcanic rocks ophiolites and orogenic batholiths a tectonic environment including the deposition of terrigenous sediments in isolated fault bounded basins and intermediate to felsic volcanism followed the culmination of orogenic activity the younger granites intrude all of these earlier units after the time of younger granite intrusion and prior to red sea rifting magmatism was limited to minor alkaline volcanism and intrusions ranging from early paleozoic to tertiary in age the egyptian younger granites occur as three petrologic geochemical groups but all three are post tectonic and epizonal other characteristics common to all groups are homogeneity and an absence of tectonic foliation and pegmatites younger granite quartz veins occur in place of pegmatites which are common in older orogenic plutons the modal abundances of quartz plagioclase and alkali feldspar in the younger granites classify them as true granites with a few granodiorite samples among the least differentiated group iii plutons group i granites have been extensively albitized and silicified resulting in the modification of original hypersolvus quartz feldspar fabrics group iii rocks are strictly subsolvus and contain larger proportions of plagioclase other than hydrothermal metasomatic albite and mafic mineral phases than do groups i or ii group ii granites are similar to group i but are less albitized and have higher mafic contents the eighteen plutons studied range from peraluminous to slightly peralkaline granitic rocks group iii plutons are the most mafic with high mgo total pe cao tio 2 a1 2 o 3 and sr contents group i granites are very siliceous to 80 sio 2 and also contain the most rb y nb and u all reflecting their hydrothermal alteration group i and to a lesser extent group ii are very depleted in mgo tio 2 and sr relative to calc alkaline granites taken as e whole the analyzed younger granite groups are not as rich in large ion lithophylic lil elements as similar post tectonic plutons from other areas egyptian younger granites typically have low 87 sr 86 0 701 0 7025 and are not associated with mafic differentiates nor with other diverse rock types often found in many post tectonic alkali granite provinces from the available data the younger granites can be considered as low temperature products of a eutectic partial melting process that took place in depleted upper mantle or lower crustal material the postulated geologic history of the region prior to younger granite intrusion indicates that the source of the granite melts was probably cratonized oceanic continental margin or intra oceanic are and basin material the chemistry and tectonic setting of the younger granites strongly demonstrates their anorogenic character and tends to argue against their derivation from subduction zone activity

runoff generation sediment movement and soil water behaviour on calcareous limestone slopes of some mediterranean environments in southeast spain abstract an interpretation of soil hydrology and erosion data obtained from limestone areas in southeast spain is presented in the framework of recent hypotheses on runoff generation mechanisms in mediterranean environments the main objective is to synthesise and harmonise the data in theoretical concepts or behavioural models of hydrological functioning of mediterranean limestone slopes for this purpose data were collected in a typical limestone area with climatic characteristics ranging from subhumid to semiarid several sites were chosen with comparable slopes vegetation and soils along a transect of 20 km to carry out several research projects the data discussed in this paper consist of information on water redistribution within the soil profiles obtained from long duration up to 5 h rainfall simulation experiments with continuous monitoring of soil moisture at different depths runoff and sediment concentration data were obtained i from rainfall simulation experiments with different antecedent soil moisture conditions and ii as natural results from open gerlach plots on runoff and sediment movement over 4 years three conceptual models of water redistribution during the infiltration process could be observed two of them imply nonuniform water redistribution within the soil profile due mainly to macropore flow caused by specific soil surface characteristics at the plot scale runoff generated in bare patches is mainly hortonian in plots with previously wetted soils or soils with high infiltration capacities the generated runoff implies the saturation of the upper soil both types of runoff are discontinuous through time and space the runoff generation mechanisms at the slope scale have been synthesised into two conceptual models a hortonian discontinuous runoff model that takes place in the most degraded slopes or during high intensity rain events and a mixed runoff generation model in less degraded slopes or in previously wet soils where infiltration excess runoff as well as saturation excess runoff can happen on the same slope in both cases slopes behave as a patchwork of runoff and runon areas the size of the runoff or runon patches is dependent on the climatological conditions these control the hydrological disconnection between different parts of the slopes hortonian and saturation runoff can both be generated and infiltrated downslope

channel network extent in the context of historical land use flow generation processes and landscape evolution in the north carolina piedmont intensive agricultural land use in the 18th to early 20th centuries on the southeastern piedmont resulted in substantial soil erosion and gully development today many historically farmed areas have been abandoned and afforested and such landscapes are an opportunity to study channel network recovery from disturbance by gullying channel initiation mapping watershed area slope relationships and field monitoring of flow generation processes are used to identify channel network extent and place it in hydrologic historical and landscape evolution context in six study areas in the north carolina piedmont 100 channel heads were mapped in fully forested watersheds revealing a channel initiation relationship of 380 as1 27 where a is contributing area m2 and s is local slope m m flow in these channels is generated by subsurface and overland flow the measured relative slope exponent is lower than expected based on literature values of 2 for forested watersheds with subsurface and overland flow suggesting that the channel network extent may reflect a former hydrological regime however geomorphic evidence of recovery in channel heads within fully forested watersheds is greater than those with present day pasture present day channel heads lie within hollows or downslope of unchanneled valleys which may be remnants of historical gullies and area slope relationships provide evidence of colluvial aggradation within the valleys channel network extent appears to be sensitive to land use change with recovery beginning within decades of afforestation channel initiation mapping and area slope relationships are shown to be useful tools for interpreting geomorphic effects of land use change copyright 2012 john wiley sons ltd