linking water quality changes to geochemical processes occurring in a reactive soil column during treated wastewater infiltration using a large scale pilot experiment insights into mn behavior the spatial and temporal evolution of the physical properties and chemical composition of water and soil during the infiltration of treated wastewater through a reactive soil column at the pilot scale 25 m3 were investigated for 18 months major and trace elements and organic carbon were measured monthly in treated wastewater output water and pore water o2 co2 ch4 n2o n2 h2s and h2 were measured occasionally in soil air geochemical processes occurring in the soil changed rapidly over the study period nitrification was effective in the top 1 5 m of soil during the first 8 months thereafter the organic carbon load from treated wastewater and the treated wastewater left above the infiltration surface due to clogging organic matter accumulation and precipitation of carbonates created anaerobic conditions that led to denitrification and reductive dissolution of mn oxides in the soil the latter led to the release of both mn exceeding the who drinking water limit by a factor of up to 2 and ni that was strongly associated with the mn oxides forty five percent of the ni that had accumulated in the soil during the first year was released dissolved element concentrations were non uniform because of the spatial and temporal distribution of redox reactions in the soil due to the heterogeneous distribution of organic matter and or non uniform flow water saturation residence time the soil was very effective in removing phosphate fe and li and removing degrading organic carbon and nh4 in contrast ba no3 and to a lesser extent ca were exported removal rates were moderate for as and total nitrogen and low for k na ni and mn however removal rates of nitrogen species nh4 no3 total nitrogen mn fe ni and as were strongly dependent on redox conditions which varied during the experiment the evolution of geochemical processes occurring in the soil column therefore has significant implications on the quality of water moving from the soil to groundwater and provides key knowledge for the management of groundwater under artificial recharge

downward control of the mean meridional circulation and temperature distribution of the polar winter stratosphere abstract according to the downward control principle the extratropical mean vertical velocity on a given pressure level is approximately proportional to the meridional gradient of the vertically integrated zonal force per unit mass exerted by waves above that level in this paper a simple numerical model that includes parameterizations of both planetary and gravity wave breaking is used to explore the influence of gravity wave breaking in the mesosphere on the mean meridional circulation and temperature distribution at lower levels in the polar winter stratosphere the results of these calculations suggest that gravity wave drag in the mesosphere can affect the state of the polar winter stratosphere down to altitudes below 30 km the effect is most important when planetary wave driving is relatively weak that is during southern winter and in early northern winter in southern winter downwelling weakens by a factor of 2 near the stratopause and by 20 at 30 km when gravity wave drag is not included

a data study of the influence of the equatorial upper stratosphere on northern hemisphere stratospheric sudden warmings equatorial winds in the stratosphere are known to influence the frequency of stratospheric midwinter sudden warmings sudden warmings in turn influence the earth s climate both through their direct influence on polar temperatures and through the temperature dependence of ozone depletion in the lower stratosphere the conventional holton tan explanation for the equatorial influence on sudden warmings is in terms of the equatorial winds in the lower stratosphere 20 30 km acting as a waveguide for midlatitude planetary wave propagation this study employs stratospheric temperature analyses and equatorial rocketsonde wind data extending to 58 km to diagnose the relationship between the northern hemisphere polar temperatures and equatorial zonal winds at all height levels in the stratosphere in addition to the recognized holton tan relationship linking the polar temperatures to the quasi biennial oscillation in equatorial winds in the lower stratosphere a strong correlation of polar temperatures with equatorial winds in the upper stratosphere is found we suggest that this may be associated with the strength and vertical extent of the westerly phase of the semi annual oscillation in the upper stratosphere although the observations alone cannot provide a conclusive causal relationship the main diagnostic tools employed are correlation studies and composite analysis the results underline the need for continued high quality equatorial wind measurements at all stratospheric levels

elliptical diagnostics of stratospheric polar vortices diagnostics based on the spatial moments of isopleths of a long lived tracer or of potential vorticity are presented that enable the structure and evolution of stratospheric polar vortices to be concisely summarized and quantified the area centre aspect ratio and orientation of the equivalent ellipse of the vortex on an isentropic surface are defined using the second and lower order spatial moments of contours within the vortex edge region by examining the variations of these elliptical diagnostics with time and altitude the temporal evolution and vertical structure of the polar vortices can be quantified the usefulness of the diagnostics is assessed by examining nitrous oxide data from the geophysical fluid dynamics laboratory skyhi general circulation model the diagnostics show and quantify several differences between the arctic and antarctic vortices in the skyhi model the arctic vortex moves further off the pole is generally more elongated and has a more complicated vertical structure than the antarctic vortex with larger variations of both the vortex centre and elongation with height the elliptical diagnostics also identify the occurrence of large scale rossby wave breaking events both at the vortex edge and in the subtropics in the model

experiments on tropical stratospheric mean wind variations in a spectral general circulation model abstract a 30 level version of the rhomboidal 15 gfdl spectral climate model was constructed with roughly 2 km vertical resolution in common with other comprehensive general circulation models this model fails to produce a realistic quasi biennial oscillation qbo in the tropical stratosphere a number of simulations were conducted in which the zonal mean winds and temperatures in the equatorial lower and middle stratosphere were instantaneously perturbed and the model was integrated while the mean state relaxed toward its equilibrium the time scale for the mean wind relaxation varied from somewhat over one month at 40 km to a few months in the lower stratosphere this is similar to the time scales of observed qbo wind reversals the wind relaxations in the model also displayed the downward phase propagation characteristic of qbo wind reversals and mean wind anomalies of opposite sign to the imposed perturbation appear at higher levels in the gcm however the downward propagation is clear only abov

effects of an imposed quasi biennial oscillation in a comprehensive troposphere stratosphere mesosphere general circulation model a 48 yr integration was performed using the geophysical fluid dynamics laboratory skyhi troposphere stratosphere mesosphere gcm with an imposed zonal momentum forcing designed to produce a quasi biennial oscillation qbo in the tropical stratosphere in response to this forcing the model generates a qbo in the tropical circulation that includes some very realistic features notably the asymmetry between the strength of the descending easterly and westerly shear zones and the tendency for the initial westerly accelerations to appear quite narrowly confined to the equator the extratropical circulation in the northern hemisphere nh winter stratosphere is affected by the tropical qbo in a manner similar to that observed in particular the polar vortex is generally weaker in winters in which there are easterlies in the tropical middle stratosphere roughly twothirds of the largest midwinter polar warmings occur when the equatorial 30 mb winds are easterly again in rough agreement with observations despite this effect however the total interannual variance in the zonalmean extratropical circulation in the model apparently is slightly decreased by the inclusion of the tropical qbo the observed qbo dependence of the winter mean stratospheric extratropical stationary wave patterns is also quite well reproduced in the model the qbo was also found to have a profound influence on stratospheric stationary waves at low latitudes near and above 10 mb the nh stationary waves were found to penetrate across the equator during the westerly qbo phase but to be restricted to latitudes poleward of 108n during the easterly phase this means that the equatorial qbo in prevailing wind near and above 10 mb has a significant zonally asymmetric component if this is also true in the real atmosphere there are important implications for the adequacy of the current observational rawindsonde network near the equator analysis of the zonal mean zonal momentum budget in the tropical stratosphere reveals that the resolved waves in the model are strong enough to force the realized accelerations through much of the qbo cycle the exception appears to be the easterly acceleration phase below about 20 mb the implications of this for the generation of a self consistent qbo by gcms will be considered the effects of the imposed qbo on the troposphere were found to be very modest there does appear to be a statistically significant weakening by 1ms 21 of the high latitude winter vortex in the middle and upper troposphere given the very high predictability of the stratospheric qbo itself this effect could possibly be used to enhance the skill of seasonal weather forecasts no significant qbo influence was found in the model precipitation field

mountain ordering a method for classifying mountains based on their morphometry a new method for classifying mountain morphology mountain ordering is proposed and quantitative expressions for various morphological parameters of two ordered mountains in northern japan were obtained using this method mountain order was defined in terms of the closed contour lines on a topographic map a set of closed concentric contour lines defines a first order mountain higher order mountains can be defined as a set of closed contour lines that contain lower order mountains and that have only one closed contour line for each elevation they are identified as m 1th order mountains where m represents the order of the enclosed lower order mountains the geomorphometry for a mountain ordered according to this definition permits the identification of systematic relationships between various morphological parameters the relationships between mountain order and these morphological parameters follow a form similar to that of horton s laws and permit the calculation of the ratios of number area and height these parameters are sufficient to express the magnitude of a mountain s dissection the size frequency distribution for area and height shows self similarity for ordered mountains and determines their fractal dimensions furthermore the relationship between area and height which has the form of a power function describes the relief structure of ordered mountains copyright 1999 john wiley sons ltd

fluvial landsculpting and the fractal dimension of topography abstract quantitative models of landform development can help us to understand the evolution of mountains and regional topography and the effects of tectonic motions and climate on landscape including its fractal geometry this paper presents a general and powerful three dimensional model of fluvial erosion and deposition at hill to mountain range scale the model works by accumulating the effects of randomly seeded storms or floods precipitons that cause diffusional smoothing then move downslope on digital topography grids that erode portions of elevation differences that transport a slope limited amount of eroded material and that deposit alluvium when their sediment carrying capacity is exceeded the iteration of these simple and almost linear rules produce very complicated simulated landscapes demonstrating that complex landscapes do not require complex laws each process implemented in the model is affected differently by changes in horizontal scale erosion a scale free process roughens topography at all wavelengths this roughening is balanced by diffusive processes scaling as 1 l 2 at short wavelengths and deposition scaling scaling as 1 l 2 at long wavelenghts such a mixture of scale free and scale dependent processes can produce multifractal behavior in the models the fractal dimension of the model topography is much more sensitive to climatic variables than to tectonic uplift landscape evolution may be fractal but it does not seem to be chaotic analysis of topography of areas in southern arizona using variograms shows approximately fractal behavior with mean fractal dimension around 2 2 2 3 departures from an exact fractal relatioship imply that the topography is in detail multifractal the fractal dimension at short wavelengths is less than that at long wavelengths this variation could either be caused by the relative strengths of diffusive and erosional processes shaping the topography or a result of changes in climatic or tectonic conditions still preserved in the landscape

two day wave observations of uars microwave limb sounder mesospheric water vapor and temperature 1 a two day wave disturbance is observed in the mesospheric temperature and water vapor on the basis of new version data from the upper atmosphere research satellite microwave limb sounder using two data segments during the austral summers january february of 1992 and 1993 and the asynoptic mapping method a strong wave signal is identified as having zonal wave number 3 and a westward period of about 2 1 days the wave amplitudes are located near the core of the summer easterly jet with strongest wave amplitudes as large as 11 k and 0 35 part per million by volume near the mesopause the temperature and water vapor wave strengths are highly correlated in time but their peaks are almost longitudinally out of phase poleward heat flux associated with upward wave energy propagation in the southern hemisphere points to baroclinic instability as the cause for the wave appearance a growing wave signature in water vapor is observed in regions of strong meridional gradient of water vapor near the mesopause wave breaking is suggested as moist polar air is displaced into the much drier subtropics and wave amplitude decays

cross equatorially radiating stratospheric rossby waves upper atmosphere research satellite observations of constituent distributions in the middle stratosphere show that extratropical rossby waves from the winter hemisphere can at certain times radiate across the equator and reach the summer subtropics before they break and are absorbed conditions are most favorable for rossby waves to radiate into the tropics when the westerlies of the winter hemisphere extend to low latitudes as usually occurs during november and december in the northern hemisphere cross equatorial radiation of quasi stationary rossby waves requires westerly equatorial winds as occurred in the middle stratosphere in late 1992 constituent distribution maps show numerous episodes of rossby wave radiation across the equator during this early winter period but not after early january 1993 wave breaking in both the winter and summer subtropics above 22 mb causes constituent exchange between the tropics and extratropics including deep tropical in mixing

trench infiltration for managed aquifer recharge to permeable bedrock managed aquifer recharge to permeable bedrock is increasingly being utilized to enhance resources and maintain sustainable groundwater development practices one such target is the navajo sandstone an extensive regional aquifer located throughout the colorado plateau of the western united states spreading basin and bank filtration projects along the sandstone outcrop s western edge in southwestern utah have recently been implemented to meet growth related water demands this paper reports on a new cost effective surface infiltration technique utilizing trenches for enhancing managed aquifer recharge to permeable bedrock a 48 day infiltration trench experiment on outcropping navajo sandstone was conducted to evaluate this alternative surface spreading artificial recharge method final infiltration rates through the bottom of the trench were about 0 5m day these infiltration rates were an order of magnitude higher than rates from a previous surface spreading experiment at the same site the higher rates were likely caused by a combination of factors including the removal of lower permeability soil and surficial caliche deposits access to open vertical sandstone fractures a reduction in physical clogging associated with silt and biofilm layers minimizing viscosity effects by maintaining isothermal conditions minimizing chemical clogging caused by carbonate mineral precipitation associated with algal photosynthesis and diminished gas clogging associated with trapped air and biogenic gases this pilot study illustrates the viability of trench infiltration for enhancing surface spreading of managed aquifer recharge to permeable bedrock published in 2010 by john wiley sons ltd

atlantic seasonal hurricane frequency part i el nino and 30 mb quasi biennial oscillation influences abstract this is the first of two papers on atlantic seasonal hurricane frequency in this paper seasonal hurricane frequency as related to e1 nino events during 1900 82 and to the equatorial quasi biennial oscillation qbo of stratospheric zonal wind from 1950 to 1982 is discussed it is shown that a substantial negative correlation is typically present between the seasonal number of hurricanes hurricane days and tropical storms and moderate or strong 15 cases el nin off the south american west coast a similar negative anomaly in hurricane activity occurs when equatorial winds at 30 mb are from an easterly direction and or are becoming more easterly with time during the hurricane season this association of atlantic hurricane activity with el nino can also be made with the southern oscillation index by contrast seasonal hurricane frequency is slightly above normal in non el nino years and substantially above normal when equatorial stratospheric winds blow from a westerly direction and or are bec

measurement of self affinity on surfaces as a trial application of fractal geometry to landform analysis abstract landforms which are often referred to as good examples of fractal geometry are considered to be self affine because they appear flatter as the viewing point is moved farther away the line scaling method which can express the self affinity of various curves including self similar curves as a limiting case by separately scaling two coordinates was expanded and applied to surfaces developing in three dimensional space area scaling method for the purpose of deriving a parameter which might be useful in landform analysis the variance of height change z 2 surface area s and basal area a measured in a number of scaling unit areas of various sizes can be scaled as z 2 s z and a s a indicating the self affinity of these surfaces z 2 and a then are scaled to each other as z 2 a h and h z a in the of land surfaces h v z because a is always close to 1 this means that h is equivalent to the scaling hurst exponent h 0 h h measured by the area scaling method closely reproduced the initially introduced h values of computer generated fractional brownian surfaces although vertical exaggeration can make a surface look very different from the original appearance the measured values of h do not change significantly owing to vertical exaggeration the h value seems to express a relief texture essential for the surface a surface with minor h has a greater local roughness relative to the total relief than surfaces with large h the area scaling method then was applied to actual landforms in two areas of well dissected low mountains using equally scaled topographic maps with the same grid spacing 25 m grid on 1 5000 maps the obtained values of h are considered reasonable for the difference in relief texture shown by the block diagrams of these areas h values which were evaluated for four different landscapes on 1 25 000 topographic maps with a 125 m grid moreover also seem to indicate their relief texture expressed by the 125 m grid spacing h values obtained by the area scaling method may become a useful parameter to express the degree of self affinity or relief texture of landform surfaces although more research is necessary to establish the reliability of the h parameter for landform analysis

quasi biennial oscillation of short period planetary waves and polar night jet in winter antarctica observed in saber and merra 2 and mechanism study with a quasi geostrophic model

modeling the quasi biennial oscillation s effect on the winter stratospheric circulation abstract the influence of the equatorial quasi biennial oscillation qbo on the winter middle atmosphere is modeled with a mechanistic global primitive equation model the model s polar vortex evolution is sensitive to the lower stratosphere s tropical winds with the polar vortex becoming more less disturbed as the lower stratospheric winds are more easterly westerly this agrees with the observed relationship between wintertime polar circulation strength and the phase of the qbo in the lower stratosphere in these experiments it is the extratropical planetary rossby waves that provide the tropical extratropical coupling mechanism more easterly tropical winds in the lower stratosphere act to confine the extratropical rossby waves farther north and closer to the vortex at the qbo altitudes weakening the vortex relative to the case of westerly qbo phase while the qbo winds occur in the lower stratosphere the anomaly in the polar vortex strength is strongest at higher levels

quantitative diagnostics of mixing in a shallow water model of the stratosphere two different approaches are applied to quantify mixing in a shallow water model of the stratosphere these are modified lagrangian mean mlm theory and a technique referred to as reverse domain filling with local gradient reversal rdf lgr the latter is similar to a previously existing technique using contour advection and contour surgery it is first proved that in an inviscid shallow water atmosphere subject to mass sources and sinks if the mass enclosed by a potential vorticity pv contour is steady in time then the integral of the mass source over the area enclosed by the contour must be zero next the mlm and rdf lgr approaches are used to diagnose the time averaged transport across pv contours in the model simulations the model includes a sixth order hyperdiffusion on the vorticity field except in a thin outer entrainment zone the hyperdiffusion term has only a very weak effect on the mlm mass budget of the polar vortex in the entrainment zone the hyperdiffusion term has a significant effect the rdf lgr results capture this behavior providing good quantitative estimates of the hyperdiffusion term which is equivalent to the degree of radiative disequilibrium at a pv contour this agreement shows that the main role of the hyperdiffusion is to mop up the filaments that are produced by the essentially inviscid large scale dynamics all calculations are repeated for two values of the hyperdiffusion coefficient that differ by a factor of 50 with little difference in the results this suggests that the amount of material entrained from the vortex edge into the surf zone does not depend on the details of the small scale dissipation as long as it is sufficiently weak and has some degree of scale selectivity

the influence of the quasi biennial oscillation on the troposphere in winter in a hierarchy of models part i simplified dry gcms abstracta dry primitive equation model is used to explain how the quasi biennial oscillation qbo of the tropical stratosphere can influence the troposphere even in the absence of tropical convection anomalies and a variable stratospheric polar vortex qbo momentum anomalies induce a meridional circulation to maintain thermal wind balance this circulation includes zonal wind anomalies that extend from the equatorial stratosphere into the subtropical troposphere in the presence of extratropical eddies the zonal wind anomalies are intensified and extend downward to the surface the tropospheric response differs qualitatively between integrations in which the subtropical jet is strong and integrations in which the subtropical jet is weak while fluctuation dissipation theory provides a guide to predicting the response in some cases significant nonlinearity in others particularly those designed to model the midwinter subtropical jet of the north pacific prevents its universal application when the ext

the gradient genesis of stratospheric trace species in the subtropics and around the polar vortex abstract mechanisms that control the formation and decay of meridional gradients in stratospheric trace species in the subtropics and around the polar vortex are investigated using a gradient genesis equation that uses mass weighted isentropic zonal means application of this method to global nitrous oxide n2o data output from a global chemical transport model shows that mean vertical transport increases the meridional tracer gradient from the subtropics to midlatitudes through the shearing deformation particularly related to overturning of the brewer dobson circulation mean meridional transport advects the subtropical tracer gradient toward midlatitudes while the eddy stairstep effect steepening at the edge of the well mixed region because of a meridional gradient in the diffusion coefficient increases the tracer gradient in the subtropics and around the polar vortex mechanisms controlling the evolution of the tracer gradients in the subtropics differ between spring and autumn the autumnal subtr

interannual variations of global total ozone revealed from nimbus 4 buv and ground based observations an objective analysis is made by the hybrid use of nimbus 4 buv and ground based network data to investigate interannual variations in global distributions of total ozone much improvement in spatial resolution and reliability of the analysis is attained from the deduced time changes in 7 years april 1970 to may 1977 the quasi biennial and 4 year oscillations qbo and fyo are separated by numerical filtering characteristic features of these oscillations are investigated by examining time changes of global patterns as well as some spatial mean values the qbo in total ozone is characterized by large variabilities in time and space typical features are as follows in the tropics positive deviations nearly coincide with the westerly phase of equatorial zonal wind at 50 mbar zonally uniform phase changes exhibiting cross equatorial northward propagation are observed phase propagation is continuous to northern mid latitudes where the ozone distributions are accompanied by zonal wave number 3 4 disturbances in northern high latitudes deviations superposed by wave number 1 distribution are found often opposite to mid latitudes in the southern hemisphere the phase is reversed around 15 s and nearly out of phase relation to northern mid latitudes is observed wave number 1 is the dominant wave component through out the southern hemisphere the fyo in total ozone is suggested as a global phenomenon this oscillation is characterized as follows a roughly symmetric distribution with respect to the equator is observed with the out of phase relation between tropics and extratropics there also appears a phase propagation starting from southern high and mid latitudes and reaching northern high latitudes zonally uniform phase changes with wave number 3 disturbances are seen in the northern mid latitudes in the equatorial region and southern hemisphere systematic phase precedings in the western hemisphere are observed for both qbo and fyo planetary scale total ozone waves of zonal wave number 1 in the winter hemisphere are seen to penetrate into the summer hemisphere

on the subtropical edge of the stratospheric surf zone abstract the formation of a subtropical transport barrier in the wintertime stratosphere is investigated in the context of a high resolution shallow water model in which rossby waves are topographically forced on a zonally symmetric basic state two sets of experiments are performed in the first adiabatic set no dissipation or forcing of the mean state is imposed in the second set the layer thickness is relaxed to an equilibrium state taken to be representative of middle stratospheric radiative equilibrium temperatures it is found that in the adiabatic case only a very weak subtropical barrier forms for forcing amplitudes that generate realistically steep potential vorticity gradients at the edge of the polar vortex the vigorous wave breaking in the surf zone generates secondary waves that spread and in turn break well into the summer hemisphere in contrast the inclusion of relaxation to a realistic thermal equilibrium leads to the formation of a subtropical region of steep pv gradients the

the impact of variably saturated conditions on hydrogeochemical changes during artificial recharge of groundwater artificial recharge of groundwater is often used to either purify partially treated wastewater or to enhance the quality of surface water by percolation through a variably saturated zone in many cases the most substantial purification process within the infiltration water is the redox dependent biodegradation of organic substances the present study was aimed at understanding the spatial and temporal distribution of the redox reactions that develop below an artificial recharge pond near lake tegel germany at this site like at many artificial recharge sites the hydraulic regime immediately below the pond is characterised by cyclic changes between saturated and unsaturated conditions these changes which occur during each operational cycle result from the repeated formation of a clogging layer at the pond bottom regular hydrogeochemical analyses of groundwater and seepage water in combination with continuous hydraulic measurements indicate that no3 and mn reducing conditions dominate beneath the pond as long as water saturated conditions prevail manganese fe and so42 reducing conditions are confined to a narrow zone directly below the clogging layer and in zones of lower hydraulic conductivity the formation of the clogging layer leads to a steady decrease of the infiltration rate which ultimatively causes a shift to unsaturated conditions below the clogging layer atmospheric o2 then starts to penetrate from the pond fringes into this region leading to i the re oxidation of the previously formed sulphide minerals and ii the enhanced mineralisation of sedimentary particulate organic c the mineralisation of sedimentary particulate organic c leads to an increased h2co3 production and subsequent dissolution of calcite

rossby wave propagation into the tropical stratosphere observed by the high resolution doppler imager stratospheric wind observations by the high resolution doppler imager on the upper atmosphere research satellite show that quasi stationary rossby waves propagate into the tropics rossby wave breaking and dissipation causes meridional transport and direct deposition of momentum and has a significant influence on the evolution of the mean tropical winds in the upper stratosphere deeper penetration into the tropics occurs when the quasi biennial oscillation is in its westerly phase above 30 km during northern winter subtropical momentum deposition by rossby waves occurs only in late november through december while during southern winter this occurs primarily in august and september

distribution of major stratospheric warmings in relation to the quasi biennial oscillation data from 1953 to the present indicate that major warmings in the northern hemisphere winter have not occurred when the equatorial monthly mean zonal winds are deep westerly i e westerly over more than about 5 8 of the 10 85 mb layer sixteen winters have had a major warming in the last 35 years six january february periods had deep equatorial westerlies but did not experience a major warming major warmings do not require deep equatorial easterlies nor is the occurrence of a major warming significantly correlated with the sign of the zonal mean wind at any particular level between 10 and 50 mb although as noted by previous investigators more than half of the observed major warmings have occurred when the equatorial flow is easterly at a given level between 10 and 50 mb we suggest that a more relevant qbo statistic may be found in the depth of qbo wind regimes the previously proposed connection between the equatorial quasi biennial oscillation and the major warmings of the northern hemisphere winter is supported by these observations

tropical mixing barriers in the lower stratosphere in the geophysical fluid dynamics laboratory skyhi model large scale isentropic mixing in the tropical lower stratosphere is investigated by computing lagrangian trajectories using winds from the geophysical fluid dynamics laboratory skyhi general circulation model the use of model simulated winds avoids some problems with analyzed winds in the tropics during the solstitial seasons a weak mixing zone is present in the tropics in the model simulations the weak mixing zone is relatively isolated from the midlatitude surf zones in the northern and southern hemispheres by two mixing barriers a strong one on the summer hemisphere side and a weak one on the winter side the mixing barriers vary seasonally in response to seasonal variations of the tropical zonal mean zonal flow and wave spectrum the roles of the zonal mean flow and of different parts of the wave spectrum in meridional transport are tested using filter techniques effective meridional diffusion coefficients are calculated by using filtered and antifiltered winds i e winds with selected spatial scales either attenuated or amplified the results suggest that mixing in the tropical easterlies occurs near the critical layers for the large scale zonal wavenumber 10 westward moving waves which is where the waves would be expected to break wave spectrum analysis indicates that during the solstitial seasons there is a zone in the tropics exactly matching the weak mixing zone where there is relatively little power in westward moving waves the tropical mixing barriers are a result of the relative lack of such waves

the roles of the hadley circulation and downward control in tropical upwelling abstract several idealized models of tropical upwelling are presented in order to clarify the roles of the nonlinear hadley circulation and extratropical wave driving in particular it is shown that the hadley circulation and wave driven circulation interact to determine the nature of tropical upwelling the authors explain several observed features such as maximum upwelling in the summer subtropics and the annual variation of the upwelling

longitudinal variation of the stratospheric quasi biennial oscillation the longitudinal dependence of interannual variations of tropical stratospheric wind is examined in a detailed general circulation model simulation and in the limited observations available a version of the skyhi model is run with an imposed zonally symmetric zonal momentum source that forces the zonal mean zonal wind evolution in the tropical stratosphere to be close to an estimate of the observed zonal wind based on radiosonde observations at singapore during the period 1978 99 this amounts to a kind of simple assimilation model in which only the zonal mean wind field in the tropical stratosphere is assimilated and other quantities are allowed to vary freely a total of five experiments were run one covering the full 1978 99 period and four for 1989 99 the results at and above about 30 hpa are fairly simple to characterize when the zonal mean wind near the equator at a particular level is easterly the monthly mean wind has only very small zonal contrasts when mean westerlies are present near the equator significant zonal asymmetries occur at low latitudes most notably easterly anomalies over south america and westerly anomalies in the eastern pacific region these anomalies generally display a continuous meridional phase propagation with the extratropical quasi stationary eddy field in the winter hemisphere the net result is a significantly weaker peak to peak amplitude of the quasi biennial oscillation qbo in zonal wind over the south american sector than over the rest of the equatorial band the zonal contrast in qbo amplitude near 10 hpa exceeds 10 in the lower stratosphere the zonal asymmetries in the prevailing wind are fairly small asymmetries seem to reflect the upward extension of the tropospheric walker circulation and are less strongly modulated by the quasi biennial oscillation in zonal mean circulation the model results were checked against limited station observations at nairobi 1 38s 36 78e singapore 1 48n 103 98e rochambeau 4 88n 52 48w and bogota 4 78n 74 18w overall reasonable agreement was found between the monthly mean zonal winds in the model simulation and these station data the low latitude wind field in monthly mean ncep gridded analyses was also examined these analyses have some obviously unrealistic features in the tropical stratosphere but some of the behavior seen in the skyhi model simulations can be identified as well in the ncep analyses

a climatology of stratospheric polar vortices and anticyclones 1 united kingdom meteorological office global analyses from 1991 to 2001 are used to create a global climatology of stratospheric polar vortices and anticyclones new methodologies are developed that identify vortices in terms of evolving three dimensional 3 d air masses a case study illustrates the performance of the identification schemes during february and march of 1999 when a merger of anticyclones led to a stratospheric warming that split the arctic polar vortex the 3 d structure and temporal evolution of the arctic vortex and identified anticyclones demonstrates the algorithm s ability to capture complicated phenomena the mean geographical distribution of polar vortex and anticyclone frequency is shown for each season the frequency distributions illustrate the climatological location and persistence of polar vortices and anticyclones a counterpart to the aleutian high is documented in the southern hemisphere the australian high the temporal evolution of the area occupied by polar vortices and anticyclones in each hemisphere is shown as a function of potential temperature large polar vortex area leads to an increase in anticyclone area which in turn results in a decrease in the size of the polar vortex during northern winter and southern spring 9 years of daily anticyclone movement are shown on the 1200 k 36 km 4 hpa isentropic surface preferred locations of anticyclogenesis are related to cross equatorial flow and weak inertial stability regimes of traveling and stationary anticyclones are discussed index terms 3309 meteorology and atmospheric dynamics climatology 1620 3319 meteorology and atmospheric dynamics general circulation 3334 meteorology and atmospheric dynamics middle atmosphere dynamics 0341 0342 keywords polar vortex stratospheric anticyclones

climatology of the equatorial lower stratosphere abstract twenty years of radiosonde data have been analyzed in an attempt to develop a latitudinal structure climatology of winds temperature and geopotential at 30 and 50 mb in the equatorial stratosphere the fine latitudinal resolution provided by the wmo station network reveals several interesting features in the latitudinal structure of the annual and quasi biennial cycles which dominate this region for example the westerly and easterly acceleration phases of the quasi biennial oscillation are markedly different westerly accelerations appear first at the equator spreading outward with time to higher latitude and an more intense on average than the easterly accelerations the easterly accelerations are more uniform in latitude but leer uniform in time sometimes occurring in two stages the quasi biennial wind and temperature oscillations are symmetric about the equator while the annual harmonic in zonal wind is antisymmetric about the equator but is not proportional to the coriolis paramete

the influences of zonal flow on wave breaking and tropical extratropical interaction in the lower stratosphere abstract the influences of the zonal mean flow on rossby wave breaking and tropical extratropical interaction in the lower stratosphere are investigated using a high resolution barotropic model it is found that the zonal mean wind in the subtropics of the winter hemisphere denoted as 30 is pivotal to the location and intensity of rossby wave breaking when 30 is positive and relatively large significant wave breaking occurs in two regions one in the midlatitudes of the winter hemisphere and the other in the tropics when 30 is small or negative on the other hand wave breaking occurs primarily in the middle to high latitudes of the winter hemisphere it is also found that when 30 is large wave breaking is sensitive to the phase of the equatorial quasi biennial oscillation qbo in that if the qbo is westerly significant wave breaking takes place in the midlatitudes of the winter hemisphere and the subtropics of the summer hemisphere and no wave breaking occurs in the equatorial region and

dynamical response in the northern hemisphere midlatitude and high latitude winter to the qbo simulated by ccsr nies ccm 1 an analysis of the relationship between zonal wind in the equatorial stratosphere and zonal wind temperature and eliassen and palm e p flux in the northern hemisphere extratropical winter was performed using the ccsr nies chemistry climate model ccm and the japanese 25 year reanalysis jra 25 data the tropical zonal wind of the ccm was forced by observations including the observational equatorial quasi biennial oscillation qbo the influence of the qbo on the northern hemisphere winter was estimated by a composite analysis with statistical significance the analyses suggest that the difference in latitude of the critical line zero value line of zonal wind in the low latitudes around 10 hpa as well as 50 hpa between the easterly and westerly phases is related to the wave propagation and circulation over the whole depth of the stratosphere the circulation anomaly is further related to the temperature anomaly at the northern hemisphere midlatitudes and the zonal wind anomaly at the high latitudes these results suggest a mechanism through which 10 hpa qbo could influence the polar vortex while the mechanism of 50 hpa qbo influence is unclear but the possibility is not ruled out

nonlinear relation of the arctic oscillation with the quasi biennial oscillation a nonlinear principal component analysis nlpca is applied to a set of monthly mean time series from january 1956 to december 2007 consisting of the arctic oscillation ao index derived from 1 000 hpa geopotential height anomalies poleward of 20 n latitude and the zonal winds observed at seven pressure levels between 10 and 70 hpa in the equatorial stratosphere to investigate the relation of the ao with the quasi biennial oscillation qbo the nlpca is conducted using a new compact neural network model the nlpca modeling of the dataset of the ao index and qbo winds offers a clear picture of the relation between the two oscillations in particular the phase of covariation of the oscillations defined by the two nonlinear principal components of the dataset progresses with a predominant 28 4 month periodicity this predominant cycle is modulated by an 11 year cycle the variation of the ao index with the qbo phase also shows that the average ao index is positive when the westerly qbo phase descends past 30 hpa and conversely the average ao index is negative when the easterly qbo phase descends past 30 hpa this relationship is evident during the boreal cold season from november to april but non existent during the boreal warm season from may to october

effects of the quasi biennial oscillation on low latitude transport in the stratosphere derived from trajectory calculations 1 the quasi biennial oscillation qbo of stratospheric zonal winds induces a secondary meridional circulation smc consisting of qbo variations in meridional and vertical winds in this work we investigate how these instantaneous meridional circulation anomalies add over time to variations of stratospheric transport to that end we compute backward parcel trajectories on the basis of the output of a chemistry climate model ccm at the equator the trajectories show the strongest vertical parcel displacement over a seasonal timescale when the qbo progresses toward easterly phase in the middle stratosphere during the solstitial seasons a large number of parcels come from the summer hemisphere causing in addition a qbo variation in the spread of the total ascent among equatorial parcels a qbo effect on meridional transport is diagnosed from pv gradients during summer in the easterly phase of the qbo which suggests a variation of the tropical subtropical barrier strength analyses of the parcel trajectories and ccm trace gas distributions confirm this finding we suggest that this variation is due to the combined effects of qbo and annual variation in meridional advection and in wave induced eddy transport

connections between the stratospheric quasi biennial oscillation and tropospheric circulation over asia in northern autumn 1 we investigate the variations in tropospheric circulation over asia associated with the stratospheric quasi biennial oscillation qbo during northern hemisphere nh autumn september november using the national centers for environmental prediction national center for atmospheric research ncep ncar reanalysis and ncep department of energy doe reanalysis ii data sets for a 25 year period 1980 2004 the anomaly fields in this study are expressed as the easterly years minus the westerly years of the qbo the zonal wind distribution at 200 hpa indicates easterly anomalies at low latitudes from india through taiwan statistically significant westerly anomalies at midlatitudes including the tibetan plateau to northern china and significant easterly anomalies in the high latitude eurasia north of 50 n a momentum balance analysis indicates that these anomalies over asia are attributable to atmospheric waves and residual mean meridional flow significant northward and descending anomalies are observed in the lower stratosphere over asia with detectable signals in the troposphere around tibet the adiabatic heating due to descending motions in the region centering on india and bangladesh is consistent with the distribution of rainfall anomalies the formation of zonal wind anomalies over south asia seems to be associated with not only wave activities but also adiabatic heating and thermal advection we suggest that the qbo may be linked to tropospheric circulation over asia through wave activities and convective activities in autumn and the wave activities in the low latitudes associated with the qbo seem to be connected with the rainfall distribution over the asian monsoon region

model studies of the interannual variability of the northern hemisphere stratospheric winter circulation the role of the quasi biennial oscillation a series of experiments are described that examine the sensitivity of the northern hemisphere winter evolution to the equatorial quasi biennial oscillation qbo the prime tool for the experiments is a stratosphere mesosphere model the model is integrated over many years with the modelled equatorial winds relaxed towards observed values in order to simulate a realistic qbo in experiment a the equatorial winds are relaxed towards singapore radiosonde observations in the height region 16 32 km in contrast to previous modelling studies the holton tan relationship warm cold winters associated with easterly westerly qbo winds in the lower stratosphere is absent however in a second experiment run b in which the equatorial winds are relaxed towards rocketsonde data over the extended height range 16 58 km a realistic holton tan relationship is reproduced a series of further studies are described that explore in more detail the sensitivity to various equatorial height regions and to the bottom boundary forcing the experiments suggest that the evolution of the northern hemisphere winter circulation is sensitive to equatorial winds throughout the whole depth of the stratosphere and not just to the lower stratospheric wind direction as previously assumed

interaction of extratropical rossby waves with westerly quasi biennial oscillation winds the role of laterally radiating stratospheric rossby waves from the winter hemisphere in the momentum balance of the quasi biennial oscillation qbo remains an unresolved issue observations of extratropical rossby waves penetrating close to the equator suggest that rossby wave absorption in the tropics must occur at least occasionally this paper presents numerical simulations using a global shallow water model to examine the pattern of wave absorption at low latitude during the westerly wind phase of the qbo earlier results indicating that extratropical rossby waves radiating to the equator do not break there when the qbo phase is westerly are reproduced it is shown that the westerly qbo jet can persist undiminished at its core over seasonal length integrations because the laterally radiating rossby waves are absorbed along the qbo jet s flanks where easterly acceleration occurs the net effect of the rossby waves on the westerly qbo jet is a reduction in the width of its meridional profile but not its core strength this behavior is interpreted by considering the filtering of equatorward radiating rossby waves by critical layer absorption a process that depends on the background zonal mean wind and the waves phase speed and amplitude the simulations also show that adequate horizontal resolution is needed to capture the suppression of wave breaking at the qbo jet core and persistence of the jet core strength over seasonal timescales the implications of this result for simulations of the qbo in general circulation models are considered

biogeochemical processes in infiltration basins and their impact on the recharging effluent the soil aquifer treatment sat system of the shafdan plant israel abstract soil aquifer treatment sat systems utilize infiltration basins for recharging pre treated effluent into the aquifer for water quality improvement the present research focuses on the diurnal and seasonal variations of oxygen carbon and nitrogen species in the infiltration basins and in the uppermost vadose zone for determining the impact of different environmental conditions on the composition of the infiltrating effluent the study was conducted in one of the infiltration basins of the dan region sewage reclamation project shafdan israel solar radiation and aeration were recognized to be the two main factors controlling the chemical composition of the effluent within the basin and the uppermost vadose zone the effluent entering the basin show initial enrichment with dissolved oxygen do due to gas exchange caused by injection through the inlet fountain and turbulence during basin filling the do ph and dissolved inorganic carbon dic fluctuate diurnally as a result of intense in basin daylight photosynthesis and nighttime respiration do and ph increase during day and decrease during night and the dic shows an opposite behavior the daylight net primary production was 240 mol l 1 d 1 and the diurnal respiration rate was 430 mol l 1 d 1 assuming that the nighttime respiration rate is constant over a whole diurnal cycle the gross primary production during daylight was 450 mol l 1 d 1 dissolved organic carbon doc and inorganic nitrogen species nh 4 no 3 varied significantly in the uppermost vadose zone however neither the vadose zone nor the basin showed diurnal fluctuations it appears that chemical variations between three sampling campaigns conducted in different seasons stemmed mainly from the efficiency of basin aeration that resulted from changes in basin s operation regime and local environmental conditions the results of this study lead to the following basin management recommendations 1 keeping short flooding and drying cycles and allowing complete basin desiccation before the next flooding and 2 flooding the basin during daytime starting at dawn to maximize oxygen production and minimize infiltration during nighttime following these routines would result in higher redox potential of the infiltrating effluent

modeling the quasi biennial oscillation s influence on isentropic tracer transport in the subtropics tracer transport in the lower stratosphere is investigated using an off line semi lagrangian transport model and winds from a mechanistic three dimensional middle atmosphere model interpolated to the 650 k isentropic surface over a winter season by comparing two simulations the effect of the quasi biennial oscillation s qbo s easterly or westerly wind phases on low latitude transport is examined especially regarding the formation of an apparent subtropical transport barrier at the equatorward edge of the surf zone the tracer field is diffused less than potential vorticity pv and shows sharper gradients and finer structures developing over the winter in both qbo phases the winter extratropical surf zone is bounded by large tracer gradients equatorward of about 15 latitude the inability of quasi stationary rossby waves to propagate into qbo easterlies leads to a much sharper edge forming between the rapidly stirred extratropical surf zone and the relatively unstirred tropics during the easterly qbo phase than occurs during the westerly qbo phase in the westerly phase some rossby wave activity can propagate across the equatorial westerlies and break on reaching the summer hemisphere easterly winds causing mixing there simulations using a tracer initially confined to the tropics show that more tropical air is mixed out to the winter extratropics by rossby wave stirring when the qbo phase is easterly despite the sharper band of stronger tracer or pv gradient which separates the tropics and the winter extratropics in this phase while air was mixed out of the tropics in both qbo phase simulations neither qbo phase simulation showed extratropical air being irreversibly mixed into the tropics these results are related to observations of the tropical reservoir of stratospheric aerosols especially the dynamics and transport of its winter hemisphere boundary

enhancement of rossby wave breaking by steep potential vorticity gradients in the winter stratosphere this work investigates the extent to which potential vorticity gradients affect the vertical propagation of planetary scale rossby waves on the edge of a stratospheric polar vortex and their eventual nonlinear saturation and breaking using two different numerical modeling approaches it is shown that wave propagation and wave breaking are significantly reduced when the potential vorticity gradients at the vortex edge are anomalously weak the efficiency of the first model based on high resolution contour dynamics permits a full exploration of the parameter space of wave forcing amplitude and edge steepness a more realistic primitive equation model in spherical geometry both confirms the contour dynamics results and highlights some direct implications for stratospheric modeling in more comprehensive models the results suggest that stratospheric models using horizontal resolutions of spectral t42 or less may significantly underestimate the vertical propagation and breaking of planetary waves and may consequently misrepresent such important stratospheric processes as the mean meridional circulation sudden warmings and the mixing of chemically distinct polar and midlatitude air

the influence of the quasi biennial oscillation on global constituent distributions long lived stratospheric constituents observed by the upper atmosphere research satellite are compared between late northern winters 1991 1992 and 1992 1993 the phase of the quasi biennial oscillation qbo was such that the equatorial zonal wind was easterly westerly in the lower stratosphere during the first second winter in the tropics winter to winter differences in the latitude height distribution of zonally averaged n 2 o and h 2 o are associated with differences in large scale upwelling the qbo s mean meridional circulations and lateral mixing by incident extratropical rossby waves in the extratropics significant differences in zonally averaged n 2 o and h 2 o are also found which are believed to represent the extratropical constituent qbo the transport processes creating the extratropical constituent qbo are tentatively identified in the winter extratropics qbo modulation of the residual circulation appears to dominate in the upper stratosphere while qbo modulated rossby wave isentropic mixing dominates below about 10 mbar analysis of rossby waves at low latitudes as deduced from isobaric constituent distribution maps suggests that the meridional distribution of rossby wave breaking depends on the tropical zonal winds easterly qbo winds prevent rossby wave radiation into the tropics so that a strong constituent concentration gradient is generated in the winter subtropics westerly qbo winds allow some wave radiation into the tropics accompanied by isentropic mixing in the winter subtropics cross equatorial propagation and occasional mixing in the summer subtropics these effects depend on altitude and appear to vary in accord with the descending phases of the qbo

assessing the numerical accuracy of complex spherical shallow water flows abstract the representation of nonlinear shallow water flows poses severe challenges for numerical modeling the use of contour advection with contour surgery for potential vorticity pv within the contour advective semi lagrangian casl algorithm makes it possible to handle near discontinuous distributions of pv with an accuracy beyond what is accessible to conventional algorithms used in numerical weather and climate prediction the emergence of complex distributions of the materially conserved quantity pv in the absence of forcing and dissipation results from large scale shearing and deformation and is a common feature of high reynolds number flows in the atmosphere and oceans away from boundary layers the near discontinuous pv in casl sets a limit on the actual numerical accuracy of the eulerian grid based part of casl for the spherical shallow water equations the limit is studied by comparing the accuracy of casl algorithms with second order centered fourth order compact and sixth order sup

mountain mass denudation and piedmont formation in the mojave and sonoran deserts map analysis of 45 mountain masses migration of the piedmont junction in embayments extends the piedmont by removing the divides between the embayments whereas migration of the piedmont junction along the mountain front causes the piedmont to be extended by mountain front retreat in the mountain masses studied the percentage of the total piedmont junction occurring in embayments epj is directly related to the area a of a mountain mass and inversely related to its relief r and a and r together account for 81 percent of the variation in epj inasmuch as the former relationship dominates the latter it is evident that as a mountain mass diminishes in size there is a tendency for epj to decrease and hence for divide removal to become progressively less important relative to mountain front retreat field data suggest 1 that channels are capable of turning abruptly after issuing from a mountain mass and of eroding more than half the mountain front in some mountain masses 2 that nevertheless hillslope processes usually affect a greater part of the mountain front than channel processes and 3 that even in embayments hillslope processes usually play an important role in piedmont junction migration modified journal abstract

tectonic climatic and lithologic influences on landscape fractal dimension and hypsometry implications for landscape evolution in the san gabriel mountains california east west variation in tectonic activity and strong north south climatic gradients provide a unique opportunity to study tectonic climatic and lithologic influences on landscape evolution in the san gabriel mountains california the competing tendencies of constructive tectonic and degradational climatic effects act against lithologic resistance to influence fluvial systems and thus the nature of adjacent and nested drainage basins landscape fractal dimension d a measure of surface roughness over a variety of scales and the hypsometric integral i a measure of the distribution of landmass volume above a reference plane are useful measures of altitudinal variation with scale as such they may provide clues as to the relative influences of tectonism climate and rock type topographic analyses of the san gabriel mountains clearly indicate that tectonism strongly influences d at range wavelength scales while rock type variation apparently influences d and i at smaller scales tectonism is also shown to influence i across the mountain piedmont junction at all scales investigated tectonic activity shows strong negative correlation with both i and d because tectonically active portions of the mountain front do not allow time for much landscape dissection by lower order streams three dimensional topographic modeling suggests climatic parameters exert a stronger influence on d than does tectonism this modeling also suggests an inverse correlation between range scale d and i with varying climate and uplift rate a positive correlation is observed in the san gabriel mountains we suggest this difference results from 1 differences in uplift style between the san gabriel mountains and the models and or 2 variation in rock type erodibility present in the san gabriel mountains but which was not modeled we postulate that the interaction of tectonic climatic and lithologic parameters influences the stable i and d to which a landscape evolves key questions remaining include 1 the time required to reach a stable i or d after a climatic or tectonic change 2 what does the fractal nature of topography tell us about the scaling characteristics of major landforming processes 3 how does climate influence range scale i and both range and small scale d and 4 what are the effects on i and d of range scale lithologic variation both in the models and in real landscapes

seasonal variation of clogging of an artificial recharge basin in a northern climate abstract the decrease of infiltration rate and the depth cause and hydraulic effect of clogging were evaluated for a sandy artificial recharge test basin during the application of water containing between 51 and 61 mg l 1 suspended solids infiltration rate decreased by two orders of magnitude under fall operational conditions for a clean sand surface clogging was caused by clay deposition within the basin soil profile during early operation times 19 75 h followed by the complete interception of sediment in the surface filter cake during later operational times impedance decreased by two to three orders of magnitude in the surface 8 cm and by zero to two orders of magnitude from 8 to 38 cm increased clay content following basin operation was measured to a depth of 5 cm during the spring test sediment movement and deposition were similar to the fall test in addition carbonates and iron oxyhydroxides precipitated causing cementation of the surface soil grains the cementation caused increased hydraulic impedance and resulted in a decrease of total recharge carbonate precipitation was caused by increased basin water ph resulting from algal photosynthesis allowing the basin to dry and crack for ten days resulted in a substantial recovery 64 of infiltration rate following the drying treatment the basin reclogged more quickly than for the previous test on clean sands and the impedance of the surface layer reached values larger than those prior to the drying treatment the decrease of impedance caused by drying was confined to the surface layer and no effect was observed below 8 cm following the natural drying treatment total recharge was about half that of the clean basin

sensitivity of the boreal winter circulation in the middle atmosphere to the quasi biennial oscillation in maecham5 simulations the polar vortex in the northern hemisphere exhibits high intraseasonal and interannual variability which to some degree may be controlled by the quasi biennial oscillation qbo in the tropical stratosphere here we analyze the qbo signal in the northern hemisphere polar vortex in a model simulation using the general circulation model maecham5 middle atmosphere european center hamburg model which simulates the qbo as an internal mode of variability composites have been computed for the westerly and easterly qbo phases from early winter to late winter november december december january and january february of a 50 year experiment containing 20 complete qbo cycles this method identifies tropical and midlatitude patterns in wind and temperature that are related to the secondary meridional circulation of the qbo extending towards the winter pole in the tropics significant qbo signature is observed in the mesosphere up to 0 05 hpa only in early winter and mainly in the easterly qbo phase forced by the parameterized gravity waves mean flow interaction at high latitudes maecham5 shows a significantly warmer colder polar stratosphere in the easterly westerly qbo phase at 30 hpa accompanied by a weaker stronger polar vortex in the late winter months from december to february december to january in the easterly westerly phase of the qbo in early winter there is no significant change in temperature and zonal mean zonal wind in the polar stratosphere the analysis of ep fluxes shows a different behavior between qbo phases with changes in the waveguide wave propagation occurs upwards and polewards in the easterly qbo phase at 30 hpa while waves are refracted equatorward in the westerly phase no relationship has been found between the tropical qbo and the final warming at the end of the boreal winter

forcing mechanism of the seasonally asymmetric quasi biennial oscillation secondary circulation in era 40 and maecham5 1 the seasonality of the quasi biennial oscillation qbo and its secondary circulation is analyzed in the european reanalysis era 40 and middle atmosphere european centre hamburg model maecham5 general circulation model data sets through the multitaper method singular value decomposition mtm svd in agreement with previous studies the results reveal a strong seasonal dependence of the qbo secondary circulation this is characterized by a two cell structure symmetric about the equator during autumn and spring however anomalies strongly weaken in the summer hemisphere and strengthen in the winter hemisphere leading to an asymmetric qbo secondary circulation characterized by a single cell structure displaced into the winter hemisphere during the solstices in era 40 this asymmetry is more pronounced during the northern than during the southern winter these results provide the first observation of the qbo secondary circulation asymmetries in the era 40 reanalysis data set across the full stratosphere and the lower mesosphere up to 0 1 hpa the mtm svd reconstruction of the seasonal qbo signals in the residual circulation and the qbo signals in eliassen palm ep flux divergences suggest a particular mechanism for the seasonal asymmetries of the qbo secondary circulation and its extension across the midlatitudes the analysis shows that the qbo modulates the ep flux in the winter hemispheric surf zone poleward of the qbo jets the zonal wind forcing by ep flux divergence is transformed by the coriolis effect into a meridional wind signal the seasonality in the stratospheric ep flux and the hemispheric differences in planetary wave forcing cause the observed seasonality in the qbo secondary circulation and its hemispheric differences

coupling of the quasi biennial oscillation and the extratropical circulation in the stratosphere through planetary wave transport abstract a significant fraction of the interannual variability of the wintertime stratosphere in the northern hemisphere is related to the quasi biennial oscillation qbo in tropical winds disturbed conditions of the polar night vortex are favored in years when the winds over the equator are easterly more quiescent conditions prevail at high latitudes when the phase of the tropical qbo is westerly the effects of tropical winds on the extratropical circulation are studied in the equivalent barotropic framework on the sphere calculations are performed with the tropical flow representative of easterly and westerly phases of the qbo with planetary wave forcing representative of conditions in the lower stratosphere the wintertime polar vortex is highly disturbed during the easterly phase of the qbo the evolution taking the form of a canadian warming in contrast more quiescent conditions prevail with the same forcing but with tropical winds representative of the westerly phase of the qbo the vortex

nonlinear latitudinal transfer of wave activity in the winter stratosphere partial support for this work was provided through the national science foundation award ags 1333029

streamers observed by the crista experiment and simulated in the kasima model data from the cryogenic infrared spectrometers and telescopes for the atmosphere crista showed three narrow streamers of air with tropical mixing ratios of hno3 and n2o pointing from the tropics toward middle latitudes in the middle stratosphere on november 6 1994 by means of the mechanistic prognostic model the diagnostic chemical transport model ctm and the combined nudged model which are all versions of the karlsruhe simulation model of the middle atmosphere kasima the hypothesis is checked of whether these streamers are due to adiabatic transport processes on a timescale of days whereas the prognostic model reproduces the northern hemisphere streamers only qualitatively in their position the ctm and the nudged model show a good agreement between their simulated tracer structures and the observed streamers because of the clear streamer signal in the nudged model compared to the ctm its data are used for the investigation of isentropic tracer deformations they show that the northern hemisphere streamers are mainly built by adiabatic transport on a timescale of days rossby wave breaking plays a role in the dissolution of the streamers in the southern hemisphere the production of ertel s potential vorticity epv and the net heating rate is large and the observed streamers are therefore not reproduced in the epv moreover the isentropic deformations of the epv due to the horizontal flow are that strong during a minor warming in the end of october that the reproduction of the southern hemisphere streamer by means of artificial tracers fails

seasonal variation of isentropic transport out of the tropical stratosphere the seasonal variation of the isentropic transport out of the tropical stratosphere is examined using contour advection calculations with winds from meteorological analyses for the period july 1991 to june 1994 calculations using winds from three different meteorological analyses are compared there is good qualitative agreement between the different calculations for extratropical structures but not for structures in the tropics there is also reasonable agreement between area diagnostics for transport out of the tropics derived from these calculations transport out of the tropics occurs in rossby wave breaking events in which filaments of tropical air are drawn into middle latitudes in all years these wave breaking events occur during the fall to spring period when there are westerlies throughout middle latitudes late september to early may in the northern hemisphere this includes periods before the formation of and after the breakup of the polar vortex in the northern hemisphere the rate of transport out of the tropics during fall to spring fluctuates around a constant value whereas in the southern hemisphere there is a relatively quiet midwinter period with maxima in the transport in early and late winter