a numerical simulation of quasi stationary tropical convective bands a method of imposing large scale ascent on a three dimensional numerical model is introduced and this is shown to be crucial in maintaining the quasi stationary convective bands observed in gate the effects of ascent on the overall convective development are to enhance updraughts and particularly to maintain the development of new convection cells the magnitutude of the forcing is varied to show the sensitivity of growth on convergence a quasi stationary convective band aligned approximately parallel to the low level wind shear is simulated in an initial environment defined from soundings obtained from the gate ships researcher and oceanographer on 3 september 1974 the organization is therefore quite distinct from that of fast moving squall lines aligned at right angles to the shear the simulated convective system has marked dynamical similarity to the observed bands these consisted of a number of cumulonimbus cells with new cells developing on the eastern end of the hand with deeper cells to the west the cells generally travel along the line the large shear due to the strong low level jet is crucial in influencing the band development and orientation the dynamical structure of the convective band is investigated by a trajectory analysis which indicates an organized three dimensional structure the transports of heat moisture and momentum are calculated and a quasi balance between large scale ascent and cloud induced descent on a time scale of a few hours is shown to exist apparent heat sources and moisture sinks are calculated and these have a bi modal vertical structure in general agreement with those in observed tropical cloud clusters

long lived mesoscale systems in a low convective inhibition environment part i upshear propagation abstractpart ii of this study of long lived convective systems in a tropical environment focuses on forward tilted downshear propagating systems that emerge spontaneously from idealized numerical simulations these systems differ in important ways from the standard mesoscale convective system that is characterized by a rearward tilted circulation with a trailing stratiform region an overturning updraft and a mesoscale downdraft in contrast to this standard mesoscale system the downshear propagating system considered here does not feature a mesoscale downdraft and although there is a cold pool it is of secondary importance to the propagation and maintenance of the system the mesoscale downdraft is replaced by hydraulic jump like ascent beneath an elevated forward tilted overturning updraft with negligible convective available potential energy therefore the mesoscale circulation is sustained almost entirely by the work done by the horizontal pressure gradient and the kinetic energy available from

relative age dating of transported regolith and application to study of landform evolution in the appalachians abstract surficial deposits in the appalachians generally are thin discontinuous and difficult to date in the absence of numerical dates particularly for older deposits relative age indices based on degree of weathering and soil development have been used to distinguish and correlate deposits of different ages a favorite locale of relative age studies has been stream terraces where chronosequences have been developed to shed light on the relationship between time and weathering soil development the lack of applicable numerical dating techniques has led some researchers to establish relative chronosequences in which height of stream or fan terraces above modern river level arl serves as a proxy for time approximate incision rates can then be used to estimate numerical ages of the deposits relative age correlations between the weathering indices on the terraces and comparable indices on dated deposits on the coastal plain and in nearby glaciated regions suggest that ages so estimated are the right order of magnitude relative age indices show correlations with height arl that are as high as those with time perhaps because more data sets are available for relative chronosequences than for true chronosequences analogous relative age sequences can be established for alluvial fans and even for hillslope colluvium many weathering indices have been employed but weathering rind thickness on mafic to intermediate clasts has proved to be a particularly consistent and useful parameter in addition to showing how weathering and soil development progress over time relative age dating has shed light on the manner in which landforms evolve along some rivers for example the areal extent of old highly weathered alluvium far exceeds that of younger alluvium suggesting that formerly floodplains and low terraces were much more extensive than at present in addition the manner in which weathering indices on some river terrace sequences vary with height arl suggests that incision rate has changed through time relative age mapping of alluvial fans produces a map pattern of older and younger fan surfaces that allows the sequence of fan development to be inferred in one case suggesting a scenario different from those previously described for fans mapping also shows that the relative abundance of young intermediate and old fan surfaces varies greatly from one area to another several studies have demonstrated clustering of relative age values into a small number of groups suggesting temporal grouping and thus episodic deposition on fans regression of weathering rind thickness against height above modern drainageways of remnant fan surfaces in two areas suggests that fans are being incised more rapidly in one area than in another relative age of hillslope colluvium also aids geomorphic interpretation young brown colluvium is much more common than old red colluvium near the glacier border where red colluvium rarely occurs at the surface but typically is covered by brown colluvium probably mobilized during the late pleistocene distant from the ice margin however red colluvium is extensively exposed on interfluves relatively stable hillslopes can also be distinguished from active ones in this manner for example colluvium on hillslope noses is somewhat more weathered than that on hollow floors and sideslopes

kinematic and precipitation characteristics of convective systems observed by airborne doppler radar during the life cycle of a madden julian oscillation in the indian ocean abstractthis study presents characteristics of convective systems observed during the dynamics of the madden julian oscillation dynamo experiment by the instrumented noaa wp 3d aircraft nine separate missions with a focus on observing mesoscale convective systems mcss were executed to obtain data in the active and inactive phase of a madden julian oscillation mjo in the indian ocean doppler radar and in situ thermodynamic data are used to contrast the convective system characteristics during the evolution of the mjo isolated convection was prominent during the inactive phases of the mjo with deepening convection during the onset of the mjo during the mjo peak convection and stratiform precipitation became more widespread a larger population of deep convective elements led to a larger area of stratiform precipitation as the mjo decayed convective system top heights increased though the number of convective systems decreased eventually transitioning back to isolated convection a distinct

relative age relationships of debris flow deposits in the southern blue ridge north carolina abstract periods of increased landscape instability in the southern blue ridge were assessed with relative ages of three sequences of debris flow deposits the sequences consist of a series of lobate deposits that are expressed as step like landforms on the floors of host valleys data were collected at three sites from soil pits on the toe and apex of debris flow deposits relative ages were obtained by qualitatively and statistically examining data on clast weathering soil color clay content and iron species consistent results among the indicators of relative age demonstrate that they have utility in warm to temperate humid environments at each site the topographically highest debris flow deposits are slightly older than those at lower elevations one deposit at each of the three sites has a relative age that is very similar to that of one deposit at the other sites this similarity in age indicates that an external factor such as extreme precipitation accounts for the formation of debris flows at approximately the same time in the geological past one of the sites however also has deposits that are clearly younger than the deposits at the other sites which indicates that intrinsic factors also affect the formation of debris flows in the region

the influence of changing orbital parameters and surface boundary conditions on climate simulations for the past 18 000 years abstract general circulation model experiments at 3000 year intervals for the past 18 000 years were made to estimate the magnitude timing and pattern of the climatic response to prescribed changes of orbital parameters date of perihelion axial tilt eccentricity and glacial age lower boundary conditions ice sheets land albedo sea ice and sea surface temperature the experiments used the community climate model ccm of the national center for atmospheric research ncar the response of monsoon circulations and tropical precipitation to the orbitally produced solar radiation changes was much larger than the response to changes of glacial age boundary conditions the continental interior of eurasia was 2 4 k warmer in summer and summer monsoon precipitation of north africa south asia was increased by 10 20 between 12 000 and 6000 yr bp before present when perihelion occurred during northern summer rather than in winter as now and the earth s axial tilt was larger than now southern hemisphe

the relationship between emex mesoscale precipitation feature properties and their environmental characteristics abstract characteristics of the prestorm environment of equatorial mesoscale experiment emex mesoscale precipitation features mpfs are related to properties of them systems using regression analysis although environmental thermodynamic parameters are poorly correlated with emex mpf properties mainly because environmental thermodynamic conditions varied little among mpfs kinematic parameters are well correlated to these properties lines whose environments have low level shear the shear between about 950 and 750 mb exceeding 5 m s 1 are oriented normal to the direction of this shear lines where the low level shear is under 5 m s 1 are oriented along the direction of the midlevel shear the shear between about 800 and 400 mb convective line speeds correlate well with the maximum speed of the rear to front flow in the troposphere below 300 mb direction of mpf motion is nearly coincident with the tropospheric mean wind direction convective line length is proportional to the magnitude of the men

nd and sr isotope systematics of miocene to holocene volcanic rocks from southwest japan volcanism since the opening of the japan sea isotope nd and sr and geochemical data for twelve volcanic rocks from the shimane oki san in region of southwest japan give some insight into the miocene recent volcanic history of southern japan since rifting from the asian mainland the oldest rocks examined dolerites and ushikiri formation were erupted during the opening of the japan sea at about 15 ma and comprise arc tholeiites derived from a depleted source end 0 esr 0 interpreted in terms of a depleted mantle source modified by a slab derived fluid volcanics of oki dozen island in the japan sea are alkalic derived from an enriched mantle plume isotopically distinct from nearly oki dogo island eruption of the calc alkaline wakurayama andesite early pliocene and both arc and within plate type basalts 1 ma show that magmas were tapped from a variety of sources taking into account plate tectonics and seismic data the subduction influence until the quaternary was the pacific plate with philippines sea plate subduction affecting quaternary and younger volcanics

migration of fluid phases and genesis of basalt magmas in subduction zones dehydration and hydration reactions in both the downgoing lithosphere and the overlying mantle wedge have been examined in order to understand the role of h2o in the production of magmas at convergent plate boundaries the subduction of oceanic lithosphere occurring with increasing pressures and rising temperatures causes liberation of h2o from the slab amphibole which can be stable to the highest pt conditions among hydrous phases in the slab decomposes at around 90 km depth it follows that the subducted lithosphere is essentially anhydrous beneath volcanic arcs lying more than 110 km above the slab and that the supply of slab derived h2o is not a direct trigger for the production of arc magmas instead the h2o released from downgoing lithosphere reacts with the forearc mantle wedge to crystallize hydrous minerals serpentine talc amphibole chlorite and phlogopite this hydrated peridotite is dragged downward on the slab toward higher pt regions and releases h2o to shallower potential magma source regions in the mantle wedge combining experimental data on the stability of serpentine and talc with the thermal structure in the mantle wedge it is concluded that those minerals decompose beneath the forearc region on the other hand high pt experimental and thermodynamic data suggest that dehydration of amphibole and chlorite in the downdragged hydrated peridotite can take place just beneath a volcanic front phlogopite in the peridotite decomposes to release h2o at a deeper level about 200 km h2o liberated from the hydrated peridotite causes partial melting of overlying mantle wedge peridotites along with the migration of h2o through the above processes subduction components especially large ion lithophile elements can be overprinted on the magma source region which governs the geochemical characteristics of arc magmas

stratospheric gravity waves generated by multiscale tropical convection abstract the generation of gravity waves by multiscale cloud systems evolving in an initially motionless and thermodynamically uniform environment is explored using a two dimensional cloud system resolving model the simulated convection has similar depth and intensity to observed tropical oceanic systems the convection self organizes into preferred horizontal and temporal scales involving weakly organized propagating cloud clusters the multiscale systems generate a broad spectrum of gravity waves with horizontal scales that range from the cloud system scale up to the cloud cluster scale the gravity waves with the largest horizontal scale play an important role in modifying layered tropospheric inflow and outflow to the cloud systems which in turn influence the multiscale convective organization slower moving short scale gravity waves make the strongest individual contribution to the vertical flux of horizontal momentum and cause a robust peak in the momentum flux spectrum that corresponds to the lif

textural and compositional evidence for magma mixing and its mechanism abu volcano group southwestern japan quaternary basalts andesites and dacites from the abu monogenetic volcano group sw japan composed of more than 40 monogenetic volcanoes show two distinct chemical trends especially on the feo mgo vs sio2 diagram one trend is characterized by feo mgo enrichment with a slight increase in sio2 content fe type trend whereas the other shows a marked sio2 enrichment with relatively constant feo mgo ratios si type trend the fe type trend is explained by fractional crystallization with subtraction of olivine and augite from a primitive alkali basalt magma rocks of the si type trend are characterized by partially melted or resorbed quartz and sodic plagioclase phenocrysts and or fine grained basaltic inclusions they are most likely products of mixing of a primitive alkali basalt magma containing olivine phenocrysts with a dacite magma containing quartz sodic plagioclase and hornblende phenocrysts petrographic variation as well as chemical variation from basalt to dacite of the si type trend is accounted for by various mixing ratios of basalt and dacite magmas pargasitic hornblende and clinopyroxene phenocrysts in andesite and dacite may have crystallized from basaltic magma during magma mixing olivine and spinel and quartz sodic plagioclase and common hornblende had crystallized in basaltic and dacitic magmas respectively before the mixing within a lava flow the abundance of basaltic inclusions decreases from the area near the eruptive vent towards the perimeter of the flow and the number of resorbed phenocrysts varies inversely suggesting zonation in the magma chamber

regional variation of morphology of organized convection in the tropics and subtropics 1 properties of organized convection with large horizontal area 1000 km2 and with different horizontal structures in the tropics and subtropics are investigated by using 14 years of tropical rainfall measuring mission observations first the convective features cfs are defined as contiguous areas of convective precipitation detected by the tropical rainfall measuring mission precipitation radar using the minor and major axes of fitted ellipses the morphology of the cfs are described as closer to a circular or a line shape regional variations and the properties of organized convection are examined with cfs with area 1000 km2 after categorizing them by their shapes organized convection tends to have larger extent and a higher fraction of near circular shapes over land than over ocean shallow organized convection with maximum radar echo top height below 4 5 km is found mainly over ocean and some coastal regions of all tropical oceans most shallow organized convection is found over the east pacific the fraction of line shaped organized convection is higher over the ocean than over land and is higher in the subtropics than in the tropics more convective lines are found in winter than in summer over oceans but more in summer over land organized convective lines are slightly less convectively intense indicated by lower 30 dbz echo top heights and warmer 37 ghz brightness temperatures than those with near circular shapes orientations of organized convective lines are often aligned with fronts dry lines warm ocean currents coastlines and mountain slopes over the subtropics organized convective lines are tilted more east west over land and more north south over oceans the largest and the most intense convective lines are found over central africa argentina and southeast u s over land and over several warm currents in subtropical oceans

momentum flux by lines of cumulonimbus over the tropical oceans abstract examination of aircraft and rawinsonde data gathered in nine tropical mesoscale convective line cases indicates that all but two lines systematically increased front to rear momentum at heights greater than about 4 km and rear to front momentum at lower levels where front is defined as the direction toward which the line is moving the convective lines were characterized by a leading 10 20 km wide band of convective clouds and a trailing region of stratiform cloudiness most wore propagating lines moving into the wind at all levels consistent with mixing length theory the vertical transport of the horizontal wind component parallel to the lines was down the vertical gradient of the component resulting in a decrease of its vertical shear smaller more random cloud groups and the upper portions of a convective line with isolated towers transported both components of horizontal momentum downgradient normalization of the vertical flux of horizontal momentum normal to the line u w su

a theory for strong long lived squall lines abstract we study herein the mechanics of long lived line oriented precipitating cumulus convection squall lines using two and three dimensional numerical models of moist convection these models used in juxtaposition enable us to address the important theoretical issue of whether a squall line is a system of special long lived cells or whether it is a long lived system of ordinary short lived cells our review of the observational literature indicates that the latter is the most consistent paradigm for the vast majority of cases but on occasion a squall line may be composed of essentially steady supercell thunderstorms the numerical experiments presented herein show that either type of squall line may develop from an initial line like disturbance depending on the magnitude and orientation of the environmental shear with respect to the line with shallow shear oriented perpendicular to the line a long lived line evolves containing individually short lived cells our analysis of this type o

organization of oceanic convection during the onset of the 1998 east asian summer monsoon the organizational modes of convection over the northern south china sea scs during the onset of the summer monsoon are documented using radar and sounding data from the may june 1998 south china sea monsoon experiment scsmex the onset occurred in mid may with a rapid increase in deep convection over a 10 day period accompanied by a major shift in the circulation over the east asian region analysis of bureau of meteorology research centre bmrc radar data from dongsha island reveals a wide range of organizational modes of convection over the northern scs proximity sounding data indicate that lower and middle level vertical wind shears exerted a dominant control over the orientation of convective lines within mesoscale convective systems in this region as has been found in the australian monsoon region and the equatorial western pacific the results are consistent with the conceptual model of lemone et al based on the tropical ocean global atmosphere coupled ocean atmosphere response experiment toga coare except two new organizational modes have been identified shear parallel bands for strong low level shear and weak midlevel shear when there is weak instability and the air is dry aloft and shear parallel bands for strong shears in both layers when the shear vectors are in the same direction midlatitude influences namely the passage of troughs over southern china likely contributed to these two additional modes the stratiform rain fraction from the convective systems during the monsoon onset period was relatively small 26 compared to the estimated average of about 40 for the entire tropics this small fraction is attributed to the weak instability during the onset period and relatively dry air in the upper troposphere

the role of catastrophic geomorphic events in central appalachian landscape evolution abstract catastrophic geomorphic events are taken as those that are large sudden and rare on human timescales in the nonglaciated low seismicity central appalachians these are dominantly floods and landslides evaluation of the role of catastrophic events in landscape evolution includes assessment of their contributions to denudation and formation of prominent landscape features and how they vary through space and time tropical storm paths and topographic barriers at the blue ridge and allegheny front create significant climatic variability across the appalachians for moderate floods the influence of basin geology is apparent in modifying severity of flooding but for the most extreme events flood discharges relate mainly to rainfall characteristics such as intensity duration storm size and location landslide susceptibility relates more directly to geologic controls that determine what intensity and duration of rainfall will trigger slope instability large floods and landslides are not necessarily effective in producing prominent geomorphic features large historic floods in the piedmont have been minimally effective in producing prominent and persistent geomorphic features in contrast smaller floods in the valley and ridge produced erosional and depositional features that probably will require thousands of years to efface scars and deposits of debris slide avalanches triggered on sandstone ridges recover slowly and persist much longer than scars and deposits of smaller landslides triggered on finer grained regolith even though the smaller landslides may have eroded greater aggregate volume the surficial stratigraphic record can be used to extend the spatial and temporal limits of our knowledge of catastrophic events many prominent alluvial and colluvial landforms in the central appalachians are composed of sediments that were deposited by processes similar to those observed in historic catastrophic events available stratigraphic evidence shows two scales of temporal variation one related to quaternary climate changes and a more recent higher frequency variation due to rare events during the holocene in much of the central appalachians landforms related to quaternary climate changes persist as the most prominent features despite the modifying effects of late holocene catastrophic events

holocene erosion sedimentation and stratigraphy at raven fork southern blue ridge mountains usa holocene colluvial and alluvial stratigraphy and a radiocarbon chronology are presented for the valley of the lower three kilometers of raven fork a mountain stream draining 194 km 2 of high relief 1 3 km terrain of the southern blue ridge mountains in western north carolina usa which is in a region that lacks good chronological data lower hillslopes alluvial colluvial fans alluvial bottomlands first terrace and floodplain and the modern stream channel are landforms described with respect to soils stratigraphy and sedimentary structures standard methods for subsurface investigations core holes excavation units exposures are used in conjunction with extensive archeological excavations and cultural chronologies radiocarbon ages from each landform are used to calculate long term average rates of sedimentation results indicate that the first half of the holocene experienced somewhat more rapid rates of hillslope sedimentation 0 3 to 1 1 mm yr than the last half of the holocene 0 1 0 2 mm yr on footslopes toeslopes and alluvial colluvial fans prior to historic time we suggest that these subtle differences in the rates of sedimentation were driven by changes in global paleoclimate that favored a high frequency of heavy rainfall including tropical storms and or severe thunderstorms and more and possibly larger floods during the first half of the holocene prehistoric rates of vertical accretion on the first terrace t1 ranged from 0 1 to 0 8 mm yr between about 10 000 and 3000 calendar years ago and incision below t1 formed the late holocene floodplain beginning at about 6000 years ago we suggest that this incision is linked to a reduction in the supply of sediment and a reduction in the magnitude of floods historical rates of sedimentation on all parts of the depositional landscape 2 0 2 7 mm yr on hillslopes and fans and 5 8 6 5 mm yr on floodplains were about an order of magnitude greater than prehistoric rates we attribute these rates to human impacts such as timber harvest and land clearing which caused accelerated erosion we attribute the abundance of fine grained sediment in streams of the southern blue ridge province which is atypical in many mountain streams around the world to the regionally widespread mantle of saprolite as a source of sediment to the fluvial system holocene sedimentation on all depositional landforms in the valley led to sedimentary burial of archeological materials which highlights the need to consider site burial on lower hillslopes and terraces for evaluation of the cultural resources in the southern blue ridge mountains these findings show that the entrenched condition of the raven fork channel was inherited from the middle holocene and can be considered a natural state for this mountain stream casting doubt on the negative connotation that is often assigned to entrenched channels

mechanisms of shallow landslides on soil mantled hillslopes with permeable and impermeable bedrocks in the boso peninsula japan abstract rainfall induced shallow landslides play a vital role in hillslope denudation processes in humid temperate regions this study demonstrates the contrasting mechanisms of landslides in adjoining hills with permeable sandstone and impermeable mudstone bedrock in the boso peninsula japan the characteristics of slope hydrology were inferred from pressure head monitoring and rainfall runoff observations an analysis of slope stability provided critical conditions for several previously occurring landslides the results are as follows 1 in slopes with the permeable sandstone infiltrated rainwater percolates through the bedrock as an unsaturated gravitational flow the wetting front migration results in a decrease of soil cohesion and causes landsliding at the steep lower part of the hillslopes 2 in contrast the impermeable mudstone beneath a thin soil layer causes a transient positive pressure head that generates a saturated subsurface storm flow the reduction in effective normal stress triggers shallow soil slipping at the uppermost part of a hollow

timing of rotational motion of southwest japan inferred from paleomagnetism abstract paleomagnetic field directions for the period younger than 35 ma are obtained from igneous rocks distributed in the san in district inner zone of southwest japan the remanent magnetization of samples between 30 and 35 ma old are fairly well grouped with a mean direction of d 65 9 i 48 6 and 95 6 5 this result establishes that southwest japan rotated clockwise 56 12 during the past 30 m y a declination value of about 60 is observed in the rocks of 28 ma d 52 2 i 33 5 and 21 ma d 69 9 i 49 5 comparing this with results from dacitic rocks with an age of 15 ma in other areas of southwest japan suggests that rotational motion did not occur possibly until 15 ma these results require that the rotation of southwest japan occurred just after the shikoku basin had been created

slope gradient and aspect effects on soils developed from sandstone in pennsylvania abstract this study was initiated to determine the basic characteristics and genesis of soils on gentle to very steep slopes on two contrasting slope aspects two transects a southwest sw and a northwest nw transect were laid out on a sandstone ridge across the summit and steepest convex shoulder positions the thickness of the o a and e horizons was not related to slope gradient across soils on all slope gradients and aspects this indicates that the present rate of soil formation is greater than erosion the influence of erosion on steep slopes could be off set by lateral movement of through flow water above the b horizon or the process of tree throw masks slope gradient effects solum depth b horizon thickness clay fe and al indexes decreased with increasing slope for both the nw and sw aspects organic carbon index decreased with increasing slope for the sw aspect decreases in effective precipitation over relatively larger surface areas at steep versus lower slope gradients a longer influence of periglacial erosion following the wisconsinan glacial advance and present slow but significant soil creep could cause these differences in soil development across the slope solum depth b horizon thickness clay fe and al indexes showed a smaller decrease across the nw compared to the sw slope organic carbon did not decrease across the nw slope the e horizon was also slightly thicker on the nw compared to the sw slope these aspect differences were probably caused by less evaporation on shaded nw compared to sunny sw slopes which produce generally higher moisture levels and more effective eluviation and illuviation on the nw slope

soil chronosequence of brasstown creek blue ridge mountains usa abstract a chronosequence of soils on alluvial terraces in the appalachian highlands of the southeastern united states is identified by simple methods of quantitative soil morphology and chemical analysis the chronosequence is from brasstown creek a 5th order stream draining 65 km 2 of the blue ridge mountains of north georgia the portion of the valley studied is about 1 km wide and contains five quaternary terrace remnants radiocarbon dates show that the floodplain t0 is late holocene and includes historical post ca 1830 a d sediment and the four older terraces t1 t5 are pre holocene the floodplain soils are either entisols in historical sediment or buried inceptisols with weak bw horizons in late holocene to protohistoric sediment the lowest terrace t1 is terminal pleistocene in age and its soils have bt horizons that are about 0 9 m thick 10yr 4 5 to 10yr 5 4 in colour and contain 25 to 35 clay soils on terraces older than t1 become progressively redder and contain more clay with increasing age culminating with 2 5yr hues and 40 to 52 clay in the bt horizon of t5 percent clay in bt horizons rubification indices iron oxide contents and element ratios progressively change with age of the terraces but other morphological properties ph and individual element concentrations are of less use as chronosequence variables

an anthropic soil transformation fingerprinted by rey patterns abstract this focus article deals intentionally with modern soil disturbance in situ this is of interest to archaeologists as after disturbances both short and long term pedogenesis re starts obliterating previous signs soil modifications induced by human activity may be linked to pedogenetic evidence for disturbance with archaeological evidence for the cultural activities we contrasted two 750 m 3 soil pedons an anthrosol and a kastanozem from which the anthrosol is derived using 77 descriptors of soil properties which have been utilized in archaeological studies pedo morphological routine laboratory biochemical metals and rare earth elements plus yttrium rey with the aim of identifying a group of descriptors able to sort the occurrence of human interventions but which one is more promising our findings indicate that by the use of rare earth spatial patterns it is possible to classify the occurrence of human interventions in the case of emplacement of new parent material in respect to bulk soil disturbance in situ

fluorine geochemistry of basaltic rocks from continental and oceanic regions and petrogenetic application fluorine contents in about 300 samples of various types of basalts and related rocks from continental southwestern u s a zaire deccan and south africa and oceanic regions hawaii and mid atlantic ridge between 23 n and 40 n were determined by a selective ion electrode method

the role of environmental shear and thermodynamic conditions in determining the structure and evolution of mesoscale convective systems during toga coare abstract a collection of case studies is used to elucidate the influence of environmental soundings on the structure and evolution of the convection in the mesoscale convective systems sampled by the turboprop aircraft in the tropical ocean global atmosphere toga coupled ocean atmosphere response experiment coare the soundings were constructed primarily from aircraft data below 5 6 km and primarily from radiosonde data at higher altitudes the well documented role of the vertical shear of the horizontal wind in determining the mesoscale structure of tropical convection is confirmed and extended as noted by earlier investigators nearly all convective bands occurring in environments with appreciable shear below a low level wind maximum are oriented nearly normal to the shear beneath the wind maximum and propagate in the direction of the low level shear at a speed close to the wind maximum when there is appreciable shear at middle levels 800 400 mb convective bands form parallel to the shear with

the effect of vertical wind shear on radiative convective equilibrium states abstract using a three dimensional cloud ensemble model a systematic exploration is undertaken of radiative convective equilibrium states as a function of the structure and magnitude of an imposed background flow with vertical shear in such simulations mesoscale organization appears naturally independent of the particulars of the initial condition as the magnitude of an imposed low level shear increases the convection becomes increasingly organized in lines or arcs propagating broadly downshear as predicted by earlier work when the shear is very strong the convection tends to organize into lines at an angle to the shear such that the line normal component is not far from its theoretical optimal value midlevel shear favors shear parallel lines but if it occurs in conjunction with sufficiently strong low level shear the convection can become very strongly organized into lines or arcs generally orthogonal to the low level shear optimal organization occurs when the depth of the shear layer is c

convection initiation by density currents role of convergence shear and dynamical organization abstract steady state analytic models establish two key points concerning the impact of vertical shear on density currents and the implication for convection initiation first shear decreases the horizontal convergence and therefore the mean ascent associated with downshear propagating currents second shear has a basic effect on the dynamical organization if the downshear current travels at the speed of the ambient flow at a critical steering level an overturning circulation provides deep lifting although mean ascent is increased by shear in the case of upshear propagating currents the lifting is comparatively shallow because jumplike ascent occurs rather than deep overturning the convection initiation mechanism involving the downshear current is therefore very different from the upshear case these basic principles are borne out in two dimensional numerical simulations density currents generated by a stationary cold source imposed on an initially horizontally homogeneous sheared and neutra

soil fertility and slope processes in the western cumberland escarpment of kentucky influences on the development of horticulture in the eastern woodlands the archaeological record of dry rockshelters in the red river valley of eastern kentucky contains botanical remains of several weedy annual seed bearing plants that point to the independent development of agriculture during the late archaic and early woodland period the objective of this study is to gather quantitative data through the chemical and physical analysis of soils collected within a valley transect to gain insights into landscape processes and soil fertility that may have played a role in the early development of plant domestication and the location of garden plots in relation to rock shelter sites in the upper cumberland plateau region of eastern kentucky soils on upland benches formed in limestones have soil fertility values that are comparable to fertile floodplain soils upslope outcrops of calcareous bedrock are contributing basic cations to these bench soils additionally in comparison to other landscape positions these upland soils have high levels of organic carbon available p and greater c n ratios soil morphology radiocarbon dates and archaeological evidence indicate that many of the numerous earthflows and debris flows within the region are early to middle holocene in age these slides were likely generated by mid holocene climatic shifts in which the frequency and intensity of summer precipitation increased across the southeastern united states these slope failures may have contributed to the development of plant domestication by creating forest canopy gaps and disturbed soils in which weedy plants thrived

multiscale convective wave disturbances in the tropics insights from a two dimensional cloud resolving model abstract multiscale convective wave disturbances with structures broadly resembling observed tropical waves are found to emerge spontaneously in a nonrotating two dimensional cloud model forced by uniform cooling to articulate the dynamics of these waves model outputs are objectively analyzed in a discrete truncated space consisting of three cloud types shallow convective deep convective and stratiform and three dynamical vertical wavelength bands model experiments confirm that diabatic processes in deep convective and stratiform regions are essential to the formation of multiscale convective wave patterns specifically upper level heating together with low level cooling serves to preferentially excite discrete horizontally propagating wave packets with roughly a full wavelength structure in troposphere and dry phase speeds cn in the range 16 18 m s 1 these wave packets enhance the triggering of new deep convective cloud systems via low level destabilization the new convection in turn caus

convection in gate the difficult problem of parameterizing tropical convection in large scale models of the atmosphere led to the global atmospheric research program s atlantic tropical experiment gate whose goal was to improve basic understanding of tropical convection and its role in the global atmospheric circulation a dense network of instrumented ships equipped with upper air sounding equipment and quantitative weather radars were located over the atlantic ocean in the intertropical convergence zone itcz just west of equatorial africa the ship network was supplemented by a fleet of research aircraft and a geosynchronous meteorological satellite the data obtained show that the deep convection in the itcz was concentrated in two types of cloud clusters rapidly moving squall clusters and slowly moving nonsquail clusters the clusters were characterized by large mid to upper level cloud shields or anvil clouds that emanated from penetrative cumulonimbus convection accompanying the deep cumulonimbus in each cluster was a log normal spectrum of smaller convective features ranging from moderate cumulonimbus down to tiny nonprecipitating cumulus the large cumulonimbus were typically grouped within a cluster into one or more mesoscale precipitation features or mpf s which were apparently triggered in mesoscale regions of intensified low level convergence as an mpf matured it developed a region of stratiform precipitation adjacent to its active deep convective cells the stratiform precipitation fell from the anvil cloud associated with the stratiform precipitation were a mesoscale downdraft below the anvil cloud and an apparent mesoscale updraft within the anvil cloud itself above the mesoscale downdraft these mesoscale drafts were distinct from the convective scale updrafts and downdrafts of the cumulus and cumulonimbus cells of the cluster downdrafts both convective scale and mesoscale filled the planetary boundary layer in the vicinity of cumulonimbus with stable air of low moist static energy these wakes of downdraft air exerted a strong control on where future convection broke out the results of gate show that to simulate the effects of tropical convection in large scale numerical models of the atmosphere a variety of phenomena must be accounted for including not only convective scale updrafts and downdrafts but anvil clouds with mesoscale updrafts and downdrafts downdraft induced boundary layer transformations and mesoscale convergence patterns experimentation with ways of including some of these features of tropical convection in large scale diagnostic and prognostic studies is under way but much work remains to be done

latent heating and mixing due to entrainment in tropical deep convection abstractrecent studies have noted the role of latent heating above the freezing level in reconciling riehl and malkus hot tower hypothesis hth with evidence of diluted tropical deep convective cores this study evaluates recent modifications to the hth through lagrangian trajectory analysis of deep convective cores in an idealized high resolution cloud resolving model crm simulation that uses a sophisticated two moment microphysical scheme a line of tropical convective cells develops within a finer nested grid whose boundary conditions are obtained from a large domain crm simulation approaching radiative convective equilibrium rce microphysical impacts on latent heating and equivalent potential temperature e are analyzed along trajectories ascending within convective regions of the high resolution nested grid changes in e along backward trajectories are partitioned into contributions from latent heating due to ice processes and a residual term that is shown to be an approximate representati

tomographic evidence for the mantle upwelling beneath southwestern japan and its implications for arc magmatism abstract the seismotectonics and volcanotectonics of southwestern sw japan have been affected by the subduction of the old pacific and the young philippine sea slabs we have attempted to determine the three dimensional p and s wave velocity structures of the upper mantle in sw japan by using a large amount of high quality arrival time data recorded by the dense seismograph network on the japanese islands to understand the tectonic framework of sw japan our results show the existence of a large low velocity anomaly below the philippine sea slab in the chugoku and shikoku districts at least down to depths of 300 km we infer that the low velocity zone is an upwelling flow from depth two shallower low velocity zones derived from this low velocity zone are detected one is toward the quaternary volcanoes in the chugoku district and the other is toward the uppermost mantle beneath the kii peninsula the former suggests that the magma for the quaternary volcanoes in the chugoku district is attributable to the upwelling flow in the upper mantle this idea supports the geochemical and petrological observations that the erupted alkalic basalt in the chugoku district should have originated from a more primitive or enriched mantle the latter is responsible for the absence of a high velocity anomaly corresponding to the subducted philippine sea slab beneath the kii peninsula the philippine sea slab could have been more hydrated locally beneath the kii peninsula than that in the surrounding regions by the interaction with the mantle upwelling consequently dehydration reactions could be involved during the progressive metamorphism accompanied by intensive intraslab seismicity lowering the seismic velocity in the slab aqueous fluids thus released to the overriding plate might be a possible source of mantle type helium and trigger a long term swarm activity in the crust of the overriding plate our results indicate the importance of the heterogeneous structure below the philippine sea slab with regard to the tectonics of sw japan

three dimensional seismic structure beneath southwest japan the subducting philippine sea plate abstract a three dimensional seismic structure beneath southwest japan has been investigated in detail by applying an inversion method this analysis clearly reveals the present and possibly the past subduction of the philippine sea plate beneath southwest japan beneath the izu peninsula the philippine sea plate does not appear to subduct but collides against the continental asian plate here and its thickness appears thinnest at most about 30 km from the tokai to the shikoku regions the high velocity zone corresponds well to the zone of subcrustal earthquakes down to a depth of about 60 70 km indicating that the subduction of the present philippine sea plate does not reach below this depth here however a small high velocity portion appears at depths between 100 km and 150 km beneath a part of the kinki region and probably extends to the chugoku region where no corresponding seismic activities exist these high velocities might be an indication of the remnants of the past subduction of the philippine sea plate in the kyushu region the high velocity zone continues down to a depth of about 150 km or even to 200 km in the southern part corresponding to a steeply inclined seismic zone the philippine sea plate in this region appears to be thicker than in regions east of the kyushu palau ridge it was also found that there exist narrow low velocity zones intervening within the philippine sea plate where two aseismic ridges the kyushu palau and shichito iwojima ridges extend northwards and the nankai trough shows warping these low velocity zones give support to the buoyant subduction hypothesis it also appears that lateral heterogeneities existing within and around the subducting plate are closely related to the mode of rupture of large earthquakes occurring around there

shear parallel mesoscale convective systems in a moist low inhibition mei yu front environment abstractnumerical simulations are performed to investigate organized convection observed in the asian summer monsoon and documented as a category of mesoscale convective systems mcss over the u s continent during the warm season in an idealized low inhibition and unidirectional shear environment of the mei yu moisture front the structure of the simulated organized convection is distinct from that occurring in the classical quasi two dimensional shear perpendicular and trailing stratiform ts mcs consisting of four airflow branches a three dimensional eastward propagating downshear tilted shear parallel mcs builds upshear by initiating new convection at its upstream end the weak cold pool in the low inhibition environment negligibly affects convection initiation whereas convectively generated gravity waves are vital upstream propagating gravity waves form a saturated or near saturated moist tongue and downstream propagating waves control the initiation and growth of convection within a pre

heat of fusion of basaltic magma abstract the heat of fusion of haplobasaltic liquids in the systems forsterite diopside sio2 and basaltic liquids in natural peridotite has been determined by high temperature solution calorimetry for liquids in the systems diopside anorthite and forsterite diopside anorthite the heat of fusion was calculated from literature data the heats of fusion for eutectic liquids in the system anorthite diopside and forsterite diopside anorthite for haplobasaltic liquid in equilibrium with olivine and two pyroxenes in the system forsterite diopside sio2 and for basaltic melts from natural peridotite parent are 130 6 121 1 157 4 and 161 5 cal g respectively the heat of mixing in the liquids contributes up to about 5 of this value the magnitude of this contribution increases when the structure of the endmember minerals is significantly different e g forsterite and anorthite or quartz the pressure effect on the heat of fusion results in a 10 20 increase in the pressure range 10 30 kbar compared with the 1 atm values this increase results from the larger compressibility of silicate liquids compared with that of the coexisting minerals in both model and natural compositions

magma ascent by porous flow porous flow of buoyant liquid through partially molten rock is regarded as the initial transport process leading to magma segregation in the mantle recent work has identified the importance of matrix deformation and compaction in this process we present finite difference calculations based on a generalized form of darcy s law that includes matrix deformation in two dimensional cartesian and cylindrical coordinates we emphasize the existence of solitary wave solutions called magmons these waves are regions of locally high porosity that ascend through regions of low uniform porosity they differ from diapirs where the liquid and matrix ascend together the one dimensional waves that were previously reported are found to be unstable in two dimensions breaking down to form two dimensional waves of circular cross section both the development of the instability and the form of the two dimensional waves are supported by theoretical analysis numerical experiments in which two dimensional waves collide show that the extent to which they are conserved after collision depends on the lateral offset of the waves the conservation can be very good in other cases larger waves appear to grow at the expense of smaller waves although the quantification of the relevant permeability and rheological parameters remains uncertain geophysically plausible estimates suggest wavelengths of kilometers and velocities of centimeters per year in our preliminary assessment of the relevance of these results to igneous processes we find that magmons are unlikely to be important in regions of broad upwelling such as beneath spreading centers here the transport of liquid adjusts to match the supply by melting and compaction processes are not important if liquid is supplied from below to a stable partially molten region of the asthenosphere it is expected to ascend in magmons this may occur beneath oceanic volcanic centers or in subcontinental mantle it is possible that magma ascent in magmons leads to spatial and temporal episodicity of volcanic activity if higher level processes do not obscure this influence the waveform of a magmon ascends faster than the liquid within the magmon so new liquid is taken in from above while original liquid is lost from below consequently magmons can mobilize small degrees of partial melt and deliver it rapidly to the surface

comments on tomographic evidence for the mantle upwelling beneath southwestern japan and its implications for arc magmatism by j nakajima and a hasegawa earth planet sci lett 254 2007 90 105 abstract based on tomographic images nakajima and hasegawa earth planet sci lett 254 2007 90 105 discussed that fluids derived from the stagnant pacific plate caused the back arc volcanisms in sw japan geochemical features of the volcanic products in sw japan however suggest that fluids dehydrated from the stagnant slab did not play a significant role in the magma genesis therefore discussions of nakajima and hasegawa should be revised

spatial variations in major u s hurricane activity statistics and a physical mechanism abstract the authors provide a statistical and physical basis for understanding regional variations in major hurricane activity along the u s coastline on long timescales current statistical models of hurricane activity are focused on the frequency of events over the entire north atlantic basin the exception is the lead author s previous work which models the occurrence of hurricanes over the caribbean sea gulf of mexico and the southeast u s coast separately here the authors use statistics to analyze data from historical and paleoclimatic records to expand this work in particular an inverse correlation in major hurricane activity across latitudes at various timescales is articulated when activity is above normal at high latitudes it tends to be below normal at low latitudes and vice versa past research paleoclimatic records and historical data hint at the potential of using the north atlantic oscillation nao as an indicator of where storms will likely track over long timescales an excite

reconstruction of prehistoric landfall frequencies of catastrophic hurricanes in northwestern florida from lake sediment records abstract sediment cores from western lake provide a 7000 yr record of coastal environmental changes and catastrophic hurricane landfalls along the gulf coast of the florida panhandle using hurricane opal as a modern analog we infer that overwash sand layers occurring near the center of the lake were caused by catastrophic hurricanes of category 4 or 5 intensity few catastrophic hurricanes struck the western lake area during two quiescent periods 3400 5000 and 0 1000 14 c yr b p the landfall probabilities increased dramatically to ca 0 5 per yr during an hyperactive period from 1000 3400 14 c yr b p especially in the first millennium a d the millennial scale variability in catastrophic hurricane landfalls along the gulf coast is probably controlled by shifts in the position of the jet stream and the bermuda high

a stagnation point flow model for melt extraction from a mantle plume we present a two dimensional dynamical model for melt extraction from a mantle plume mantle material rises at constant velocity wo until it reaches a depth at which melting begins the flow in the melt zone above this depth has the form of a stagnation point flow melt migrates through the unmelted matrix in response to the total nonhydrostatic pressure gradient which is the sum of contributions from the deformation of the matrix and the buoyancy of the melt melt extraction is modeled as a melt flux through the upper surface of the melt zone our main conclusions are as follows 1 the nonhydrostatic pressure gradient associated with the deformation of the matrix is small relative to the buoyancy of the melt everywhere within the melt zone and the melt migration within the plume obeys darcy s law the rate of melt extraction from a mantle plume is therefore controlled by the buoyancy and viscosity of the melt itself and not by the viscosity of the matrix 2 melt extraction from a plume occurs over an area comparable to that of the plume itself and about 60 80 of the melt generated within the plume is extracted both the geometry and rate of extraction predicted by the model are consistent with observations in the hawaiian islands 3 layers of segregated melt magma chambers are likely to form at the the base of the lithosphere under intraplate volcanoes

reinitiation of subduction and magmatic responses in sw japan during neogene time southwestern japan during paleogene time was affected by subduction of the kula and pacifi c plates beneath the eastern margin of eurasia followed by a brief episode of transform faulting to allow the shikoku basin to open at 27 15 ma subsequent opening of the japan sea back arc basin in middle miocene time broke japan away from eurasia and sw japan rotated clockwise 45o as it drifted south 17 15 ma southward drift required subduction of the philippine sea plate beneath sw japan leading to the formation of a magmatic arc subduction of the hot shikoku basin lithosphere and spreading ridge resulted in distinctive volcanism in the sw japan forearc between 17 and 12 ma this volcanism included midoceanic ridge basalt morb like intrusions and oceanic island basalt oib type alkali basalts felsic plutons in the accretionary prism and high magnesium andesites along the setouchi forearc basin mafi c magmas in the outermost forearc originated from the subducted shikoku basin spreading ridge whereas setouchi high magnesium andesites hma may have resulted from the interaction of melts of the subducted philippine sea plate with the overlying mantle felsic magmas in the forearc resulted from melting of shimanto belt sediments caused by intrusion of hma magmas persistent rear arc volcanism was caused by upwelling asthenosphere associated with opening of the sea of japan rear arc volcanism began ca 25 ma as rift fi ll low alkali tholeiite volcanism and was replaced gradually after 12 ma by alkali basalt volcanism upwelling related alkali volcanism continues up to the present whereas forearc volcanism ceased at 12 ma the volcanic arc narrowed with time as the philippine sea slab descended and slowly cooled adakitic dacites erupted after 1 7 ma above the 100 km depth contour of the subducted philippine sea plate suggesting that melting resulted from interaction of the slab with upwelling asthenosphere interactions between upwelled rear arc asthenosphere and subduction of the hot philippine sea slab appear to have been the main controls of magmatism for the neogene sw japan arc

simulation modeling and dynamically based parameterization of organized tropical convection for global climate models abstracta new approach for treating organized convection in global climate models gcms referred to as multiscale coherent structure parameterization mcsp introduces physical and dynamical effects of organized convection that are missing from contemporary parameterizations the effects of vertical shear are approximated by a nonlinear slantwise overturning model based on lagrangian conservation principles simulation of the april 2009 madden julian oscillation event during the year of tropical convection yotc over the indian ocean using the weather research and forecasting wrf model at 1 3 km grid spacing identifies self similar properties for squall lines mcss and superclusters embedded in equatorial waves the slantwise overturning model approximates this observed self similarity the large scale effects of mcsp are examined in two categories of gcm first large scale convective systems simulated in an aquaplanet model are approximated by slantwise overturning with attention to convective mome

mass flux characteristics of tropical cumulus clouds from wind profiler observations at darwin australia abstractcumulus parameterizations in weather and climate models frequently apply mass flux schemes in their description of tropical convection mass flux constitutes the product of the fractional area covered by convection in a model grid box and the vertical velocity in cumulus clouds however vertical velocities are difficult to observe on gcm scales making the evaluation of mass flux schemes difficult here the authors combine high temporal resolution observations of in cloud vertical velocities derived from a pair of wind profilers over two wet seasons at darwin with physical properties of precipitating clouds cloud top heights cth convective stratiform classification derived from the darwin c band polarimetric radar to provide estimates of cumulus mass flux and its constituents the length of this dataset allows for investigations of the contributions from different cumulus cloud types namely congestus deep and overshooting convection to the overall mass flux and of the influence of large

shear parallel tropical convective systems importance of cold pools and wind shear the impact of cold pools on line orientated convective systems is assessed using idealized simulations of tropical oceanic convection under weak moderate and strong wind shear regimes cold pools are weakened by suppressing evaporation in the shallow subcloud layer analysis of objectively identified convective systems reveals that the convection with weaker cold pools is more often oriented parallel rather than perpendicular to the wind shear the cold pool induced orientation changes are most pronounced in the strong shear environment interactions between convective orientation and the tropical atmosphere are assessed simulations with shear parallel convection demonstrate more top of atmosphere upwelling longwave radiation and less reflected shortwave radiation due to changes in convective anvils faster propagating larger scale gravity waves narrower cross shear moisture distributions and differences in convective momentum fluxes the results highlight critical interactions across convective scales mesoscales and climate scales as well as avenues for parameterizing structural modes of mesoscale organized convection in global models

two dimensional convection in non constant shear a model of mid latitude squall lines numerical simulations of two dimensional deep convection are analysed using analytical models extended to include shallow downdraughts and non constant shear the cumulonimbus are initiated by low level convergence created by a finite amplitude downdraught these experiments have constant low level shear and differ only in the profile of mid and upper level winds quasi steady convenction is produced if the mid and upper level flow has small shear and the low level shear is large the surface precipitation ismaximized for no intial relative relative flow aloft if stationary this storm p o can give prodigious locilized rainfall p o is the two dimentisonal equivalent of the supercell these results are placed in context with previous two dimensional simulations attention is drawn to the similiarity with previous two dimensional simulations attention is drawn to the similarity with squall lines in central and eastern u s a storm p o is analysed by construction of time averaged fields of streamfunction vorticity teperature and height deviation the smoothness of these fields suggests a conceptual model of the storm dynamics which involves cooperation between distinct charcteristic flows an overturning updraught a jump type updraught a shallow downdraught a low level rotor and a boundary layer an idealized analytical model is described by solution of the equations for steady convection these solutions for the remote flow are derived from energy conversation mass continuity and a momentum budget and they give relationships between the non dimensional parameteres of the problem it is apparent that the convection is a high froude or low richardson number flow demanding the existence of a cross storm pressure gradient inherent in this idealized model is a vortex sheet between updraught and down draught and it is considered that the dynamical instability of this sheet is related to complexities in the numerical simulation furthermore these results show that in two dimensions both non constant shear and a shallow downdraught are necessary to maintain steady convection

late quaternary paleoclimates and biotic responses in eastern north america and the western north atlantic ocean abstract broad scale late quaternary paleoclimatic changes are interpreted from palynological records across eastern north america and from assemblages of marine foraminifera in the western north atlantic ocean quantitative reconstructions of past dominance for major tree taxa at eight fossil pollen sites located south of the maximum glacial extent in the southeastern united states illustrate dramatic responses of tree populations to climatic change during the transition from pleistocene to holocene conditions a series of maps depicting changes in inferred boundaries of predominant airmasses during the late quaternary are based upon paleoclimatic interpretation of paleovegetation maps for eastern north america and climap maps of winter sea surface temperatures for the western north atlantic ocean in the eastern united states at 18 000 b p strong zonal circulation resulted in a fixed position of the atmospheric polar frontal zone along 33 n latitude the pacific airmass extended from 33 n latitude north to the southern margin of the laurentide ice sheet with the maritime tropical airmass dominating south of 33 n across the gulf coastal plain the gulf of mexico and the equatorial atlantic ocean the oceanic polar frontal zone extended northeastward from cape hatteras to 37 n in the western north atlantic ocean late glacial climatic amelioration was first reflected in vegetational changes south of the laurentide ice sheet beginning at 16 500 b p late glacial weakening in zonal atmospheric flow resulted in the penetration of the maritime tropical airmass farther to the north during the summer season increased summer warmth and rain produced substantial melting of the southern flank of the laurentide ice sheet the early holocene interval from 12 500 to 8 000 b p bracketed the time of maximum seasonality of solar radiation ca 11 000 b p during the early holocene enhanced meridional air flows resulted in increased seasonality of temperatures by 10 000 b p the oceanic polar frontal zone was displaced northward from the gulf stream anomalously cold maritime climatic conditions persisted along the central atlantic coast reflecting the position of the cold marine labrador current between the atlantic seaboard and the gulf stream during the mid holocene or hypsithermal interval from 8 000 to 4 000 b p prevailing westerlies expanded the midcontinental region of warmth and aridity for the last 4 000 years the modern climatic regime has been characterized by increased meridional flow

organized convection parameterization for the itcz abstractmesoscale convective systems mcss are of fundamental importance in the dynamics of the atmospheric circulation and the climate system they are often observed to develop over significant terrain in ambient shear flows in midlatitudes and embedded within the madden julian oscillation mjo and convectively coupled equatorial wave ccew envelopes as well as in the intertropical convergence zone itcz yet general circulation models gcms fail to resolve these systems and their underlying convective parameterizations are not directed to represent organized circulations shear parallel mcss which are common in the itcz have a three dimensional structure and as such present a serious modeling challenge here a previously developed multicloud model mcm is modified to parameterize mcss one of the main modifications is the parameterization of stratiform condensation to capture extended stratiform outflows which characterize mcss resulting from strong upper level jets linear analysis show

quaternary deposits and landscape evolution of the central blue ridge of virginia abstract a catastrophic storm that struck the central virginia blue ridge mountains in june 1995 delivered over 775 mm 30 5 in of rain in 16 h the deluge triggered more than 1000 slope failures and stream channels and debris fans were deeply incised exposing the stratigraphy of earlier mass movement and fluvial deposits the synthesis of data obtained from detailed pollen studies and 39 radiometrically dated surficial deposits in the rapidan basin gives new insights into quaternary climatic change and landscape evolution of the central blue ridge mountains the oldest depositional landforms in the study area are fluvial terraces their deposits have weathering characteristics similar to both early pleistocene and late tertiary terrace surfaces located near the fall zone of virginia terraces of similar ages are also present in nearby basins and suggest regional incision of streams in the area since early pleistocene late tertiary time the oldest debris flow deposits in the study area are much older than wisconsinan glaciation as indicated by 2 5yr colors thick argillic horizons and fully disintegrated granitic cobbles radiocarbon dating indicates that debris flow activity since 25 000 ybp has recurred on average at least every 2500 years the presence of stratified slope deposits emplaced from 27 410 through 15 800 ybp indicates hillslope stripping and reduced vegetation cover on upland slopes during the wisconsinan glacial maximum regolith generated from mechanical weathering during the pleistocene collected in low order stream channels and was episodically delivered to the valley floor by debris flows debris fans prograded onto flood plains during the late pleistocene but have been incised by holocene stream entrenchment the fan incision allows holocene debris flows to largely bypass many of the higher elevation debris fan surfaces and deposit onto the topographically lower surfaces these episodic high magnitude storm events are responsible for transporting approximately half of the sediment from high gradient low order drainage basins to debris fans and flood plains

gregarious tropical convection abstract a beat source with a vertical profile like that of observed tropical mesoscale convective systems mcss is shown to cause through inviscid gravity wave dynamics upward displacement at low levels in a mesoscale region surrounding the heating typical values are 10 30 area contraction at the surface everywhere within 270 km of the heating 6 h after it starts as a result conditions near an existing mcs but beyond the area of mcs outflow become more favorable for the development of additional convection this theory predicts that cloud clusters should be gregarious infrared satellite imagery confirms that almost half of the cold cloudiness observed in a month over the oceanic warm pool region was contributed by just 14 objectively defined multiday supercluters

zonal structure of cenozoic basalts related to mantle upwelling in southwest japan cenozoic olivine bearing basaltic rocks in the central chugoku district form eight provinces each 20 to 30 km in diameter these provinces can be grouped into three zones almost parallel to the elongation of the sw japan arc based on geological and petrological characteristics the san yo zone the closest to the nankai trough is characterized by a small amount of alkaline basalt in the sekiryo zone intermediate zone transitional basalt is dominant the san in zone along the japan sea coast is characterized by subalkaline basalt and a large amount of andesitic rocks the eruption volume of these volcanics exponentially increases toward the back arc side less than 1 km3 to more than 100 km3 chemical compositions of relatively undifferentiated basalts show systematic across arc variations sio2 and al2o3increase and feo mgo and cao decrease toward the back arc side 44 to 54 13 to 18 11 to 6 13 to 7 and 12 to 8 wt at feo mgo 0 85 respectively melting experiments on the basalt h2o co2 systems show that the pressure and temperature of magma segregation decrease toward the back arc side 17 19 kbar and 1340 1320 c to 8 kbar and 1250 c and the coexisting phases change from a spinel lherzolite assemblage to a harzburgite assemblage these pt conditions define a trend which can be interpreted as a pt path for adiabatic upwelling of the mantle material consequently the observed volcanism and zonation may have been caused by upwelling of a plume from a deep part of the mantle

geomorphological controls on soil fertility of semi arid alluvial fans a case study of the joghatay mountains northeast iran abstract alluvial fans are ideal locations to examine the effect of geomorphic processes and landforms on the soil characteristics the rate of soil development and fertility differs between active surfaces exposed to aggradation and old or relict surfaces subject to degradation the aim of this research is to evaluate the effect of landforms and processes on soil fertility based on the studies on three alluvial fans of different ages relict old and young a total of 36 soil samples were collected from these three alluvial fan surfaces the samples were gathered from different locations of fans apex and toe and landforms gully beds interfluves swales and bars and for each sample nine variables including soil texture acidity ph electrical conductivity ec total neutralizing value tnv available phosphorus ap available potassium ak total nitrogen tn total organic carbon toc and hydraulic conductivity k were measured the results show that the values of tnv ap ak tn and toc increase as clay increases in the relict and old fans the values of tnv toc tn ap ak clay and silt are higher in the interfluves than in the gully beds also in the relict and old fans the rates of clay silt toc tn and ap are higher in the apexes than in the toes in the young fan the values of most variables are higher in the toe compared to the apex the wide and relatively flat interfluves of the apex of old and relict fans have soils that are more fertile compared to the extensively entrenched surfaces of relict and old fan toes with relatively steep sloped interfluves the less fertile soils in the apex of young fan can be attributed to its coarse textured soils and also to repeated flooding and depositional processes overall this study reveals that geomorphological landforms and processes such as aggradation and degradation play an important role in the spatial variation of soil fertility