simultaneous thin section and phytolith observations of finely stratified deposits from neolithic catalhoyuk turkey implications for paleoeconomy and early holocene paleoenvironment simultaneous thin section and phytolith observations of finely stratified anthropogenic deposits from the neolithic settlement of catalhoyuk turkey dated between 7400 and 6000 bc provide evidence for both the depositional context and phytolith assemblage of these deposits although extracted phytoliths provide a general picture of vegetation that supports existing evidence of a local wet marshland environment comparisons with observations of phytoliths in situ indicate a diverse range of microcontexts as well as depositional and post depositional processes that influence phytolith size this has implications for studies that use conjoined phytolith size as a proxy for water availability and early agricultural practices observations indicate a significant background noise of phytoliths and micro charcoal in the deposits linked to the frequent use of fire which has implications for interpreting assemblages where phytolith counts are low such as from floors of buildings this study confirms the usefulness of phytoliths in providing information on human plant use and environment where the taphonomy of the deposits is clear and provides new evidence for wet farming of at least some of the wheat found at the site it also suggests there needs to be greater consideration of phytolith taphonomy which can be provided to an extent by combining phytolith analysis with thin section micromorphology copyright 2011 john wiley sons ltd

late quaternary climates of the australian arid zone a review abstract aridity in australia has generally been associated with glacial intervals of the last few glacial cycles the causes and nature of aridity varied from north to south over the continent in northern and central australia reduced monsoon rain in global cold stages caused lakes and rivers to dry vegetation to become more sparse sand dunes to become active and dust advection to increase while the monsoon is correlated with warmer global temperatures and high sea levels overall the exact timing of the greatest development of the monsoon in stage 5 remains uncertain in southeastern australia the proxy records give a less clear picture while vegetation seems to have been more sparse in cold stages and sand dune activity and dust flux consequently greater records of runoff in rivers and lakes have mixed or opposite behaviour to northern or central australia the nature of aridity in southeastern australia is not analogous to conditions anywhere on the continent today greatly reduced temperatures over the central and southern interior greater influence of snow and periglaciation on runoff high groundwater tables lower rainfall and reduced atmospheric carbon dioxide levels may all have contributed to and interacted to produce the reconstructed picture of a cold sparsely vegetated arid landscape with large rivers and perennial lakes the largest changes in circulation patterns over the glacial cycle probably occurred in the location and or intensity of summer tropical convergence in northern australia over southern australia changes to the temperature and humidity of the westerly circulation have been more significant than the small fluctuations in latitude of the sub tropical high pressure ridge

structure of a midtropospheric vortex induced by a mesoscale convective system on 9 june 1988 a mesoscale 200 km diameter convectively generated vortex mcv passed through the colorado wind profiling network the generating convective system which was too small to meet maddox s mesoscale convective complex criteria developed beneath a high amplitude mid and upper level ridge axis profiler winds obtained within the stratiform region of the convective system and near the center of the ensuing mcv form the basis of this study with the addition of satellite including rapid scan images and conventional and doppler radar data this vortex was well observed over its entire life cycle the slowly moving vortex was observed by the flagler 50 mhz profiler for more than 16 h for a portion of this period the circulation was quasi steady hence the spatial structure of the vortex was depicted by timeto space conversion of the profiler data the results show a strong coherent circulation with maximum tangential speeds greater than 16 m s21 at 6 km above mean sea level msl and at radii of 50 70 km corresponding relative vorticity was more than three times as large as the local coriolis parameter the long duration and the apparent dominance of vorticity over divergence suggest that the flow in the vortex was in a quasi balanced state hence the temperature perturbation necessary to support the tangential velocity distribution was computed assuming gradient balance in the radial direction the resulting estimated temperature structure showed a warm core with a magnitude of 2 38c at 7 3 km msl and a cold core below 6 3 km msl the associated potential vorticity pv structure at the vortex center consisted of a lens of high pv with a maximum at 6 3 km msl and relative minima above and below this height

genesis of tropical storm eugene 2005 from merging vortices associated with itcz breakdowns part i observational and modeling analyses abstract although tropical cyclogenesis occurs over all tropical warm ocean basins the eastern pacific appears to have the highest frequency of tropical cyclogenesis events per unit area in this study tropical cyclogenesis from merging mesoscale convective vortices mcvs associated with breakdowns of the intertropical convergence zone itcz is examined this is achieved through a case study of the processes leading to the genesis of tropical storm eugene 2005 over the eastern pacific using the national centers for environmental prediction reanalysis satellite data and 4 day multinested cloud resolving simulations with the weather research and forecast wrf model at the finest grid size of 1 33 km observational analyses reveal the initiations of two mcvs on the eastern ends of the itcz breakdowns that occurred more than 2 days and 1000 km apart the wrf model reproduces their different movements intensity and size changes and vortex vortex interaction at nearly the right timing and location at

mechanisms for quasi stationary behavior in simulated heavy rain producing convective systems abstract in this study idealized numerical simulations are used to identify the processes responsible for initiating organizing and maintaining quasi stationary convective systems that produce locally extreme rainfall amounts of particular interest are those convective systems that have been observed to occur near mesoscale convective vortices mcvs and other midlevel circulations to simulate the lifting associated with such circulations a low level momentum forcing is applied to an initial state that is representative of observed extreme rain events the initial vertical wind profile includes a sharp reversal of the vertical wind shear with height indicative of observed low level jets deep moist convection initiates within the region of mesoscale lifting and the resulting convective system replicates many of the features of observed systems the low level thermodynamic environment is nearly saturated which is not conducive to the production of a strong surface cold pool yet the convection qui

convection in an african easterly wave over west africa and the eastern atlantic a model case study of helene 2006 convective systems embedded in an african easterly wave aew over west africa and the eastern atlantic in september 2006 are investigated the study is based on cosmo model runs with a horizontal resolution of 2 8 km the developing mature and decaying phases of a mesoscale convective system over land are identified over the ocean the convection consists of the development and decay of short lived systems there are significant differences between the structure of convection over land and water over land the updraught heating and vertical vorticity are tilted in the vertical over water the convective cores are upright and collocated with positive relative vorticity the atmosphere is drier at mid levels over land and stronger shear downdraughts and a distinct cold pool occur the influence of the convective systems on their environment is assessed with potential temperature and relative vorticity budgets for regions encompassing the convective systems during the convective system s life cycle the relative vorticity increased at the height of the african easterly jet over land due to the eddy flux term whereas the relative vorticity maximum over the ocean moved downwards with time due to stretching high values of low level relative vorticity were seen over the ocean before the aew trough crossed the west african coast the low level circulation that developed as a positive low level vorticity anomaly associated with the westward extension of the saharan heat low moved over the atlantic and southwestwards in addition positive vorticity associated with the low level monsoon flow contributed to this circulation the cyclogenesis of hurricane helene was initiated when the mid level vorticity anomaly of the aew moved over the low level circulation initiating convection and enhancing the low level vorticity through vortex stretching copyright 2010 royal meteorological society

phytolith taphonomy and distributions in archeological sediments from panama abstract this paper presents the results of research into the nature distribution and significance of phytoliths in archeological sediments from panama four sites are investigated that span a time period dated by radiocarbon from 6600 bc to ad 500 and which encompass a range of human adaptations and ecological settings the strengths and limitations of phytolith analysis are evaluated in relation to a diverse set of paleoecological issues the results indicate that panamanian archeological deposits contribute silicified structures from a large number of plant taxa phytoliths appear to be horizontally and vertically stable after deposition there are problems in human paleoecology such as the evolution of root cropping systems that are not amenable to study with phytolith data however a considerable amount of information can be generated about some components of prehistoric seed cropping systems wild plant usage and landforms

the vertical structure of mesoscale convective vortices abstract simulations of two cases of developing mesoscale convective vortices mcvs are examined to determine the dynamics governing the origin and vertical structure of these features although one case evolves in strong vertical wind shear and the other evolves in modest shear the evolutions are remarkably similar in addition to the well known mesoscale convergence that spins up vorticity in the midtroposphere the generation of vorticity in the lower troposphere occurs along the convergent outflow boundary of the parent mesoscale convective system mcs lateral transport of this vorticity from the convective region back beneath the midtropospheric vorticity center is important for obtaining a deep column of cyclonic vorticity however this behavior would be only transient without a secondary phase of vorticity growth in the lower troposphere that results from a radical change in the divergence profile favoring lower tropospheric convergence following the decay of the nocturnal mcs subsequent con

reconnaissance studies of the tufa deposits of the napier range n w australia tufas are widespread in the napier range of north western australia an area of tropical seasonal climate and savanna vegetation the major tufa deposits have been mapped and the different forms described these include drapes on cliffs cones at cave entrances or the mouths of ephemeral streams rimstone pools and tufa dams there are at least two generations of tufa cone with the older being heavily calcreted and eroded simple geochemical and petrographical data allow comparison between the different types of deposit here and with deposits from other parts of the world thin section observations and scanning electron microscopy enable an initial assessment of the role of organic processes in tufa formation obvious organic remains are sparse although many of the active tufas are composed of filamentous microsparite fabrics suggesting that algae have influenced the geometry of the deposits however the identification of various endolithic algae indicates that they may also be actively involved in the degradation of the deposits

impacts of increasing low level shear on supercells during the early evening transition abstractthe dynamical response of simulated supercells to temporally increasing lower tropospheric vertical wind shear is investigated using idealized simulations these simulations are based upon observed soundings from two cases that underwent an early evening transition during the second verification of the origins of rotation in tornadoes experiment vortex2 mature supercells were simulated in observed afternoon environments with moderate vertical wind shear and then compared to simulated supercells experiencing observed evening increases in lower tropospheric shear the primary effect of the increase in low level shear is to establish larger values of vertical vorticity at lower altitudes in the storm s updraft in turn this leads to a nonlinear increase in the updraft strength due to the enhanced dynamic pressure minimum associated with larger vorticity in the storm s mesocyclone this is particularly important at low levels where it increases the storm s ability to lift cool surface air includ

analysis of a small vigorous mesoscale convective system in a low shear environment part ii evolution of the stratiform precipitation and mesoscale flows abstract the evolution of the mesoscale flow and precipitation distribution are investigated for a small mesoscale convective system mcs that evolved in a nearly barotropic environment exhibiting moderate instability and weak wind shear observations primarily from a single doppler radar detail the growth of the mcs from the merger of several clusters and lines of vigorous convective cells into a mature state consisting of a weaker convective line trailed by an expanding stratiform precipitation region analysis of radar reflectivity reveals that this stratiform region formed in situ in the presence of weak mesoscale updraft as decaying convective cores coalesced rather than through rearward advection of ice particles directly from the convective region in the absence of sufficient low level shear the mcs collapsed rapidly as it assumed the structure of the archetypal convective line and trailing stratiform precipitation region velocity azimuth displays reveal mesoscale updrafts of about 70 cm s 1 d

environmental history of northwest australia based on phytolith analysis at carpenter s gap 1 examination of a phytolith assemblage from the archaeological site of carpenter s gap 1 provides an hitherto unrecognised source of vegetation history for the tropical savannah region of north western australia two predominant mechanisms contributed to the formation of the phytolith assemblage firstly the introduction of phytoliths in plant materials brought in by humans and secondly the introduction of phytoliths contained in faecal pellets deposited by animals separating the effects of both mechanisms enables local vegetation patterns and by inference climatic conditions to be reconstructed the period ca 40 000 years bp was probably wetter than today allowing the southerly expansion of palms beyond their present day distribution grassland compositional changes occurred by ca 33 000 years bp probably resulting from a combination of lowered rainfall decreased temperatures and possibly aboriginal firing activities a reduction in palm at a similar time followed by its complete disappearance in association with the loss of ulmaceae prior to the last glacial maximum lgm indicates a continued trend in decreasing water availability an abundance of cyperaceae sponge spicules and diatoms during the lgm when considered in conjunction with the other evidence possibly represents altered human behaviour in response to increased aridity

convective contribution to the genesis of hurricane ophelia 2005 abstract the convection occurring in the tropical depression that became hurricane ophelia 2005 was investigated just prior to tropical storm formation doppler radar showed a deep wide intense convective cell of a type that has been previously thought to occur in intensifying tropical depressions but has not heretofore been documented in detail the updraft of the cell was 10 km wide 17 km deep had updrafts of 10 20 m s 1 throughout its mid to upper levels and contained a cyclonic vorticity maximum the massive convective updraft was maintained by strong positive buoyancy which was maximum at about the 10 km level probably aided by latent heat of freezing evaporative cooling and precipitation drag occurred in the rain shower of the cell but were insufficient to produce a strong downdraft or gust front outflow to force the updraft the convective updraft was fed by a layer of strong inflow that was several kilometers deep wind induced turbulence just above the ocean surface enriched the equi

the propagation and diurnal cycles of deep convection in northern tropical africa the propagation and diurnal cycle of organized convection in northern tropical africa are examined using five years 1999 2003 of digital infrared imagery for may august reduced dimension techniques are used to document the properties of cold clouds proxies for deep convection and precipitation large scale environments are diagnosed from global analyses organized convection in africa consists of coherent sequences or episodes which span an average distance of about 1000 km and last about 25 h a substantial fraction of events exhibits systematic propagation at regional to continental scales while undergoing decay and regeneration episodes with 36 h duration and 1472 km span recur at a one per day interval most episodes have phase speed of 10 20 m s 1 which is faster than most african easterly waves convective episodes tend to initiate in the lee of high terrain consistent with thermal forcing from elevated heat sources average diurnal frequency maxima result from the superposition of local diurnal maximum with the delayed phase arrival of systems propagating from the east propagation occurs with moderate low to mid tropospheric shear which varies with the african easterly jet migration and west african monsoon phases frequent deep convection occurs with local shear maxima near high terrain for the peak monsoon period and for 10 w 10 e where easterly waves and convective systems are frequent 35 of cold cloud episodes occur east of the wave trough compared with about 24 to the west based on the coherent behaviour of organized propagating convection inferences may be made regarding the prediction of precipitation beyond one or two days copyright 2008 royal meteorological society

the formation of hurricane humberto 2001 the importance of extra tropical precursors the authors examine the formation of hurricane humberto 2001 in the atlantic basin precursor disturbances originating in the extratropics appear critical for inducing tropical cyclogenesis one precursor near the tropopause arose during the development of hurricane erin on 7 september and could be tracked continuously for 12 days until 1200 utc 19 september a fully explicit numerical simulation with the psu ncar mesoscale model produces a generally realistic evolution of the developing storm during a 4 day period beginning 0000 utc 19 september diagnostics of the simulations reveal that moderate vertical shear was crucial for organizing convection and this shear was enhanced on the periphery of an upper level vortex within a lower to mid tropospheric baroclinic zone downdraughts and evaporative cooling produced a rearward propagating bore that organized new convection in a notably moistened environment with small cape vorticity generation maximized near 1 km above mean sea level and the vortex built upward with time this evolution contrasts markedly with downward development conceptual models of tropical cyclogenesis and points to the crucial need for observations in the lower troposphere before depression formation convective scale dynamics were governed by intense convective cores which produced most of the diabatic heating and lower tropospheric vertical vorticity they were constrained by vertical shear to populate the downshear left quadrant of the vortex and therefore their collective behaviour was organized despite being quasi random within the favoured region ultimately the shear that helped organize the convection in the developing depression hampered humberto s subsequent intensification copyright 2006 royal meteorological society

the vertical vorticity structure within a squall line observed during bamex banded vorticity features and the evolution of a bowing segment abstracta quasi linear convective line with a trailing stratiform region developed during the bow echo and mesoscale convective vortex experiment bamex while being sampled by two airborne doppler radars the finescale reflectivity and doppler velocities recorded by the radars documented the evolution of the convective line bands of positive and negative vertical vorticity oriented parallel to the convective line were resolved in the analysis this type of structure has rarely been reported in the literature and appears to be a result of the tilting and subsequent stretching of ambient horizontal vorticity produced by the low level wind shear vector with a significant along line component the radar analysis also documented the evolution of an embedded bow echo within the convective line embedded bow echoes have been documented for a number of years however a detailed analysis of their kinematic structure has not been previously reported in the literature the counterrotating circulation patterns tha

interactions between a developing mesoscale convective system and its environment part ii numerical simulation the 19 july 1993 mesoscale convective system mcs discussed in part i was simulated using the regional atmospheric modeling system rams the model was initialized with variable physiographic and atmospheric data with the goal of reproducing the convective system and its four dimensional environment four telescopically nested moving grids allowed for horizontal grid spacings down to 1 67 km on the cloud resolving grid comparisons with the analysis show that the propagation evolution and structure of this mcs were well simulated the simulation is used to further investigate the interactions between this mcs and its surrounding environment in part i the doppler derived winds indicated that upshear westward propagating gravity waves left uppertropospheric front to rear and midtropospheric rear to front flow perturbations in their wake a similar flow structure developed in the simulated mcs and unlike the doppler results the low frequency waves that produced it were resolved in the data in the simulation much of the convectively generated temperature and momentum perturbations propagated westward with the waves leaving a warm wake in the clear air trailing the system although the gravity waves traveled rearward the perturbation flow in their wake was not strong enough to reverse the upper tropospheric storm relative winds thus most of the anvil condensate advected ahead of the convective line as the mcs encountered the low level jet the midtropospheric upward mass flux increased but gravity wave motions became less detectable the upper tropospheric anvil pushed westward into the strong flow as the system expanded into a characteristically oval shape temperature and momentum perturbations propagated rearward along with the anvil in a disturbance that resembled an advective outflow unlike the gravity waves this disturbance became almost stationary with respect to the ground and it retained its continuity through the rest of the simulation vertical cross sections indicate that a large slab of convectively processed air had detrained into the upper troposphere prior to this event much of the warm temperature anomalies generated within the convective towers either remained in the updrafts or propagated outward with the gravity waves early on individual updrafts were relatively erect and although condensate did detrain eastward in the forward anvil the temperature anomalies did not propagate with it in contrast convective updrafts associated with the expanding oval anvil disturbance were more continuous and they tilted strongly westward with height

mesoscale convective vortices observed during bamex part i kinematic and thermodynamic structure abstract five cases of mesoscale convective vortices mcvs are described from observations collected during the bow echo and mcv experiment bamex over the central united states during the period from 20 may to 6 july 2003 in the present paper the kinematic and thermodynamic structure of each vortex and its environment are emphasized data consist of bamex dropsondes the national oceanic and atmospheric administration profiler network and national weather service soundings in addition weather surveillance radar 1988 doppler observations documented the signatures of nascent mcvs within nocturnal convection systems as well as the spatial pattern of convection within mcvs during the following day the vertical structure of each vortex was highly dependent on the vertical shear and the presence of upper tropospheric cyclonic vorticity anomalies in strong shear a pronounced downshear tilt of the vortex was evident but with the presence of an upper tropospheric trough the tilt was upshear in the upp

influence of balanced motions on heavy precipitation within a long lived convectively generated vortex abstract the forcing of heavy precipitation within a long lived convectively generated mesoscale vortex mcv is investigated with the aid of diagnoses from rapid update cycle gridded analyses organized convection within the mcv followed a distinct diurnal cycle which featured organized mesoscale convective systems mcss that matured overnight near the mcv center on successive days the mcv was typically most intense in the middle troposphere but intensified within the lower troposphere during the episodes of organized nocturnal convection the lower tropospheric vertical shear was an important organizing factor in mcs development and sustenance in the sense that its interaction with the cold temperature anomaly beneath the mcv center determined where balanced lower tropospheric ascent occurred from trajectory analyses we estimate that balanced ascent accounted for approximately half of the total vertical displacement of the thermodynamically unstable air that eventually composed elevated saturated

the variable nature of convection in the tropics and subtropics a legacy of 16 years of the tropical rainfall measuring mission satellite for over 16 years the precipitation radar of the tropical rainfall measuring mission trmm satellite detected the three dimensional structure of significantly precipitating clouds in the tropics and subtropics this paper reviews and synthesizes studies using the trmm radar data to present a global picture of the variation of convection throughout low latitudes the multiyear data set shows convection varying not only in amount but also in its very nature across the oceans continents islands and mountain ranges of the tropics and subtropics shallow isolated raining clouds are overwhelmingly an oceanic phenomenon extremely deep and intense convective elements occur almost exclusively over land upscale growth of convection into mesoscale systems takes a variety of forms oceanic cloud systems generally have less intense embedded convection but can form very wide stratiform regions continental mesoscale systems often have more intense embedded convection some of the most intense convective cells and mesoscale systems occur near the great mountain ranges of low latitudes the maritime continent and amazonia exhibit convective clouds with maritime characteristics although they are partially or wholly land convective systems containing broad stratiform areas manifest most strongly over oceans the stratiform precipitation occurs in various forms often it occurs as quasi uniform precipitation with strong melting layers connected with intense convection in monsoons and the intertropical convergence zone it takes the form of closely packed weak convective elements where fronts extend into the subtropics broad stratiform regions are larger and have lower and sloping melting layers related to the baroclinic origin of the precipitation

a climatology of midlatitude mesoscale convective vortices in the rapid update cycle abstract climatological characteristics of mesoscale convective vortices mcvs occurring in the state of oklahoma during the late spring and summer of four years are investigated the mcv cases are selected based on vortex detection by an objective algorithm operating on analyses from the rapid update cycle ruc model consistent with a previous study true mcvs represent only about 20 of the mesoscale relative vorticity maxima detected by the algorithm the mcvs have a broad range of radii and intensities and their longevities range between 1 and 54 h their median radius is about 200 km and their median midlevel relative vorticity is 1 2 10 4 s 1 there appears to be no significant relationship between mcv longevity and intensity similar to past estimates approximately 40 of the mcvs generate secondary convection within their circulations the mean synoptic scale mcv environment is determined by the use of a ruc based composite analysis at four different stages in the mcv life cycle defined b

warm core vortex amplification over land abstract a convectively generated mesoscale vortex that was instrumental in initiating and organizing five successive mesoscale convective systems over a period of three days is documented two of these convective systems were especially intense and resulted in widespread heavy rain with localized flooding based upon radar and satellite data the detectable size of the vortex became much larger following the strong convective developments nearly tripling its initial diameter over its three day life cycle during nighttime when convection typically intensified within the vortex movement of the system tended to slow following dissipation of the convection in the morning the daytime movement accelerated cross sections of potential vorticity taken through the vortex center clearly show a maximum at midlevels and a well defined minimum directly above the vortex and the potential vorticity maximum were essentially colocated and the system was nearly axisymmetric in the vertical over the three day life

patterns of precipitation and mesolow evolution in midlatitude mesoscale convective vortices abstract surface pressure manifestations of mesoscale convective vortices mcvs that traversed oklahoma during the periods may august 2002 05 are studied using the weather surveillance radar 1988 doppler wsr 88d the oklahoma mesonet and the noaa profiler network data forty five mcvs that developed from mesoscale convective systems mcss have been investigated 28 62 of which exhibit mesolows detectable at the surface within this group three distinct patterns of precipitation organization and associated mesolow evolution have been identified the remaining 17 38 of the cases do not contain a surface mesolow two repeating patterns of precipitation organization are identified for the latter group the three categories of mcvs possessing a surface mesolow are as follows nineteen are classified as rear inflow jet mcvs and tend to form within large and intense asymmetric mcss rear inflow into the mcs enhanced by the development of an mcv on the left hand side relative to system motion pro

diurnal evolution and structure of long lived mesoscale convective vortices along the mei yu front over the east china plains abstractthe structure and diurnal evolution of long lived eastward propagating mesoscale convective vortices mcvs along typical summertime mei yu fronts over the east china plains are investigat

detection and prediction of warm season midtropospheric vortices by the rapid update cycle the authors perform a statistical and dynamical analysis of midtropospheric mesoscale vortices captured by analyses from the rapid update cycle version 2 ruc 2 during the period 1 may to 31 august 1999 a total of 203 vortices meeting conditions of an automated algorithm were found of these 86 were observed to form within organized convection and were termed mesoscale convective vortices mcvs mcvs were favored over a broad area from eastern colorado and western nebraska to the mississippi river valley essentially collocated with the loci of organized convection the remaining 117 vortices termed dry vortices clustered in the immediate lee of the rocky mountains and over the southeastern united states vortices arising from convection had considerably greater intensity and longevity than dry vortices they were roughly five times more likely to be involved with the triggering of new convection a relationship was found between intensity and longevity such that there appears to be a maximum vortex lifetime that can be estimated from its maximum intensity vortices arising from convection had markedly greater humidity and water vapor mixing ratio underneath their centers compared to dry vortices consistent with many dry vortices having a topographic origin and mcvs arising from organized convection parameters such as horizontal scale background vertical wind shear and horizontal deformation were not systematically related to intensity or longevity prediction of mesoscale vortices by the ruc 2 was examined for a subsample of all cases in general the ruc 2 was able to predict the evolution of vortices once analyzed but had virtually no skill at predicting 12 h in advance the formation of the vortices however forecasts of organized convection should still benefit from accurate predictions of long lived vortex tracks

in search of regional palaeoclimates australia 18 000 yr bp abstract this paper continues the investigation of regional palaeoclimates in australia at 18 000 yr b p using the method set out in hubbard 1995 initial research showed that while the palaeodata were on the whole in keeping with climates retrodicted for the northern part of the continent there was substantial disagreement between the data and retrodictions in the south of australia while several possible reasons for this disagreement are considered in this paper it is the author s conclusion that the 18 000 yr b p run of the community climate model placed the southern boundary of the mid latitude belt of high pressure south of its actual position new seasonal circulations based on a northward position of this belt are outlined in this paper and using the method given in hubbard ibid new climate retrodictions are given for each of 12 australian regions these new retrodictions are almost entirely in keeping with the published data review suggesting that the community climate model 0 run pressure results were incorrect the revised seasonal circulation patterns can be used therefore to reconstruct likely palaeoclimates of regions that currently have few or no palaeoclimatic data

phytolith evidence for c4 dominated grassland since the early holocene at long pocket northeast queensland australia abstract preliminary phytolith analysis of ephemeral lake fill sediment at long pocket near toomba northeast queensland australia indicates that a c4 dominated grassland with a minor woody component has been present in the region since ca 8000 cal yr b p based on the modern distribution of c4 and c3 native grasses in australia this suggests that mean summer temperatures of at least 14 c ca 10 c cooler than present were maintained since the early holocene this interpretation is comparable with previous studies which together imply that the establishment of c4 dominated grasses in central and northeast australia occurred between the last glacial maximum most likely after ca 16 000 14 c yr b p and ca 7200 14 c yr b p ca 8000 cal yr b p taxonomic composition of the grassland appears relatively consistent since the early holocene at long pocket and includes phytoliths comparable with those from modern arundinoideae panicoideae and chloridoideae rare non grass phytoliths are also present a gradual decrease in abundance of saddle phytolith forms attributed to chloridoideae grasses from the base of the record at ca 6500 7000 cal yr b p suggests decreasing aridity throughout the holocene this trend could reflect a locally drawn out effect of the end of the postglacial arid period due to the well drained basalt flow catchment maintaining a local arid habitat for the chloridoideae grasses

late quaternary landscapes in central australia sedimentary history and palaeoecology of puritjarra rock shelter puritjarra rock shelter provides a long record of late quaternary vegetation in the australian arid zone analysis of the sedimentary history of this rock shelter is combined with reanalysis of charcoal and phytolith records to provide a first order picture of changing landscapes in western central australia these show a landscape responding to increasing aridity from 45 ka with deflation of clay rich red palaeosols 45 ka and sharp declines in grassland and other vegetation at 40 36 ka and at the beginning of the last glacial maximum lgm 24 ka vegetation in the catchment of the rock shelter recovered after 15 ka with expansion of both acacia woodland and spinifex grasslands registering stronger summer rainfall in the interior of the continent by 8 3 ka re vegetation of local palaeosols and dunes had choked off sediment supply to the rock shelter and the character of the sediments changed abruptly poaceae values peaked at 5 8 ka suggesting the early mid holocene climatic optimum in central australia is bracketed between 8 3 and 5 8 ka local vegetation was disrupted in the late holocene with a sharp decline in poaceae at 3 8 ka coinciding with an abrupt intensification of enso local grasslands recovered over the next two millennia and by 1 5 ka the modern vegetation appears to have become established copyright 2009 john wiley sons ltd

long lived mesoconvective vortices and their environment part ii induced thermodynamic destabilization in idealized simulations abstract idealized numerical simulations are used to quantify the effect of quasi balanced lifting arising from the interaction of the ambient vertical shear with midtropospheric cyclonic vortices mcvs generated by mesoscale convective systems on thermodynamic destabilization over a range of ambient vertical shear strengths and vortex characteristics observed in part i maximum upward displacements occur beneath the midtropospheric potential vorticity anomaly near the radius of maximum tangential vortex winds the location of the region of upward displacements relative to the ambient vertical shear vector depends on the relative strength of the vortex tangential flow and the ambient vertical shear and ranges from downshear for vortices of moderate strength in strong ambient vertical shear to 90 to the left of downshear for strong vortices in weak ambient vertical shear although significant upward displacements occur most rapidly with small vortices in strong ambient vertical shear maximum upward di

climate variability over the last 35 000 years recorded in marine and terrestrial archives in the australian region an oz intimate compilation abstract the australian region spans some 60 of latitude and 50 of longitude and displays considerable regional climate variability both today and during the late quaternary a synthesis of marine and terrestrial climate records combining findings from the southern ocean temperate tropical and arid zones identifies a complex response of climate proxies to a background of changing boundary conditions over the last 35 000 years climate drivers include the seasonal timing of insolation greenhouse gas content of the atmosphere sea level rise and ocean and atmospheric circulation changes our compilation finds few climatic events that could be used to construct a climate event stratigraphy for the entire region limiting the usefulness of this approach instead we have taken a spatial approach looking to discern the patterns of change across the continent the data identify the clearest and most synchronous climatic response at the time of the last glacial maximum lgm 21 3 ka with unambiguous cooling recorded in the ocean and evidence of glaciation in the highlands of tropical new guinea southeast australia and tasmania many terrestrial records suggest drier conditions but with the timing of inferred snowmelt and changes to the rainfall runoff relationships driving higher river discharge at the lgm in contrast the deglaciation is a time of considerable south east to north west variation across the region warming was underway in all regions by 17 ka post glacial sea level rise and its associated regional impacts have played an important role in determining the magnitude and timing of climate response in the north west of the continent in contrast to the southern latitudes no evidence for cooling during the younger dryas chronozone is evident in the region but the antarctic cold reversal clearly occurs south of australia the holocene period is a time of considerable climate variability associated with an intense monsoon in the tropics early in the holocene giving way to a weakened monsoon and an increasingly el nino dominated enso to the present the influence of enso is evident throughout the southeast of australia but not the southwest this climate history provides a template from which to assess the regionality of climate events across australia and make comparisons beyond our region

simulated impacts of a mesoscale convective system on the track of typhoon robyn during tcm 93 abstract the contribution that a mesoscale convective vortex that developed within the circulation of typhoon robyn 1993 may have had to a significant tropical cyclone track change is simulated with a mesoscale model using initial conditions that approximate the circulations measured by aircraft during the tropical cyclone motion tcm 93 field experiment a dry version of the psu ncar mesoscale model is used to first investigate the dynamic aspects of the interaction a deceleration of about 2 m s 1 and then more northward movement similar to that observed for typhoon robyn could have been produced by an interaction with the mesoscale convective vortex of the type modeled in the control run sensitivity of the simulated track change is tested for various aspects of the mesoscale vortex and tropical cyclone it is found that track deflections between 67 and 130 km in 18 24 h could be produced under a variety of realistic scenarios as the mesoscale vortex is advected around the tropical cyclone by the

spatiotemporal characteristics and large scale environments of mesoscale convective systems east of the rocky mountains abstractthe spatiotemporal variability and three dimensional structures of mesoscale convective systems mcss east of the u s rocky mountains and their large scale environments are characterized

surface cyclogenesis from convectively driven amplification of midlevel mesoscale convective vortices mesoscale convective vortices mcvs are midtropospheric warm core cyclonic circulations that often develop in the stratiform region of mesoscale convective systems typically divergent anticyclonically circulating mesoscale cold anomalies appear both above and below the mcv the upper level cold anomaly is usually found near the tropopause while the low level anomaly is surface based and exhibits locally higher pressure one aspect of mcvs that has received much attention recently is the role that they may play in tropical cyclogenesis of special interest is how an mcv amplifies when deep convection redevelops within the borders of its midlevel cyclonic circulation and how the amplified mcv transforms the divergent surface based cold pool with anomalously high surface pressure into a convergent cyclonic circulation with anomalously low pressure the pennsylvania state university national center for atmospheric research fifth generation mesoscale model is used to simulate an mcv that was instrumental in initiating within the borders of the midlevel vortex s circulation several successive cycles of convective development and decay over a 2 day period after each cycle of convection both the horizontal size of the cyclonic circulation and the magnitude of the potential vorticity associated with the vortex were observed to increase the simulation reproduces the development and evolution of the mcv and associated convective cycles mesoscale features responsible for the initiation of convection within the circulation of the vortex and the impact of this convection on the structure and evolution of the vortex are investigated a conceptual model is presented to explain how convective redevelopment within the mcv causes low level heights to fall and cyclonic vorticity to grow downward to the surface applying this conceptual model to a tropical marine environment is also considered

using phytolith assemblages to reconstruct the origin and spread of grass dominated habitats in the great plains of north america during the late eocene to early miocene abstract this paper outlines a general approach for analyzing siliceous microfossils from plants phytoliths in geologic sediments and uses this method to reconstruct the evolution of grasslands in the central great plains during the late tertiary phytolith assemblage analysis is widely employed for reconstructing vegetation types in pleistocene holocene paleoecology and archaeology but no standardized methodology is currently available published phytolith studies are often system specific and tailored after specific modern analogues as a result they vary in extraction technique classification scheme and method of inference for ancient phytolith assemblages whose modern analogues are not well understood a more general analytic approach is necessary this analytic approach includes studying all size fractions 2 250 mm using a classification scheme based on the available literature and a comprehensive modern phytolith reference collection and comparing relative frequencies through time of all diagnostic phytoliths to interpret changes in habitat structure this general method was applied to late eocene to early miocene sediment samples from northwestern nebraska to deduce vegetation history and the results were compared to those obtained using a more specific technique stromberg paleogeogr paleoclimatol paleoecol 177 2002 59 in both studies phytoliths were extracted by means of heavy liquid separation from the following lithostratigraphic units 1 the late eocene chadron formation and the early oligocene brule formation white river group 2 the late oligocene early miocene monroe creek formation the early miocene harrison formation and anderson ranch formation arikaree group and 3 the early miocene runningwater formation and box butte formation ogallala group the two techniques general vs specific produced results that differ markedly data from the general approach indicate the presence of relatively closed habitats in late eocene to early oligocene typified by the presence of phytoliths from bambusoid grasses woody and herbaceous dicotyledons and palms the introduction and spread of modern open habitat grasses such as pooids arundinoids and panicoids occurred between the late oligocene and early miocene this resulted in a savanna or woodland type habitat by the early miocene in contrast analysis using the specific method suggested the presence of open habitats in northwestern nebraska from the late eocene onward the difference in interpretation based on the two approaches is principally due to inclusion of phytoliths 50 mm and the use of an expanded reference collection in the current study general analytic approach these results point to the importance of methodological choices in phytolith analysis and emphasize the usefulness of phytoliths as paleoecological indicators in the fossil record

wood charcoal analysis at riwi cave gooniyandi country western australia abstract wood charcoals excavated from archaeological sites provide a useful tool for palaeoenvironmental reconstruction particularly in arid and semi arid zones where suitable catchments for palynological archives are often limited preservation of organic material in northern australia is characteristically poor and wood charcoal analysis provides a viable alternative to understand shifts in woody vegetation in the past the analysis of charcoal from matrix contexts at riwi cave located in the southern kimberley region of northern western australia has allowed a reconstruction of the local woody vegetation during occupation over the last 45 000 years the wood charcoal assemblage from the holocene stratigraphic units reflects the composition of the modern vegetation and illustrates that people were occupying the site during periods of relative humidity the pleistocene stratigraphic units show a shift in vegetation composition from eucalyptus spp to corymbia sp dominated savanna with an understory of secondary shrub associated with a late mis 3 arid event observed in both terrestrial and marine archives suggesting that activities continued at riwi during this arid event further anthracological analysis of other sites in the kimberley will help to build a regional picture of woody vegetation change and will further disentangle local and regional climatic signals particularly in relation to phases of occupation

stable isotope proxy records in tropical terrestrial environments abstract the tropics refers to an area that is loosely equatorial characterized by relatively high temperatures at low altitude comparatively low seasonal contrast in temperatures and generally high or highly seasonal rainfall the stable isotopes of carbon oxygen and hydrogen are increasingly important tools of relevance to understanding trajectories and mechanisms of past environmental change in the tropics in the case of carbon this is because at the broadest level the carbon isotope composition of organic and carbon containing inorganic proxy materials formed in the tropics can be read as being derived from the balance between c3 tree and c4 grass photosynthesis hence providing a relative measure of vegetation type and indirectly climate likewise changes in the oxygen and hydrogen isotope composition of many proxy materials again at the broadest level can be read as indicative of changes in hydrological conditions and or altitude in the past this review provides an entry point into the literature relating to the use of stable isotopes as terrestrial environmental proxies for past environmental change with a focus on the measurement and interpretation of stable isotope data from the wide range of proxy materials preserved in tropical environments

prediction and diagnosis of tropical cyclone formation in an nwp system part i the critical role of vortex enhancement in deep convection this is the first of a three part investigation into tropical cyclone tc genesis in the australian bureau of meteorology s tropical cyclone limited area prediction system tc laps an operational numerical weather prediction nwp forecast model the primary tc laps vortex enhancement mechanism is presented in part i the entire genesis process is illustrated in part ii using a single tc laps simulation and in part iii a number of simulations are presented exploring the sensitivity and variability of genesis forecasts in tc laps the primary vortex enhancement mechanism in tc laps is found to be convergence stretching and vertical advection of absolute vorticity in deep intense updrafts which result in deep vortex cores of 60 100 km in diameter the minimum resolvable scale is limited by the 0 15 horizontal grid spacing on the basis of the results presented it is hypothesized that updrafts of this scale adequately represent mean vertical motions in real tc genesis convective regions and perhaps that explicitly resolving the individual convective processes may not be necessary for qualitative tc genesis forecasts although observations of sufficient spatial and temporal resolution do not currently exist to support or refute this proposition relatively large scale 30 km and greater lower to midlevel tropospheric convergent regions have been observed in tropical oceanic environments during the global atmospheric research programme garp atlantic tropical experiment gate the equatorial mesoscale experiment emex and the tropical ocean global atmosphere coupled ocean atmosphere response experiment toga coare and regions of extreme convection of the order of 50 km are often remotely observed in tc genesis environments these vortex cores are fundamental for genesis in tc laps they interact to form larger cores and provide net heating that drives the system scale secondary circulation which enhances vorticity on the system scale akin to the classical eliassen problem of a balanced vortex driven by heat sources these secondary vortex enhancement mechanisms are documented in part ii in some recent tc genesis theories featured in the literature vortex enhancement in deep convective regions of mesoscale convective systems mcss has largely been ignored instead they focus on the stratiform regions while it is recognized that vortex enhancement through midlevel convergence into the stratiform precipitation deck can greatly enhance midtropospheric cyclonic vorticity it is suggested here that this mechanism only increases the potential for genesis whereas vortex enhancement through low to midlevel convergence into deep convective regions is necessary for genesis

baroclinic transition of a long lived mesoscale convective vortex abstract the period 5 15 june 2003 during the field phase of the bow echo and mesoscale convective vortex mcv experiment bamex was noteworthy for the wide variety of mesoscale convective systems mcss that occurred of particular interest was a long lived mcv that formed in the trailing stratiform region of an mcs over west texas at 0600 utc 10 june this mcv was noteworthy for its i longevity as it can be tracked from 0600 utc 10 june to 1200 utc 14 june ii development of a surface cyclonic circulation and attendant 2 to 4 hpa sea level pressure perturbation iii ability to retrigger convection and produce widespread rains over several diurnal heating cycles and iv transition into a baroclinic surface cyclone with distinct frontal features baroclinic transition defined here as the acquisition of surface fronts occurred as the mcv interacted with a remnant cold front left behind by a predecessor extratropical cyclone over the great lakes region although the mcv developed well def

balanced and unbalanced circulations in a primitive equation simulation of a midlatitude mcc part i the numerical simulation abstract a midlatitude mesoscale convective complex mcc which occurred over the central united states on 23 24 june 1985 was simulated using the regional atmospheric modeling system rams the multiply nested grid simulation agreed reasonably well with surface upper air and satellite observations and ground based radar plots the simulated mcc had a typical structure consisting of a leading line of vigorous convection and a trailing region of less intense stratiform rainfall several other characteristic mcc circulations were also simulated a divergent cold pool in the lower troposphere midlevel convergence coupled with a relatively cool descending rear inflow jet and relatively warm updraft structure and a cold divergent anticyclone in the tropopause region early in the mcc simulation a mesoscale convectively induced vortex mcv formed on the eastern edge of the convective line while frequently associated with mccs and other mesoscale convective systems mcss mcvs are more typically repo

phytoliths and microcharcoal at jinluojia archeological site in middle reaches of yangtze river indicative of paleoclimate and human activity during the last 3000 years a variety of phytoliths together with prolific microcharcoal particles sponge spicules and diatoms were extracted and identified in four cultural layers from an archeological site at jinluojia macheng hubei province central china the warmth iw and aridity iph indices calculated from grass phytoliths reveal warm and wet periods during the west zhou early east zhou tang and song dynasties whilst cool and dry periods occurred during the late east zhou ming and qing dynasties the paleoclimate conditions reconstructed on the basis of grass phytoliths extracted from archeological sediments are in agreement with those from natural sediments in the middle yangtze region in contrast the woody phytoliths show a positive correlation with microcharcoal particles suggesting an anthropogenic contribution to the woody phytoliths from the use of woody plants for fuel during cooking and heating two episodes of the enhanced abundance of woody phytoliths and microcharcoal particles were found to occur at east zhou dynasty and from ming and qing dynasties to the present proposed to be a consequence of the population expansion and or the frequent wars

mesoscale convective vortex formation in a weakly sheared moist neutral environment abstract idealized simulations of a diabatic rossby vortex drv in an initially moist neutral baroclinic environment are performed using the fifth generation national center for atmospheric research pennsylvania state university ncar psu mesoscale model mm5 the primary objective is to test the hypothesis that the formation and maintenance of midlatitude warm season mesoscale convective vortices mcvs are largely influenced by balanced flow dynamics associated with a vortex that interacts with weak vertical shear as a part of this objective the simulated drv is placed within the context of the bow echo and mesoscale convective vortex experiment bamex field campaign by comparing its tangential velocity radius of maximum winds cape and shear with the mcvs observed in bamex the simulations reveal two distinct scales of development at the larger scale the most rapidly growing moist baroclinic mode is excited and exponential growth of this mode occurs during the simulation embedded within the

the effect of the balcones escarpment on three cases of extreme precipitation in central texas abstractthe proximity to the gulf of mexico and local topography makes central texas particularly prone to heavy precipitation and deadly flood events specifically the balcones escarpment located in central texas creates extremely favorable hydrologic characteristics for damaging floods urban centers such as san antonio and austin texas are located along this terrain feature and have suffered at times even with mitigation strategies catastrophic flood damage while the hydrologic effects of the balcones escarpment are well known the meteorological impacts are uncertain the purpose of this study is to evaluate the effect of the balcones escarpment in three cases of extreme precipitation in which the rainfall was maximized near the escarpment numerical simulations for each event were run at convection allowing grid spacing using the weather research and forecasting wrf model and were used as control runs then the balcones escarpment was removed by moving the associated terrain gradient to th

large scale patterns associated with tropical cyclogenesis in the western pacific abstract five characteristic low level large scale dynamical patterns associated with tropical cyclogenesis in the western north pacific basin are examined along with their capacity to generate the type of mesoscale convective systems that precede genesis an 8 yr analysis set for the region is used to identify and create composites for the five characteristic patterns of monsoon shear line monsoon confluence region monsoon gyre easterly waves and rossby energy dispersion this brings out the common processes that contribute to tropical cyclogenesis within that pattern which are described in detail a 3 yr set of satellite data is then used to analyze the mesoscale convective system activity for all cases of genesis in that period and to stratify based on the above large scale patterns it is found that mesoscale convective systems develop in all cases of genesis except one seventy percent of cases developed mesoscale convective systems at more than one time during the genesis period and 44 of

the multiple vortex nature of tropical cyclogenesis abstract this study explores the extent to which potential vorticity pv generation and superposition were relevant on a variety of scales during the genesis of tropical storm allison allison formed close to shore and the combination of continuous doppler radar satellite aircraft and surface observations allows for the examination of tropical cyclogenesis in great detail preceding allison s genesis pv superposition on the large scale created an environment where decreased vertical shear and increased instability surface fluxes and low level cyclonic vorticity coexisted this presented a favorable environment for meso scale pv production by widespread convection and led to the formation of surface based meso scale vortices termed convective burst vortices cbvs the cbvs seemed to form in association with intense bursts of convection and rotated around each other within the meso circulation field one cbv eventually superposed with a mesoscale convective vortex mcv resulting in a mor

the response of simulated nocturnal convective systems to a developing low level jet some recent numerical experiments have examined the dynamics of initially surface based squall lines that encounter an increasingly stable boundary layer akin to what occurs with the onset of nocturnal cooling the present study builds on that work by investigating the added effect of a developing nocturnal low level jet llj on the convective scale dynamics of a simulated squall line the characteristics of the simulated llj atop a simulated stable boundary layer are based on past climatological studies of the llj in the central united states a variety of jet orientations are tested and sensitivities to jet height and the presence of lowlevel cooling are explored the primary impacts of adding the llj are that it alters the wind shear in the layers just above and below the jet and that it alters the magnitude of the storm relative inflow in the jet layer the changes to wind shear have an attendant impact on low level lifting in keeping with current theories for gust front lifting in squall lines the changes to the system relative inflow in turn impact total upward mass flux and precipitation output both are sensitive to the squall line relative orientation of the llj the variations in updraft intensity and system relative inflow are modulated by the progression of the lowlevel cooling which mimics the development of a nocturnal boundary layer while the system remains surfacebased the below jet shear has the largest impact on lifting whereas the above jet shear begins to play a larger role as the system becomes elevated similarly as the system becomes elevated larger changes to systemrelative inflow are observed because of the layer of potentially buoyant inflowing parcels becoming confined to the layer of the llj

small scale spatial resolution of the soil phytolith record in a rainforest and a dry forest in costa rica applications to the deep time fossil phytolith record abstract phytolith analysis a well established tool in archaeology and quaternary paleoecology has become a source of data for deep time paleoecological studies only in the last 15 years recent years have also witnessed the publication of numerous soil phytolith inventories from extant vegetation types representing modern analogues however this work suffers from several methodological shortcomings limiting inter study comparisons and the development of a single and repeatable protocol for soil sample collection in this paper we focus on two fundamental methodological questions that must be answered before modern analogue studies can be meaningfully applied to deep time paleoecology 1 do phytoliths from the lower portion of the a horizon more commonly preserved in paleosols reflect standing vegetation equally well as the upper a horizon which is more commonly used in modern analogue studies but often truncated by erosion in paleosols 2 does a point soil sample usually collected from paleosols capture standing vegetation as accurately as a composite soil sample commonly used in modern analogue studies which is made from subsamples taken from a small area to address these questions we collected soil from 10 10 m quadrats in a rainforest la selva and a dry forest palo verde in costa rica and compared phytolith assemblages from upper vs lower soil a horizons and composites vs single phytolith assemblages at both sites phytolith assemblages from the lower vs upper a horizon and from single vs composite samples provide similar vegetation structure signal despite some compositional differences these results suggest that the typical approach in deep time paleoecology of taking point samples from the lower a horizon of paleosols is likely justifiable at least for paleosols reflecting rainforest and dry forest soils we discuss possible mechanisms driving differences between sites and future approaches to further expand and test our results

a late quaternary record of monsoon variability in the northwest kimberley australia abstract understanding of the late quaternary environment of australia s vast kimberley region has to date been hindered by the region s lack of classic palaeoenvironmental archives such as deep lake sediments however mound spring peat deposits in the region have been found to be a potentially rich archive of palaeoenvironmental data here we present a high resolution record from black springs mound spring in the kimberley s northwest filling some of the current gaps in knowledge of the region s environmental history this builds on a 6000 year record developed from the same site and indicates that since the last glacial interglacial transition the australian summer monsoon has varied greatly in intensity with an increase in monsoonal precipitation from 14 000 yr bp and pronounced drying in the late holocene despite some chronological uncertainties thought to be due to the inclusion of younger microscopic root fragments changes in the record compare well with other records of climatic change from the kimberley and across tropical northern australia

organizational modes of midlatitude mesoscale convective systems this paper discusses common modes of mesoscale convective organization using 2 km national composite reflectivity data the authors investigated linear mesoscale convective systems mcss that occurred in the central united states during may 1996 and may 1997 based upon the radar observed characteristics of 88 linear mcss the authors propose a new taxonomy comprising convective lines with trailing ts leading ls and parallel ps stratiform precipitation while the ts archetype was found to be the dominant mode of linear mcs organization the ls and ps archetypes composed nearly 40 of the studied population in this paper the authors document the characteristics of each linear mcs class and use operational surface and upper air data to describe their different environments in particular wind profiler data reveal that the stratiform precipitation arrangement associated with each class was roughly consistent with the advection of hydrometeors implied by the mean middle and upper tropospheric storm relative winds which were significantly different among the three mcs modes case study examples are presented for both the ls and ps classes which have received relatively little attention to this point as well the authors give a general overview of the synoptic scale meteorology accompanying linear mcss in this study which was generally similar to that observed by previous investigators

a record of fire vegetation and climate through the last three glacial cycles from lombok ridge core g6 4 eastern indian ocean indonesia abstract charcoal elemental carbon and clastic particle analyses have been undertaken on tropical marine core g6 4 collected from the eastern indian ocean between the lesser sunda islands of indonesia and northwestern australia to help interpret an existing pollen record in addition a new oxygen isotope record has been constructed and several radiocarbon dates produced to allow a refinement of the chronology of the core the record covers the last 300 000 years with three clear glacial interglacial cycles however the new oxygen isotope record and radiocarbon dates suggest a hiatus and it appears that most isotope stage 3 is missing interglacials are characterised by higher values of mangrove fern and rainforest pollen indicating wetter conditions than intervening glacials which have higher cyperaceae and chenopodiaceae values gramineae percentages are also generally higher during glacials but there is a sustained increase in grasses relative to eucalyptus about 185 000 years ago originally interpreted as a change to drier conditions an increase in burning from about 200 000 years ago from charcoal evidence suggests that fire may have been an important contributing factor this and subsequent increases in charcoal may reflect anthropogenic burning and are considered in relation to archaeological evidence for possible times of arrival of people within australia the elemental carbon record shows major differences to that from charcoal and further research is needed to interpret its meaning little consistent evidence for changes in climate or vegetation disturbance is provided by clastic particle influx which may well reveal a record of volcanicity within the region

a satellite based climatology of central and southeastern u s mesoscale convective systems abstracta satellite based climatology is presented of 9607 mesoscale convective systems mcss that occurred over the central and southeastern united states from 1996 2017 this climatology is cons

the distribution and relationship between palynomorphs in aerosols and deep sea sediments off the coast of northwest africa abstract palynomorphs in eolian dust and bottom sediments from the northeastern atlantic off the coast of northwest africa were studied primary examination was for terrestrial plant detritus pollen spores opal phytoliths and freshwater diatoms but observations about marine entities were also made three distinct geographic palynofloras were detected a northern palynoflora consisting of pollen derived primarily from the mediterranean basin a central or saharan palynoflora characterized by pollen derived from desert plants and a southern tropical equatorial palynoflora composed of pollen derived from tropical plants but including up to 50 allochthonous pollen from the drier interior of west africa palynomorph distributions are related closely to both source vegetation and to atmospheric and oceanic transport mechanisms and in many cases distribution patterns in bottom sediments and aerosols are complementary the quantity of pollen and spores per gram of bottom sediment ranges from greater than 2000 off the saharan coast in mauritania to less than 50 in deep ocean basins pollen and spores in mediterranean aerosols may exceed 40 per cubic meter of air during the summer and range between 4 to 6 for tropical aerosols during the winter tropical aerosols and bottom sediments contained the greatest abundance of fungal spores the distribution of opal phytoliths and freshwater diatoms in both aerosols and bottom sediments indicates that dust storms are a major transporting agent for these entities from the interior of west africa to the gulf of guinea these storms are also an important agent for the transport of pollen to the tropical atmosphere distances of transport may exceed 5000 km for mediterranean pollen and even greater distances for palynomorphs in eolian dust from interior west africa the abundance of dinoflagellates and microforaminifera in bottom sediments is directly related to the area of upwelling off the west african coast

convective episodes in the east central united states nine years of composited radar data are investigated to assess the presence of organized convective episodes in the east central united states in the eastern united states the afternoon maximum in thunderstorms is ubiquitous over land however after removing this principal diurnal peak from the radar data the presence and motion of organized convective systems becomes apparent in both temporally averaged fields and in the statistics of convective episodes identified by an objective algorithm convective echoes are diurnally maximized over the appalachian chain and are repeatedly observed to move toward the east partly as a result of this the daily maximum in storms is delayed over the piedmont and coastal plain relative to the appalachian mountains and the atlantic coast during the 9 yr studied the objective algorithm identified 2128 total convective episodes 236 yr 1 with several recurring behaviors many systems developed over the elevated terrain during the afternoon and moved eastward often to the coastline and even offshore in addition numerous systems formed to the west of the appalachian mountains and moved into and across the eastern u s study domain in particular many nocturnal convective systems from the central united states entered the western side of the study domain frequently arriving at the eastern mountains around the next day s afternoon maximum in storm frequency a fraction of such well timed systems succeeded in crossing the appalachians and continuing across the piedmont and coastal plain convective episodes were most frequent during the high instability low shear months of summer which dominate the year round statistics even so an important result is that the episodes still occurred almost exclusively in above average vertical wind shear despite the overall dominance of the diurnal cycle the data show that adequate shear in the region frequently leads to long lived convective episodes with mesoscale organization

subkilometer simulation of a torrential rain producing mesoscale convective system in east china part i model verification and convective organization abstracta nocturnal torrential rain producing mesoscale convective system mcs occurring during the mei yu season of july 2003 in east china is studied using conventional observations surface mesoanalysis satellite and radar data and a 24 h multinested model simulation with the finest grid spacing of 444 m observational analyses reveal the presence of several larger scale conditions that were favorable for the development of the mcs including mei yu frontal lifting moderate cold advection aloft and a moist monsoonal flow below and an elongated old cold dome left behind by a previously dissipated mcs results show that the model could reproduce the evolution of the dissipating mcs and its associated cold outflows the triggering of three separate convective storms over the remnant cold dome and the subsequent organization into a large mcs and the convective generation of an intense surface meso high and meso scale radar reflectivity morphologies in particular the model reproduces the passage of

late quaternary palaeoenvironmental change in the australian drylands in this paper we synthesise existing palaeoenvironmental data from the arid and semi arid interior of the australian continent for the period 40 0 ka moisture is the predominant variable controlli

the global population of mesoscale convective complexes a global set of 714 mesoscale convective complexes is compiled and some of the common properties of the convective systems are identified and examined from a global perspective the data set includes date of occurrence time of first storms initiation maximum extent termination duration cold cloud shield areas and tracks from initiation to termination it is found that the typical convective complex is nocturnal generates a cold cloud shield area of approximately 350 000 km2 and persists for about 10 h the largest systems and most persistent systems tend to occur near the summer solstices for the globe about 400 systems occur each year primarily over land areas most systems develop in favoured zones although some activity occurs over every continent except antarctica and all major oceans the concentration of activity into favoured zones indicates that there must be special dynamic and or thermodynamic conditions necessary for convection to organize into convective complexes activity is strongly tied to the solar day and shifts from 35 s in early january to about 50 n during the boreal summer and back to 35 s by december within the northern hemisphere there is a pronounced poleward migration as the jet stream shifts northward relatively little migration occurs in the ocean dominated southern hemisphere where the subtropical jet remains quasi stationary over the convective complex regions the nocturnal life cycles copious rainfall large cloud shields and great frequency of mesoscale convective complexes suggest that they may be significant contributors to the global hydrologic cycle and earth system energy budget

mesoscale convective systems 1 mesoscale convective systems mcss have regions of both convective and stratiform precipitation and they develop mesoscale circulations as they mature the upward motion takes the form of a deep layer ascent drawn into the mcs in response to the latent heating and cooling in the convective region the ascending layer overturns as it rises but overall retains a coherent layer structure a middle level layer of inflow enters the stratiform region of the mcs from a direction determined by the large scale flow and descends in response to diabatic cooling at middle to low levels a middle level mesoscale convective vortex mcv develops in the stratiform region prolongs the mcs and may contribute to tropical cyclone development the propagation of an mcs may have a discrete component but may further be influenced by waves and disturbances generated both in response to the mcs and external to the mcs waves of a larger scale may affect the propagation velocity by phase locking with the mcs in a cooperative mode the horizontal scale of an mcs may be limited either by a balance between the formation rate of convective precipitation and dissipation of stratiform precipitation or by the rossby radius of the mcv the vertical redistribution of momentum by an mcs depends on the size of the stratiform region while the net vertical profile of heating of the large scale environment depends on the amount of stratiform rain regional variability of the stratiform rain from mcss affects the large scale circulation s response to mcs heating

evaluating human responses to enso driven climate change during the holocene in northwest australia through macrobotanical analyses the holocene is recognised as a period through which a number of climatic fluctuations and environmental stresses occur associated with intensifying el nino southern oscillation enso climatic con

the genesis of hurricane guillermo texmex analyses and a modeling study abstract the transformation of a mesoscale convective system into hurricane guillermo was captured by aircraft and doppler wind data during the tropical experiment in mexico the early phase of the system evolves in a way very similar to previously documented mesoscale convective systems with a midlevel mesocyclone developing in the stratiform precipitation region more unusually the cyclone extends to low altitudes a weak cyclone is discernable even in the 300 m altitude wind field after another day of evolution a small surface based warm core cyclone is observed to develop within the relatively cold air associated with the mesocyclone aloft this mesocyclone develops into a hurricane over the subsequent day a nonhydrostatic axisymmetric numerical model is used to explore the evolution of the initially cold core midlevel vortex into a tropical cyclone a mesoscale midlevel showerhead is switched on in an initially quiescent tropical atmosphere overlying a warm ocean surface evaporation of t

coherent regeneration and the role of water vapor and shear in a long lived convective episode abstract in a recent radar based climatological study of warm season precipitation over the continental united states carbone et al found a high frequency of long lived coherent rainfall episodes many of the events were of longer duration than normally associated with mesoscale convective complexes and exhibited phase speeds 10 m s 1 in excess of the phase speed associated with synoptic systems the observations led to the speculation that cold pool dynamics and wavelike propagation mechanisms were responsible for the longevity of the systems one of the long lived episodes included in the statistics of the carbone et al study is described here occurring on 14 15 july 1998 the system lasted 50 h and traveled over 2800 km at its peak intensity the system was a bow echo producing damaging wind large hail and local flash flooding an interesting aspect of the event was an abrupt 90 turn in the storm s orientation and propagation vector midway through its life the environmental factors that led t

long term erosion of the tidal flats king sound north western australia abstract king sound in northwestern australia with a tropical semi arid climate is situated in a macrotidal tide dominated regime the shores of king sound are bordered by tidal flats that exhibit a considerable variation in geomorphology and stratigraphy erosion is the dominant geomorphic process forming the tidal flats today three types of erosion are important these are sheet cliff and tidal creek erosion tidal flat geomorphology at the local scale is an expression of which erosion type is dominant the geomorphology at regional scale is largely an expression of the extent that erosion has gone to completion in removing holocene pleistocene and bedrock stratigraphic units determination of erosion rates over the past few decades extrapolation of these rates into the past together with stratigraphic and diagenetic data point to a long term erosional history for king sound king sound itself appears to be formed largely as a result of long term lateral erosion

the oceanic mesoscale convective system and associated mesovortex observed 12 december 1992 during toga coare this study documents the precipitation and kinematic structure of a mature mature to decaying westward propagating near equatorial oceanic mesoscale convective system mcs observed by airborne doppler radars during toga coare the tropical ocean global atmosphere coupled ocean atmosphere response experiment this system occurred on 12 december 1992 during the convectively active phase of an intraseasonal oscillation and was followed at its dissipating stage by a redevelopment of convection that led to the mcs observed on 13 december 1992 these two successive mcss were associated with a two day atmospheric disturbance radar deduced airflows at two time periods reveal many similarities with other tropical oceanic cloud clusters in particular a marked rear inflow jet associated with a midlevel cyclonic mesovortex was observed within the rear of the stratiform region the mesovortex was better defined both in size and depth during the mature to decaying stage and was located more inside the system within a region of convergence due to the westward propagation of the rear inflow countergradient transports of momentum normal to the mean orientation of the system at midlevels and downgradient transports at lower and higher levels helped to intensify this rear inflow these transports were mostly accomplished by eddy structures cyclonic vorticity was concentrated at the rear of the mcs and peaked at the centre of the observed closed wind circulation as previously observed stretching of the pre existing vertical vorticity was the dominant dynamical mechanism which helped to amplify the mesovortex at mid to upper levels while tilting of the horizontal vorticity into the vertical was a lesser mechanism and had an opposite effect in most respects advective processes were negatively correlated with the stretching and tilting mechanisms but not sufficiently to be balanced the resulting tendency was an increase of cyclonic vorticity at low to mid levels and a net decrease above

radioactive disequilibria in mineralised fracture samples from two uranium occurrences in northern sweden abstract mineralised fractures from two uranium occurrences in northern sweden were examined mineralogically and isotopically to establish the presence or absence of radioactive equilibrium that may indicate recent rock water interaction processes based on the natural mobility of uranium i e during the last 0 5 ma the results show evidence of radioactive disequilibrium in six of the nine samples investigated disequilibria are attributable to solution to solid 234 u recoil gain weakly mineralised zones adjacent to the main mineralisation and solid to solution 234 u recoil loss moderate to highly mineralised zones the absence of significant 238 u loss in the samples emphasises the reducing conditions at the sampled depths

the evolution of the 10 11 june 1985 pre storm squall line initiation development of rear inflow and dissipation abstract mesoscale analysis of surface observations and mesoscale modeling results show that the 10 11 june squall line contrary to prior studies did not form entirely ahead of a cold front the primary environmental features leading to the initiation and organization of the squall line were a low level trough in the lee of the rocky mountains and a midlevel short wave trough three additional mechanisms were active a southeastward moving cold front formed the northern part of the line convection along the edge of cold air from prior convection over oklahoma and kansas formed the central part of the line and convection forced by convective outflow near the lee trough axis formed the southern portion of the line mesoscale model results show that the large scale environment significantly influenced the mesoscale circulations associated with the squall line the qualitative distribution of along line velocities within the squall line is attributed to the larger scale circulations associated with the le

palynology of eastern indonesian marine piston cores a late quaternary vegetational and climatic record for australasia abstract pollen analyses of late quaternary sediments from nine marine piston cores reveal a continuous vegetation and environmental record for eastern indonesia and northern australia on the island of halmahera a montane oak forest largely replaced the tropical lowland vegetation during the last glacial period while fern cover was strongly reduced during its maximum 18 000 yr b p climate was cooler and slightly drier than today around 10 000 yr b p mangrove vegetation expanded following the rising sea level in our western new guinea record at 14 000 yr b p climate grew warmer and slightly wetter until it stabilised around 10 000 yr b p at that time the mid to upper montane forests expanded to their full altitudinal range and fern cover increased while montane oak forest grassland and woodland areas had contracted in our marine pollen records during the last glacial the climate of northern australia was distinctly drier than today grassland vegetation with sedges increased considerably at 38 000 and 24 000 yr b p replacing eucalypt forest and culminating in a maximum grassland cover at the height of the last glaciation 18 000 yr b p the rapid sea level rise allowed the expansion of mangrove forests and salt bush marshes which had become established on the large tidal flats of the drowning sahul shelf around 12 000 yr b p one piston core g6 4 extends to 300 000 yr b p and shows that glacial periods are characterized by high pollen concentrations in marine sediments recording expanding grassland vegetation during interglacial woodland and fern cover increased while pollen concentrations in the sediments were low after 190 000 yr b p a more open vegetation suggests that conditions were in general much more arid than before repeated mangrove vegetation expansions suggest major rises in sea level at around 244 000 220 000 and 130 000 yr b p

genesis of typhoon chanchu 2006 from a westerly wind burst associated with the mjo part ii roles of deep convection in tropical transition abstractin this study the life cycles of a series of four major mesoscale convective systems mcss during genesis and their roles in transforming a vertically tilted vortex associated with a westerly wind burst hereafter the wwb vortex into typhoon chanchu 2006 are examined using 11 day cloud resolving simulations presented in part i it is found that the tilted wwb vortex at early stages is characterized by an elevated cold core layer about 200 hpa thick below and a weak warm column above with large vertical wind shear across the layer which extends over a horizontal distance of about 450 km between the vortex s 400 and 900 hpa centers during the final two days of the genesis process the upper level warm column increases in depth and intensity as a result of the absorption of convectively generated vortices cgvs including a mesoscale convective vortex mcv causing more rapid amplification of cyclonic vorticity in the middle than the lower troposphere the commencement of sustained intens

comparison between two case studies of developing and nondeveloping african easterly waves during namma and amma sop 3 absolute vertical vorticity budget abstract two west african disturbances observed in august and september 2006 during the national aeronautics and space administration african monsoon multidisciplinary analysis namma and the special observing period 3 amma sop 3 have been simulated using the meso nh numerical model with explicit convection the first disturbance spawned hurricane helene 2006 off the west african coast and the second one referred to as perturbation d though relatively intense failed to develop over the continent each case was associated with a well defined african easterly wave aew trough with embedded growing and decaying convective activity of various size duration and intensity the aim of this work is to investigate the contribution of these convective systems in the generation and maintenance of cyclonic vorticity associated with the aew trough with respect to the synoptic scale processes the absolute vorticity budgets are analyzed during the continental and oceanic transition stages of these aew

initiation of a mesoscale convective complex over the ethiopian highlands preceding the genesis of hurricane alberto 2000 1 a tropical disturbance which would later become hurricane alberto 2000 was traced back in time as a mesoscale convective complex mcc to the ethiopian highlands eh where the mcc first developed meteosat 7 imagery indicates that the mcc develops during the late afternoon and evening of 28 july 2000 and that a mesovortex mv was evident on the morning of 29 july 2000 a preliminary mesoscale model simulation features the development of two areas of maximum relative vorticity in the middle troposphere with the maturation of one of the vorticity maxima into a significant mv the higher level vorticity center of the simulated mv tracks westward and is nearly collocated with the vortex signature in satellite imagery while the lower level center remains near the lee side of the eh the vortex signature in satellite imagery was traceable to the cyclogenesis stage over the eastern atlantic ocean

the kinematics of a midlatitude continental mesoscale convective system and its mesoscale vortex the authors present a unique scale discriminating study of the environment relative circulations within a mesoscale convective system mcs and mesoscale convective vortex mcv the mcs a leading convective line and trailing stratiform region that became asymmetric passed through the national oceanic and atmospheric administration noaa profiler network npn in kansas and oklahoma on 1 august 1996 the mcv appeared in the mcs s stratiform region just prior to the system s mature stage and grew to a depth of over 12 km as the mcs dissipated the mcv did not apparently survive to the next day a spatial bandpass filter was used to divide observed wind into a component that was predominantly synoptic background wind and a component that was predominantly a mesoscale perturbation on that background wind a mesoscale updraft mesoscale downdraft and divergent outflows in the lower and upper troposphere were evident after the synoptic background wind was removed so these four circulations were internal and fundamental to the mcs the mesoscale perturbation in wind in the middle troposphere extended farther behind the mcs than ahead of it consistent with analytic studies and numerical simulations of gravity waves generated by heat sources characteristic of mcss with leading convective lines and trailing stratiform regions deepening of the mcv appeared to be reflected in the vertical wind shear at the vortex s center as the mcv strengthened the mesoscale shear through its lower part decreased perhaps as wind became more vortical at increasing altitudes mesoscale and synoptic vertical shears were of similar magnitude so an average of environmental soundings outside an mcs probably does not accurately represent the shear that affects an mcv this suggests the need to reevaluate how the kinematical settings of mcvs are diagnosed

alpine grassland palaeoecology of the virunga volcanoes east africa a new phytolith record from mt muhavura abstract this study presents a first attempt at using phytoliths from a high altitude crater lake as a palaeoecological tool at a tropical montane site mt muhavura 4127 m asl at the border of uganda and rwanda is part of the virunga volcanoes located in the albertine rift one of the most biodiverse areas in africa to investigate the potential of phytoliths to record grassland history in an afroalpine environment a unique and little studied ecosystem we analysed the phytolith content of 37 sediment samples from a 159 cm sediment core from the crater lake at the summit of mt muhavura representing the last ca 2400 years bp ten plant species from the alpine belt were also analysed for their main phytolith morphotypes phytoliths from the sediments were grouped into 12 main categories and the most frequently occurring individual morphotypes were bilobate 33 oblong 16 elongate 17 and globular psilate 13 the phytolith assemblage consists predominantly of phytoliths characteristic of grasses 70 a literal interpretation of the results would be that panicoideae grasses mainly c 4 that are characteristic of warm and wet climate and c 3 pooideae subfamily grasses characteristic of cold climate high altitude have co existed throughout the late holocene in this belt as only c 3 cold climate grass subfamilies are known to occur at this altitude today the abundance of short cell phytoliths bilobates typical of panicoideae grasses in the lake sediments at this altitude presents a new perspective to the phytolith discussion the c 3 pooideae grasses analysed did not produce bilobates in this study the phytolith index ic that is used as a proxy of past grass subfamily dominance is not representative of the taxonomic significance for which it is known this study suggests that caution needs to be taken when using bilobate morphotypes and the ic as indicators of grass subfamily dominance at high altitude on east african mountains as the bilobates may not be taxonomically representative of the grasses for which they are typically known this highlights the inherent problem of phytolith redundancy even at an altitude where c 3 c 4 grass distribution is better delineated

reconstructing late holocene palaeoenvironments in bangladesh phytolith analysis of archaeological soils from somapura mahavihara site in the paharpur area badalgacchi upazila naogaon district bangladesh palaeoenvironmental reconstruction based on phytolith analysis of late holocene aged soils in and around the somapura mahavihara archaeological monastery site in the paharpur area badalgacchi upazila of naogaon district in northwestern bangladesh was undertaken results indicate five climate zones marked by alternatively cool and temperate events the phytolith assemblages of zones 1 3 and 5 are clearly characterized by a higher proportion of pooideae phytoliths the climate indices for these zones are all greater than 50 indicating cooler climatic conditions in contrast the phytolith assemblages of zones 2 and 4 are typified by a higher proportion of panicoideae phytoliths their climate indices are 42 and 44 respectively indicating the presence of a warmer more temperate climate in general the dominance of grasses over broad leaved trees throughout the sequences suggests that generally cool to temperate and dry conditions with some cyclical variability persisted around paharpur and the surrounding region throughout the pala dynasty from ad 730 to 1080 the question of whether these shifts in vegetation might be linked with el nino southern oscillation events and whether these might in turn have cultural responses is raised

late quaternary environmental changes in eastern and central australia and their climatic interpretation abstract the march of environmental changes in eastern australia from the last interglacial to the holocene is reviewed palynologic evidence suggests that forest composition fluctuated substantially during oxygen isotope oi substages 5a to 5e but physical evidence for this period is as yet poorly defined during oi stage 3 and possibly part of 4 inland lakes were larger and the hydrologic balance was wetter than at any time since conditions were coldest and dune activity was maximal throughout the continent during oi stage 2 but driest conditions as judged from lake levels occurred at the termination of the pleistocene when temperatures were rising rapidly lags between changes of boundary conditions and responses of natural systems are clearly seen in holocene behaviour of coasts and reefs and the effects of extreme events rather than climatic changes are seen in some sedimentary sequences establishment of the chronology of deposits older than about 35 ka and forging links between the terrestrial and deep sea records are major challenges for future research

structures and dynamics of quasi 2d mesoscale convective systems abstract recently three distinct archetypes for midlatitude linear mesoscale convective systems mcss have been identified this article focuses on the fundamentals of two of these archetypes convective lines with trailing stratiform ts precipitation and convective lines with leading stratiform ls precipitation both the ts and ls modes typically exhibit quasi 2d reflectivity patterns and quasi 2d environmental storm relative wind fields ongoing work has revealed that there are three common flow structures for these quasi 2d mcss front fed ts systems which are sustained by front to rear storm relative inflow as well as front fed ls and rear fed ls systems which are sustained by rear to front storm relative inflow this paper summarizes the observed structures of the front fed ts front fed ls and rear fed ls modes and then outlines an idealized numerical experiment in which these modes were simulated the authors analyze the basic simulated kinematic and microphysical structures and provid

the early occupation of the eastern pilbara revisited new radiometric chronologies and archaeological results from newman rockshelter and newman orebody xxix abstract for over 30 years the radiometric chronologies of newman rockshelter and newman orebody xxix have been central to archaeological discussions on the pleistocene aboriginal occupation of the hamersley plateau and greater pilbara region until 2009 these two sites were heralded as having the oldest evidence of human occupation on the plateau dating to the last glacial maximum lgm 26 20 ka more recently however the excavations at several other rockshelters have shown that ancient aboriginal peoples occupied the hamersley plateau many thousands of years before the onset of the last glacial cycle when regional climatic conditions were wetter and more amenable this paper presents the results of our re excavation of both newman rockshelter and newman orebody xxix our research has resulted in the compilation and analysis of large lithic datasets for each of these sites and the construction of geo chronologies using modern radiometric techniques including ams radiocarbon dating and optically stimulated luminescence dating these new radiometric chronologies and artefact data indicate that both sites were occupied between 45 and 40 ka despite having significant early occupational evidence neither of the rockshelters present strong evidence for sustained or persistent site use during the lgm proper ca 23 19 ka however there is substantial evidence for more routine occupation of these localities during the terminal pleistocene and holocene

settling in sahul investigating environmental and human history interactions through micromorphological analyses in tropical semi arid north west australia the pleistocene continent of sahul was first settled by people who arrived by watercraft from island south east asia about 50 000 years ago some of the oldest archaeological sites in sahul are located in the southern kimberley in northwest australia this area lies within the southern zone of influence of the tropical monsoon and thus has always been highly sensitive to changes in monsoon dynamics over time how these climatic changes have affected the colonisation and occupation of australia is an important research theme in australian archaeology this paper illustrates the contribution and challenges of micromorphology in deciphering palaeoenvironmental and anthropogenic markers in a still largely unexplored australian context micromorphological analysis of two archaeological sequences in the napier range carpenters gap 1 and 3 provides a complementary and comprehensive reconstruction of the human climate history in this area spanning nearly 50 000 years of australian human presence the results demonstrate an opportunistic use of sites by people through time surprisingly independent of local climatic variation suggesting highly flexible subsistence strategies

cloud resolving simulations of mesoscale vortex intensification and its effect on a serial mesoscale convective system abstract the authors performed numerical simulations of the 27 28 may 1998 mesoscale convective vortex mcv and mesoscale convective system mcs to understand how the mcv modulated the convection and how the convection intensified the vortex the fifth generation pennsylvania state university national center for atmospheric research psu ncar mesoscale model mm5 was used initialized with the analysis from the rapid update cycle version 2 ruc 2 and nested to achieve 1 5 km grid spacing covering the mcs the model successfully simulated a north south convective band that formed near the center of the mcv in the early evening the simulation then correctly reoriented the convection along a roughly east west line in response to northward transport of warm conditionally unstable air within the nocturnal low level jet balanced vertical motion was found to contribute substantially to mesoscale lifting and thermodynamic destabilization which localized the convection horizontal transport of moist uns

the large scale environments of the global populations of mesoscale convective complexes abstract the mean genesis environment was constructed for each of five mesoscale convective complex mcc population centers around the world africa australia china south america and the united states it is found that the environments are very similar and exhibit many of the same dynamic and thermodynamic structures that are present with systems in the united states in particular mccs initiate within prominent baroclinic zones characterized by locally large values of lower tropospheric vertical wind shear and convective available potential energy cape typically a low level jet of air with low static stability high equivalent potential temperature oriented nearly perpendicular to the baroclinic zone intrudes into the genesis region and is forced to ascend over a relatively shallow surface based layer of relatively cool air pronounced warm advection accompanied by strong lower tropospheric veering overlays the surface based cool layer a local maximum in absolute humidity and a local minimu

microarchaeology of a collective burial cova des pas minorca ftir and phytolith analyses have been used to understand the exceptional preservation of the organic remains at the burial cave of cova des pas minorca and to obtain high resolution data of the plant remains present in the sediments the presence of sodium nitrate and gypsum suggests a relatively dry environment that has enabled the preservation of the organic material and contributed to the natural mummification the dry conditions also favored phytolith preservation grass inflorescence phytoliths are abundant all over the site suggesting that phytolith accumulations might have an anthropogenic origin and are related to the burial ritual