answer to comments on space time structure of monsoon interannual variability the conceptual model proposed by khandekar aims at explaining the occurrence of good or bad indian summer monsoons ism he argues that good or bad monsoon years can be explained by three independent factors el nino southern oscillation enso eurasian snow cover and the stratospheric wind quasi biennial oscillation qbo on the other hand the results in my paper terray 1995 suggest that ism interannual variability is dominated by two low frequency modes the biennial b mode with a period very close to 2 yr and the lowfrequency lf mode with a period close to 4 6 yr the lf mode contains more energy than the b mode but the ocean atmosphere coupling seems to be stronger at the b timescale over the indian ocean finally the occurrence and intensity of exceptional isms depend upon the coupling or the decoupling of the b and lf modes during recent decades it is true that khandekar s model for drought and flood in the indian monsoon has some connections with my results and can be among others a working hypothesis for explaining them however there are still some issues that need to be clarified in khandekar s model from my point of view

global climatic anomalies associated with extremes in the southern oscillation abstract composite temperature and precipitation anomalies during various stages of an event in the southern oscillation so have been computed for several hundred stations across the globe large regions of coherent significant signals are shown to exist for both extremes of the so with warm event signals generally opposite to those during cold events in addition during the year preceding the development of an event in the so year 1 climatic anomalies tend to be opposite to those during the following year year 0 this confirms that the biennial tendency of the so over the pacific indian ocean sectors is also present in more remote regions with climatic signals related to the so many of the signals are consistent enough from event to event to be useful for extended range forecasting purposes

extended eliassen palm fluxes associated with the madden julian oscillation in the stratosphere 1 links are sought between madden julian oscillation mjo related variations in the troposphere and stratospheric circulation tropospheric variations of equatorial mjo filtered 200 hpa zonal winds define indices of mjo activity for two equatorial regions in the indian and western pacific oceans these indices are used to define composite means of mjo filtered extended eliassen palm e p fluxes for eight height levels from the upper troposphere well into the stratosphere evidence is presented for significant and coherent mjo departures throughout the lower stratosphere significant departures of the vertical component of e p flux flow into the lower stratosphere both in the tropics and at higher latitudes especially over canada these are accompanied by horizontal flux departures in the upper troposphere and lower stratosphere from the central tropical pacific into northern canada in this region there is a divergence of extended e p flux piling up wave energy leading to the observed increased cyclonic motion evidence supports the hypothesis that these high latitude circulation variations in the stratosphere are due to a combination of two quite distinct mechanisms in the first poleward propagation occurs in the upper troposphere with vertical propagation at higher latitudes in the second upward propagation occurs in low latitudes into the lower stratosphere this is followed by poleward propagation into higher latitudes and then farther upward propagation

zonal and vertical structure of the madden julian oscillation abstract a statistical study of the three dimensional structure of the madden julian oscillation mjo is carried out by projecting dynamical fields from reanalysis and radiosonde data onto space time filtered outgoing longwave radiation olr data mjo convection is generally preceded by low level convergence and upward motion in the lower troposphere while subsidence cooling and drying prevail aloft this leads to moistening of the boundary layer and the development of shallow convection followed by a gradual and then more rapid lofting of moisture into the middle troposphere at the onset of deep convection after the passage of the heaviest rainfall a westerly wind burst region is accompanied by stratiform precipitation where lower tropospheric subsidence and drying coincide with continuing upper tropospheric upward motion the evolution of the heating field leads to a temperature structure that favors the growth of the mjo the analysis also reveals distinct differences in the vertical structure

two dimensional water flood and mudflow simulation flo 2d is a two dimensional finite difference model that simulates clear water flood hazards mudflows and debris flows on alluvial fans and urban floodplains interactive flood or mudflow routing between channel street and floodplain flow is performed using a uniform grid system to describe complex floodplain topography a quadratic rheological model developed from field and laboratory mudflow data enables appropriate simulations of flooding conditions ranging from clear water to hyperconcentrated sediment flows computer aided design cad graphics of predicted time sequenced flood depths automates the delineation of flood hazards replication of the 1983 rudd creek mudflow in utah demonstrates the capability of the model

velocity of debris flow determined by grain composition abstractvelocity is one of the most important parameters of debris flows and it is usually calculated using manning formula in hydraulics mostly ignoring the granular effects due to flow material

the tropical extratropical interaction between high frequency transients and the madden julian oscillation abstract the interaction between high frequency transient disturbances and convection and the madden julian oscillation mjo is investigated using ncep ncar reanalysis and satellite outgoing longwave radiation data for 15 northern winters during the phase of the mjo with enhanced convection over the east indian ocean and indonesia and suppressed convection over the south pacific convergence zone both the asian pacific jet and the region of upper tropospheric tropical easterlies over the warm pool are displaced westward these changes in the basic state lead to a weaker or leakier waveguide in the asian pacific jet with a westward displaced forbidden region of tropical easterlies such that high frequency transient waves propagate equatorward into the deep tropics over the central pacific near the date line as these waves induce convection in the region of ascent and reduced static stability ahead of the upper level cyclonic disturbances there is an enhancement of high frequency convective var

the southern oscillation part ix the influence of volcanic eruptions on the southern oscillation in the stratosphere abstract the signal in the winter stratosphere on the northern hemisphere of a warm event in the southern oscillation is a warm polar vortex with a weak westerly circulation this signal failed to appear in two warm events which took place at the time of the eruptions of agung and el chichon we propose that the volcanic emissions affected the development of the warm events in the stratosphere and support this argument by reference to a sensitivity experiment made by m blackmon this experiment used the observed global anomalies of sea surface temperature in december january february 1982 83 but did not consider volcanic aerosols and gasses ejected by el chichon in 1982 the response of the model stratosphere in the experiment resembled the observed signal of the southern oscillation in other years

the influence of the 1997 99 el niňo southern oscillation on extratropical baroclinic life cycles over the eastern north pacific the el nino southern oscillation enso strongly influences the interannual and seasonal atmospheric circulation over the north pacific the present study shows that the meridional displacement of the time mean upper level jet associated with enso modulates the time mean barotropic meridional wind shear over the central and eastern north pacific storm track earlier theoretical and observational studies established the influence of barotropic wind shear on the life cycles of extratropical cyclones and their upper level potential vorticity pv waves the present study suggests that differences in the time mean flow associated with the 1997 99 enso cycle had a similar impact on tropopause pv structure meridional eddy fluxes of momentum and temperature and predictability

the development of upper tropospheric wind over the western hemisphere in association with mjo convective initiation abstractthis study examines the structure and driving mechanisms of upper tropospheric intraseasonal zonal wind anomalies over the western hemisphere wh during the convective initiation of the madden julian oscillation mjo over the indian ocean using composite and budget analyses the initiating mjo convection is more often associated with wh upper tropospheric intraseasonal easterly wind anomalies and when it is it tends to develop a stronger and zonally broader envelope of enhanced convection than events associated with westerly wind anomalies the wh upper tropospheric zonal wind anomaly associated with the mjo is often described as a dry kelvin wave radiated from mjo convection but the results show that both the structure and driving mechanisms are different from the ones of theoretical kelvin waves unlike the theoretical kelvin wave the zonal wind anomaly is not driven mainly by the zonal pressure gradient force and it is strongly coupled with rotational wind associated with subtropical and

intraseasonal temperature variability in the upper troposphere and lower stratosphere from the gps radio occultation measurements 1 in this study we examine the detailed spatiotemporal patterns and vertical structure of the intraseasonal temperature variability in the upper troposphere and lower stratosphere utls associated with the madden julian oscillation mjo using the temperature profiles from the recent global positioning system radio occultation gps ro measurements including the constellation observing system for meteorology ionosphere and climate cosmic mission the mjo related temperature anomalies in the utls are smaller near the equator 1 2 k near the equator the temperature anomalies exhibit an eastward tilt with height from the upper troposphere ut to the lower stratosphere ls and their magnitudes and signs are determined by the strength of convective anomalies and vertical pressure level the subtropical temperature anomalies have similar magnitudes and patterns at a given location between the ut 250 hpa to 150 hpa and the ls 150 hpa to 50 hpa except for opposite signs that change around 150 hpa the subtropical warm cold anomalies in the ut and cold warm anomalies in the ls are typically collocated with the subtropical positive negative tropopause height anomalies cyclones anticyclones and flank or lie to the west of equatorial enhanced suppressed convection we also compare the intraseasonal temperature variability in the utls related to the mjo between the gps ro and atmospheric infrared sounder airs measurements to highlight the new features of the gps ro temperature anomalies and to evaluate the quality of the airs temperature in the utls considering the gps ro temperature in the utls as the benchmark both airs and gps ro have a very consistent vertical structure in the subtropical utls with a high correlation coefficient 0 92 and similar magnitudes both airs and gps ro also show a generally consistent vertical structure of the intraseasonal temperature anomalies in the equatorial utls however gps ro reveals many detailed fine scale vertical structures of the equatorial temperature anomalies between 150 and 50 hpa that are not well captured by airs furthermore the equatorial temperature anomalies are about 40 underestimated in airs in comparison to gps ro over the equatorial indian and western pacific oceans for 250 hpa and over all longitudes for 100 hpa the low sampling within the optically thick clouds and low vertical resolution near the tropopause may both contribute to these deficiencies of airs

northern hemisphere mid winter vortex displacement and vortex split stratospheric sudden warmings influence of the madden julian oscillation and quasi biennial oscillation we investigate the connection between the equatorial madden julian oscillation mjo and different types of the northern hemisphere mid winter major stratospheric sudden warmings ssws i e vortex displacement and vortex split ssws the mjo ssw relationship for vortex split ssws is stronger than that for vortex displacement ssws as a result of the stronger and more coherent eastward propagating mjos before vortex split ssws than those before vortex displacement ssws composite analysis indicates that both the intensity and propagation features of mjo may influence the mjo related circulation pattern at high latitudes and the type of ssws a pronounced quasi biennial oscillation qbo dependence is found for vortex displacement and vortex split ssws with vortex displacement split ssws occurring preferentially in easterly westerly qbo phases the lagged composites suggest that the mjo related anomalies in the arctic are very likely initiated when the mjo related convection is active over the equatorial indian ocean around the mjo phase 3 further analysis suggests that the qbo may modulate the mjo related wave disturbances via its influence on the upper tropospheric subtropical jet as a result the mjo related circulation pattern in the arctic tends to be wave number one wave number two 25 30 days following phase 3 i e approximately phases 7 8 when the mjo related convection is active over the western pacific during easterly westerly qbo phases which resembles the circulation pattern associated with vortex displacement vortex split ssws

a comparison of reanalyses in the tropical stratosphere part 2 the quasi biennial oscillation reanalysis datasets potentially offer the opportunity to examine the tropical quasi biennial oscillation qbo in greater detail than in the past including the associated meridional circulation and the links with other parts of the atmosphere for such studies to be useful the qbo represented by the reanalyses should be realistic in this work the qbo in the era and ncep reanalyses is validated against rawinsonde observations from singapore monthly mean data are used in the lower stratosphere at 50 hpa and 30 hpa the era qbo is reasonable although the wind extrema in both phases are too weak and the vertical shear and the temperature anomalies are too small the ncep qbo is weaker still at 10 hpa neither reanalysis system performs well both systems failing to reproduce the westerlies possibly because of the proximity of the upper boundary the singapore wind is representative of the zonal means in the reanalyses the weak wind extrema in the reanalyses would not support a wave mean flow interaction theory of the qbo because a large portion of the gravity wave spectrum which would be absorbed in reality would be transmitted beyond 10 hpa the stronger shear zones captured in the era data are associated with larger more realistic temperature perturbations near 30 hpa the northward velocities in the ncep data show a more realistic structure than in the era reanalysis where they are dominated by a vertical gridpoint wave structure in the lowermost stratosphere despite the shortcomings of the reanalyses the high correlations of the wind at 30 hpa and 50 hpa with the observations at singapore mean that the reanalyses could potentially be used to examine the effects of the qbo away from the tropical stratosphere future reanalyses need to take full account of the wind shears evident in the rawinsonde observations and use models with an adequate resolution to capture these vertical scales

relationships among the stratospheric and tropospheric zonal flows and the southern oscillation abstract relationships among the high latitude stratospheric zonal wind the tropospheric zonal wind in the region of the subtropical jet and over the equator the southern oscillation and the stratospheric tropical quasi biennial oscillation qbo were examined from monthly anomaly data for 13 years 1968 80 patterns of correlation wore found which are broadly consistent with the theory on vertical and latitudinal rossby wave propagation with high correlations diminishing rapidly in association with easterly basic flow lag correlations as high as 0 8 0 9 were found for leads of 1 7 months based on three month average anomalies for successive months the simplified lead path is from southern oscillation to equatorial winds to subtropical winds to stratospheric high latitude winds relationships involving the qbo appear weak compared to those involving the extratropical flows the tropospheric equatorial flow of the east pacific and the southern oscillation even so the structure of correlation fo

the southern oscillation part v the anomalies in the lower stratosphere of the northern hemisphere in winter and a comparison with the quasi biennial oscillation abstract the mean anomalies of 50 mb height in the northern winter for seven warm events in the southern oscillation show a weak polar vortex and an enhanced aleutian high in the mean for six cold events the polar vortex is unusually strong and the aleutian high is weakened and displaced far to the southwest these anomalies are consistent with the corresponding anomalies in sea level pressure pattern the warm events of 1963 and 1982 did not fit this pattern as in both years the polar vortex was cold and intense these events happened in years when volcanoes injected large amounts of gases and aerosols into the stratosphere and the temperature of the tropical stratosphere became unusually high in other warm events the temperature of the tropical stratosphere was abnormally low the mean anomalies of the quasi biennial oscillation for the winter as a whole west minus east phase computed from years with no cold or warm events are zonally symmetrical and shaped as four concentric regions with alternatin

characteristics of kelvin waves and gravity waves observed with radiosondes over indonesia profiles of wind velocity and temperature at 0 35 km were observed by means of radiosondes in west java indonesia during november 1992 and april 1993 and used to study the behavior of various atmospheric waves in the equatorial atmosphere an oscillation of zonal winds with a period of about 27 days was found in the troposphere which was associated with variations in humidity and cloud top height kelvin waves showed phase progression beginning at cloud top height 13 16 km and were particularly enhanced near the tropopause the kelvin waves strongly modulated the tropopause structure including the tropopause height minimum temperature and atmospheric stability a hodograph analysis was applied to determine the propagation characteristics of inertial gravity waves height variation of the vertical group velocity suggests that the gravity waves were generated in the troposphere while the horizontal phase velocity distribution suggests that they were interacting with the background mean zonal winds these wave activities were enhanced when tall convective clouds passed over the site suggesting that cumulus convection seems to play a key role in generating these waves in the equatorial region

aspects of interannual and intraseasonal variability of the tropopause and lower stratosphere radiosonde and national centers for environmental prediction national center for atmospheric research reanalysis data are utilized to consider aspects of large scale variability in tropopause height temperature and pressure this variability is related to coherent dynamical fluctuations in the troposphere and lower stratosphere through the use of linear correlation and regression on interannual time scales significant global scale tropopause fluctuations are tied to variability in sea surface temperature sst associated with the el ni o southern oscillation phenomenon when sst is anomalously high in the central tropical pacific tropopause height pressure is high low throughout the tropics with largest perturbation amplitudes in the subtropical pacific at the same time the tropopause is cold over the tropical and subtropical pacific sector but warm elsewhere in the tropics over the extratropics wave like perturbations in the tropopause are seen with anomalous cyclonic flow corresponding to a lower tropopause height and higher tropopause temperature and pressure and vice versa the sign of the temperature anomalies in the lower stratosphere tends to match that at the tropopause over much of the globe with opposite signed anomalies in the upper troposphere the vertical structure of these perturbations is consistent with the expected potential vorticity anomalies induced by quasi stationary rossby waves and vertically propagating gravity waves forced by displacements of tropical convection similar relationships are associated with the eastward propprotion of tropical convection due to the madden julian oscillation on intraseasonal time scales

the signature of enso in global temperature and precipitation fields derived from the microwave sounding unit abstract global temperature anomalies associated with enso are investigated making use of a 13 year record of gridded temperature and precipitation data from the microwave sounding unit msu the warm phase of the enso cycle during this period was characterized by an overall warming of the tropical troposphere superimposed upon a distinctive equatorially symmetric dumbbell shaped pattern straddling the equator near 140 w accompanied by negative anomalies along the equator over the western pacific by means of singular value decomposition svd analysis it is shown that this pattern fluctuated in phase with the displacements of convective activity over the equatorial pacific as reflected in the anomalies in outgoing longwave radiation olr and msu precipitation fields fluctuations in mean tropical tropospheric temperature lagged the olr anomalies and the related temperature pattern by about 3 months the same dumbbell shaped pattern was evident with reversed polarity in the lower stratosphere tog

effect of bed sediment entrainment on debris flow resistance entrainment of sediment from hillslope and channel usually has a significant influence on resistance of debris flow this effect is studied by flume experiments of debris flow over rigid and erodible beds fifty contrast flume tests show that the flow resistance over the erodible bed is significantly larger than that over the rigid bed because of higher energy consumption resulting from sediment transport a new formula of debris flow resistance involving the entrainment effect is obtained from the erodible bed data by nondimensional multiple regression analysis

a possible influence of the tropical quasi biennial oscillation on the variability of the extratropical circulation in the southern hemisphere 1 this study uses geopotential heights and zonal winds from the ncar ncep reanalysis and the naujokat tropical stratospheric zonal wind data set to evaluate the suggestion that the tropical quasi biennial oscillation qbo influenced the observed amplitude increase in zonal harmonic wave 1 in the southern hemisphere winter after 1975 fourier analysis was used to extract zonal wave 1 zw1 from the geopotential heights zw1 and the zonal winds were stratified by qbo phase and compared to those composited for years before and after 1975 the comparisons confirm that zw1 during the easterly phase of the qbo is larger than zw1 during the westerly phase the comparisons also suggest that the growth in zw1 seen after 1975 took place preferentially during winters with an easterly tropical qbo and weak stratospheric winds the change in zw1 is associated with surface level changes over the pacific and simultaneous upper level support by the easterly phase tropical qbo

influence of flow width on mean velocity of debris flows in wide open channel debris flow in a wide open downstream channel has a significant transverse velocity component that strongly influences its mean longitudinal velocity investigation of observation data of debris flow surges at jiangjia ravine in china shows the dependency of manning resistance of debris flows on the ratio of flow width to depth regression fit reveals a power function relationship between the manning resistance coefficient and the width to depth ratio this derives a new formula of mean velocity incorporating the influence of flow width the result indicates that the width to depth ratio can be viewed as a kind of shape roughness analogous to grain roughness in the darcy weisbach resistance coefficient expression doi 10 1061 asce hy 1943 7900 0000648 c 2013 american society of civil engineers

experimental study on gully shaped mud flow in the loess area vast expanse of land in northwest china is covered by loess because of the characteristics of loess mud flow disasters can be induced in this area easily worse still due to the mud flow gully transformation and the environmental changes in recent decades mud flow disasters are increasing in order to know more about gully shaped mud flow the field investigation of more than 60 gullies and the similarity principle were applied to determine the test parameters and a physical model of gully was made for mud flow during the tests the motion characteristics velocity acceleration and intermittent debris flow and deposition parameters length width area aspect ratio distribution shape and thickness of mud flow in the model were collected and analyzed the instantaneous velocities of the mud flow fluctuated discharge exerts a maximum impact on the velocity second is unit weight and minimum slope angle in the transportation zone the mud flow flows and forms the bed firstly then the intermittent debris flow occurs which is affected by discharge and unit weight the length width and area of deposition have a certain linear rule and distribution pattern greatly relates to the first accumulation the stacking thickness is decreasing from the center to the edge

horizontal structure and seasonality of large scale circulations associated with submonthly tropical convection the relationship between deep tropical convection and large scale atmospheric circulation in the 6 30 day period range is examined regression relationships between filtered outgoing longwave radiation at various locations in the tropics and 200 and 850 mb circulation are mapped for the standard seasons and the spatial structure and seasonal dependence of the results are interpreted in view of the basic state circulation in regions where the convection is embedded in upper level easterlies anomalous equatorial easterly flow is typically present at 200 mb within and to the west of the convective signal along with patterns of meridional outflow into subtropical anticyclonic perturbations lagged relationships suggest that the convection is forcing the circulation in many of these cases the outflow and subtropical circulations are strongest into the winter hemisphere during the solstitial seasons with more symmetric signals about the equator seen in the equinoctial seasons the longitudinal positioning of the subtropical features with respect to the convection varies but is generally located due poleward or just to the east of the convection there tends to be a first baroclinic mode vertical structure to these circulations such that equatorial westerlies are present at 850 mb within the convection with closed circulations on either side of the equator resembling equatorial rossby modes especially common over the atlantic and pacific sectors as a contrast in regions located within upper level westerlies or along the margin of influence of upper westerly disturbances convection appears to be forced by upper level wave energy propagating into the deep tropics with the heating located in the upward motion region ahead of upper level troughs this occurs over the atlantic and eastern pacific sectors during northern winter and spring and over australia the south pacific and south america during southern summer when upper westerlies are at relatively low latitudes where they can interact with deep tropical convection the results confirm theoretical and modeling ideas that suggest that rossby wave energy is able to propagate into the deep tropics in regions where upper level westerlies exist in the tropics

the global range of the stratospheric decadal wave part i its association with the sunspot cycle in summer and in the annual mean and with the troposphere abstract the authors correlate the 23 yr series of reanalyzed 30 hpa heights and temperatures and 10 hpa heights with the 11 yr solar cycle for the summers of both hemispheres and for the annual mean the size and spatial pattern of the correlations in the northern hemisphere are the same as those of the correlations computed with a nearly twice as long series from the freie universitat berlin a belt of correlations that encircles the hemisphere in the outer tropics subtropics the correlation pattern is similar in the southern hemisphere the spatial distribution of correlations between 30 hpa temperatures and the solar cycle has the same configuration as the height correlations with the cycle the largest temperature correlations move with the sun from one summer hemisphere to the other the first eigenvector in a principal component analysis of the 30 hpa heights in summer and in the annual mean has the same shape as the above mentioned pattern in the correlations between the stratospheric data and th

upper regime plane bed the analysis of a laboratory and field data set for sand bed channels defines the characteristics of upper regime plane bed with sediment transport the occurrence of upper regime plane bed relates to the laminar sublayer thickness and depends on shear velocity u median grain size d50 and grain shear reynolds number r two different boundary conditions are recognized 1 transition to hydraulically smooth when r 11 6 in the first case upper regime plane bed is obtained when u 2 g where g is the gravitational acceleration in the second case upper regime plane bed is observed when d50 2 temperature effects are possible when r approaches 11 6 which explains the observations on the missouri river resistance to flow for plane bed with sediment transport increases with the shields parameter

development characteristics and dynamic structure of tropical intraseasonal convection anomalies abstract the development and dynamical structure of intraseasonal low frequency convection anomalies in the equatorial region are investigated using 10 years 1975 85 of outgoing longwave radiation olr and 7 years 1979 85 of 200 and 850 mb wind data the composite olr anomalies for 36 cases show a four stage development process initiation over equatorial africa rapid intensification when passing through the indian ocean mature evolution characterized by a weakening in the maritime continent and redevelopment over the western pacific and dissipation near the date line in moderate events or emanation from the equator toward north america and southeastern pacific in strong events a noticeable feature in vertical structure is that the 850 mb convergence leads convection and midtropospheric upward motion by about 30 degrees longitude in both developing and mature phases equatorial upper lower level easterly westerly anomalies and associated twin anomalous anticyclonic cyclonic circulation an

mean velocity of mudflows and debris flows models to predict mudflow and debris flow velocities are tested with 350 field and laboratory measurements overall the turbulent model performs best while the dispersive stress approach only compares well with the measurements when the flow depth h is less than 50 times the median particle diameter d50 the analysis of field measurements shows that the ratio of mean flow velocity v to shear velocity u is approximately 10 rarely exceeds 30 and increases slightly with relative submergence h d50 the best overall agreement with laboratory and field velocity measurements is obtained with v 5 75 u log h d50

the tropical tropopause and the el nino of 1982 1983 an earlier study of the behavior of the tropical tropopause during 1982 is extended through 1984 the earlier study focused on the influence of the el chichon volcanic eruption but it also considered the influence of the 1982 1983 el nino event during its onset phase in the latter half of 1982 here we present anomalies of tropopause height tropopause potential temperature and lower stratospheric potential temperature through 1984 these anomalies clearly show a much warmer than normal tropopause potential temperature over the western tropical pacific associated with el nino the abnormally warm tropopause potential temperature which was evident in late 1982 reaches a peak in early 1983 and continues abnormally warm until about october 1983 during this period the tropopause is also abnormally high but the lower stratospheric potential temperature is near normal

detection and analysis of lnapl using the instantaneous amplitude and frequency of ground penetrating radar data this paper reports the results of using the ground penetrating radar gpr method to detect light non aqueous phase liquids lnapl floating on the water table in an area where the thickness of lnapl present ranges from a few centimetres to several decimetres to understand the gpr response in this context gpr theoretical models are calculated using information from the literature and hydrogeological field data the study revealed that in the case of lnapl floating on the water table in a static condition there is an increase in the reflection amplitude from the water table due to the decrease in the capillary fringe nevertheless the amplitude of reflection from the water table can discriminate the contaminated from the non contaminated zone apart from an analysis of the real traces the analysis of some attributes of the complex trace instantaneous amplitude phase and frequency are also good tools to detect hydrocarbons floating on the water table such attributes depending on both the signal frequency and the hydrocarbon thickness can also give information about the thickness of the hydrocarbon layer it is concluded that analysing the lateral variations in signal amplitude of the real trace and in the amplitude phase and instantaneous frequency of the complex signal permits the delimiting of the area polluted by the hydrocarbon

initiation and flow behavior of the 1980 pine creek and muddy river lahars mount st helens washington two large high velocity lahars volcanic debris flows were triggered by a pyroclastic surge during the first few minutes of the may 18 1980 eruption of mount st helens the initial surge cloud evolved progressively by gravity segregation from a gas mobilized highly inflated density flow to a dense water mobilized basal debris flow lahar and accompanying ash cloud as it flowed down the east flank of the volcano the main source of the water for the lahars was probably from eroded snow and ice incorporated into the flow by turbulent mixing but ground water expelled together with the rock debris by the initiating volcanic explosions also may have contributed peak lahar discharge from the pine muddy fan upper smith creek and ape canyon probably exceeded 250 000 m 3 s initially but decreased exponentially in the downstream direction total volume of the lahars was in excess of 1 4 10 7 m 3 initial peak flow velocities in excess of 30 m s also decreased markedly downstream where flow was not impeded velocity was strongly related to the depth slope term r 2 3 s 1 2 from the manning uniform flow equation as a power law function during much of the route traveled lahar flow appears to have been supercritical deposits left in channels were generally thin relative to flow depth 0 to 2 5 m particles up to small boulder size were randomly distributed in the poorly sorted nonstratified matrix indicating complete suspension in a fully developed debris flow slurry however much larger clasts were transported as bed load computed sediment concentrations of matrix slurry samples ranged from 84 to 91 solids by weight and were similar for the two lahars two indirect methods for computing peak flow velocity previously only tentatively applied to debris flows were tested for accuracy by comparing computed lahar arrival times with recorded arrival times at swift reservoir the computed velocities appear to be 15 slower than the recorded velocities which is consistent with the restriction that the velocity formulas produce only minimum values

ground penetrating radar for high resolution mapping of soil and rock stratigraphy ground penetrating radar is a technique which offers a new way of viewing shallow soil and rock conditions the need to better understanding overburden conditions for activities such as geochemical sampling geotechnical investigations and placer exploration as well as the factors controlling groundwater flow has generated an increasing demand for techniques which can image the subsurface with higher resolution than previously possible the areas of application for ground penetrating radar are diverse the method has been used successfully to map ice thickness water depth in lakes bedrock depth soil stratigraphy and water table depth it is also used to delineate rock fabric detect voids and identify karst features the effective application of the radar for the high resolution definition of soil stratigraphy and fractures in bedrock is highlighted the basic principles and practices involved in acquiring high quality radar data in the field are illustrated by selected case histories one example demonstrates how radar has been used to map the bedrock and delineate soil horizons to a depth of more than 20 m two case histories show how radar has been used to map fractures and changes of rock type to 40 m range from inside a mine another case history demonstrates how radar has also been used to detect and map the extent of groundwater contamination the corroboration of the radar results by borehole investigations demonstrates the power and utility of the high resolution radar method as an aid for interpolation and extrapolation of the information obtained with conventional coring programmes with the advent of new instrumentation and field procedures the routine application of the radar method is becoming economically viable and the method will see expanded use in the future

the generation of global rotational flow by steady idealized tropical divergence abstract tropical convective heating is balanced on the large scale by the adiabatic cooling of ascent the horizontal divergence of the wind above this heating may be viewed as driving the upper tropospheric rotational wind field a vorticity equation model is used to diagnose this relationship it is shown that because of the advection of vorticity by the divergent component of the flow the rossby wave source can be very different from the simple fd source often used in particular an equatorial region of divergence situated in easterly winds can lead to a rossby wave source in the subtropical westerlies where it is extremely effective this part of the source can be relatively insensitive to the longitudinal position of the equatorial divergence a divergence field which is asymmetric about the equator can lead to a quite symmetric rossby wave source for a steady frictionless flow the rossby wave source averaged over regions within closed streamfunction or absolute vorticity contours is under cert

intraseasonal behavior of clouds temperature and motion in the tropics abstract the spectral character of tropical convection is investigated in an 11 yr record of outgoing longwave radiation from the advanced very high resolution radiometer to identify interaction with the tropical circulation along the equator in the eastern hemisphere the space time spectrum of convection possesses a broad peak at wave numbers 1 3 and eastward periods of 35 95 days significantly broader than the dynamical signal of the madden julian oscillation mjo this quasi discrete convective signal is associated with a large scale anomaly that propagates across and modulates time mean or climatological convection over the equatorial indian ocean and western pacific outside that region the convective signal is small even though under amplified conditions coherence can be found east of the date line and in the subtropics having a zonal scale of approximately wavenumber 2 anomalous convection propagates eastward at some 5 m s 1 and suppresses as well as reinforces climatological convection

space time variability of equatorial kelvin waves and intraseasonal oscillations around the tropical tropopause 1 using the ecmwf 40 year reanalysis data large scale variations of temperature and zonal wind around the tropical tropopause are investigated from the space time spectral analysis two dominant spectral regions in the eastward propagating domain are found one for kelvin waves and the other for intraseasonal oscillations isos to investigate activities of kelvin waves and isos we reconstructed the grid data for the two spectral windows and calculated the square amplitude at each grid point kelvin wave activities in zonal wind are vigorous during two seasons around february and july in the upper troposphere up to 100 hpa however the longitudinal maxima are found in the eastern hemisphere at 100 hpa and in the western hemisphere at 150 hpa and below activities calculated from the outgoing longwave radiation data for the kelvin wave spectral window are different from those in zonal wind about their maximum longitudes and seasons as the climatological background zonal wind in the upper troposphere is easterly in the eastern hemisphere and westerly in the western hemisphere it seems that the difference of kelvin wave activities between 100 hpa and 150 hpa is closely related to the background wind field affecting kelvin wave propagation and dissipation iso activities in zonal wind at 100 hpa are vigorous in the western pacific during northern winter and we may find relation to those in olr this indicates that the eastward moving disturbance with the iso time scale is coupled with the organized convective system such as the madden julian oscillation

vertically propagating kelvin waves and tropical tropopause variability abstract the relationship between local convection vertically propagating kelvin waves and tropical tropopause height variability is examined this study utilizes both simulations of a global primitive equation model and global observational datasets regression analysis with the data shows that convection over the western tropical pacific is followed by warming in the upper troposphere ut and cooling in lower stratosphere ls over most longitudes which results in a lifting of the tropical tropopause the model results reveal that these ut ls temperature anomalies are closely associated with vertically propagating kelvin waves indicating that these kelvin waves drive tropical tropopause undulations at intraseasonal time scales the model simulations further show that regardless of the longitudinal position of the imposed heating the ut ls kelvin wave reaches its maximum amplitude over the western pacific this result together with an analysis based on wave action conservation is used to contend

radiosonde observations of equatorial atmosphere dynamics over indonesia 1 equatorial waves and diurnal tides this paper describes the characteristics of the mean winds equatorial waves with periods ranging from 4 to 20 days and diurnal tides determined by analyzing the profiles of wind velocity temperature and humidity obtained every 5 7 hours in the height range up to about 35 km with a height resolution of 150 m during an observation campaign conducted february 27 to march 22 1990 in east java indonesia the structures of the mean winds in the troposphere and lower stratosphere seemed to be affected by the australian monsoon and the quasi biennial oscillation respectively frequency spectra indicated that the equatorial waves as well as the diurnal tides were dominant below about 25 km while gravity waves with periods shorter than 4 days became more significant above 25 km a 7 day oscillation showing an antiphase relation between the eastward and northward components and exhibiting large amplitudes was observed in the lower troposphere the time height variations of the activity of this 7 day oscillation were clearly correlated with a region of high relative humidity perturbations in the zonal wind and temperature with wave periods varying from 15 to 17 days were also enhanced in the troposphere while kelvin waves with periods of about 7 and 20 days were detected in the lower stratosphere and activity near the tropopause was conspicuously enhanced we found that the 20 day kelvin wave greatly modified the structure of the tropopause such as the minimum temperature the tropopause height and the values of the brunt vaisala frequency squared n2 which further suggests the effects of kelvin waves on the transportation of tropospheric water vapor into the stratosphere and on the downward mixing of stratospheric minor constituents into the troposphere the observed profiles of the diurnal oscillation were compared with those of a numerical model assuming only migrating tides which reasonably agreed above about 25 km below 25 km however the observed amplitudes were 1 1 5 m s exceeding those of the model about 10 times moreover the phase profiles involved fluctuations with small vertical scales suggesting interference by many nonmigrating tides with short vertical wavelengths