sea land breeze development during a summer bora event along the north eastern adriatic coast the interaction of a summer frontal bora and the sea land breeze along the north eastern adriatic coast was investigated by means of numerical simulations and available observations available measurements in situ radiosonde satellite images provided model validation the modelled wind field revealed several regions where the summer bora weaker than 6 m s 1 allowed sea breeze development in the western parts of the istrian peninsula and rijeka bay and along the north western coast of the island of rab along the western istrian coast the position of the narrow convergence zone that formed depended greatly on the balance between the bora jets northward and southward of istria in the case of a strong northern trieste bora jet the westerly istrian onshore flow presented the superposition of the dominant swirled bora flow and local weak thermal flow it collided then with the easterly bora flow within the zone with weakening of the trieste bora jet the convergence zone was a result of the pure westerly sea breeze and the easterly bora wind in general during a bora event sea breezes were somewhat later and shorter with limited horizontal extent the spatial position of the convergence zone caused by the bora and sea breeze collision was strongly curved the orientation of the head of the thermally induced flow was more in the vertical causing larger horizontal pressure gradients and stronger daytime maximum wind speed than in undisturbed conditions except for the island of rab other lee side islands in the area investigated did not provide favourable conditions for the sea breeze formation within a bora wake near the island of krk onshore flow occurred as well although not as a sea breeze flow but as the bottom branch of the lee rotor that was associated with the hydraulic jump like feature in the lee of the velika kapela mountain copyright 2010 royal meteorological society

the mesoscale and microscale structure and organization of clouds and precipitation in midlatitude cyclones viii a model for the seeder feeder process in warm frontal rainbands abstract previous field studies have indicated that warm frontal rainbands form when ice particles from a seeder cloud grow as they fall through a lower level feeder cloud in this paper we present results from a parameterized numerical model of the growth processes that can lead to the enhancement of precipitation in a seeder feeder type situation the model is applied to two types of warm frontal rainbands in the first type 1 situation the vertical air motions are typical of those associated with slow widespread lifting in the vicinity of warm fronts in the second type 2 situation the vertical air motions are stronger and more characteristic of the mesoscale the model simulations show that in the type 1 situations the growth of the seed ice crystals within the feeder zone is due to vapor deposition the feeder zone in this case is slightly sub saturated with respect to water due to the presence of the seed crystals in regions where the feeder zone is not seeded from aloft snow cryst

the effect of bottom friction on shallow water flow past an isolated obstacle abstract the effect of bottom friction on fluid flow past an isolated obstacle is investigated in the shallow water framework the controlling parameter for this effect is the nondimensional bottom friction number defined as a ratio of friction to inertia with the bottom stress related to the horizontal wind via standard bulk aerodynamic formula the friction number is proportional to the surface roughness the horizontal scale of the obstacle and the inverse of the upstream fluid depth thus under otherwise identical conditions the flow past larger obstacles will be more viscous bottom friction modifies the vorticity generation in several ways but under normal conditions the wake formation remains dominated by a pseudoinviscid process related to the presence of hydraulic jumps however friction strongly controls the velocity deficit region of the wake and thus influences the stability of the steady state wakes predictions of the linear stability analysis are compared with numerical simulation

the wake of st vincent abstract the island of st vincent and the other windward islands in the southeastern caribbean were chosen as a field site for the study of weak mountain wakes by the authors definition a weak wake forms when the potential vorticity generated by a mountain is not strong enough to advect itself into eddies rather it is simply advected downstream by the ambient flow goes 8 and landsat sunglint images unambiguously revealed that the mountainous windward islands have remarkably long straight wakes the length of st vincent s wake exceeds 300 km although its width is only 20 km near the islands the wake structures reflect the details of the island topography these wakes do not exhibit any obvious diurnal effect boat surveys in the lee of st vincent confirmed the existence of features seen in the images the sharp wake boundary the small valley induced jet embedded in the near wake and the absence of any reverse flow aircraft surveys gave evidence of descent over the island and showed that the

pleistocene glacial relief of the central part of mt prokletije albanian alps abstract the central and highest area of mt prokletije albanian alps is situated in northern albania and eastern montenegro at 42 30 n the highest peak is maja e jezerces 2694 m detailed geomorphological mapping was used to reconstruct the positions of former glaciers the longest ropojana glacier had a length of 12 5 km and surface of 20 km 2 others include valbona glacier 9 5 km 10 5 km 2 grbaja glacier 5 km 6 7 km 2 and bogicevica glacier 6 km 6 9 km 2 three series of moraines can be distinguished the lowest at an average altitude of 990 m average ela 1750 m the middle series at 1350 m ela 1942 m and the highest at 1900 m ela 2123 m as no advanced dating methods have yet been used to provide a numerical chronological framework for these features hypotheses are made based on the comparison with the advanced studies of other similar mountains in the mediterranean region the moraines of the first stage lowest series correspond to one of pre lgm glaciations middle or even early wurmian the second stage moraines probably correspond to lgm and the third stage could be attributed to younger dryas the mapping included a number of inactive and active rock glaciers as well as three small active glaciers surface 5 ha and less at 1980 2100 m altitude in the area close to maja e jezerces

discovery of early holocene wood and peat on the forefield of the pasterze glacier eastern alps austria during recent years a number of fragments of pinus cembra and larix decidua as well as peat were found in front of the tongue of the pasterze glacier in the eastern alps these were washed out by the stream from under the present ice the wood originates from trees which reached ages of upto 400 years or more radiocarbon dating shows them to come from the early holocene they indicate that between cal bc 8100 and cal bc 6900 the pasterze glacier was smaller than at present the pasterze glacier advanced around cal bc 6900 a lump of peat shows that around cal bc 6300 at the latest the pasterze glacier was again smaller than today the radiocarbon age of the fulvic acid fraction of thepeat suggests that growth could have continued until cal bc 5430 5080 further wood samples dated to around cal bc 4800 and cal bc 3800 show that at these times the pasterze glacier was smaller than at present the pasterze glacier had a relatively limited extent over long periods inthe early holocene thus mostly favou

modeling the trajectories of satellite tracked drifters in the adriatic sea during a summertime bora event 1 during the summertime bora episode of 22 25 june 1995 characterized by hazardous weather conditions with strong winds of over 20 m s 1 two satellite tracked drifters were present in the adriatic shelf area one was on the open sea south of the istrian peninsula while the other which measured the surface current of 70 cm s 1 was tracked along the western coastal strip an oceanographic model forced by the outputs of mesoscale meteorological models and by river discharges was applied to simulate drifter trajectories during the event process oriented studies performed to determine governing forcings for the drifter movements in different areas of the adriatic revealed that strong current along the western adriatic coast resulted from a combined influence of the wind stress and the river discharges the wind was responsible for the strong drifter movements while the baroclinic current due to the coastal buoyancy fluxes prevented the drifter from moving close to the shore and from colliding with the coast at the same time drifter movements in the open sea resulted from the wind action solely differences in the alongshore and offshore vertical density profiles primarily due to the river inflows caused 3 times stronger currents in the coastal area as compared to the currents in the open sea the proper formulation of the drag coefficient was crucial for the successful simulations of the drifter trajectories as simulations with increased values of the drag coefficient reproduced well the effects of the sea surface roughness and atmospheric instability above the sea

sar derived gap jet characteristics in the lee of the philippine archipelago abstract gap jet characteristics were analyzed in the lee of the philippine archipelago during the 2004 2009 winter monsoon seasons november march using wind fields derived from envisat synthetic aperture radar sar images jet characteristics were derived for the philippine island gap jets and compared to those from theoretical literature and experimental studies it was found that 18 of 31 jets characterized from 13 sar images followed the defined power laws or classic case and were similar to the defined scale equations the remaining 13 jets did not follow the classic case and resulted from jet interaction with islands adjacent jets and variable atmospheric conditions these non classic jets were grouped based upon similarities and referred to as decreasing increasing and reverse classic cases distinct deviations from the classic case included downstream increases in velocity and decreases in jet width it was found that the orientation of the wind field relative to topography significantly impacted jet classification and thereby made it difficult to characterize jets by region for all 31 jets the initial jet width dictated the distance at which a jet became self similar wherein a larger initial jet width required a greater distance for self similarity

numerical and observational case study of a deep adriatic bora a detailed analysis of bora winds is presented that were observed on 28 march 2002 in the north eastern part of the adriatic sea very high resolution numerical simulations are compared with airborne surface and balloon observations the key instrument for the verification of the numerical results is an aerosol backscatter lidar on board the dlr falcon research aircraft the high spatial resolution of the model and of the observational dataset allows several small scale aspects of the bora winds to be explored the study emphasises the great impact of boundary layer effects including convective mixing and surface friction on the structure of the bora flow the numerical model reveals that the diurnal cycle of the planetary boundary layer causes a diurnal variation of the gravity wave amplitude and consequently a variation in the bora strength the downslope flow is strongest during the night time when the impinging air mass is stably stratified and exhibits a low level jet the bora strength weakens during the daytime due to the evolution of a neutrally stratified convective boundary layer lidar observations and simulations both suggest that the observed bora winds are driven by the dynamics of orographic gravity waves in the deep north easterly cross mountain flow steeply amplified but non breaking gravity waves as well as trapped lee waves are found throughout the troposphere vertical separation of the boundary layer over the steep leeward terrain slope prevents the bora flow from reaching the coast as a result the flow is kept aloft in a series of at least three unsteady trapped lee waves before it reattaches to the surface over the sea downstream of the mountains no clear evidence is found for the existence of low level rotors underneath these lee waves the ability of the model to capture the trapped waves is found to depend on the horizontal model resolution bora winds are identified as jets emanating from several mountain gaps the physical mechanism for the gap flow formation is boundary layer separation controlled by surface friction flow separation is more effective over the highest terrain where a broad wake forms downstream with weak winds compared to the mountain gaps where the strong bora flow eventually reattaches to the surface the strongest gap jet belongs to the vratnik pass upstream of the town senj and forms the primary shear line in the northern adriatic with a corresponding potential vorticity pv banner the numerical model reveals several secondary orographic pv banners and embedded pv filaments the vertical pv distribution exhibits a two layer structure with pv anomalies at lower higher elevations originating from mountain gaps isolated mountain peaks surface friction has a minor direct effect on pv generation but has a major indirect effect in controlling the mechanism for the generation of pv in a simulation without surface friction the primary pv banner forms as a result of gravity wave breaking in the more realistic simulation however the primary mechanism for pv generation is flow separation controlled by surface friction copyright 2005 royal meteorological society

subglacial carbonates constrain basal conditions and oxygen isotopic composition of the laurentide ice sheet over arctic canada subglacially precipitated carbonate crusts spccs formed on bedrock and till boulder surfaces adjacent to the barnes ice cap bic central baffin island arctic canada act as unique archives of laurentide ice sheet basal conditions uranium series dating of these features reveals that carbonate precipitation from subglacial meltwater occurred during the last glacial maximum lgm requiring warm based ice in the region at that time however the preservation of fragile spccs is unlikely beneath erosive warm based ice suggesting that the transition to subsequent cold based conditions took place shortly after the lgm and glacial erosion in the region occurred dominantly prior to the lgm the oxygen isotopic composition of the meltwater from which the spccs precipitated is indistinguishable from that of the debris rich bic basal ice 18 o 24 referenced to vienna standard mean ocean water but distinct from that of the overlying white pleistocene ice 18 o 35 demonstrating that spccs are reliable archives of the isotopic composition of only the basal ice of past ice sheets

enhancing rescue archaeology using geomorphological approaches archaeological sites in paredes asturias nw spain abstract palaeolithic remnants a necropolis roman villa and another minor archaeological site were discovered in paredes spain these sites were the focus of multidisciplinary research during the construction of a large shopping centre in asturias nw spain the aims of this study are 1 to contribute to archaeological prospection in the sites and 2 to develop evolutionary models of the sites based on geomorphological inferences detailed archaeological prospection 103 trenches geomorphologic mapping stratigraphic studies 36 logs and ground penetration radar gpr surveys on five profiles indicate that the location of the settlement source of the necropolis is outside the construction perimeter farther to the southeast the pre holocene evolution of the fluvial landscape is marked by the development of two terraces t1 and t2 that host the early palaeolithic remains in the area ca 128 71 ka the holocene evolution of the landscape was marked by the emplacement of the nora river flood plain covered by alluvial fans after ca 9 ka bp cal bc 8252 7787 subsequently neolithic pebble pits dated ca 5 3 ka bp cal bc 4261 3963 and 4372 4051 were constructed on t2 at the area reoccupied as a necropolis during the late roman period 1590 45 years bp cal ad 382 576 coeval human activity during the late roman period at 1670 60 years bp cal ad 320 430 is also recorded by channel infill sediments in a minor site at the margin of an alluvial fan located to the southeast this work shows that a rescue archaeological study can be significantly enhanced by the implementation of multidisciplinary scientific studies in which the holistic view of geomorphologic settings provide key insights into the geometry and evolution of archaeological sites

bone weathering in the tropical rain forest abstract bones deposited on the rain forest floor exhibit distinctly different surface modifications from those found in savannas the development of weathering cracks is considerably slower than in more open environments suggesting that the dearth of rain forest fossil assemblages is not caused by increased weathering in these environments ubiquitous surface modifications include green plant growth on the bone s exposed surfaces termite caused pitting and extensive rodent gnawing if preserved on fossil bone these modifications may serve as palaeoenvironmental indicators

geomorphological processes and their palaeoenvironmental significance at the shum laka cave bamenda western cameroon abstract the climatic environmental history of the shum laka cave western cameroon and its surroundings has been established by means of geomorphological sedimentological and botanical data tied in a well dated stratigraphical sequence since 30 000 yr bp this mountainous area 1 650 2 000 m asl has never been a desert nor a tropical forest temperatures seldom significantly dropped below freezing mountain forest with galleries along the water courses and grassland in between prevailed most of the time a certain evolution can be observed from 31 000 to 20 000 yr bp annual precipitation was initially higher than today and subsequently somewhat lower from 13 000 yr bp onwards humidity and temperatures increased again around 9 000 yr bp they probably reached higher values than today from 9 000 yr bp human activity became very apparent this may have influenced the evolution of the natural landscape and obliterated climatological effects this evolution has been interrupted three times by dryer climatic conditions which each time lasted for only 1 or 2 millennia respectively at 33 000 at 11 000 and at 3 000 yr bp another important less humid episode occurred between 6 070 and 3 180 yr bp finally there is some evidence for a drier period between 8 480 and 7 150 yr bp the climatic evolution established for the shum laka cave confirms and refines former data from the area and is in good agreement with data from barombi mbo and chad

phytoliths from archaeological sites in the tropical forest of ituri democratic republic of congo abstract phytoliths record late quaternary vegetation at three archaeological sites in the ituri rain forest the oldest deposits dated to ca 19 000 to 10 000 14c yr b p contain abundant phytoliths of grasses but also enough arboreal forms to show that the landscape was forested the late glacial forests may have had a more open canopy than today s younger phytolith assemblages show that the northeast congo basin was densely forested throughout the holocene archaeological materials among the phytoliths show that people lived in this region during the pleistocene therefore pleistocene and holocene prehistoric foragers probably inhabited tropical forests of the northeast congo basin many millennia before farming appeared in the region

the nature of the mistral observations and modelling of two map events two mistral events observed in 1999 during the mesoscale alpine programme map are studied using observational data and high resolution mesoscale model simulations from the us navy s coupled ocean atmosphere mesoscale prediction system coamps radiosondes suggested that both mistral wind events were associated with the passage of cold fronts and post frontal air descent eurosat rapidscan images indicated a stationary and persistent cloud edge along the lee of the massif central the cloud edge marks the beginning of mistral flow acceleration and descent according to coamps simulations narrow persistent cloud banners were identified trailing from the mont lozere in the massif central during both mistral events coamps indicated that these cloud banners were associated with a deeper turbulent boundary layer in wakes induced by hydraulic jumps the cloud banner and wake defined the western boundary of the mistral analysis of dropsonde data and in situ flight data indicated the presence of a sharp shear line separating the cold severe mistral wind from the warm calm wake flow to the lee of the french alps trajectory analysis of model data suggested that air parcels on the two sides of the shear line had different histories copyright 2003 royal meteorological society

temperature and precipitation climate at the equilibrium line altitude of glaciers expressed by the degree day factor for melting snow several authors relate accumulation or precipitation at the glacier equilibrium line altitude ela to summer mean temperature using exponential or power law functions i analyze the accumulation temperature relation at the ela with a degree day model using data from the 1992 paper by a ohmura and others the dataset includes estimates at the ela of winter balance and of winter balance plus summer precipitation which represent respectively low and high estimates of annual accumulation which is seldom measured the ohmura dataset only lists summer mean temperature but i recover monthly temperatures for the whole year for 66 of the glaciers by assuming sinusoidal temperature variation through the year and using annual temperature range from a gridded climatology monthly degree day sums are then estimated from monthly mean temperature and summed to give annual totals so degree day factors for melting snow at the ela are obtained the degree day factors fall close to those reported in the literature for glacier snowmelt with averages of 3 5 1 4 and 4 6 1 4 mm d 1 k 1 for low and high accumulation estimates on the 66 glaciers the degree day model gives a family of accumulation temperature curves that depend upon the annual temperature range representing the contrast between maritime and continental climates

impact of mesoscale meteorological processes on anomalous radar propagation conditions over the northern adriatic area the impact of mesoscale structures on the occurrence of anomalous propagation ap conditions for radio waves including ducts super refractive and subrefractive conditions were studied the chosen meteorological situations are the bora wind and the sporadic sea land breeze sb lb during three selected cases over a large portion of the northern adriatic for this purpose we used available radiosoundings and numerical mesoscale model simulations of real cases and their sensitivity tests at a horizontal resolution of 1 5 km and 81 vertical levels the model simulated the occurrences of ap conditions satisfactorily although their intensities and frequency were underestimated at times certain difficulties appeared in reproducing the vertical profile of the modified refractive index which is mainly dependent on the accuracy of the modeled humidity the spatial distributions of summer ap conditions reveal that the surface layer above the sea roughly between 30 and 100 m asl is often covered by super refractive conditions and ducts the sb is highly associated with the formations of ap conditions i in the first 100 m asl where trapping and super refractive conditions form because of the advection of cold and moist air and ii inside the transition layer between the sb body and the elevated return flow in the form of subrefractive conditions when deep convection occurs all three types of ap conditions are caused by the downdraft beneath the cumulonimbus cloud base in its mature phase that creates smaller but marked pools of cold and dry air the bora wind usually creates a pattern of ap conditions associated with the hydraulic jump and influences distribution of ap conditions over the sea surface

low level potential vorticity and cyclogenesis to the lee of the alps abstract high resolution numerical model simulations over the alpine region are presented that reveal the presence of low level elongated bands of potential vorticity pv downstream of high topography these pv streamers or pv banners occur when the synoptic scale wind turns into a direction across the alps individual pairs of banners with anomalously positive and negative values of pv can be attributed to flow splitting either on the scale of the whole of the alps primary banners or on that of individual massifs and peaks of the model topography secondary banners the pv bands have amplitudes of up to 2 5 and 5 pvu a width of 50 150 km can attain a length of up to 1500 km and extend in the vertical from the surface up to the 500 hpa level on occasions the pv banners are associated with zones of enhanced horizontal wind shear the analysis of daily output from the operational nwp model run of the swiss meteorological institute also demonstrates that such pv streamers are a frequent feature

recent evolution of marmolada glacier dolomites italy by means of ground and airborne gpr surveys abstract a 10 year long evolution of ice thickness and volume of the marmolada glacier is presented quantitative measurements have been performed by using two different ground penetrating radar gpr datasets a ground based survey using two different ground coupled systems equipped with 100 mhz and 35 mhz antennas was performed in 2004 in 2015 the dataset was collected by using a helicopter borne step frequency gpr equipped with a 100 mhz antenna through a critical discussion of the two different methodologies we show how both approaches are useful to estimate the ice volume within a glacier as well as its morphological characteristics and changes with time even if datasets are acquired in different periods of the year the observed 2004 2014 ice volume reduction of the marmolada glacier is equal to about 30 while the area covered by ice decreased by about 22 the glacier is now splitted in several separated units it is very likely that the fragmentation of the marmolada glacier observed in the period 2004 2014 was accelerated due to irregular karst topography by applying the observed 2004 2014 ice melting trend for the future although the marmolada glacier might behave slightly differently compared to glaciers on non karstic terrains owing to dominant vertical subglacial drainage it will likely disappear by the year 2050 only few isolated very small and thin ice patches will eventually survive due to avalanche feeding and shading at the foot of the north facing cliffs

terrain influences on synoptic storm structure and mesoscale precipitation distribution during ipex iop3 abstract the influence of topography on the evolution of a winter storm over the western united states and distribution of precipitation over northern utah are examined using data collected during the third intensive observing period iop3 of the intermountain precipitation experiment ipex the analysis is based on high density surface observations collected by the mesowest cooperative networks special radiosonde observations wind profiler observations next generation weather radar nexrad data and conventional data a complex storm evolution was observed beginning with frontal distortion and low level frontolysis as a surface occluded front approached the sierra nevada as the low level occluded front weakened the associated upper level trough moved over the sierra nevada and overtook a lee trough the upper level trough which was forward sloping and featured more dramatic moisture than temperature gradients then moved across nevada with a weak surface reflection as a pressure trough over no

cave sediments upper pleistocene stratigraphy and mousterian facies in cantabrian spain abstract archaeological sediments are analysed from karst cave columns in cantabrian spain cueva morin el pendo the castillo cave complex including la flecha las chimeneas la pasiega las monedas hornos de la pena and cobalejos external sediment influx including loess is calibrated by an index of cave and slope run off energy while other features slope and roof rubble chemical precipitates cryoturbations fine soil derivatives and cultural components are discussed the key sequences morin el pendo castillo are each interpreted in local terms and then combined into a regional climatostratigraphy that includes 40 environmental phases within deep sea isotope stages 2 5 trends in run off energy reflecting slope stability temperature and summer moisture are rarely in phase indicating complex environmental change mid pleistocene and older deposits exist but have largely been destroyed explaining the apparent absence of acheulian settlement mousterian occupation is verified by isotope stage 5b and two or three mousterian facies that span 25 50 000 years are coeval in several caves regardless of the direction of climatic oscillations this suggests the flexible lithic technology of a single population maintaining an adaptive steady state despite repeated environmental changes by contrast the distinct upper palaeolithic industries each span only a few millennia but in part overlap temporally within the region between 35 000 and 9500 bp

the formation of fire residues associated with hunter gatherers in humid tropical environments a geo ethnoarchaeological perspective this work was supported by the people programme marie curie actions of the european union s seventh framework programme fp7 2007 2013 under rea agreement n 623293 granted to d e f at the mcdonald institute for archaeological research university of cambridge radiocarbon dating was also funded by the exilarch s foundation for the dangoor research accelerator mass spectrometry laboratory d reams

february 2003 marine atmospheric conditions and the bora over the northern adriatic 1 a winter oceanographic field experiment provided an opportunity to examine the atmospheric marine conditions over the northern adriatic mean february winds are from a northeasterly direction over most of the adriatic and a more northerly direction along the western coast wind speeds are fastest in jets over the ne coast during bora events and weakest in the mid northwestern adriatic diurnal air temperature cycles are smallest on the ne coast and largest in the midwestern adriatic the maximum sea air difference is 10 c on the eastern coast and near zero on the midwestern adriatic boras are northeasterly from wind events that sweep off croatia and slovenia bringing slightly colder and drier air over the northern adriatic the main bora season is december to march winter 2002 2003 was normal for bora events synoptic scale temporal variations are correlated over the northern adriatic fastest bora winds and highest wind stress over the northern adriatic is concentrated in four topographically controlled jets the strongest is the senj jet while the trieste jet extends across the entire northern adriatic between each two jets is a weak wind zone the greatest mean net heat loss is in bora jets in the ne adriatic where it was 438 w m 2 and is weakest in the midwestern northern adriatic where it was near zero wind stress is concentrated over the ne half of adriatic in four bora jets while wind stress is weak in the nw adriatic there is significant variation in wind stress mean and standard deviation structure over the northern adriatic with each bora event

velocity analysis from common offset gpr data inversion theory and application to synthetic and real data we implemented a procedure to estimate the electromagnetic em velocity using common offset ground penetrating radar gpr data the technique is based on the inversion of reflection amplitudes to compute the series of reflection coefficients used to estimate the velocity in each interpreted layer the proposed method recursively calculates the incident angles at any interface taking into account the offset between antennas and needs as input in addition to the picked amplitudes values a reference amplitude for each analysed gpr trace and a velocity value for the first shallowest layer the latter two parameters can be estimated directly from the available data or can be better constrained by further dedicated gpr acquisitions or by additional direct measurements we critically evaluated the performances for both synthetic and real data acquired with different antenna frequencies and we demonstrated that the new method can be applied in several real situations despite the necessary approximations and simplifying hypotheses the velocity values calculated for each layer are consistent with direct information and with cross validations obtained considering profiles acquired using different antennas and various path directions tests of the method on synthetic and real data sets show that the errors in the calculated velocity fields are quite low and comparable with more demanding velocity analysis techniques the obtained em velocity field is crucial in many processing steps such as for example true amplitude recovery depth conversion and imaging and provide essential information to characterize the subsurface materials

gap winds and wakes sar observations and numerical simulations the nature of terrain induced gap winds and wakes in the atmosphere is examined using surface wind data from synthetic aperture radar sar and the shallow water equations the shallow water model is used to predict the types of wake jet wind patterns that might occur behind an idealized pair of bell shaped hills with a gap between them a regime diagram is constructed based on the width of the gap and the upstream froude number specific predictions of the model are found to compare moderately well with sar data from four examples of airflow near unimak island in the aleutian chain the model predicts the observed wakes and jets including jets that exceed the upstream speed theoretical analysis considers the relative importance of rising terrain and narrowing valley walls in the acceleration of gap winds wind speeds in the wake region are controlled by the bernoulli function and regional pressure gap winds therefore are streams of air that have avoided bernoulli loss over the terrain by passing through gaps the speed of gap winds can exceed the upstream speed only in ridgelike situations when the regional leeside pressure is lower than the upstream pressure

archaeological site formation in rain forests insights from the ituri rock shelters congo abstract this contribution complements the existing literature on rock shelter geoarchaeology and site formation processes by presenting data from 10 granite rock shelters in a tropical rain forest environment geological taphonomic pedological and archaeological data are used to assess the geomorphological evolution of rock shelters in the ituri rain forest northeast democratic republic of congo mechanisms of sediment production and deposition soil formation and related site formation processes were investigated the implications for the preservation of archaeological materials and stratigraphic resolution are discussed rock shelters in the tropical environment of the congo basin are formed by mechanical and chemical denudation of large granite boulders the current geomorphological cycle of rock shelter formation and collapse dates to the late pleistocene and may have been accelerated by anthropogenic forces the sedimentary record includes in situ breakdown products from the rock shelter walls while off site sources are represented by a minor influx of colluvium soil forming forces have acted on these matrices humans introduced charcoal phytoliths endocarps shell animal and human bone as well as inorganic materials such as stone ceramics and metal lags of archaeological materials are common under driplines where fine sediments have been washed away and include artefacts of different ages there is no evidence of extensive bioturbation but limited disturbance by roots burrowing animals and termites has been documented although there is some horizontal and vertical movement of prehistoric artefacts the post depositional translocation of materials is not significant we conclude that the stratigraphic integrity of these granite rock shelter sites with multiple archaeological horizons and the potential for the long term preservation of organic materials in a tropical environment are better than previously thought

little ice age glaciers in the balkans low altitude glaciation enabled by cooler temperatures and local topoclimatic controls moraine ridges are present in the highest cirques of the durmitor massif in montenegro and post date the widespread pleistocene moraines of this area lichenometry suggests that at least eight glaciers were present in the 19th century and correlate with the culmination of the little ice age in the european alps cooler temperatures combined with local topoclimatic controls including windblown and avalanching snow as well as shading were crucial for the formation and survival of these glaciers below the regional equilibrium line altitude the resultant regional equilibrium line altitude ela was positioned close to the highest peaks between 2400 and 2500 m with local controls such as avalanche windblown snow and shading depressing the ela in the northern cirques to 2130 2210 m this ela position was very low for this latitude and lower than for most glaciers in the european alps at any time during the holocene and even equivalent to many alpine glaciers during the younger dryas today one glacier still survives in montenegro in a deep northeast facing cirque characterized by the largest combined areas of potential avalanche and windblown snow copyright 2009 john wiley sons ltd

geoarchaeological research in the humid tropics a global perspective abstract geoarchaeological research is now commonly undertaken as an integral component of archaeological investigations across much of the world however in humid tropical regions there is a relative shortfall of this earth science approach to understanding archaeological records in these regions where hot and humid conditions prevail for significant parts of the year sedimentological records are prone to high levels of diagenesis bioturbation and weathering this means that understanding and quantifying archaeological site formation processes can be very challenging because we may not have sufficient existing data with which to decipher the stratigraphic and microstratigraphic features recorded in these sequences in this paper we introduce a special issue of journal of archaeological science in which we showcase a selection of geoarchaeological research from across the equatorial regions of five continents highlighting the types of stratigraphic sequences and sedimentological features that are likely to be encountered and evaluating the tools that can be employed to maximise the geoarchaeological potential of these unique records additionally we use this opportunity to review geoarchaeology in the humid tropics from a global perspective outlining the main problems that geoarchaeologists face working in these environments and the techniques available with which to mitigate them

recent behaviour of the debeli namet glacier durmitor montenegro a small cirque glacier is present in a north east facing cirque on the mountain of sljeme 2455 m a s l in the durmitor massif montenegro sediment ridges in front of this glacier are interpreted as moraines and can be attributed to recent glacier activity over the past 130 years lichenometry was applied to determine the relative ages of different moraines using aspicilia calcarea agg one set of moraines dates from about 1878 ad whilst another set of inner moraines dates from about 1904 ad the most recent moraines appear to have formed within the last 11 years in front of an active glacier margin copyright 2007 john wiley sons ltd

alpine gravity waves lessons from map regarding mountain wave generation and breaking the two month special observing period of the mesoscale alpine programme map in autumn 1999 included a variety of complex mountain wave events seven wave events were carefully analyzed compared with numerical models and described in published papers these detailed investigations revealed some common dynamical elements i e the importance of low level processes involving the slow moving boundary layer low level wind shear causing either wave absorption or decoupling spilling upstream blocking and latent heat release based on these studies it is clear that any quantitative prediction of mountain wave generation must take full account of these lower troposphere processes the newest numerical models show significant skill in simulating these effects using these models the climatology of waves over the alps can be studied copyright 2007 royal meteorological society

size specific steady state accumulation area ratio an improvement for equilibrium line estimation of small palaeoglaciers abstract characteristic distribution of the steady state accumulation area ratio aar0 of valley and corrie glaciers was investigated in a global dataset comprised of 46 glaciers there is a positive relationship between aar0 and glacier area with smaller glaciers having lower values of aar0 compared with larger glaciers the relationship between glacier area s and steady state aar of studied glaciers can be optimally described by a logarithmic regression equation this relationship is thought to be a globally valid approximation if the size of the glacier is not smaller than 10 1 km2 in the case of palaeoglaciers an aar0 value of 0 44 0 07 is best applied on glaciers with areas in the range 0 1 1 km2 0 54 0 07 for glaciers covering areas between 1 and 4 km2 and 0 64 0 04 for glaciers larger than 4 km2 this assumes insignificant debris cover for the investigated palaeoglaciers the proposed size specific aar0 values take into account the geometric hypsometric properties of palaeo glaciers the results have major importance for palaeoglaciological reconstructions in many regions of former marginal niche glaciation characterized by small former glaciers

aerial observations of the yugoslavian bora abstract the first aircraft observations of the bora in yugoslavia were accomplished during the alpex project in 1982 data from all five alpex bora flights have been analyzed in a comparative study of bora structure although the bora varies considerably in depth in the strength of the incoming low level flow and in the direction of the winds aloft several common features are evident these include upstream descent and acceleration beginning where the mountains rise an approximate coincidence between the depth of the uppermost descending streamline and the wind reversal level upstream when a reversal exists a decoupling of the flow aloft associated with a splitting of the inversion and the formation of a thick mixed layer downstream a narrow region of intense turbulence and an ascending jet just downstream of the plunging bora the bora structure is similar in many respects to the boulder windstorm internal hydraulic theory taking into account the decoupling effect of the intermediate layer a

the reshaping of the south west adriatic margin by cascading of dense shelf waters abstract the south west adriatic margin sam includes a steep and morphologically complex continental slope stretching about 600 km from the pelagosa sill to the otranto strait the margin is clearly dissected by submarine slides active fault systems e g the gondola deformation belt numerous shallowly incised and relatively straight canyons located south of bari canyon and a variety of large scale erosional and depositional features this area is seasonally impacted by dense shelf water forming in the north adriatic through wind forced winter cooling moving south along the western side of the basin and cascading across the south adriatic slope the area has been investigated through multibeam surveys integrated by high resolution seismic stratigraphic data resolving glacial and post glacial deposits this paper gives a detailed and comprehensive description of the sam seafloor morphology to document how the process of dense shelf water cascading concurs to a thorough restyling of the submarine landscape by interacting with the pre existing and markedly differentiated morphologies and sediment distribution we focus on depositional and erosional features such as giant sediment drifts down to 1200 m water depth muddy and sandy sediment waves comet marks against pre existing slide blocks furrow fields against steep slopes large scours at the shelf edge and large erosional moats adjacent to major morphological barriers the analysis of the bedform orientation and spatial distribution indicates that the downslope cascading bottom currents dominantly directed to the se encounter a straight upper slope oriented north south in the north and progressively more east west proceeding to the south as the slope orientation becomes more e w it also appears more dissected by small scale canyons active during glacial times in the latter area therefore the dense shelf waters follow a slope parallel direction almost perpendicular to the pre existing slope canyons as a consequence erosional furrows develop perpendicular to the canyon flanks and some of the canyon heads become disconnected from the main canyon downslope

the physical basis of glacier volume area scaling ice volumes are known for only a few of the roughly 160 000 glaciers worldwide but are important components of many climate and sea level studies which require water flux estimates a scaling analysis of the mass and momentum conservation equations shows that glacier volumes can be related by a power law to more easily observed glacier surface areas the relationship requires four closure choices for the scaling behavior of glacier widths slopes side drag and mass balance reasonable closures predict a volume area scaling exponent which is consistent with observations giving a physical and practical basis for estimating ice volumes glacier volume is insensitive to perturbations in the mass balance scaling but changes in average accumulation area ratios reflect significant changes in the scaling of both mass balance and ice volume

on the onset of bora and the formation of rotors and jumps near a mountain gap this study investigates the onset phase of a strong adriatic bora windstorm that occurred on 4 april 2002 the target area is a gap about 20 km wide embedded in the coastal mountain barrier of the dinaric alps that favours strong jet like winds airborne aerosol back scatter lidar measurements on board the dlr falcon research aircraft together with surface and upper air observations are used to verify high resolution numerical experiments conducted with the mesoscale atmospheric model rams and a single layer shallow water model swm especially during the breakthrough phase of the bora the flow at the gap exit exhibits a complex spatial structure and temporal evolution on a transect through the centre of the gap a hydraulic jump forms this is located close to the coast throughout the night and starts to propagate downstream in the early morning on a transect through the edge of the gap a lee wave induced rotor becomes established due to boundary layer separation it starts to propagate downstream about two hours after the jump this flow evolution implies that the onset of strong winds at the coast occurs several hours earlier downstream of the centre of the gap than downwind of the edge of the gap consequently the wind field in the vicinity of rijeka airport located downwind of the gap is strongly inhomogeneous and transient and represents a potential hazard to aviation measured bora winds at the surface exceed 20 ms 1 and the simulated wind speed in the gap wind layer exceeds 30 ms 1 the simulated turbulent kinetic energy exceeds 10 m2 s 2 rams indicates that wave breaking near a critical level is the dominant mechanism for the generation of the windstorm gap jets can be identified downstream of several mountain passes the simulated wave pattern above the dinaric alps the wave decay with height due to directional wind shear and the strong flow descent on the leeward side of the barrier are supported by measured back scatter intensities basic bora flow features including gap jets and jumps are remarkably well reproduced by swm simulations the rams reference run captures observed flow phenomena and the temporal flow evolution qualitatively well a cold low level bias an overestimated bora inversion strength and a slightly too early bora onset are probably related to insufficient turbulent mixing in the boundary layer the amplitude of trapped gravity waves the time of the bora breakthrough and the inversion strength are found to be quite sensitive to the turbulence parametrization copyright 2008 royal meteorological society

lee vortex formation in free slip stratified flow over ridges part ii mechanisms of vorticity and pv production in nonlinear viscous wakes abstract the formation of orographic wakes and vortices is studied within the context of numerically simulated viscous flow with uniform basic state wind and stability past elongated free slip ridges the viscosity and thermal diffusivity are sufficiently large that the onset of small scale turbulence is suppressed it is found in part i of this study that wake formation in the viscous flow is closely tied to the dynamics of a low level hydraulic jump like feature in the lee of the obstacle here the role of the hydraulic jump in producing the vorticity and potential vorticity pv of the viscous wake is considered a method for diagnosing vorticity production is developed based on a propagator analysis of the lagrangian vorticity equation that generalizes cauchy s formula for the evolution of vorticity in a lagrangian framework application of the method reveals that the vertical vorticity of the wake originates through baroclinic generation and tilting in the mountain wave upstream of the jump however

the missing link between terrain induced potential vorticity banners and banded convection abstracton 1 february 2014 the southern side of the alps was affected by a severe snowstorm that forced authorities to issue the highest level of avalanche danger in southern parts of austria the northern side of the alps was mostly dry nevertheless radar imagery captured the evolution of quasi steady convective cloud bands over the northern alpine foreland with a remarkable length of up to 300 km this study illuminates the processes that generated these cloud bands based on numerical simulations the storm was associated with a deep large scale trough that caused strong southwesterly cross alpine flow orographic precipitation on the southern side and foehnlike subsidence on the northern side of the alps orographic potential vorticity pv banners developed at small scale topographic features embedded in the alps and extended downstream over the northern alpine foreland convective cloud bands were aligned parallel to these pv banners they formed in an environment of inertial instability negativ

lapa das boleiras rockshelter stratigraphy and formation processes at a paleoamerican site in central brazil abstract lapa das boleiras rockshelter a paleoamerican archaeological site in central brazil was intensely occupied by humans from 10 000 14c bp 11 8 cal kyr bp until approximately 7500 14c bp 8 4 cal kyr bp in this paper we present some interpretations about the formation processes operating on the site one of our main conclusions is that the bulk of accumulated sediments at the site is of anthropogenic origin they are constituted by volumetrically significant quantities of plant ash remains what is somewhat unexpectedly in view of prevailing models about the lifestyle of paleoamerican hunter gatherers in south america the evidence we discuss below is also consistent with paleoenvironmental data that suggest a dry period during the mid holocene in the region probably leading to a decrease in human occupation araujo a g m neves w pilo l b atui j p 2005 holocene dryness and human occupation in brazil during the archaic gap quaternary research 64 298 307 we surmise that both factors underpin a surprising reduction in sediment accumulation at the site during the mid holocene

wave breaking induced surface wakes and jets observed during a bora event 1 an observational and modeling study of a bora event that occurred during the field phase of the mesoscale alpine programme is presented research aircraft in situ measurements and airborne remote sensing observations indicate the presence of strong low level wave breaking and alternating surface wakes and jets along the croatian coastline over the adriatic sea the observed features are well captured by a high resolution coamps simulation analysis of the observations and modeling results indicate that the long extending wakes above the boundary layer are induced by dissipation associated with the low level wave breaking which locally tends to accelerate the boundary layer flow beneath the breaking farther downstream of the high peaks a hydraulic jump occurs in the boundary layer which creates surface wakes downstream of lower terrain passes the boundary layer flow stays strong resembling supercritical flow

permafrost conditions in the mediterranean region since the last glaciation the relatively warm climate conditions prevailing today in the mediterranean region limit cold geomorphological processes only to the highest mountain environments however climate variability during the late pleistocene and holocene has led to significant spatio temporal variations of the glacial and periglacial domain in these mountains including permafrost conditions here we examine the distribution and evolution of permafrost in the mediterranean region considering five time periods last glaciation deglaciation holocene little ice age lia and present day the distribution of inactive permafrost derived features as well as sedimentary records indicates that the elevation limit of permafrost during the last glaciation was between 1000 m and even 2000 m lower than present permafrost was also widespread in non glaciated slopes above the snowline forming rock glaciers and block streams as well as meter sized stone circles in relatively flat summit areas as in most of the northern hemisphere the onset of deglaciation in the mediterranean region started around 19 20 ka the ice free terrain left by retreating glaciers was subject to paraglacial activity and intense periglacial processes under permafrost conditions many rock glaciers protalus lobes and block streams formed in these recently deglaciated environments though most of them became gradually inactive as temperatures kept rising especially those at lower altitudes following the younger dryas glacial advance the early holocene saw the last massive deglaciation in mediterranean mountains accompanied by a progressive shift of permafrost conditions to higher elevations it is unlikely that air temperatures recorded in mediterranean mountains during the holocene favoured the existence of widespread permafrost regimes with the only exception of the highest massifs exceeding 2500 3000 m lia colder climate promoted a minor glacial advance and the spatial expansion of permafrost with the development of new protalus lobes and rock glaciers in the highest massifs finally post lia warming has led to glacial retreat disappearance enhanced paraglacial activity shift of periglacial processes to higher elevations degradation of alpine permafrost along with geoecological changes

glaciokarst landforms and processes of the southern dinaric alps glaciokarst is a landscape which combines karst features and hydrology as well as inherited glacial features it is a result of glaciation upon a karst geomorphological system the relationship between glaciers and karst is rather poorly known and inadequately recognized this research focuses on three distinct karst areas along the adriatic coast in the southern dinaric alps that were affected by the quaternary glaciations an insight into specific glaciokarst processes and surface features was provided through the study of the areas of the lovcen orjen and vele mountains a glaciokarst geomorphology is in general well preserved due to the prevailing vertically oriented chemical denudation following de glaciation and almost the entire absence of other surface processes typical glacial erosional features are combined by a variety of depressions which are the result of a karstic drainage of sub glacial waters the majority of glacial deposits occur as extensive lateral terminal moraine complexes which are often dissected by smaller breach lobe moraines on the external side of the ridge those moraine complexes are likely to be a product of several glacial events which is supported by complex depositional structures according to the type of glacial depositional features the glaciers in the study areas were likely to have characteristics of moraine dammed glaciers due to vertical drainage ice marginal fluvial processes were unable to evacuate sediment fluvial transport between glacial and pro glacial systems in karst areas is inefficient nevertheless some sediment from the glacier margin is washed away by the pro glacial streams filling the karst depressions and forming piedmont type poljes copyright 2015 john wiley sons ltd

influence of terrain resolution on banded convection in the lee of the rocky mountains abstracton 16 17 february 2007 snowbands formed in the lee of the rocky mountains in wyoming colorado and nebraska on the anticyclonic shear side of a midlevel jet streak two types of bands were prevalent a longer wider band associated with frontogenesis along an equatorward moving cold front major band and multiple shorter narrower bands farther poleward minor bands to understand how the upstream terrain affected the occurrence and intensity of the bands multiple mesoscale model simulations were performed in which the terrain was incrementally smoothed the evolutions of the synoptic patterns were similar in all simulations that included topography but the synoptic pattern differed and no bands developed in a simulation with a flat land surface these results allowed a focus on the changes to the banded precipitation due to the terrain resolution remarkably although the exact location of the bands differed from run to run the bands in all simulations with topography were in roughly the s

timing of glacial retreat in the wicklow mountains ireland conditioned by glacier size and topography this paper presents 170 schmidt hammer exposure ages from moraine boulders and glacially sculpted bedrock to reveal the post last glacial maximum lgm history of the wicklow mountains ireland these data suggest that large ice masses survived for 4 7 ka after retreat of the irish sea ice stream and were sustained by summit ice fields until 16 6 ka post lgm retreat was dynamic with re advance moraines deposited in response to heinrich stadial 1 however these events reflect short term ice front oscillations 1 ka during the long term retreat phase retreat from re advance positions was synchronous across the range and paced by climate with time progressive deglaciation from low to high elevation in contrast marked asynchroneity in the timing of younger dryas deglaciation is closely linked to snow redistribution and indicates that for small cirque glaciers 1 km2 topography can exert the primary control on glacier survival this result has important implications for palaeoclimate econstructions as cirque glacier dynamics may be unrelated to climate this is further complicated by post depositional processes which can result in moraine ages e g 10be which post date retreat future palaeoclimate studies should prioritise cirque glaciers where snow contributing areas are small and where postdepositional disturbance is limited matrix poor boulder rich moraines

little ice age glaciation and current glaciers in the iberian peninsula little ice age lia glacier advance has been registered in three of the main iberian high mountain areas pyrenees picos de europa and sierra nevada during the lia three different glacial env

numerical simulation of flow diversion around the pyrenees a tramontana case study abstract the intensive observing period iop 6 of the pyrenees experiment pyrex has been simulated with a hydrostatic three dimensional model the pyrex iop 6 was devoted to the observation of a regional wind the tramontana which blows in the vicinity of the pyrenees mountains at the french spanish border under northerly synoptic wind conditions the low level flow frequently splits around the pyrenees barrier 400 km long and 3000 m high with the eastern branch of the flow favored by coriolis effect forming the tramontana model results are consistent with the tramontana climatology and in good agreement with the pyrex observations at all the different stages of the tramontana development in the blocking zone where the model reproduces the observed reversed flow as well as its disappearance later in the course of the simulation in the acceleration zone where the model gives accurate wind intensity and direction at the land sea transition where the development of an internal boundary layer is

latest pleistocene and holocene glacier variations in the european alps in the alps climatic conditions reflected in glacier and rock glacier activity in the earliest holocene show a strong affinity to conditions in the latest pleistocene younger dryas glacier advances in the alps related to younger dryas cooling led to the deposition of egesen stadial moraines egesen stadial moraines can be divided into three or in some cases even more phases sub stadials moraines of the earliest and most extended advance the egesen maximum stabilized at 12 2 1 0 ka based on 10be exposure dating at the schonferwall tyrol austria and the julier pass outer moraine switzerland final stabilization of moraines at the end of the egesen stadial was at 11 3 0 9 ka as shown by 10be data from four sites across the alps from west to east the sites are piano del praiet northwestern italy grosser aletschgletscher central switzerland julier pass inner moraine eastern switzerland and val viola northeastern italy there is excellent agreement of the 10be ages from the four sites in the earliest holocene glaciers in the northernmost mountain ranges advanced at around 10 8 1 1 ka as shown by 10be data from the kartell site northern tyrol austria in more sheltered drier regions rock glacier activity dominated as shown for example at julier pass and larstig valley tyrol austria new 10be dates presented here for two rock glaciers in larstig valley indicate final stabilization no later than 10 5 0 8 ka based on this data we conclude the earliest holocene between 11 6 and about 10 5 ka was still strongly affected by the cold climatic conditions of the younger dryas and the preboreal oscillation with the intervening warming phase having had the effect of rapid downwasting of egesen glaciers at or slightly before 10 5 ka rapid shrinkage of glaciers to a size smaller than their late 20th century size reflects markedly warmer and possibly also drier climate between about 10 5 ka and 3 3 ka conditions in the alps were not conducive to significant glacier expansion except possibly during rare brief intervals past tree line data from kaunertal tyrol austria in concert with radiocarbon and dendrochronologically dated wood fragments found recently in the glacier forefields in both the swiss and austrian alps points to long periods during the holocene when glaciers were smaller than they were during the late 20th century equilibrium line altitudes ela were about 200 m higher than they are today and about 300 m higher in comparison to little ice age lia elas the larstig rock glacier site we dated with 10be is the type area for a postulated mid holocene cold period called the larstig oscillation presumed age about 7 0 ka our data point to final stabilization of those rock glaciers in the earliest holocene and not in the middle holocene the combined data indicate there was no time window in the middle holocene long enough for rock glaciers of the size and at the elevation of the larstig site to have formed during the short infrequent cold oscillations between 10 5 and 3 3 ka small glaciers less than several km2 may have advanced to close to their lia dimensions overall the cold periods were just too short for large glaciers to advance after 3 3 ka climate conditions became generally colder and warm periods were brief and less frequent large glaciers for example grosser aletschgletscher advanced markedly at 3 0 2 6 ka around 600 ad and during the lia glaciers in the alps attained their lia maximum extents in the 14th 17th and 19th centuries with most reaching their greatest lia extent in the final 1850 1860 ad advance

climate at the equilibrium line of glaciers the relationships between temperature precipitation and radiation on glacier equilibrium lines are investigated using 70 glaciers for which the mass balance and meteorological observations have been carried out for sufficiently long periods it is found that the characteristic climate at glacier equilibrium lines can be described using the summer 3 months temperature in a free atmosphere annual total precipitation and the sum of global and long wave net radiation all of these are measured at or very near the equilibrium line altitudes then it is shown how the shift of the equilibriumline will occur as a result of a climatic change finally the effect of the shift of the equilibrium line on the annualmean specific mass balance is analytically derived and compared with observations the present results make it possible to identify the altitudes in climate models where glacierization should begin and to evaluate the mass balance changes as a result of possible future changes in the climate

high resolution mapping of bora winds in the northern adriatic sea using synthetic aperture radar 1 the adriatic sea is regularly subjected to strong bora wind events from the northeast during winter the events have a strong effect on the oceanography in the adriatic driving basin scale gyres that determine the transport of biogeochemical material and extracting large amounts of heat the bora is known to have multiple surface wind jets linked to the surrounding orography and have been the focus of many studies but it has not been possible to describe the detailed spatial structure of these jets by in situ observations using high resolution spaceborne radarsat 1 synthetic aperture radar sar images collected during an active bora period 23 january 16 february 2003 we created a series of high resolution 300 m maps of the wind field the obtained winds show reasonable agreement with several in situ wind observations with an rms wind speed error of 3 6 m s slightly higher than the 2 3 m s errors reported in previous studies these sar images reveal the spatial structure of the bora wind in unprecedented detail showing several new features in the senj region of croatia several images show rhythmic structure with wavelengths of 2 3 km that may reflect bora pulsation seen at fixed locations by previous investigators along the italian coast several images show a wide 20 30 km band of northwesterly winds that abruptly change to the northeasterly bora winds further offshore meteorological model results suggest that these northwesterly winds are consistent with those of a barrier jet forming along the italian apennine mountain chain

classification of cyclone tracks over the apennines and the adriatic sea abstract cyclones that appear in the adriatic sea basin strongly influence the climate and weather conditions in the area in particular apart from the usually mild climate cyclone activity in the adriatic and the central mediterranean sea provide both the main hydrological forcing and the trigger mechanisms for a range of extreme weather phenomena therefore a basic understanding of the cyclogenesis over the adriatic sea is essential in particular the classification of different types of cyclogenesis in the area is fundamental because it will help the understanding and prediction of the relevant weather phenomena in this study based on the analysis of the 4 yr 2002 05 operational european centre for medium range weather forecasts t511 dataset various types of cyclone tracks are classified and the mesocyclogenesis areas in the vicinity of the adriatic basin are isolated this analysis indicates that the following four types of cyclogenesis over the adriatic sea can be identified 1 type a cycl

geomorphic influence on small glacier response to post little ice age climate warming julian alps europe the evolution of glaciers and ice patches as well as the equilibrium line altitude ela since the little ice age lia maximum were investigated in the julian alps south eastern european alps including ice masses that were previously unreported twenty three permanent firn and ice bodies have been recognized in the 1853 km2 of this alpine sector covering a total area in 2012 of 0 385 km2 about one fifth of the area covered during the lia 2 350 km2 these features were classified as very small glaciers glacierets or ice patches with major contribution to the mass balance from avalanches and wind blown snow localized snow accumulation is also enhanced in the area due to the irregular karst topography the ice masses in the region are at the lowest elevations of any glaciers in the alpine chain and are characterized by low dynamics the elas of the two major lia glaciers canin and triglav have been established at 2275 10 m and 2486 10 m respectively by considering the reconstructed area and digital elevation model dem and using an accumulation area ratio aar of 0 44 0 07 typical of small cirque glaciers changes in the ela and glaciers extension indicate a decoupling from climate this is most evident in the smallest avalanche dominated ice bodies which are currently controlled mainly by precipitation the damming effect of moraine ridges and pronival ramparts at the snout of small ice bodies in the julian alps represents a further geomorphological control on the evolution of such ice masses which seem to be resilient to recent climate warming instead of rapidly disappearing as should be expected copyright 2016 john wiley sons ltd

dense water formation and bios induced variability in the adriatic sea simulated using an ocean regional circulation model a performance analysis of the nemomed8 ocean regional circulation model was undertaken for the adriatic sea during the period of 1961 2012 focusing on two mechanisms dense water formation dwf and the adriatic ionian bimodal oscillating system bios which drive interannual and decadal variability in the basin the model was verified based on sea surface temperature and sea surface height satellite measurements and long term in situ observations from several key areas the model qualitatively reproduces basin scale processes thermohaline driven cyclonic circulation and freshwater surface outflow along the western adriatic coast dense water dynamics and the inflow of ionian and levantine waters to the adriatic positive temperature and salinity biases are reported the latter are particularly large along the eastern part of the basin presumably because of the inappropriate introduction of eastern adriatic rivers into the model the highest warm temperature biases in the vertical direction were found in dense water collecting depressions in the adriatic indicating either an inappropriate quantification of dwf processes or temperature overestimation of modelled dense water the decadal variability in the thermohaline properties is reproduced better than interannual variability which is considerably underestimated the dwf rates are qualitatively well reproduced by the model being larger when preconditioned by higher basin wide salinities anticyclonic circulation in the northern ionian sea was modelled only during the eastern mediterranean transient no other reversals of circulation that could be linked to bios driven changes were modelled

aerial observations of hawaii s wake abstract under the influence of the east northeasterly trade winds the island of hawaii generates a wake that extends about 200 km to the west southwest during the harp project in july and august 1990 five wake surveys were carried out by the ncar electra the patterns of wind and aerosol concentration revealed by these flights suggest that hawaii s wake consists of two large quasi steady counterrotating eddies the southern clockwise rotating eddy carries a heavy aerosol load due to input from the k volcano at the eastern end of the wake the eddies are potentially warmer and more humid than the surrounding trade wind air several other features are discussed sharp shear lines near the northern and southern tips of the island dry and warm air bands along the shear lines a small embedded wake behind the kohala peninsula wake centerline clouds hydraulic jumps to the north and south of the island a descending inversion connected with accelerating trade winds and evidence for side to side wake mo

response of a mid latitude cirque glacier to climate over the last two decades mangaehuehu glacier mt ruapehu the recent loss of mountain glaciers in response to climate warming has been reported across a range of latitudes globally but the processes involved are not always straightforward in southern pacific mid latitudes twentieth century glacier fluctuations are thought to reflect the strength of westerly atmospheric circulation which brings increased precipitation leading to mass gains we present a study of the response of mangaehuehu glacier a cirque glacier on mt ruapehu to climate over the last two decades glacier surface area fluctuated in size over this period corresponding closely with mean end of summer snowlines in the southern alps the key control on glacier extent appears to be ablation season temperature itself controlled by regional atmospheric circulation including el nino southern oscillation interdecadal pacific oscillation ipo and to a lesser extent southern annular mode sam copyright 2011 john wiley sons ltd

convective snowbands downstream of the rocky mountains in an environment with conditional dry symmetric and inertial instabilities abstract convective snowbands moved slowly over wyoming and northern colorado on 16 17 february 2007 and produced up to 71 mm 2 8 in of snow that was unpredicted by operational numerical weather prediction models and human forecasters the northwest southeast oriented bands lasted for over 6 h comprising both a single major band more than 30 km wide and multiple minor bands about 10 km wide the convective bands initiated within the ascending branch of a secondary circulation associated with both near surface and elevated frontogenesis but the bands remained nearly stationary while the near surface frontogenesis moved quickly equatorward the bands occurred downstream of complex terrain on the anticyclonic shear side of a midlevel jet streak where conditional dry symmetric negative potential vorticity and inertial negative absolute vorticity instabilities were present to determine the mechanisms responsible for the development and organization of these bands simulations using a convectio

the randolph glacier inventory a globally complete inventory of glaciers the randolph glacier inventory rgi is a globally complete collection of digital outlines of glaciers excluding the ice sheets developed to meet the needs of the fifth assessment of the intergovernmental panel on climate change for estimates of past and future mass balance the rgi was created with limited resources in a short period priority was given to completeness of coverage but a limited uniform set of attributes is attached to each of the 198 000 glaciers in its latest version 3 2 satellite imagery from 1999 2010 provided most of the outlines their total extent is estimated as 726 800 34 000 km 2 the uncertainty about 5 is derived from careful single glacier and basin scale uncertainty estimates and comparisons with inventories that were not sources for the rgi the main contributors to uncertainty are probably misinterpretation of seasonal snow cover and debris cover these errors appear not to be normally distributed and quantifying them reliably is an unsolved problem combined with digital elevation models the rgi glacier outlines yield hypsometries that can be com bined with atmospheric data or model outputs for analysis of the impacts of climatic change on glaciers the rgi has already proved its value in the generation of significantly improved aggregate estimates of glacier mass changes and total volume and thus actual and potential contributions to sea level rise

complex bora flow in the lee of southern velebit the complexity of bora flow in the lee of southern velebit croatia is investigated by means of high resolution numerical simulations carried out with the us naval research laboratory s nrl coupled ocean atmosphere mesoscale prediction system coamps model the aim of this study is to identify reasons for the strong spatial variability of bora in the wider zadar region and the uncharacteristically weak bora in the city of zadar the primary focus is put on the severe bora episode of 20 december 2004 during which a sodar sonic detection and ranging system was operated at zemunik airport numerical results are verified against the available surface and upper air observations upstream conditions governing dynamics of this particular bora event are characterized by the presence of a mean state critical level at 3 4 km above mean sea level amsl defining the upstream bora layer low level airflow over zadar peninsula during this event displays marked temporal variability during the morning a highly three dimensional and unsteady wake i e region of reduced wind speed is established over zadar peninsula downstream of a hydraulic jump that forms in the lee of but not collocated with highest portions of the southern velebit terrain during its most extensive phase the wake scales the entire length of zadar peninsula in the horizontal and extends up to the critical level in the vertical a wake vortex develops as the flow reverses along the wake centreline in the evening hours an undular bore forms in the same location with large amplitude waves on top of it inducing boundary layer separation and rotors wake flow is affected both by changes in the upstream atmospheric structure and diurnal boundary layer evolution sensitivity experiments show that the influence of velebit s height is particularly strong governing the onset and strength of bora the terrain of zadar peninsula exerts a strong influence on the characteristics of the developed bora flow particularly when non hydrostatic effects are significant boundary layer separation is particularly sensitive to downstream orography copyright 2012 royal meteorological society

paleoclimatic implications based on equilibrium line altitude depressions of reconstructed younger dryas and holocene cirque glaciers in inner nordfjord western norway abstract relative to a present cirque glacier in innner nordfjord western norway equilibrium line altitude ela depressions for reconstructed cirque glaciers formed during the younger dryas 11 000 10 000 yr b p the erdalen event 9100 200 yr b p and the little ice age mid 18th century are calculated by the use of accumulation area ratio aar and compared to the corresponding values for plateau glaciers the temperature precipitation ela tp ela as reflected by plateau glaciers gives considerably larger ela depressions than use of the temperature precipitation wind ela tpw ela for cirque glaciers ela depressions during the younger dryas erdalen event and the little ice age thus strongly indicate that cirque glaciers are much more sensitive to changes in winter precipitation than plateau glaciers the difference in ela depressions of contemporaneous plateau and cirque glaciers during the younger dryas erdalen event and the little ice age suggests that winter precipitation was reduced to 59 7 71 6 and 88 7 compared to present values taken into account the reduced winter precipitation the corresponding mean ablation season temperature depressions were probably 4 3 0 3 3 0 0 2 0 3 and 1 4 0 3 0 2 c respectively

structure and dynamics of an alpine potential vorticity banner a detailed analysis is undertaken of the primary alpine shear zone that occurred on 1 october 1999 during the mesoscale alpine programme this shear zone emanates from the south western alpine tip in north westerly flow conditions develops in response to the alpine scale flow splitting and separates the northerly mistral wind to the south west of the alps from the quasi stagnant air within the alpine wake the study is based on in situ flight level and dropsonde data from two research aircraft the data are used for the construction of an objective analysis in a cross section perpendicular to the shear zone and for diagnostic computations of the potential vorticity pv flux between vertically stacked flight legs the observed flow structure is compared with simulation results of the swiss model and the non hydrostatic canadian mesoscale compressible community model mc2 operating at horizontal resolutions of 14 and 3 km respectively immediately downstream of the topography the observed shear zone has a surprisingly quasi steady structure that becomes evident provided a slow westward migration is accounted for further downstream the shear zone shows increased signs of transience near the surface it has an overall width of 150 km but narrows to about 25 km near the top of the mistral inversion at a height of 2 km detailed analysis shows that the shear zone has a complex substructure consisting of at least three positive and three negative pv filaments these shear lines are characterized by a pronounced vertical coherence in the mixed layer and throughout most of the inversion layer one of the banners is also evident in low level tracer constituents diagnostic computations of the pv flux along the banners using the generalized bernoulli theorem reveal that most of the associated pv flux is due to vertically oriented vorticity within the inversion layer within the shear zone there is a spanwise circulation of appreciable strength it consists of a deformation flow with the axes of deformation oriented perpendicular to the shear zone this deformation flow in effect squeezes the pv banners and thereby makes them resilient with respect to dissipation and barotropic instabilities detailed intercomparison with numerical model results shows that models with a grid spacing below 15 km are able to capture the overall structure of the shear zone the mc2 model in addition credibly replicates some of the finer scale sub structure of the shear zone in particular at low levels the high predictability and steadiness of the pv banners supports the idea that individual banners are generated by flow separation and or gravity wave breaking events upstream it is argued that the overall width of the shear zone is thus in effect determined by the geometry of the upstream topography and the dynamical processes that govern the downstream advection of the pv banners copyright 2003 royal meteorological society

examining deep and shallow adriatic bora events this note examines the differences observed between two adriatic bora events that took place in the winter of 2011 case 1 and 2012 case 2 using the weather research and forecasting wrf model aided by two terrasar x tsx images the former was a deep bora event predominantly of an anti cyclonic type whereas the latter was a shallow bora case simultaneously pertaining to cyclonic and frontal types the high resolution of the ts x scansar scenes offered for the first time the opportunity to examine the finer details of the bora jet and wake patterns in the case 1 bora the bright patterns of the two major jets dominated the ts x image with a well defined broad wake zone in between in the case 2 bora a much richer pattern was registered in the ts x normalised radar cross section nrcs field with a notable difference in the intensity of the response the major jets were broader each exhibiting features apparently reflecting the impact of smaller ridges in the dinaric mountain chain the impact was also observed in the narrower wake zone which was populated with three additional but shorter jets in both cases the ts x derived surface wind field convincingly conveyed the rich morphology of the jet and wake response the wrf model near surface wind simulations in a one way nested four domain setup closely resembled the ones obtained with the satellite sensor additionally the vertical along coast cross section of the lower troposphere indicated jets within the lowest 1 km corresponding to the ones registered in the ts x derived surface wind with the jets in case 2 exhibiting much higher velocities both the satellite observations and the model simulations indicated that these low level jets lljs can maintain their coherence and speed at considerable offshore distances which is in agreement with certain theoretical studies the longer offshore extent and higher velocities suggested by the wrf simulations have yet to be verified with field data

observations of a terrain forced mesoscale vortex and canyon drainage flows along the front range of colorado abstract observations taken during the february 1991 atmospheric studies in complex terrain ascot winter validation study are used to describe the wind field associated with a terrain forced mesoscale vortex and thermally forced canyon drainage flows along the front range of northeastern colorado a case study is presented of the night of 6 7 february 1991 when a weak vortex formed and propagated through the ascot domain the noaa erl environmental technology laboratory doppler lidar one of an ensemble of instruments participating in the ascot field experiment obtained high resolution measurements of the structure of both the vortex and the canyon drainage flows the lidar observations documented the kinematic and structural changes in the cyclone and their relationship to a drainage jet exiting a nearby canyon lidar analyses clearly show the layering and stratification present during this case specifically the drainage jet flowing under the cyclone a period of strong intensification of the drainag

the glacial history of the dinaric alps montenegro abstract large areas of montenegro were glaciated during the pleistocene this paper presents evidence from the massifs of central montenegro including durmitor and sinjajevina moracke planine maganik prekornica and vojnik glacial deposits have been subdivided on the basis of morphostratigraphy and soil weathering and 31 u series ages from cemented tills provided a geochronological framework the largest glaciation occurred before 350 ka when a series of conjoined ice caps over the massifs of central montenegro covered a total area of nearly 1500 km 2 these formed during mis 12 and correspond with the largest skamnellian stage glaciations in greece to the south later middle pleistocene glaciations occurred during the penultimate glacial cycle correlating with the vlasian stage in greece mis 6 when ice caps covered an area of 720 km 2 over central montenegro there is also geochronological evidence of glacial deposits dating from the interval between mis 12 and mis 6 before the interglacial complex of mis 7 this glaciation appears to have been very similar in extent to that which occurred during mis 6 the last glacial cycle in central montenegro was characterised by valley and cirque glaciers covering a total area of 49 km 2 it is very likely that glaciers have been present in the mountains of central montenegro during every glacial cycle since a small glacier still survives today the smaller glaciers of the last glacial cycle are likely to have been associated with summer temperatures that were warmer than those of earlier cold stages the striking contrast in the extent and thickness of ice cover during the cold stages of the pleistocene has an important bearing on the geomorphological and biological evolution of the balkans

topographic influences on recent changes of very small glaciers in the monashee mountains british columbia canada an analysis of the local topographic setting of very small 0 4 km 2 glaciers within a small region of the monashee mountains british columbia was conducted to investigate its influence on recent changes in the extent of these glaciers net changes in glacier extent were determined from a detailed manual comparison of remotely sensed imagery acquired in 1951 2001 and 2004 most of the 86 glaciers included in the study showed no observable net change in area over the study period while six glaciers retreated four disappeared entirely and only one advanced indices derived to characterize elements of the local topographic setting that might affect the local mass balance suggest that most of the glaciers are situated in locations that favor ice preservation by enhancing mass input and or reducing ablation rates glaciers situated in less favorable settings generally either decreased in area or disappeared the results suggest that most of the glaciers studied have retreated as far as they are likely to under the climatic conditions of the late 20th century

geomorphologic and paleoclimatic evidence of holocene glaciation on mount olympus greece this study investigates the possibility of holocene glaciation on mount olympus greece with a respective local temperature precipitation equilibrium line altitude tp ela at c 2200m a s l based on geomorphologic and paleoclimatic evidence at present the local tp ela is situated above the mountain s summit c 2918 m a s l but permanent snowfields and ice bodies survive within megala kazania cirque between c 2400 and c 2300 m a s l because of the cirque s maritime setting that results from its close proximity c 18km to the aegean sea and of the local topographical controls the snow and ice bodies occupied a considerably larger area and attained a stabilization phase between ad 1960 and 1980 also manifested from aerial photographs a period characterized by increased winter precipitation pw with subsequent tp ela depression to c 2410m a s l mid to late 20th century pw and tp ela variations exhibit negative correlations with the winter north atlantic oscillation index naow at annual and multidecadal 30 years timescales late holocene ad 1680 1860 reconstructed summer mean temperatures were lower by ts 1 1 c in relation to the reference period between ad 1960 and 1980 and were also superimposed to negative naow phases thus bracketing this time interval as a favorable one to glacial formation and or advance millennial scale annual precipitation reconstructions at the hypothesized tp ela c 2200m a s l point the period between 8 and 4 kyr bp as another glacier friendly candidate the mid holocene rather simplistic sequence of potential glacial advance phase was disturbed by short lived cold climatic deteriorations well documented over the northern aegean region that may partly explain the multicrested shape of the highest c 2200 m a s l morainic complex of megala kazania cirque

approaches to middle stone age landscape archaeology in tropical africa the southern montane forest grassland mosaic ecosystem in the humid subtropics southern rift valley of africa comprised the environmental context for a large area in which modern human evolution and dispersal occurred variable climatic conditions during the late pleistocene have ranged between humid and hyperarid changing the character of the ecosystem and transforming it at different points in time into a barrier a refuge and a corridor between southern and eastern african populations alluvial fans presently blanket the areas adjacent to major river systems which were key areas of prehistoric human habitation these sets of variables have created conditions that are both challenging and advantageous to conduct archaeological research lateritic soil development has resulted in poor organic preservation and facilitated insect bioturbation which has demanded an integrated micro macro scale approach to building a reliable geochronology an integrated field and analytical methodology has also been employed to identify the nature and degree of post depositional movement in alluvial deposits which preserve a wide range of spatial integrity levels in buried stone artifact assemblages between 47 and 30 ka in karonga northern malawi this paper describes the methodological advances taken toward understanding open air middle stone age archaeology in sub tropical africa and explores the inferential potential for understanding pleistocene human ecology in the important southern rift valley region

bora driven potential vorticity banners over the adriatic a case study is presented of the secondary potential vorticity pv banners over the northern adriatic that occurred in an early stage of a bora on 7 november 1999 during the mesoscale alpine programme map special observation period the dynamics and structure of the lee side and cross mountain flow past the dinaric alps were investigated using data collected in a dual aircraft ncar electra and noaa p 3 map intensive observing period 15 mission over the adriatic and high resolution numerical simulations the observational study employs flight level dropsonde and scanning aerosol backscatter lidar data the observed flow structure is compared with simulations results of the coamps model run at a horizontal resolution of 3 km the dinaric alps the north west south east oriented coastal mountain range of croatia has an irregular ridge line with a number of peaks in the range of 1 5 2 km with several prominent mountain passes the identified jet and wake structure within the east north easterly bora over the adriatic was found to be well correlated with the upwind distribution of mountain passes and peaks the wake flow structure was found also to be in excellent agreement with the climatological profile of the bora strength along the croatian coast the attendant secondary pv banners separating individual jets and wakes diagnosed by computing pv from the flight level data were found to have a characteristic horizontal scale of 10 25 km and a maximum amplitude of up to 6 pvu within the boundary layer over the open sea the thickness of the boundary layer within which the east north easterly bora also achieved its maximum strength was approximately 1 km detailed comparison with the numerical model results shows that at the horizontal resolution of 3 km the coamps model reproduces well the overall flow structure the coamps simulated pv field was found to be in good agreement with the pv derived from observations the differences in substructure between simulated and experimentally derived pv profiles derive from minor differences between modelled and observed velocity and potential temperature profiles which are subsequently accentuated by computing differentiated quantities such as vorticity and potential temperature gradients the high predictability and steadiness of the pv banners and a good correlation with the geometry of the upwind topography support the orographic generation mechanism of pv with dissipation in hydraulic jumps and gravity wave breaking regions as the likely main source of pv copyright 2004 royal meteorological society

the wake south of the alps dynamics and structure of the lee side flow and secondary potential vorticity banners the dynamics and structure of the lee side flow over the po valley during a northerly fohn event which occurred in the framework of the mesoscale alpine programme special observation period on 8 november 1999 during intensive observation period 15 has been investigated using aircraft data and high resolution numerical simulations numerical simulations were performed with the mesoscale non hydrostatic model meso nh using three nested domains with horizontal resolutions 32 8 and 2 km the 2 km resolution domain being centred on the po valley the basic data model comparison and back trajectory and tracer release analyses provided evidence that the jet wake structure of the flow above the po valley could be reasonably identified with the mountain pass peak distributions measurements from three aircraft flying below the alps crestline at 2700 1500 and 600 m above sea level along two 350 km east west legs designed to be approximately perpendicular to the northerly synoptic flow were used to compute the potential vorticity pv experimentally assuming the lee side flow to be two dimensional the simplified form of the pv under these assumptions is hereafter referred to as spv due to increasing lee side flow curvature with decreasing altitude caused by flow splitting at the scale of the alps the experimentally derived spv was compared to its simulated counterpart in situ measurements showed that coherent secondary pv banners pvb2s do exist downstream of the complex alpine terrain as observations show oscillations between positive and negative values of spv as expected from the simulations the details of the structure of the spv field simulated with meso nh were found to be different from the observations i e the location of observed maxima and minima of spv did not match their simulated counterparts at particular points this is because the correspondence between observed and modelled velocity and potential temperature fields was not good enough to expect good correspondence between differentiated quantities such as vorticity and potential temperature gradient since less reliable shorter scale features are thereby accentuated parametrized processes such as surface drag and internal diffusion and numerical processes such as model filters to which pv production mechanisms are sensitive and whose role is difficult to assess also contribute to the poor agreement between observed and modelled spv fluctuations finally simulations suggest that lowlevel gravity wave breaking was the main mechanism responsible for the formation of the elongated pvb2 modelled observed over the po valley

potential vorticity of flow along the alps abstract observations from the german front experiment are presented here that show the existence in conditions with a dominant flow component parallel to the main alpine chain of a mesoscale region to the north of the alps where the absolute and potential vorticity pv are substantially negative these structures exist before the front arrives to the alps and appear to be affected little by the passage of the front a dynamical explanation for these and other mesoscale structures is sought by considering a simple unsheared airflow impinging on the alps from the west a linear frictionless model for the steady state response is used as well as a full nonlinear numerical model with and without friction a vastly simplified alpine orography is considered as well as one that adequately describes its mesoscale detail the results show that the frictionless linear dynamics lead to a zone north of the alps with anticyclonic vorticity but with uniform positive potential vorticity with boundary layer processe