topography and self gravitation interaction in elastic gravitational modeling changes in gravity due to volcanic loading of the crust are influenced by topography we investigate the relative importance of topography and self gravitation in the interpretation of gravity changes it is shown that modeling of gravity changes can be more precise with the introduction of topographic relief although it is neglected self gravitation of the medium this paper exploits this result by suggesting a mathematical simplification that could be useful in the future development of a numerical technique to accurately include topographic effects in the modeling of deformation and gravity changes finally we perform an inversion of the gravity changes observed at mayon volcano philippines between december 1992 and december 1996 including topographic effects by varying the depth of the source failure to account for topographic influences can bias estimates of source parameters particularly when the lateral extension of the relief is of the same order of magnitude as the source depth

storm time evolution of elf vlf waves observed by demeter satellite in this paper using the data of sun synchronous satellite detection of electro magnetic waves transmitted from earthquake regions demeter we investigated the storm time variations of elf vlf waves during the intense coronal mass ejections cme driven storms from 2005 to 2009 the results show that there is a good correlation between the enhancement of elf vlf waves and the cme events immidately following the enhanced wave activity driven by cmes at the initial phase the wave intensity decreases temporarily at the beginning of storm main phase the strongest waves predominantly occur from the late main phase to early recovery phase the elf waves below 3 khz are significantly intensified during the whole storm time while the high frequency waves above 3 khz seem strengthened predominantly during the late main and early recovery phase the elf waves below 3 khz can exist in a wide l shell range with the intensity peaking at l 3 and 4 high frequency waves at f 9 khz exist mostly outside the plasmapause the stronger elf vlf waves on the dayside can last longer time than those on the nightside

western pacific interannual variability associated with the el nino southern oscillation observations of sea surface temperature sst sea level pressure slp surface wind and outgoing longwave radiation olr show that the el nino southern oscillation enso displays western pacific anomaly patterns in addition to eastern pacific anomaly patterns during the warm phase of enso warm sst and low slp anomalies in the equatorial eastern pacific and low olr anomalies in the equatorial central pacific are accompanied by cold sst and high slp anomalies in the off equatorial western pacific and high olr anomalies in the off equatorial far western pacific also while the zonal wind anomalies over the equatorial central pacific are westerly those over the equatorial far western pacific are easterly the nearly out of phase behavior between the eastern and western tropical pacific is also observed during the cold phase of enso but with anomalies of opposite sign these western pacific interannual anomaly patterns are robust features of enso independent of data sets it is argued that equatorial easterly westerly wind anomalies over the far western pacific during the warm cold phase of enso are initiated by off equatorial western pacific cold warm sst anomalies and that these winds are important for the evolution of enso an atmosphere model is employed to demonstrate that small off equatorial western pacific cold warm sst anomalies compared to those in the east are sufficient to produce equatorial easterly westerly wind anomalies as observed over the far western pacific the coupled ocean atmosphere model of zebiak and cane is then modified to investigate the evolution of the western pacific interannual anomaly patterns in a coupled ocean atmosphere system by including a meridional structure to the subsurface temperature parameterization in the western pacific the modified model produces both western and eastern pacific interannual anomaly patterns

gravity changes and deformation due to a magmatic intrusion in a two layered crustal model we develop and extend theoretical and computational methods for the calculation of the deformation gravity and potential change due to a point source of magma injection into a multilayered elastic gravitational earth model in our calculations which are based upon the method outlined by rundle two distinct layers overlying a half space may be incorporated the source can be located in either of the layers or the half space the method is quite general and can be readily adapted to calculations in which stresses in either the layers or the half space relax by viscoelastic flow the results obtained indicate that the use of homogeneous half space to represent the earth may in some cases be too simple a model and that variations in elastic moduli have a more significant effect than variation in reference density on both the surface displacements and gravity changes as an example we calculate the displacement and gravity changes due to a subsurface mass injection in a crust mantle model appropriate to the volcanic island of lanzarote which is presently the subject of numerous geophysical experiments both historical and recent data indicate that lanzarote may be subject to some risk of volcanic eruption in the future thus our calculations may be useful in interpreting observations of preemption phenomena the results are discussed in terms of prediction versus measurement capabilities

new results at mayon philippines from a joint inversion of gravity and deformation measurements in this paper we detail the combination of the genetic algorithm ga inversion technique with the elastic gravitational model originally developed by rundle and subsequently refined by fernandez and others a sensitivity analysis is performed for the joint inversion of deformation and gravity to each of the model parameters illustrating the importance of proper identification of both the strengths and limitations of any source model inversion and this technique in particular there is a practical comparison of the theoretical results with the inversion of geodetic data observed at the mayon volcano in the philippines where there are gravity changes without significant deformation after the 1993 eruption

statistical storm time examination of mlt dependent plasmapause location derived from image euv the location of the outer edge of the plasmasphere the plasmapause as a function of geomagnetic storm time is identified and investigated statistically in regard to the solar wind driver imager for magnetopause to aurora global exploration image extreme ultraviolet euv data are used to create an automated method that locates and extracts the plasmapause the plasmapause extraction technique searches a set range of possible plasmasphere densities for a maximum gradient the magnetic local time mlt dependent plasmapause results are compared to manual extraction results the plasmapause results from 39 intense storms are examined along a normalized epoch storm timeline to determine the average plasmapause l shell as a function of mlt and storm time the average extracted plasmapause l shell follows the expected storm time plasmapause behavior the results show that during the main phase the plasmapause moves earthward and a plasmaspheric drainage plume forms near dusk and across the dayside during strong convection during the recovery phase the plume rejoins the corotationally driven plasma while the average plasmapause location moves farther from the earth the results are also examined in terms of the solar wind driver we find evidence that shows that the different categories of solar wind drivers result in different plasmaspheric configurations during magnetic cloud driven events the plasmaspheric drainage plume appears at the start of the main phase during sheath driven events the plume forms later but typically extends further in mlt

role of indian ocean warming in the development of philippine sea anticyclone during enso 1 the anomalous low level anticyclone near the philippines and suppressed convection over the western pacific associated with the mature warm phase of el nino southern oscillation enso have been suggested as important elements in the interaction between enso and the east asian monsoon we examined the causes of these anomalies in the circulation and convection using a newly developed linear baroclinic model that includes interactive moist processes of the cumulus convection and surface heat fluxes a conventional version of the linear model forced by prescribed heating indicates that the diabatic cooling due to suppressed convection over the maritime continent generates the philippine sea anticyclone from a series of the moist linear model experiments we found that the modest warming of the indian ocean in addition to the strong warming in the central eastern pacific and weak cooling in the western pacific is significant to suppress the convection over the maritime continent observed data also show a coincidence of the development between the philippine sea anticyclone indian ocean warming and the ascending motion over the indian ocean supporting the model results the above results indicate that the atmosphere ocean system in the indian ocean may be one of important factors to improve predictability of the east asian climate during enso

sea surface temperature in the north tropical atlantic as a trigger for el nino southern oscillation events the el nino southern oscillation in the pacific ocean influences temperature in other tropical ocean basins reanalysis data and model simulations suggest that temperature anomalies in the north tropical atlantic may also influence the development of la nina events

two types of strong northeast asian summer monsoon the characteristics of a strong northeast asian summer monsoon neasm with and without a and b type respectively a basinwide warming in the indian ocean during the preceding winter are examined for the period of 1979 2006 in the case of the a type strong el nino like sea surface temperature sst decays very rapidly from the preceding winter december february to the following summer june august which may be due to a feedback process of the warm indian ocean in addition the a type strong neasm is more associated with a weak western north pacific summer monsoon than the b type strong neasm on the other hand for the b type an el nino like sst during the preceding winter is a persistent influence into the following summer a striking difference can be found in the atmospheric teleconnection pattern from the tropics to the midlatitudes over the indo pacific region that is the pacific japan like pattern versus a pronounced rossby wave train pattern this may result from the difference in location of the maximum center of rainfall anomalies over the tropical northwestern pacific between the two types of strong neasm the authors argue that indian ocean basin warming plays a role in modifying the convective system over the subtropical western pacific resulting in changes in atmospheric teleconnections between the two types of strong neasm the weak neasm in which the anomalous rainfall pattern resembles that of the a type strong neasm except for the sign is also discussed

on the atlantic pacific ninos connection a multidecadal modulated mode atlantic and pacific el nino are the leading tropical oceanic variability phenomena at interannual timescales recent studies have demonstrated how the atlantic nino is able to influence on the dynamical processes triggering the development of the pacific la nina and vice versa however the stationarity of this interbasin connection is still controversial here we show for the first time that the atlantic pacific ninos connection takes place at particular decades coinciding with negative phases of the atlantic multidecadal oscillation amo during these decades the atlantic pacific connection appears as the leading coupled covariability mode between tropical atlantic and pacific interannual variability the mode is defined by a predictor field the summer atlantic sea surface temperature sst and a set of predictand fields which represent a chain of atmospheric and oceanic mechanisms to generate the pacific el nino phenomenon alteration of the walker circulation surface winds in western pacific oceanic kelvin wave propagating eastward and impacting on the eastern thermocline and changes in the pacific sst by internal bjerknes feedback we suggest that the multidecadal component of the atlantic acts as a switch for el nino prediction during certain decades putting forward the amo as the modulator acting through changes in the equatorial atlantic convection and the equatorial pacific sst variability these results could have a major relevance for the decadal prediction systems

some insights into topographic elastic and self gravitation interaction in modelling ground deformation and gravity changes in active volcanic areas surface displacements and gravity changes due to volcanic sources are influenced by medium properties we investigate topographic elastic and self gravitation interaction in order to outline the major factors that are significant in data modelling while elastic gravitational models can provide a suitable approximation to problems of volcanic loading in areas where topographic relief is negligible for prominent volcanoes the rough topography could affect deformation and gravity changes to a greater extent than self gravitation this fact requires the selection depending on local relief of a suitable model for use in the interpretation of surface precursors of volcanic activity we use the three dimensional indirect boundary element method to examine the effects of topography on deformation and gravity changes in models of magma chamber inflation deflation topography has a significant effect on predicted surface deformation and gravity changes both the magnitude and pattern of the geodetic signals are significantly different compared to half space solutions thus failure to account for topographic effects in areas of prominent relief can bias the estimate of volcanic source parameters since the magnitude and pattern of deformation and gravity changes depend on such effects

modulation of the meridional structures of the indo pacific warm pool on the response of the hadley circulation to tropical sst abstractby decomposing the variations of the hadley circulation hc and tropical zonal mean sea surface temperature sst into the equatorially asymmetric hea for hc sea for sst and symmetric

roles of tropical sst anomalies in modulating the western north pacific anomalous cyclone during strong la nina decaying years this study re explores the roles of tropical sst anomalies in modulating the anomalous cyclone over the indo western pacific during strong la nina decaying years via a series of numerical experiments the results suggest that central to eastern equatorial pacific cooling western north pacific wnp warming and indian ocean cooling all contribute to the indo western pacific cyclonic wind anomalies the wnp sst anomalies play a role via a rossby wave type response as the positive sst anomalies in the wnp decay the local forcing effect decays as well the indian ocean remote forcing seems to play an important role during boreal summer via cold kelvin wave induced cyclonic shear and boundary layer convergence during strong la nina decaying years the negative sst anomalies in the equatorial central to eastern pacific can maintain and persist into summer such cooling could induce anomalous walker circulation with ascending branch over the maritime continent to philippines and descending branch over central to eastern pacific which links the wnp climate to the equatorial central and eastern pacific sst anomalies the convective heating over the wnp induced remotely by central to eastern pacific cooling in turn forces atmospheric rossby wave to its west which may amplify the anomalous cyclone over the indo western pacific

interannual variability in a tropical atmosphere ocean model influence of the basic state ocean geometry and nonlinearity abstract the behavior of a tropical coupled atmosphere ocean model is analyzed for a range of different background states and ocean geometries the model is essentially that of cane and zebiak for the tropical pacific except only temporally constant background states are considered here for realistic background states and ocean geometry the model solutions feature oscillations of period of 3 5 yr by comparing the full model solution with a linearized version of the model it is shown that the basic mechanism of the oscillation is contained within linear theory a simple linear analog model is derived that describes the nature of the interannual variability in the coupled tropical atmosphere ocean system the analog model highlights the properties that produce coupled atmosphere ocean instability in the eastern ocean basin and the equatorial wave dynamics in the western ocean basin that are responsible for a delayed negative feedback into this instability growth the growth rate of the local instabil

indian ocean capacitor effect on indo western pacific climate during the summer following el nino significant climate anomalies persist through the summer june august after el nino dissipates in spring over the equatorial pacific they include the tropical indian ocean tio sea surface temperature sst warming increased tropical tropospheric temperature an anomalous anticyclone over the subtropical northwest pacific and increased mei yu baiu rainfall over east asia the cause of these lingering el nino effects during summer is investigated using observations and an atmospheric general circulation model gcm the results herein indicate that the tio warming acts like a capacitor anchoring atmospheric anomalies over the indo western pacific oceans it causes tropospheric temperature to increase by a moist adiabatic adjustment in deep convection emanating a baroclinic kelvin wave into the pacific in the northwest pacific this equatorial kelvin wave induces northeasterly surface wind anomalies and the resultant divergence in the subtropics triggers suppressed convection and the anomalous anticyclone the gcm results support this kelvin wave induced ekman divergence mechanism in response to a prescribed sst increase over the tio the model simulates the kelvin wave with low pressure on the equator as well as suppressed convection and the anomalous anticyclone over the subtropical northwest pacific an additional experiment further indicates that the north indian ocean warming is most important for the kelvin wave and northwest pacific anticyclone a result corroborated by observations these results have important implications for the predictability of indo western pacific summer climate the spatial distribution and magnitude of the tio warming rather than simply whether there is an el nino in the preceding winter affect summer climate anomalies over the indo western pacific and east asia

erosion and refilling of the plasmasphere during a geomagnetic storm modeled by a neural network we present a history dependent model of the equatorial plasma density of the inner magnetosphere using a feedforward neural network with two hidden layers as the model inputs we take locations and time series of sym h al and f10 7 indices by considering not only the instantaneous values but also the past values of geomagnetic and solar indices the model is history dependent on levels of geomagnetic and solar activity the modeled electron density is continuous both spatially and temporally so that the evolution of the density can be studied such as plasmaspheric refilling the model is trained using the electron density inferred from the spacecraft potential from three themis probes the equatorial electron density is shown to be accurately reconstructed with a correlation coefficient of r 0 953 between data and model target since the model is history dependent it succeeds in reconstructing various density features and dynamic behaviors such as the quiet time plasmasphere erosion and recovery of the plasmasphere as well as the plume formation during a storm on 4 february 2011 our model may provide unprecedented insight into the behavior of the equatorial density at any time and location as an example we show the inferred refilling rate from our model and compare it to previous estimates

the effects of topography on magma chamber deformation models application to mt etna and radar interferometry we have used a three dimensional elastic finite element model to examine the effects of topography on the surface deformation predicted by models of magma chamber deflation we used the topography of mt etna to control the geometry of our model and compared the finite element results to those predicted by an analytical solution for a pressurized sphere in an elastic half space topography has a significant effect on the predicted surface deformation for both displacement profiles and synthetic interferograms not only are the predicted displacement magnitudes significantly different but also the map view patterns of displacement it is possible to match the predicted displacement magnitudes fairly well by adjusting the elevation of a reference surface however the horizontal pattern of deformation is still significantly different thus inversions based on constant elevation reference surfaces may not properly estimate the horizontal position of a magma chamber we have investigated an approach where the elevation of the reference surface varies for each computation point corresponding to topography for vertical displacements and tilts this method provides a good fit to the finite element results and thus may form the basis for an inversion scheme for radial displacements a constant reference elevation provides a better fit to the numerical results

role of the enso indian ocean coupling on enso variability in a coupled gcm warming are only confined to the io and it has little impact on the tropical pacific during the boreal winter when the el nino is in its mature phase the anomalous warming extends eastward to cover the entire tropical io and the anomalous easterlies extend into the western pacific wp the anom alous easterlies in the wp generate oceanic upwelling kelvin waves which propagate eastward and accelerate the decay of the warm sst in the eastern pacific as a result the el nino is rapidly terminated and a la nina develops within one year from the el nino mature phase they concluded that the interaction between enso and the io may generate a biennial tendency for enso 4 the samples used for the composite analysis by kk06 are rather limited due to the relatively short length of the observational data in this study we intended to analyze a longer 200 yr data set obtained from the simulation of a sintex f scale interaction experiment frcgc cou pled gcm in order to verify the enso io feedback hypoth esis itturnsoutthatthefeedbackprocessbetweenensoand the io is quite plausible not only from observations but also from the state of the art coupled gcm

a moist linear baroclinic model coupled dynamical convective response to el nino a newly developed linear baroclinic model lbm and its application to the tropical enso teleconnection is described the model based on primitive equations linearized about the observed zonally varying basic state in northern winter involves linear schemes for the cumulus convection and surface sensible and latent heat fluxes referred to as the moist lbm this enables us to solve a steady state response of the coupled dynamical convective system to a given sst anomaly which is fairly different from the conventional dry lbm linear representation of the convection is acceptable for a realistic range of sst anomalies reproducing well the rossby wave train computed in the conventional lbm forced by a tropical heating the moist lbm is used to examine the formation mechanisms of an anomalous low level anticyclone near

axi symmetric deformation of a thermo poro elastic half space inflation of a magma chamber summary the deformation observed at phlegraean fields italy during the recent 1982 1984 crisis is interpreted in terms of overpressure in a shallow magma chamber and migration of hot pressurized fluids elastic effects are studied first and previous results obtained from maruyama s strain nuclei are corrected poro elastic and thermo elastic effects are found to be as important as the elastic ones in a semi pervious medium the three terms are typically of the same magnitude results are applied to interpreting the bradyseismic crisis of 1982 84 at phlegraean fields pf near naples italy the concave shape of the first phase of the deformation history at pf can be reproduced by linearly increasing fluid pressure and or temperature at the boundary of a spherical cavity the convex shape of the second phase is interpreted in terms of a gradual return to normal conditions the late phase of slow subsidence is interpreted as the effect of diffusional dissipation of temperature and pressure excess the deconvolution of the real source time history at pf is largely non unique but in any case the importance of fluids in the deformation history is assessed furthermore the inclusion of fluid migration in the deformation model allows simple explanations of several geochemical and geophysical observations made during the bradyseismic crisis

interactive feedback between enso and the indian ocean abstract a feedback process of the indian ocean sst on enso is investigated by using observed data and atmospheric gcm it is suggested that warming in the indian ocean produces an easterly wind stress anomaly over indonesia and the western edge of the pacific during the mature phase of el nino the anomalous easterly wind in the western pacific during el nino helps a rapid termination of el nino and a fast transition to la nina by generating upwelling kelvin waves thus warming in the indian ocean which is a part of the el nino signal operates as a negative feedback mechanism to enso this indian ocean feedback appears to operate mostly for relatively strong el ninos and results in a la nina one year after the mature phase of the el nino this 1 yr period of phase transition implies a possible role of indian ocean enso coupling in the biennial tendency of the enso atmospheric gcm experiments show that indian ocean sst forcing is mostly responsible for the easterly wind anomalies in the western pacific

gravity changes and internal processes some results obtained from observations at three volcanoes temporal gravity changes provide information about mass and or density variations within and below the volcano edifice three active volcanoes have been under investigation each of them related to a plate boundary mayon luzon philippines merapi java indonesia and galeras colombia the observed gravity changes are smaller than previously expected but significant for the three volcanoes under investigation and within the observation period mainly the increase of gravity is observed ranging from 1 000 nm 2 to 1 600 nms 2 unexpectedly the gravity increase is confined to a rather small area with radii of 5 to 8 km around the summit at mayon and merapi the parallel gps measurements yield no significant elevation changes this is crucial for the interpretation as the internal pressure variations do not lead to significant deformation at the surface thus the classical mogi model for a shallow extending magma reservoir cannot apply to confine the possible models the attraction due to changes of groundwater level or soil moisture is estimated along the slope of merapi exemplarily by 2 d modelling mass redistribution or density changes were evaluated within the vent as well as deeper fluid processes to explain the gravity variations the results are compared to the model incorporating the additional effect of elastic deformation

spherical and ellipsoidal volcanic sources at long valley caldera california using a genetic algorithm inversion technique abstract we model the second inflation period at long valley caldera california using a genetic algorithm technique and high quality geodetic measurements of elevation changes and baseline extensions we compare two source inversions for both spherical mogi point sources and the finite prolate ellipsoid of yang and davis a sensitivity analysis for the genetic algorithm is performed based upon synthetic data set inversions on similar sources in order to better constrain the areal location orientation and volume of the potential sources the spherical sources are well constrained the larger located at 9 9 km beneath the resurgent dome with a volume of 0 036 km 3 while the second at only 0 008 km 3 is located at a depth of 7 3 km beneath the south moat the depths to the ellipsoidal sources are switched with the larger source at a depth of 9 6 km and the smaller at 11 8 km with volumes of 0 037 and 0 002 km 3 respectively

interannual and interdecadal variations of the east asian summer monsoon and tropical pacific ssts part i roles of the subtropical ridge the interannual relationship between the east asian summer monsoon and the tropical pacific ssts is studied using rainfall data in the yangtze river valley and the ncep reanalysis for 1951 96 the datasets are also partitioned into two periods 1951 77 and 1978 96 to study the interdecadal variations of this relationship a wet summer monsoon is preceded by a warm equatorial eastern pacific in the previous winter and followed by a cold equatorial eastern pacific in the following fall this relationship involves primarily the rainfall during the pre mei yu mei yu season may june but not the post mei yu season july august in a wet monsoon year the western north pacific subtropical ridge is stronger as a result of positive feedback that involves the anomalous hadley and walker circulations an atmospheric rossby wave response to the western pacific complementary cooling and the evaporation wind feedback this ridge extends farther to the west from the previous winter to the following fall resulting in an 850 hpa anomalous anticyclone near the southeast coast of china this anticyclone 1 blocks the pre mei yu and mei yu fronts from moving southward thereby extending the time that the fronts produce stationary rainfall 2 enhances the pressure gradient to its northwest resulting in a more intense front and 3 induces anomalous warming of the south china sea surface through increased downwelling which leads to a higher moisture supply to the rain area a positive feedback from the strong monsoon rainfall also appears to occur leading to an intensified anomalous anticyclone near the monsoon region this sst subtropical ridge monsoon rainfall relationship is observed in both the interannual timescale within each interdecadal period and in the interdecadal scale the sst anomalies sstas change sign in northern spring and resemble a tropospheric biennial oscillation tbo pattern during the first interdecadal period 1951 77 in the second interdecadal period 1978 96 the sign change occurs in northern fall and the tbo pattern in the equatorial eastern pacific sst is replaced by longer timescales this interdecadal variation of the monsoon sst relationship results from the interdecadal change of the background state of the coupled ocean atmosphere system this difference gives rise to the different degrees of importance of the feedback from the anomalous circulations near the monsoon region to the equatorial eastern pacific in a wet monsoon year the anomalous easterly winds south of the monsoon enhanced anomalous anticyclone start to propagate slowly eastward toward the eastern pacific in may and june apparently as a result of an atmosphere ocean coupled wave motion these anomalous easterlies carry with them a cooling effect on the ocean surface in 1951 77 this effect is insignificant as the equatorial eastern pacific sstas already change from warm to cold in northern spring probably as a result of negative feedback processes discussed in enso mechanisms in 1978 96 the equatorial eastern pacific has a warmer mean sst a stronger positive feedback between ssta and the walker circulation during a warm phase tends to keep the ssta warm until northern fall when the eastward propagating anomalous easterly winds reach the eastern pacific and reverse the ssta

on the relative importance of self gravitation and elasticity in modeling volcanic ground deformation and gravity changes 1 elastic half space models widely used to interpret displacements and gravity data in active volcanic areas usually compute the displacement response to dilatational sources that simulate a change in pressure of the magma chamber elastic gravitational models allow the computation of gravity deformation and gravitational potential changes due to pressurized magma cavities and intruding masses together this type of model takes into account the mass interaction with the self gravitation of the earth through coupling between model equations we perform a dimensional analysis of the elastic gravitational model estimating the magnitude of intrusion mass and coupling effects at the space scale associated with volcano monitoring we show that the intrusion mass cannot be neglected in the interpretation of gravity changes while displacements are primarily caused by pressurization therefore the intrusion of mass together with the associated pressurization of the magma chamber produces distinctive changes in gravity that could be used to interpret gravity changes without ground deformation and vice versa depending on what type of source plays the main role in the intrusion process theoretical experiments indicate that mass and self gravitation could produce changes in the magnitude and pattern of predicted gravity that may be above microgravity accuracy application of the elastic gravitational model to interpret geodetic precursors observed at mayon volcano philippines prior to the eruption of 2001 shows that inversions increase in precision by using this model therefore our elastic gravitational model is a refinement of purely elastic models and can better interpret gravity and deformation changes in active volcanic zones

deformation gravity and potential changes due to volcanic loading of the crust a method for calculating deformation gravity and potential changes induced by volcanic loads imposed within and on the earth s crust is presented the method involves application of techniques developed for earthquake loading problems in elastic gravitational earth models by considering the elastic gravitational equilibrium of the layered system the gravitational and displacement response due to intruding masses and to pressurized magma chambers can be computed for applications involving seamount loading variations in the height of sea level can be calculated by requiring that seawater lie along an equipotential in continental loading problems the change in potential can be used to calculate the orthometric height cahnge as distinct from the geometric height change for some plausible loading geometries the difference between these two qunatities can be significant results for various loads and earth structures are shown and discussed in particular a magmatic mass intruding into an elastic gravitational lithosphere overlying a compressible gravitating asthenosphere produces distinct gravity anomalies which depend on the depth of intrusion applications of this result can be made to problems of isostatic compensation the intrusion of a magmatic mass together with the associated pressurization of the magma chamber produces distinctive surface gravity and deformation in the near field gravity gradients more defined as surface gravity divided by uplift vary with distance from the source moreover orthometric elevations can be significantly 25 less than geometric elevations these results have clear application to data from events such as the posteruption deflation of kilauea volcano less

gravity changes as a precursor to volcanic eruption at poas volcano costa rica monitoring of gravity changes at active volcanoes has considerable potential for understanding magma chamber dynamics and for detecting eruptive precursors the technique essentially aims to identify changes in sub surface mass or density corresponding to departures from the free air gradient fag or bouguer corrected terrain corrected fag bcfag respectively1 2 such gravity changes of the order of 10 100 gal have been reported previously through eruptive periods3 6 here we present a ten year data set measured at poas volcano costa rica in which gravity increases in 1987 1989 relative to both the fag and the bcfag preceded the ash cloud eruptions of april may 1989 these results constitute the first unambiguous detection of gravity changes as a precursor to eruption and we interpret them in terms of the intrusion of an ascending relatively dense magma body

inflation or deflation new results for mayon volcano applying elastic gravitational modeling volcanic activity produces deformation and gravity changes that many times can be used as precursors of future eruptions applying geodetic techniques to monitoring activity involves interpretation using deformation models usually the observed changes of the deformation and gravity fields are interpreted seperately not in a joint inversion it can be difficult if not impossible to interpret the data coherently or correctly in terms of the characteristics of the intrusion or the deflation derived from the gravity changes with purely elastic models as in the case of mayon volcano phillipines we show that elastic gravitational models can be used to interpret these cases simultaneously leading to a result that is more plausible on the basis of the available information thus we may need to change the philosophy normally used to interpret geodetic observations interpretation as proposed in this work can significantly improve the possibility of predicting future eruptions

an accurate and efficient method for including the effects of topography in three dimensional elastic models of ground deformation with applications to radar interferometry topography has a large effect on the results predicted by elastic surface deformation models in regions of significant relief in some cases topography may have more influence on the predicted deformation field than do model source parameters we have developed an approximate analytical technique for including topographic effects that retains most of the computational simplicity of elastic half space models while providing an accurate representation of topographic effects we use a series expansion of the elastic half space solution with a small slope approximation yielding a set of higher order corrections the integrated effect of these corrections is evaluated using fourier methods we investigate the effectiveness of our method by comparing predicted results for a tilted triaxial ellipsoid with those predicted by finite element models the resulting displacements and displacement gradients are in good agreement with finite element results both for relatively smooth topography synthetically generated and for the greater relief in the vicinity of mount etna volcano we then compare the results of our method with those predicted by traditional elastic half space models using different reference elevations and with a previously proposed method of estimating topographic effects our new method provides a significantly better fit to the finite element results than do the other methods our method is able to accurately portray both the number and the horizontal pattern of fringes in a synthetic interferogram when compared with finite element results in particular the method accurately represents the broadening of fringes that is observed in regions of high relief as well as reproducing the location of the fringe center and the topographically induced deviation of the fringes from a regular pattern elastic half space models typically show a fringe center that is displaced with respect to the finite element results indicating that parameter inversions based on such a model would provide incorrect estimates of the horizontal source position the lack of topographically generated fringe distortions in elastic half space results would also likely lead to inaccuracies in the predicted magnitude and orientation of proposed deformation sources our new technique over comes these limitations and should be useful when evaluating either traditional geodetic results or the greater areal coverage provided by interferometric observations

impacts of indo pacific sea surface temperature anomalies on the summer monsoon circulation and heavy precipitation over northwest india pakistan region during 2010 abstractquite a few studies have documented the evolution of monsoon synoptic systems and midlatitude atmospheric blocking associated with the recent heavy precipitation and floods over northwest pakistan during 2010 this period also witnessed a very unusual indo pacific sea surface temperature sst evolution with a strong la nina event in the pacific substantial indian ocean warming and a negative indian ocean dipole event together with significant enhancement of precipitation over both the equatorial western pacific ocean and the eastern indian ocean here the authors perform a suite of high resolution atmospheric general circulation model experiments to investigate the influence of indo pacific sst anomalies on the south asian monsoon circulation and heavy precipitation over pakistan and adjoining northwest india during 2010 the realistic simulation of these rainfall anomalies using observed ssts motivated the authors to explore the specific influence of indian ocean and pacific sst anomalies thr

interactive feedback between enso and the indian ocean in an interactive ensemble coupled model an interactive feedback between enso and the indian ocean is investigated using a center for ocean land atmosphere studies cola interactive ensemble coupled model from a long term simulation of the coupled gcm it is shown that el nino events terminate relatively rapidly when the indian ocean sst is anomalously warm the anomalous indian ocean warming induces the anomalous easterlies over the western pacific by modulating the walker circulation in turn the anomalous easterlies generate oceanicupwelling kelvin waves over the western pacific which propagate eastward and accelerate the decay of the warm sst in the eastern pacific as a result el nino terminates relatively quickly and the phase transition from el nino to la nina progresses rapidly these interactive processes are consistent with those derived from the previous observational analyses

dynamic plasmapause model based on themis measurements this paper presents a dynamic plasmapause location model established based on 5 years of time history of events and macroscale interactions during substorms themis measurements from 2009 to 2013 in total 5878 plasmapause crossing events are identified sufficiently covering all 24 magnetic local time mlt sectors based on this plasmapause crossing database we investigate the correlations between plasmapause locations with solar wind parameters and geomagnetic indices input parameters for the best fits are obtained for different mlt sectors and finally we choose five input parameters to build a plasmapause location model including 5 min averaged sym h al and au indices as well as hourly averaged ae and kp indices two out of sample comparisons on the evolution of the plasmapause is shown during two magnetic storms demonstrating good agreement between model results and observations two major advantages are achieved by this model first this model provides plasmapause locations at 24 mlt sectors still providing good consistency with observations second this model is able to reproduce dynamic variations of the plasmapause on timescales as short as 5 min

monthly mean island surface winds in the central tropical pacific and el nino events abstract the monthly mean surface wind changes during recent enso events as observed from 11 islands in the tropical pacific are described two different composite enso wind fields are evaluated and compared the month to month wind changes during each event are also discussed the wind changes for each event between 1953 and 1980 except 1969 show several common features i westerly anomalies appear first west of the date line and then at the date line sometime in summer 0 to fall 0 then intensify over the following several months the anomalies are confined to within 3 of the equator during this stage ii in either november 0 december 0 or january 1 there is an abrupt southward shift of the narrow band of westerly anomalies so that the maximum anomaly is then at 5 s latitude at the date line and nearly normal conditions prevail north of the equator iii westerly anomalies are gone or greatly reduced one to two months after the southward shift the event to event variations are

a new solar wind driven global dynamic plasmapause model 1 database and statistics a large database possibly the largest plasmapause location database with 49119 plasmapause crossing events from the in situ observations and 3957 plasmapause profiles corresponding to 48899 plasmapause locations in 1 h mlt intervals from optical remote sensing from 1977 to 2015 by 18 satellites is compiled the responses of the global plasmapause to solar wind and geomagnetic changes and the diurnal seasonal solar cycle variations of the plasmapause are investigated based on this database it is found that the plasmapause shrinks towards the earth globally and a clear bulge appears in the afternoon to pre midnight mlt sector as the solar wind or geomagnetic conditions change from quiet to disturbed the bulge is clearer during storm times or southward imf the diurnal variations of the plasmapause are most probably be result of the difference between the magnetic dipole tilt and the earth s spin axis the seasonal variations of the plasmapause are characterized by equinox valleys and solstice peaks it is also found that the plasmapause approaches the earth during high solar activity and expands outward during low solar activity this database will help us study and understand the evolution properties of the plasmapause shape and the interaction processes of the plasmasphere the ring current and the radiation belts in the magnetosphere

tropical pacific basin wide adjustment and oceanic waves this study examines the basin wide adjustment process associated with el nino southern oscillation enso in terms of oceanic waves using the cane zebiak model the rossby waves induce not only the meridional mass divergence in the ocean interior but also the incoming zonal mass flux at the western boundary which generally overcompensates the interior meridional divergence therefore the rossby waves alone cannot make a negative feedback however the outgoing zonal mass flux associated with the reflected kelvin wave at the western boundary reduces the incoming boundary mass flux associated with the rossby waves resulting in the tendency of equatorial basin wide heat content varying in phase with the meridional divergence also shown is that the nonequilibrium adjustment of the tropical pacific ocean is mainly due to the free kelvin waves reflected at the western boundary

effects of topography on the interpretation of the deformation field of prominent volcanoes application to etna we have investigated the effects of topography on the surface deformation field of volcanoes our study provides limits to the use of classical half space models considering axisymmetrical volcanoes we show that interpreting ground surface displacements with half space models can lead to erroneous estimations of the shape of the deformation source when the average slope of the flanks of a volcano exceeds 20 tilting in the summit area is reversed to that expected for a flat surface thus neglecting topography may lead to misinterpreting an inflation of the source as a deflation comparisons of mogi s model with a three dimensional model shows that ignoring topography may lead to an overestimate of the source volume change by as much as 50 for a slope of 30 this comparison also shows that the depths calculated by using mogi s solution for prominent volcanoes should be considered as depths from the summit of the edifices finally we illustrate these topographic effects by analyzing the deformation field measured by radar interferometry at mount etna during its 1991 1993 eruption a three dimensional modeling calculation shows that the flattening of the deflation field near the volcano s summit is probably a topographic effect

investigating the role of the tibetan plateau in enso variability abstractthe role of the tibetan plateau tp in el nino southern oscillation enso variability is investigated using coupled model experiments with different topography setups removing the tp res

dynamic inversion of ground deformation data for modelling volcanic sources etna 1991 93 the 1991 93 etna eruption that represented the most important recent eruptive event both in terms of duration 472 days and total volume of erupted lava ca 250 106 m caused marked ground deformation measured by using different geodetic techniques such as edm gps levelling and tiltmetry an inversion termed dynamic because it took into account the sequence of events considering both the separate and cumulative effects of two sources a shallow tensile crack and a deeper ellipsoidal deflating source was performed it was based on 163 data collected by the different techniques plus 2 geometrical conditions for constraining the geometry of the crack on the surface the final solution furnished a good fit for all measurements defining a shallow tensile crack located inside the volcanic edifice which represents the effect of the intrusion and a depressuring body with centre at ca 3000 m b s l which could represent the centre of a generalized and more complex deflation of the volcanic edifice during the course of the eruption

structure and dynamics of the summertime pacific japan teleconnection pattern convective activity over the tropical western pacific is known to influence the extratropical circulation over east asia in the boreal summer in the form of teleconnection called the pacific japan pj pattern but its structure and dynamics have not yet been studied in depth in this study a composite analysis is performed for 32 monthly events of enhanced convection observed to the east of the philippines the composited monthly mean vorticity anomalies associated with the pj pattern are elongated zonally with a distinct poleward tilt with height this structure differs fundamentally from a combination of the first baroclinic mode in the tropics and the barotropic structure in midlatitudes as has widely been accepted as a conceptual model of the pj pattern a wave activity flux points polewards only in the lower troposphere indicating that rossby wave teleconnection occurs primarily through a low level south westerly jet those tilted anomalies over the western pacific can effectively gain kinetic energy in the exits of the mean jet streams in the upper and lower troposphere and available potential energy ape in the presence of the vertically sheared jets the enhanced convection can generate ape effectively and the associated low level anomalous circulation acts to increase moisture supply into the convective region while enhancing evaporation from the pre warmed ocean surface it is thus hypothesized that the pj pattern may be regarded as a dynamical mode that can be effectively excited in the zonally asymmetric baroclinic mean flow associated with the asian summer monsoon with an efficient self sustaining mechanism through moist processes copyright 2006 royal meteorological society

relative role of dynamic and thermodynamic processes in the development of the indian ocean dipole an ogcm diagnosis 1 the relative role of oceanic dynamics and surface heat fluxes in the initiation and development of the indian ocean dipole was investigated by analyzing results from an oceanic general circulation model the model was forced by observed surface wind stress and heat flux fields for 1958 1997 the results show that it was capable of reproducing observed dipole events over the tropical indian ocean the diagnosis of the mixed layer heat budget indicates that the sst anomaly ssta in the east pole is primarily induced by anomalous surface latent heat flux and vertical temperature advection whereas in the west pole it is mainly caused by meridional and vertical temperature advection anomalies in both regions shortwave radiation anomalies tend to damp the ssta the ocean rossby waves are essential in linking the anomalous wind and sst off sumatra and subsurface temperature variations in southwest indian ocean

the role of reversed equatorial zonal transport in terminating an enso event abstractthis study shows the sudden basinwide reversal of anomalous equatorial zonal transport above the thermocline at the peaking phase of enso triggers rapid termination of enso events the anomalous equatorial zonal transport is controlled by the concavity of anomalous thermocline meridional structure across the equator during the developing phase of enso opposite zonal transport anomalies form in the western central and central eastern equatorial pacific respectively both are driven by the equatorial thermocline anomalies in response to zonal wind anomalies over the western central equatorial ocean at this stage the anomalous zonal transport in the east enhances enso growth through zonal sst advection in the mature phase of enso off equatorial thermocline depth anomalies become more dominant in the eastern pacific because of the reflection of equatorial signals at the eastern boundary as a result the meridional concavity of the thermocline anomalies is reversed in the east this change reve

pacific east asian teleconnection how does enso affect east asian climate observational evidence is presented to show a teleconnection between the central pacific and east asia during the extreme phases of enso cycles this pacific east asian teleconnection is confined to the lower troposphere the key system that bridges the warm cold events in the eastern pacific and the weak strong east asian winter monsoons is an anomalous lower tropospheric anticyclone cyclone located in the western north pacific the western north pacific wind anomalies develop rapidly in late fall of the year when a strong warm or cold event matures the anomalies persist until the following spring or early summer causing anomalously wet dry conditions along the east asian polar front stretching from southern china northeastward to the east of japan kuroshio extension using atmospheric general circulation and intermediate models the authors show that the anomalous philippine sea anticyclone results from a rossby wave response to suppressed convective heating which is induced by both the in situ ocean surface cooling and the subsidence forced remotely by the central pacific warming the development of the anticyclone is nearly concurrent with the enhancement of the local sea surface cooling both the anticyclone and the cooling region propagate slowly eastward the development and persistence of the teleconnection is primarily attributed to a positive thermodynamic feedback between the anticyclone and the sea surface cooling in the presence of mean northeasterly trades the rapid establishment of the philippine sea wind and sst anomalies implies the occurrence of extratropical tropical interactions through cold surge induced exchanges of surface buoyancy flux the central pacific warming plays an essential role in the development of the western pacific cooling and the wind anomalies by setting up a favorable environment for the anticyclone sst interaction and midlatitude tropical interaction in the western north pacific

the interpretation of gravity changes and crustal deformation in active volcanic areas simple models like the well known point source of dilation mogi s source in an elastic homogeneous and isotropic half space are widely used to interpret geodetic and gravity data in active volcanic areas this approach appears at odds with the real geology of volcanic regions since the crust is not a homogeneous medium and magma chambers are not spheres in this paper we evaluate several more realistic source models that take into account the influence of self gravitation effects vertical discontinuities in the earth s density and elastic parameters and non spherical source geometries our results indicate that self gravitation effects are second order over the distance and time scales normally associated with volcano monitoring for an elastic model appropriate to long valley caldera we find only minor differences between modeling the 1982 1999 caldera unrest using a point source in elastic homogeneous half spaces or in elasto gravitational layered half spaces a simple experiment of matching deformation and gravity data from an ellipsoidal source using a spherical source shows that the standard approach of fitting a center of dilation to gravity and uplift data only excluding the horizontal displacements may yield estimates of the source parameters that are not reliable the spherical source successfully fits the uplift and gravity changes overestimating the depth and density of the intrusion but is not able to fit the radial displacements

upper tropospheric forcing on late july monsoon transition in east asia and the western north pacific abstractby investigating the large scale circulation in the upper troposphere it is demonstrated that the rapid late july summer monsoon transition in the east asia and western north pacific ea wnp is associated with a weakened westerly at the exit of the east asian jet stream eajs even in a normally stable atmosphere under the influence of the north pacific np high in late july convection rapidly develops over the midoceanic region of the western np 15 25 n 150 170 e prior to the rapid transition the eajs weakens and shifts northward which induces a series of changes in downstream regions the northeastern stretch of the asian high weakens upper tropospheric divergence in the region southwest of the mid np trough increases and convection is enhanced at the monsoon transition upper level high potential vorticity intrudes southward and westward convection expand from the mid np westward to cover the entire subtropical western np the lower tropospheric monsoon trough deepens surface

pacific east asian teleconnection part ii how the philippine sea anomalous anticyclone is established during el nino development the anomalous philippine sea anticyclone psac conveys impacts of el nino to east asian climate during the mature and decay of an el nino from the winter to ensuing summer it is shown that the anomalous psac forms in fall about one season prior to the peak el nino its strength increases with the el nino intensity and its sign reverses during a la nina the psac formation concurs with abnormal deepening of the east asian trough and with increasing number of northward recurvature of tropical storms in the western pacific the psac establishment is abrupt coupling with a swing from a wet to dry phase of an intraseasonal oscillation iso and often concurrent with early retreat of the east asian summer monsoon the iso becomes inactive after psac establishment the development of the psac is attributed to combined effects of the remote el nino forcing tropical extratropical interaction and monsoon ocean interaction the developing el nino induces off equatorial as cending rossby wave responses and land surface cooling in northeast asia both deepen the east asian trough in fall and induces vigorous tropical extratropical exchange of air mass and heat which enhances the cold air outbreak and initiation of the psac through exciting descending rossby waves the el nino induced indonesian subsidence generates low level anticyclonic vorticity over south asia which is advected by mean monsoon westerly instigating the anomalous psac the iso interacting with the underlying ocean plays a critical role in the abrupt establishment of psac the wind evaporation entrainment feedback tends to amplify suppress iso before after winter northeasterly monsoon commences suggesting the roles of atmosphere ocean inter action and the seasonal march of background winds in changing the philippine sea iso intensity and maintaining psac

global plasmasphere evolution 22 23 april 2001 1 the evolution of the plasmasphere during the moderate 22 23 april 2001 storm is studied by comparing observed plasmasphere behavior to the predictions of a simulation the plasmasphere observations include global images from image euv and density and flow measurements from lanl mpa the subjective uncertainty in the euv plasmapause was found to be 0 2l inward plasmapause motion was correlated with southward interplanetary magnetic field imf with a 27 min delay the electric e field at the plasmapause was approximately 13 of the solar wind e field the observations support the idea that plasmaspheric erosion begins with a partial plasmapause indentation which then gradually widens in magnetic local time mlt to encompass the entire nightside in situ measurements confirm a dayside plume of sunward flowing plasma and images show that the plume subsequently experienced phases of mlt narrowing and rotation wrapping to simulate the event we employed a test particle representation of the plasmapause using a parametric e field model that includes corotation and convection from two sources dayside magnetopause reconnection dmr and the subauroral polarization stream saps the model captures the phases of plume evolution and it reproduces the observed plasmapause with maximum mean error 0 7l 0 24l the model fails to reproduce important subglobal features e g a predawn plasmaspheric shoulder and grossly misplaces the inner edge of the rotating and wrapping plume saps contributes significantly to the duskside flows but the simulated flows are about 50 smaller than those seen by lanl mpa the simulated plasmapause e field is about 70 of the euv inferred value

on the relationship between indian ocean sea surface temperature and the transition from el nino to la nina the relationship between indian ocean sea surface temperature and the transition of el nino events into either la nina or el nino southern oscillation neutral conditions is examined in both observations and the retrospective ensemble hindcasts of the national center for environmental prediction climate forecast system the southern indian ocean is shown to demonstrate a particularly robust and consistent relationship with the evolution of these transitions these associations are described and a physical mechanism involving air sea interaction in the indian and western pacific oceans is proposed observations suggest that easterly surface wind anomalies in the western pacific ocean are associated with the emergence of la nina during boreal summer and fall here it is shown that these winds are significantly correlated to southern indian ocean sea surface temperature in the preceding spring that is characterized by a large scale zonal dipole of cool and warm anomalies in the southwestern and southeastern indian oceans respectively these associations are particularly pronounced for strong el nino conditions during the dissipation of which a pronounced wavetrain like atmospheric pattern accompanies sea surface temperature anomalies in the southern indian ocean together the circulation and sea surface temperature anomalies increase the meridional cross equatorial temperature gradient in the western indian ocean and mute intraseasonal variability while strengthening surface equatorial easterly winds in the indo pacific warm pool collectively these anomalies favor subsequent la nina development on the basis of these observed associations a predictive model that demonstrates skill in anticipating the nature of el nino transitions involving the southern indian ocean asian monsoon and el nino southern oscillation is proposed in the national center for environmental prediction climate forecast system the relationships described above are simulated both consistently and realistically despite model weaknesses further bolstering a key role of southern indian ocean and predictive relationship comparison of fully coupled and sea surface temperature forced simulations suggests a key role for air sea interaction in the observed associations moreover it is demonstrated that coupled simulations of el nino southern oscillation may benefit substantially from improved representation of indian ocean variability and indo pacific interaction

role of subtropical precipitation anomalies in maintaining the summertime meridional teleconnection over the western north pacific and east asia abstract the meridional teleconnection patterns over the western north pacific and east asia wnp ea during summer have a predominant role in affecting east asian climate on the interannual time scale a well known seesaw pattern of tropical subtropical precipitation is associated with the meridional teleconnection and the subtropical precipitation anomaly has been previously viewed as a result of anomalous circulations associated with the teleconnection in this study however the authors suggest that subtropical precipitation anomalies in turn can significantly affect large scale circulations and may be crucial for maintenance of the meridional teleconnection diagnosis by using observational and reanalysis data indicates that the meridional teleconnection patterns are clearer in summers when the subtropical rainfall anomalies are greater the simulated results by a linear baroclinic model indicate that a subtropical heat source which is equivalent to the diagnosed positive subtropical precipitati

the influence of atmospheric convection on the interaction between the indian ocean and enso abstractin recent years it has been proposed that a negative positive indian ocean dipole iod in boreal autumn favors an el nino la nina at a lead time of 15 months observational analysis suggests that a negative iod might be accompanied by easterly anomalies over the western pacific such easterlies can enhance the western pacific warm water volume thus favoring el nino development from the following boreal spring onward however a gill model response to a negative iod forcing would lead to nearly zero winds over the western pacific the authors hypothesize that a negative iod or even a cool western indian ocean alone leads to low level air convergence and hence enhanced convectional heating over the maritime continent which in turn amplifies the wind convergence so as to cause easterly winds over the western pacific this hypothesis is tested by coupling an idealized indian ocean model and a convective feedback model over the maritime continent to the zebiak cane model it is found that for a

mayon volcano philippines change of monitoring strategy after microgravity and gps measurements from 1992 to 1996 abstract mayon volcano is part of the bicol volcanic chain on the island luzon philippines during this century there were ten activity periods distributed almost regularly because of the density of population about one million people living in the vicinity of the volcano three seismological observatories are in operation measurements of gravity changes started in 1992 just before the eruption of february march 1993 two profiles at the slope were established connected to a regional network around the volcano in order to enable the determination of mass changes between the campaigns the height control was provided by parallel gps measurements in all the network consists of 26 points which were remeasured with three gravimetres at least three times within one campaign during five campaigns within 4 years the differential gps gives no significant changes of the elevation within 4 cm nevertheless the gravity increased significantly by up to 1500 nm s2 equivalent to 150 gal as no significant change of elevation is observed gps no extended shallow magma chamber system below the volcano can be proved this is in accordance with geochemical results indicating a rather undifferentiated magma the youngest lava which is of interest for the eruption dynamics belongs to the medium k basaltic andesite field of the k2o vs sio2 diagram a rather qualitative check of groundwater level changes reveals that these cannot be the sources for the observed gravity changes thus the increase of gravity after the eruption of february 1993 can be explained by a mass redistribution in the volcanic vent from above the level of the gravity points to below practical conclusions of these results lead to changes in the monitoring strategy deformation measurements did not reveal any volcanic activities at least for the eruption of 1993 no significant deformation was observed gravity could be an indicator for long term changes thus repeated gravity measurements gps at selected points could be used in parallel to seismic monitoring to detect slow mass movements prior to changes in seismicity

a western pacific oscillator paradigm for the el nino southern oscillation a data based hypothesis is presented on the mechanism of the el nino southern oscillation enso a major determinant of interannual global climate variability the hypothesis emphasizes the importance of off equator sea surface temperature and sea level pressure variations west of the dateline for initiating equatorial easterly winds over the far western pacific these winds compete with westerly winds over the equatorial central pacific enabling the coupled ocean atmosphere system to oscillate consistent with this hypothesis an analogical oscillator model is constructed that produces enso like oscillations the proposed mechanism differs from the delayed oscillator paradigm in that wave reflection at the western boundary is not a necessary condition for the coupled ocean atmosphere system to oscillate

gravity changes and passive so2 degassing at the masaya caldera complex nicaragua an understanding of the mechanisms responsible for persistent volcanism can be acquired through the integration of geophysical and geochemical data sets by interpreting data on micro gravity ground deformation and so2 flux collected at masaya volcano since 1993 it is now clear that the characteristically cyclical nature of the activity is not driven by intrusion of additional magma into the system rather it may be due in large part to the blocking and accumulation of gas by restrictions in the volcano substructure the history of crater collapse and formation of caverns beneath the crater floor would greatly facilitate the trapping and storage of gas in a zone immediately beneath san pedro and the other craters another mechanism that may explain the observed gravity and gas flux variations is the convective overturn of shallow pre existing degassed cooled dense magma that is replaced periodically by lower density hot gas rich magma from depth buoyant gas rich magma rises from depth and is emplaced near the surface resulting in the formation and fluctuation of a low density gas rich layer centred beneath nindiri and santiago craters as this magma vigorously degasses it must cool increase in density and eventually sink five stages of activity have been identified at masaya since 1853 and the most recent data suggest that the system may have been entering another period of reduced degassing in 2000 this type of analysis has important implications for hazard mitigation because periods of intense degassing are associated with poor agricultural yields and reduced quality of life a better understanding of persistent cyclically active volcanoes will allow for more effective planning of urban development and agricultural land use

three dimensional indirect boundary element method for deformation and gravity changes in volcanic areas application to teide volcano tenerife canary islands 1 most deformation models of volcanoes assume that the earth is a linear elastic isotropic and homogeneous half space although some volcanic areas are associated with significant relief we investigate the effects of topography on surface deformation and gravity changes caused by a magma intrusion in the earth s crust a three dimensional 3 d indirect boundary element method ibem that incorporates realistic topographic features is developed in order to perform this analysis our results show that the topography alters both the magnitude and pattern of the deformation and gravity signal as an example of realistic topography we consider a spherical source of dilatation located at 4 km depth below teide volcano summit tenerife canary islands in order to simulate the deformation and gravity changes that could be observed at tenerife if a hypothetical intrusion occurred in the volcanic system this approach gives a picture of the 3 d topographic effect at teide that can provide insight in order to improve the geodetic monitoring of the volcano

improved extended reconstruction of sst 1854 1997 abstract an improved sst reconstruction for the 1854 1997 period is developed compared to the version 1 analysis in the western tropical pacific the tropical atlantic and indian oceans more variance is resolved in the new analysis this improved analysis also uses sea ice concentrations to improve the high latitude sst analysis and a modified historical bias correction for the 1939 41 period in addition the new analysis includes an improved error estimate analysis uncertainty is largest in the nineteenth century and during the two world wars due to sparse sampling the near global average sst in the new analysis is consistent with the version 1 reconstruction the 95 confidence uncertainty for the near global average is 0 4 c or more in the nineteenth century near 0 2 c for the first half of the twentieth century and 0 1 c or less after 1950

plasmapause undulation of 17 april 2002 1 we report image euv observations of a striking undulatory motion of the plasmapause that occurred on 17 april 2002 in which a large ripple propagated westward across the duskside plasmapause from the plasmapause motion we infer a peak e field of 3 mv m associated with the undulation and estimate the undulation s equatorial azimuthal speed to be 0 9 rad hr 4 re hr corresponding to 1 km s in the ionosphere using an r3 2 dependence to map from the equator because dmsp ion drift data at 850 km altitude show the presence of a subauroral polarization stream saps flow channel 1 km s at the same location and time as the undulation we assert that saps was responsible for removal of plasma during the undulation the saps apparently formed in response to a 19 00 ut substorm onset

impact of the indian ocean sst basin mode on the asian summer monsoon 1 following an el nino event a basin wide warming takes place over the tropical indian ocean peaks in late boreal winter and early spring and persists through boreal summer our observational analysis suggests that this indian ocean warming induces robust climatic anomalies in the summer indo west pacific region prolonging the el nino s influence after tropical east pacific sea surface temperature has returned to normal in response to the indian ocean warming precipitation increases over most of the basin forcing a matsuno gill pattern in the upper troposphere with a strengthened south asian high near the ground the southwest monsoon intensifies over the arabian sea and weakens over the south china and philippine seas an anomalous anticyclonic circulation forms over the subtropical northwest pacific collocated with negative precipitation anomalies all these anomaly patterns are reproduced in a coupled model simulation initialized with a warming in the tropical indian ocean mixed layer indicating that the indian ocean warming is not just a passive response to el nino but important for summer climate variability in the indo west pacific region the implications for seasonal prediction are discussed

dynamical and boundary forcing characteristics of regional components of the asian summer monsoon abstract in this paper the authors present a description of the internal dynamics and boundary forcing characteristics of two major subcomponents of the asian summer monsoon asm that is the south asian monsoon sam and the east southeast asian monsoon eam the description is based on a new monsoon climate paradigm in which the variability of asm is considered as the outcome of the interplay of a fast and an intermediate monsoon subsystem under the influence of slow external forcings two sets of regional monsoon indices derived from dynamically consistent rainfall and wind data are used in this study results show that the internal dynamics of sam are representative of a classical monsoon system in which the anomalous circulation is governed by rossby wave dynamics where anomalous vorticity induced by an off equatorial heat source is balanced by the advection of planetary vorticity on the other hand the internal dynamics of eam are characterized by a hybrid monsoon system featuring m

mechanisms of meridional teleconnection observed between a summer monsoon system and a subtropical anticyclone part i the pacific japan pattern abstract summertime atmospheric circulation over the midlatitude western north pacific wnp is influenced by anomalous convective activity near the philippines this meridional teleconnection observed in monthly anomalies and known as the pacific japan pj pattern is characterized by zonally elongated cyclonic and anticyclonic anomalies around the enhanced convection center and to its northeast respectively in the lower troposphere with an apparent poleward phase tilt with height the authors idealized two layer linear model whose basic state consists of a zonal subtropical jet and a pair of a monsoon system and a subtropical anticyclone can simulate a pj like response against diabatic heating located between the pair each of the observed and simulated patterns can gain energy through barotropic and baroclinic conversions from the zonally varying baroclinic mean flow in an efficiency comparable with that of energy generation due to the anomalous diabatic heating indicating a characteristic of

preconditions for el nino and la nina onsets and their relation to the indian ocean 1 el nino la nina onset is a challenging problem of enso prediction in this study we introduce two precursors of el nino and la nina onsets one is the equatorial heat content and the other is the western pacific wp wind when the two precursors are considered together both the el nino and la nina onsets can be highly predictable in particular the persistence of the wp wind is more important for the onset than sporadic wind events the persistent wp westerly easterly wind tends to be concurrent with the indian ocean sst cooling warming the indian ocean sst anomaly is partly correlated to an enso event during the previous winter we demonstrate that an asymmetric relation between the indian ocean sst and enso can result in asymmetric progress of onset in the opposite enso phases

el nino la nina and the nonlinearity of their teleconnections the paradigm of an atmospheric system varying linearly with respect to extreme phases of the el nino southern oscillation is questioned it is argued that the global response to tropical pacific sea surface temperature forcing will be inherently nonlinear a physical basis for this intrinsic nonlinearity is the thermodynamic control on deep convection climate statistics for warm and cold events of the tropical pacific are analyzed separately for the northern winter periods during 1950 96 composite analysis of 500 mb heights reveal planetary scale teleconnection patterns as noted in earlier studies a new result is the evidence for an appreciable 358 longitude phase shift between the warm and cold event circulation composites and the two wave trains appear to have different tropical origins a large nonlinear component in north american surface climate anomalies is also found which is consistent with such a phase shift in teleconnections in the tropics rainfall anomalies also show evidence of nonlinear behavior the maximum rain anomalies along the equator are located east of the date line during warm events but west of the date line during cold events the interpretation of this behavior is complicated however by the fact that composite warm event sst anomalies are not the exact inverse of their cold event counterparts idealized atmospheric general circulation model agcm experiments are performed in order to test the question of whether the observed nonlinearity is an intrinsic property of the atmospheric system the model is forced with a composite sst anomaly that undergoes a realistic seasonally varying enso life cycle as described by e rasmusson and t carpenter both positive and negative phases of the sst anomaly are used and a 40 member ensemble of warm and cold event model simulations is conducted a nonlinear climate response in the agcm is found that closely resembles the observed composites including a shift in the equatorial positions of the maxmium rain responses and a phase shift of teleconnection patterns in the upper troposphere barotropic model experiments indicate that the inherent nonlinearity in the tropical rain response may itself be responsible for the phase shift in the extratropical teleconnection patterns

slow variability in the equatorial west central pacific in relation to enso abstract six years of upper ocean velocity temperature and surface wind data collected in the west central pacific at 0 170 w reveal a slow ocean dynamical mode associated with the el nino southern oscillation enso latent and sensible heat flux calculations using the basin wide tropical atmosphere ocean tao array data show a coincident slow ocean atmosphere thermodynamical mode beginning with the la nina conditions in 1988 through the peak el nino conditions in 1992 the equatorial undercurrent euc speed decreased along with the surface zonal wind stress and the zonal pressure gradient simultaneous with these were increasing trends in the richardson number above the euc core and in sea surface temperature sst after peak warming was achieved the variations in all of these quantities reversed in a movement toward their previous la nina conditions as this evolved within the ocean the sensible and latent heat fluxes increased with large values emanating eastward from the western pacific the

the enso asian monsoon interaction in a coupled ocean atmosphere gcm abstract in this study the authors evaluate the el nino southern oscillation enso asian monsoon interaction in a version of the hadley centre coupled ocean atmosphere general circulation model cgcm known as hadcm3 the main focus is on two evolving anomalous anticyclones one located over the south indian ocean sio and the other over the western north pacific wnp these two anomalous anticyclones are closely related to the developing and decaying phases of the enso and play a crucial role in linking the asian monsoon to enso it is found that the hadcm3 can well simulate the main features of the evolution of both anomalous anticyclones and the related sst dipoles in association with the different phases of the enso cycle by using the simulated results the authors examine the relationship between the wnp sio anomalous anticyclones and the enso cycle in particular the biennial component of the relationship it is found that a strong el nino event tends to be followed by a more rapid decay and i

displacements and tilts from dip slip faults and magma chambers beneath irregular surface topography surface displacements and tilts due to buried deformation sources are influenced by topography the leading order corrections due to topography of arbitrary profile but small slope are determined for dip slip faults edge dislocations and magma bodies lines of inflation in a two dimensional elastic medium the vertical displacement correction is simply the product of the topography and the horizontal normal strain due to the source in a flat half space the correction for a normal fault beneath an idealized basin and range topography is a slight increase in the uplift on the range side the effect of topography for a line of inflation beneath a symmetric volcano is to reduce the central uplift failure to account for topographic influences can bias estimates of source depth and geometry

rapid termination of the 2006 el nino and its relation to the indian ocean 1 we investigated the rapid termination of the 2006 el nino using observed data and a coupled ocean atmosphere general circulation model cgcm observed data showed development of an anomalous south indian ocean sio anticyclone associated with the concurrent indian ocean dipole during september november 2006 at the end of 2006 the eastward retreat of the sio anticyclone in response to the indian ocean warming generated an easterly anomaly over the western pacific and the resultant oceanic upwelling kelvin wave terminated the el nino cgcm experiments indicated that the formation of the sio anticyclone was influenced remotely by the pacific ocean sst anomalies and that the easterly anomaly over the western pacific at the end of 2006 was reinforced by the indian ocean sst anomalies these results suggest that interactive feedback between the indian and pacific oceans helped the rapid termination of the 2006 event

teleconnected influence of north atlantic sea surface temperature on the el nino onset influence of north atlantic sea surface temperature sst anomalies on tropical pacific sst anomalies is examined both summer and winter north atlantic sst anomalies are negatively related to central eastern tropical pacific sst anomalies in the subsequent months varying from 5 to 13 months in particular when the north atlantic is colder than normal in the summer an el nino event is likely to be initiated in the subsequent spring in the tropical pacific associated with summer cold north atlantic sst anomalies is an anomalous cyclonic circulation at low level over the north atlantic from subsequent october to april corresponded to this local response an sst induced heating over the north atlantic produces a teleconnected pattern similar to the east atlantic west russia teleconnection the pattern features two anticyclonic circulations near england and lake baikal and two cyclonic circulations over the north atlantic and near the caspian sea the anticyclonic circulation near lake baikal enhances the continent northerlies and strengthens the east asian winter monsoon these are also associated with an off equatorial cyclonic circulation in the western pacific during the subsequent winter and spring which produces equatorial westerly wind anomalies in the western pacific the equatorial westerly wind anomalies in the winter and spring can help initiate a pacific el nino event following a cold north atlantic in the summer

the non linear relationship between the western north pacific anticyclonic circulation and korean summer precipitation on subseasonal timescales it has been widely known that the pulse of the western north pacific anticyclonic circulation wnpac plays a key role on east asian summer climate variability in subseasonal to interannual time scales yet the relation between the wnpac and summer precipitation over korea is not robust on seasonal and subseasonal timescales for the recent few decades here we show that the low correlation between wnpac and korean precipitation is attributable to their distinctive non linear relationship and investigate detailed features in their four different phase relationships on subseasonal time scales first the positive korean precipitation anomaly occurs as the part of zonally elongated precipitation band along with the positive wnpac anomaly closely connected with the decaying phase of el nino and indian ocean warming the second case is enhanced korean precipitation accompanying with negative wnpac anomaly in this case the negative wnpac anomaly constitutes a part of atmospheric wave train across the north pacific and this feature is associated with the decaying phase of la nina the typhoon related precipitation event also contributes to this case third the negative korean precipitation anomaly arises when the low level easterly anomaly along with the northern flank of negative wnpac anomaly leads to suppressed convective activity in korea lastly the negative korean precipitation anomaly happens with the positive wnpac anomaly when anomalous high covers entire east asia and the wnp mainly during the decaying phase of central pacific el nino the understanding of the non linear relationship between wnpac and korean precipitation in this study provides better insight into the potential impacts of el nino southern oscillation and circulation convection anomaly over the wnp on summer korean precipitation