principles of early development of karst conduits under natural and man made conditions revealed by mathematical analysis of numerical models numerical models of the enlargement of primary fissures in limestone by calcite aggressive water show a complex behavior if the lengths of the fractures are large and hydraulic heads are low as is the case in nature dissolution rates at the exit of the channel determine its development by causing a slow increase of water flow which after a long gestation time by positive feedback accelerates dramatically within a short time span mathematical analysis of simplified approximations yields an analytical expression for the breakthrough time when this happens in excellent agreement with the results of a numerical model this expression quantifies the geometrical hydraulic and chemical parameters determining such karst processes if the lengths of the enlarging channels are small but hydraulic heads are high as is the case for artificial hydraulic structures such as dams it is the widening at the entrance of the flow path which determines the enlargement of the conduit within the lifetime of the dam this can cause serious water losses this can also be explained by mathematical analysis of simplified approximations which yield an analytical threshold condition from which the safety of a dam can be judged thus in both cases the dynamic processes of karstification are revealed to gain a deeper understanding of the early development of karst systems as a further important result one finds that minimum conditions below which karstification cannot develop do not exist

gravity wave variability and interaction with lower frequency motions in the mesosphere and lower thermosphere over hawaii abstract radar observations of the mesosphere and lower thermosphere over kauai hawaii have provided measurements of the horizontal wind field since september 1990 horizontal velocity variances in the gravity wave band of frequencies were computed for several averaging intervals over the entire dataset the results correlated with tidal and lower frequency winds show evidence of filtering of gravity waves by tidal and other lower frequency motions spectra of gravity wave variances for two years of data display peaks at planetary wave as well as tidal periods primarily near 12 24 48 h and 16 day periods the modulation of gravity wave variance during four distinct background regimes is examined one in which the diurnal tide predominates another in which the 2 day wave is large a third in which the zonal mean wind and tidal amplitudes are large and a fourth in which the zonal mean tidal and 2 day amplitudes are all small intervals in which the diurnal tide or the 2 day wave predominates s

a comparative study of mesospheric solar tides observed at adelaide and kyoto observations of winds in the upper mesosphere and lower thermosphere 80 110 km measured at the geographically conjugate locations of adelaide 35 s 138 e and kyoto 35 n 136 e in the years 1983 1985 are used to study hemispheric differences in the behavior of the solar diurnal and semidiurnal tides comparisons of the tidal amplitude and phase parameters show that there are distinct hemispheric asymmetries the diurnal tide is usually much larger in amplitude at adelaide and it exhibits a height structure which indicates a relatively larger contribution from the propagating 1 1 mode at this location comparisons with recent theoretical work suggest that while some of these differences may be due to hemispheric differences in forcing and or to interactions between the tide and the background winds in the middle atmosphere it is also possible that they indicate weaker turbulent induced damping of the 1 1 mode in the southern hemisphere the characteristics of the semidiurnal tide agree well at the two locations it is found that the zonal wind components are about 6 hours out of phase and the meridional components are in phase in all seasons this behavior taken together with the inferred vertical wavelengths which are greater than 100 km in summer and 45 80 km in winter indicates that there are strong contributions from the antisymmetric 2 3 mode probably forced by wind induced mode coupling from the symmetric 2 2 mode the phases near 90 km exhibit a bimodal or two state behavior with the phases being almost constant in one state near the june solstice and then making a rapid transition of between 4 and 6 hours to another phase stable state near the december solstice the duration of the state near the june solstice 6 8 months is longer than the duration of the state at the december solstice although the agreement between recent models and our observations is relatively good better agreement may be expected when more realistic wind distributions especially for the southern hemisphere are used in the models

an estimate of the momentum deposition in the lower thermosphere by the observed diurnal tide abstract this paper reports a calculation of the acceleration of the zonal mean flow induced by dissipating tides in the equatorial lower thermosphere estimates of the gravest symmetric gravitational hough mode 1 1 of the migrating diurnal tide are obtained from monthly composites of global winds observed by the upper atmosphere research satellite high resolution doppler imager using the principles of classical tidal theory the tidal momentum flux divergence is computed for a series of monthly mean 1 1 fields from january 1992 to may 1993 the contribution to the mean flow by the leading mode of the migrating tide ranges between 5 and 20 easterly m s 1 day 1 in the equatorial lower thermosphere a semiannual variation is noted in the tidal amplitudes and the inferred tidal accelerations these variations are consistent with observed trends in the zonal mean flow of the lower thermosphere

short period fluctuations of the diurnal tide observed with low latitude mf and meteor radars during cadre evidence for gravity wave tidal interactions mf and meteor radar data from four equatorial and subtropical sites hawaii christmas island jakarta and adelaide are used to examine diurnal tide amplitude and phase variability at mesosphere and lower thermosphere altitudes all sites exhibit significant seasonal variability with the largest amplitude fluctuations occurring at hawaii and adelaide shorter term variability is found to occur primarily on timescales of 5 to 30 days amplitude and phase fluctuations are well correlated among different sites on occasion but in general the amplitude and phase coherences are low and suggest significant local influences on the tidal structures the temporal behavior of height variations of the diurnal tide amplitude and phase is also examined cross correlations and cross spectra of these tidal parameters especially between the amplitude and phase are examined closely the tendency for phase maxima to lead amplitude maxima is consistent with tidal modulation of gravity wave propagation and momentum fluxes with a corresponding feedback by the gravity wave momentum flux divergences on the observed tidal structures these results substantially extend previous more limited studies of gravity wave tidal interactions and provide a statistical basis for the possible importance of this interaction and its influences on the diurnal tidal structure

a model of the early evolution of karst aquifers in limestone in the dimensions of length and depth a new model of the early evolution of limestone karst aquifers in the dimensions of length and depth is presented in its initial state the aquifer consists of a rock massive with evenly spaced fractures of about 50 mm aperture widths with an hydraulic conductivity of 10 27 ms 21 in addition to this a coarser network of prominent fractures with aperture widths of several 100 mm is also present boundary conditions of constant recharge 450 mm year or constant head from the input of allogenic streams are imposed first the position of the water table in the aquifer is calculated then dissolutional widening during a time step in all the fractures below the water table is found by use of the well known nonlinear dissolution kinetics of limestone this is iterated and the position of the water table as well as the fracture widths are found as a function of time in the case of constant recharge to a karst plateau the water table in any case drops to base level and conduits there propagate from the spring headwards if constant head conditions are valid the position of the water table remains almost stable and conduits propagate along the water table from the input towards the spring there is competition between conduit evolution along prominent fractures and along tight fissures close to the water table in any case under constant head conditions one of these pathways wins and early karst evolution is terminated by a breakthrough event with an explosive increase of the flow through the aquifer until constant head conditions break down depending on the boundary conditions of constant head or constant recharge or a combination of both it is possible to describe models of cave genesis which have been derived from field evidence such as the water table models of swinnerton geol soc am bull 34 1932 662 and rhoades and sinacori j geol 49 1941 785 as well as the four state model by ford and ewers can j earth sci 15 1978 1783 q 2001 elsevier science b v all rights reserved

gravity wave interactions with the diurnal propagating tide observations of the diurnal propagating solar tide in the mesosphere and lower thermosphere 50 150 km indicate substantial annual variations in tidal amplitudes observations and modeling efforts suggest that interactions with internal gravity waves can result in significant modifications of the diurnal tide herein a two dimensional 2 d linear steady state tidal model is used in conjunction with hybrid lindzen matsuno gravity wave parameterization to examine the role of gravity wave interactions in the seasonal variability of the diurnal tide in the mlt the analysis indicates that annual variations of the background atmosphere result in significant annual variations in the eddy diffusion and the diurnal harmonic of the momentum flux divergence wave stress produced by breaking gravity waves the seasonal variability in these two mechanisms can explain the observed semi annual variability in the diurnal tide amplitude minima at solstice and maxima at equinox the relative roles of wave stress and diffusion are examined and it is shown that both play important roles in tidal modification by damping its amplitude the effects of varying inputs to the gravity wave parameterization are explored

mesospheric momentum flux studies at adelaide australia observations and a gravity wave tidal interaction model abstract we present here the results of an analysis of gravity wave momentum fluxes in the mesosphere and lower thermosphere inferred using a dual beam doppler radar near adelaide australia during june 1984 our analysis reveals that over 70 of the momentum flux and of the inferred zonal drag was due to gravity waves with observed periods less than one hour this suggests that it is the gravity waves with high intrinsic frequencies and small horizontal scales that are most effective at transporting momentum into the middle atmosphere the temporal variations in the momentum flux and flux divergence due to high frequency motions were also examined in detail in addition to daily variability a strong diurnal modulation was observed to occur this was found to be correlated with the phase of large amplitude diurnal tidal motions as a result of these observations a gravity wave tidal interaction model was proposed which accounts for all of the major features of the observed data including a reduction i

mean motions and tidal and two day structure and variability in the mesosphere and lower thermosphere over hawaii abstract an overview of the motion field and an analysis of the tidal and 2 day wave motions observed in the mesosphere and lower thermosphere over the central pacific from 1 october 1990 through 19 august 1992 is presented characteristics and interactions of motions at lower and higher frequencies will be addressed elsewhere wind measurements were obtained with an mf radar operating on kauai hawaii 22 n 160 w using the partial reflection drift technique results presented in this paper reveal a zonal mean motion reflecting the mesopause semiannual oscillation msao observed at more equatorial latitudes from january to july coinciding with the period during which the msao and the annual cycle of the zonal mean wind at higher latitudes are in phase eastward and westward maxima are 55 m s 1 below 80 km and 45 m s 1 near 85 km during the first year with maxima of 57 and 53 m s 1 during the second year and evidence of substantial interannual variability the second msao cycle is greatly suppresse

first observations of mesospheric dynamics with a partial reflection radar in hawaii 22 n 160 w we present here an overview of the wind measurements made during the first year of operation of a partial reflection radar system in hawaii the system operates at 1 98 mhz and provides wind estimates between 60 and 100 km at 2 km intervals our wind observations reveal a zonal mean motion that has several features in common with the mesopause semiannual oscillation msao seen at more equatorial latitudes but which is influenced as well by the seasonal variations of the mesospheric jet structure at higher latitudes major features of the zonal mean wind structure include a downward progression of strong eastward and westward phases of the msao from january to july coinciding with the period during which the msao and the annual cycle of the zonal mean wind at higher latitudes are in phase this results in an eastward maximum of 60 ms 1 near 80 km during january and february which descends rapidly and a westward maximum of 50 ms near 85 km during march and april which descends much more slowly the second msao cycle is greatly suppressed relative to the first due to the reversal of the correlation between this and the annual cycle at higher latitudes from july to december mean eastward motions occur primarily above 85 km early in this cycle and throughout the height range at later times planetary wave activity is seen to contribute substantial variability during times of eastward mean flow and to have a smaller role when zonal mean motions are westward tidal and 2 day motions are found to be large and variable with the maximum 2 day amplitudes occurring during february and august the largest diurnal tides were observed during october and november march and april and july and august while the semi diurnal amplitudes exhibited a minimum from april to june

mesospheric momentum fluxes observed by the mst radar at poker flat alaska abstract an analysis of the wave motions observed with the poker flat mst radar during the winter summer and fall of 1986 is presented in this paper monthly and daily mean winds momentum fluxes and velocity variances are investigated in detail while several features are in agreement with previous measurements some significant differences also are found to exist in our observations monthly mean horizontal winds between 82 and 89 km have amplitudes of 20 40 m s 1 westward and 10 25 m s 1 southward in july and august in fall and winter the horizontal winds between 58 and 75 km are weaker and essentially eastward monthly mean vertical velocities are predominantly downward at 0 3 m s 1 which implies a vertical wave energy flux of 0 1 w m 2 higher than that estimated at low latitudes monthly mean horizontal variances are 1600 m2 s 2 in summer and 600 m2 s 2 in fall and winter with vertical variances 3 m2 s 2 monthly mean zonal and meridional momentum fluxes contributed predominantly by wa

a study of the relationship between stratospheric gravity waves and polar mesospheric clouds at davis antarctica 1 we used a rayleigh lidar located at davis station east antarctica to compare polar mesospheric cloud pmc and stratospheric gravity wave gw strengths in the austral summer 2005 2006 earlier similar studies from greenland noted that intervals of large stratospheric gw activity appeared to coincide with reduced pmc strengths we measure the stratospheric gw strength in the 30 45 km altitude range for waves of vertical wavelength between 2 and 10 km and of periods greater than 1 h we find little consistency with the greenland studies as the occurrence of pmc over davis appear to have little relationship to observed stratospheric gravity wave activity hemispheric differences in both pmc strength and occurrence and in gravity wave strength may have a role in explaining our results our data suggest that a significant controller of occurrence of pmc over davis is related to diurnal tidal movement we also investigate the potential influence of sampling biases in our data set

early development of karst systems 2 turbulent flow a simulation model developed to explore patterns of fracture enlargement within incipient limestone karst aquifers has been extended to turbulent flow in contrast to the highly selective passage enlargement that occurs early in cave network development under laminar flow the transition to turbulent flow results in more general passage enlargement leading to maze networks when initial fractures are large and hydraulic gradients are high these results support previously published hypotheses for the development of maze patterns including formation within structural settings that have created initially large fractures or within flow systems periodically inundated by flooding maze development is also favored under turbulent flow when passages are entirely water filled and where the groundwater flow system is long lived by contrast branched patterns are most common when passages become free surface subterranean streams because depression of the piezometric surface along main passages downcutting along main passages and possible infilling with sediment of side passages limit the sharing of discharge among interconnected fractures or bedding planes that promote maze development

prediction of unconfined compressive strength of carbonate rocks using artificial neural networks the unconfined compressive strength ucs of intact rocks is an important geotechnical parameter for engineering applications determining ucs using standard laboratory tests is a difficult expensive and time consuming task this is particularly true for thinly bedded highly fractured foliated highly porous and weak rocks consequently prediction models become an attractive alternative for engineering geologists the objective of study is to select the explanatory variables predictors from a subset of mineralogical and index properties of the samples based on all possible regression technique and to prepare a prediction model of ucs using artificial neural networks ann as a result of all possible regression the total porosity and p wave velocity in the solid part of the sample were determined as the inputs for the levenberg marquardt algorithm based ann lm ann the performance of the lm ann model was compared with the multiple linear regression reg model when training and testing results of the outputs of the lm ann and reg models were examined in terms of the favorite statistical criteria which are the determination coefficient adjusted determination coefficient root mean square error and variance account factor the results of lm ann model were more accurate in addition to these statistical criteria the non parametric mann whitney u test as an alternative to the student s t test was used for comparing the homogeneities of predicted values when all the statistics had been investigated it was seen that the lm ann that has been developed was a successful tool which was capable of ucs prediction

the role of dissolution kinetics in the development of karst aquifers in limestone a model simulation of karst evolution to model the development of karst aquifers from primary fissures in limestone rock a numerical model of solutional widening of such fractures by calcite agressive water is suggested the geological setting determines relevant geometrical parameters i e length of the fracture its initial width and the hydraulic gradient driving water from the input to the output to simulate the solutional widening as it proceeds in time the solution rates must be known as a function of concentration c of dissolved calcite they are given as a first order kinetic rate law for c leq k cdot c eq as f 1 alpha 0 c c eq for c k cdot c eq close to equilibrium a fourth order rate law becomes dominant f 4 beta cdot c c eq 4 the parameters alpha 0 beta and k depend on the chemistry of the carbonate system and rock chemistry the saturation concentration c eq with respect to calcite depends on the initial co 2 concentration of the inflowing solution

early development of karst aquifers on percolation networks of fractures in limestone we have modeled flow and dissolution processes within percolation networks representing stochastic primary fracture systems in limestone at the beginning of karstification flow is evenly distributed on all fractures available as the system develops by dissolutional widening of the fractures preferred flow pathways evolve which attract more and more flow until at breakthrough the total flow rate increases dramatically these breakthrough times have been investigated with regard to their dependence on the initial fracture aperture width the dimension of the evolving karst aquifer hydraulic gradients connectivity of the percolation network and the chemical parameters such as higher order rate constants and exponents and equilibrium concentration they exhibit a behavior similar to that of breakthrough times for one dimensional conduits dreybrodt 1996 our results show that the structure of the evolving karst aquifer is determined by the initial geological setting however the final conduits are selected from competing pathways with potential breakthrough times close to each other whereby the details of the distribution of undersaturation with respect to calcite play an important role

mean winds and tidal and planetary wave motions over hawaii during airborne lidar and observations of hawaiian airglow aloha 93 the mean and low frequency wave motions in the mesosphere and lower thermosphere from 70 to 98 km were observed with the mf radar on kauai during the airborne lidar and observations of hawaiian airglow aloha 93 measurement campaign two day mean zonal winds exhibited a transition from a variable structure with altitude at the beginning of october having westward motions near 80 km and eastward motions at upper and lower levels to more uniform eastward winds with altitude at the end of october two day mean meridional motions were equally variable with northward motions at all altitudes on october 1 northward motions above 80 km and southward motions below throughout much of the campaign and largely northward motions at the end of october zonal and meridional winds exhibited significant oscillations at 5 to 30 day periods indicative of planetary wave activity during this interval diurnal tidal amplitudes and phases were likewise variable with maximum and minimum rms amplitudes of 35 and 10 ms 1 approximate phase quadrature with meridional leading zonal amplitude and phase variability on time scales of 5 to 15 days and an overall phase advance during october of 10 h other tidal components and the two day wave had rms amplitudes of 5 to 10 ms 1

an integrated view of the 1987 australian monsoon and its mesoscale convective systems i horizontal structure this observational study is organized around three issues the forcing of the monsoon flow by embedded deep convection the thermodynamic conditions that support the convection and the structures of the mesoscale convective systems mcss that constitute much of the deep convection the monsoon convective cloudiness occurred predominantly offshore over the earth s warmest waters week long periods of widespread deep convection caused cycles of monsoon spin up culminating in tropical cyclone formation momentum transports by the convection also created smaller scale vortex pairs in the upper troposphere sounding data suggest that the convection was modulated by low level processes not by large scale deep forced ascent triggering by mesoscale boundary layer cold pool boundaries and coastlines determined specifically where convection occurred while several positive feedbacks acted to keep regional thermodynamic conditions favourable hence monsoon convection once initiated persisted as self exciting superclusters composed at any instant of many distinct mcss the observed mcss all contained areas of deep convection and stratiform precipitation areas stratiform precipitation usually evolved in place from convective cells although precipitation also occasionally fell from overhanging anvils created by upper level shear the mcss within similar synoptic wind environments tended to have similar mesoscale structures this fact reflects the effects illustrated herein of environmental winds upon the relative motions of cold pools which trigger new convective cells and stratiform precipitation areas which evolve from old convective cells

carbon dioxide and dissolution rate dynamics within a karst underflow overflow system savoy experimental watershed arkansas usa abstract within numerical models of karst development geochemical and hydrological boundary conditions are typically assumed to be constant however rates of calcite dissolution in natural karst systems can vary substantially in time in particular variation in carbon dioxide co2 concentrations has been shown to produce time variability in dissolution rates in karst streams but controls on co2 variation within karst systems are relatively poorly quantified here we analyze hourly in situ measurements of dissolved co2 discharge and specific conductance at a pair of karst underflow overflow springs and examine potential drivers of variability in co2 and dissolution rates the springs display strong seasonal variability in co2 and saturation state as well as moderate variation during storm events though both springs have elevated co2 concentrations in the summer season the overflow spring experiences a substantial decrease in dissolved co2 below a critical discharge threshold we hypothesize that this decrease results from ventilation within the overflow portion of the system as segments of the flow path transition from full pipe to open channel flow the overflow spring experiences substantially lower average dissolution rates than the underflow spring despite larger discharge and chemical variability during high flow events at the overflow spring though open systems are frequently presumed to have higher dissolution rates because of their ability to replenish co2 that is consumed in the dissolution process these data suggest that dissolution rates within the closed portion of the system may in some cases be higher due to the inability of closed flow paths to ventilate excess co2 to the atmosphere such conditions are likely to occur in conduits where co2 concentrations are elevated above atmospheric levels and average flow through times are short compared to the time scale over which water reaches equilibrium with respect to calcite

fluid transfers in a carbonate gaseous aquifer through the local tectonic and geodynamic history abstract a multidisciplinary approach was developed to analyse the impact of the various tectonic joints on water and gas transfers in the carbonate aquifer of quezac southern massif central france microtectonic measurements confirmed the local tectonic history and the structural map was completed by a morphostructural approach using detailed photointerpretation of both aerial photographs and a digital elevation model the past fluid transfers were discussed on the basis of field observations and the possible geodynamic context the present fluid transfers observed in the field were related to four main groups of tectonic joints based on a tectonic and morphostructural approach the history of tectonic constraints geodynamic context and fluid transfers was then reconstructed it highlighted the major role of the north south tectonic joints for water flows followed by east west joints because of their longest karstification history joints with nw se and ne sw orientations which were more recently karstified appeared to have less influence on water transfers the weak gas production at the surface of north south faults was explained by its dispersion owing to their intense karstification on the basis of the innovative multidisciplinary approach we propose a model for the water and gas preferential flow paths taking the local tectonic and geodynamic context into account

classification of slopes and prediction of factor of safety using differential evolution neural networks slope stability analysis is one of the most important problems in geotechnical engineering the development in slope stability analysis has followed the development in computational geotechnical engineering this paper discusses the application of different recently developed artificial neural network models to slope stability analysis based on the actual slope failure database available in the literature different ann models are developed to classify the slope as stable or unstable failed and to predict the factor of safety the developed ann model is found to be efficient compared with other methods like support vector machine and genetic programming available in literature prediction models are presented based on the developed ann model parameters different sensitivity analyses are made to identify the important input parameters

observational evidence of tidal gravity wave interactions using the uwo 2 mhz radar the degree of interaction between atmospheric gravity waves and tides is an issue which is of great importance in middle atmosphere studies it is especially important with regard to tidal variability which is frequently observed in the mesosphere and lower thermosphere but as yet has not been subject to adequate study in this paper we present some strong observational evidence of such interactions made with the uwo 2 mhz radar near london canada our observations show significant correlation between gravity waves and tides diurnal at certain times of the year and the nature of the correlation is intermittent and varies with time of year it is possible that differences between tidal amplitudes at sites with mesoscale separations may be explained in terms of such phenomena we also propose a simple model which is found to be consistent with the major features of the observed data

modeling three dimensional karst aquifer evolution using different matrix flow contributions summary we have developed the program package karstaquifer which simulates flow and transport in a three dimensional transient karst aquifer consisting of fractures and matrix elements the fractures can be enlarged by chemical dissolution of calcite increasing the secondary permeability of the karst aquifer boundary conditions for our model setup are guided by published benchmark models for karst aquifer evolution in two dimensions length and width with a 100 m high hydraulic head difference across the model domain responsible for relatively fast evolution of the aquifer we are interested in the effect of the third dimension on the evolution of the karst aquifer especially the effect of matrix flow with a matrix defined either as porous medium or as fine fracture system or both we first discuss our model results using a pseudo 3d setup to be able to directly compare results to the 2d benchmark scenarios published we then discuss real 3d models with a prominent fault located in the central part of the aquifer connecting input and output regions finally we replace the prominent fault with a statistical fracture diameter distribution our results compare well with existing 2d scenarios and the additional third dimension offers new insights into the evolution of karst aquifers especially the role of matrix flow under fixed head boundary conditions in their early phases can be studied in more detail

modelling unsaturated flow in an evolving karst aquifer a two dimensional cross section of a karst aquifer in which chemical dissolution enlarges fractures with time is studied the karst aquifer is recharged by precipitation and drains towards a resurgence the initial aquifer has low conductivities both in the rock matrix and the fracture network and the initial water table is high as the enlargement of fractures by dissolution increases the fracture conductivity the water table drops until it reaches a steady state along the level of the resurgence several parameterisations are discussed for flow in the unsaturated zone above the water table it is shown that different approaches result in similar cave passage patterns with a large water table cave draining the recharge towards the resurgence however flow patterns in the unsaturated zone can be very different for the different parameterisations

comparative study of short term diurnal tidal variability examination of the simultaneous temperature measurement from the sounding of the atmosphere using broadband emission radiometry saber instrument on board the thermosphere ionosphere mesosphere energetics and dynamics timed satellite not only confirms the existence of the inversion layer but also reveals the global nature of the inversion suggesting the presence of a transient planetary wave in the mesosphere the large tidal variability therefore is probably a consequence of the interaction between the transient planetary wave and tides this possibility is investigated by using the ncar thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm and by comparing model results with the lidar saber and timed doppler interferometer tidi measurements with a large transient planetary wave specified at the model lower boundary the model is able to produce strong diurnal tidal variability comparable to that from the lidar observation and the modeled temperature inversion is similar to that from the saber measurement the model results suggest that the planetary tidal wave interaction excites nonmigrating tides and modulates the gravity modes and or the rotational modes of the diurnal migrating tide among the nonmigrating tides the diurnal zonally symmetric s 0 component is the strongest and its interaction with the planetary wave leads to a strong diurnal eastward wave number 1 component

early development of karst systems 1 preferential flow path enlargement under laminar flow modeling of flow and solutional processes within networks of interconnected conduits in limestone aquifers indicates that enlargement occurs very selectively during the early stages of karst aquifer development under laminar flow if initial flow paths are uniform in size almost all enlargement occurs along a single set of connected conduits that lie along a direct path between recharge and discharge locations and are aligned along the hydraulic gradient with a sufficiently large variation in initial aperture widths enlargement occurs along the flow path offering the least resistance to flow but since flow rates in laminar flow are proportional to the fourth power of diameter but only linearly proportional to hydraulic gradient the preferentially enlarged set of fractures may follow an indirect path results disfavor earlier suggestions that nonselective cave patterns result from artesian flows at least under laminar flow conditions and that all passages should be competitive until the onset of turbulent flow

cave development in the swabian alb south west germany a numerical perspective summary the formation of phreatic cave conduits in the carbonate aquifer of the swabian alb south west germany is discussed by means of numerical simulations three active cave conduit systems the blautopf cave the aachtopf cave and the wimsener cave have been partially explored by divers and exhibit a continuous conduit flow path with phreatic loops down to 50 m below the average water table these three systems drain catchments between 50 and 280 km2 and largely follow the dip of the jurassic limestone beds we use the numerical model karst karst aquifer simulation tool to explore the possibility of structural control of the conduit evolution we show that both the dip of the bedding and the frequency of major bedding partings is likely to result in numerical drainage paths which are similar to the observed cave systems

first observational evidence of the modulation of gravity wave activity in the low latitude middle atmosphere by equatorial waves 1 evidence for the modulation of the gravity wave activity by the equatorial waves in the tropical middle atmosphere is presented using the rayleigh lidar observations of the temperature over gadanki 13 5 n 79 2 e and the rocketborne measurements of winds over shriharikota range 13 7 n 80 2 e during the period of 29 february to 31 march 2000 the potential energy per unit mass associated with the gravity wave activity in the upper stratosphere and mesosphere is found to undergo periodic fluctuations which is well correlated with the zonal and meridional wind oscillations in the stratosphere produced by the equatorial waves the most dominant modulation of the gravity wave activity due to equatorial waves is found to occur at periods around 4 days and 12 days minimum gravity wave activity in the mesosphere is observed during the southward phase of meridional wind and the westward phase of zonal wind oscillations in the lower stratosphere

artificial neural networks and dendroclimatic reconstructions an example from the front range colorado usa the feasibility of reconstructing total spring precipitation for the south platte river basin from tree ring chronologies using artificial neural networks is explored the use of artificial neural networks allows a comparison of reconstructions resulting from both linear and nonlinear models both types of models produced reconstructions that explained more than 40 of the variation in spring precipitation and were well verified with independent data although the nonlinear models produced higher r2 values than did the linear model for the calibration period they performed less well in the independent period this result and other model evaluation statistics suggest that in this study the nonlinear models contain a greater degree of overfit than the linear model and thus do not offer a clear improvement over the linear model for the reconstruction of spring precipitation in this region however neural networks offer an alternative approach to linear regression techniques and may provide improved den

a model of early evolution of karst conduits affected by subterranean co2 sources in investigating early karstification of one dimensional conduits by computer models so far one has assumed that the co2 content of the calcite aggressive water stems entirely from the surface subterranean sources of co2 however can rejuvenate the solutional power of water already close to equilibrium with respect to calcite and boost dissolution rates in a first scenario we have investigated the influence of a punctual source of co2 as the most simple case of release of co2 into a karstifiable fracture at some position kl from its entrance of the widening joint with length l k 1 the results show that only a small increase of the pco2 in the solution to about 0 01 atm is sufficient to reduce the breakthrough times to about 0 3 with respect to the case where no co2 is delivered other sources of co2 are due to the metabolic activity of microorganisms the existence of such diverse subterraneous microbial life in karst systems is demonstrated whether situated on the fissure surfaces or free floating in the karst water one basic product of their metabolism is co2 this contributes over the whole flow path to the pco2 of the karst water therefore in a second scenario we assumed a constant rate of co2 input along parts of the fracture as could be delivered by the activity of aerobic bacteria dwelling at its walls such a scenario also applies to an extended diffuse co2 migration from volcanic activity deep underground in this case drastic reductions of the breakthrough time by about one order of magnitude are observed these reductions are enhanced when the fracture aperture width of the initial fracture decreases the physicochemical mechanisms of enhancement of karstification are discussed in detail by considering the evolution of the fracture aperture width and of the dissolution rates in space and time

influence of co2 dynamics on the longitudinal variation of incision rates in soluble bedrock channels feedback mechanisms we use measurements of dissolution rates of limestone tablets placed along a cave stream to estimate rates of modern incision dissolution rates within the stream display a systematic decrease with downstream distance we discuss a variety of mechanisms that could be responsible for the longitudinal decrease in dissolution rates and develop simple mathematical models for each the dissolutional length scales that arise from each model allow a first order estimate of the plausibility of each mechanism and motivate further field studies to test each possibility water chemistry and other field data suggest that a decrease in the concentration of co2 along the cave stream is responsible for the observed decrease in dissolution rates we propose two potential mechanisms that could trigger this reduction in dissolved co2 and discuss the plausibility of each mechanism in light of the field data collected either of these mechanisms introduces a feedback loop whereby the stream profile of a channel in soluble bedrock indirectly influences co2 concentrations in the water via either microbial or hydraulic processes the co2 concentration in turn effects the incision rates and therefore the future stream profile this study illustrates the importance of co2 dynamics in determining incision rates in a soluble channel and points to further modeling and field work that are needed in order to enable the development of realistic stream incision models in soluble strata

a model comparison of karst aquifer evolution for different matrix flow formulations the evolution of permeability and flow in a karst aquifer is studied by numerical simulations the aquifer considered consists of a large central fracture a network of finer fissures and a porous rock matrix enlargement of both the central fracture and the fissures by chemical dissolution is possible hence the conductivities in the fracture and the fissure system can increase with time no dissolution is allowed in the porous rock matrix which has a constant conductivity flow is driven by a simple fixed head boundary condition representative for the initial phase of karstification a systematic parameter study is carried out by varying the initial width of the fissure network and the conductivity of the rock matrix while keeping the initial width of the central fracture fixed key parameters such as flowrates breakthrough times and conductivities for the different models are compared if either the conductivity of the rock matrix is high enough or the initial width of the fissures is large enough to carry flow breakthrough times of the aquifer are significantly reduced when compared to a model with low matrix conductivity and small fissures however due to the dissolutional widening of fissures the evolution of the aquifer is distinctively different for models with rock matrix simulated by a porous medium or a fissure network

southern argentina agile meteor radar system design and initial measurements of large scale winds and tides 1 the southern argentina agile meteor radar saamer was installed at rio grande on tierra del fuego 53 8 s 67 8 w in may 2008 and has been operational for 24 months this paper describes the motivations for the radar design and its placement at the southern tip of south america its operating modes and capabilities and observations of the mean winds planetary waves and tides during its first 20 months of operation saamer was specifically designed to provide very high resolution of large scale motions and hopefully enable direct measurements of the vertical momentum flux by gravity waves which have only been possible previously with dual or multiple beam radars and lidars or in situ measurements saamer was placed on tierra del fuego because it was a region devoid of similar measurements the latitude was anticipated to provide high sensitivity to an expected large semidiurnal tide and the region is now recognized to be a hot spot of small scale gravity wave activity extending from the troposphere into the mesosphere and lower thermosphere perhaps the most dynamically active location on earth saamer was also intended to permit simultaneous enhanced meteor studies including head echo and nonspecular measurements which were previously possible only with high power large aperture radars initial measurements have defined the mean circulation and structure exhibited planetary waves at various periods and revealed large semidiurnal tide amplitudes and variability with maximum amplitudes at higher altitudes often exceeding 60 m s 1 and amplitude modulations at periods from a few to 30 days

tidal modulation of the gravity wave momentum flux in the antarctic mesosphere airglow imager and dynasonde idi radar wind measurements at halley station antarctica 76degreess 27degreesw have been used to estimate the diurnal variation of the vertical fluxes of horizontal momentum carried by high frequency atmospheric gravity waves the cross correlation coefficients between the vertical and horizontal wind perturbations were calculated from the sodium airglow imager data collected during four consecutive nights of near total darkness during july of 2000 these were combined with wind velocity variances from coincident radar measurements to estimate the upper limit of the vertical flux of horizontal momentum during three hour intervals throughout the period the resulting momentum flux showed a marked semi diurnal oscillation in the zonal and meridional components calculations of the momentum flux through the na airglow show variations in period and phase consistent with the observations implying that tidal propagation and modulated gravity wave forcing may both affect observed wind variations

landslide susceptibility mapping using frequency ratio analytic hierarchy process logistic regression and artificial neural network methods at the inje area korea every year the republic of korea experiences numerous landslides resulting in property damage and casualties this study compared the abilities of frequency ratio fr analytic hierarchy process ahp logistic regression lr and artificial neural network ann models to produce landslide susceptibility index lsi maps for use in predicting possible landslide occurrence and limiting damage the areas under the relative operating characteristic roc curves for the fr ahp lr and ann lsi maps were 0 794 0 789 0 794 and 0 806 respectively thus the lsi maps developed by all the models had similar accuracy a cross tabulation analysis of landslide occurrence against non occurrence areas showed generally similar overall accuracies of 65 27 64 35 65 51 and 68 47 for the fr ahp lr and ann models respectively a correlation analysis between the models demonstrated that the lr and ann models had the highest correlation 0 829 whereas the fr and ahp models had the lowest correlation 0 619

tidal gravity wave interactions and their influence on the large scale dynamics of the middle atmosphere model results results from a modified version of the quasi geostrophic model of mclandress and mcfarlane 1993 in combination with the tidal model of forbes 1982a b are used to delineate the role of tides in modulating gravity wave momentum fluxes and the ensuing effects on the large scale circulation of the middle atmosphere for solstice conditions the influence of the tidal wind fields on the location and strength of the gravity wave drag is strongest in the mesosphere and lower thermosphere where the tidal winds are of the same order as the zonal mean component due to the nonlinear dependence on the local wind speed the daily mean gravity wave drag in the model can differ significantly depending on whether or not tidal variations are included at middle and low latitudes these differences are largest and occur as a result of the filtering effects of the shorter vertical wavelength diurnal tide at more polar latitudes where the longer wavelength semidiurnal tide dominates a slight increase in drag occurs the interaction between the tidal wind fields and the localized orographic gravity wave momentum flux has important consequences for the in situ generation of planetary scale disturbances in particular the amplification of stationary planetary wavenumber 1 is enhanced by the presence of tides in addition forcing of nonmigrating tidal modes is predicted to occur as a result of the localized drag

diurnal nonmigrating tidal oscillations forced by deep convective clouds the global distribution of latent heat released by the diurnal oscillations in deep convective precipitating clouds is investigated as a forcing mechanism of diurnal nonmigrating atmospheric tidal modes the seasonal distribution of this forcing is deduced from 3 hour temporal resolution infrared 11 m radiance measured by four geostationary and two polar orbiting satellites which was transformed into the zonal wavenumber domain yielding migrating and non migrating oscillations the dominant wavenumbers in the forcing include the westward propagating 5 2 and 1 oscillations the eastward propagating 3 oscillation and the standing oscillation these dominant wavenumber oscillations were decomposed into hough functions to describe their meridional structure a vertical profile of latent heating rate was estimated and the dominant 22 tidal modes were used in an f plane model to determine the middle atmospheric response to this tropospheric forcing the f plane model was also excited using heating rates associated with the solar insolation absorption by water vapor the magnitude of the model atmosphere diurnal winds from both water vapor and latent heat is similar at certain locations this response suggests that the superposition of many nonmigrating tidal modes forced by the latent heat release of precipitating clouds is important in understanding the middle atmospheric circulation

prediction of water quality from simple field parameters water quality parameters like temperature ph total dissolved solids tds total suspended solids tss dissolved oxygen do oil and grease etc are calculated from the field while parameters like biological oxygen demand bod and chemical oxygen demand cod are interpreted through the laboratory tests on one hand parameters like temperature ph do etc can be accurately measured with the exceeding simplicity whereas on the other hand calculation of bod and cod is not only cumbersome but also inaccurate many times a number of previous researchers have tried to use different empirical methods to predict bod and cod but these empirical methods have their limitations due to their less versatile application in this paper an attempt has been made to calculate bod and cod from simple field parameters like temperature ph do tss etc using artificial neural network ann method datasets have been obtained from analysis of mine water discharge of one of the mines in jharia coalfield jharkhand india 73 data sets were used to establish ann architecture out of which 58 datasets were used to train the network while 15 datasets for testing the network the results show encouraging similarity between experimental and predicted values the rmse values obtained for the bod and cod are 0 114 and 0 983 respectively

karstification of aquifers interspersed with non soluble rocks from basic principles towards case studies abstract we have developed a numerical model able to describe the karstification of aquifers in fractured rocks containing soluble limestone or gypsum and insoluble layers when water is flowing along fractures crossing the soluble layers it is able to dissolve the material there to increase the aperture width of the conduit and consequently to increase the local hydraulic conductivity depending on the thickness and the distribution of these layers the dissolution can be active only for limited periods or during the whole evolution time fractures located in insoluble layers do not change at all we are interested in the integral effect of these local processes and study four simplified scenarios of karstification along a prominent wide conduit crossing a fractured limestone block we keep the initial and the boundary conditions the same for all scenarios and vary only in the amount and the distribution of the soluble material we demonstrate that aquifers in 100 limestone without any insoluble layers develop along areas with high hydraulic conductivities and high hydraulic gradients creating channel like pathways on the other hand aquifers containing soluble layers with limited thickness develop faster and exhibit diffuse patterns determined by the chemical properties of the rock the second part of the paper is a step towards modeling of real karst systems we present the evolution of an aquifer located in the vicinity of a large hydraulic structure all initial and boundary conditions except the amount and the distribution of the soluble rock remain the same for all scenarios as a material example for the bedrock we chose gipskeuper from an aquifer along the birs river in switzerland this rock consists of soluble gypsum layers and insoluble clays and marls with typical layer thickness in the range of millimeters to centimeters the basic processes discussed in the first part of the paper remain valid we demonstrate that large insoluble zones can impair the karstification process and even completely block it while areas with thin soluble layers can provide a preferential pathway and decrease the evolution times considerably finally we show that the evolution of the leakage rates and the head distribution within the aquifer can sometimes reveal misleading information about the stage of karstification and the safeness of the dam our model can be used not only to study simplified geological settings and basic processes but also to address some of the complications arising when modeling real aquifers

long term oscillations of the wind field in the tropical mesosphere and lower thermosphere from hawaii mf radar measurements 1 wind measurements in the mesosphere and lower thermosphere obtained with a medium frequency mf radar in hawaii 22 n 160 w spanning 16 years are employed to examine the intra annual and interannual variability of the mean and tidal motions at altitudes between 84 and 94 km intra annual periodicities range from 3 to 12 months with significant coherence in altitude and between the zonal and meridional components of each motion field interannual variations confirm the dominant periodicities identified previously at this site and elsewhere in particular the significant diurnal and less significant semidiurnal tidal responses at periods of 28 and 48 months amplitudes of these long period oscillations of the diurnal tide increase with altitude below 92 km and are larger than the amplitudes of the 12 month oscillations above 90 km phases of the 28 and 48 month oscillations show a downward progression with a slightly larger altitude variation in the meridional diurnal tide for the 28 month oscillation and a significantly larger altitude variation in the zonal diurnal tide for the 48 month oscillation the long and nearly continuous hawaii data set also enables characterization of the responses of the wind fields to the 11 year solar cycle both wind and tidal fields exhibit this periodicity but these responses display interesting and different relations to the phase of the solar cycle the 11 year oscillation of the meridional wind is nearly in phase with the solar cycle while the 11 year oscillation of the zonal wind is in approximate quadrature with the solar cycle the 11 year oscillations of the semidiurnal tidal amplitudes and the meridional diurnal amplitude are all in approximate quadrature with the solar cycle with the tidal amplitudes leading by 29 to 37 months while the 11 year oscillation of the zonal diurnal amplitude is somewhat nearer an antiphase than a quadrature relation to the solar cycle leading by 54 months

a comparative study of artificial neural networks bayesian neural networks and adaptive neuro fuzzy inference system in groundwater level prediction predictive modeling of hydrological time series is essential for groundwater resource development and management here we examined the comparative merits and demerits of three modern soft computing techniques namely artificial neural networks ann optimized by scaled conjugate gradient scg ann scg bayesian neural networks bnn optimized by scg bnn scg with evidence approximation and adaptive neuro fuzzy inference system anfis in the predictive modeling of groundwater level fluctuations as a first step of our analysis a sensitivity analysis was carried out using automatic relevance determination scheme to examine the relative influence of each of the hydro meteorological attributes on groundwater level fluctuations secondly the result of stability analysis was studied by perturbing the underlying data sets with different levels of correlated red noise finally guided by the ensuing theoretical experiments the above techniques were applied to model the groundwater level fluctuation time series of six wells from a hard rock area of dindigul in southern india we used four standard quantitative statistical measures to compare the robustness of the different models these measures are 1 root mean square error 2 reduction of error 3 index of agreement ia and 4 pearson s correlation coefficient r based on the above analyses it is found that the anfis model performed better in modeling noise free data than the bnn scg and ann scg models however modeling of hydrological time series correlated with significant amount of red noise the bnn scg models performed better than both the anfis and ann scg models hence appropriate care should be taken for selecting suitable methodology for modeling the complex and noisy hydrological time series these results may be used to constrain the model of groundwater level fluctuations which would in turn facilitate the development and implementation of more effective sustainable groundwater management and planning strategies in semi arid hard rock area of dindigul southern india and alike

gravity wave tidal interactions in the mesosphere and lower thermosphere over rothera antarctica 68 s 68 w 1 a simple technique for measuring gravity wave activity has been used to investigate gravity wave tidal interactions in the polar mesosphere and lower thermosphere mlt the technique uses the radial velocities of individual meteors recorded by meteor radar to derive a statistical measure variance of the activity of the high frequency gravity wave field this technique can measure gravity waves with horizontal wavelengths of up to about 400 km and periods up to approximately 3 hours interactions between the observed gravity wave field and the background wind are investigated using data collected between february 2005 and december 2008 by a meteor radar based at rothera antarctica 68 s 68 w the results reveal the presence of significant modulations of the observed gravity wave field at tidal periods of 12 and 24 hours correlations between the hourly zonal winds and the gravity wave field measured by the meteor radar reveal an in phase relationship between the hourly zonal winds and gravity wave variance in winter and an anti phase relationship in summer this is consistent with the theory of filtering by tidal winds acting on a zonally asymmetric gravity wave field in which westward waves dominate in winter and eastward waves dominate in summer the limitations of the technique and the effect this has on the interpretation of these results are also considered the effects of the diurnal cycles in meteor count rates the uncertainty in recorded radial velocities and the uncertainty in the measured heights of meteors are considered

comparison of models for estimating uniaxial compressive strength of some sedimentary rocks from qom formation to estimate uniaxial compressive strength of some sedimentary rock types from a set of index test results selected soft computing methods were employed consequent comparative performances of these methods were also evaluated some selected sedimentary rock types i e grainstone wackestone mudstone boundstone gypsum and silty marl collected from the qom formation in the vicinity of qom city central iran were examined four indices i e block punch index point load strength schmidt hammer rebound number and ultrasonic p wave velocity and uniaxial compressive strength ucs of these samples were determined a multidisciplinary approach including multiple linear regression analysis fuzzy inference system artificial neural network and adaptive neuro fuzzy inference system based models were used to estimate ucs from these index test results various statistical parameters vaf rmse and r 2 were determined to check the predictive performances of these models the rmse vaf and r 2 values for anfis model were 0 99 3 77 and 0 99 respectively in a comparative sense anfis gives better predictive results accordingly this method is being inferred as a predictive approach to estimate preliminary rock engineering purposes in comparison with alternate methods

radiocarbon evidence for decomposition of aged organic matter in the vadose zone as the main source of speleothem carbon 2015 elsevier ltd several recent studies have used records of the radiocarbon 14c bomb peak in speleothems to inversely model the soil a 14co 2 and the age distribution of soil organic material som above caves in part to investigate the potential of speleothems as sensitive records of past som dynamics the results of these modeling studies have suggested that soil co 2 at karst sites is derived primarily from the decomposition of som with turnover times on the order of decades to centuries this result is in stark contrast with observations of soil a 14co 2 at non karst sites which indicate that soil co 2 is derived primarily from root respiration and decomposition of som with much shorter turnover times this discrepancy suggests that som in karst settings may have a very different age distribution than sites that have been studied previously and or that soil co 2 is not the main source of speleothem carbon to help resolve this discrepancy we present an improved inverse model which we use to estimate the age of co 2 above several caves we also present results from a detailed case study of soil carbon dynamics at heshang cave china this work demonstrates that som in karst sites may be much older than som in non karst soils that have been studied previously but that co 2 produced in the shallow soil zone is unlikely to be the main source of speleothem carbon a review of the literature suggests that the most likely explanation for the aforementioned discrepancy is that decomposition of down washed som in the vadose zone is the dominant source of speleothem carbon

atmospheric tide 2 the solar and lunar semidiurnal components solar and lunar semidiurnal wind and temperature oscillations from the surface to 400 km are simulated for average solar activity conditions utilizing the numerical tidal model described in part 1 hough mode decomposition of the solstitial solar semidiurnal tide excited by h2o and o3 insolation absorption below 80 km indicates that it is characterized by a predominance of 2 2 below 60 km about equal contributions of 2 2 2 3 and 2 4 between 70 and 90 km mostly 2 4 with some 2 5 and 2 2 between 90 and 120 km and a predominance of 2 2 above 140 km with secondary contributions from 2 3 and 2 5 the solstitial lunar semidiurnal tide is characterized by a predominance of 2 2 below 70 km 2 4 with secondary contributions from 2 2 2 3 and 2 5 between 80 and 110 km and by 2 2 with a fairly strong secondary contribution from 2 3 above 120 km similar descriptions for both the solar and lunar oscillations apply at equinox except that the asymmetric 2 3 and 2 5 modes are absent relative to the solar component lunar temperature and wind amplitudes are sufficiently large 20 in the lower and upper thermosphere to account for some of the observed variability previously attributed to the solar tide amplitudes of the 2 4 and 2 5 modes above 100 km are significantly affected by mesospheric eddy diffusion coefficients in excess of 2 106 cm s 1 the total solar semidiurnal exospheric temperature oscillation for average solar conditions ranges from 10 20 k poleward of 40 n to 40 60 k equatorward of 30 n and has its origin in three sources of excitation all of comparable importance 1 euv solar radiation absorption in the lower thermosphere 100 200 km 2 in situ momentum coupling due to the interaction of diurnal winds and diurnally varying ion drag and 3 tides propagating upwards from below 100 km in addition the calculations are compared with rocket meteor radar partial reflection thomson scatter and satellite data to evaluate the consistency of the model with observations

radar observations of longitudinal variability of tidal planetary waves and mean motions in the tropical mesosphere during the summer of 1995 two mf radars located at hawaii and puerto rico were in operation to measure mesospheric motions we use the data obtained at the two sites to study the longitudinal variability of mean winds planetary waves and tides on average the winds at puerto rico were more westward and equatorward than those at hawaii quasi 2 day planetary wave activity was evident most of the time from june 28 to july 25 the quasi 2 day wave had a zonal wave number m of 3 during one occasion and 4 during another and the periods of the two planetary waves were 56 and 48 hours respectively the diurnal tide at puerto rico was stronger than that at hawaii above 86 km and the semidiurnal tide at hawaii was strongly damped in the altitude range of 90 98 km both the semidiurnal and the diurnal tides were apparently modulated by longer period waves which was perhaps the most important factor in accounting for their large spatial and temporal variability the phase difference at the two sites deviates considerably from the expectation of purely migrating tides

role of mixing corrosion in calcite aggressive h2o co2 caco3 solutions in the early evolution of karst aquifers in limestone two cave forming mechanisms in limestone are discussed currently first when two h2o co2 caco3 solutions saturated with respect to calcite but with different chemical compositions mix renewed aggressiveness to limestone dissolution occurs this process called mixing corrosion bogli 1964 1980 in combination with linear dissolution kinetics has been suggested as cave forming second it has been shown that solely the action of nonlinear dissolution kinetics can generate extended karst conduits this paper combines both mechanisms by digital modeling of the evolution of the aperture widths of a confluence of two fractures into a third one it is shown that the first mechanism does not create large cave conduits the combination of mixing corrosion and nonlinear kinetics however considerably intensifies karstification compared to that of nonlinear kinetics solely the times to terminate early evolution of karst are significantly reduced when the co2 concentrations of the inflowing solutions differ by no more than 30 we discuss the underlying mechanisms by inspection of the time dependence of the evolution of aperture widths flow rates through them and of the renewed undersaturation of the mixed solution at the confluence of two fractures finally the evolution of a karst aquifer on a two dimensional percolation network is modeled when mixing corrosion is present and compared to that on an identical net with identical nonlinear dissolution kinetics but mixing corrosion excluded large differences in the morphology of the net of cave conduits are found and also a reduction of the time of their evolution from these findings we conclude that climatic changes which influence the pco2 in the soil can divert the evolving cave patterns

minimum hydrochemical conditions allowing limestone cave development early theoretical investigations into initiation of limestone cave development suggested that water entering small fractures approaches saturation within a short distance and thus appeared to be unable to produce much further enlargement of these fractures the answer to this problem seems to be white s 1977 kinetic trigger idea emphasizing the precipitous drop in dissolution rates as equilibrium is approached however minimum conditions of flow rate passage geometry and initial co2 concentration may exist below which the waters will so nearly achieve saturation that caves will be unable to develop modeling results indicate that under geologically reasonable pco2 and head gradient values the minimum initial aperture widths in which caves will develop is of the order of 100 m initial apertures wider than about 500 m will form passages very easily even under low head gradients there will thus be strong differential selection among initial flow paths with regard to cavern passage development

ann based inversion of dc resistivity data for groundwater exploration in hard rock terrain of western maharashtra india summary inversion of vertical electrical sounding ves data especially from the crystalline hard rock area assumes a special significance for groundwater exploration here we used a newly developed algorithm based on the bayesian neural network bnn theory combined with hybrid monte carlo hmc markov chain monte carlo mcmc simulation scheme to invert the direct current dc ves measurements obtained from 30 locations around tenduli vengurla sindhudurg district maharashtra india the inversion results suggest that the top layer is mostly comprised of laterites followed by mixture of clay clayey sand and garnulites granite as basement rocks the source of groundwater appears to be accessible in weathered semi weathered layer of laterite clayey sand that exists within the depth of 10 15 m from the surface the nw se trending major lineaments and its criss crosses are also identified from the apparent and true resistivity surface map the pseudo section at different depths in the western part of the area near nivti shows extensive influence of saltwater intrusion and its impact reaching up to the depth of 30 m from the surface along the coastal area our results also show that intrusion of saline water decreases from the western part to the eastern part of the region two dimensional modeling of four resistivity profiles from the study region identified two potential groundwater reservoirs one lying between path tenduli and another in between mat and zaraph the deduced true electrical resistivity section against depth correlates well with available borehole lithology in the area the results presented here would be useful for interpreting the geological signatures like fractures major joints and lineaments which in turn will be helpful for identifying groundwater reservoirs and drainage pattern in the crystalline hard rock area the newly developed hmc based bnn method is robust and would provide insights for constraining the geophysical models and criteria for modeling resistivity data

quasi 16 day oscillation in the mesosphere and lower thermosphere a quasi 16 day wave in the mesosphere and lower thermosphere is investigated through analyses of radar data during january february 1979 and through numerical simulations for various background wind conditions previous workers have examined about 19 days of tropospheric and stratospheric data during january 10 28 1979 and present conflicting evidence as to whether a large westward propagating wavenumber 1 oscillation observed during this period can be identified in terms of the second symmetric rossby normal mode of zonal wavenumber 1 commonly referred to as the 16 day wave in the present work we have applied spectral analysis techniques to meridional and zonal winds near 95 km altitude obtained from radar measurements over obninsk russia 54 n 38 e and saskatoon canada 52 n 107 w these data reveal oscillations of the order of 10 m s 1 with a period near 16 days as well as waves with periods near 5 and 10 days these periodicities all correspond to expected resonant frequencies of atmospheric disturbances associated with westward propagating free rossby modes of zonal wavenumber 1 numerical simulations are performed which demonstrate that the 95 km measurements of the 16 day wave are consistent with upward extension of the oscillation determined from the tropospheric and stratospheric data noteworthy features of the model in terms of its applicability in the mesosphere lower thermosphere regime are explicit inclusion of eddy and molecular diffusion of heat and momentum and realistic distributions of mean winds especially between 80 and 100 km the latter include a westerly wind regime above the summer easterly mesospheric jet thus providing a ducting channel enabling interhemispheric penetration of the winter planetary wave disturbance this serves to explain the appearance of a quasi 16 day wave recently reported in the high latitude summer mesopause williams and avery 1992 however the efficiency of this interhemispheric coupling may be reduced by gravity wave stress no significant penetration of the 16 day oscillation above about 100 km is predicted by the model reported signatures of a 16 day periodicity in ionospheric data therefore require modulation of tidal or gravity wave accessibility to the thermosphere or perhaps in situ excitation

two day wave structure and mean flow interactions observed by radar and high resolution doppler imager data obtained with four mf and meteor radars at equatorial and subtropical sites and with the high resolution doppler imager hrdi instrument aboard the uars satellite were used to examine the structure wave mean flow interactions and potential sources of the 2 day wave in the middle atmosphere during three southern hemisphere summers the three wave events were highly transient having typical durations of 20 to 30 days and exhibiting modulation at shorter periods temporal variations were found to exhibit good correlations between radar and hrdi data radar and hrdi data were used to estimate those components of the eliassen palm flux that could be assessed with these data meridional fluxes of momentum and heat were computed using hrdi data and agree reasonably with the momentum fluxes computed from radar data at discrete locations these fluxes were found to exhibit consistent latitudinal structures each year suggesting systematic wave excitation and wave mean flow interactions meridional momentum flux gradients were seen to be anticorrelated with zonal wind accelerations in a manner consistent with wave forcing of the large scale circulation the apparent wave mean flow interactions suggest that the 2 day wave could be a transient response to baroclinic instability of the summer hemisphere mesospheric jet a calculation of the meridional gradient of quasi geostrophic potential vorticity using hrdi winds and the cospar international reference atmosphere cira 1986 temperatures exhibits a region of instability in the lower and middle mesosphere extending into subtropical latitudes and provides additional evidence of a possible source of this motion via baroclinic instability of the summer hemisphere jet structure

mean winds and the semiannual oscillation in the mesosphere and lower thermosphere at christmas island in this paper we analyze mesospheric wind data collected from august 1988 to november 1989 and january 1991 to december 1991 at christmas island 1 95 n 157 30 w using the meteor echo detection and collection system a brief overview of the data analysis techniques used on these data sets and meteor arrival statistics are presented the mean winds are computed for 80 to 100 km and compared with the cira 86 model of mesospheric equatorial mean winds examination of the zonal mean winds and a fourier decomposition of the zonal wind field shows a strong semiannual oscillation sao to determine the vertical characteristics of the zonal sao a least squares fit was computed at each height the results show a semiannual oscillation that peaks in amplitude at 84 km and decreases with increasing height the sao at christmas island is compared with data collected at ascension island and kwajalein island and with the cira 86 model this comparison shows good phase agreement between the sites and some variability in the amplitudes to fully understand the sao in the context of the theory presented by delisi and dunkerton 1988 the tropospheric mean winds and wind variances are computed to determine the extent of tropospheric gravity wave activity present finally the amplitude and phase of the sao in temperature are computed indirectly from the christmas island wind data and compared to temperature results from sme data our results show reasonable agreement below 87 km and a divergence in amplitude near 90 km one probable reason for this difference is contamination of the sme data from the diurnal tide as noted by garcia and clancy 1990

dynamics of the equatorial mesosphere first results with a new generation partial reflection radar the first observations of mesospheric winds made between january august 1990 with an mf partial reflection radar located on christmas island 2 n 157 w in the central pacific are described the mean zonal winds are in general westward but show clear evidence for a wave driven circulation power spectral studies indicate that waves are present over a wide range of periods ultra fast kelvin waves are especially evident in january march with peak amplitudes 20 ms 1 and intrinsic phase speeds of 150 ms 1 indicated the kelvin waves are estimated to contribute an eastward acceleration of up to 10 ms 1 day 1 gravity wave amplitudes are also found to be almost as large as those observed at mid latitude sites which suggests that convection is a major source of gravity wave activity

mean winds tides and gravity waves during the westward phase of the mesopause semiannual oscillation msao mf radar observations of mean winds tides and gravity waves in the period range 30 120 min over tirunelveli 8 7 n 77 8 e during april 1993 when the mesopause semiannual oscillation msao was in the westward phase are presented in this work the focus herein is on the observed relationship between these dynamical parameters which is explained in the context of the current understanding of the behavior of msao winds tidal dissipation and gravity wave tide interactions the observed diurnal tide amplitude and phase variations with height indicate 1 1 wave damping and subsequent westward momentum deposition the gravity wave variances are shown to be modulated by the diurnal tide though the analysis does not lead to an estimation of gravity wave contributions to the time mean zonal flow and its shears the observations do suggest that the short term tidal variability contributes either directly or indirectly through the gravity wave tidal interactions to the variation of the strength of the time mean westward flow associated with the msao

the effect of the sampling strategies on the landslide susceptibility mapping by conditional probability and artificial neural networks this study presented herein compares the effect of the sampling strategies by means of landslide inventory on the landslide susceptibility mapping the conditional probability cp and artificial neural networks ann models were applied in sebinkarahisar giresun turkey digital elevation model was first constructed using a geographical information system software and parameter maps affecting the slope stability such as geology faults drainage system topographical elevation slope angle slope aspect topographic wetness index stream power index and normalized difference vegetation index were considered in the last stage of the analyses landslide susceptibility maps were produced applying different sampling strategies such as scarp seed cell and point the maps elaborated were then compared by means of their validations scarp sampling strategy gave the best results than the point whereas the scarp and seed cell methods can be evaluated relatively similar comparison of the landslide susceptibility maps with known landslide locations indicated that the higher accuracy was obtained for ann model using the scarp sampling strategy the results obtained in this study also showed that the cp model can be used as a simple tool in assessment of the landslide susceptibility because input process calculations and output process are very simple and can be readily understood

numerical models for mixing corrosion in natural and artificial karst environments 1 the enlargement of initially small fractures in a karst aquifer by chemical dissolution is studied flow in the aquifer is driven by head differences between sinks and resurgences and flow depends on the permeability of small fissures and fractures in the aquifer enlargement of fractures is controlled by the chemical composition of the recharge as water undersaturated with respect to calcite is able to dissolve material from the fracture walls as fractures are enlarged with time permeability within the aquifer increases significantly and flow becomes very heterogeneous two different processes are considered enlargement due to normal corrosion where water is undersaturated with respect to calcite and enlargement due to mixing corrosion where two solutions saturated with respect to calcite but with different carbon dioxide concentrations mix and the resulting solution becomes undersaturated again the importance of mixing corrosion is discussed for two boundary conditions a natural karst aquifer is modeled with fixed recharge boundary conditions representing sinking streams and an artificial karst aquifer is simulated with fixed head boundary conditions representing a reservoir in both cases mixing corrosion is important especially if recharge is characterized by an almost saturated chemistry mixing corrosion significantly changes the evolving passage pattern as dissolution due to mixing of solutions is possible deep in the aquifer mixing corrosion also reduces breakthrough times of the aquifer and can result in dramatic leakage underneath dam sites even if the impounded water is almost saturated with respect to calcite

tidal signatures in temperature data from crista 1 mission temperature measurements in the stratosphere and mesosphere were taken during the first cryogenic infrared spectrometers and telescopes for the atmosphere crista 1 mission using co2 emissions these measurements range from 13 to close to 100 km and individual temperature measurements have a precision of 1 k the crista orbit was circular at an inclination of 57 so local time variations during the 7 day mission were small for a given latitude and orbit leg zonal averages of the data show significant structure in the vertical and as a function of latitude temperature differences between the zonal mean data from the ascending and descending portions of the orbit are of the form expected from the diurnal tide the maximum zonal mean difference is 20 k and occurs over the equator at an altitude of 75 km zonal variations in the temperature difference indicate that the tidal amplitude is not uniform at all longitudes at the equator the maximum amplitude 30 k appears over the african sector and the minimum 10 k over the pacific sector this variation is most likely a nonmigrating wavenumber 2 diurnal tide although other less plausible possibilities exist to facilitate comparisons with model results the temperature variations are converted to equivalent vertical displacements assuming the tidal motions are adiabatic such an approach is appropriate in the mesosphere where diurnal variations due to radiative effects are small and reduces the dependence of the measured temperature amplitude on the background temperature profile equivalent vertical displacements are also calculated using results from the global scale wave model for the most part the model results and observations are in excellent qualitative and good quantitative agreement from the tropopause to the mesopause however the observed vertical wavelength is smaller and its amplitude in terms of equivalent displacement is smaller in the upper mesosphere than that in the model the decrease in amplitude is consistent with that expected from the transition from equinox to solstice conditions

climatology of mesospheric gravity wave activity over urbana illinois 40 n 88 w a 5 year 1991 1995 climatology of mesospheric gravity wave activity observed with the urbana medium frequency mf radar is presented we focus on the monthly mean horizontal wind variances associated with gravity waves with observed periods between 10 min and 8 hours these results are compared with the seasonal characteristics from other gravity wave observations the total wave variance displays a dominant semiannual variation maxima summer winter minima spring fall below 87 km with little seasonal variation above 87 km the zonal wave variance exceeds the meridional wave variance except around regions of zonal wind reversal in all seasons the observed variance scale height is greater than that of a nondissipating wave field a simple zero mean wind model based on linear saturation theory is found to be inadequate in reproducing the seasonal characteristics of the observed wave variances an alternative model based on critical layer filtering by a height dependent wind field can reproduce the observed semiannual oscillation in the wave variance given a specific source input

application of integrated arima and rbf network for groundwater level forecasting the combination model of autoregressive integrated moving average arima and radial basis function network rbfn is used for the prediction of monthly groundwater level the arima model is used to estimate the linear principal of time series and the rbfn model is used to predict the nonlinear residuals the proposed hybrid model is applied to forecast the monthly groundwater level fluctuations for two observation wells in the city of xi an china the monthly groundwater level data from the year 1998 to 2008 are used for training the applied models and the data from the year 2009 to 2010 are reserved for testing predicted data from the hybrid model are compared with those from the arima model and rbfn model using the accuracy measures the result shows that the proposed hybrid model has both the good linear fitting ability of arima model and the great nonlinear mapping ability of rbfn model the prediction accuracy rate is higher than that of any single model therefore the application of the combination model in the prediction of groundwater level is effective and feasible

interstation correlation of high latitude lower stratosphere gravity wave activity evidence for planetary wave modulation of gravity waves over antarctica 1 four years of operational radiosonde balloon flights from three australian stations in eastern antarctica casey 66 3 s 110 0 e davis 68 6 s 78 0 e and mawson 67 6 s 62 9 e are analyzed to derive lower stratosphere 12 20 km altitude gravity wave information from perturbations in wind and temperature gravity wave activity and seasonal behavior was found to be similar to that seen in earlier studies from antarctica interstation comparisons of zonal wind and gravity wave activity showed very high correlations throughout the entire data set between mawson and davis stations 600 km distant with a lag near 0 5 days the correlations between casey and davis 1400 km apart were lower but still significant with a lag near 1 day there is no significant correlation between stratospheric gravity wave activity and surface winds our results suggest a pattern of winds and waves moving eastward over the stations with a speed near 15 m s 1 as this is comparable to planetary wave speeds we interpret our results as being evidence for a significant planetary wave induced modulation of the zonal wind and the gravity wave field although we are unable to identify the mechanism by which this operates our work suggests that the high latitude lower stratosphere gravity wave fields are relatively uniform on spatial scales of 500 1000 km and on timescales of around 0 5 1 days

drake antarctic agile meteor radar first results configuration and comparison of mean and tidal wind and gravity wave momentum flux measurements with southern argentina agile meteor radar 1 a new generation meteor radar was installed at the brazilian antarctic comandante ferraz base 62 1 s in march 2010 this paper describes the motivations for the radar location its measurement capabilities and comparisons of measured mean winds tides and gravity wave momentum fluxes from april to june of 2010 and 2011 with those by a similar radar on tierra del fuego 53 8 s motivations for the radars include the hotspot of small scale gravity wave activity extending from the troposphere into the mesosphere and lower thermosphere mlt centered over the drake passage the maximum of the semidiurnal tide at these latitudes and the lack of other mlt wind measurements in this latitude band mean winds are seen to be strongly modulated at planetary wave and longer periods and to exhibit strong coherence over the two radars at shorter time scales as well as systematic seasonal variations the semidiurnal tide contributes most to the large scale winds over both radars with maximum tidal amplitudes during may and maxima at the highest altitudes varying from 20 to 70 ms 1 in contrast the diurnal tide and various planetary waves achieve maximum winds of 10 to 20 ms 1 monthly mean gravity wave momentum fluxes appear to reflect the occurrence of significant sources at lower altitudes with relatively small zonal fluxes over both radars but with significant and opposite meridional momentum fluxes below 85 km these suggest gravity waves propagating away from the drake passage at both sites and may indicate an important source region accounting in part for this hotspot

gregarious tropical convection abstract a beat source with a vertical profile like that of observed tropical mesoscale convective systems mcss is shown to cause through inviscid gravity wave dynamics upward displacement at low levels in a mesoscale region surrounding the heating typical values are 10 30 area contraction at the surface everywhere within 270 km of the heating 6 h after it starts as a result conditions near an existing mcs but beyond the area of mcs outflow become more favorable for the development of additional convection this theory predicts that cloud clusters should be gregarious infrared satellite imagery confirms that almost half of the cold cloudiness observed in a month over the oceanic warm pool region was contributed by just 14 objectively defined multiday supercluters

observations of the diurnal tide from space abstract this study presents a climatology of mesospheric and lower thermospheric diurnal tidal winds obtained with the high resolution doppler imager hrdi on the upper atmosphere research satellite uars the observations reveal that although tidal structures are present at all times like the prevailing zonal winds they exhibit significant semiannual as well as other shorter term variations in amplitude results are presented for a period extending over more than one year from november 1991 to july 1993 the 1 1 diurnal tidal amplitude of the meridional component characterized by the value at an altitude of 90 km and a latitude of 22 ranges from a minimum at solstice of less than 20 m s 1 to an equinox maximum of over 70 m s 1 the vertical wavelength and phase of the tide show only slight variations throughout the year with a suggestion of semiannual variations in both

a three year gravity wave climatology of the mesosphere and lower thermosphere over kauai a 3 year study of gravity wave variability covering 1991 1992 and 1993 was conducted using horizontal wind measurements collected by a partial reflection mf radar located on the island of kauai hawaii 22 n 160 w high echo return rates between 70 and 98 km provided ample time resolution for the study of gravity wave variability in this height range horizontal wind measurements were band pass filtered for periods between 20 min and 6 hours establishing a gravity wave band time series gravity wave variance and polarization calculations were carried out over various time frames and examined with regard to their response to season and background environment among the more interesting observed phenomena were the annual and semiannual oscillations in the gravity wave variances a significant diurnal and semidiurnal variability in the variances and an extended enhancement of these variances during the latter half of 1992 and the beginning of 1993

equatorial dynamics observed by rocket radar and satellite during the cadre malted campaign 2 mean and wave structures coherence and variability we present an analysis of the wind and temperature measurements made by rocket radar and satellite instrumentation in the equatorial and subtropical middle atmosphere accompanying the malted cadre campaign conducted at alcantara brazil during august 1994 measured mean winds and temperatures extended from 10 to 110 km exhibited general consistency between instruments and revealed an oscillatory nature of the mean zonal wind with altitude at equatorial latitudes mf radar measurements of tidal structures showed these to exhibit variability on 8 and 16 day periods but to be largely uncorrelated in time two day wave structures displayed the same periodicities but were well correlated among sites at northern and equatorial latitudes rocket and radar measurements at smaller scales of motion revealed inertia gravity waves having significant temporal coherence quadrature correlations between components indicating clear directions of propagation and momentum flux and mean wind correlations indicative of gravity wave filtering processes rocket estimates of diurnal tidal amplitudes suggest that the diurnal tide achieves convectively unstable amplitudes in the upper equatorial mesosphere

tides in the mesopause region over fort collins colorado 41 n 105 w based on lidar temperature observations covering full diurnal cycles 1 eighteen sets of 24 hour continuous lidar temperature observation well distributed throughout the year have been analyzed to reveal the mean amplitude and phase of oscillations with 24 12 8 and 6 hour periods for four seasons the amplitude and phase of both 24 and 12 hour components are compared to the prediction of the most recent global scale wave model gswm 00 the variability of diurnal and semidiurnal oscillations is examined by comparing the amplitude and phases of each observed day in autumn winter and spring even with the limited data sets reported here surprisingly good general agreement between the observed and model tidal phases can be established implicating the prevalence of migrating diurnal and semidiurnal tides compared to the diurnal and semidiurnal phases which typically show clear downward phase progression the 8 and 6 hour components exhibit small amplitude and show unorganized phase propagation as a function of altitude the advantage of having coverage over complete diurnal cycle and entire mesopause altitudes as demonstrated here would hopefully stimulate future tidal studies with lidar temperature and zonal and meridional wind observations

medium frequency radar studies of gravity wave seasonal variations over hawaii 22 n 160 w 1 using simple numerical filters estimates of wind variances with period bands of 0 1 to 1 hour and 1 to 5 hours have been derived from data taken with the medium frequency radar on the island of kauai hawaii 22 n 160 w the observations cover altitudes of 70 to 90 km and extend over the years 1990 2000 the results show seasonal and interannual variations of the wind variances which can be attributed to atmospheric gravity waves the mean zonal wind has mainly an annual variation below an altitude of 83 km and a semiannual variation above the gravity waves have maximum intensity at the solstices below 83 km but at higher altitudes the times of the maxima shift to the equinoxes numerical simulations suggest this behavior results from the dependence of gravity wave generation and propagation on the background wind and temperature

nonmigrating diurnal tides in the equatorial middle atmosphere abstract data from the nimbus 7 limb infrared monitor of the stratosphere lims are used to extend the analysis of diurnal tides in the middle atmosphere to include the zonally symmetric and eastward propagating components these modes show vertical and meridional structures that are generally consistent with the predictions of linear tidal theory the zonal and meridional wind fields are calculated from the tidal temperatures diurnal perturbations in lims temperature and derived winds agree well with equinoctial model calculations comparisons with day night differences of radiosonde temperature and rocket winds show qualitative agreement in vertical structure and amplitude the zonally symmetric and eastward migrating tidal components show a higher degree of temporal variability than the sun synchronous component these modes at times contribute substantially to the diurnal signal in wind and temperature with combined amplitudes equal to or in excess of the amplitude of the main migrating diurnal tid

vadose co2 gas drives dissolution at water tables in eogenetic karst aquifers more than mixing dissolution most models of cave formation in limestone that remains near its depositional environment and has not been deeply buried i e eogenetic limestone invoke dissolution from mixing of waters that have different ionic strengths or have equilibrated with calcite at different pco2 values in eogenetic karst aquifers lacking saline water mixing of vadose and phreatic waters is thought to form caves we show here calcite dissolution in a cave in eogenetic limestone occurred due to increases in vadose co2 gas concentrations and subsequent dissolution of co2 into groundwater not by mixing dissolution we collected high resolution time series measurements 1 year of specific conductivity spc temperature meteorological data and synoptic water chemical composition from a water table cave in central florida briar cave we found spc pco2 and calcite undersaturation increased through late summer when briar cave experienced little ventilation by outside air and decreased through winter when increased ventilation lowered cave co2 g concentrations we hypothesize dissolution occurred when water flowed from aquifer regions with low pco2 into the cave which had elevated pco2 elevated pco2 would be promoted by fractures connecting the soil to the water table simple geochemical models demonstrate that changes in pco2 of less than 1 along flow paths are an order of magnitude more efficient at dissolving limestone than mixing of vadose and phreatic water we conclude that spatially or temporally variable vadose co2 g concentrations are responsible for cave formation because mixing is too slow to generate observed cave sizes in the time available for formation while this study emphasized dissolution gas exchange between the atmosphere and karst aquifer vadose zones that is facilitated by conduits likely exerts important controls on other geochemical processes in limestone critical zones by transporting oxygen deep into vadose zones creating redox boundaries that would not exist in the absence of caves copyright 2014 john wiley sons ltd