large scale mass redistribution in the oceans 1993 2001 1 a recent study of satellite laser ranging measurements by cox and chao 2002 indicates that large scale mass redistribution has caused a rapid change in earth s dynamic oblateness j2 since 1998 using satellite altimeter observations and two runs of an ocean general circulation models ogcm we examine mass variations in the oceans and their estimated effect on j2 combined altimeter and ogcm results indicate variations similar to the j2 changes in 1998 and predict considerably larger oceanic effects on the j2 anomaly than purely ogcm estimates suggesting that the oceans should not be ruled out by any means as a significant source of this interesting geodetic anomaly until they have been studied further

vhf radar observations of convectively generated gravity waves some new insights 1 vhf radar observations of tropical mesoscale convective systems have provided some new insights on convectively generated gravity waves over gadanki 13 5 n 79 2 e a tropical station in india present observations revealed disturbed tropopause structures and enhanced mass fluxes across the tropopause during the passage of deep convective systems the analysis suggest that during disturbed tropopause conditions not only the direct intrusion across the tropopause takes place but also the gravity wave activity associated with convection enhances in the lower stratosphere as compared to the stable tropopause conditions this result is a major outcome of the present study another noteworthy result from the present observations is the phase profile of convectively generated gravity waves which for the first time provided an opportunity to localize the source region of gravity waves

erratum to the control mechanisms of erosion and weathering at basin scale from cosmogenic nuclides in river sediment earth planet sci lett 237 2005 462 479

large potential energy of gravity waves over a smooth surface with little convection simulation and observation 1 a numerical experiment is conducted using an atmospheric general circulation model agcm to investigate the presence of the large potential energy over a region of low topography and little convective activity focusing on the tropical atlantic region 10 e to 20 w 0 to 20 s it is found that gravity waves with a time period of 24 hours are excited near the equator 5 15 n in a region of large moist heating extending vertically up to 10 13 km the gravity waves propagate upward from this region with a bias toward the south and are manifested as large energy fluxes in the cross equatorial region enhanced energy fluxes are therefore simulated at 20 30 km altitude over a region with no significant source of gravity waves and are confirmed using global positioning satellite meteorology gps met experiment data

gravity waves generated by convection during twp ice i inertia gravity waves gravity waves are analyzed in radiosonde soundings taken during the tropical warm pool international cloud experiment twp ice campaign the properties of the inertia gravity waves are analyzed in part i whereas part ii focuses on high frequency gravity waves two groups of inertia gravity waves are detected group l long vertical wavelength in the middle stratosphere during the suppressed monsoon period and group s short vertical wavelength in the lower stratosphere during the monsoon break period waves belonging to group l propagate to the southeast with a mean intrinsic period of 35 h and have vertical and horizontal wavelengths of about 5 6 km and 3000 6000 km respectively ray tracing calculations indicate that these waves originate from a deep convective region near indonesia waves belonging to group s propagate to the south southeast with an intrinsic period vertical wavelength and horizontal wavelength of about 45 h 2 km and 2000 4000 km respectively these waves appear to originate from convection in the vicinity of new guinea

recent earth oblateness variations unraveling climate and postglacial rebound effects earth9s dynamic oblateness j2 has been decreasing due to postglacial rebound pgr however j2 began to increase in 1997 indicating a pronounced global scale mass redistribution within earth9s system we have determined that the observed increases in j2 are caused primarily by a recent surge in subpolar glacial melting and by mass shifts in the southern pacific and indian oceans when these effects are removed the residual trend in j2 2 9 x 10 11 year 1 becomes consistent with previous estimates of pgr from satellite and eclipse data the climatic significance of these rapid shifts in glacial and oceanic mass however remains to be investigated

seasonal variations in lower stratospheric gravity wave energy above the falkland islands 1 the gravity wavefield in the lower stratosphere between 15 km and 22 km altitude above mount pleasant airport 51 49 s 58 26 w on the falkland islands is studied using over 2100 high resolution radiosonde soundings from 2002 to 2010 the seasonal variation in vertical direction of propagation shows a small decrease in numbers of upward propagating waves that is related to critical level filtering however there is a very large increase in numbers of downward propagating waves between july and september this is attributed to the proximity of the edge of the polar vortex there is a seasonal variation in gravity wave energy density with a large peak during the austral autumn equinox this is markedly different to results in the literature both from rothera on the antarctic peninsula and stations on the main antarctic continent this seasonal pattern has been shown to be linked to variations in the sources of upward propagating gravity waves the seasonal variation in gravity wave characteristics above mount pleasant airport seen in our results suggests that the gravity wavefield in this region is determined by a combination of different gravity wave sources located above and below the lower stratosphere

characteristics of high frequency gravity waves generated by tropical deep convection case studies 1 high frequency gravity waves generated by tropical deep convection play a major role in shaping the general circulation of the middle atmosphere special experiments were conducted to capture two convective events on 16 may and 5 june 2006 using vhf radar located at gadanki 13 5 n 79 2 e a tropical indian station control day observations were also made for necessary comparisons background wind and temperature information was obtained by gps radiosonde flights launched from the same site this work has utilized these valuable data sets to delineate characteristics of convectively generated gravity waves a superposition of gravity waves is observed with different scales after the deep convective events vertical wave number spectra of radial velocities show steeper slopes and higher power spectral densities during convection which slowly reduce to their normal values the present case studies suggest the mechanical oscillator mechanism to be a major source of convective gravity wave generation in the tropics estimates of vertical wind variances and momentum fluxes of short period 2 h wind fluctuations show large enhancements on convective days in comparison to control days the momentum flux frequency spectra revealed a higher contribution of 30 65 min wave periods to the mean profile in the lower stratosphere the wavelet transform momentum flux spectra displayed the temporal variability and discretization of the gravity wave momentum fluxes in frequency and time

gravity waves and turbulence associated with cumulus convection observed with the uhf vhf clear air doppler radars vertical wind disturbances are frequently observed during midsummer afternoons in association with cumulus convection to examine the relation of these wind disturbances to atmospheric stability and turbulence intensity we carried out intensive observations of wind temperature and humidity over a large vertical region extending from the boundary layer to the lower stratosphere using uhf vhf radars and radiosondes at shiga japan 35 n 136 e the wind disturbances propagate quickly into the upper troposphere just after 1500 local standard time lst when the level of free convection lfc descends below the top of the mixed layer while before that the disturbances are confined in the mixed layer however strong turbulence is largely confined to the region below 3 km even after 1500 lst suggesting that the height of 3 km corresponds to the top of cumuli while the wind disturbances above are due to gravity waves generated in association with cumulus convection in addition stratospheric disturbances were examined for 12 cases of midsummer disturbances using routine observational data taken with a vhf radar in a height region of 5 24 km wind disturbances are observed in the lower stratosphere when turbulence as well as wind disturbances are strong in the whole troposphere the stratospheric disturbances are dominant in two regions below and above a height of 18 km where the background horizontal wind is weak long period disturbances are observed only in the lower region this fact suggests that the height of 18 km is a critical level for the long period gravity waves the existence of a strong turbulent layer around 18 km is consistent with this inference

earth s variable rotation recent improvements in geodetic data and practical meteorology have advanced research on fluctuations in the earth9s rotation theinterpretation of these fluctuations is inextricably linked with studies of the dynamics of the earth moon system and dynamical processes in the liquid metallic core of the earth where the geomagnetic field originates other parts of the earth9s interior and the hydrosphere and atmosphere fluctuations in the length of the day occurring on decadal time scales have implications for the topography of the core mantle boundary and the electrical magnetic and other properties of the core and lower mantle investigations of more rapid fluctuations bear on meteorological studies of interannual seasonal and intraseasonal variations in the general circulation of the atmosphere and the response of the oceans to such variations

oceanic effects on polar motion determined from an ocean model and satellite altimetry 1993 2001 1 mass redistribution and motion in the oceans are major driving forces of geodetic variations including polar motion length of day geocenter and gravity field changes we examine oceanic contribution to polar motion using estimates from a data assimilating ocean general circulation model and satellite radar altimeter observations the data include model estimates of variations in oceanic mass obp and meridional and zonal velocities sea level anomalies from topex poseidon t p satellite altimeter measurements and steric sea surface height changes deduced from the model are also used to estimate obp effects estimated oceanic contributions from both the model and t p show considerably better agreement with polar motion observations compared with results from previous studies the improvement is particularly significant at intraseasonal timescales both obp and ocean current variations provide important contributions to polar motion at intraseasonal timescales the oceans appear to be a dominant contributor to residual polar motion not accounted for by the atmosphere the oceans also play an important role in seasonal excitation combined obp and ocean current contributions explain much of the residual semiannual variability

a note on the representation of steric sea level in models that conserve volume rather than mass this note discusses the representation of steric sea level in ocean circulation models changes in steric sea level are caused when changes in the density of the water column imply an expansion or contraction of the column models usually make the boussinesq approximation and conserve volume rather than mass and so do not properly represent expansion or contraction this means that although expansion contraction is included in the equation of state it is not accounted for by the model dynamics in this note we examine the equation governing the time evolution of the sea level displacement it is shown that requiring conservation of mass rather than volume introduces a new term to this equation a simple example is used to show the relationship of the new term to the surface buoyancy flux the equilibrium response to the new term has two parts one part consists of the goldsbrough and stommel gyres for which in the ocean interior vortex stretching due to the local expansion contraction of the water column is balanced by changes in planetary vorticity the other part corresponds to the inverse barometer the effect is to adjust sea level by a globally uniform but timevarying factor determined by the net expansion contraction of the global ocean since this correction is globally uniform it has no dynamical significance both the goldsbrough stommel gyres and the inverse barometer solution are missing from models as currently formulated this does not represent a serious error however if comparison is made with observations of sea level model calculated sea level should be adjusted by a globally uniform time varying factor determined by the net expansion contraction of the global ocean this would be important for assessing the likely rise in sea level in response to global warming

studies of quasi horizontally propagating gravity waves in the troposphere using the piura st wind profiler vhf profiler observations of the troposphere obtained over a flat desert in northern peru show the presence of strong quasi sinusoidal oscillations in the vertical wind velocity with periods of around 8 18 min these oscillations are a very typical feature of the vertical velocities over piura this paper presents an overview of the wave characteristics obtained at piura until this point including results obtained using two additional antennas built a few hundred meters to the west and south of the main antenna to measure horizontal wavelengths and phase velocities briefly the piura waves appear to have horizontal wavelengths of 1 3 km with either westward or eastward phase velocities in a ground based reference frame of 0 5 4 m s 1 their occurrence appears to be causally related to the magnitude of the easterly wind which blows over the andean cordillera some 60 km to the east of the site

hydrological and oceanic effects on polar motion from grace and models 1 terrestrial water storage tws and ocean bottom pressure obp are major contributors to the observed polar motion excitations second only to atmospheric mass movement however quantitative assessment of the hydrological and oceanic effects on polar motion remains unclear because of the lack of global observations in this paper hydrological and oceanic mass excitations to polar motion are investigated using monthly tws and obp derived from the gravity recovery and climate experiment grace for january 2003 until december 2008 the results from this analysis are compared with hydrological model excitations from the european center for medium range weather forecasts ecmwf and oceanic model excitations obtained from the jet propulsion laboratory jpl using estimating the circulation and climate of the ocean ecco results show that the grace derived obp and tws better explain the geodetic residual polar motion excitations for the px component at the annual period while the grace obp and ecmwf hydrological angular momentum agree better with the geodetic residuals for the annual py excitation grace ocean and hydrology excitations better explain the geodetic residuals for the semiannual py excitation however the jpl ecco and ecmwf models better explain the intraseasonal geodetic residual of polar motion excitation in the px and py components the grace data demonstrate much higher intraseasonal variability than either the models or the geodetic observations

the oceanic contribution to the earth s seasonal angular momentum budget seasonal variations in the speed of the earth s rotation manifest themselves as fluctuations in the length of the day lod with an amplitude of about 1000 microseconds s we know from previous work that at least 95 of these variations can be accounted for in terms of angular momentum exchanged between the atmosphere and the solid earth here we examine the respective contributions of the antarctic circumpolar current acc and the global oceans to the earth s seasonal angular momentum budget using in situ data from the drake passage and results from both the oceanic regional model fine resolution antarctic model fram of webb et al 1991 and the global oceanic model of maier reimer et al 1993 as analyzed by brosche et al 1990 the estimated annual contribution of the acc 2 4 s is much smaller than the total variation in the oceanic models or the existing lod aam residual both 15 20 s the estimated semi annual acc contribution 3 8 s is offset by counter currents further north in both oceanic models which exhibit larger semi annual variations in planetary angular momentum further refinements in the earth s seasonal angular momentum budget therefore will require the full planetary plus relative contribution of the global oceans in addition to that of the acc

the role of climate driven chemical weathering on soil production climate plays an important role in controlling rates of weathering and weathered regolith production regolith production functions however seldom take climate parameters into account based on a climate dependent weathered regolith production model at low denudation rates relative regolith thicknesses are less sensitive to changes in precipitation rates while at high denudation rates small changes in climatic parameters can result in complete stripping of hillslopes this pattern is compounded by the long residence times and system response times associated with low denudation rates and vice versa as others have shown the transition between regolith mantled and bedrock slopes is dependent on the ratio of denudation to production here we further suggest that this is itself a function of precipitation rate and temperature we suggest that climatic parameters can be easily incorporated into existing soil production models and that such additions improve the predictive power of soil production models

numerical modeling of gravity wave generation by deep tropical convection although convective clouds are known to generate internal gravity waves the mechanisms responsible are not well understood the present study seeks to clarify the dynamics of wave generation using a high resolution numerical model of deep convection over the tiwi islands australia the numerical calculations presented explicitly resolve both the mesoscale convective cloud cluster and the gravity waves generated as the convective clouds evolve they excite gravity waves which are prominent features of the model solutions in both the troposphere and stratosphere the source location is variable in time and space but is related to the development of individual convective cells the largest amplitude gravity waves are generated when the cloud tops reach the upper troposphere a new analysis technique is introduced in which the nonlinear terms in the governing equations are taken as the forcing for linear gravity waves the analysis shows that in the present calculation neither the shear nor the diabatic heating are the dominant forcing terms instead the wave source is most easily understood when viewed in a frame of reference moving with the wind at the level of neutral buoyancy whereupon the source may be described as a vertically oriented oscillating convective updraft this description is consistent with the properties of the modeled stratospheric waves

hydrological excitations of polar motion 1993 2002 summary changes in continental water storage obtained from an advanced land data assimilation system ldas are employed to compute hydrological excitations of polar motion for the 10 yr period of 1993 2002 the results are compared with observed excitations of polar motion and contributions from the atmosphere and ocean and with results from previous studies there is remarkably good agreement between ldas derived results and remaining observed excitations i e after atmospheric and oceanic effects are removed from the observations ldas predicted hydrological excitations play a major role in closing the excitation budget for prograde and retrograde annual wobble especially for the prograde component and show considerably better agreement with observations than previous results ldas predicted results show significantly larger interannual variability and also agree well with observed excitations not accounted for by the atmosphere and ocean as demonstrated in this study ldas shows major improvement in modelling large scale change in land water storage at both seasonal and interannual timescales 1i n t r o duction under the conservation of angular momentum any change in the earth s inertia tensor due to redistribution of mass will cause changes in the earth s rotation variations of atmospheric angular momentum aam or oceanic angular momentum oam will also change the earth s rotation via exchange of angular momentum between the solid earth and its geophysical fluid envelope at interannual or shorter timescales redistribution of air and water mass and movement within the earth system including the atmosphere ocean and hydrosphere plus snow ice sheet are primary driving forces behind changes in the earth s rotation while redistribution of mass within the core and mantle plays a more important role at decadal or longer timescales

hydrological and oceanic excitations to polar motion andlength of day variation summary water mass redistributions in the global hydrosphere including continental water storage change and non steric sea level change introduce variations in the hydrological angular momentum ham and the oceanic angular momentum oam under the conservation of angular momentum ham and oam variations are signi cant excitation sources of the earth rotational variations at a wide range of timescales in this paper we estimate ham and oam variations and their excitations to polar motion and length of day variation using soil moisture and snow estimates and non steric sea level change determined by topex poseidon satellite radar altimeter observations and a simpli ed steric sea level change model the results are compared with the variations of polar motion and lod that are not accounted for by the atmosphere this study indicates that seasonal continental water storage change provides signi cant contributions to both polar motion and lod variation especially to polar motion x and the non steric sea level change is responsible for a major part of the remaining excitations at both seasonal scale and high frequencies particularly in polar motion y and lod the good correlation between oam contributions and the remaining excitations shows that large scale non tidal mass variation exists in the oceans and can be detected by topex poseidon altimeter observations

review of wave turbulence interactions in the stable atmospheric boundary layer flow in a stably stratified environment is characterized by anisotropic and intermittent turbulence and wavelike motions of varying amplitudes and periods understanding turbulence intermittency and wave turbulence interactions in a stably stratified flow remains a challenging issue in geosciences including planetary atmospheres and oceans the stable atmospheric boundary layer sabl commonly occurs when the ground surface is cooled by longwave radiation emission such as at night over land surfaces or even daytime over snow and ice surfaces and when warm air is advected over cold surfaces intermittent turbulence intensification in the sabl impacts human activities and weather variability yet it cannot be generated in state of the art numerical forecast models this failure is mainly due to a lack of understanding of the physical mechanisms for seemingly random turbulence generation in a stably stratified flow in which wave turbulence interaction is a potential mechanism for turbulence intermittency a workshop on wave turbulence interactions in the sabl addressed the current understanding and challenges of wave turbulence interactions and the role of wavelike motions in contributing to anisotropic and intermittent turbulence from the perspectives of theory observations and numerical parameterization there have been a number of reviews on waves and a few on turbulence in stably stratified flows but not much on wave turbulence interactions this review focuses on the nocturnal sabl however the discussions here on intermittent turbulence and wave turbulence interactions in stably stratified flows underscore important issues in stably stratified geophysical dynamics in general

inertia gravity waves observed by the uk mst radar we present an analysis of eight years data from the uk mst radar at aberystwyth wales to determine the occurrence and properties of long period quasi monochromatic oscillations in the wind vector identified with inertia gravity waves wave perturbations were first isolated by filtering out background wind variation in the vertical then the continuity of the radar measurements was exploited to apply band pass filters in time to select quasi monochromatic oscillations with periods 4 8 hours or 12 24 hours by searching for altitude regions where the wind vector rotates systematically with height and fitting ellipses to such sections the properties of inertia gravity waves can be derived to guard against contamination by short intrinsic period mountain waves cases were discarded when the vertical velocity measured by the radar exceeded 15 cm s 1 results show that waves in the stratosphere are dominated by upward energy propagation clockwise rotation and those in the troposphere by downward propagation consistent with the dominant source for inertia gravity waves being at tropopause level long period waves 12 hours are observed 70 of the time in the lower stratosphere roughly twice as often as the shorter period waves and 10 20 of the time in the troposphere there is a winter maximum in occurrence in the troposphere and for the short period stratospheric waves however the dominant long period waves show little seasonal dependence likewise they show only a weak correlation with jet stream velocity or direction unlike the other categories which are preferentially associated with strong jet streams and propagate along the jet inertia gravity waves observed by the radar have typical amplitudes 1 2 m s 1 and vertical wavelength 2 km the intrinsic wave period estimated for non jet stream conditions is similar for the two band passed series pointing to the importance of doppler shifting in generating the observed oscillations copyright 2007 royal meteorological society

causes of rapid motions of the earth s pole analysis of new highly accurate geodetic data reveals rapid motions of the earth s pole with peak to peak variations of 0 002 to 0 020 seconds of arc fluctuating on timescales between two weeks and several months comparison with meteorological excitation estimates shows that these motions are at least partially driven by surface air pressure changes as modified by the response of sea level to atmospheric loading such geodetic measurements thus potentially provide a novel means of observing the dynamics of the atmosphere and oceans at very low spatial wavenumbers

atmospheric and oceanic excitation of the earth s wobbles during 1980 2000 1 because of the action of various geophysical excitation mechanisms the earth does not rotate about its figure axis so it wobbles as it rotates here the effectiveness of atmospheric and oceanic processes in exciting the earth s wobbles during 1980 2000 is evaluated using estimates of atmospheric angular momentum from the national centers for environmental prediction national center for atmospheric research ncep ncar reanalysis project and estimates of oceanic angular momentum from the estimating the circulation and climate of the ocean ecco consortium s simulation of the general circulation of the oceans on intraseasonal timescales atmospheric surface pressure changes are found to be the single most effective process exciting the earth s wobbles explaining about twice as much of the observed variance as do either atmospheric wind or ocean bottom pressure changes and nearly 4 times as much of the observed variance as do oceanic currents however on interannual timescales ocean bottom pressure changes are found to be the single most effective process exciting the earth s wobbles explaining more than 5 times as much of the observed variance as do atmospheric wind and pressure changes combined and more than twice as much of the observed variance as do oceanic currents within the chandler band it is found that during 1980 2000 atmospheric and oceanic processes have enough power to excite the chandler wobble and are significantly coherent with it the single most important mechanism exciting the chandler wobble is found to be ocean bottom pressure variations atmospheric and oceanic processes do not appear to have enough power to excite the earth s wobbles to their observed levels on pentadal and longer timescales although series longer than the 21 yearlong series used here need to be studied in order to obtain greater statistical significance of this result

erosion rates on different timescales derived from cosmogenic 10 be and river loads implications for landscape evolution in the rhenish massif germany we determined erosion rates on timescales of 101 104 years for two catchments in the northeastern rhenish massif in order to unravel the quaternary landscape evolution in a variscan mountain range typical of central europe spatially averaged erosion rates derived from in situ produced 10be concentrations in stream sediment of the aabach and mohne watersheds range from 47 6 to 65 14 mm ka and integrate over the last 9 13 ka these erosion rates are similar to local rates of river incision and rock uplift in the quaternary and to average denudation rates since the mesozoic derived from fission track data this suggests that rock uplift is balanced by denudation i e the landscape is in a steady state short term erosion rates were derived from suspended and dissolved river loads subsequent to 1 correcting for atmospheric and anthropogenic inputs 2 establishing calibration curves that relate the amount of suspended load to discharge and 3 estimating the amount of bedload the resulting solid mass fluxes suspended and bedload agree with those derived from the sediment volume trapped in three reservoirs however resulting geogenic short term erosion rates range from 9 to 25 mm ka and are only about one third of the rates derived from 10be model simulations in combination with published sediment yield data suggest that this discrepancy is caused by at least three factors 1 phases with higher precipitation and or lower evapotranspiration 2 rare flood events not captured in the short term records and 3 prolonged periods of climatic deterioration with increased erosion and sediment transport on hillslopes

rapid ocean signals in polar motion and length of day 1 non tidal variability in ocean currents and bottom pressure is substantial at short periods but relating the associated signals in ocean angular momentum oam to observed polar motion and length of day fluctuations has been difficult our simulations using a barotropic ocean model reveal a clear connection between the estimated oam signals and both polar motion and length of day at periods of 3 10 days the dynamic response of the oceans to barometric pressure plays an important role in the excitation of rapid rotation signals the impact of oam variability is most clear when using gps based earth orientation measurements with little temporal smoothing using the gps series and accounting for oam in addition to atmospheric effects yields substantial improvements in the excitation budget for rapid polar motion and length of day the comparisons with earth rotation data provide a useful check on the rapid ocean variability simulated by the barotropic model

microwave limb sounder observations of gravity waves in the stratosphere a climatology and interpretation high horizontal resolution temperature data from the microwave limb sounder mls are analyzed to obtain information about high intrinsic frequency gravity waves in the stratosphere global climatologies of temperature variance at solstice are computed using six years of data a linear gravity wave model is used to interpret the satellite measurements and to infer information about tropospheric wave sources globally uniform sources having several different spectral shapes are examined and the computed variances are filtered in three dimensional space in a manner that simulates the mls weighting functions the model is able to reproduce the observed zonal mean structure thus indicating that the observations reflect changes in background wind speeds and provide little information about the latitudinal variation of wave sources longitudinal variations in the summer hemisphere do reflect source variations since the modeled variances exhibit much less variation in this direction as a consequence of the zonal symmetry of the background winds a close correspondence between the mls variances and satellite observations of outgoing longwave radiation suggests that deep convection is the probable source for these waves the large variances observed over the tip of south america in winter are most certainly linked to orographic forcing but inferences about wave sources in northern hemisphere winter are difficult to make as a result of the high degree of longitudinal and temporal variability in the stratospheric winds comparisons of model results using different source spectra suggest that the tropospheric sources in the subtropics in summer have a broader phase speed spectrum than do sources at middle latitudes in winter

convectively generated gravity waves observed from radiosonde data taken during mctex the properties of gravity waves generated by deep tropical convective systems are analysed from radiosonde soundings taken during the maritime continent thunderstorm experiment and the results compared against recent cloud scale numerical modelling of convectively generated waves fluctuations in the ascent rate of the radiosonde are used to characterize the high frequency waves whereas the zonal wind fluctuations are used to determine the properties of the inertia gravity waves the density weighted vertical velocity variance shows a pronounced diurnal cycle with the largest amplitude gravity waves developing during the early afternoon following the development of deep convection in contrast the density weighted horizontal velocity variance and by implication the inertia gravity wave activity shows no diurnal variation simple theoretical analysis shows that the observations on 27 november 1995 are consistent with a westward propagating gravity wave with a horizontal wavelength of 17 km and a source frequency equal to 0 007 rad s 1 these findings are consistent also with a high resolution numerical model simulation for the same day nonetheless the character of the high frequency gravity waves cannot be uniquely determined from a single radiosonde sounding copyright 2003 royal meteorological society

oceanic excitations on polar motion a cross comparison among models recent studies based on various ocean general circulation models ogcms demonstrate that the oceans are a major contributor to polar motion excitations in this paper we analyse and compare observed non atmospheric polar motion excitations with oceanic angular momentum oam variations determined from four ogcms which include the parallel ocean climate model pocm a barotropic ocean model bom the estimating the circulation and climate of the ocean ecco non data assimilating model ecco nda and the ecco data assimilating model ecco da the data to be analysed span a 5 yr overlapped period from 1993 to 1997 at annual timescale considerable discrepancies exist between pocm and the other three models which result mainly from differences in annual components of the forcing wind fields at semi annual timescale however pocm shows better phase agreement with observed non atmospheric polar motion excitation than the other three ocean models at intraseasonal timescales ecco da yields better agreement with observations and reduces the variance of non atmospheric excitations by similar to 60 per cent 10 20 per cent more than those explained by the other three models however at the very short periods of 4 20 days the bom estimates could explain about half of the observed variance twice as much as that by ecco nda and also shows considerably better correlation with observations due to different modelling schemes and methods significant discrepancies could arise with respect to the quality of modelling large scale oceanic mass redistribution and current variation a complete understanding of global oceanic contributions to polar motion excitation still remains a challenge

impact of glacial erosion on 10 be concentrations in fluvial sediments of the marsyandi catchment central nepal several processes contribute to denudation in high mountain environments of these glacial erosion is particularly difficult to constrain despite its critical importance in the evolution of many mountain ranges in this study we present a new data set of 10be concentrations in fluvial sediments sampled along the marsyandi river and its main tributaries in central nepal we interpret the 10be concentrations as being significantly impacted by glacially derived sediments along the marsyandi river such additions complicate conventional interpretations of 10be derived catchment scale denudation rates using a simple linear mass conservation formulation we invert our data set in order to separate the different denudational contributions to the observed signal as well as to constrain their magnitude and spatial distribution our results suggest significant variations in glacial erosion both in space and magnitude within the marsyandi catchment

modelling soil landscape genesis a time split approach for hummocky agricultural landscapes abstract here we present a scheme for modelling soil landscape development in hummocky agricultural landscapes of formerly glaciated terrains soil landscape development is regarded as discontinuous over time long term progressive soil development during the holocene was replaced abruptly by an intense period of regressive pedogenesis during the last 50 years which is deduced from published 137 cs data and catchment scale mass balances consequently our primary working hypothesis is that the recent soil pattern is mainly a result of human influence during the last 50 years the paradigm behind our approach is that we have to couple geological historical information with recent dynamics of relevant processes to understand soil landscape development spatially distributed erosion and sedimentation are the most important processes during that period the intensity and extent of these processes is however also a function of the spatial pattern of soils erodibility which evolved in the progressive period therefore we developed a time split modelling approach for the progressive period relevant pedogenic processes de carbonatization silicate weathering clay translocation have to be quantified by a spatially distributed coupled water flow and solute transport model based on reconstructed initial and upper boundary conditions geomorphic units climate history relevant outputs e g topsoil textural properties are used as a spatially distributed input for the model of the regressive period for the latter we use a modified version of the dynamic physically based erosion 3d model schmidt j von werner m michael a 1996 erosion 2d 3d a computer model to simulate water erosion in german sachsische landesanstalt fur landwirtschaft dresden which allows spatially distributed modelling of water related soil erosion and deposition relevant topsoil properties are iteratively adapted to the rates of spatially distributed erosion and deposition preliminary results suggest that a coupling with tillage erosion plays an important role in our landscapes explicit analyses of the soil pattern using digital soil mapping techniques will be applied for model validation

low frequency inertia gravity waves in the stratosphere revealed by three week continuous observation with the mu radar continuous observations over three weeks were performed with the mu radar at shigaraki japan 35n 136e in april of 1995 by integrating radar echo spectra over 30 min after removing severe interferences winds were successfully estimated offline up to 24 km in the lower stratosphere it was found that inertia gravity waves with a period of about 20 h and a vertical wavelength of 3 5 km are dominant near 22 km in a region of weak background winds four wave packets were fitted to plane waves by a least squares method and wave parameters were estimated theoretically the inertia gravity waves propagate energy upward and their horizontal phase velocity is westward in the range 10 to 20 m s 1 the waves have large momentum fluxes of about 0 002 nm 2 this result suggests that inertia gravity wave drag may contribute to the formation of easterlies in the summer stratosphere

occurrence frequency of convective gravity waves during the north american thunderstorm season 1 convective gravity waves are an important driver of the equator to pole circulation in the stratospheric summer hemisphere but their nature is not well known previous studies showing tight relationships between deep convection and convective waves mainly focus on tropical latitudes for midlatitudes most analyses are based on case studies here we present a new multiyear occurrence frequency analysis of convective waves at midlatitudes the study is based on radiance measurements made by the atmospheric infrared sounder airs satellite experiment during the north american thunderstorm season may to august in the years 2003 2008 for this study we optimized an existing algorithm to detect deep convection in airs data to be applicable at midlatitudes we also present a new detection algorithm for gravity waves in airs data based on a variance filter approach for 4 3 m brightness temperatures the new algorithm can detect plane wave perturbations in the altitude range from 20 to 65 km with vertical wavelengths larger than 15 km and horizontal wavelengths from 50 to 1000 km by analyzing spatial and temporal correlations of the individual airs observations it can be shown that more than 95 of the observed gravity waves in a core region over the north american great plains are related to deep convective clouds i e are likely being classified appropriately as convective waves we conclude that the core region is a good location to observe and characterize the properties of convective waves at midlatitudes the statistical analyses presented here are also valuable to validate parameterization schemes for convective gravity waves for completeness it should be mentioned that our analyses cover not only the u s midwest but the north american continent as well as the surrounding ocean regions in general our analysis also reveals interesting details about tropical convection and related gravity wave activity as well as the capability of the airs instrument to observe these

geomorphology rain revs the crustal conveyor it is intuitive but evidence that high levels of precipitation increase erosion rates has been elusive the ages of exposed porphyry copper deposits reveal that rocks emplaced at depth travel to the surface faster where precipitation rates are high

oceanic signals in observed motions of the earth s pole of rotation motion of the earth s pole of rotation relative to its crust commonly referred to as polar motion can be excited by a variety of geophysical mechanisms1 in particular changes in atmospheric wind and mass fields have been linked to polar motion over a wide range of timescales but substantial discrepancies remain between the atmospheric and geodetic observations1 2 3 4 here we present results from a nearly global ocean model which indicate that oceanic circulation and mass field variability play important roles in the excitation of seasonal to fortnightly polar motion the joint oceanic and atmospheric excitation provides a better agreement with the observed polar motion than atmospheric excitation alone geodetic measurements may therefore be used to provide a global consistency check on the quality of simulated large scale oceanic fields

gravity wave forcing in the stratosphere observational constraints from the upper atmosphere research satellite and implications for parameterization in global models 1 global models that include parameterized gravity wave effects have an excessively broad range of tuning parameters to choose from that allow a very broad range of gravity wave momentum forcing distributions we derive a set of constraints on gravity wave characteristics near the tropopause from databased estimates of gravity wave effects in the stratosphere we use 5 6 years of upper atmosphere research satellite data and uk met office analyzed wind and temperature fields to first derive estimates of the gravity wave mean flow forcing in the stratosphere we then compare these estimates to a suite of gravity wave model calculations to infer the constraints on the gravity wave characteristics near the tropopause these constraints apply to the portion of the gravity wave spectrum that dissipates in the stratosphere and does not include those that dissipate and drive the mesosphere we focus on equatorial and extratropical regions separately and find substantially different wave characteristics between the two we also find a seasonal variation in gravity wave characteristics in the extratropics near the equator gravity waves assist in driving the quasibiennial and semiannual oscillations and our constraints on gravity waves likely include a blend of characteristics of both ordinary gravity waves and some kelvin wave modes in the extratropics gravity wave forcing primarily assists in the annual winter to summer transition from westward to eastward winds

a geoclim simulation of climatic and biogeochemical consequences of pangea breakup large fluctuations in continental configuration occur throughout the mesozoic while it has long been recognized that paleogeography may potentially influence atmospheric co2 via the continental silicate weathering feedback no numerical simulations have been done because of the lack of a spatially resolved climate carbon model geoclim a coupled numerical model of the climate and global biogeochemical cycles is used to investigate the consequences of the pangea breakup the climate module of the geoclim model is the foam atmospheric general circulation model allowing the calculation of the consumption of atmospheric co2 through continental silicate weathering with a spatial resolution of 7 5 long 4 5 lat seven time slices have been simulated we show that the breakup of the pangea supercontinent triggers an increase in continental runoff resulting in enhanced atmospheric co2 consumption through silicate weathering as a result atmospheric co2 falls from values above 3000 ppmv during the triassic down to rather low levels during the cretaceous around 400 ppmv resulting in a decrease in global mean annual continental temperatures from about 20 c to 10 c silicate weathering feedback and paleogeography both act to force the earth system toward a dry and hot world reaching its optimum over the last 260 myr during the middle late triassic in the super continent case given the persistent aridity the model generates high co2 values to produce very warm continental temperatures conversely in the fragmented case the runoff becomes the most important contributor to the silicate weathering rate hence producing a co2 drawdown and a fall in continental temperatures finally another unexpected outcome is the pronounced fluctuation in carbonate accumulation simulated by the model in response to the pangea breakup these fluctuations are driven by changes in continental carbonate weathering flux accounting for the fluctuations in area available for carbonate platforms the simulated ratio of carbonate deposition between neritic and deep sea environments is in better agreement with available data