on temperature inversions and the mesospheric surf zone 1 mesospheric thermal inversions are investigated in a numerical simulation with the whole atmosphere community climate model an upward extension of the national center for atmospheric research s community climate model the seasonal character spatial extent and magnitude of the inversion layers are realistic during winter in the model the occurrence of wintertime inversions is a direct consequence of the rapid decay with height of vertically propagating planetary waves which induces large temperature perturbations in the upper mesosphere to maintain hydrostatic equilibrium the magnitude of the inversions is highly correlated with planetary wave amplitude so that large inversions develop during episodes of planetary wave amplification gravity waves do not play a major direct role in the formation of the inversions because the largest thermal tendencies associated with gravity wave breaking occur well above the range of altitudes where inversions are found however gravity waves play an essential indirect role because they set up a critical line in the upper mesosphere where rossby waves break in the mesospheric surf zone

connection between weak stratospheric vortex events and the pacific decadal oscillation we investigate the possible impacts of the pacific decadal oscillation pdo on the occurrence of weak stratospheric polar vortex wsv events in the northern hemisphere winter wsv events which are defined when polar cap geopotential height anomalies at 50 hpa fall below the 10th percentile in winter are observed more frequently during positive pdo phases than during negative pdo phases additionally tropospheric wave forcings that drive wsv events are remarkably different between the two phases of the pdo during the positive pdo phase the vertical propagation of wavenumber one waves plays a predominant role with a rather minor contribution of wavenumber two waves this contrasts with the negative pdo phase when the wsv events are primarily caused by wavenumber two waves this difference is partly related to the pdo induced tropospheric circulation anomalies over the north pacific whose zonal wavenumber one component constructively destructively interferes with climatological planetary scale waves during positive negative pdo winters the predominant wavenumber two wave forcings during the negative pdo phase are likely related to the enhanced tropospheric eddy activity over alaska that results from the poleward shift of the pacific jet in response to the negative pdo

altered atmospheric responses to eastern pacific and central pacific el ninos over the north atlantic region due to stratospheric interference the two types of el nino that have been identified namely the eastern pacific ep and central pacific cp el ninos are known to exert different climatic impacts on the north atlantic region during winter here we investigate the characteristics of the teleconnection of the two el nino types with a focus on the stratosphere troposphere coupling during the ep el nino polar stratospheric warming and polar vortex weakening frequently occur with a strong tendency for downward propagation near the tropopause consequently the atmospheric pattern within the troposphere over the north atlantic sector during midwinter closely resembles the negative north atlantic oscillation pattern in contrast during cp el nino events stratospheric warming events exhibit a much weaker downward propagation tendency this difference in the stratospheric circulation response arises from the different seasonal evolution of the tropospheric wave response to the two el nino types for the ep el nino the aleutian low begins growing during december and is sustained throughout the entire winter december to february which provides favorable conditions for the continuous downward propagation of the stratospheric warming we also discuss the origin of the difference in the teleconnections from the two types of el nino associated with the distinct longitudinal position of the warm sst anomaly that determines troposphere stratosphere coupling

dynamical mechanism for the increase in tropical upwelling in the lowermost tropical stratosphere during warm enso events the brewer dobson circulation strengthens in the lowermost tropical stratosphere during warm el nino southern oscillation enso events dynamical analyses using the most recent version of the whole atmosphere community climate model show that this is due mainly to anomalous forcing by orographic gravity waves which maximizes in the northern hemisphere subtropics between 18 and 22 km especially during the strongest warm enso episodes anomalies in the meridional gradient of temperature in the upper troposphere and lower stratosphere utls are produced during warm enso events accompanied by anomalies in the location and intensity of the subtropical jets this anomalous wind pattern alters the propagation and dissipation of the parameterized gravity waves which ultimately force increases in tropical upwelling in the lowermost stratosphere during cold enso events a similar signal but of opposite sign is present in the model simulations the signals in ozone and water vapor produced by enso events in the utls are also investigated

on the nonuniqueness of sediment yield at the catchment scale the effects of soil antecedent conditions and surface shield the understanding of reasons leading to nonuniqueness of soil erosion susceptibility is still inadequate yet indispensable for establishing general relations between runoff volume and sediment yield to obtain relevant insights we performed a series of numerical simulations with a detailed hydrodynamic model using synthetic storms of varying intensity duration and lag time between events as representations of different hydrologic response conditions in a zero order catchment the design targeted to generate surface flow and perturb soil substrate by a first rainfall event creating a set of initial conditions in terms of flow and deposited sediment prior to the onset of a subsequent rainfall event due to the differential effect of re detachment and re entrainment processes on soil particles of varying sizes the deposited sediment mass formed shielding layer one of the essential results is that unless the initial condition of flow and sediment is identical the same volume of runoff can generate different total sediment yields and their variation can reach up to 200 the effect is attributed to two major conflicting effects exerted by the deposited initialization soil antecedent condition sediment mass erosion enhancement because of supply of highly erodible sediment and erosion impediment because of constrain on the availability of lighter particles by heavier sediment consistently with this inference long term simulations with continuous rainfall show that a peculiar feature of sediment yield series is the existence of maximum before the steady state is reached the two characteristic time scales the time to peak and the time to steady state separate three characteristic periods that correspond to flow limited source limited and steady state regimes these time scales are log linearly and negatively related to the spatially averaged shields parameter the smaller the rainfall input and the heavier a given particle is the larger the two scales are the results provide insights on how the existence of shield operates on erosion processes possibly implying that accurate short term predictions of geomorphic events from headwater areas may never become a tractable problem the latter would require a detailed spatial characterization of particle size distribution prior to precipitation events

the el nino southern oscillation enso modoki signal in the stratosphere el nino southern oscillation enso is known to be the largest source of interannual variability in the tropical troposphere however the variability in the tropical pacific since 1979 seems to be associated not only with canonical enso events but also with a variation thereof known as enso modoki which is characterized by warm anomalies in the central pacific west from those occurring during a typical enso this works analyzes the signal of enso modoki in the stratosphere and compares it to canonical enso by using the chemistry climate whole atmosphere community climate model waccm3 5 the results reveal a significant warming in the southern hemisphere polar stratosphere during boreal winter months which propagates downward in early spring this is absent during canonical warm enso events on the other hand in the northern hemisphere stratosphere the anomalous warming typical of canonical el nino episodes during boreal winter is not statistically significant during el nino modoki events these differences are related in waccm3 5 to changes in tropical convection and tropospheric teleconnections associated with each type of event in particular an enhancement and westward displacement of the anomalous convective area during el nino modoki episodes is related to an intensification of the pacific south american teleconnection pattern and a weakening of the aleutian low during cold enso modoki events a significant anomalous cooling is present in the model simulations

initial transient response of the winter polar stratospheric vortex to idealized equatorial pacific sea surface temperature anomalies in the ncar waccm abstractperpetual winter simulations using the ncar whole atmosphere community climate model waccm are conducted to document the differences of the initial transient response of the boreal winter northern hemisphere stratospheric polar vortex to central cpw and eastern pacific warming epw events idealized patches of positive sea surface temperature sst anomalies are superimposed onto a climatological sst field to mimic canonical cpw and epw forcings a 20 member ensemble was created by varying initial atmospheric conditions for both cpw and epw cases in the ensemble average the vortex weakens under both cpw and epw forcing indicated by a negative zonal mean zonal wind tendency this tendency is mainly tied to changes in the eddy driven mean meridional circulation mmc a negative anomaly in the eddy momentum flux convergence also plays a secondary role in the weakening the vortex response however differs dramatically among individual ensemble members a few ensemble members exhibit initial

effects of soil surface roughness on interrill erosion processes and sediment particle size distribution abstract soil surface roughness significantly impacts runoff and erosion under rainfall few previous studies on runoff generation focused on the effects of soil surface roughness on the sediment particle size distribution psd which greatly affects interrill erosion and sedimentation processes to address this issue a rainfall simulation experiment was conducted with treatments that included two different initial soil surface roughnesses and two rainfall intensities soil surface roughness was determined by using photogrammetric method for each simulated event runoff and sediment samples were collected at different experimental times the effective undispersed psd of each sediment sample and the ultimate after dispersion psd were used to investigate the detachment and transport mechanisms involved in sediment movement the results show that soil surface roughness significantly delayed runoff initiation but had no significant effect on the steady runoff rate however a significant difference in the soil loss rate was observed between the smooth and rough soil surfaces sediments from smooth soil surfaces were more depleted in clay size particles but more enriched in sand size particles than those from rough soil surfaces suggesting that erosion was less selective on smooth than on rough soil surfaces the ratio of different sizes of transported sediment to the soil matrix indicates that most of the clay was eroded in the form of aggregates silt size particles were transported mainly as primary particles and sand size particles were predominantly aggregates of finer particles soil surface roughness has a crucial effect on the sediment size distribution and erosion processes significant differences of the enrichment ratios for the effective psd and the ultimate psd were observed under the two soil surface roughness treatments these findings demonstrate that we should consider each particle size separately rather than use only the total sediment discharge in assessing and modeling interrill erosion processes

impact of tropical sst on stratospheric planetary waves in the southern hemisphere abstractthe impact of tropical sea surface temperature sst on stratospheric planetary waves in the southern hemisphere sh is investigated in austral spring using observed sst and reanalysis data for the past three decades maximum covariance analysis indicates that the tropical sst and the sh stratospheric planetary wave activity are primarily coupled through two modes the leading two modes show the la nina like and the central pacific el nino like sst anomalies in their positive polarities respectively which each are related to enhanced stratospheric planetary wave activity these two modes also introduce phase shifts to the stratospheric stationary planetary waves a westward shift is seen for la nina and an eastward shift for warm sst anomalies is seen in the central pacific the eliassen palm fluxes associated with the two modes indicate that the anomalous stratospheric wave activity originates in the troposphere and propagates upward over the mid high latitudes so that the linkages between tr

enso influences on southern hemisphere column ozone during the winter to spring transition 1 this study investigates how the el nino southern oscillation enso modulates the distribution of column ozone during the southern hemisphere sh winter to spring transition when a zonal asymmetry in column ozone develops near 55 s with a maximum south of australia enso differences in column ozone and planetary wave structure are explored for the average of seven el nino en versus six la nina ln events during 1982 2004 a westward shift in convection during ln corresponds to a 30 50 westward shift of sh planetary wave and column ozone patterns the extratropical lower stratospheric temperature anomalies are inversely correlated with tropical anomalies in similar longitude bands and are highly correlated with local column ozone anomalies the tropical signal is communicated to higher latitudes by modulating subtropical anticyclones with distinctive responses for en and ln years for each month during august and en a subtropical anticyclone extends from south america to south africa and the wave one asymmetry of the antarctic vortex is more pronounced and shifted eastward along with column ozone in september and en a strong anticyclone exists over south africa with a corresponding cold ozone poor anomaly in the stratosphere diminishing the western edge of the ozone maximum in october and ln a strong anticyclone exists over australia with an amplified trough on its poleward flank this trough is overlain by an ozone rich warm anomaly which expands the western edge of the ozone maximum and the polar vortex asymmetry is amplified and rotated westward

a general circulation model study of january climate anomaly patterns associated with interannual variation of equatorial pacific sea surface temperatures abstract a general circulation model has been run in the perpetual january mode to produce several long term simulations each distinguished by a different imposed equatorial pacific sea surface temperature from each of them simulations we have extracted an eight member ensemble of 90 day averaged fields ensemble mean difference maps are presented in this paper together with an estimate of the statistical significance of features which appear in thee maps these results are compared with observational studies in the literature that present difference maps of northern hemisphere winter fields composited according to some index related to the two extremes of equatorial pacific sea surface temperature variation the results show many anomaly patterns of high statistical significance that are also in good agreement with those observed in the tropics them include 990 mb wind sea level pressure and rainfall anomalies constituting the southern oscillation as well as a 200 mb height anomaly at all longitud

an examination of observed southern oscillation effects in the northern hemisphere stratosphere abstract the effects of the southern oscillation on the december february mean circulation in the northern hemisphere stratosphere were investigated using 34 years of data no evidence for a significant relation between the southern oscillation so and the zonally averaged flow is found for any region poleward of 20 n the effects of the tropical quasi biennial oscillation qbo on the zonal mean flow are much stronger and this complicates the detection of 50 effects some more suggestive results are evident when hemispheric maps of height anomalies at 50 or 30 mb are composited for the warm extremes of the 50 the present findings are broadly consistent with earlier suggestions that on average the aleutian high is intensified during the warm extremes of the southern oscillation even using the 34 years of data now available however the statistical significance of this relationship cannot be demonstrated unequivocally once again the separation of so effects from qbo influences in the limited data a

tropical sst preconditioning of the sh polar vortex during winter 2002 the response of the southern hemisphere sh polar atmosphere to the tropical sea surface temperature sst during the 2002 winter spring season is investigated by using a general circulation model gcm the sh stratospheric winter of 2002 was particularly unusual characterized by a weaker than normal polar vortex during the whole season it also registered at the end of september the first major warming yet observed in the sh this event is unexpected in the sh and it is supposed to be induced by a preconditioning of the polar vortex starting at the beginning of the winter atmospheric gcm experiments with prescribed sst boundary conditions are performed the sensitivity of the antarctic dynamics to the tropical sst of 2002 a year characterized by an el nino event of moderate intensity is studied and the uniqueness of the 2002 tropical oceanic condition is investigated through the comparison of the simulated response of the climatic system to 2002 and 1997 tropical sst 1997 being a year with a strong el nino event model results highlight a primary role played by the tropical sst of 2002 in the development of the peculiar characteristics of the antarctic dynamics during the winter months that appears to be a necessary condition for the generation of the anomalous destabilization of the polar vortex during the following spring results for june 2002 show a strong generation of vertically propagating waves resulting from the tropical sst that through the perturbation of the westerly jet at middle latitudes produces a preconditioning of the polar vortex by affecting the wave refraction index the particular structure of the tropical sst anomalies during the winter of 2002 is thought to have influenced the subsequent preconditioning of the stratospheric vortex

tropospheric precursors of anomalous northern hemisphere stratospheric polar vortices regional extratropical tropospheric variability in the north pacific and eastern europe is well correlated with variability in the northern hemisphere wintertime stratospheric polar vortex in both the ecmwf reanalysis record and in the whole atmosphere community climate model to explain this correlation the link between stratospheric vertical eliassen palm flux variability and tropospheric variability is analyzed simple reasoning shows that variability in the north pacific and eastern europe can deepen or flatten the wintertime tropospheric stationary waves and in particular its wavenumber 1 and 2 components thus providing a physical explanation for the correlation between these regions and vortex weakening these two pathways begin to weaken the upper stratospheric vortex nearly immediately with a peak influence apparent after a lag of some 20 days the influence then appears to propagate downward in time as expected from wave mean flow interaction theory these patterns are influenced by enso and october eurasian snow cover perturbations in the vortex induced by the two regions add linearly these two patterns and the quasi biennial oscillation qbo are linearly related to 40 of polar vortex variability during winter in the reanalysis record

propagation of enso temperature signals into the middle atmosphere a comparison of two general circulation models and era 40 reanalysis data the vertical propagation of the el nino southern oscillation enso temperature signal has been analyzed in two general circulation models the whole atmosphere community climate model and the middle atmosphere european center hamburg model and in the era 40 reanalysis data set monthly mean data have been used and composite differences el nino la nina have been computed our results show that the enso signal propagates into the middle atmosphere by means of planetary rossby waves significant wave like anomalies are observed up to around 40 km this propagation is strongly influenced by the zonal mean zonal winds being most effective in midlatitudes of the northern hemisphere because enso events tend to peak in northern winter when stratospheric winds are westerly in the northern hemisphere and allow vertical propagation of rossby waves in addition zonal mean temperature anomalies are observed in the middle atmosphere in the tropics and at polar latitudes of the northern hemisphere these anomalies are the result of changes in the residual mean meridional circulation our analysis reveals that during an el nino event vertical wave propagation and divergence of eliassen palm flux are enhanced forcing a stronger residual circulation in the stratosphere which cools the tropics and warms the higher latitudes this pattern is highly significant in the models during certain months but much less in the era 40 data where other sources of variability in particular the quasi biennial oscillation also influence the residual circulation

response of the antarctic stratosphere to two types of el nino events this study is the first to identify a robust el nino southern oscillation enso signal in the antarctic stratosphere elninoeventsbetween1979and2009areclassifiedaseitherconventional coldtongue events positive sst anomalies in the nino 3 region or warm pool events positive sst anomalies in the nino 4 region the 40 yr ecmwf re analysis era 40 ncep and modern era retrospective analysis for research and applications merra meteorological reanalyses are used to show that the southern hemisphere stratosphere responds differently to these two types of el nino events consistent with previous studies cold tongue events do not impact temperatures in the antarctic stratosphere during warm pool el nino events the poleward extension and increased strength of the south pacific convergence zone favor an enhancement of planetary wave activity during september november on average these conditions lead to higher polar stratospheric temperatures and a weakening of the antarctic polar jet in november and december as compared with neutral enso years the phase of the quasi biennial oscillation qbo modulates the stratospheric response to warm pool el nino events the strongest planetary wave driving events are coincident with the easterly phase of the qbo

internal variability of the troposphere stratosphere coupled system simulated in a simple global circulation model internal variability of a troposphere stratosphere coupled system is investigated in a series of numerical experiments with a simple global circulation model under a perpetual winter condition in order to examine the relative importance of forced planetary waves in the interaction with the zonal mean zonal flow and baroclinic disturbances amplitude of a sinusoidal surface topography of zonal wavenumber 1 or 2 is swept as an experimental parameter 1000 day integrations are performed for 110 combinations of the external parameters intraseasonal variability of the extratropical winter stratosphere in the parameter sweep experiment of the zonal wavenumber 1 topography is classified into four regimes dependent on the topographic amplitude i a nearly radiative equilibrium state ii small undulations of the polar vortex iii intermittent breakdowns of the polar vortex or occurrence of stratospheric sudden warming events and iv a usually weak and warm state of the polar vortex the behavior of planetary waves in the stratosphere is characterized by linear propagation in regime i and by quasi linear or weakly nonlinear wave mean flow interaction in regime ii in regimes iii and iv on the other hand it is in a highly nonlinear state reflecting the occurrence of sudden warming events and the usually distorted polar vortex respectively the northern hemisphere winter stratosphere corresponds to regime iii in the intraseasonal variations while the southern counterpart is close to regime ii a lag correlation analysis shows that the dynamical linkage between the stratosphere and the troposphere is also dependent on the regimes the vertical linkage is primarily the upward control in regime i planetary waves are generated by nonlinear interaction of baroclinic disturbances in the troposphere and propagate into the stratosphere in regime ii stratospheric variations are largely confined in the stratosphere although planetary waves are generated in the troposphere the linkage in regime iii on the other hand is inevitably two way planetary wave variability has upward influence from the troposphere to the stratosphere as well as the zonal mean zonal wind shows preconditioning in the troposphere before stratospheric sudden warming events downward propagation of signals to the upper troposphere are also seen in the zonal mean temperature in high latitudes it is higher than normal at the final stage of the sequence of sudden warming events the linkage is also two way in regime iv

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

tropospheric stratospheric wave propagation during el nino southern oscillation 1 traditional and 3 d extended eliassen palm ep fluxes for the globe between the 3 and 600 hpa levels are used to calculate el nino southern oscillation enso composites few of the warm minus cold departures of the traditional ep fluxes are significant at the 95 confidence level in contrast the enso composite differences of the longitudinally dependent extended ep flux have broad regions of significance for a wide range of latitudes longitudes and heights during an enso event there are significant vertical fluxes of wave energy across the tropopause over the subtropical pacific in addition there is substantial meridional exchange of wave energy in the upper troposphere and lower stratosphere in this region proceeding northward the changes in the stratosphere are associated with meridional exchanges of wave energy and strong vertical fluxes of wave energy across the pacific and north america the higher latitude changes have a westward tilt with height and eastward group velocities both suggesting the importance of rossby waves in the atlantic region there are strong downward fluxes of wave energy which may be part of an important enso pathway into europe overall these results strongly suggest the importance of nonzonally averaged dynamics in the stratospheric responses to enso

ph changes in peralkaline late magmatic fluids the 1 15 ga old ilimaussaq intrusive complex in south greenland shows an extensive fractionation trend from alkaline augite syenite to various varieties of strongly peralkaline agpaitic nepheline syenites the peralkaline nepheline bearing syenites crystallized between ca 900 and 450 c at 1 kbar and they are cut by late magmatic hydrothermal veins with nepheline absent assemblages of albite aegirine analcime sodalite na be silicates tugtupite chkalovite sorensenite ussingite naalsi3o8 naoh based on fluid inclusions and phase equilibria these veins crystallized between 300 and 500 c at 1 kbar textures indicate that the hydrothermal veins at least partly replaced earlier ilimaussaq rocks the occurrence of ussingite and tugtupite suggests that the late magmatic fluids had strongly basic ph values speciation calculations show that the ph in fluids of the system na al si o h cl mainly depends on the na cl ratio and to a lesser degree on salinity and temperature if the na cl ratio is greater than 1 ph at 400 c and 1 kbar where neutrality is about at ph 5 lies between 7 and 12 because na cl tends to decrease in the final stages of magmatism and during crystallization of the vein assemblage ph of late magmatic fluids generally should become more acidic and only two processes can increase na cl and thus ph dissolution of a cl poor or cl free na silicate or unmixing of an hcl enriched vapour phase field observations and microtextures suggest that replacement reactions are responsible for the change to basic ph at least in some alteration assemblages while replacement of 1 mol nepheline by 1 mol analcime would not alter the ph the volume conserving reaction 1 85 rm ne 2 3 rm h rm 2 rm o 0 19 rm h rm 4 rm sio 4 1 02 rm anl 0 83 rm na 0 83 rm al oh 4 can be used to model the replacement process quantitatively provided it occurred in a more or less closed system progress of this reaction leads to successively increasing ph of the fluid during fluid rock interaction and stabilizes minerals such as ussingite and tugtupite transferring the two processes to a larger scale it is proposed that the extreme hyper agpaitic assemblages at ilimaussaq or at the kola peninsula which include copious amounts of very basic water soluble minerals such as trona villiaumite or thermonatrite are formed either in this way by autometasomatic reactions of late magmatic fluids or melts or supercritical fluid melt mixtures with earlier crystallized rocks of the same plutonic complex or by large scale vapour unmixing in the very final stages of magmatism

tropical variability and stratospheric equatorial waves in the ipslcm5 model the atmospheric variability in the equatorial regions is analysed in the earth system model pre industrial simulation done at ipsl in the framework of cmip5 we find that the model has an interannual variability of about the right amplitude and temporal scale when compared to the el nino southern oscillation enso but that is too confined to the western pacific at the intra seasonal periods the model variability lacks of large scale organisation and only produces one characteristic madden julian oscillation every 10 winters typically at shorter time scales and in the troposphere the model has rossby and kelvin convectively coupled equatorial waves ccews but underestimates the kelvin ccews signal on olr in the model stratosphere a composite analysis shows that the temperature and velocities fluctuations due to the kelvin waves are quite realistic in the model nevertheless the stratospheric waves are less related to the convection than in the observations suggesting that their forcing by the midlatitudes plays a larger role still in the model the kelvin waves are not predominantly occurring during the life cycle of the tropospheric kelvin ccews a behaviour that we find to be dominant in the observations the composite analysis is also used to illustrate how the waves modify the zonal mean flow and to show that the model kelvin waves are too weak in this respect this illustrates how a model can have a reasonable kelvin waves signal on the velocities and temperature but can at the same time underestimate their amplitude to modify the mean flow we also use this very long simulation to establish that in the model the stratospheric equatorial waves are significantly affected by enso hence supporting the idea that the enso can have an influence on the quasi biennial oscillation

southern hemisphere summer mesopause responses to el nino southern oscillation abstractin the southern hemisphere sh polar region satellite observations reveal a significant upper mesosphere cooling and a lower thermosphere warming during warm enso events in december an opposite pattern is observed in the tropical mesopause region the observed upper mesosphere cooling agrees with a climate model simulation analysis of the simulation suggests that enhanced planetary wave pw dissipation in the northern hemisphere nh high latitude stratosphere during el nino strengthens the brewer dobson circulation and cools the equatorial stratosphere this increases the magnitude of the sh stratosphere meridional temperature gradient and thus causes the anomalous stratospheric easterly zonal wind and early breakdown of the sh stratospheric polar vortex the resulting perturbation to gravity wave gw filtering causes anomalous sh mesospheric eastward gw forcing and polar upwelling and cooling in addition constructive inference of enso and quasi biennial oscillation qbo could lead to st

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

influences of enso on stratospheric variability and the descent of stratospheric perturbations into the lower troposphere abstractthe linkage between el nino southern oscillation enso and north atlantic oscillation nao through the stratospheric pathway is examined using a global coupled climate model gfdl climate model version 3 cm3 with increased vertical resolution and extent in the stratosphere as compared to an earlier model gfdl climate model version 2 cm2 it is demonstrated that the relationship between enso and nao is stronger in cm3 than in cm2 it is found that enso plays an important role in modulating the frequency of occurrence of the stratospheric polar vortex anomalies through enhancement attenuation of the amplitudes of zonal wavenumbers 1 and 2 especially in late winter a higher frequency of weak strong stratospheric vortex events is simulated in cm3 during el nino la nina episodes the weak vortex events during el nino winters are preceded by enhancement of the zonal wave 1 pattern and weakening of zonal wave 2 pattern these modified tropospheric planetary waves propagate upward and then w

the 6 5 day wave and its seasonal variability in the middle and upper atmosphere 1 the zonal wave number 1 planetary wave of period near 6 5 days is a robust feature in the mesosphere and lower thermosphere mlt region with prominent seasonal variability as revealed by ground based and satellite observations this wave and its seasonal variability are well reproduced in a recent one model year run of the national center for atmospheric research thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm with its lower boundary specified according to the national centers for environmental prediction analysis year 1993 wavelet analysis of the model output shows that in the mlt region the wave maximizes before and after the equinoxes and minimizes at solstices the wave amplitudes at the equinoxes are smaller than the peaks before and after but are still larger than the wave amplitudes at solstices however at the lower boundary near 30 km the wave peaks are predominantly between fall and the following spring by examining the episodes of maximum and minimum wave amplitude and by conducting additional control experiments using the time gcm the structure of this planetary wave and the factors determining the wave characteristics and seasonal variability are studied in detail it is found that the wave source mean wind structure instability and the critical layers of the wave can all affect the wave response in the mlt region and can have a strong seasonal dependence before and after equinox the wave follows the waveguide and propagates from the stratosphere to the summer mesosphere mesopause where it may amplify due to baroclinic barotropic instability such instability is usually absent from the equinoctial atmosphere so that there is no wave amplification at equinox at solstice the wave decays significantly when propagating away from its winter source due to the strong eastward winter stratospheric jet in the summer side the westward jet is also strong and the meridional and vertical extension of the critical layer of the wave is large enough to enclose the instability in the summer mesosphere mesopause at middle to high latitudes the wave is thus reflected away and prevented from reaching and amplifying at the unstable region the seasonal variation of the quasi two day wave which has zonal phase speed similar to the 6 5 day wave is also studied using similar diagnostics it is further shown that within certain seasonal window periods the variability in the mlt especially the summer mlt may closely track the lower atmospheric variability associated with these waves

asymmetry and nonlinearity of the influence of enso on the northern winter stratosphere 1 observations the el nino southern oscillation enso has significant effects on the extratropical stratosphere this study explores the nonlinearity and the asymmetry of these influences by distinguishing the different effects of four types of enso moderate el nino strong el nino moderate la nina and strong la nina it is revealed that the moderate el nino and the strong la nina are much more efficient than the strong el nino and the moderate la nina respectively in modulating the northern winter stratospheric variability resulting in significant nonlinearity and asymmetry the tropical rainfall anomalies induced by a moderate el nino or a strong la nina are centered over the central equatorial pacific region near the dateline while the convection responses to a strong el nino or a moderate la nina are centered farther eastward accordingly the anomalous pacific north america wave train pattern is modulated by enso in a nonlinear and asymmetric way which leads the large nonlinear and asymmetric components of the vertical eliassen palm e p flux responses to enso the increase of planetary wave activity in the extratropical stratosphere in moderate el nino winters is thus greater than in strong el nino winters whereas a strong la nina gives a larger decrease in propagation than a moderate la nina the relatively strong weak e p flux responses to moderate strong el nino and strong moderate la nina explain the remarkable nonlinearity and asymmetry in the response of the extratropical stratosphere to enso

subsolidus deuteric hydrothermal alteration of eudialyte in lujavrite from the pilansberg alkaline complex south africa abstract the most evolved rocks of the pilansberg alkaline complex are aegirine lujavrites in which three varieties of eudialyte are recognized on the basis of textural relationships and composition manganoan eudialyte i is a relict orthomagmatic phase occurring as poikilitic plates or as relict grains in pseudomorphed euhedral phenocrysts late eudialyte ii ranges in composition from manganoan eudialyte through kentbrooksite to taseqite like varieties and is considered to be formed by cation exchange with eudialyte i and alkaline fluids eudialyte iii is a hydrothermal phase replacing eudialyte ii and has either taseqite like 5 7 3 wt sro

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

ion microprobe study of intragrain micropermeability in alkali feldspars alkali feldspar cleavage fragments from the klokken layered syenite south greenland were heated to 700 c at 0 1 gpa in 99 h218o for 75 h these samples were then polished and imaged by ion microprobe for 18o the feldspars were known to contain areas of pristine braid micro perthite which were not turbid and areas of deuteric patch perthite which were turbid turbidity is related to the presence of micropores in the feldspars on imaging the grain it was found that the 18o had penetrated into the parts of the grain which were microporous and not into the pristine areas micropores are therefore responsible for rendering the feldspars permeable as well as porous the implications of micropermeable feldspars in several areas of geology are discussed

the influence of enso on winter north atlantic climate 1 although the influence of the el nino southern oscillation on the extra tropical climate is well established for the pacific basin and north american regions there is no clear consensus as to whether there are reproducible effects from enso on the north atlantic and west european regions in this study we present a revised analysis of past el nino teleconnections by stratifying el nino events according to amplitude we find a highly non linear yet robust response to enso that changes sign over the eastern north atlantic as the amplitude of the el nino anomaly increases results from a series of experiments with a general circulation model indicate that the response to strong enso events is reproducible given the sea surface temperature anomalies in the tropical pacific the response to moderate el nino events resembles the negative phase of the north atlantic oscillation as found in previous studies

why might stratospheric sudden warmings occur with similar frequency in el nino and la nina winters 1 the effect of el nino southern oscillation enso on the frequency and character of northern hemisphere major mid winter stratospheric sudden warmings ssws is evaluated using a meteorological reanalysis data set and comprehensive chemistry climate models there is an apparent inconsistency between the impact of opposite phases of enso on the seasonal mean vortex and on ssws el nino leads to an anomalously warm and la nina leads to an anomalously cool seasonal mean polar stratospheric state but both phases of enso lead to an increased ssw frequency a resolution to this apparent paradox is here proposed the region in the north pacific most strongly associated with precursors of ssws is not strongly influenced by el nino and la nina teleconnections in the observational record both la nina and el nino lead to similar anomalies in the region associated with precursors of ssws and consistent with this there is a similar ssw frequency in la nina and el nino winters a similar correspondence between the penetration of enso teleconnections into the ssw precursor region and ssw frequency is found in the comprehensive chemistry climate models the inability of some of the models to capture the observed relationship between la nina and ssw frequency appears related to whether the modeled enso teleconnections result in extreme anomalies in the region most closely associated with ssws finally it is confirmed that the seasonal mean polar vortex response to enso is only weakly related to the relative frequency of ssws during el nino and la nina

impact of enso on the atmospheric variability over the north atlantic in late winter role of transient eddies abstractthe dynamical mechanism for the late winter teleconnection between el nino southern oscillation enso and the north atlantic oscillation nao is examined using the output from a 2000 yr integration of a coupled general circulation model gcm the coupled model captures many salient features of the observed behavior of both enso and nao as well as their impact on the surface climate in late winter both the observational and model data indicate more occurrences of negative phase of nao in late winter during el nino events and positive nao in la nina episodes the potential role of high frequency transient eddies in the above teleconnection is diagnosed during el nino winters the intensified transient disturbances along the equatorward shifted north pacific storm track extend their influences farther downstream the eddy induced negative height tendencies are found to be more coherent and stronger over north atlantic than that over north pacific these negative height tendencies over the north

association of tropical pacific sea surface temperatures with the stratospheric holton tan oscillation in the northern hemisphere winter 1 based on 45 years of the european centre for medium range weather forecasting era 40 reanalysis dataset and the noaa extended reconstructed sea surface temperature sst data the associated anomalies in the stratospheric holton tan oscillation hto with the tropical eastern pacific sst in the northern hemisphere winter are investigated it is found that the hto which is induced by equatorial quasi biennial oscillation qbo is significant in the cold sst phase but the hto becomes much weaker in the warm sst phase the conventional qbo modulation on the planetary wave propagation in the stratosphere is only significant when the sst anomaly is cold in the tropical eastern pacific however the modulation tends to be weak when the sst anomaly is warm it is suggested that this difference may arise from the interaction between the tropical eastern pacific sst and the qbo associated planetary wave propagation

using a large ensemble of simulations to assess the northern hemisphere stratospheric dynamical response to tropical volcanic eruptions and its uncertainty the observed strengthening of the northern hemisphere nh polar vortex after tropical volcanic eruptions appears to be underestimated by coupled climate models however there is only a limited number of observed eruptions which makes the attribution of volcanic signals difficult because the polar vortex is also influenced by other external forcing factors as well as internal variability we show with a 100 member ensemble of historical 1850 2005 simulations with the mpi esm lr that an ensemble larger than what is provided by the coupled model intercomparison project phase 5 cmip5 models is needed to detect a statistically significant nh polar vortex strengthening the most robust signal can be found when only the two strongest eruptions krakatau and pinatubo are considered in contrast to including smaller eruptions to increase the sample size for these two strongest eruptions also the mean of 15 cmip5 models shows a statistically significant strengthening of the nh polar vortex

raindrop induced saltation and the enrichment of sediment discharged from sheet and interrill erosion areas sheet and interrill erosion areas are sources of soil material rich in nutrients and pollutants the loss of soil nutrients and other chemicals from these areas is a matter of concern both in terms of maintaining soil productivity and the health of offsite environments many experiments on rainfall erosion have shown enrichment of fine material nutrients and other chemicals in the sediment discharged for sheet and interrill erosion areas but often these results were obtained over short periods of time a qualitative mechanistic model of raindrop induced saltation is used to illustrate how this transport mechanism influences the composition of sediment discharged by rain impacted flow initially fast moving particles are enriched in the sediment discharge but over time during a rainfall event slower moving particles become more represented raindrop induced saltation promotes the storage of material on the soil surface with a coarser composition than the original soil winnowing of material from this storage by the development of flow driven saltation during high intensity events can modify the composition of the sediment discharged later by raindrop induced saltation given stable soil particles the composition of the sediment discharged at the steady state is the same as the original soil enrichment is a non steady state phenomenon and failure to recognize the transient nature of enrichment may lead to inappropriate interpretation of the implications of the results from short term experiments copyright 2011 john wiley sons ltd

implementation of a gravity wave source spectrum parameterization dependent on the properties of convection in the whole atmosphere community climate model waccm 1 this article describes the implementation of a new source spectrum parameterization for convectively generated gravity waves in the whole atmosphere community climate model version 2 waccm2 this parameterization is active in the tropics and is interactive with the underlying convection the gravity wave spectrum at each model grid point and time step is determined based on the convective heating depth tropospheric wind and the convective heating rate this parameterization introduces more realistic spatial and temporal distributions of gravity wave activity and yields gravity wave characteristics related to the underlying wave source we present the estimated gravity wave momentum flux phase speed spectra at 100 hpa as well as the gravity wave drag in the middle and upper atmosphere using the new source spectrum representation we also show the effects of this more physically based parameterization on the structure of the stratospheric and mesospheric semi annual oscillations of the zonal wind compared to a simulation with uniform gravity wave distribution we conclude that the interaction of the gravity wave parameterization with tropospheric characteristics is a positive step toward a more physical representation of the middle and upper atmosphere

effect of el nino southern oscillation on the dynamical thermal and chemical structure of the middle atmosphere 1 a simulation of the middle atmosphere is presented using a general circulation model gcm forced with observed sea surface temperature for the period 1950 2000 the gcm extends to the lower thermosphere and reproduces realistic dynamical and temperature distributions the period contains several el nino and la nina events which are identified using the nino3 index composite anomalies of relevant meteorological fields are obtained by stratifying the northern winter season according to the nino3 index these anomalies have the structure of vertically propagating planetary waves extending from the troposphere to the mesosphere circulation anomalies in the middle atmosphere are accompanied by large temperature anomalies that are of opposite sign in the stratosphere and mesosphere the former being warmer and the latter colder during el nino events near the summer mesopause changes in momentum deposition by parameterized gravity waves results in warming during el nino detailed statistical analysis is used to determine the significance of these anomalies a chemical transport simulation is carried out using output from the gcm it shows that when the lower stratosphere is colder as during la nina events some ozone depletion takes place conversely when the lower stratosphere is warmer and more disturbed as is the case during el nino events heterogeneous chemical processes are inhibited

the effects of the indo pacific warm pool on the stratosphere sea surface temperature sst in the indo pacific warm pool ipwp plays a key role in influencing east asian climate and even affects global scale climate change this study defines ipwp nino and ipwp nina events to represent the warm and cold phases of ipwp sst anomalies respectively and investigates the effects of these events on stratospheric circulation and temperature results from simulations forced by observed sst anomalies during ipwp nino and nina events show that the tropical lower stratosphere tends to cool during ipwp nino events and warm during ipwp nina events the responses of the northern and southern polar vortices to ipwp nino events are fairly symmetric as both vortices are significantly warmed and weakened however the responses of the two polar vortices to ipwp nina events are of opposite sign the northern polar vortex is warmed and weakened but the southern polar vortex is cooled and strengthened these features are further confirmed by composite analysis using reanalysis data a possible dynamical mechanism connecting ipwp sst to the stratosphere is suggested in which ipwp nino and nina events excite teleconnections one similar to the pacific north america pattern in the northern hemisphere and a rossby wave train in the southern hemisphere which project onto the climatological wave in the mid high latitudes intensifying the upward propagation of planetary waves into the stratosphere and in turn affecting the polar vortex

assessment of soil particle erodibility and sediment trapping using check dams in small semi arid catchments check dams can be used as a source of information for studies on sediment characteristics and soil particle erodibility in this study sediment yield and grain size distribution gsd were measured in twenty small catchments draining into a rock check dam in nw iran for different runoffs during 2010 2011 significant correlations were found between sediment yield and slope steepness vegetation cover and soil erodibility factor k of the catchments the erodibility of soil particles was determined using the comparison of gsd between sediment and original soil clay was the most erodible soil particle which showed 2 05 times more percentage in sediment than the original soil the erodibility of soil particles were strongly affected by the rainfall erosivity ei30 check dams showed more effectiveness in trapping coarse particles sand and gravel the effectiveness of check dams in trapping coarse particles enhanced with increase in the remaining capacity of check dams

a new type of silicate liquid immiscibility in peralkaline nepheline syenites lujavrites of the ilimaussaq complex south greenland the 1 15 ga old ilimaussaq intrusive complex in south greenland shows an extensive fractionation trend from alkaline augite syenite to various varieties of strongly peralkaline agpaitic nepheline syenites lujavrites the lujavrites are rocks with highly fluidal textures and are interpreted to have compositions close to melt compositions with the possible exception of significant loss of volatiles they crystallized between 800 and 450 c at 1 kbar and the different textural and mineralogical varieties exhibit variable but extreme enrichment in incompatible elements such as u th nb li be ree zr or rb dykes of one variety of these extreme agpaites exhibit spectacular features of macroscopically visible liquid immiscibility between an fe mn nb ree rich and a na al rich melt the latter forms light greyish pillow like structures of up to some centimetres size comparable to the ocelli known from lamprophyres in a dark fine grained matrix which is one of the most nb and ree rich melts known up to 1 2 wt nb2o5 and up to 6 6 wt reetot 2o3 unmixed between 500 and 600 c at 1 kbar both former melt phases crystallized assemblages involving arfvedsonite k feldspar steenstrupine and a variety of rare trace minerals presumably the na al rich melt additionally crystallized nepheline which was completely converted to analcime in an auto hydration process during cooling thisoccurrence offers the possibility to study the effect of compositional changes in melts and their bearing on immiscibility in great detail because the two immiscible melt phases are macroscopically visible can easily be separated from each other and a large part of the fractionation trend towards the solvus is recorded in the various lujavritic rock types of the ilimaussaq complex

the influence of raindrop induced saltation on particle size distributions in sediment discharged by rain impacted flow on planar surfaces abstract a mechanistic model was used to simulate the downstream movement of particles travelling in suspension by raindrop induced saltation and flow driven saltation on planar surfaces ranging from 2 m to 30 m in length results were produced for two rainfall events one of high intensity the other of moderate intensity and a mixture of particle sizes ranging from fine material to 0 9 mm sand initially the composition of the sediment discharge was controlled by the composition of the soil matrix and the rate the raindrop driven transport systems were capable of transporting the particles from zones near the downstream boundary as time progressed material transported from upslope provided a degree of protection in these zones and controlled the composition of the sediment discharge the protection provided reduced the discharge of fine material but had little effect of the composition of the discharge of the coarser material during a given rainfall event so that it remainder finer than that of the soil matrix however in the long term the slow movement of the coarsest material into the zones controlling sediment discharge led to coarsening of the sediment discharge so that it tended to the composition of the soil matrix at the steady state the time taken to reach that steady state may be considerable and increases with plot length so that many many storms may occur before the steady state condition is reached

dynamical connection between the stratospheric arctic vortex and sea surface temperatures in the north atlantic we used two long term reanalysis datasets and time slice simulations to examine the decadal relationship between the stratospheric arctic vortex sav and sea surface temperature anomalies sstas in the north atlantic and the dynamic mechanisms involved in the linkage between the two our results show that there is a significant decadal linkage between sstas over the north atlantic and the sav where warmed cooled sstas over the north atlantic in association with its principal mode correspond to a weakened strengthened sav the warmed north atlantic sstas tend to result in a weakened sav via two dynamic processes 1 constructive interference at high latitudes with a ridge in the atlantic sector and a trough in the pacific accompanied by a negative north atlantic oscillation like pattern over the north atlantic and a weakened aleutian low over the north pacific and 2 more wavenumber 1 waves propagated into the arctic stratosphere by modifying the baroclinic term of the zonal mean background state and altering the propagating conditions around the tropopause over the arctic results from reanalysis and model simulations both suggest that a strengthening wave intensity in the high latitude troposphere and more upward propagation of the planetary wavenumber 1 wave in response to the warmed north atlantic sstas conjunctly contribute to the increased planetary wave flux in the arctic stratosphere facilitating a weakened sav these results provide a new understanding of what dynamic processes control the sav and will help to predict the stratosphere on decadal timescales