2 3 day convective variability in the tropical western pacific abstract this paper is an examination of 2 3 day convective variability in the tropical pacific region the initial focus of the paper is on the western tropical pacific during the tropical ocean global atmosphere coupled ocean atmosphere response experiment toga coare intensive observation period iop high spatial and temporal resolution outgoing longwave radiation olr data and sea surface temperatures are filtered to eliminate diurnal and lower frequency variability the propagation of the 2 3 day convective variability is also studied westward propagation appears to be favored in some regions indicative of the events being influenced by westward propagating inertio gravity waves however many regions have 2 3 day events that divide fairly equally into eastward and westward propagations indicating that both eastward and westward propagating inertio gravity waves are influencing the oscillation the sst data during the 4 month iop dataset show evidence of a 2 3 day variability during those con

linking morphodynamic response with sediment mass balance on the colorado river in marble canyon issues of scale geomorphic setting and sampling design 1 measurements of morphologic change are often used to infer sediment mass balance such measurements may however result in gross errors when morphologic changes over short reaches are extrapolated to predict changes in sediment mass balance for long river segments this issue is investigated by examination of morphologic change and sediment influx and efflux for a 100 km segment of the colorado river in grand canyon arizona for each of four monitoring intervals within a 7 year study period the direction of sand storage response within short morphologic monitoring reaches was consistent with the flux based sand mass balance both budgeting methods indicate that sand storage was stable or increased during the 7 year period extrapolation of the morphologic measurements outside the monitoring reaches does not however provide a reasonable estimate of the magnitude of sand storage change for the 100 km study area extrapolation results in large errors because there is large local variation in site behavior driven by interactions between the flow and local bed topography during the same flow regime and reach average sediment supply some locations accumulate sand while others evacuate sand the interaction of local hydraulics with local channel geometry exerts more control on local morphodynamic response than sand supply over an encompassing river segment changes in the upstream supply of sand modify bed responses but typically do not completely offset the effect of local hydraulics thus accurate sediment budgets for long river segments inferred from reach scale morphologic measurements must incorporate the effect of local hydraulics in a sampling design or avoid extrapolation altogether

sediment budgeting a case study in the katiorin drainage basin kenya the primary objective of this study was to compute a detailed budget for a small semiarid tropical drainage basin in kenya results indicated that transfer of sediments inputs from primary source areas was minor in comparison to changes in storage the major sediment source area within the katiorin drainage basin was the colluvial hillslope zone the net change in storage within this zone was approximately 2100 mg yr 1 surface wash and rilling were the dominant transport processes responsible for the remobilization of colluvial sediments sediment storage within the in channel reservoir increased by 60 mg yr 1 which was minor when compared to the total store of sediment in this reservoir during 1986 the channel network stored only a small fraction 3 per cent of the sediment delivered from the hillslope subsystem therefore the in channel reservoir had limited influence on sediment conveyance to the basin outlet these data indicate that a static equilibrium condition cannot be assumed within the katiorin drainage basin such an assumption would result in erosion estimates of approximately 5 5 mm yr 1 for the entire basin based on a sediment output of 7430 mg km 2 yr 1 and a measured bulk density of 1 35 mg m 3 however this masked the actual rates of 1 2 to 7 1 mm yr 1 in subbasin primary source areas and rates of 0 6 to 17 mm yr 1 for colluvial material in the various subbasins the extreme accelerated erosion rates resulted from minimal ground vegetation steep slopes soil crust formation an erodible substrate and a well integrated drainage network for rapid conveyance of sediments from the hillslope subsystem to the basin outlet

sources sinks and storage of river sediment in the atlantic drainage of the united states the history of sediment and its movement in the atlantic drainage demonstrate some of the difficulties of modeling sediment on a river basin scale soil erosion was accelerated by a factor of at least 10 when european settlers cleared forests and planted crops although increasing soil conservation practice and decreasing crop farming have since reduced the rates of erosion large quantities of eroded material are still stored on hillslopes and in stream valleys where they continue to augment the sediment loads of the rivers the sediment from this episode of erosion that is largely past can be expected to emerge from storage for many decades and perhaps even several centuries to come the reservoirs that have been built on many of the major rivers trap significant portions of the moving sediment which in some places may be remobilized by large floods essentially all the river sediment that reaches the atlantic coastal zone is trapped in estuaries and coastal marshlands probably less than 5 is deposi

multiscale aspects of convective systems associated with an intraseasonal oscillation over the indonesian maritime continent abstract multiscale aspects of convective systems over the indonesian maritime continent in the convectively active phase of an intraseasonal oscillation iso during november 2002 are studied using geostationary meteorological satellite infrared data and ground based observational data from x band rain radar equatorial atmosphere radar l band boundary layer radar and upper air soundings at koto tabang kt 0 20 s 100 32 e 865 m above mean sea level west sumatera indonesia in the analysis period four super cloud clusters sccs horizontal scale of 2000 4000 km associated with an iso are seen to propagate eastward from the eastern indian ocean to the indonesian maritime continent the sccs are recognized as envelopes of convection composed of meso scale cloud clusters m ccs horizontal scale of 500 1000 km propagating westward when sccs reach the indonesian maritime continent the envelopes disappear but m ccs are clearly observed over sumatera the evolution and structure of a distinct

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

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

dam to delta sediment inputs and storage in the lower trinity river texas livingston dam on the trinity river in se texas usa disrupts the transport of sediment to the lower trinity river and the trinity bay galveston bay estuary however a sediment budget of the lower basin shows that the effects of this disruption are undetectable in the lower river sediment trapped in lake livingston is partly offset by channel erosion downstream of the dam and by inputs from the lower basin most importantly however the lower coastal plain reaches of the trinity are characterized by extensive alluvial storage and are a bottleneck that buffers the bay from effects of upstream changes in sediment flux storage is so extensive that the upper trinity basin and the lowermost river reaches were essentially decoupled in the sense that very little upper basin sediment reached the lower river long before the dam was constructed whereas sediment storage in lake livingston is extensive alluvial storage on the trinity flood plain is even more extensive dam related sediment starvation effects are noted for about 52 km downstream and the sediment budget suggests that a majority of the sediment in this reach is likely derived from channel scour and bank erosion the capacious alluvial storage in the lower trinity not only limits flux to the bay but the large amount of remobilizable alluvium also allows the system to adjust to localized sediment shortages as illustrated in the dam to romayor reach internal adjustments within the lower trinity river valley thus buffer the bay from changes in sediment supply upstream

using sediment fingerprints to assess sediment budget errors north halawa valley oahu hawaii 1991 92 reliable estimates of sediment budget errors are important for interpreting sediment budget results sediment budget errors are commonly considered equal to sediment budget imbalances which may underestimate actual sediment budget errors if they include compensating positive and negative errors we modified the sediment fingerprinting approach to qualitatively evaluate compensating errors in an annual 1991 fine 63 m sediment budget for the north halawa valley a mountainous forested drainage basin on the island of oahu hawaii during construction of a major highway we measured concentrations of aeolian quartz and 137cs in sediment sources and fluvial sediments and combined concentrations of these aerosols with the sediment budget to construct aerosol budgets aerosol concentrations were independent of the sediment budget hence aerosol budgets were less likely than sediment budgets to include compensating errors differences between sediment budget and aerosol budget imbalances therefore provide a measure of compensating errors in the sediment budget the sediment budget imbalance equalled 25 per cent of the fluvial fine sediment load aerosol budget imbalances were equal to 19 per cent of the fluvial 137cs load and 34 per cent of the fluvial quartz load the reasonably close agreement between sediment and aerosol budget imbalances indicates that compensating errors in the sediment budget were not large and that the sediment budget imbalance is a reliable measure of sediment budget error we attribute at least one third of the 1991 fluvial fine sediment load to highway construction continued monitoring indicated that highway construction produced 90 per cent of the fluvial fine sediment load during 1992 erosion of channel margins and attrition of coarse particles provided most of the fine sediment produced by natural processes hillslope processes contributed relatively minor amounts of sediment 1998 john wiley sons ltd

synoptic scale disturbances near the equator abstract a spectral analysis of winds analyzed and initialized at the european centre for medium range weather forecasts reveals an abundance of power in the 850 mb meridional wind along the equator with periods near four days the power is mostly in the westward propagating component using high pass filtered data it is shown that the waves have westward phase and eastward group propagation relative to the mean wind the longest wavelengths are found over the pacific ocean while the shortest are found over the convectively variable regions of indonesia south america and africa mean phase speeds at 850 mb are positively correlated with the mean wind on the equator at 500 mb and below and negatively correlated with the mean wind above that level the effective advecting zonal wind of the disturbances seems to be the density weighted average of the lower troposphere the structure of the disturbances bears resemblance to the expected structure of an equatorially trapped mixed rossby gravity wave over t

fluvial sediment budgets in the north carolina piedmont phillips j d 1991 fluvial sediment budgets in the north carolina piedmont geomorphology 4 231 241 sediment budgets for four large 1000 km 2 drainage basins in the piedmont physiographic province of north carolina were estimated from data compiled during erosion and sedimentation surveys budgets for the upper tar upper neuse haw and deep river basins showed broadly similar trends in allocation of eroded sediment among yield and storage sediment yield as a percentage of mean annual gross erosion within the basins averaged 10 this was less than the rate of alluvial storage which averaged 14 of annual gross erosion about 76 of the mean annual erosion was stored as colluvium on hillslopes there are relatively small differences in sediment delivery and storage ratios among the study basins this suggests that the relative order of magnitude of the allocation of eroded sediment for southern piedmont rivers is colluvial storage alluvial storage and yield of the sediment that does reach the streams more than half is stored as alluvium on an average annual basis aggrading channels and floodplains siltation of benthic habitats and sediment pollution problems are thus likely to persist unless dramatic reductions in upland erosion or in sediment delivery to streams are realized with respect to longer term basin evolution results point to the need for an improved understanding of the temporal scales of colluvial and alluvial sediment storage

multiscale organization of convection simulated with explicit cloud processes on an aquaplanet abstract this study investigated the multiscale organization of tropical convection on an aquaplanet in a model experiment with a horizontal mesh size of 3 5 km for a 10 day simulation and 7 km for a 40 day simulation the numerical experiment used the nonhydrostatic icosahedral atmospheric model nicam with explicit cloud physics the simulation realistically reproduced multiscale cloud systems eastward propagating super cloud clusters sccs contained westward propagating cloud clusters ccs sccs ccs had zonal sizes of several thousand hundred kilometers typical propagation speed was 17 10 m s 1 smaller convective structures such as mesoscale cloud systems mcs of o 10 km and cloud scale elements 16 km of o 100 km area was also reproduced planetary scale equatorial waves with wavelengths of 10 000 and 40 000 km had a major influence on the eastward propagation of the simulated scc destabilization east of the

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

diurnally forced tropical tropospheric circulation over south america abstract the impact of diurnally varying thermal forcing on the tropical circulation is studied with a linearized shallow water model on an equatorial beta plane the mass and flow fields are interpreted as an internal mode with equivalent depth of the order of 250 m this is the preferred vertical mode excited by typical cumulus heating profiles in the tropics the diurnal forcing with the horizontal scale of the amazon source partitions approximately 40 of the input energy to slow modes the fast modes are trapped by the critical latitudes contributing significantly to oscillations in the divergence field which emanate out of the source region the divergence field at the source is approximately in phase with the forcing the vorticity field lags the forcing by approximately 10 hours a comparison of the model results with the 500 mb level vertical motion derived from the national meteorological center analysis shows a similar pattern of propagating oscillations it is suggested that the diurnally f

production storage and output of coarse upland sediments natural and artificial influences as revealed by research catchment studies rates of sediment production in uk river basins are generally low however upland source areas control both runoff and sediment volumes to he routed through larger basins and there are indications that development pressures on land in upland areas have far reaching implications output rates for bedload from semi natural grassland and commercially afforested catchments are now available for a ten year period at the plynlimon catchments mid wales the influence of forestry drainage practice is to increase bedload yields sixfold suspended load yields are doubled in an attempt to predict yields and to investigate the operation of storage and transport processes on bedload a regression analysis was conducted using the weight of bedload trapped as a dependent variable and selected climatic supply and transport factors as independent variables the climatic supply factors chosen are shown to have little influence on yield relative to transport factors despite evidence of supply limited yields tracer studies indicate that channel storage of material exercises a critical control on yield a factor which is not accommodated by the climate based supply indices implications for field measurement techniques are discussed

horizontal and vertical structure of observed tropospheric equatorial rossby waves equatorial rossby er waves are identified in an 8 year data set of national meteorological center operational analyses the westward moving waves have symmetric circulations about the equator and eastward energy dispersion with maximum zonal wind perturbations along the equator and meridional wind maxima roughly 10 15 off the equator they have maximum amplitude in the lower troposphere and are associated with convective signals at roughly the mean latitude of the tropical convergence zones the circulations thus possess many of the features of the equatorially trapped n 1 rossby modes derived by matsuno 1966 they are generally around zonal planetary wavenumber 6 scale and have a deep nearly equivalent barotropic structure up to 100 mbar this is in contrast with the madden julian oscillation and mixed rossby gravity waves which generally have a first baroclinic mode vertical structure during the intensive observing period iop of the tropical ocean global atmosphere toga coupled ocean atmosphere response experiment coare and in other years westward propagating er disturbances along the equator are observed by using 6 to 30 day filtered circulation data at 850 mbar zonal wind anomalies at 850 mbar are preferentially associated with like signed anomalies in a deep layer at this frequency as was observed during coare the er waves are most common during northern winter in the central pacific although they can be detected sporadically over the other ocean basins and in other seasons as well one source for the equatorial rossby waves appears to be upper level extratropical rossby wave activity propagating into the eastern pacific although the equatorial waves are sometimes present during the northern summer when the extratropical source is absent we cite evidence that propagation of er wave activity from the central into the western pacific is related to occurrences of westerly wind bursts

balanced tropical data assimilation based on a study of equatorial waves in ecmwf short range forecast errors summary this paper seeks to represent the tropical short range forecast error covariances of the european centre for medium range weather forecasts ecmwf model in terms of equatorial waves the motivation for undertaking this investigation is increasing observational evidence indicating that a substantial fraction of the tropical largescale variability can be explained by equatorially trapped wave solutions known from shallow water theory shortrange forecast differences from a data assimilation ensemble were taken to serve as a proxy for background errors it was found that the equatorial waves coupled to convection can explain on average 60 70 of the error variance in the tropical free atmosphere the largest part of this explained variance is represented by the equatorial rossby er modes and a significant percentage pertains to theequatorial inertio gravity eig modes eastwardpropagating eig modes have maximum variance in the stratosphere where the short wave variance in westwardmoving waves is particularly small this feature is most likely related to the phase of the quasi biennial oscillation during the study period suggesting that significant temporal variations could be present in longer term time series of such statistics the vertical correlations for er modes display characteristics similar to those of their extratropical counterparts correlations narrow towards shorter scales and in the stratosphere however the present statistics do not display the significant increase with altitude of the horizontal correlation scale for the height field which is typical for global quasi geostrophic statistics commonly used in current data assimilation schemes furthermore tropospheric er correlations are vertically asymmetric and deeper for the n 1 mode than for higher modes most likely deep convection acting as a generator of equatorial wave motion is the dominant mechanism underlying these results in spite of its relatively small contribution to the tropospheric variance the kelvin wave coupling plays a decisive role for determining the characteristics of the horizontal correlation near the equator eig modes also play an important role for the tropical mass wind coupling these waves have a major impact by reducing the meridional correlation scales and the magnitudes of the balanced height field increments

sediment yield from gullies riparian mass wasting and bank erosion in the upper konto catchment east java indonesia abstract upland watershed rehabilitation programmes in indonesia have faced increased scrutiny for not delivering the desired reductions in downstream sedimentation rates partly this reflects the fact that conservation measures have not been widely adopted or maintained by upland farmers mainly for socio economic reasons another potential explanation is that sediment contributions by gullying riparian mass wasting and bank erosion have been seriously underestimated or even ignored this paper presents estimates of sediment contributions by gullies riparian mass wasting and bank erosion in the upland volcanic konto catchment east java runoff and sediment yield from gullies were studied in two areas with contrasting soils and land use gullies in the maron area few gullies andic cambisols maize and rice cultivation on stable broad based terraces were related to improper drainage of trails roads and yards in the binangsri area more widespread gullying eutric cambisols onion cultivation on forward sloping terraces gullying was further enhanced by the practice of downslope furrowing to promote field drainage estimated annual sediment yields from the two areas were strikingly different at 22 26 and 50 87 mg ha 1 respectively riparian mass wasting was estimated to contribute ca 4 of total sediment yield at maron and 8 19 in the main gully system at binangsri with the higher value in the latter case representing the effect of extreme rainfall in the latter half of the rainy season short term wet season rates of gully wall retreat at binangsri suggested a contribution by bank erosion of ca 3 8 including extreme events as such 11 27 of the annual sediment yield at binangsri was estimated to have come from sources other than surface erosion substantial volumes of sediment 29 107 mg km 1 of river length were also added to streams bordered by irrigated rice fields sawah in non gullied areas mainly through the collapse of the lowermost terraces due to undercutting

runoff and sediment generation on bench terraced hillsides measurements and up scaling of a field based model despite widespread bench terracing stream sediment yields from agricultural hillsides in upland west java remain high we studied the causes of this lack of effect by combining measurements at different spatial scales using an erosion process model event runoff and sediment yield from two 4 ha terraced hillside subcatchments were measured and field surveys of land use bench terrace geometry and storage of sediment in the drainage network were conducted for two consecutive years runoff was 3 0 3 9 of rainfall and sediment yield was 11 30 t ha 1 yr 1 for different years subcatchments and calculation techniques sediment storage changes in the subcatchment drainage network were less than 2 t ha 1 whereas an additional 0 3 1 5 t ha 1 was stored in the gully between the subcatchment flumes and the main stream this suggests mean annual sediment delivery ratios of 86 125 or 80 104 if this additional storage is included the terrace erosion and sediment transport test model developed and validated for the studied environment was parameterized using erosion plot studies land use surveys and digital terrain analysis to simulate runoff and sediment generation on the terraced hillsides this resulted in over estimates of runoff and under estimates of runoff sediment concentration relatively poor model performance was attributed to sample bias in the six erosion plots used for model calibration and unaccounted covariance between important terrain attributes such as slope infiltration capacity soil conservation works and vegetation cover copyright 2005 john wiley sons ltd

organization of convection within the madden julian oscillation convection associated with the madden julian oscillation mjo is organized over a broad range of time and space scales within a large scale envelope of activity the large scale envelope of convection is characterized as an eastward propagating disturbance predominantly of zonal wavenumber 2 which is confined over the warmest waters of the indian and western pacific oceans large scale convection is shifted toward the disturbance s temperature anomaly which appears to result from frictional effects in the boundary layer synoptic and mesoscale convective activity is enhanced within the wet phase of the large scale envelope the increase at synoptic scales occurs uniformly over all scales but little difference in the character of the variability is observed between dry and wet phases the enhanced mesoscale activity within the wet phases exhibits a marked tendency to be organized into westward propagating clusters with periods near 2 days and half wavelengths of about 1000 km the role of these modes for the evolution of the mjo is discussed

squall lines and convectively coupled gravity waves in the tropics why do most cloud systems propagate westward abstractthe coupling between tropical convection and zonally propagating gravity waves is assessed through fourier analysis of high resolution 3 hourly 0 5 satellite rainfall data results show the familiar enhancement in power along the dispersion curves of equatorially trapped inertia gravity waves with implied equivalent depths in the range 15 40 m i e pure gravity wave speeds in the range 12 20 m s 1 here such wave signals are seen to extend all the way down to zonal wavelengths of around 500 km and periods of around 8 h suggesting that convection wave coupling may be important even in the context of mesoscale squall lines this idea is supported by an objective wave tracking algorithm which shows that many previously studied squall lines in addition to 2 day waves can be classified as convectively coupled inertia gravity waves with the dispersion properties of shallow water gravity waves most of these disturbances propagate westward at speeds faster than the background flow to under

variability of sediment removal in a semiarid watershed field and documentary data from walnut gulch watershed an instrumented semiarid drainage basin of approximately 150 km 2 57 mi 2 in southeastern arizona show that 83 of the alluvium removed from the basin during a 15 year erosion episode beginning about 1930 was excavated from the highest order stream the amount of alluvium removed in the erosion episode would have been equal to a covering of about 4 cm 1 6 in over the entire basin the rate of sediment removal during the erosion episode was 18 times greater than the rate of present channel sediment transport production of sediment from slopes and channel throughput at present rates are approximately equal and refilling will not occur under present conditions the channel forms left by the massive evacuation of sediment impose controls on the spatial distribution of tractive force and total stream power that make renewed storage of sediment likely in only a few restricted locations modern instrumented records of a decade or more provide an inadequate perspective on long term sediment movement

suspended sediment exchange through the sub tropical richmond river estuary australia a balance approach major sources of suspended sediments and their exchanges with the continental shelf for the richmond river estuary were investigated during two hydrological years of the major sources of suspended sediment inputs into the richmond river estuary fluvial input from the upper catchment area was about 92 99 of the total yearly balance and more than 90 of this fluvial sediment was transported into the estuary during less than 5 time of the year the richmond river estuary received net sediment input of about 1 2 of the total yearly balance from the continental shelf during dry seasons when upper catchment freshwater input was less than 45 106 m3 bank erosion in the richmond river estuary was least 1 during low to moderate floods mainly due to river training works and large mangrove coverage along the banks percentage of sediment export from the richmond river estuary depends on the magnitude of floods which was evident from 47 export during dry year when the estuary experienced a minor flood compared to 88 export during the wet year when the estuary experienced one minor and one moderate flood

close range digital photogrammetric analysis of experimental drainage basin evolution brasington james smart r m a 2003 close range digital photogrammetric analysis of experimental drainage basin evolution earth surface processes and landforms 28 3 pp 231 247 rae2008 special issue the generation of high quality topographic data for hydrology and geomorphology

butzer down under debates on anthropogenic erosion in early colonial australia abstract the arrival of europeans in the new world and the rapid deforestation for agriculture and settlement that shortly followed resulted in large and rapid increases in soil erosion and sediment aggradation in australia as in parts of north america and other new world sites this event dates to the last several centuries of the common era a period for which we have surprisingly little historical or scientific data capable of informing debates on the impact of european colonisation on soils and erosion these research themes and debates were central to the work of karl butzer who undertook field and archival research in australia to test existing ideas of the timing and magnitude of landscape response to colonisation in this paper the work and impact of butzer in australia is reviewed as part of ongoing scholarship on the impact of colonisation on landscapes to which butzer contributed butzer and helgren 2005 geomorphic records of soil erosion and historical accounts of land use and impact from eastern australia show that european settlement land clearing and agriculture resulted in rapid and often severe increases in erosion in the late eighteenth and early nineteenth centuries mirroring the experience of anthropogenic soil loss experienced in other parts of the world it is postulated that the geomorphic response to european settlement in australia is more complex than researchers have previously noted that in some contexts continues to influence catchment processes decades and centuries after colonisation

bank erosion of an incised upland channel by subaerial processes tasmania australia the headwaters of many rivers are characterized by gullies and incised streams that generate significant volumes of sediment and degrade downstream water quality these systems are characterized by harsh climates ephemeral flows that do not reach bank top and bare cohesive banks of clay and weathered bedrock we investigated the rates and processes of bank erosion in an incised canal that has such characteristics detailed measurements of bank position were made over two years with a purpose built groundprofiler and photo electronic erosion pins peeps stage height and turbidity were also monitored the bare banks eroded at 13 2 mm a 1 erosion is controlled by subaerial processes that loosen bank material observations show that needle ice growth is important in winter and desiccation of clays predominates in summer flows are unable to erode firm cohesive clays from the banks and erosion is generally limited by the availability of loosened material this produces strong hysteresis in turbidity during events peak turbidity is related to the number of days with low flow between events and not peak stage rehabilitation with a moderate cover of grass is able to prevent bank erosion by limiting the subaerial erosion processes projections of current erosion suggest that without vegetation cover the banks are unlikely to stabilize for many years copyright 2000 john wiley sons ltd

late holocene sediment storage in canyons of the colorado plateau field surveys of ten drainage basins 10 to 1 790 km2 in area in the colorado plateau utah and arizona and repeat photography of 156 fluvial environments providing comparative evidence spanning up to 114 yr reveal that two stratigraphic units characterize the alluvial materials on valley floors an older unit deposited generally between 1250 a d 200 yr and 1880 a d 20 yr was dissected by arroyo development by the early twentieth century a younger unit was deposited generally during the period after approximately 1943 5 yr rates of sedimentation in the 1943 1980 period were almost twice the rates in the 1250 1880 period channel storage rates during the two periods of sedimentation are related to drainage basin area by a power function similar to functions relating slope sediment production and sediment yield to drainage basin area storage rates in the 1943 1980 period were about 50 of the rates of slope sediment production the amount of sediment stored in the two units exhibits a definable spatial pattern source streams with basin areas upstream 10 000 km2 alternatively stored or evacuated moderate amounts of sediment in response to upstream evacuations of sediment from the colorado plateau riparian vegetation change and hydro climatic changes in mountain watersheds outside the plateau region

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

a dynamical model of high latitude convection derived from superdarn plasma drift measurements 1 a discrete set of climatological patterns of high latitude ionospheric convection are derived using line of sight plasma drift data from the super dual auroral radar network superdarn the patterns are derived independently for the northern hemisphere and southern hemisphere and for varying solar wind interplanetary magnetic field imf and dipole tilt angle conditions by interpolating between discrete patterns a dynamical model of convection is obtained which can uniquely specify the high latitude electrostatic potential distribution for a wide range of solar wind imf and dipole tilt parameter values accounting for solar wind velocity dependencies in convection leads to better resolving the large scale convection pattern as compared to previous statistical models based on superdarn data it is shown that the mesoscale features of the climatological model compare favorably to the features seen in instantaneous patterns of convection observed with superdarn comparison of the model to other statistical or empirical models derived from ground and space based measurements shows good agreement with most models

the madden julian oscillation observed during the toga coare iop global view abstract during the toga coare intensive observing period november 1992 february 1993 two pronounced madden julian oscillation mjo events associated with super cloud clusters and westerly wind bursts were observed this paper presents a global view of the mjos including the origin of the super clusters in the indian ocean their migration into the maritime continent and the toga coare large scale soundings array lsa in the western equatorial pacific and their rapid decay over cold water of the eastern pacific the structure and evolution of the mjo are examined with emphasis on the coupling between large scale motion and convection because of differences in propagation speeds the positions of maximum zonal wind perturbations relative to deep convection undergo systematic changes during the travel of the mjo however the centers of deep convection always coincide with those of large scale ascent the super cloud cluster accompanies a wide area of warm air in the upper troposphere over the warm

multiscale phenomena in the tropical atmosphere over the western pacific abstract multiscale variabilities in the atmosphere over the tropical western pacific during the 1979 northern hemisphere winter are studied with an aim at identifying possible interactions between phenomena of different spatial and temporal scales based on the convection index information derived from satellite measurements two intra seasonal oscillations isos are identified within the equatorial belt between 0 and 10 s in the analyzed period the two isos accompanied by both rotational and divergent circulations propagate eastward from the indian ocean to the western pacific over the warm pool in the western pacific the isos develop into quasi stationary systems with an enhanced rotational circulation characterized by a strong westerly jet in the lower troposphere the isos appear to interact with a number of regional and synoptic scale phenomena in the maritime continent and western pacific region for example the onset of the monsoon coincides with the arrival of the first iso at northern a

solute sources and transport in an ephemeral badland catchment southeastern alberta canada this study was carried out as part of an investigation of water and sediment budgets in an ephemeral catchment in dinosaur provincial park badlands alberta these badlands have developed in cretaceous mudstones siltstones and sandstones with some glacial and postglacial surficial deposits study objectives were i to identify major solute sources ii to show how these change with storm characteristics and iii to assess the proportion of solutes in the total stream budget field examination rainfall simulation tests and laboratory experiments showed marked variations in solute production on different lithologic surfaces this information when combined with data on threshold precipitation for runoff production from previous experiments made it clear that solute production in the catchment is significantly influenced by storm characteristics observations indicate that in brief low intensity storms runoff occurs only on sandstone miniature pediment and stream channel surfaces solute produc

sediment source and storage in small watersheds on the keuper marls in luxembourg as indicated by soil profile truncation and the deposition of colluvium abstract soil survey reports and soil maps of 11 second order watersheds on the keuper marls in luxembourg were used to establish the extent to which soils were modified by accelerated erosion and colluviation and to calculate the volume of colluvium the amount of truncation of the soil profiles in the eroded area is on average 55 cm of which the equivalent of 36 cm remains in the watersheds as colluvium the 34 of the eroded soil material that has left the watersheds represents the longterm sediment delivery ratio landuse exerted a more powerful control on the production of colluvium than geomorphology the area occupied by colluvial soils c ha which offer good quality land can be predicted from the area under agriculture l ha with the equation c 74 l 56 comparison with palynologically dated colluvium produced figures for sediment yield of the source areas in the range between 700 and 1800 kg ha year

late cenozoic tectonics and denudation in the central kenya rift quantification of long term denudation rates abstract long term average denudation rates were calculated for the last 3 4 million years ma using digital topographic data related to the present surface of the intrarift bahati kinangop plateau in the central kenya rift well established relations between stratigraphy and faulting chronology and a detailed digital topographic database allow reconstruction of the idealized uneroded plateau surface for an area of 710 km2 the reconstruction refers to the time when the plateau came into existence 3 4 2 6 ma due to widespread deposition of ashflow tuffs and subsequent faulting the reconstruction of this palaeosurface is based on erosional surface remnants occurring within the present plateau surface relict surfaces elements were determined by analyzing the present digital surface representation and geological information within a geographical information system gis after generating digital elevation models of the present and palaeosurfaces long term denudation rates were calculated using the elevation difference method about 80 of the study area are characterized by denudation rates between 0 relict parts and 20 m per one million years m ma for deeply eroded plateau regions denudation reaches 80 100 m ma these rates are comparable to denudation rates which are known from other studies in similar settings the gis based approach provides spatially high resolution denudation rates allowing for further regional analysis of factors controlling spatial variations in sediment supply to the rift basin

intensity of in lake processes in floodplain lakes within the bug river zone of fluvial activity the paper presents a new approach to calculating the erosion and deposition values of floodplain lake basins the erosion deposition index edi the edi is a sum of the basin geometry indices bgis which can be calculated for a separate cross section of the lake the distribution of processes within the basin was investigated in two selected floodplain lakes with the use of bgis field research was carried out in the bug river valley from 1 november 2006 to 31 october 2011 the highest erosion was observed in the lakes located close to the parent river deposition processes were observed in lakes with high inflow of groundwater the results showed that edi values of 48 out of the 71 floodplain lakes ranged from 0 2 to 0 2 spatial distribution of erosion and deposition processes within the lake basins resulted from a velocity of water inflowing or flowing through the basin this was observed especially in contrafluent confluent lake inflow of rivers water via upstream crevasse occurred later than via downstream one but energy of flowing water was higher which favoured erosion of this part of the lake basin copyright 2013 john wiley sons ltd

sediment budget to assess the geomorphic effect of a cyclonic storm new zealand abstract a short term sediment budget was constructed to assess the erosion response of a soft rock hill country watershed to an intense rainstorm event the watershed is located in a landslide prone area on the east coast of the north island new zealand during march 1988 753 mm of rain was recorded over a four day period with 320 mm and 329 mm on successive days known as cyclone bola this was the largest rainstorm event in the tutira watershed in the 93 year rainfall record the budget quantifies the total sediment generated during the storm the relative contribution of erosion processes involved the amount of sediment held in storage and the amount discharged into two lakes within the watershed a landform map of the watershed was constructed and the contribution of each landform type to the total budget was calculated a total of 1 35 0 13 million m3 of sediment was generated during the storm at an average of 420 m3 ha this is equivalent to a denudation value of 42 mm for the total watershed 3208 ha and 83 mm for the landforms severely affected by landsliding 1427 ha of the sediment generated 21 remained on hillslopes 22 was deposited on valley floors 51 was deposited on the lakebeds and the remaining 6 was discharged from the watershed via the lake outlet most of the sediment generated during the storm was from primary source areas on hill slopes with sediment in secondary storage providing only a small contribution landslide erosion was the main process accounting for 89 of the sediment generated channel tunnel gully and sheet erosion were only minor contributors to the budget six hillslope landforms which occupy only 44 of the watershed generated 90 of the sediment the results of this sediment budget when put in context with the storm magnitude frequency history being analysed from lake cores contribute to the identification of sustainable land use and management of soft rock hill country

observation of quasi 2 day convective disturbances in the equatorial indian ocean during dynamo abstractthis study examines the westward propagating convective disturbances with quasi 2 day intervals of occurrence identified over gan island in the central indian ocean from mid to late octobe

north south asymmetry of the high latitude thermospheric density imf by effect previous studies have established that the y component of the interplanetary magnetic field imf by plays a role in the north south asymmetry of the high latitude plasma convection and wind the effect of the positive negative imf by in the northern hemisphere resembles the effect that the negative positive imf by would have in the southern hemisphere in this study we demonstrate that the imf by effect can also contribute to the hemispheric asymmetry of the thermospheric density we use high accuracy air drag measurements from the challenging minisatellite payload champ satellite and supermag ae index during the period 2001 2006 to examine the response of the high latitude thermospheric density to geomagnetic activity our statistical analysis reveals that the density response at 400 km is greater in the southern hemisphere under positive imf by conditions and greater in the northern hemisphere under negative imf by conditions the results suggest that the imf by effect needs to be taken into account in upper atmospheric modeling for an accurate description of high latitude densities during periods of enhanced geomagnetic activity

organized convective systems in the tropical western pacific as a process in general circulation models a toga coare case study we examine the large scale effects of organized convective systems in the tropical western pacific observed during the tropical ocean global atmosphere coupled ocean atmosphere response experiment toga coare in a case study approach we examine realizations of a supercluster associated with the onset of the december 1992 westerly wind burst in the t213 operational medium range weather forecasting model of the european centre for medium range weather forecasts ecmwf we idealize a supercluster as a hierarchy of three interacting scales namely organized cumulonimbus c 1 mesoscale convective systems c 2 and the supercluster component c 3 it is shown that the ecmwf model represents this hierarchy as a c 3 like surrogate whose influence dominates the effect of parametrized convection this causes over prediction of the model tendencies which in the case of zonal momentum is explained in elementary terms the structure of the resolved scale momentum flux is explained by moncrieff s 1992 archetypal theory of organized convection which has been verified against observations and cloud resolving model data sets the parametrization of subgrid scale convective momentum flux in the ecmwf model based on a momentum mixing concept produces subgrid scale tendencies that are physically different from transports associated with cumulonimbus convection in a shear flow we outline a strategy for parametrizing the momentum flux by the c 1 component based on the archetypal model the c 2 component which is part resolved and part parametrized is at odds with the assumptions of scale separation underpinning parametrization it is argued that this component should be represented as part of the prognostic treatment of convectively generated cirrus finally we suggest cloud resolving modelling studies to further quantify the structure and large scale impact of superclusters in a westerly wind burst environment ranging from idealized models to models having data assimilation capability

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

modeling study of a tropical squall type convective line abstract a multidimensional and time dependent cloud scale model is used to investigate the dynamic and micro physical processes associated with convective and stratiform regions within a tropical squall type convective line the evolution of the total convective and stratiform portions of rainfall is also estimated by using model output a three dimensional version of the model covers a horizontal domain about 96 96 km2 frequently the horizontal extent of an observed stratiform region is over a few hundred kilometers therefore a two dimensional version of the model with a 512 km horizontal length is also used to incorporate a complete stratiform region two dimensional model result recapture many interesting features as observed in particular the fractional portion of stratiform rain as well as its fractional area coverage are in good agreement with observations a significant amount of ice particles melted to rain near the freezing level in the trailing part of the modeled squall system during i

sediment routing in a small drainage basin in the blast zone at mount st helens washington u s a abstract a quantitative description of the routing of 400 10 3 t km 2 of sediment delivered to a 2 4 km 2 basin by the may 18 1980 eruption of mount st helens has been developed for the period may 1980 june 1981 on hillslopes this sediment resided in primary and secondary remobilized primary storage sites hillslope erosion processes redistributed sediment on hillslopes and delivered sediment to the channel system these processes included shallow sliding from slopes steeper than 0 70 sheet erosion and rill erosion the most important discrete sites of storage on hillslopes were colluvial wedges and sites upslope of logs or other organic debris most tephra delivered to the basin by the eruptions is likely to be preserved in the stratigraphic record twelve percent of the sediment delivered to the study area was transported to the channel system directly by the eruption and by hillslope erosion processes of this approximately half remained in storage in the channel system and the remainder was exported from the drainage basin important sites of alluvial sediment storage included alluvial fans sites related to logs channel beds and alluvial terraces

frictional moisture convergence in a composite life cycle of the madden julian oscillation abstract a composite life cycle of the madden julian oscillation mjo is constructed using an index based on the first two eofs of the bandpass filtered 20 80 days 850 mb zonal wind averaged from 5 n to 5 s every 2 5 around the equator precipitation 1000 mb convergence 850 mb wind and 200 mb wind are composited for the period 1979 95 water vapor integrated from the surface to 300 mb is composited for the period 1988 92 frictional moisture convergence at the equator is shown to play an important role in the life cycle of the madden julian oscillation mjo regions of boundary layer convergence foster growth of positive water vapor anomalies to the east of convection this convergence coincides with 850 mb easterly wind anomalies as is consistent with kelvin wave dynamics drying of the atmosphere occurs rapidly after the passage of convection with the onset of 850 mb westerly perturbations possible mechanisms for this drying include boundary layer divergence and subsidence or horizontal advect

rill network development and sediment budgets threshold conditions for rill incision are well known but few studies have examined the effect of network geometry on water and sediment fluxes within an evolving rill system this paper reports the first in a series of studies designed to identify the influence of soil properties on rill network and confluence geometry and on water and sediment fluxes in rill systems the object of this study was to prepare detailed rill network water and sediment budgets identifying important sources and sinks simulated rainfall experiments were carried out on a canadian silt loam soil in a 7 1 m 2 4 m flume on a 5 slope rill networks of varying complexity developed which were ultimately constrained by flume boundaries sediment and water fluxes and hydraulic conditions were measured within networks and at a terminal weir networks evolved by initial knickpoint incision in the lower flume as flow shear velocities reached critical levels of 4 5 5 cm s 1 followed by headward migration and tributary development microtopography determined tributary location but the timing and intensity of development were controlled by the incision and migration rate of the main channel which changed local thalwegs and base levels raising shear velocities on side slopes above critical levels sediment discharge at the weir broadly reflected rill incision intensity and transport limited conditions but as active incision moved headward the linkage became attenuated and identification of discrete erosional incidents e g local bank collapse in the signal of the weir record became very difficult detailed water and sediment budgets showed much more complex patterns of localized incision and deposition within networks strongly influenced by local changes in thalweg and in water discharge due to seepage or return flow and by the effect of confluences on hydraulic conditions results indicate the value of detailed sediment budgets in interpreting weir water and sediment flux records and the necessity of linking such measurements for erosion plots and hillslope segments to rill network characterization experimental results are consistent with a simple model of rill system evolution based on channel incision headward migration and the critical shear velocities for rill initiation copyright 2000 john wiley sons ltd

effect of imf by on thermospheric composition at high and middle latitudes 1 numerical experiments 1 magnetic storms and their effects on the thermosphere and ionosphere have been studied for many years yet there are many aspects of the thermospheric and ionospheric responses that are not understood the purpose of this paper is to show how the high latitude composition depends on the sign of the imf by component using controlled simulations with a global first principles model because the high latitude convection and neutral wind systems are strongly controlled by the imf by component it seems likely that the compositional response that is driven by high latitude forcing should also be sensitive to the by component to date no first principles modeling has been performed to test the idea of imf by effects on composition numerical experiments using model simulations provide insight into this important scientific question since the thermospheric compositional response to the convection patterns for different imf bz and by can be studied in isolation in a model in this paper we use a first principles model to determine the effect of the imf by component on the compositional response of the high latitude thermosphere we show for the first time that a clockwise rotation of the potential pattern resulting from a change from by negative to by positive drives a corresponding rotation in the wind neutral density and composition distributions by control of thermospheric composition has been invoked in the literature to explain an apparent variability in the effectiveness of auroral activity in causing thermospheric storm effects at middle latitudes as observed in global images of the far ultraviolet fuv oi 130 4 nm emission from the de 1 auroral imager however the effect in the simulations presented here is opposite from that suggested by earlier work based on de data indicating another explanation must be sought for the de results these simulations are highly relevant for interpreting data being provided by more modern uv imaging instruments on the dmsp timed and image satellites

nonlinear zonal propagation of organized convection in the tropics abstracta wide range of the observed variability in the itcz is frequently explained in terms of equatorially trapped modes arising from matsuno s linear shallow water model here a series of zona

delivery of upper basin sediment to the lower neuse river north carolina u s a extensive storage of upper basin piedmont sediment and apparent low sediment supply to streams in lower basin coastal plain areas generates questions as to the source of alluvium in lower reaches of rivers of the u s atlantic drainage this was investigated on the neuse river north carolina using a mineralogical indicator of sediment source areas the utility of mica flakes for discriminating between piedmont and non piedmont sources of sediment in the lower coastal plain reaches of the neuse was established on the basis of an examination of the u s national soils database and of 26 soil surveys of the north carolina coastal plain from the neuse river estuary to 48 km upstream there are no mica flakes in floodplain soils or in river bank and channel shelf sediments mica flakes become more common upstream this suggests that a very small proportion of the sediment eroded in the piedmont portion of the watershed is delivered to the river mouth the small amounts which presumably do reach the lower coastal plain are so diluted by coastal plain derived alluvium that no piedmont origin can be discerned this demonstrates a dominantly coastal plain source and underscores the importance of storage and discontinuous transport in fluvial sediment systems more importantly results suggest that upper and lower basin sediment dynamics are not only non linearly related but may be virtually decoupled

interactions between upland catchment and lowland rivers an applied australian case study abstract persistent allegations have been made mainly by victorian farmers that channel and floodplain aggradation are occuring on the floodplain of the snowy river in victoris as a consequence of a accelaerated erosion of degraded agricultural land in parts of the new south wales upland catchment these claims prompted the victorian department of water resources to initiate geomorphological investigations involving reviews of historical evidence including the squential aerial photographs and a study of sediment sources based on environmental tracers a qualitative approach set within a sediment budget framework was adopted for data integration a detailed quantitative analysis being precluded by financial temporal and practical constrainsts no compelling evidence was found to support claims of recent channel aggradation in the downstream snowy river transfer of sediment eroded from catchment slopes in nsw to the lowland floodplain in victoria is indirect with some sediments stored temporarily in fans and floodplains within tributary catchments and in the snowy valley for long delay times storage and interbasin transfer of water as part of the snowy mountains scheme have affected sediment delivery the catchment upstream of lake jindabyne is effectively isolated by this large impoundment and sediment transport rates as far downstream as the delegate river junction appear to have significantly decreased as the result of the considerable reduction in discharge

genesis and evolution of hierarchical cloud clusters in a two dimensional cumulus resolving model abstract a two dimensional cloud ensemble model is integrated over a basin scale domain with prescribed sea surface temperature sst to study the formation and evolution of cloud clusters over a large scale warm pool neither a basic zonal flow is prescribed nor is a single perturbation initially given the results show that deep convective clouds appear in hierarchical clustered patterns and are limited to the area of warm sst above 28 c the most fundamental cloud cluster in the model has a horizontal scale of a few hundred kilometers in which new cumulus clouds are generated at the leading edge of a propagating surface cold air pool the gust front it may last for days and propagate for a long distance if the background flow is broad and persistent as is the case in the low level convergence zone of the sst induced background flow the largest hierarchical propagating cloud systems in the model have horizontal scales up to 3000 km and consist of up to four cloud clusters that are generally of gust

rates of surface processes on slopes slope retreat and denudation results taken from 270 publications on rates are summarized and collated with those from 149 publications reviewed previously young 1969 1974 the data are classified by major climatic zone normal or steep relief and consolidated or unconsolidated rocks representative rates and their ranges are given for soil creep solifluction surface wash solution chemical denudation rock weathering slope retreat cliff free face retreat marine cliff retreat and denudation the last being compared with representative rates of uplift solifluction is of the order of 10 times faster than soil creep but both cause only very slow ground loss solution is an important cause of ground loss for siliceous rocks on which it may be half as rapid as on limestones total denudation brought about mainly by surface wash reaches a maximum in the semi arid and probably also the tropical savanna zones acceleration of natural erosion rates by human activities ranges from 2 3 times with moderately intense land use to about 10 times with intensive land use and considerably higher still where there is recognized accelerated soil erosion where there is active uplift typical rates are of the order of 10 times faster than denudation although in some high steep mountain ranges these may approach equality

the de ploey erosional susceptibility model for catchments es abstract this article is based on an unpublished manuscript by the late prof dr jan de ploey it focusses on the erosional susceptibility of catchments in terms of total energy input by the meteorological factors water and wind e s model the form and the universal character of the basic expression of the erosional susceptibility are explained applications of the model are illustrated for different processes such as landsliding and debris flows gullying creep and rill interrill combinations characteristic e s values exist for these processes also e s values vary in regions with differing pedo botanical characteristics and land use the difference between e s values for single storm events and longer periods are related to the magnitude frequency distribution of erosive activities and allow in many cases an assessment of the age of erosion phenomena and an estimation of the recurrence period of extreme single events

late quaternary sediment budget in alluvial fan source basin systems in japan sediment budgets since the late glacial were constructed for five alluvial fan source basin systems in japan the late glacial and holocene sediment yield from each source area was estimated based on digital elevation data and the morphometric analyses of geomorphological maps in which all hillslopes and fluvial surfaces were classified late glacial and holocene sediment storage in each fan was calculated from stratigraphical data the results have revealed that the ratio of sediment storage in a fan to sediment supply is between ca 0 3 and 0 8 such high ratios of sediment storage over long time periods cast doubt on the previously proposed steady state theory of alluvial fan development the storage ratio decreases if fan sediments are removed by neighbouring large rivers the maximum storage ratio of 0 8 reflects the ratio of washload to total load for japanese mountain rivers 1997 john wiley sons ltd

eastward propagating 2 to 15 day equatorial convection and its relation to the tropical intraseasonal oscillation anomalies of outgoing longwave radiation olr in 1980 1989 were examined in a narrow latitude band about the equator to elucidate the propagation and interaction of tropical intraseasonal oscillations tios and synoptic scale convective activity hovmoller diagrams of olr data reconstructed from two frequency bands corresponding to periods of 30 60 days and 2 15 days respectively revealed a clear distinction between the phase speed of eastward moving tios 3 7 m s 1 and that of eastward synoptic scale convection 10 13 m s 1 coherent propagation of tios from the indian to the western pacific oceans was often observed with temporary diminution of amplitude over the maritime continent propagation of high frequency anomalies was generally confined to an individual basin dominance of eastward propagating synoptic scale convection in the equatorial zone contrasts sharply with the westward propagation of off equatorial convergence zones interaction between the tio and high frequency activity resolved by daily olr was visible as a modest enhancement of eastward synoptic scale events and of high frequency activity in general during the convectively active phase of the tio

observations of a super cloud cluster accompanied by synoptic scale eastward propagating precipitating systems over the indian ocean the multiscale structure of a super cloud cluster scc over the equatorial indian ocean observed in november and december 2006 was investigated using data from satellite microwave sensors and surfacebased radars the smaller scale structure of this scc was marked by a complicated relationship between rainfall systems and upper tropospheric cloud shields which moved eastward and westward respectively with a cycle of 2 4 days in the analyses attention was given to the structure of slow eastward propagating 5 11 m s 21 precipitating systems and related synoptic scale 2000 km disturbances a case study of one of the systems revealed that it consisted of several lines of convective cells with a depth that was usually shallower than 10 km unless the cells encountered the westward moving cloud shields the environment of the convective lines was characterized by persistent unstable conditions with an increase of the westerly flow in the lower troposphere suggesting the existence of a synoptic scale upward motion composite analyses revealed that each rainfall system formed in a region of zonal flow convergence near the surface and divergence near 300 hpa the vertical temperature structure tilted westward with height below this pressure level and eastward aloft similar to that of a convectively coupled kelvin wave these results suggest that a scc involves a group of synoptic scale shallow waves propagating eastward an additional analysis over the western pacific also showed the predominance of eastward propagation in a scc demonstrating the advantage of satellite microwave sensors over infrared ones in monitoring the multiscale structure of tropical convection

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

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

paired geochemical tracing and load monitoring analysis for identifying sediment sources in a large catchment draining into the great barrier reef lagoon while sediment tracing has been typically applied to identify sediment sources that are difficult to measure by gauging monitoring it can also be useful in estimating relative sediment yields from gauged river catchments the major and trace element composition of river sediments from eleven locations in the 130000 km2 burdekin river catchment northeastern australia was analysed to examine relative contributions from upstream source areas in the 2011 12water year sediment tracing results are compared against estimates derived fromsediment load monitoring at three locations comparisons show that there is good agreement between tracing results and monitoring data at one of the tributary confluences at the second site notable contrastswere found between the load estimates from the monitoring and tracing data at this site a large impoundment occurs between the upstream sampling gauging sites for source sediments and the downstream sampling gauging sites for target sediments the contrast is likely caused by temporal variations in particle size distributions of suspended sediment fromeach river and differential trapping efficiencies in the impoundment for sediment derived fromthe different tributaries in the absence of the detailed particle size data and trapping efficiency estimates sediment tracing provides the unique opportunity to elucidate source contributions of the finer fractions of suspended sediment at a third site where there were recognised measurement gaps in the monitoring data during large discharge events the relative load estimates fromthe tracing data provided a means of constraining the recognized uncertainty of monitored load estimates we conclude that sediment tracing can be used as a valuable adjunct to monitoring data particularly in remote large and data sparse catchments both tracing results and monitoring data showthat the upper burdekin river and bowen bogie riverswere the dominant source of the b10 m sediments being delivered to the gbr lagoon from the burdekin river catchment in the 2011 12 water year more substantial contribution from the belyando suttor rivers indicated by the tracing results than the monitoring data is attributed to preferential delivery of the 1 10 m sediments through the impoundment and has uncovered a knowledge gap in sediment budgets in the catchment

observations of cloud cluster hierarchies over the tropical western pacific infrared radiance measurements at cloud top by the japanese geostationary meteorological satellite gms were used to study the structure and propagation of tropical convective systems over the equatorial western pacific results indicate that tropical convection in this region possesses three fundamental periodicities 1 day 2 3 days and 10 15 days cloud clusters within these convective systems interact to produce a hierarchy of collective motions covering all of these three basic time scales the 10 to 15 day time scale is closely related to the intraseasonal or 30 60 day oscillations that propagate from the indian ocean to the western pacific along the equator all year round large convective complexes known as supercloud clusters scc are found to organize in the 10 to 15 day time scale especially over the open warm water of the western central pacific 160 e to 180 the sccs generally propagate eastward although occasionally they can also propagate westward the zonal propagation can occur either continuously or intermittently in both cases the scc is found to be made up of several well organized cloud clusters which are generated at 2 to 3 day intervals and propagate in the opposite direction to the scc the diurnal variation is most pronounced over the maritime continent although significant amplitudes are also found over the open ocean the amplitude of the diurnal cycle is strongly modulated by the 2 to 3 day and 10 to 15 day oscillations advanced spectral analysis methods applied to convective indices derived from the radiance data confirm this hierarchical structure in cloud clusters in the tropical western pacific in addition to the embedding of well organized clusters within a scc in the spatial domain there is also a similar embedding by successive longer scales in the time domain interactions between the major frequency groups appear also to give rise to intermediate frequency variations a discussion of the present results in the context of equatorial wave dynamics of the moist tropical atmosphere is also presented