subsurface flow in a soil mantled subtropical dolomite karst slope a field rainfall simulation study abstract soil and epikarst co evolve resulting in complex structures but their coupled structural effects on hydrological processes are poorly understood in karst regions this study examined the plot scale subsurface flow characteristics from an integrated soil epikarst system perspective in a humid subtropical cockpit karst region of southwest china a trench was excavated to the epikarst lower boundary for collecting individual subsurface flows in five sections with different soil thicknesses four field rainfall simulation experiments were carried out under different initial moisture conditions dry and wet and rainfall intensities 114 mm h 1 high and 46 mm h 1 low on average the soil epikarst system was characterized by shallow soil overlaying a highly irregular epikarst surface with a near steady infiltration rate of about 35 mm h 1 the subsurface flows occurred mainly along the soil epikarst interface and were dominated by preferential flow the subsurface flow hydrographs showed strong spatial variability and had high steady state coefficients 0 52 and 0 36 for high and low rainfall intensity events irregular epikarst surface combining with high vertical drainage capacity resulted in high threshold rainfall depths for subsurface flows 67 mm and 263 mm for initial wet and dry conditions respectively the above results evidenced that the irregular and permeable soil epikarst interface was a crucial component of soil epikarst architecture and consequently should be taken into account in the hydrological modeling for karst regions

observation of glacial isostatic adjustment in stable north america with gps 1 motions of three hundred and sixty global positioning system gps sites in canada and the united states yield a detailed image of the vertical and horizontal velocity fields within the nominally stable interior of the north american plate by far the strongest signal is the effect of glacial isostatic adjustment gia due to ice mass unloading during deglaciation vertical velocities show present day uplift 10 mm yr near hudson bay the site of thickest ice at the last glacial maximum the uplift rates generally decrease with distance from hudson bay and change to subsidence 1 2 mm yr south of the great lakes the hinge line separating uplift from subsidence is consistent with data from water level gauges along the great lakes showing uplift along the northern shores and subsidence along the southern ones horizontal motions show outward motion from hudson bay with complex local variations especially in the far field although the vertical motions are generally consistent with the predictions of gia models the horizontal data illustrate the need and opportunity to improve the models via more accurate descriptions of the ice load and laterally variable mantle viscosity

submerged karst landforms observed by multibeam bathymetric survey in nagura bay ishigaki island southwestern japan abstract submerged tropical karst features were discovered in nagura bay on ishigaki island in the southern ryukyu islands japan the coastal seafloor at depths shallower than 130 m has been subjected to repeated and alternating subaerial erosion and sedimentation during periods of quaternary sea level lowstands we conducted a broadband multibeam survey in the central area of nagura bay 1 85 2 7 km and visualized the high resolution bathymetric results over a depth range of 1 6 58 5 m various types of humid tropical karst landforms were found to coexist within the bay including fluviokarst doline karst cockpit karst polygonal karst uvalas and mega dolines although these submerged karst landforms are covered by thick postglacial reef and reef sediments their shapes and sizes are distinct from those associated with coral reef geomorphology the submerged landscape of nagura bay likely formed during multiple glacial and interglacial periods according to our bathymetric results and the aerial photographs of the coastal area this submerged karst landscape appears to have developed throughout nagura bay i e over an area of approximately 6 5 km and represents the largest submerged karst in japan

a new ice thickness and bed data set for the greenland ice sheet 1 measurement data reduction and errors ice thickness data collected between 1993 and 1999 using a coherent ice penetrating radar system developed at the university of kansas have been combined with data collected by the technical university of denmark in the 1970s to produce a new ice thickness grid for greenland crossover analysis was used to assess the relative accuracy of the two data sets and they were weighted accordingly and interpolated onto a regular 5 km spacing grid using a kriging interpolation procedure a high resolution land ice mask was used to help constrain the interpolation of the ice thickness data near the ice sheet margins where in the past the relative errors have been largest the ice thickness grid was combined with a new digital elevation model of the ice sheet and surrounding rock outcrops to produce a new bed elevation data set for the whole of greenland the ice thickness grid was compared with the currently available data set differences in the center of the ice sheet where the ice is thickest were of the order of a few percent near the margins however large differences of as much as a factor of 10 were found the total volume of ice contained in the ice sheet was reestimated and found to have a value of 2 93 x 10 6 km 3 the ice thickness grid was used to calculate the spatial pattern of gravitational driving stress over the ice sheet anomalous patterns of stress were found in areas that appeared to be associated with areas of rapid flow

monsoon convection in the himalayan region as seen by the trmm precipitation radar three dimensional structure of summer monsoon convection in the himalayan region and its overall variability are examined by analyzing data from the tropical rainfall measuring mission trmm precipitation radar over the june september seasons of 2002 and 2003 statistics are compiled for both convective and stratiform components of the observed radar echoes deep intense convective echoes 40 dbz echo reaching heights 10 km occur primarily just upstream south of and over the lower elevations of the himalayan barrier especially in the northwestern concave indentation of the barrier the deep intense convective echoes are vertically erect consistent with the relatively weak environmental shear they sometimes extend above 17 km indicating that exceptionally strong updraughts loft graupel to high altitudes occasionally scattered isolated deep intense convective echoes occur over the tibetan plateau wide intense convective echoes 40 dbz echo 1000 km2 in horizontal dimension also occur preferentially just upstream of and over the lower elevations of the himalayas most frequently in the northwestern indentation of the barrier the wide intense echoes have an additional tendency to occur along the central portion of the himalayas and they seldom if ever occur over the tibetan plateau the wide intense echoes exhibit three mesoscale structures amorphous areas lines parallel to the mountain barrier and arc shaped squall lines perpendicular to and propagating parallel to the steep himalayan barrier the latter are rare generally weaker than those seen in other parts of the world and occur when a midlevel jet is aligned with the himalayan escarpment deep and wide intense convective echoes over the northwestern subcontinent tend to occur where the low level moist layer of monsoon air from the arabian sea meets dry downslope flow in a manner reminiscent of severe convection leeward of the rocky mountains in the central usa as the low level layer of moist air from the sea moves over the hot arid northwestern subcontinent it is capped by an elevated layer of dry air advected off the afghan or tibetan plateau the capped low level monsoonal airflow accumulates instability via surface heating until this instability is released by orographically induced lifting immediately adjacent to or directly over the foothills of the himalayas broad 50 000 km2 in area stratiform echoes occur in the eastern and central portions of the himalayan region in connection with bay of bengal depressions their centroids are most frequent just upstream of the himalayas in the region of the concave indentation of the barrier at the eastern end of the range the steep topography apparently enhances the formation and longevity of the broad stratiform echoes monsoonal depressions provide a moist maritime environment for the convection evidently allowing mesoscale systems to develop larger stratiform echoes than in the western himalayan region copyright 2007 royal meteorological society

evaluation of electrical resistivity tomography ert for mapping the soil rock interface in karstic environments rocky desertification is a significant threat in the karst regions of southwest china studies of soil distribution can contribute to protecting and recovering the fragile karst ecosystem that is prevalent in this region with an underlying aim of being able to assess soil stocks in karstic environments this study evaluates the use of electrical resistivity tomography ert for delineating the soil rock interface using a synthetic model that recognizes the three dimensional nature of the subsurface experiments are performed to assess the impact of measurement errors and measurement configuration on recovery of the interface the inverted results show that the accuracy of the delineation of the soil rock interface decreases with the increase of measurement error and dipole spacing the results also show the importance of reliable estimation of measurement errors field based applications of ert at five exposed profiles in southwest china are also reported for the field data three dimensional modelling was necessary to account for the exposed face the field experiments show that ert can be effective at delineating the interface between soil and bedrock but resolution can be limited due to the scale of features or lack of contrast between soil and bedrock the method shows great promise as a means of assessing in a non invasive manner the soil bedrock interface and perhaps more significantly quantifying estimates of total soil stocks as we seek to quantify the vulnerability or resilience of this important landscape to anthropogenic and natural stresses

origin of the term karst and the transformation of the classical karst kras the limestone region northeast of trieste bay is named kras in slovenian karst in german and carso in italian from a pre indo european word karra meaning stony the natural vegetation was deciduous forest clearance and burning to create pasture for sheep began in the first millenium bc and resulted in considerable losses of soil into underground karstic channels by the middle ages the region was known as a rocky treeless land the first legislation to conserve or re establish forests was passed but it did not succeed in the 19th century the regional name came to be adopted as the generic name for all dissolutional landscapes and hydrogeological systems whether natural or modified during this period a change from sheep rearing to dairying with cattle plus new legislation and experimental plantings with black pine pinus nigra began the restoration of the forests in the karst itself since 1945 their extent has more than doubled again partly as consequences of rural depopulation and the banning of goats approximately 50 percent of the region is now covered by woodlands soil erosion is much reduced but evapotranspiration losses have probably increased it is hypothesized that there will be effects of restoration upon such karstic parameters as the discharge of springs or rates of travertine deposition in the caves

erosion creep collapse mechanism of underground soil loss for the karst rocky desertification in chenqi village puding county guizhou china carbonate rocks distribute widely in china the total area of the carbonate rocks is about 3 430 000 km 2 and the exposed area of the carbonate is approximately 13 of china s territory in 2003 soil loss in yunnan guizhou and guangxi provinces reached 179 600 km 2 which is almost 40 1 of the total area causing rocky desertification in this study the erosion creep collapse mechanism of underground soil loss for the karst rocky desertification in chenqi village puding county guizhou province is proposed the mechanism occurs under the following geological environment slope surface undulation underlying bedrock surface fluctuation and thin and inhomogeneous soil overlying overlying soil generation by bedrock weathering underground karst development and large groundwater depth and lying water table under the bottom of soils the erosion creep collapse mechanism of underground soil loss in the karst slopes is explained as follows power loss due to human cultivation activities that destroy the soil structure hydraulic force formed by rainfall infiltration wet dry cycle generated by rainfall erosion effect caused by rainfall penetration creeping and flowing of plastic stream soil and collapse the erosion creep collapse mechanism of underground soil loss has seven steps disturbance of soils filled in underground karst cave by human activities internal soil erosion and partial collapse caused by hydraulic power internal free surface formation within the soil in the filled karst cave internal soil creeping soil pipe formation soil pipe collapse and ground surface collapse and filling soil loss develops slowly and sudden transportation occurs by collapse soil loss can be explained by the proposed mechanism and soil loss can be prevented by controlling soil collapse

quasi periodic oscillations in a symmetric general circulation model abstract long lime integrations with a symmetric version of the clas climate model with hydrology have shown that the hadley circulation has well defined strong and weak episodes this oscillation of the hadley circulation seems to occur in two dominant range of periodicities one with periods between 10 and 15 days and another with periods between 20 and 40 days this quasi periodic behavior of the hadley circulation is seen only when the moist convective heating is determined by dynamics if the latent beating in the atmosphere is prescribed and kept artificially fixed this oscillation of the hadley circulation disappears thus this oscillation of the hadley circulation appears as a result of interactions between moist convective and dynamical processes a wave phenomenon is seen in the lower atmosphere that propagates toward the position of maximum radiative beating this wave perturbation has a length scale of about 15 20 degrees latitude in the north south direction this phenomenon has large ampli

icesat observations of seasonal and interannual variations of sea ice freeboard and estimated thickness in the weddell sea antarctica 2003 2009 sea ice freeboard heights for 17 icesat campaign periods from 2003 to 2009 are derived from icesat data freeboard is combined with snow depth from advanced microwave scanning radiometer for earth observing system amsr e data and nominal densities of snow water and sea ice to estimate sea ice thickness sea ice freeboard and thickness distributions show clear seasonal variations that reflect the yearly cycle of growth and decay of the weddell sea antarctica pack ice during october november sea ice grows to its seasonal maximum both in area and thickness the mean freeboards are 0 33 0 41 m and the mean thicknesses are 2 10 2 59 m during february march thinner sea ice melts away and the sea ice pack is mainly distributed in the west weddell sea the mean freeboards are 0 35 0 46 m and the mean thicknesses are 1 48 1 94 m during may june the mean freeboards and thicknesses are 0 26 0 29 m and 1 32 1 37 m respectively the 6 year trends in sea ice extent and volume are 0 023 0 051 x 10 exp 6 sq km a 0 45 a and 0 007 1 0 092 x 10 exp 3 cu km a 0 08 a however the large standard deviations indicate that these positive trends are not statistically significant

convection induced gravity waves observed by the equatorial atmosphere radar 0 20 s 100 32 e in indonesia 1 two days of continuous data acquired using the equatorial atmosphere radar ear boundary layer radar blr x band radar radiosonde and other collocated facilities were analyzed to demonstrate the relationship between the evolution of strong convection and its role in forcing gravity waves that penetrate from the troposphere into the lower stratosphere vertical winds in the troposphere and lower stratosphere were strongly modulated for about 6 8 hours by each convection event during the period 10 11 april 2004 temporal and spatial structure of momentum flux anomalies showed development from sources located near the middle troposphere these anomalies developed due to convection induced gravity waves and were marginally biased in the meridional direction radiosonde observations showed that atmospheric stability and gradual increase in vertical wind shear above convection played a key role in filtering the waves and modifying their vertical wavelength 2 km

role of epikarst in near surface hydrological processes in a soil mantled subtropical dolomite karst slope implications of field rainfall simulation experiments epikarst exerts a strong control on run off generation in karst regions but it is still unclear in karst regions our study aimed to demonstrate the effect of epikarst on near surface hydrological processes in a subtropical cockpit karst region of southwest china using plot scale rainfall simulation experiments with different rainfall intensities low and high and antecedent moisture conditions dry and wet a trench excavated to the epikarst lower boundary allowed identification of flow pathways in the entire soil epikarst architecture system thus facilitating the water balance calculations using a conceptual model with the assumption of a two stage hydrological evolution more than 70 of the total rainfall water moved vertically through the shallow soil layer and then was redistributed by the epikarst as subsurface flow occurring on the soil epikarst interface depression filling on epikarst surface water held by epikarst and deep percolation epikarst water regulation capacity defined as the sum of depression filling on epikarst surface water held by epikarst epikarst seepage flow and deep percolation was 58 mm wet antecedent condition and 223 mm dry antecedent condition total run off from the soil epikarst system was dominated by saturated subsurface flow showing a threshold process controlled by epikarst storage capacity storing as much as 181 mm of rainfall water under dry antecedent condition our study proved that despite the epikarst being relatively poorly developed and covered by a soil mantle it still exerted a strong influence on near surface hydrological processes and thus should be adequately considered in future modelling of water recharge and depletion dynamics in this integrated soil epikarst system copyright 2015 john wiley sons ltd

uncertainties in ice sheet altimetry from a spaceborne 1064 nm single channel lidar due to undetected thin clouds in support of the ice cloud and land elevation satellite icesat ii mission this paper studies the bias in surface elevation measurements caused by undetected thin clouds the icesat ii satellite may only have a 1064 nm single channel lidar onboard less sensitive to clouds than the 532 nm channel the 1064 nm channel tends to miss thin clouds previous studies have demonstrated that scattering by cloud particles increases the photon path length thus resulting in biases in ice sheet elevation measurements from spaceborne lidars this effect is referred to as atmospheric path delay this paper complements previous studies in the following ways first atmospheric path delay is estimated over the ice sheets based on cloud statistics from the geoscience laser altimeter system onboard icesat and the moderate resolution imaging spectroradiometer modis onboard terra and aqua second the effect of cloud particle size and shape is studied with the state of the art phase functions developed for modis cirrus cloud microphysical model third the contribution of various orders of scattering events to the path delay is studied and an analytical model of the first order scattering contribution is developed this paper focuses on the path delay as a function of telescope field of view fov the results show that reducing telescope fov can significantly reduce the expected path delay as an example the average path delays for fov 167 rad a 100 m diameter circle on the surface caused by thin undetected clouds by the 1064 nm channel over greenland and east antarctica are illustrated

vertical and lateral propagation characteristics of intraseasonal oscillation from the tropical lower troposphere to upper mesosphere 1 using a mesosphere stratosphere troposphere mst radar and a rayleigh lidar collocated at the indian tropical station gadanki 13 5 n 79 2 e european centre for medium range weather forecasts ecmwf re analysis data and the horizontal wind velocities measured by the thermosphere ionosphere mesosphere energetics and dynamics timed doppler interferometer tidi instrument onboard the timed satellite the present study makes a report on the lateral and vertical propagation characteristics of an intraseasonal oscillation iso 20 40 day period band propagating from the lower troposphere to the upper mesosphere region during the winter november december january and february months of the years 2004 2005 it is found that the iso had its origin in the tropical lower troposphere and propagated laterally and vertically to the upper mesosphere through the subtropical latitudes by partial refraction and reflection processes about the subtropical westerly jet corresponding enhancements in the wavelet spectrum of outgoing long wave radiation olr noaa interpolated indicate that convective forces in the lower troposphere are one of the main sources for the generation of the iso from the phase of the iso in the horizontal winds as observed by the mst radar it is found that the iso propagated upward from the lower troposphere up to near the tropopause where it got sharply attenuated from the ecmwf data it is observed that the iso was refracted to the subtropical latitudes through the tropical tropopause from where it got radiated upward into the stratosphere the phase propagation of the filtered winds shows that the iso arched back toward the tropical latitudes and propagated to the mesospheric region

morphology and origin of coastal karst landforms in miocene and quaternary carbonate rocks along the central western coast of sardinia italy in the area of punta funtanas arbus central west sardinia some small surfaces of miocene limestones crop out partially covered with quaternary calcarenites and plio quaternary basalts the biggest of these outcrops forms a fossil wave cut shore platform of up to 50 m wide with an altitude above sea level of approximately 4 5 m on this platform a wide variety of dissolution landforms can be observed these morphologies are related to the influence of the seawater zone of wave action marine splash and spray zone up to progressively more continental environments and to biokarst processes erosional action of marine organisms algae and micro organisms and are arranged in bands parallel to the coast corresponding to different morphological zones this paper describes all the karst landforms observed in this coastal area from a morphological and genetic point of view

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

tropical 45 day oscillations during the 1979 northern hemisphere summer abstract based on fgge 1 cvel iiib data the structural features of 45 day perturbations over a tropical belt 15 n 15 s during the 1979 summer are detailed at the equator 45 day perturbations which are primarily associated with the zonal wind components of wavenumber 1 propagate eastward 8 of longitude per day and upward 0 7 km per day probably indicating downward energy flux in the southern hemisphere tropics 0 15 s the 45 day zonal mean wind perturbations propagate downward with an approximate phase speed of 0 8 km per day in the northern hemisphere tropics they are largely of standing character with the maximum amplitude 3 m s 1 near 200 mb at 15 n there exists a strong association between monsoon activity over south asia and changes in the intensity of the equatorial walker circulation when active monsoons occur over south asia the walker circulation becomes stronger than usual with prominent 850 mb easterlies 200 mb easterlies over the eastern pacific east of the date line an

vertical variation of low frequency oscillations in uhf radar derived winds at a tropical indian station 1 signatures of the low frequency intraseasonal oscillations and their vertical variation in the lower troposphere are studied using multilevel wind observations made at a tropical indian station pune 18 32 n 73 51 e from wind profiler uhf radar during the period june 2003 to may 2006 spectral analysis using fast fourier transform showed the presence of oscillations 30 40 days and 50 70 days in daily mean zonal winds and revealed their evolution in height period structures the 30 40 days oscillation mode has the largest amplitude compared to the other modes in zonal and meridional winds all oscillation modes have much less amplitude in the vertical wind component the high temporal 3 hourly zonal and meridional wind observations obtained during the southwest monsoon period june to september jjas during the years 2003 2004 and 2005 showed a prominent regime of oscillation namely 30 40 days and a moderate signature of 10 20 day mode in all three years it is seen that these oscillations are not occurring as a single frequency sinusoidal oscillation but are seen as broadband spectrum the amplitude of these wave modes showed significant vertical variation the vertical structures of radar observed intraseasonal oscillations 30 40 days mode and tropical rainfall measuring mission derived mean precipitation intensity during the monsoon period jjas during the years 2003 2005 showed a reasonable comparison the results presented in this study show significant intraseasonal and interannual variability in lower tropospheric winds which are closely related to the performance of the southwest monsoon

a simple atmospheric model of the local and teleconnection responses to tropical heating anomalies abstract a minimal complexity model of both the local and remote stationary responses of the atmosphere to tropical heating anomalies is described and demonstrated two levels are recast as baroclinic and barotropic components with thermal advection in the tropics neglected the model is linearized about some idealized and realistic background wind fields and forced with a localized heating for illustration in the tropics the baroclinic responses are familiar from the matsuno gill model these excite barotropic responses by advective interactions with vertical background wind shear the barotropic signals are in turn transmitted to high latitudes only in the presence of barotropic background westerly winds for an el nino like equatorial heating the barotropic response has anticyclones to the north and south of the heating reinforcing opposing the anticyclonic cyclonic baroclinic gyres in the upper lower troposphere with realistic background flows the model reproduces the hemispheric asymmetry

runoff and erosion processes on bare slopes in the karst rocky desertification area underground pore fissure and bedrock bareness are the main factors that lead to complicated mechanisms of soil erosion in karst regions the objectives of this study were as follows a to measure runoff and sediment generated from the surface and underground in the karst bare slope and b to analyse the impacts of underground pore fissures and bedrock bareness rates on soil erosion to achieve these objectives we designed an experiment in which underground pore fissure degrees and bedrock bareness rates were varied and their impacts on soil erosion were measured the results showed that runoff and sediment yields from the surface and underground increased with increasing rainfall intensity and the surface runoff was much more easily generated when the rainfall intensity was greater ii surface runoff yield first increased and then decreased with increasing bedrock bareness rates while the runoff yield in underground pore fissures increased with increasing bedrock bareness rates thus sediment production on the surface and in underground pore fissures showed the same pattern i e first decreased and then increased iii the surface runoff and sediment generally decreased with increasing degrees of underground pore fissures while that of underground pore fissures presented a different pattern and iv rainfall intensity bedrock bareness rates and underground pore fissure degrees were the important factors affecting soil erosion processes in karst bare slopes because the bedrock bareness rates and underground pore fissure degrees were the main factors causing the uneven distribution of runoff and sediment on soil surfaces and underground therefore soil and water loss in underground pore fissures was the special pattern and main difference in soil erosion processes in the karst region compared with other regions these results have theoretical and practical significance for understanding soil erosion mechanisms and controlling soil and water loss in karst regions

icesat antarctic elevation data preliminary precision and accuracy assessment 1 since first light on february 20th 2003 nasa s ice cloud and land elevation satellite icesat has derived surface elevations from 86 n to 86 s latitude these unique altimetry data have been acquired in a series of observation periods in repeated track patterns using all three geoscience laser altimeter system glas lasers here we focus on antarctic ice sheet elevation data that were obtained in 2003 2004 we present preliminary precision and accuracy assessments of selected elevation data and discuss factors impacting elevation change detection we show that for low slope and clear sky conditions the precision of gla12 laser 2a release 21 data is 2 1 cm and the relative accuracy of icesat elevations is 14 cm based on crossover differences

divergent circulations on the 30 to 50 day time scale abstract a brief review of some of the recent results on the 30 to 50 day time scale is presented in this paper we have examined the divergent circulations on the time scale of 30 to 50 days during the fgge year the present study is based on two different data sets these are the fgge iiib analysis from the european center for medium range weather forecasts ecmwf and the florida state university s analysis over the monsoon region during the fgge year the analysis clearly identifies a planetary scale divergence wave that traverses around the globe eastward throughout the fgge year its speed of eastward propagation is around 8 longitude day 1 the amplitude of this wave is largest during the summer season over the monsoon region and the western pacific oceans the amplitude decreases somewhat as the wave traverses across the eastern pacific and atlantic oceans this wave appears to modulate the monsoon activity such that active inactive spells seem to bear a close relationship to the divergence on t

geometric morphology and soil properties of shallow karst fissures in an area of karst rocky desertification in sw china abstract serious soil erosion and an extremely low rate of soil formation leads to a thin layer of surface soil that makes tree growth difficult in areas of karst meanwhile surface soil driven by runoff enters shallow karst fissures skfs these skfs filled with soil have become the major habitat type in the area here we explore the morphological characteristics of shallow karst fissures as well as the soil physical and chemical properties of the skfs and comprehensively analyse the factors that influence the soil properties three key results are presented first a high heterogeneity of morphological characteristics exists for shallow karst fissures according to the different characteristics of the vertical section the skfs can be divided into 5 types these types are rectangle type pyramid type funnel type net type and diamond type in addition the skf dip angles were mainly between 60 and 90 76 39 the width of the top aperture was mainly between 20 and 40 cm 51 39 and the trace lengths were mainly between 80 and 160 cm 76 39 second compared with their characteristics of surface soil the bulk density and fractal dimension of soil particles of the skfs were both large and the main composition of the skf soil was clay third the soil nutrients of the skfs the organic matter total nitrogen and total phosphorus were lower than the surface soil nutrients but not significantly so the total potassium tk of the skfs was greater than that observed for the surface and increased as the depth of the skf increased the soil nutrients of the skfs were significantly affected by the fissure morphology the poorly connected fissures had better soil fertility when the morphological characteristics and soil properties of the skfs were comprehensively considered the vegetation types that were determined to be the best for use in the ecological restoration of areas of karst rocky desertification were deep rooted plants with especially strong root penetration the result of this study can supply some reference for future studies of karst rocky desertification control and vegetation restoration in the karst area of southwest china in the south claw silicon island in yogyakarta province indonesia and in other karst regions with the same ecological background

intraseasonal oscillations in the global atmosphere i northern hemisphere and tropics abstract we have examined systematically oscillatory modes in the northern hemisphere and in the tropics the 700 mb heights were used to analyze extratropical oscillations and the outgoing longwave radiation to study tropical oscillations in convection all datasets were band pass filtered to focus on the intraseasonal is band of 10 120 days leading spatial patterns of variability were obtained by applying eof analysis to these is data the leading principal components pcs were subjected to singular spectrum analysis ssa ssa is a statistical technique related to eof analysis but in the time domain rather than the spatial domain it helps identify nonlinear oscillations in short and noisy time series in the northern hemisphere there are two important modes of oscillation with periods near 48 and 23 days respectively the 48 day mode is the most important of the two it has both traveling and standing components and is dominated by a zonal wavenumber two the 23 day mode has the spatial stru

role of stratiform rainfall in modifying the northward propagation of monsoon intraseasonal oscillation 1 the stratiform and convective rain rate measurement from the tropical rainfall measuring mission trmm satellite data can give a realistic idea of the latent heating distribution in the tropics the vertical profile of diabatic heating related to the convective and the stratiform rain is known to modulate the dynamical response of atmosphere and also the vertical structure of madden julian oscillation in this study the contribution of the stratiform and convective rain rate to the total rain rate during different phases of the northward propagating boreal summer monsoon intraseasonal oscillation iso is examined using the trmm data two new insights have emerged from this analysis first unlike conventional wisdom the convective component shows weak northward propagation and grows and decays in situ during the evolution of active and break phases while the northward propagation of the monsoon iso is largely achieved by organized movement of the stratiform component second the trademark meridional dipole pattern of total rainfall between the monsoon trough zone and the southern equatorial indian ocean also arises largely from the contribution of stratiform anomalies as the northward propagation of the monsoon iso is known to be due to the anomalous response of the atmosphere to heating in the presence of mean easterly vertical shear modification of the vertical profile of heating due to a contribution from stratiform rain could influence the northward propagation of the monsoon iso this hypothesis is tested using a simple global atmospheric circulation model to study the response of the convective and stratiform heating profiles on the modification of the mean condition modification in the large scale response of the atmosphere as a result of proper specification of convective and stratiform heating anomalies indicates that the presence of stratiform heating favors the northward propagation of the heat source thereby facilitating the positive feedback leading to northward propagation of the monsoon iso these results underline the importance of simulating the partitioning of convective and stratiform rain by cumulus parameterization in climate models if they have to get the space time structure of the summer isos correct

mean vertical motions and their time height variations in the lower troposphere obtained from a uhf wind profiler at pune a tropical indian station 1 a 404 mhz wind profiler uhf radar system has been in continuous operation since june 2003 at pune 18 32 n 73 51 e a tropical indian station the system enables measurement of all three components zonal meridional and vertical of the wind field with height coverage from 1 05 km to about 10 km and a height resolution of 300 m daily mean profile data of vertical velocity in the lower troposphere obtained during the 3 year period june 2003 to may 2006 has been used in this study to investigate the long term mean clear air vertical velocity its variability and seasonal intraseasonal variations mean vertical velocities varied between 5 30 cm s 1 and 1 30 cm s 1 and mean vertical motions are predominantly downward at altitudes above 3 km significant seasonal variation in vertical velocity has been observed during southwest monsoon months june september a vertical two cell structure in vertical velocity has been noticed with upward motions below 4 km and downward motion above in the premonsoon months march may vertical motions are predominantly downward throughout the lower troposphere variability is larger during the monsoon and premonsoon seasons and is smaller during postmonsoon october november and winter december february seasons vertical velocities at altitudes below 3 km reveal significant semiannual and annual oscillations mean diurnal variations during sw monsoon period show interesting features the observed variability in vertical velocities especially in layers close to the surface is explained to be due to the highly variable weather conditions on local as well as synoptic scale at this tropical station

the 30 50 day mode at 850 mb during monex abstract the analyzed wind field at 850 mb during the summer monsoon experiment monex is subjected to a time series analysis to confirm the existence of a peak in the time range of 30 50 days having established that this study presents a mapping of the motion field for this time scale in this short paper we illustrate the steady meridional propagation of a train of troughs and ridges that seem to form near the equator and dissipate near the himalayas the meridional scale of this mode is around 300 km and its meridional speed of propagation is 0 75 latitude per day the amplitude of the wind for this mode is around 3 6 m s 1 the salient contributions here are the mapping and the demonstration of a very regular behavior of this mode its existence is here noted from a period well before the onset of monsoon i e from early may to late july three major storms during monex were noted to form within the trough line of this system and the period of major cessation of rains over the indian subconti

pre monsoon to monsoon change in direction of vertical motions in the tropical lower troposphere from uhf radar observations 1 multi height vertical wind data in the lower troposphere 1 05 3 75 km obtained from wind profiler uhf radar at pune 18 32 n 73 51 e india during june 2003 may 2006 has been used here to investigate the seasonal evolution in the vertical structure especially the change taking place from pre monsoon march may to south west monsoon june september season vertical motions are predominantly upward during winter december february and are strongly downward during pre monsoon a transition from downward to upward motion takes place around early june coinciding with the local onset of sw monsoon kinetic energy computed from zonal and meridional winds is small in magnitude during pre monsoon but shows an abrupt and explosive increase around the time onset of monsoon the results thus provide an observational evidence of existence of strong subsidence in the lower troposphere during pre monsoon which weakens and vertical winds turn upward signaling the arrival of monsoon conditions

spatial distribution of rock fragments on steep hillslopes in karst region of northwest guangxi china abstract rock fragments 5 mm in diameter at the soil surface and within the topsoil have a large effect on the intensity of various hydrologic and geomorphic processes however little information is available on the spatial distribution of rock fragments in subtropical regions the objective of this paper was to investigate the relationship between the spatial distribution of rock fragments and landforms on two different steep karst hillslopes in northwest guangxi southwest china on the first hillslope a disintegrated landslide failure with the presence of several large rock outcrops 2 m in height the spatial distribution of rock fragment cover had no obvious relationship with topographic position except that the mean cover percentage of small rock fragments 5 20 mm decreased from bottom to top on the second hillslope an avalanche slope without the presence of large rock outcrops the mean total rock fragment cover 5 600 mm increased from bottom 5 to top 21 with decreasing variability and rock fragments with various sizes 5 20 20 75 and 75 250 mm showed a similar increasing trend the mean total rock fragment cover increased linearly with slope gradient on the second hillslope and tended to increase and then decrease with gradient but their relationship was not obvious on the first hillslope this indicated that the spatial distribution of surface rock fragment cover had a close relationship with the presence of large rock outcrops and slope gradient however the median diameter d50 of the surface rock fragments had an increase decrease trend with slope gradient but there was no obvious relationship on both hillslopes with low overland flow therefore the dominant factor for the spatial distribution of rock fragment cover and size at the soil surface might not be soil erosion by water but slope gradient vegetation and geomorphologic condition of the slope the mean total volumetric rock fragment content 5 250 mm within the topsoil 10 20 cm thick increased linearly from bottom 16 to top 39 with slope gradient on the first hillslope and had a logarithmic increase from bottom 10 to top 27 with gradient on the second hillslope this suggested that rock fragment content within the topsoil was mostly controlled by slope gradient and topographic positions and had not a close relationship with the presence of large rock outcrops

icesat observations of arctic sea ice a first look 1 analysis of near coincident icesat and radarsat imagery shows that the retrieved elevations from the laser altimeter are sensitive to new openings containing thin ice or open water in the sea ice cover as well as to surface relief of old and first year ice the precision of the elevation estimates measured over relatively flat sea ice is 2 cm using the thickness of thin ice in recent openings to estimate sea level references we obtain the sea ice freeboard along the altimeter tracks this step is necessitated by the large uncertainties in the sea surface topography compared to that required for accurate determination of freeboard unknown snow depth introduces the largest uncertainty in the conversion of freeboard to ice thickness surface roughness is also derived for the first time from the variability of successive elevation estimates along the altimeter track overall these icesat measurements provide an unprecedented view of the arctic ocean ice cover at length scales at and above the spatial dimension of the altimeter footprint of 70 m

geomorphology of sand dunes in the northeast taklimakan desert three types of sand dunes exist in the taklimakan desert namely compound complex crescent dunes and crescent chains compound dome dunes and compound complex linear dunes besides these three compound complex types single simple dunes are also distributed throughout the sand sea the compound complex linear dunes are developed under acute bimodal wind regimes though the ratios of the resultant drift potential rdp and the drift potential dp are the same as that near the border and adjacent area of the sand sea the compound complex crescent and dome dunes are developed respectively because of divergence of the sand available the stress of the sand moving winds and the time scales of dune formation the sand supply for the dunes is not from lopo nor in the east as previous studies suggested but mainly from local alluvial or lacustrine deposits the grain size component does not correlate evidently to the morphology parameters of the sand dunes analyses of the dp and drift direction suggest that the northeast taklimakan is an area of low wind energy and the resultant drift direction rdd coincides well with the distribution morphology and scales of the dunes

structure genesis and scale selection of the tropical quasi biweekly mode the quasi biweekly mode qbm and the 30 60 day mode are two major intraseasonal oscillations isos in the tropics the qbm is known to have a major influence in determining the active and break conditions of the indian monsoon during the northern summer a westward propagating equatorial rossby wave with quasi biweekly period influences the australian monsoon during the northern winter universality between the summer and winter qbm is established through analysis of daily circulation and convection data for 10 years it is shown that the mean spatial structure of the qbm in circulation and convection resembles that of a gravest meridional mode equatorial rossby wave with wavelength of about 6000 km and westward phase speed of approximately 4 5 m s 1 however the maximum zonal wind occurs at around 5 n 5 s during the northern summer winter the wave structure appears to be translated northward southward by about 5 during the northern summer winter the relationship between outgoing long wave radiation and circulation data indicates that the mode is driven unstable by coupling with moist convection similarity in temporal and spatial characteristics of the mode during the two seasons leads us to propose that the same mechanism governs the genesis and scale selection of the mode in both the seasons an acceptable mechanism for genesis and scale selection of the qbm has been lacking in the present study a mechanism for genesis and scale selection of the observed qbm is proposed a simple 2 layer model that includes a steady ekman boundary layer bl formulation incorporating effect of entrainment mixing is constructed for the convectively coupled equatorial waves without influence of the background mean flow moist feedback in the presence of frictional bl convergence drives the gravest meridional mode equatorial rossby wave unstable with observed wavelength and period but with zonal winds symmetric about the equator potential temperature perturbation associated with the rossby wave is in phase with relative vorticity perturbation at low level the bl drives moisture convergence in phase with the relative vorticity at the top of the bl release of latent heat associated with the bl convergence enhances the potential temperature leading to a positive feedback the mean flow over the indian ocean and western pacific at low levels is such that the zero ambient absolute vorticity or the dynamic equator shifts to around 5 n 5 s during summer winter and results in a shift of the unstable rossby waves towards the north south by about 5 the resulting structure of the unstable rossby mode resembles the observed structure of the biweekly mode it is shown that neither evaporation wind feedback nor vertical shear of the mean flow is crucial for the existence of the mode however these processes marginally modify the growth rate and make the structure of the unstable wave more realistic