birth growth and morphologic evolution of the laghetto cinder cone during the 2001 etna eruption we have undertaken detailed observations of the formation of the laghetto cinder cone a new cone that formed during a 2 week period of intense activity in piano del lago on the upper slopes of mount etna in summer 2001 we describe the events leading to the formation of a small graben the formation of pit craters on the base of the graben the onset of phreatomagmatic activity a transition to intense strombolian activity and a return to phreatomagmatic activity as the eruption came to an end we discuss the reasons for these transitions and describe the morphological development of the cone during these events arcuate cracks on the southern part of the cone were related to withdrawal of magma at the end of the eruption other slope instabilities that developed during the eruption include the formation of small radial grain flows on the outer flanks of the cone and the collapse into the crater of part of the crater rim some of the failure planes we observed were first identified using a flir tm 695 thermal infrared camera this is the first time that infrared thermography has been used to detect instability of volcanic structures results obtained during this test case demonstrate that thermal cameras are a very useful tool for studies of volcanic instability

the diurnal cycle of surface divergence over the global oceans the diurnal cycle of surface divergence over the oceans is examined using 4 daily data from the tandem seawinds satellite missions during april september 2003 a statistically significant diurnal cycle of surface divergence is observed over a large fraction of the tropical and subtropical oceans the highest amplitudes are found adjacent to tropical landmasses and decrease exponentially with distance away from the coast with a representative e folding distance of approximately 200 km in most of these near coastal regions the surface divergence peaks at 15 20 h locally and there is evidence of offshore propagation of the signal there are regions however where strong cycles persist for much greater distances offshore over the southeast pacific ocean there is evidence of a diurnal subsidence wave that propagates for over 2000 km away from the south american coast at approximately 25 m s 1 a cloud response to the subsidence wave moving westward from the andes mountains is detected using passive microwave observations of liquid water path over the remote tropical pacific significant diurnal amplitude is found in and around regions of strong mean surface convergence with a phase suggesting a surface response to the early morning diurnal maximum in precipitation and propagation away from these sources consistent with gravity waves forced by deep tropospheric heating european centre for medium range weather forecasts ecmwf model simulations of 850 hpa subsidence show a diurnal cycle that is largely consistent with the seawinds divergence observations copyright c 2009 royal meteorological society

a simple analytical model of the nocturnal low level jet over the great plains of the united states abstracta simple analytical model including both diurnal thermal forcing over sloping terrain the holton mechanism and diurnally varying boundary layer friction the blackadar mechanism is developed to account for the observed amplitude and phase of the low level jet llj over the great plains and to understand better the role of each mechanism the present model indicates that for the pure holton mechanism time independent friction coefficient the maximum southerly wind speed occurs depending on the assumed friction coefficient between sunset and midnight local standard time which is earlier than the observed after midnight maximum for the pure blackadar mechanism time independent thermal forcing the present model shows that generally occurs later closer to sunrise than observed and has a strong latitudinal dependence for both mechanisms combined the present model indicates that occurs near to the observed time which lies between the time obtained in the pure holton mechanism and

a linear theory of three dimensional land sea breezes abstractland sea breezes lsbs induced by diurnal differential heating are examined using a three dimensional linear model employing fast fourier transform with emphasis on the complex coastline shape and geometry the earth s rotation and background wind effects it has been demonstrated that the low level vertical motion associated with lsb can be significantly enhanced over a bay peninsula because of convergence of perturbations induced by differential heating along a seaward concave convex coastline the dependence of surface winds and vertical motion patterns and their evolutions on the coastline geometries such as the width and the aspect ratio of the bay the earth s rotation and the background winds are investigated the lsb induced by an isolated tropical island is characterized by onshore flow and ascent over the island in the afternoon to early evening with a reversal of direction from midnight to early morning the diurnal heating induced vertical motion is greatly enhanced over the isl

ground penetrating radar and its use in sedimentology principles problems and progress abstract ground penetrating radar gpr also referred to as ground probing radar surface penetrating radar subsurface radar georadar or impulse radar is a noninvasive geophysical technique that detects electrical discontinuities in the shallow subsurface

holocene development of the river lippe valley germany a case study of anthropogenic influence the characteristics of the holocene valley floor of the river lippe germany are atypical for a river in central europe the valley floor consists of three terrace levels which are not always clearly separated from each other analysis of the sediments making up the terraces indicates that they accumulated during the course of the entire holocene although there is insufficient information available to allow detailed determination of phases of fluvial change and stability responsible for terrace formation two of the terraces exist only in the lower reaches of the valley where they converge and diverge with the third the lowest terrace consists only of a narrow strip running parallel to the river channel the configuration of the valley floor may be explained by a series of anthropogenic influences the earliest human impact probably occurred about 2000 years ago when during their campaign against german tribes the romans built a towpath and may have changed the channel planform from its natural anabranching pattern to a meandering form by building small dams on local distributary forks implementation of artificial meander cut offs to improve navigation on the river began in medieval times the morphological response to these human interventions was primarily degradational in the 19th century artificial lateral fill was used to narrow the channel and the towpath was renewed several times the trace of the most recent towpath is still discernible as a narrow strip parallel to the river channel and it constitutes the lowest terrace level comparison between the bankfull discharge of a 4000 year old abandoned channel and the formative flow for the modern channel supports the premise that prior to anthropomorphic influence the natural planform was anabranched copyright 2000 john wiley sons ltd

evaluating competing hypotheses for the origin and dynamics of river anastomosis anastomosing rivers have multiple interconnected channels that enclose flood basins various theories potentially explain this pattern including an increased discharge conveyance and sediment transport capacity of multiple channels deltaic branching avulsion forced by base level rise or a tendency to avulse due to upstream sediment overloading the former two imply a stable anabranching channel pattern whereas the latter two imply disequilibrium and evolution towards a single channel pattern in the absence of avulsion our objective is to test these hypotheses on morphodynamic scenario modelling and data of a well documented case study the upper columbia river proportions of channel and floodplain sediments along the river valley were derived from surface mapping initial and boundary conditions for the modelling were derived from field data a 1d network model was built based on gradually varied flow equations sediment transport prediction mass conservation transverse slope and spiral meander flow effects at the bifurcations the number of channels and crevasse splays decreases in a downstream direction also measured sediment transport is higher at the upstream boundary than downstream these observations concur with bed sediment overloading from upstream which can have caused channel aggradation above the surrounding floodplain and subsequent avulsion the modelling also indicates that avulsion was likely caused by upstream overloading in the model multi channel systems inevitably evolve towards single channel systems within centuries the reasons are that symmetric channel bifurcations are inherently unstable while confluenced channels have relatively less friction than two parallel channels so that more discharge is conveyed through the path with more confluences and less friction furthermore the present longitudinal profile curvature of the valley could only be reproduced in the model by temporary overfeeding

remote determination of sif4 in volcanic plumes a new tool for volcano monitoring sif4 is probably a common trace component of fumarole gases on volcanoes arising from interactions between magmatic hf and wall rocks it is not distinguished from hf in conventional analyses a strong absorption band at 1032 cm 1 makes sif4 well suited to remote open path ftir spectroscopic techniques we report the first measurements of sif4 in volcanic gases at etna and vulcano sicily sif4 concentrations were low at etna but higher at vulcano where the so2 sif4 ratio was consistently around 1 7 10 2 1 thermodynamic considerations show that the hf sif4 ratio increases sharply with increasing temperature thus remote measurements of sif4 may offer a qualitative way of constraining fumarole temperatures we use our ftir measurements of hcl sif4 in combination with conventional measurements of hcl hf to infer an hf sif4 ratio for vulcano of 10 1 consistent with gas temperatures in the range 200 450 c

spectroscopic evidence for a lava fountain driven by previously accumulated magmatic gas the eruption of mount etna in 2000 was notable for an exceptional series of 64 periodic lava fountains propelling lava fragments to heights of up to 900 metres it has been difficult to determine which of two suggested sources of power gas release from the magma itself during its rapid ascent or a build up of pressure from gas accumulated at depth is the driving force for these dramatic jets but one of the etna fountains provided volcanologists with the opportunity to use remote sensing not that remote see picture on the following page to determine the infrared spectra of the gas phase this revealed the chemical composition of the gas that powered this fountain as consistent with an origin in an accumulated gas layer lava fountains are spectacular continuous gas jets propelling lava fragments to heights of several hundred metres which occasionally occur during eruptions of low viscosity magmas1 2 3 4 5 whether they are generated by the effervescent disruption of fast rising bubbly melt2 3 4 5 or by the separate ascent of a bubble foam layer accumulated at depth6 7 still remains a matter of debate8 no field measurement has yet allowed firm discrimination between these two models a key insight into the origin of lava fountains may be gained by measuring the chemical composition of the driving gas phase this composition should differ markedly depending on whether the magma degassing occurs before or during eruption9 10 here we report the analysis of magmatic gas during a powerful 250 600 m high lava fountain measured with fourier transform infrared spectroscopy11 12 13 14 on mount etna sicily the abundances of volcanic gas species determined from absorption spectra of lava radiation reveal a fountain gas having higher co2 s and s cl ratios than other etnean emissions14 15 16 17 18 and which cannot derive from syn eruptive bulk degassing of etna basalt19 20 instead its composition suggests violent emptying of a gas bubble layer previously accumulated at about 1 5 km depth below the erupting crater

the internal structure of scrolled floodplain deposits based on ground penetrating radar north thompson river british columbia abstract a study of floodplain deposits using ground penetrating radar gpr was conducted on a confined meander of the north thompson river near kamloops british columbia a survey grid consisting of 20 individual gpr profiles from 200 m to 900 m in length was constructed on a 0 9 km2 section of the floodplain all gpr profiles were collected using a pulse ekkotm iv gpr system with 100 or 200 mhz antennae dependent on the thickness of floodplain sediments floodplain sediments consist of sand and gravel deposits approximately 7 to 14 m thick that overlie silts and clays interpreted to be glaciolacustrine in origin vibracore and auger data obtained at nine locations in the gpr survey grid show that changes from medium sand to gravel do not produce distinct radar reflections in gpr profiles but that the water table may locally produce a distinct high amplitude radar reflection area well log data show that rapid signal attenuation at depth in all gpr profiles coincides with underlying silt and clay sediments gpr profiles were therefore useful in mapping 3 d variability in the thickness of floodplain deposits all gpr profiles were divided into macroscale 150 m2 in 2 d cross section radar facies delineated on the basis of the nature and orientation of reflections relative to surface scroll topography radar stratigraphy suggests that the floodplain is composed of a single complex lateral accretion deposit with periodic channel fills located between surface scroll ridges dip direction profiles normal to surface scroll ridges exhibit mainly inclined stratification is and or preserved ridge and swale ras deposits dipping in the direction of floodplain accretion well developed ras architecture in 200 mhz gpr profiles displays mainly wavy reflections conforming with surface topography and little inclined stratification these reflectors are interpreted to be the result of processes of vertical accretion associated with floodplain formation preserved scroll ridge deposits exhibit asymmetry at depth dipping more steeply in the direction of floodplain accretion profiles of strike direction parallel to surface scroll ridges show either parallel or slightly inclined 1 2 reflections dipping in the downstream direction

application of field geophysics in geomorphology advances and limitations exemplified by case studies abstract during the last decade the use of geophysical techniques has become popular in many geomorphological studies however the correct handling of geophysical instruments and the subsequent processing of the data they yield are difficult tasks furthermore the description and interpretation of geomorphological settings to which they apply can significantly influence the data gathering and subsequent modelling procedure e g achieving a maximum depth of 30 m requires a certain profile length and geophone spacing or a particular frequency of antenna for more than three decades geophysical techniques have been successfully applied for example in permafrost studies however in many cases complex or more heterogeneous subsurface structures could not be adequately interpreted due to limited computer facilities and time consuming calculations as a result of recent technical improvements geophysical techniques have been applied to a wider spectrum of geomorphological and geological settings this paper aims to present some examples of geomorphological studies that demonstrate the powerful integration of geophysical techniques and highlight some of the limitations of these techniques a focus has been given to the three most frequently used techniques in geomorphology to date namely ground penetrating radar seismic refraction and dc resistivity promising applications are reported for a broad range of landforms and environments such as talus slopes block fields landslides complex valley fill deposits karst and loess covered landforms a qualitative assessment highlights suitable landforms and environments the techniques can help to answer yet unsolved questions in geomorphological research regarding for example sediment thickness and internal structures however based on case studies it can be shown that the use of a single geophysical technique or a single interpretation tool is not recommended for many geomorphological surface and subsurface conditions as this may lead to significant errors in interpretation because of changing physical properties of the subsurface material e g sediment water content in many cases only a combination of two or sometimes even three geophysical methods gives sufficient insight to avoid serious misinterpretation a good practice guide has been framed that provides recommendations to enable the successful application of three important geophysical methods in geomorphology and to help users avoid making serious mistakes

anabranching rivers their cause character and classification anabranching rivers consist of multiple channels separated by vegetated semi permanent alluvial islands excised from existing floodplain or formed by within channel or deltaic accretion these rivers occupy a wide range of environments from low to high energy however their existence has never been adequately explained they occur concurrently with other types of channel pattern although specific requirements include a flood dominated flow regime and banks that are resistant to erosion with some systems characterized by mechanisms to block or constrict channels thereby triggering avulsion the fundamental advantage of an anabranching river is that by constructing a semi permanent system of multiple channels it can concentrate stream flow and maximize bed sediment transport work per unit area of the bed under conditions where there is little or no opportunity to increase gradient on the basis of stream energy sediment size and morphological characteristics six types of anabranching river are recognized types 1 3 are lower energy and types 4 6 are higher energy systems type 1 are cohesive sediment rivers commonly termed anastomosing with low w d ratio channels that exhibit little or no lateral migration they are divisible into three subtypes based on vegetative and sedimentary environment type 2 are sand dominated island forming rivers and type 3 are mixed load laterally active meandering rivers type 4 are sand dominated ridge forming rivers characterized by long parallel channel dividing ridges type 5 are gravel dominated laterally active systems that interface between meandering and braiding in mountainous regions type 6 are gravel dominated stable systems that occur as non migrating channels in small relatively steep basins anabranching rivers represent a relatively uncommon but widespread and distinctive group that because of particular sedimentary energy gradient and other hydraulic conditions operate most effectively as a system of multiple channels separated by vegetated floodplain islands or alluvial ridges

scales and causes of heterogeneity in bars in a large multi channel river rio parana argentina to date published studies of alluvial bar architecture in large rivers have been restricted mostly to case studies of individual bars and single locations relatively little is known on how the depositional processes and sedimentary architecture of km scale bars vary within a multi km reach or over several 100s km downstream this study presents ground penetrating radar gpr and core data from 11 km scale bars from the rio parana argentina the investigated bars are located between 30 km upstream and 540 km downstream of the rio parana rio paraguay confluence where a significant volume of fine grained suspended sediment is introduced into the network bar scale cross stratified sets with lengths and widths up to 600 m and thicknesses up to 12 m enable the distinction of large river deposits from stacked deposits of smaller rivers but are only present in half the surface area of the bars up to 90 of bar scale sets are found on top of finer grained ripple laminated bar trough deposits bar scale sets make up as much as 58 of the volume of the deposits in small incipient mid channel bars but this proportion decreases significantly with increasing age and size of the bars contrary to what might be expected a significant proportion of the sedimentary structures found in the rio parana is similar in scale to those found in much smaller rivers in other words large river deposits are not always characterised by big structures that allow a simple interpretation of river scale however the large scale of the depositional units in big rivers causes small scale structures such as ripple sets to be grouped in thicker co sets which indicate river scale even when no obvious large scale sets are present the results also show that the composition of bars differs between the studied reaches upstream and downstream of the confluence with the rio paraguay relative to other controls on downstream fining the tributary input of fine grained suspended material from the rio paraguay causes a marked change in the composition of the bar deposits compared to the upstream reaches the sedimentary architecture of the downstream reaches in the top 5 m of mid channel bars shows i an increase in the abundance and thickness up to m scale of laterally extensive 100s of metres fine grained layers ii an increase in the percentage of deposits comprised of ripple sets to 40 in the upper bar deposits and iii an increase in bar trough deposits and a corresponding decrease in bar scale cross strata

the role of floodplain width and alluvial bar growth as a precursor for the formation of anabranching rivers abstract anabranching rivers are defined as a system of multiple channels separated by stable alluvial islands while substantial progress has been made in developing a physics based understanding of what drives the differences between meandering and braided river channels anabranching rivers have not been well integrated into these models here we propose that alluvial bar growth on the floodplain may be a precursor for the formation of anabranching rivers alluvial bar growth strongly depends on the aspect ratio of the flow width divided by depth and rivers with wide floodplains have flows with a large aspect ratio consistent with this idea remotely sensed measurements of floodplain width of four rivers from different climatic and tectonic settings show that anabranching river patterns are often associated with relatively wide floodplains to explore the physics behind that empirical relationship we carried out two sets of morphodynamic numerical simulations using boundary conditions from field scale modern anabranching rivers spanning different climatic and geologic settings as well as hypothetical floodplain widths results from the simulations show that for a given flood discharge widening the floodplain changes the river pattern from single channel to multi threaded with mobile bars to multi channeled with immobile islands multi channeled patterns arise because the emergence of bars causes flow bifurcation subsequent bifurcation instability leads to the emergence of multiple stable channels as the channels increase their cross sectional area shields stresses on intervening bars are reduced until the bars stabilize into islands we suggest that the presence of stable islands allows vegetation to grow or cohesive sediment to accumulate leading to enhanced channel bank strength and a stable anabranching pattern our results suggest that alluvial bar growth can be a precursor to formation of anabranching rivers compared with field measurements our simulations accurately predict the number of active channels to within 20 which seems to support the idea that some anabranching rivers may originate from alluvial bar growth

first gas and thermal measurements at the frequently erupting gamalama volcano indonesia reveal a hydrothermally dominated magmatic system abstract the first gas and thermal measurements at the summit of the gamalama volcano indicate that the system is dominated by hydrothermal processes this is highlighted by the prevalence of h2s over so2 h2s so2 2 8 a high co2 so2 ratio 76 201 and a low heat transfer 3 0 mw to the surface a relative variation in gas composition is observed along the degassing fracture zone possibly due to partial s scrubbing despite this surface hydrothermal signature the system exhibits high gas equilibrium temperatures 425 480 c indicating that fluids are not exclusively derived from a boiling hydrothermal aquifer but also sourced by cooling and crystallizing basaltic magma at deep that continues to inject magmatic fluids into the system this hydrothermally dominated activity on gamalama possibly persisted over the last two decades during which a high number of eruptive events were witnessed the period coincides with the opening of large fractures at the summit that subsequently shifted the volcanic activity from the crater center to the peripheral fractures zones these fractures that possibly developed in response to the regional geodynamics have weakened the hydrothermal seal allowing the pressure developed by the hydrothermal magmatic system and promoted by the high annual rainfall to rapidly exceeds the tensile strength of the seal leading to the numerous phreatic eruptions

morphology hydrology and evolution of the anastomosing ovens and king rivers victoria australia anastomosing channels form the characteristic stream pattern of the riverine plain of southeastern australia investigations of the ovens and king rivers in northeastern victoria show that the individual channels and reaches of channels vary markedly in channel morphology and age young channels have large bankfull flows low sinuosity large meander wavelength steep gradients and are unstable they are incised channels that are rapidly eroding their bed and banks old channels however have small bankfull flows high sinuosity small meander wavelength gentler gradients and are relatively stable the multiple channels develop by avulsion as individual channels become older and more sinuous they also become more hydraulically inefficient thus increasing proportions of flood discharge are displaced overbank this overbank flow concentrates in relatively straight flood plain depressions and it erodes a new channel which develops by both up and down valley incision down valley incision is initiated at outflow points and up valley incision is initiated where the overbank flow rejoins the main channel with time both channel segments join to form a new anabranch of the anastomosing channel system large anastomosing channel networks have been identified in ancient rocks by stratigraphers and sedimentologists on the basis of studies of the anastomosing ovens and king rivers it is very likely that these channel networks are composed of channels of different ages hence even at one stratigraphic level not all of the anabranches functioned simultaneously nevertheless as a result of anabranch incision which intersects older channels at depth a three dimensional network of paleochannels can form that permits fluid flow throughout the network

correction to chronological evolution of the channel functional units in association with palaeo hydrogeomorphological environment in the ancient delta fan of subarnarekha basin india the original article has been published inadvertently with some errors in figures and their caption figs 1 2 3 and errors only in captions of figures figs 4 5 7 8 9 also errors in tables and their caption tables 1 5 6 7 and errors only in captions of tables tables 2 3

timing of massive fleuve manche discharges over the last 350 kyr insights into the european ice sheet oscillations and the european drainage network from mis 10 to 2 continuous high resolution mass accumulation rates mar and x ray fluorescence xrf measurements from marine sediment records in the bay of biscay ne atlantic have allowed the determination of the timing and the amplitude of the fleuve manche channel river discharges during glacial stages mis 10 mis 8 mis 6 and mis 4 2 these results have yielded detailed insight into the middle and late pleistocene glaciations in europe and the drainage network of the western and central european rivers over the last 350 kyr this study provides clear evidence that the fleuve manche connected the southern north sea basin with the bay of biscay during each glacial period and reveals that fleuve manche activity during the glaciations mis 10 and mis 8 was significantly less than during mis 6 and mis 2 we correlate the significant fleuve manche activity detected during mis 6 and mis 2 with the extensive saalian drenthe substage and the weichselian glaciations respectively confirming that the major elsterian glaciation precedes the glacial mis 10 in detail massive fleuve manche discharges occurred at ca 155 ka mid mis 6 and during termination i while no significant discharges are found during termination ii it is assumed that a substantial retreat of the european ice sheet at ca 155 kyr followed by the formation of ice free conditions between the british isles and scandinavia until termination ii allowed meltwater to flow northwards through the north sea basin during the second part of the mis 6 we assume that this glacial pattern corresponds to the warthe substage glacial maximum therefore indicating that the data presented here equates to the drenthe and the warthe glacial advances at ca 175 160 ka and ca 150 140 ka respectively finally the correlation of our records with odp site 980 reveals that massive fleuve manche discharges related to partial or complete melting of the european ice masses were synchronous with strong decreases in both the rate of deep water formation and the strength of the atlantic thermohaline circulation fleuve manche discharges over the last 350 kyr probably participated with other meltwater sources in the collapse of the thermohaline circulation by freshening the northern atlantic surface water

a quantitative three dimensional depositional model of gravelly braided rivers a quantitative three dimensional depositional model of gravelly braided rivers has been developed based largely on the deposits of the sagavanirktok river in northern alaska these deposits were described using cores wireline logs trenches and ground penetrating radar profiles the origin of the deposits was inferred from observations of 1 channel and bar formation and migration and channel filling interpreted from aerial photographs 2 water flow during floods and 3 the topography and texture of the river bed at low flow stage this depositional model quantitatively represents the geometry of the different scales of strataset the spatial relationships among them and their sediment texture distribution porosity and permeability in the model are related to sediment texture the geometry of a particular type and scale of strataset is related to the geometry and migration of the bedform type e g ripples dunes bedload sheets bars associated with deposition of the strataset in particular the length to thickness ratio of stratasets is similar to the wavelength to height ratio of associated bedforms furthermore the wavelength and height of bedforms such as dunes and bars are related to channel depth and width therefore the thickness of a particular scale of strataset i e medium scale cross sets and large scale sets of inclined strata will vary with river dimensions these relationships between the dimensions of stratasets bedforms and channels mean that this depositional model can be applied to other gravelly fluvial deposits the depositional model can be used to interpret the origin of ancient gravelly fluvial deposits and to aid in the characterization of gravelly fluvial aquifers and hydrocarbon reservoirs

architecture of channel belt deposits in an aggrading shallow sandbed braided river the lower niobrara river northeast nebraska abstract architecture of recent channel belt deposits of the niobrara river northeast nebraska usa records the response of a sandy braided river to rapid base level rise up to 3 m of aggradation has occurred within the lower 14 km of the niobrara river since the mid 1950s as a result of base level rise at the confluence of the niobrara and missouri rivers aerial photographs and channel surveys indicate that the lower niobrara has evolved from a relatively deep stable channel with large bank attached braid bars to a relatively shallow aggrading channel with braid bars and smaller secondary channels architecture of channel belt deposits associated with the recent aggradation has been defined using ground penetrating radar gpr and vibracores the channel belt deposits exhibit a series of amalgamated channel fills and braid bar complexes i e macroforms radar facies identified in the gpr data represent architectural elements of the braid bar complexes large and small bedforms two dimensional 2 d and three dimensional 3 d dunes and channels individual braid bars appear to consist of basal high flow and upper low flow components preservation of the complete high flow bar geometry is generally incomplete due to frequent migration of smaller scale secondary channels within the channel belt i e braided channel network at low discharges the large scale stratification of the braid bar deposits is dominated by cross channel and upstream accretion elements of downstream accretion are also recognized these accretion geometries have not been documented previously in similar sandy braided rivers braid bar deposits with low flow modification e g incision by secondary channels are recognized in the deeper portions of the deposits imaged by gpr preservation of braid bars with both high and low flow components is a result of the rapid base level rise and channel bed aggradation experienced by the niobrara river over the past 45 years recent avulsion of the river channel allowed preservation of the upper low flow component of the braid bar deposits i e bar top sequences the relative abundance and stratigraphic position of the amalgamated channels and braid bar complexes within the channel belt deposits constitute a signature of the recent base level rise

controls on the occurrence and prevalence of floodplain channels in meandering rivers the process of channelization on river floodplains plays an essential role in regulating river sinuosity and creating river avulsions most channelization occurs within the channel belt e g chute channels but growing evidence suggests some channels originate outside of the channel belt in the floodplain to understand the occurrence and prevalence of these floodplain channels we mapped 3064 km2 of floodplain in indiana usa using 1 5 m resolution digital elevation models dems derived from airborne light detection and ranging lidar data we find the following range of channelization types on floodplains in indiana 6 8 of floodplain area has no evidence of channelization 55 9 of floodplains show evidence e g oxbow lakes of chute channel activity in the channel belt and 37 3 of floodplains contain floodplain channels that form long coherent down valley pathways with bifurcations and confluences and they are active only during overbank discharge whereas the first two types of floodplains are relatively well studied only a few studies have recognized the existence of floodplain channels to understand why floodplain channels occur we compared the presence of channelization types with measured floodplain width floodplain slope river width river meander rate sinuosity flooding frequency soil composition and land cover results show floodplain channels occur when the fluvial systems are characterized by large floodplain to river widths relatively higher meandering rates and are dominantly used for agriculture more detailed reach scale mapping reveals that up to 75 of channel reaches within floodplain channels are likely paleo meander cutoffs the meander cutoffs are connected by secondary channels to form floodplain channels we suggest that secondary channels within floodplains form by differential erosion across the floodplain linking together pre existing topographic lows such as meander cutoffs copyright 2016 john wiley sons ltd

analysis of wrf simulated diurnal boundary layer winds in eastern china using a simple 1d model abstractthe low level diurnal winds for different locations of eastern china are documented using the june 2006 11 hourly model data simulated with the weather research and forecasting wrf mesoscale model with a 9 km horizontal resolution a simple 1d model including both diurnal thermal forcing and diurnally varying boundary layer friction is found to explain important features of the wrf simulated diurnal boundary layer winds in eastern china for example in northeastern china at a similar latitude the maximum velocity parallel to the coastline at a longitude over the ocean occurs earlier than the maximum velocity parallel to the inland chain of coastline parallel mountains at a longitude over land this difference can be identified with the well known blackadar effect over the land off the eastern coast of china the diurnal winds for different latitudes over the ocean vary in both phase and amplitude consistent with expectations based on the simple 1d model

cooling rate of an active hawaiian lava flow from nighttime spectroradiometer measurements a narrow band spectroradiometer has been used to make nighttime measurements of the phase 50 eruption of pu u o o on the east rift zone of kilauea volcano hawaii on february 19 1992 a ger spectroradiometer was used to determine the cooling rate of an active lava flow this instrument collects 12 bit data between 0 35 to 3 0 m at a spectral resolution of 1 5 nm thirteen spectra of a single area on a pahoehoe flow field were collected over a 59 minute period 21 27 22 26 hst from which the cooling of the lava surface has been investigated a two component thermal mixing model flynn 1992 applied to data for the flow immediately on emplacement gave a best fit crustal temperature of 768 c a hot component at 1150 c and a hot radiating area of 3 6 of the total area over a 52 minute period within the time interval between flow resurfacings the lava flow crust cooled by 358 c to 410 c at a rate that was as high as 15 c min 1 our observations have significance both for satellite observations of active volcanoes and for numerical models of the cooling of lava flows during their emplacement

crevasse splays from the rapidly aggrading sand bed braided niobrara river nebraska effect of base level rise base level rise of 2 35 m on the niobrara river has resulted in aggradation of the channel belt and a recent avulsion overbank areas have become flooded by rising groundwaters and more than eight crevasse splays have formed between 1993 and 1997 two crevasse splays situated on the west and east sides of the niobrara have been studied using ground penetrating radar gpr shallow boreholes and topographic surveys the vibracores and gpr profiles provide a nearly three dimensional view of the architecture of crevasse splay deposits the east splay was initiated in the winter of 1993 94 and has expanded to cover an area 200 m by 1000 m with sediment up to 2 5 m thick the west splay which was initiated by the opening of a crevasse channel through a levee in the autumn of 1995 covers an area 150 m by 250 m with up to 1 2 m of sand deposited in a single year the niobrara splays are sand dominated and characterized by bedload deposition within channels 5 30 m wide and 0 5 2 m deep with the development of slipfaces where splays prograde into standing bodies of water sedimentary structures in cores include horizontal lamination ripple lamination and sets of cross stratification there is a slight tendency for splays to coarsen up but individual beds within the splays often fine up the abundance of crevasse splays on the niobrara river contrasts with other braided river floodplains in the niobrara crevasse splay formation followed aggradation within the channel belt which occurred in response to base level rise the link between crevasse splays channel aggradation and base level rise has important implications for the interpretation of ancient braided river and floodplain sequences it is suggested that crevasse splay deposits should be an important component of aggrading fluvial sediments and hence should be preserved within the rock record in this case the aggradation and crevassing have been tied to a rise in base level elevation and it is suggested that similar deposits should be preserved where braided rivers are affected by base level rise for instance during transgression and filling of palaeovalleys

dynamics of the december 2002 flank failure and tsunami at stromboli volcano inferred by volcanological and geophysical observations 1 the 2002 effusive flank eruption at stromboli volcano started on december 28 after several months of strong explosive activity at the summit craters on december 30 the seismic network recorded two large flank failures and associated tsunami waves this is the first time that a flank collapse and tsunami and their associated phenomena have been recorded by a multi disciplinary monitoring system volcanological and geophysical monitoring as well as thermal surveys performed immediately before and after the failure allowed us to define and interpret the sequence of events the still on going eruption has provided for the first time the opportunity to look into the dynamics of stromboli s effusive eruptions flank failure and landslide formation and their potential hazard

upstream control of river anastomosis by sediment overloading upper columbia river british columbia canada anastomosing rivers systems of multiple interconnected channels that enclose floodbasins constitute a major category of rivers for which various sedimentary facies models have been developed while the sedimentary products of anastomosing rivers are relatively well known their genesis is still debated a rapidly growing number of ancient alluvial successions being interpreted as of anastomosing river origin including important hydrocarbon reservoirs urge the development of robust models for the genesis of anastomosis to facilitate better interpretation of ancient depositional settings and controls the upper columbia river british columbia canada is the most studied anastomosing river and has played a key role in the development of an anastomosing river facies model two hypotheses for the origin of upper columbia river anastomosis include the following i downstream control by aggrading cross valley alluvial fans and ii upstream control by excessive bedload input from tributaries both upstream and downstream control may force aggradation and avulsions in the upper columbia river in order to test both hypotheses long term millennia scale floodplain sedimentation rates and avulsion frequencies are calculated using 14c dated deeply buried organic floodplain material from cross valley borehole transects the results indicate a downstream decrease in floodplain sedimentation rate and avulsion frequency along the anastomosed reach which is consistent with dominant upstream control by sediment overloading the data here link recent avulsion activity to increased sediment supply during the little ice age ca 1100 to 1950 ad this link is supported by data showing that sediment supply to the upper columbia study reach fluctuated in response to holocene glacial advances and retreats in the hinterland upstream control of anastomosis has considerable implications for the reconstruction of the setting of interpreted ancient anastomosing systems the present research underscores that anastomosing systems typically occur in relatively proximal settings with abundant sediment supplied to low gradient floodplains a situation commonly found in intermontane and foreland basins

why some alluvial rivers develop an anabranching pattern anabranching rivers have been identified globally but a widely accepted and convincing theoretical explanation for their occurrence has remained elusive using basic flow and sediment transport relations this study analyzes the mechanisms whereby self adjusting alluvial channels can anabranch to alter their flow efficiency sediment transport capacity per unit of stream power it shows that without adjusting channel slope an increase in the number of channels can produce a proportional decrease in flow efficiency a finding particularly relevant to understanding energy consumption in some braided rivers however anabranching efficiency can be significantly increased by a reduction in channel width as occurs when vegetated alluvial islands or between channel ridges form the counteracting effects of width reduction and an increasing number of channels can cause with no adjustment to slope an otherwise unstable system underloaded or overloaded to achieve stability as with other river patterns anabranching can be characterized by stable equilibrium or accreting disequilibrium examples copyright 2007 by the american geophysical union

linear theory of the sea breeze in a thermal wind this article investigates the linear dynamics of the sea breeze in an along shore thermal wind shear the present analysis shows that the sea breeze circulation is tilted towards the slanted isentropes associated with the thermal wind at a critical value of the thermal wind shear the tilt of the sea breeze circulation becomes equal to the slope of the background isentropes the present analysis also shows a spatial shift between the heating pattern and the sea breeze circulation the present linear theory is then applied to interpret measurements made in the vicinity of new york city where there is a warm season synoptic southwesterly jet it is compared with observations and past numerical simulations agreement is found with respect to the enhanced along coast wind that follows the tilted isentropes the order of magnitude of the isentrope tilt and the clockwise rotating wind hodograph showing the jet maximum peaking at 1800 solar time there is a disagreement between theory and observations on the phase lag between the jet maximum and the cross shore pressure gradient maximum however this disagreement can reasonably be attributed to either the angle made by the synoptic jet to the coastline and or the presence of friction the inland spatial shift of the breeze indicated by the theory might also be indirectly confirmed by the coastal inlan dw ind observations of al arger diurnal amplitude for a stronger synoptic jet copyright c 2011 royal meteorological society

ftir remote sensing of fractional magma degassing at mount etna sicily abstract the chemical composition of volcanic gas emissions from each of the four summit craters of mount etna was measured remotely in may 2001 using a fourier transform infrared ftir spectrometer operated on the upper flanks of the volcano the results reveal constant hci hf ratio but distinct so2 hc1 and so2 hf ratios in the emitted gases which in the light of melt inclusion data for etna basalts can be interpreted in terms of escape of gases from partially and variably degassed magma at different depths beneath the summit gases released from the three main summit craters bocca nuova voragine and northeast had an identical composition controlled by bulk degassing of a single magma body that had previously lost c 25 0 of its original sulphur the similar gas composition at all three main craters suggests that these are connected to a central conduit system that branches at relatively shallow depth measurements of the bulk volcanic plume on the same day c 7 km downwind show that degassing from these craters dominated the total gas output of the volcano and that no significant chemical evolution occurred within the plume over a time scale of c 12 min weaker gas emissions from the southeast crater were comparatively depleted in so2 so2 hc1 and so2 hf ratios a factor of two lower implying that this crater is fed either by a separate conduit or by a branch of the central conduit whose geometry favours solubility controlled volatile fractionation still lower so2 hc1 and so2 hf ratios measured for residual degassing of a lava flow erupted from the southeast crater verify the lower solubility and earlier escape of sulphur compared to halogens at etna fractional magma degassing is also implied by strong chemical contrasts between the bulk volcanic plume and fissure gas emissions measured during the july august 2001 flank eruption these results highlight the ability of ftir spectrometry to detect fine spatial and temporal variations in magma degassing processes and thereby constrain models of shallow plumbing systems introduction magmas contain dissolved volatiles h20 co2 s c1 f etc with differing solubility behaviom which gradually reach a saturation pressure and exsolve into a separate gas phase bubbles during magma ascent and crystallization this volatile phase plays a central role in magmatic and volcanic processes e g anderson 1975 and its chemical composition changes from depth to the surface according to the pressure controlled solubility behaviour of each volatile species but also as a function of the dynamics of magma supply and ascent sparks 2003 this volume in fact gas bubbles may rise with either the same velocity as surrounding magma allowing continuous gas melt equilibration and single step bulk gas emission at the surface or with a higher velocity thereby reaching the surface independently of the parental magma batch e g sparks 1978 vergniolle jaupart 1986 in the latter case chemical equilibrium between gas and magma may be inhibited sustained high gas fluxes in excess of lava production on basaltic volcanoes such as etna and stromboli typically require a separated bubble flow and in the long term convective renewal of volatile rich magma from depth francis

high resolution satellite and airborne thermal infrared imaging of precursory unrest and 2009 eruption at redoubt volcano alaska abstract a combination of satellite and airborne high resolution visible and thermal infrared tir image data detected and measured changes at redoubt volcano during the 2008 2009 unrest and eruption the tir sensors detected persistent elevated temperatures at summit ice melt holes as seismicity and gas emissions increased in late 2008 to march 2009 a phreatic explosion on 15 march was followed by more than 19 magmatic explosive events from 23 march to 4 april that produced high altitude ash clouds and large lahars two or three lava domes extruded and were destroyed between 23 march and 4 april after 4 april the eruption extruded a large lava dome that continued to grow until at least early july 2009

global observations of the land breeze 1 four times daily satellite wind observations from the quikscat and adeos ii tandem scatterometer mission are used to study the land sea breeze circulation these observations provide a global view of diurnal wind variations over the ocean results agree with frictional linear theory winds follow an elliptical hodograph through the course of the day but indicate that diurnal wind variations propagate offshore progressively like nonlinear gravity waves and are detectable several hundred kilometers from the coast

effects of a volcanic plume on thermal imaging data ground based thermal imaging is becoming an increasingly important tool for volcano surveillance however the impact of volcanic plumes on quantitative measurements of surface temperature has not been previously evaluated here we use a radiative transfer model to simulate gas primarily h2o and so2 and aerosol absorptions over the path between a thermal camera and a heat source on stromboli volcano italy a ftir spectrometer was used to quantify path amounts of gases likely to be encountered when making thermal measurements of the active craters we find that when using a camera sensitive from 7 5 to 13 mu m underestimates of similar to 400 k may be produced when viewing a source with an actual temperature of 1200 k cameras that operate between 3 and 5 mu m are somewhat less susceptible to these errors

radiative temperature measurements at kupaianaha lava lake kilauea volcano hawaii field spectroradiometer data in the wavelength range of 0 4 2 5 m and spectral resolution of 1 5 nm have been used to compute the radiative temperature of the surface of kupaianaha lava lake kilauea volcano hawaii two sets of observations a total of 120 spectra were made on october 12 1987 and january 23 1988 when the lava lake was in a period of active overturning the area of the surface for which temperatures were measured was 0 23 0 55 m2 two numerical models of two and three components have been used to match the measured radiant flux ratios and to describe the surface of the lava pond in terms of radiant area and temperature three stages of activity on the lake surface are identified stage 1 characterized by magma fountaining and overturning events exhibited the hottest crustal temperatures 180 572 c and the largest fractional hot areas 10 3 stage 1 average flux densities were 2 2 104 w m2 the highest recorded for the three stages of activity on either day the largest radiative area of fresh magma was 29 at 1100 c while cooling from magmatic temperatures to newly formed crust at 790 c took place in a matter of seconds stage 2 marked by rifting events between plates of crust exhibited crustal temperatures between 100 and 340 c with fractional hot areas at least an order of magnitude lower than those found for stage 1 average flux densities calculated for three examples of stage 2 activity were 5 3 103 w m2 stage 3 which was quiescent periods when the lake was covered by a thick crust dominated the activity of the lake both temporally and spatially over 90 of the time the characteristic crustal temperature of stage 3 was 80 345 c with most solutions near 200 300 c and fractional hot areas of 10 5 of the viewing area average flux densities for stage 3 were 4 9 103 w m2 for many stage 3 examples a two component model was sufficient to describe the spectral data however for almost all of the stage 1 and 2 examples and the remainder of the stage 3 examples a three component model was required these determinations of lava temperature and radiant area have relevance for satellite and airborne measurements of the thermal characteristics of active volcanoes and indicate that temporal variability of the thermal output of lava lakes occurs on the time scale of seconds to minutes

the formation of an anabranching planform in a sandy floodplain by increased flows and sediment load anabranching rivers evolve in various geomorphic settings and various river planforms are present within these multi channel systems in some cases anabranches develop meandering patterns such river courses existed in europe prior to intensive hydro technical works carried out during the last 250 years proglacial stream valleys inherited from the last glaciation provided a suitable environment for the development of anabranching rivers wide valleys floors with abundant sand deposits the main objective of the present study is to reconstruct the formation of an anabranching river planform characterized by meandering anabranches based on geophysical and geological data obtained from field research and a reconstruction of palaeodischarges a model of the evolution of an anabranching river formed in a sandy floodplain is proposed it is demonstrated that such a river system evolves from a meandering to an anabranching planform in periods of high flows that contribute to the formation of crevasse splays the splay channels evolve then into new meandering flow paths that form second order crevasses avulsions and cutoffs the efficiency of the flow is maintained by the formation of cutoffs and avulsions preventing the development of high sinuosity channels and redirecting the flow to newly formed channels during maximum flow events a comparison with other anabranching systems revealed that increased discharges and sediment loads are capable of forming anabranching planforms both in dryland and temperate climate zones the sediment type available for transport often inherited from older sedimentary environments is an important variable determining whether the channel planform is anabranching with actively migrating channels or anastomosing with stable straight or sinuous branches

surface temperature measurements of active lava flows on kilauea volcano hawai i systematic hand held radiometer measurements of lava surface temperatures in active flows and tubes on kilauea volcano hawai i reveal complexities that cannot be resolved in remotely sensed data from aircraft or satellites using portable infrared minolta land cyclops radiometers we measured surface temperatures of flows at various distances from their sources and investigated cooling rates and the development of crust our measurements suggest that the upper surface of these lava flows can be split into a minimum of four thermal components core 1050 c visco elastic skin 750 900 c rigid solid crust 750 c and flow margins 175 c for the a a flows investigated a cool rigid crust characteristically developed in the central part of channels within 30 m of the source vent and incandescent lava was exposed in the marginal shear zones of channels this affects the heat loss and morphology of lava in active channels our investigations of temperature distributions on pahoehoe flow fields reveal temperature anomalies of up to 150 c above active tubes and tumuli

ground penetrating radar images of selected fluvial deposits in the netherlands ground penetrating radar gpr surveys have been carried out in order to characterise reflection patterns and to assess the method s potential for imaging palaeofluvial sediments in the mass rhine former confluence area in the southern netherlands the results show that the deposits of meandering braided and transitional river types produce characteristic radar facies representative examples of each of these river types were selected where the gpr data could be directly correlated with sedimentary information derived from exposures and detailed drilling and geomorphological data could be supplied individual channels may be distinguished by the radar facies of their fills the floodplains of the different river types also show a characteristic radar facies in gpr data from the meander floodplain parallel dipping reflections represent point bar structures while irregular intersecting small channel patterns that alternate with parallel continuous reflections are more typical in the braid plain a transitional river type shows characteristics of both of these types typical examples of gpr sections recorded in each of the different fluvial palaeoenvironments are presented in an interpretative radar facies chart

diurnal variations of summer precipitation over contiguous china 1 diurnal variations of summer precipitation over contiguous china are studied using hourly rain gauge data from 588 stations during 1991 2004 it is found that summer precipitation over contiguous china has large diurnal variations with considerable regional features over southern inland china and northeastern china summer precipitation peaks in the late afternoon while over most of the tibetan plateau and its east periphery it peaks around midnight the diurnal phase changes eastward along the yangtze river valley with a midnight maximum in the upper valley an early morning peak in the middle valley and a late afternoon maximum in the lower valley summer precipitation over the region between the yangtze and yellow rivers has two diurnal peaks one in the early morning and another in the late afternoon

emissivity of terrestrial materials in the 3 5 μm atmospheric window remotely sensed infrared radiance emitted by a surface is a function both of its kinetic temperature and its spectral emissivity consequently assumptions are usually made about the emissivity of earth surface materials to allow their temperatures to be determined or vice versa to increase the accuracy of these assumptions the directional hemispherical spectral reflectance of a wide range of natural earth surface materials has been measured and is summarized here these include igneous metamorphic and sedimentary rocks desert varnish soils vegetation water and ice kirchhoff s law can be used to predict directional spectral emissivity from these data

is history of rivers important in restoration projects the example of human impact on a lowland river valley the obra river poland abstract palaeoenvironmental and palaeohydrological reconstructions can provide important guidance for river restoration projects this paper reconstructs the trajectory of river pattern changes of a lowland river the obra river western poland as a basis to inform realistic restoration activities the history of river changes is reconstructed for the last 12 700 radiocarbon years bp the sequence and timing of change differ from widely recognized conventional assessments of transitions from braided to meandering planforms in the polish lowlands traces of a laterally migrating anabranching system were found in the middle obra valley in its lower course a transition from a braided to meandering planform took place later than in other rivers of the polish lowlands sediment delivery from parts of the catchment situated downstream of lakes in the river course could have been the main reason for maintenance of the braided pattern restoration scenarios that take into account the trajectory of river planform changes are hypothesized in relation to variations of sediment supply and degree of anthropogenic impact

anastamosing channels in the lower neches river valley texas active and semi active anastomosing holocene channels upstream of the delta in the lower valley of the meandering neches river in southeast texas represent several morphologically distinct and hydrologically independent channel systems these appear to have a common origin as multi thread crevasse channels strongly influenced by antecedent morphology levee breaching leads to steeper cross valley flows toward floodplain basins associated with pleistocene meander scars creating multi thread channels that persist due to additional tributary contributions and ground water inputs results are consistent with the notion of plural systems where main channels tributaries and sub channels may have different morphologies and hydrogeomorphic functions the adjacent trinity and sabine rivers have similar environmental controls yet the trinity lacks evidence of extensive anastomosing channels on its floodplain and those of the sabine appear to be of different origin the paper highlights the effects of geographical and historical contingency and hydrological idiosyncrasy copyright 2014 john wiley sons ltd

morphology and evolution of bars in a wandering gravel bed river lower fraser river british columbia canada a hierarchical typology for the channels and bars within aggradational wandering gravel bed rivers is developed from an examination of a 50 km reach of lower fraser river british columbia canada unit bars built by stacking of gravelly bedload sheets are the key dynamic element of the sediment transfer system linking sediment transport during individual freshets to the creation development and remoulding of compound bar platforms that have either a lateral or medial style primary and secondary unit bars are identified respectively as those that deliver sediment to compound bars from the principal channel and those that redistribute sediment across the compound bar via seasonal anabranches and smaller channels the record of bar accretion evident in ground penetrating radar sequences is consistent with the long term development of bar complexes derived from historical aerial photographs for two compound bars inter annual changes associated with individual sediment transport episodes are measured using detailed topographic surveys and longer term changes are quantified using sediment budgets derived for individual bars from periodic channel surveys annual sediment turnover on the bars is comparable with the bed material transfer rate along the channel indicating that relatively little bed material bypasses the bars bar construction and change are mainly accomplished by lateral accretion since the river has limited capacity to raise bed load onto higher surfaces styles of accretion and erosion and therefore the major bar form morphologies on fraser river are familiar and consistent with those in gravelly braided channels but the wandering style does exhibit some distinctive features for example 65 year histories reveal the potential for long sequences of uninterrupted accretion in relatively stable wandering rivers that are unlikely in braided rivers

diurnal variations of warm season precipitation over northern china abstract this study examines the diurnal variations of the warm season precipitation over northern china using the high resolution precipitation products obtained from the climate prediction center s morphing technique cmorph during may august of 2003 09 the areas of focus are the yanshan taihangshan mountain ranges along the east peripheries of the loess and inner mongolian plateaus and the adjacent north china plains it is found that the averaged peak in local precipitation begins early in the afternoon near the top of the mountain ranges and propagates downslope and southeastward at a speed of 13 m s 1 the peak reaches the central north china plains around midnight and the early morning hours resulting in a broad area of nocturnal precipitation maxima over the plains the diurnal precipitation peak minimum is closely collocated with the upward downward branch of a mountain plains solenoid mps circulation both the mps and a low level southwesterly nocturnal jet are likely to be jointly resp

dryland anabranching river morphodynamics rio capilla salar de uyuni bolivia the dryland anabranching river rio capilla is characterized by nonvegetated and vegetated reaches with prominent channel morphology to identify the morphodynamics of such dryland anabranching systems and their controls we investigated the rio capilla of the southern altiplano plateau using high resolution satellite imagery and field measurements comparison of high resolution satellite data reveals that erosion exceeds deposition for the main channel accompanied by changes in channel planform such as meander and channel morphology on site surveys combined with high precision gps and high resolution satellite imagery show that channels are characterized by shallowness and poor development of levees the study area of the rio capilla is divided into two zones of different slopes zone 1 with a high slope and zone 2 with a low slope zone 1 has a relatively straight main channel with few anabranches and grass covered banks that are stable despite the high gradient whereas zone 2 is typified by more anabranches with nonvegetated banks and the main channel experiences prominent bank accretion and erosion excavations show that point bar deposits are fine sand dominated in two reaches and that river banks primarily consist of silt and clay the limited vegetation cover and abundance of desiccation cracks and macropores make the river bank more erodible leading to pronounced lateral migration in this low gradient dryland river system shallow channels and poor development of levees in combination with in channel accretionary benches result in frequent overbank flooding which results in a high density of crevasse splays over unconsolidated river banks and accretionary benches connection of headcuts and crevasse channels together with lateral migration and chute channels and reactivation of partially abandoned meanders produces an anabranching pattern in such dryland river systems

monitoring eruptive activity at mount st helens with tir image data 1 thermal infrared tir data from the master airborne imaging spectrometer were acquired over mount st helens in sept and oct 2004 before and after the onset of recent eruptive activity pre eruption data showed no measurable increase in surface temperatures before the first phreatic eruption on oct 1 master data acquired during the initial eruptive episode on oct 14 showed maximum temperatures of 330 c and tir data acquired concurrently from a forward looking infrared flir camera showed maximum temperatures 675 c in narrow 1 m fractures of molten rock on a new resurgent dome master and flir thermal flux calculations indicated a radiative cooling rate of 714 j m2 s over the new dome corresponding to a radiant power of 24 mw master data indicated the new dome was dacitic in composition and digital elevation data derived from lidar acquired concurrently with master showed that the dome growth correlated with the areas of elevated temperatures low so2 concentrations in the plume combined with sub optimal viewing conditions prohibited quantitative measurement of plume so2 the results demonstrate that airborne tir data can provide information on the temperature of both the surface and plume and the composition of new lava during eruptive episodes given sufficient resources the airborne instrumentation could be deployed rapidly to a newly awakening volcano and provide a means for remote volcano monitoring

sedimentary products of avulsions in the holocene rhine meuse delta the netherlands abstract the main objective of this study was to describe the characteristics of deposits related to avulsion to determine if avulsion locations can be recognized by characteristic sediment architecture in the rhine meuse delta the majority of avulsion sites is accompanied by crevasse splay deposits with a relatively large areal extent these crevasse splay complexes occur near the base of the overbank deposits of the newly formed channel belt and are similar to avulsion belt deposits described by smith et al sedimentology 36 1989 1 can j earth sci 35 1998 453 the lithology of all investigated crevasse splay deposits ranges from coarse sand to silty clay sand is concentrated in crevasse splay channels and silty and sandy clay occurs as distal deposits and as levee deposits between the channels the total volume of sand is small relative to clay and silt of a total of 91 avulsion sites three sites were studied in detail one each representing the sedimentary architecture of a full nodal avulsion a failed avulsion and a crevasse splay complex that did not lead to avulsion it is concluded that dating evidence of the abandoned and newly formed paleo channel is always required to verify if avulsion really occurred although the presence of large scale sandy crevasse splay deposits in combination with two main meandering channels often indicates avulsion based on a 2 d outcrop or just one cross section it is impossible to determine whether a splay complex was associated with an avulsion or not because the architecture and lithology in both cases can be identical not all avulsion locations are characterized by crevasse splay deposits there are two possible explanations for this 1 splay deposits were eroded by the newly formed channel or 2 splay deposits were never formed this may be a result of reoccupation of an old channel in this case avulsive flow is immediately appropriated by the pre existing channel and no large scale splay formation occurs alternatively splay deposits were not formed because avulsion resulted from headward erosion

numerical simulations of the boundary layer jet off the southeastern coast of china abstracta strong coastal boundary layer jet cblj 8 m s 1 off the southeastern coast of china around 28 n 122 e is found from the july 2006 11 hourly model data simulated by the advanced research weather research and forecasting model wrf arw with a 9 km horizontal grid the southerly cblj has a jet core at the 925 hpa level located along the western periphery of the west pacific subtropical high wpsh the cblj is mainly contributed by large scale enhancement by diurnal forcing and orographic effects by the coastal terrain along the southeastern china coast and the terrain of taiwan although the geostrophic winds offshore are faster in the afternoon due to the larger east west pressure gradient caused by land surface heating over the china plain the cblj has a nocturnal 0200 lst maximum in the afternoon hours easterly ageostrophic winds driven by differential land sea thermal heating develop at low levels after sunset with the disappearance of land surface heating the ageostrophic win

thermal imaging and analysis of short lived vulcanian explosions at volcan de colima mexico abstract vulcanian explosions present a major hazard at many active volcanoes but they also provide useful insights into the underlying behaviour of the volcanic system and therefore require close monitoring thermal infrared cameras are an effective tool for imaging vulcanian explosion plumes since they capture detailed temperature information and can reveal the internal dynamics of the plume forming explosions high spatial resolution thermal images of 200 small to moderate sized vulcanian explosions from the summit crater of volcan de colima mexico recorded between 2006 and 2011 were analysed to distinguish different event types and develop an explosion classification scheme explosions display a broad spectrum of sizes and characteristics ranging between two typical end members large impulsive events producing rapidly ascending explosion plumes up to heights of 600 1600 m above the crater rim and small diffusive events with plumes restricted to heights 1 to 29 m s 1 a time series of thermal imagery throughout the period 2006 2011 reveals a weak relationship between apparent plume temperatures and lava dome extrusion with the highest explosion temperatures coinciding with the onset of dome growth in early 2007 temporal variations in the source locations of explosions across the summit crater are also identified and appear to show a close relationship to the patterns of lava dome growth and thermal evolution with explosion source locations associated with the highest temperature thermal features

quantitative imaging of volcanic plumes results needs and future trends abstract recent technology allows two dimensional imaging of trace gas distributions in plumes in contrast to older one dimensional remote sensing techniques that are only capable of measuring total column densities the new imaging methods give insight into details of transport and mixing processes as well as chemical transformation within plumes we give an overview of gas imaging techniques already being applied at volcanoes so2 cameras imaging doas ft ir imaging present techniques where first field experiments were conducted led lidar tomographic mapping and describe some techniques where only theoretical studies with application to volcanology exist e g fabry perot imaging gas correlation spectroscopy bi static lidar finally we discuss current needs and future trends in imaging technology

gpr and aerial imageries to identify the recent historical course of the obra river and spatial extent of obrzanskie lake altered by hydro technical works ground penetrating radar gpr measurements have been conducted to retrace the natural course of the obra river and changes of spatial extent of obrzanskie lake western poland the obra river valley was subjected to intensive anthropogenic transformation three artificial canals were constructed here in the beginning of the nineteenth century the gpr surveys were done using a georadar mala proex equipped with 250 mhz antenna the measurement was verified by coring and analyses of historical maps aerial photographs and satellite images the research has shown that there are at least three elongated depressions preserved in the modern land surface near the village of solec situated in the middle course of the valley several structures suggesting functioning of a multi channel pattern in the past have been detected inside and in the vicinity of the depressions filling the channels with silts and peats might have been the effect of flow deceleration caused by the construction of the obra canals moreover situation of two of the retraced depressions suggests that the landforms might be the remains of a river bed disappearing in wetlands further studies including groundwater flux measurements in the area between the depressions are needed to confirm such hypothesis furthermore the study allowed retracing the spatial extent of obrzanskie lake the sediment structures detected by the gpr measurements and calibrated with coring were interpreted to be the traces of the lake shoreline the interpretation was supported by the findings inferred from aerial and satellite images it was shown that obrzanskie lake had had at least three islands and had been directly connected with a network of braided channels before the anthropogenic intervention the spatial extent of the lake was significantly altered by the construction of the north obra canal disconnecting the lake from the canal resulted in more than 50 decrease of the lake surface

impacts of mountain plains solenoid on diurnal variations of rainfalls along the mei yu front over the east china plains abstractconvection permitting numerical experiments using the weather research and forecasting wrf model are performed to examine the impact of a thermally driven mountain plains solenoid mps on the diurnal variations of precipitation and mesoscale convective vortices along the mei yu front over the east china plains during 1 10 july 2007 the focus of the analyses is a 10 day simulation that used the 10 day average of the global analysis at 0000 utc as the initial condition and the 10 day averages every 6 h as lateral boundary conditions with diurnal variations only despite differences in the rainfall intensity and location this idealized experiment successfully simulated the observed diurnal variation and eastward propagation of rainfall and mesoscale convective vortices along the mei yu front it was found that the upward branch of the mps along with the attendant nocturnal low level jet is primarily responsible for the midnight to early morning rainfall enhancement along the mei yu front th

thermally driven diurnally periodic wind signals off the east coast of china abstractthe characteristics of thermally driven diurnally periodic wind signals off the east coast of china are studied using hourly model data for the period june 2006 11 simulated with a mesoscale model analysis of these model data indicates low level diurnally periodic wind signals propagate eastward off the southeast coast whereas diurnal wind variations off the northeast coast are nearly in phase it is found that a simple 2d linear land sea breeze model with friction can capture this main difference in propagation character with respect to latitude idealized simulations using a simplified version of the mesoscale model that includes surface heating and terrain are found to explain certain features not captured by the present linear theory such as the absolute time phase and cross coast location of the maximum amplitude of the diurnally periodic winds

the detection and significance of diurnal pressure and potential vorticity anomalies east of the rockies abstract harmonic analysis of pressure temperature and precipitation data from 1000 automated surface observing system asos stations reveals a mix of stationary and east west moving disturbances east of the rockies optimization of the pressure data using a temperature based tide assumption separates a strong sun following continentally enhanced tide from a smaller eastward propagating wave epw the latter signal moves at a similar speed to the previously discovered eastward moving precipitation systems analysis of asos summer precipitation data confirms eastward propagation but east of 90 w it shows nonpropagating diurnal convection at a fixed local time i e 1800 lst analysis of winter days still finds the epw suggesting that it is the cause and not the result of the propagating precipitation a possible mechanism for the epw is developed from the linear bousinesq equations with heating and wind shear solutions show eastward moving diurnal pulses of potential vorticity pv generated by

monitoring the december 2015 summit eruptions of mt etna italy implications on eruptive dynamics abstract a lengthy period of eruptive activity from the summit craters of mt etna started in january 2011 it culminated in early december 2015 with a spectacular sequence of intense eruptive events involving all four summit craters voragine bocca nuova new southeast crater and northeast crater the activity consisted of high eruption columns strombolian explosions lava flows and widespread ash falls that repeatedly interfered with air traffic the most powerful episode occurred on 3 december 2015 from the voragine after three further potent episodes from the voragine activity shifted to the new southeast crater on 6 december 2015 where strombolian activity and lava flow emission lasted for two days and were fed by the most primitive magma of the study period activity once more shifted to the northeast crater where ash emission and weak strombolian activity took place for several days sporadic ash emissions from all craters continued until 18 december when all activity ceased although resembling the summit eruptions of 1998 1999 which also involved all four summit craters this multifaceted eruptive sequence occurred in an exceptionally short time window of less than three days unprecedented in the recent activity of mt etna it also produced important morphostructural changes of the summit area with the coalescence of voragine and bocca nuova in a single large crater the central crater reproducing the morphological setting of the summit cone before the formation of bocca nuova in 1968 the december 2015 volcanic crisis was followed closely by the staff of the etna observatory to monitor the on going activity and forecast its evolution in accordance with protocols agreed with the italian civil protection department

downstream channel changes on a contracting anabranching river the lachlan southeastern australia abstract downstream trends in flow channel morphology and sediments were investigated over 220 km of the middle and upper alluvial lachlan river in southeastern australia the lachlan is a perennial river that rises from temperate humid highlands and flows inland into a semiarid low gradient plain lacking perennial tributaries long daily stage records were used to calculate flow parameters and flood frequencies in single and anabranching channel reaches of the river morphological trends were based on cross section and height data compiled from new and water authority data and from particle size trends constructed from bed and bank sediment samples mean and peak flows channel size and bed particle size all diminish in a downstream direction in the partially confined piedmont zone channel and floodplain morphology feature large flood effects and large channel dimensions that reflect extreme flow variability on the alluvial plains the unconfined single channel contracts with distance downvalley and anabranches develop at high flow stages the development of a full anabranching pattern is associated with large flood volume losses diminishing flood volumes mean flows and channel dimensions is attributed to storage of flood waters in lakes floodways and lagoons and through transmission losses during overbank flows the frequency of bankfull discharge consistently decreases downstream and may reflect the long duration and lower frequency of floods in the lower reaches of the river particle size of bed sediment fines downstream at rates consistent with those reported from sand bed rivers elsewhere this is attributed to a combination of hydraulic sorting and low rates of sediment supply from the catchment

variability of warm season cloud episodes over east asia based on gms infrared brightness temperature observations abstract the present study has used the geostationary meteorological satellite gms ir brightness temperature observations to investigate the regional and intraseasonal variability of east asian warm season cloud precipitation episodes in distance time space due to land sea contrast and latitudinal effects the data period was may august 1998 2001 and harmonic analysis was employed as the major tool for analysis the full domain of study 20 40 n 95 145 e was divided into northern and southern zones and into eastern and western sectors and statistics of episodes in each subregion were derived and compared for latitudinal effects episodes were found to be significantly larger in span and duration in northern 30 40 n than in southern 20 30 n zones in the northern zone the propagation characteristics were also stronger and remain evident even in midsummer while episodes south of 30 n reversed in direction and traveled westward in july and august for land sea contrast the may august tra

avulsions channel evolution and floodplain sedimentation rates of the anastomosing upper columbia river british columbia canada ages of channels of the anastomosing upper columbia river south eastern british columbia canada were investigated in a cross valley transect by c 14 dating of subsurface floodplain organic material from beneath levees the avulsion history within the transect was deduced from these data and morphological stages in channel development were recognized additionally floodplain sedimentation rates were established the new data demonstrate that the upper columbia river is a long lived dynamic anastomosing system results show that anastomosis at the study location has persisted since at least 2700 cal years bp with avulsions occurring frequently at least nine channels have formed in the studied cross valley transect within the past 3000 years channel lifetimes from formation to abandonment appear to be highly variable ranging from approximately 800 to 3000 years log jams provoking avulsions and or silting up of old channels are proposed as reasons for this variability long term average floodplain sedimentation rates appear to be significantly lower than previously proposed by smith 1983 int assoc sedimentol spec publ 6 155 168 a long term 4550 years average of 1 75 mm per year after compaction was based on c 14 dates whilea short term sedimentation rate of 0 8 mm was determined for a single relatively small seasonal flood in 1994 using sediment traps however short term sedimentation rates vary considerably over the floodplain with levees aggrading up to four times faster than floodbasins channels of the upper columbia river anastomosed reach follow a consistent pattern in their development with each stage being characterized by different morphology and processes channel evolution comprises the following succession 1 avulsion stage in which a crevasse splay channel deepens by scour and levee sedimentation 2 widening and deepening stage in which bank slumping and bed scouring dominates 3 infilling stage in which either channel narrowing bank accretion or channel shallowing bed accretion takes place and 4 abandonment stage in which the residual remnant channel is filled exclusively by silt clay and organic material vertical stacking super imposition of active channels on recent channel fill sand bodies is a notable feature of the upper columbia river which suggests that reoccupation of residual channels is a common process

diurnal variations of precipitation deep convection and lightning over and east of the eastern tibetan plateau abstract diurnal cycles of total rainfall precipitation features mesoscale convective systems mcss deep convection precipitation vertical structure and lightning over the eastern tibetan plateau tp and eastward through china are investigated using 11 yr of tropical rainfall measuring mission trmm measurements diurnal cycles of rainfall and precipitation features present apparent phase propagation eastward from the eastern tp for about 1000 km the phase propagation is most evident during the pre mei yu and mei yu seasons however it weakens with the northward progress of the east asian monsoon and ceases in midsummer during the pre mei yu season diurnal cycles of storm population total rainfall deep convection and lightning over the central and eastern tp foothills are in phase peaking during the early morning another striking feature of the pre mei yu season is that nocturnal rainfall and mcss prevail over the southeastern tp foothills following the deep convection and lightning maxim

mechanisms supporting long lived episodes of propagating nocturnal convection within a 7 day wrf model simulation abstract a large domain explicit convection simulation is used to investigate the life cycle of nocturnal convection for a one week period of successive zonally propagating heavy precipitation episodes occurring over the central united states similar to climatological studies of phase coherent warm season convection the longest lived precipitation episodes initiate during the late afternoon over the western great plains 105 100 w reach their greatest intensity at night over the central great plains 100 95 w and typically weaken around or slightly after sunrise over the midwest 95 85 w the longest lived episodes exhibit average zonal phase speeds of 20 m s 1 consistent with radar observations during the period composite analysis of the life cycle of five long lived nocturnal precipitation episodes indicates that convection both develops and then propagates eastward along an east west oriented lower tropospheric frontal zone an elevated 2 km deep layer of high e air helps sustain convect

a climatology of warm season cloud patterns over east asia based on gms infrared brightness temperature observations abstract in the present study hourly infrared ir brightness temperatures observed by the geostationary meteorological satellite gms over the region 20 40 n 95 145 e in may august 1998 2001 are used to compile a climatology of warm season cloud precipitation episodes over east asia with a goal to better understand the characteristics of warm season convection and the behavior of these episodes results are compared with those obtained in north america using radar derived data the convection in east asia similar to that in north america is shown to also exhibit coherent patterns and characteristics of propagating events in the longitude time hovmoller space with a preferred phase speed of 10 25 m s 1 considerably faster than warm season synoptic scale waves near the eastern edge of the tibetan plateau convection was most active with a strong diurnal signal peaking in late afternoon or early evening then propagating eastward the zonal span and duration of episodes could reach 3000 km and

diurnal cycle of surface winds over the subtropical southeast pacific 1 the diurnal variability of surface winds over the se pacific is characterized with quikscat data for years 2000 2006 the twice daily satellite passes occur around 0600 and 1800 lt referred to as am and pm respectively the pm am wind difference maximizes in a region between 20 s and 30 s extending from the chilean coast up to 75 w this difference is mostly meridional along the coast with seasonal variation characterized by summertime weakening of the morning winds the observational analysis is supplemented with mesoscale model results for december 2003 they show that the coastal zonal flow increases between 0600 and 1200 local time lt but then decreases in the next 6 hours which explains the absence of an onshore component in the quikscat pm am difference additional model diagnostics show that in this region the diurnal cycle hodographs are more simple and larger above the marine boundary layer mbl than at the surface evaluation of the momentum and temperature budgets reveals the importance of the diurnal cycle of vertical velocity coupled with the thermal structure in controlling the diurnal cycle of the low level winds around 1300 lt coastal subsidence maximizes in a layer sloping from 1000 m at 36 s to 3000 m at 22 s inducing the development of a coastal trough at the surface during the night the passage of a high pressure perturbation reverses the surface meridional pressure gradient force inducing the decrease of the coastal meridional winds these results stress the important role played by the dynamics of the low troposphere above the mbl e g the heating of the andes cordillera to the east in controlling the wind diurnal cycles near the surface

impact of vertical wind shear on gravity wave propagation in the land sea breeze circulation at the equator abstractthe impact of vertical wind shear on the land sea breeze circulation at the equator is explored using idealized 2d numerical simulations and a simple 2d linear analytical model both the id

radar facies of paraglacial barrier systems coastal new england usa analysis of a large data base of ground penetrating radar gpr profiles from both natural and developed paraglacial barriers along the coast of new england has allowed identification of eight reflection configurations that characterize this type of mid to high latitude coastal environment bedrock anchor points yield primarily hyperbolic configurations whereas glacial anchor points and sediment source areas are characterized by chaotic parallel and tangential oblique configurations beaches and dunes produce predominantly sigmoidal oblique hummocky reflection free and bounding surface configurations back barrier sediments may yield basin fill configurations but generally include abundant signal attenuating units the gpr data calibrated with information from cores were collected across swash aligned and drift aligned barriers in a variety of wave and tidal energy settings application of a 120 mhz antenna as used in this study enables portrayal of a range of sedimentary units from individual bedforms on single records to entire barrier elements using large numbers of intersecting gpr sections at maximum vertical resolutions that vary between 0 2 m and 0 7 m the most important drawback of gpr in the coastal environment is attenuation of the electromagnetic em signal by layers of salt marsh peat or by brackish or salty groundwater primarily along barrier edges this disadvantage is offset by many benefits data can be collected at rates of several km per day making gpr an excellent reconnaissance tool a core that is used in the calibration of gpr data can be matched with great accuracy to its position on the complementary gpr record allowing detailed correlation between lithostratigraphy and reflection configuration