peculiar features of the low latitude and midlatitude ionospheric response to the st patrick s day geomagnetic storm of 17 march 2015 the current study aims at investigating and identifying the ionospheric effects of the geomagnetic storm that occurred during 17 19 march 2015 incidentally with sym h hitting a minimum of 232 nt this was the strongest storm of the current solar cycle 24 the study investigates how the storm has affected the equatorial low latitude and midlatitude ionosphere in the american and the european sectors using available ground based ionosonde and gps tec total electron content data the possible effects of prompt electric field penetration is observed in both sectors during the main phase of the storm in the american sector the coexistence of both positive and negative ionospheric storm phases are observed at low latitudes and midlatitudes to high latitudes respectively the positive storm phase is mainly due to the prompt penetration electric fields the negative storm phase in the midlatitude region is a combined effect of disturbance dynamo electric fields the equatorward shift of the midlatitude density trough and the equatorward compression of the plasmapause in combination with chemical compositional changes strong negative ionospheric storm phase is observed in both ionosonde and tec observations during the recovery phase which also shows a strong hemispherical asymmetry additionally the variation of equatorial ionization anomaly as seen through the swarm constellation plasma measurements across different longitudes has been discussed we also take a look at the performance of the iri real time assimilative mapping during this storm as an ionospheric space weather tool

disturbance zonal and vertical plasma drifts in the peruvian sector during solar minimum phases in the present work we investigate the behavior of the equatorial f region zonal plasma drifts over the peruvian region under magnetically disturbed conditions during two solar minimum epochs one of them being the recent prolonged solar activity minimum the study utilizes the vertical and zonal components of the plasma drifts measured by the jicamarca 11 95 s 76 87 w incoherent scatter radar during two events that occurred on 10 april 1997 and 24 june 2008 and model calculation of the zonal drift in a realistic ionosphere simulated by the sheffield university plasmasphere ionosphere model inpe two main points are focused 1 the connection between electric fields and plasma drifts under prompt penetration electric field during a disturbed periods and 2 anomalous behavior of daytime zonal drift in the absence of any magnetic storm a perfect anticorrelation between vertical and zonal drifts was observed during the night and in the initial and growth phases of the magnetic storm for the first time based on a realistic low latitude ionosphere we will show on a detailed quantitative basis that this anticorrelation is driven mainly by a vertical hall electric field induced by the primary zonal electric field in the presence of an enhanced nighttime e region ionization it is shown that an increase in the field line integrated hall to pedersen conductivity ratio h p which can arise from precipitation of energetic particles in the region of the south american magnetic anomaly is capable of explaining the observed anticorrelation between the vertical and zonal plasma drifts evidence for the particle ionization is provided from the occurrence of anomalous sporadic e layers over the low latitude station cachoeira paulista 22 67 s 44 9 w brazil it will also be shown that the zonal plasma drift reversal to eastward in the afternoon two hours earlier than its reference quiet time pattern is possibly caused by weakening of the zonal wind system during the prolonged solar minimum period

comparison of the vertical distributions of cloud properties from idealized extratropical deep convection simulations using various horizontal resolutions abstractthe authors coarse grained and analyzed the output from a large eddy simulation les of an idealized extratropical supercell storm using the weather research and forecasting wrf model with various horizontal resolutions 200 m 400 m 1 km and 3 km the coarse grained physical properties of the simulated convection were compared with explicit wrf simulations of the same storm at the same resolution of coarse graining the differences between the explicit simulations and the coarse grained les output increased as the horizontal grid spacing in the explicit simulation coarsened the vertical transport of the moist static energy and total hydrometeor mixing ratio in the explicit simulations converged to the les solution at the 200 m grid spacing based on the analysis of the coarse grained subgrid vertical flux of the moist static energy the authors confirmed that the nondimensional subgrid vertical flux of the moist static energy varied with the subgrid fractional cloudiness according to a fun

auroral electrojets during geomagnetic storms on the basis of digital magnetometers from the international monitor auroral geomagnetic effects image and european incoherent scatter eiscat meridional chains in scandinavia dynamics of the eastward and westward electrojets during the main phase of magnetic storms are considered for the intense magnetic storm on may 10 11 1992 with dst 300 nt magnetograms of subauroral and midlatitudinal stations leningrad borok and moscow were examined it is found that the eastward electrojet center during the storm main phase shifts equatorward as dst increases the electrojet center is located at the corrected geomagnetic latitude 59 60 when dst 100 nt and at 54 55 when dst 300 nt data from meridional chains of magnetometers support earlier results pertaining to the relationship between the westward electrojet center position and the ring current intensity for intervals between substorms during substorms expansive phases the westward electrojet expands poleward covering auroral latitudes 65 the electrojets location during the storm main phase and their dynamics in connection with substorms allow for interpretations of effects described in the literature the ae indices saturation during the main phase of magnetic storms approximately equal values of au and al indices during the storm initial phase and al au during the storm main phase

equatorial westward electrojet impacting equatorial ionization anomaly development during the 6 april 2000 superstorm we investigate the forward plasma fountain and the equatorial ionosphere in the topside region during the 6 april 2000 superstorm in the australian sector at 0900 lt space and ground based multi instrument measurements coupled thermosphere ionosphere plasmasphere electrodynamics ctipe simulations and field aligned observations comprise our results these reveal an unusual storm development during which the eastward prompt penetration electric e field ppef developed and operated under the continuous effects of the westward disturbance dynamo e field ddef while large scale traveling ionospheric disturbances tids traveled equatorward and generated strong equatorward wind surges we have identified the eastward ppef by the superfountain effect causing the equatorial ionization anomaly eia s development with crests situated at 28 n geomagnetic in the topside ionosphere at 840 km altitude the westward ddef s occurrence is confirmed by mapping the anti sq current system wherein the equatorial westward current created a weak long lasting westward electrojet event line plots of vertical drift data tracked large scale tids four scenarios covering 3 5 h in universal time demonstrate that the westward ddef became superimposed on the eastward ppef as these e fields of different origins became mapped into the f region they could interact consequently the eastward ppef related equatorial upward e b drift became locally reduced by up to 75 m s near the dip equator by the westward ddef related equatorial downward e b drift meanwhile the eia displayed a better development as equatorial wind surges reproduced by ctipe increased from 501 to 629 m s demonstrating the crucial role of mechanical wind effects keeping plasma density high key points 6 april 2000 superstorm produced some significant westward electrojet events ppef developed and operated under continuous ddef effects superimposed westward ddef on eastward ppef permitted eia development

the atmospheric boundary layer and the gray zone of turbulence a critical review recent increases in computing power mean that atmospheric models for numerical weather prediction are now able to operate at grid spacings of the order of a few hundred meters comparable to the dominant turbulence length scales in the atmospheric boundary layer as a result models are starting to partially resolve the coherent overturning structures in the boundary layer in this resolution regime the so called boundary layer gray zone neither the techniques of high resolution atmospheric modeling a few tens of meters resolution nor those of traditional meteorological models a few kilometers resolution are appropriate because fundamental assumptions behind the parameterizations are violated nonetheless model simulations in this regime may remain highly useful in this paper a newly formed gray zone boundary layer community lays the basis for parameterizing gray zone turbulence identifies the challenges in high resolution atmospheric modeling and presents different gray zone boundary layer models we discuss both the successful applications and the limitations of current parameterization approaches and consider various issues in extending promising research approaches into use for numerical weather prediction the ultimate goal of the research is the development of unified boundary layer parameterizations valid across all scales

hydrothermal element fluxes from copahue argentina a beehive volcano in turmoil copahue volcano erupted altered rock debris siliceous dust pyroclastic sulfur and rare juvenile fragments between 1992 and 1995 and magmatic eruptions occurred in july october 2000 prior to 2000 the copahue crater lake acid hot springs and rivers carried acid brines with compositions that reflected close to congruent rock dissolution the ratio between rock forming elements and chloride in the central zone of the volcano hydrothermal system has diminished over the past few years reflecting increased water rock ratios as a result of progressive rock dissolution magmatic activity in 2000 provided fresh rocks for the acid fluids resulting in higher ratios between rock forming elements and chloride in the fluids and enhanced mg fluxes the higher mg fluxes started several weeks prior to the eruption model data on the crater lake and river element flux determinations indicate that copahue volcano was hollowed out at a rate of about 20 000 25 000 m 3 yr but that void space was filled with about equal amounts of silica and liquid elemental sulfur the extensive rock dissolution has weakened the internal volcanic structure making flank collapse a volcanic hazard at copahue

scintillation producing fresnel scale irregularities associated with the regions of steepest tec gradients adjacent to the equatorial ionization anomaly 1 using ground based gps and digital ionosonde instruments we have built up at latitudes of the equatorial ionization anomaly eia in the brazilian sector a time evolving picture of total electron content tec l band amplitude scintillations and f region heights and we have investigated likely reasons for the occurrence or suppression of equatorial scintillations during the disturbed period of 18 23 november 2003 during the prestorm quiet nights scintillations are occurring postsunset as expected however during the storm time period their spatial temporal characteristics and intensity modify significantly owing to the dramatic changes in the ionospheric plasma density distribution and in the temporal evolution of tec the two dimensional maps showing both tec and amplitude scintillations revealed strong evidence of turbulences at the fresnel length causing scintillations concurrent with those regions of steepest tec gradients adjacent to the crests of the eia the largest density gradients have been found to occur in an environment of increased background electron density and their spatial distribution and location during the disturbed period may differ significantly from the magnetic quiet night pattern however in terms of magnitude the gradients at equatorial and low latitudes appear to not change during both magnetic quiet and disturbed conditions the scenarios for the formation or suppression of scintillation producing fresnel scale irregularities during the prestorm quiet nights and disturbed nights are discussed in view of different competing effects computed from numerical simulation techniques

explicit convection and scale aware cumulus parameterizations high resolution simulations over areas of different topography in germany abstractan increase in the spatial resolution of regional climate model simulations improves the representation of land surface characteristics and may allow the explicit calculation of important physical processes such as convection the present study investigates further potential benefits with respect to precipitation based on a small ensemble of high resolution simulations with wrf with grid spacings up to 1 km the skill of each experiment is evaluated regarding the temporal and spatial performance of the simulation of precipitation of one year over both a mountainous region in southwestern germany and a mainly flat region in northern germany this study allows us to differentiate between the impact of grid spacing topography and convection parameterization furthermore the performance of a state of the art convection parameterization scheme in the gray zone of convection is evaluated against an explicit calculation of convection only our evaluation demonstrates the following high resolution si

empirical models of storm time equatorial zonal electric fields ionospheric plasma drifts often show highly complex and variable signatures during geomagnetically active periods due to the effects of different disturbance processes we describe initially a methodology for the study of storm time dependent ionospheric electric fields we present empirical models of equatorial disturbance zonal electric fields obtained using extensive f region vertical plasma drift measurements from the jicamarca observatory and auroral electrojet indices these models determine the plasma drift perturbations due to the combined effects of short lived prompt penetration and longer lasting disturbance dynamo electric fields we show that the prompt penetration drifts obtained from a high time resolution empirical model are in excellent agreement with results from the rice convection model for comparable changes in the polar cap potential drop we also present several case studies comparing observations with results obtained by adding model disturbance drifts and season and solar cycle dependent average quiet time drift patterns when the disturbance drifts are largely due to changes in magnetospheric convection and to disturbance dynamo effects the measured and modeled drift velocities are generally in good agreement however our results indicate that the equatorial disturbance electric field pattern can be strongly affected by variations in the shielding efficiency and in the high latitude potential and energy deposition patterns which are not accounted for in the model these case studies and earlier results also suggest the possible importance of additional sources of plasmaspheric disturbance electric fields

additional stratifications in the equatorial f region at dawn and dusk during geomagnetic storms role of electrodynamics 1 the role of electrodynamics in producing additional stratifications in the equatorial f region f 3 layer at dawn and dusk during geomagnetic storms is discussed two cases of f 3 layer at dawn 0600 0730 lt on 5 october 2000 and 8 december 2000 and one case of f 3 layer at dusk 1600 1730 lt on 5 october 2000 are observed for the first time by the digital ionosonde at the equatorial station trivandrum 8 5 n 77 e dip 0 5 n in india the unusual f 3 layers occurred during the geomagnetic storms and are associated with southward turning of interplanetary magnetic field b z suggesting that eastward prompt penetration electric field could be the main cause of the f 3 layers the dawn f 3 layer on 5 october is modeled using the sheffield university plasmasphere ionosphere model by using the e x b drift estimated from the real height variation of the ionospheric peak during the morning period the model qualitatively reproduces the dawn f 3 layer while the existing f 2 layer rapidly drifts upward and forms the f 3 layer and topside ledge a new layer forming at lower heights develops into the normal f 2 layer

geochemistry of fluids associated with the 1995 1996 eruption of mt ruapehu new zealand signatures and processes in the magmatic hydrothermal system abstract the 1995 1996 eruption of mt ruapehu has provided a number of insights into the geochemical processes operating within the magmatic hydrothermal system of this volcano both pre eruption degassing of the rising magma and its eventual intrusion into the convective zone of the hydrothermal system beneath the lake were clearly reflected in lake water compositions the eruptions of september october 1995 expelled the lake and provided the first ever opportunity to characterise gas discharges from this volcano the fumarolic discharges revealed compositions typical of andesite volcanoes and strong interaction with the enclosing meteoric and hydrothermal system fluids some 1 1 mt of so 2 gas was released from the volcano between september 1995 and december 1996 whereas ca twice this amount 2 2 mt equivalent so 2 was erupted as soluble i e leachable oxyanions of sulphur significantly more sulphur was released from the volcano over this period than can be accounted for from the magma volume actually erupted the evidence suggests that a sizable component of the evolved sulphur was remobilised from the long lived hydrothermal system within the volcano during the 1995 1996 activity

westward plasma drift in the midlatitude ionospheric f region in the midnight dawn sector in this paper we report the observations of a sharp ionospheric plasma velocity reversal boundary at subauroral latitudes during magnetic storms in the midnight dawn sector the zonal plasma drift was eastward poleward of the velocity boundary and became westward equatorward of the boundary the latitudinal extent of the westward drifts was 20 a local maximum of the drift occurred only 2 5 below the boundary the magnitude of the maximum velocity was 200 400 m s 1 between 2100 and 0300 local time lt and as high as 780 m s 1 near midnight the large westward plasma drift immediately equatorward of the velocity boundary first occurred at 2100 lt and continuously extended across midnight to the dawn sector the location of the maximum velocity coincided with the minimum density within the midlatitude ionospheric trough the latitude of the velocity boundary decreased from geographic latitude 53 to 43 corresponding to geomagnetic latitude 65 to 55 between 2100 and 0800 lt we propose that the large westward drift at subauroral latitudes is driven by the polarization jet electric fields in the ring current and that the lower latitude westward drift with moderate magnitude is caused by the disturbance wind dynamo

precipitation origin and evaporation of lakes in semi arid patagonia argentina inferred from stable isotopes δ18o δ2h stable isotope approaches are often used for estimating water balances of lakes such studies require regional background information about hydrogen and oxygen isotope variability of lakes and their potential inflows here a stable isotope database 2h and 18o is presented for estimating evaporation to inflow ratios e i of lakes in semi arid southern patagonia water samples of 23 lakes and ponds located in the patagonian steppe at about 52 s were sampled during three subsequent austral summers two deep crater lakes laguna azul and laguna potrok aike were studied in more detail during a two years monitoring furthermore precipitation groundwater and atmospheric water vapor were sampled for isotope analyses presented data imply that the isotopic composition of rainfall in southeastern patagonia is predominantly determined by precipitation amount and moisture source area for the investigated area the first meteoric water and evaporation lines in 2h vs 18o space are presented the database was further used to estimate the water balances of the two crater lakes laguna azul and laguna potrok aike which are in the focus of recent paleoclimatic investigations according to that approach about 50 and 60 respectively of the water entering laguna azul and laguna potrok aike via surface and subsurface inflow evaporates these results testify a considerable flow of lake waters into the groundwater

long duration penetration of the interplanetary electric field to the low latitude ionosphere during the main phase of magnetic storms 1 it is well known that the interplanetary electric field can penetrate to the low latitude ionosphere it is generally believed that the penetration of electric fields can last only for 30 min because of the shielding effect in the ring current in this paper we present the observations of the dayside ionospheric electric field enhancements at middle and low latitudes in association with reorientations of the interplanetary magnetic field imf in six cases the eastward electric field in the dayside equatorial ionosphere measured by the jicamarca incoherent scatter radar was enhanced for 2 3 hours after the imf turned southward and remained continuously southward in one case the eastward electric field in the dayside midlatitude ionosphere measured by the millstone hill incoherent scatter radar was continuously enhanced for 10 hours during southward imf since millstone hill is close to the equatorward boundary of the auroral zone during magnetic storms the penetration electric field there may be different from that at the equatorial ionosphere the most striking feature of the measurements is that the enhancements of the ionospheric electric field can last for many hours without significant decay the electric field enhancements in the middle and low latitude ionosphere are closely related to magnetic activity and occur during the main phase of magnetic storms the observations show that the interplanetary electric field can continuously penetrate to the low latitude ionosphere without shielding for many hours as long as the strengthening of the magnetic activity is going on under storm conditions

explicit filtering and reconstruction to reduce grid dependence in convective boundary layer simulations using wrf les abstractas model grid resolutions move from the mesoscale to the microscale turbulent structures represented in atmospheric boundary layer simulations change dramatically at intermediate resoluti

a statistical study on the characteristics of ionospheric storms in the equatorial ionization anomaly region gps tec observed over taiwan 1 positive and negative signatures of the ionospheric storms caused by the penetration electric field disturbance dynamo neutral wind neutral composition etc have been reported in this paper the ionospheric total electron content tec derived from the records of a network of ground based gps receivers in taiwan is used to statistically study the characteristics such as local time of appearance and duration of the storm signatures of various casuals in the equatorial ionization anomaly eia region during 1994 2003 a bias corrected accelerated bootstrap method and a z test are employed for the first time to detect each event and the overall storm signatures and characteristics respectively it is found that the positive signatures that appeared minutes to hours after the geomagnetic storm onset are pronounced on the storm day and the next day while the negative signatures that started hours after the geomagnetic storm onset can last for as long as the next 4 days the positive signature is statistically significant and most pronounced when the intense geomagnetic storm onset occurs during local afternoon which suggests that the signature may result from a combination of the prompt penetration electric field effect and mechanical effects of equatorward neutral wind additionally the negative signature that is statistically significant and most pronounced in the local afternoon of the storm onset day and or the next day may be produced by the disturbance dynamo or overshielding effects the long lasting negative signature occurred in local midnight noon period on days 2 4 after the storm onset may result from the neutral composition disturbances

diel changes in metal concentrations in a geogenically acidic river rio agrio argentina abstract rio agrio in patagonia argentina is a geogenically acidic stream that derives its low ph waters from condensation of acidic gases near its headwaters on the flanks of the active copahue volcano this study reports the results of three diel 24 h water samplings in three different ph regimes 3 2 4 4 and 6 3 along the river changes in the concentration and speciation of fe dominated the diel chemical changes at all three sites although the timing and intensity of these cycles were different in each reach at the two acidic sampling sites total dissolved fe and dissolved fe iii concentrations decreased during the day and increased at night whereas dissolved fe ii showed the reverse pattern these cycles are explained by fe iii photoreduction as well as enhanced rates of precipitation of hydrous ferric oxide hfo during the warm afternoon hours a strong correlation was observed between fe iii and as at the furthest upstream ph 3 2 site most likely due to co precipitation of as with hfo at the downstream ph 6 3 location fe ii concentrations increased at night as did concentrations of rare earth elements and dissolved al photoreduction does not appear to be an important process at ph 6 3 although it may be indirectly responsible for the observed diel cycle of fe ii due to advection of photochemically produced fe ii from acidic upstream waters the results of this study of a naturally acidic river are very similar to diel trends recently obtained from mining impacted streams receiving acid rock drainage the results are also used to explore the link between geochemistry and microbiology in acidic eco systems for example fe iii photoreduction produces chemical potential energy in the form of metastable fe 2 that helps support the bacterial community in this unique extreme environment

anomalous occurrence features of the preliminary impulse of geomagnetic sudden commencement in the south atlantic anomaly region 1 occurrence features of the preliminary impulse pi of geomagnetic sudden commencement sc both in the pacific ocean and south atlantic anomaly saa regions were investigated using the long term magnetic field data obtained from the circum pan pacific magnetometer network cpmn and nict space weather monitoring nswm magnetometer networks the low latitude preliminary reverse impulse pri at okinawa oki dip latitude 37 97 in the pacific ocean region appeared in all the magnetic local time mlt sectors with the peak occurrence rate of 40 around noon on the other hand the pri occurrence rate at santa maria sma dip latitude 34 35 near the center of the saa region showed a significant enhancement in the daytime sector 0800 1600 h mlt with the peak value of 80 which resembles the occurrence feature of the equatorial pri moreover the pri amplitude around noon at sma was about 3 0 times larger than that at oki from the calculation of the ionospheric conductivity derived from the iri 2007 and nrlmsise 00 models it is shown that the height integrated conductivity was more enhanced in the saa region sma where the ambient magnetic field intensity is weak compared with that in the pacific ocean region oki therefore the anomalous increase of the pri occurrence and amplitude is caused by the significant enhancement of the ionospheric conductivity due to the weakness of the ambient magnetic field intensity in the saa region

shear flow instability in the stable nocturnal boundary layer as observed by doppler lidar during cases 99 abstract this study investigates a shear flow instability observed in the stably stratified nighttime boundary layer on 6 october 1999 during the cooperative atmosphere surface exchange study cases 99 in south central kansas a scanning doppler lidar captured the spatial structure and evolution of the instability and high rate in situ sensors mounted on a nearby 60 m tower provided stability and turbulence data with excellent vertical resolution data from these instruments are analyzed and linear stability analysis lsa is employed to carefully characterize the wave field its interaction with the mean flow and its role in turbulence generation the event persisted for about 30 min and was confined within the shear zone between the surface and a low level jet llj maximum eigenvalues corresponding to the fastest growing mode of the lsa showed good agreement with the basic wave parameters determined from the lidar data good qualitative agreement was also obtained between the eigenfunction of the f

hydrogeochemistry and rare earth element behavior in a volcanically acidified watershed in patagonia argentina abstract the rio agrio watershed in northern patagonia argentina is naturally acidic due to discharges of volcanic h 2 so 4 hcl and hf at its headwaters near the summit of copahue volcano a suite of water samples was collected from the summit of the volcano to a point roughly 40 km downstream where the ph of the rio agrio rose above 6 0 this suite included a sample of the hyperacidic ph the concentrations of ree in the rio agrio decreased by several orders of magnitude through the study area as a result of dilution and chemical attenuation a subtle shift in the slope of shale normalized profiles of dissolved ree concentration was observed from being weakly positive near the source of the rio agrio to showing a weak middle ree enrichment trend in lake caviahue to being weakly negative in the lower reaches of the river the trend to a negative slope across the lanthanide series in the lower river is explained by selective partitioning of the heavier ree to hydrous oxides of fe and al suspended in the water column and accumulating on the riverbed most of the decrease in ree load occurred immediately downstream of the confluence with a tributary that increased the ph of the rio agrio from 4 3 to 6 1 although the mixed water was supersaturated with ree phosphate compounds precipitation of lnpo 4 is not believed to have been a dominant process because the predicted pattern of inter element fractionation from phosphate deposition is inconsistent with the observed trends instead ree attenuation most likely occurred from adsorption onto freshly precipitated hydrous aluminum oxide the behavior of ree in the rio agrio watershed is broadly similar to what has been observed in watersheds that owe their acidity to oxidation of sulfide minerals

ionosphere disturbances observed throughout southeast asia of the superstorm of 20 22 november 2003 1 ionospheric disturbances in the southeast asian region during the super magnetic storm of 20 22 november 2003 were investigated through an ionosonde chain and a gps network assisted by the space borne instruments at early stage of the storm in the postsunset sector large enhancements in the critical frequency of f2 layer and total electron content were observed at northern crest region of the equatorial ionization anomaly eia which might be produced by both the storm meridional wind superimposed with traveling atmospheric disturbances and prompt penetration electric field ppe during the main phase of the storm when interplanetary magnetic field started a 12 h southward turning equatorial ionosphere was elevated to a very high level which should be most probably caused by a long duration ppe event meanwhile at mid low latitudes ionosphere witnessed an initial simultaneous decrease then followed by drastic increases which is very different from the past observations in this region reddy and nishida 1992 combined analysis of the data from the ionosonde and other space based measurement shows that for the present case the penetration efficiency of the interplanetary electric field ief to the equatorial ionosphere was larger at night than in the daytime which agrees with the results of fejer et al 2007 showing the ratios of ppe and ief changes were highly variable with the local time during the recovery phase eia was severely inhibited owing to a wind convergence and possibly because of the westward disturbance dynamo electric field

iron buffer system in the water column and partitioning in the sediments of the naturally acidic lake caviahue neuquen argentina abstract sedimentary iron partitioning was studied for five sediment strata 16 cm depth at three sampling sites of the naturally occurring acidic lake caviahue patagonia argentina additionally water column iron was modeled based on five year period input loadings to study a possible iron buffer system the partition coefficient between the water column and the total iron content of the sediments was also addressed sedimentary iron was found to be distributed on average in the following forms exchangeable 6 iron oxides 4 pyrite and reactive organic matter 38 and residual non andesitic materials with a high content of humic acids 52 furthermore we found that the dissolved iron in the lake was nearly constant throughout the five year period we studied this is consistent with the existence of an iron buffer system in the lake at ph between 2 0 and 3 0 which may cause differential iron precipitation at the delta of the volcanic river with respect to the deeper northern and southern arms sedimentary iron measurements taken at the delta further support the existence of a buffer system where it was found that the iron content in the sub superficial stratum 2 cm was double that of the remainder of the vertical profile at the same site

analytical laboratory comparison of major and minor constituents in an active crater lake abstract the crater lake water from maly semiachik volcano in kamchatka was used for the international analytical laboratory comparison of major and minor elements and hydrogen sulfur and oxygen isotope data eight institutions participated in this program giving analytical results of 9 major and 20 minor elements mainly by using icp aes for cations and ic for anions among the major elements na mg and si showed coefficients of variation cv of 10 or more whereas b al fe mn had coefficients less than 7 the cv of the minor elements co cu p cr pb was much greater 30 while the v analyses agreed well 2000 ppm and so 4 5000 ppm gave considerable ranges 5 1 and 8 8 cv respectively as did the obtained ph values 22 cv the measured 18 o of the water samples and 34 s of sulfate are in excellent agreement but the d values had cv of 8 technical recommendations are presented to improve the analytical results for these elements with significant deviations from the mean values

volcanic nutrient inputs and trophic state of lake caviahue patagonia argentina the strategies for eutrophication control remediation and policy management are often defined for neutral to alkaline freshwater systems as they are most suitable for human use the influence of nutrients on eutrophication in a naturally acidic lake is poorly known the main purpose of the present work is to evaluate the significance of volcanic nutrients in the control of the trophic state of the acidic lake caviahue located at north patagonia argentina acidic water systems were most studied on artificial acidified lakes such as mining lakes in germany or pit lakes in the united states lake caviahue received a very high p load 42 192 ton p yr and low n load 14 ton n yr mainly as ammonium with quite low n p ratios 1 0 the magmatic activity of the copahue volcano represents the main natural contribution of nutrients and acidity to the lake caviahue the lake is oligotrophic in terms of chla neither the transparency nor the nutrient dissolved or particulate contents are to date representative of the trophic state of the lake high p loads do not imply the eutrophication of the lake we suggest that nitrogen and not phosphorus represents the key control nutrient in volcanically acidified lakes as ton was better related to chla observed 0 13 036 mg m 3 in the lake the ph increased around one unit ph 2 0 3 0 during the last five years suggesting that the lake has not yet returned to a stable state

modelling convectively induced secondary circulations in the terra incognita with terrsysmp advances in high performance computing have led to kilometre and even sub kilometre scale regional simulations with numerical weather prediction models this range of grid resolution also termed terra incognita approaches the length scale of the most energetic eddies of the convective atmospheric boundary layer abl which accordingly can only be inadequately resolved this dilemma becomes particularly obvious when simulating convectively induced secondary circulations ciscs in the terra incognita because the modelled cisc like circulations also termed m ciscs are poorly resolved and exhibit a grid resolution dependence previous studies have pointed out this problem using different modelling platforms and also suggested options for attenuating poorly resolved m ciscs with methods specific to the applied abl schemes this study examines m ciscs at horizontal grid resolutions of o 1km using the terrestrial systems modeling platform terrsysmp for idealised and real case studies the analysis of simulations using different surface heterogeneity and grid resolutions of o 1km shows that the presence of a super adiabatic layer near the surface and the increase of the horizontal grid resolution allow the critical rayleigh number to be exceeded generating poorly resolved m ciscs whose amplitudes are strongly dependent on the horizontal grid resolution we show that the asymptotic turbulent mixing length scale in the used abl scheme can be tuned in a way that m ciscs are attenuated while the non resolved turbulence dealt with by the abl scheme effectively propagates the surface fluxes into the abl and sustains reasonable abl profiles

evaluation of the impact of horizontal grid spacing in terra incognita on coupled mesoscale microscale simulations using the wrf framework abstractcoupled mesoscale microscale simulations are required to provide time varying weather dependent inflow and forcing for large eddy simulations under general flow conditions such coupling ne

element flux to the environment of the passively degassing crater lake hosting kawah ijen volcano indonesia and implications for estimates of the global volcanic flux volcanoes play an important role in the global cycling of elements by providing a pathway from the deep earth to its surface here we have constrained the flux to the environment for most elements of the periodic table for the passively degassing crater lake hosting kawah ijen volcano in the indonesian arc our results indicate that emissions of kawah ijen are dominated by acid water outflow especially for the ligands cl f br with active fumaroles contributing significant semi metals e g se as sb hg as well as c and s the compositional signature of emissions from kawah ijen is similar to that of major volcanic emitters such as etna but element fluxes are smaller this result provides the prerequisite foundation for extrapolating a small set of measured volcanic gas emissions to a global volcanic flux estimate however the aqueous flux i e seepage of volcanic hydrothermal fluids and volcano influenced groundwater is at least as important in terms of element release and the consideration of the gaseous flux alone thus represents a significant underestimate of the impact of volcanoes on their environment and the contribution of volcanic hydrothermal systems to global element cycling supplementary material the full datasets of water and fumarole gas chemical analyses are available at https doi org 10 6084 m9 figshare c 2134359 to quantify element cycling through the earth and to assess the impact of humanity on these cycles requires precise knowledge of natural fluxes volcanoes represent a direct pathway from the earth s interior to the atmosphere hydrosphere and crust and are an important component of this natural flux they act as point sources with emissions ranging from persistent passive emissions in degassing and outflow of magmatic hydrothermal waters to punctuated release of material during periods of eruption the comprehensive datasets necessary to quantify the output of a volcano are only available for a limited number of terrestrial volcanic centres when estimating global terrestrial volcanic gaseous emissions e g hinkley et al 1999 allard et al 2000 the flux of a single volcano or a small compilation of volcanoes is therefore scaled to a component for which the global volcanic flux is known commonly so2 however this assumes that these emitters are representative of average global volcanism quantification of global volcanic element fluxes has focused on the largest emitters such as etna e g gauthier le cloarec 1998 aiuppa et al 2008 and kilauea hinkley et al 1999 mather et al 2012 with almost no information available for the far more common minor from ohba t capaccioni b caudron c eds geochemistry and geophysics of active volcanic lakes geological society london special publications 437 http doi org 10 1144 sp437 2 2015 the author s published by the geological society of london all rights reserved for permissions http www geolsoc org uk permissions publishing disclaimer www geolsoc org uk pub ethics at simon fraser university on january 18 2016 http sp lyellcollection org downloaded from

global pc5 geomagnetic pulsations of march 24 1991 as observed along the american sector analysis of the globally coherent pc5 geomagnetic pulsation event of march 24 1991 from a chain of stations extending from the auroral oval to the equatorial region along the american sector has shown unequivocal evidence on the enhancement of pulsation amplitude in the narrow equatorial band centered at the dip equator the fine spatial structure of this equatorial enhancement documented observationally for the first time emphasizes the importance of an ionospheric component associated with enhanced cowling conductivity the presence of an ionospheric component is also indicated at mid latitudes by the sharp increase in the amplitude of pulsations more dominantly in the y than in the x component on the sunward side of the dawn terminator the sunrise effect also causes a reversal of the sense of rotation of the wave polarization across the dawn terminator propagation of the magnetospheric inducted polar electric field to low and equatorial latitudes through the ionosphere is invoked to account for the equatorial enhancement and the sunrise effect seen in these pc5 pulsations

the 2005 catastrophic acid crater lake drainage lahar and acidic aerosol formation at mount chiginagak volcano alaska usa field observations and preliminary water and vegetation chemistry results 1 a mass of snow and ice 400 m wide and 105 m thick began melting in the summit crater of mount chiginagak volcano sometime between november 2004 and early may 2005 presumably owing to increased heat flux from the hydrothermal system or possibly from magma intrusion and degassing in early may 2005 an estimated 3 8 106 m3 of sulfurous clay rich debris and acidic water with an accompanying acidic aerosol component exited the crater through a tunnel at the base of a glacier that breaches the south crater rim over 27 km downstream the acidic waters of the flood inundated an important salmon spawning drainage acidifying mother goose lake from surface to depth approximately 0 5 km3 in volume at a ph of 2 9 to 3 1 killing all aquatic life and preventing the annual salmon run over 2 months later crater lake water sampled 8 km downstream of the outlet after considerable dilution from glacial meltwater was a weak sulfuric acid solution ph 3 2 so4 504 mg l cl 53 6 mg l and f 7 92 mg l the acid flood waters caused severe vegetation damage including plant death and leaf kill along the flood path the crater lake drainage was accompanied by an ambioructic flow of acidic aerosols that followed the flood path contributing to defoliation and necrotic leaf damage to vegetation in a 29 km2 area along and above affected streams in areas to heights of over 150 m above stream level moss species killed in the event contained high levels of sulfur indicating extremely elevated atmospheric sulfur content the most abundant airborne phytotoxic constituent was likely sulfuric acid aerosols that were generated during the catastrophic partial crater lake drainage event two mechanisms of acidic aerosol formation are proposed 1 generation of aerosol mist through turbulent flow of acidic water and 2 catastrophic gas exsolution this previously undocumented phenomenon of simultaneous vegetation damaging acidic aerosols accompanying drainage of an acidic crater lake has important implications for the study of hazards associated with active volcanic crater lakes

the volcanic acidification of glacial lake caviahue province of neuquen argentina abstract lake caviahue northern patagonia argentina is a large glacial lake acidified by volcanic fluids from copahue volcano the lake and the feeding rivers were sampled annually from 1997 till early 2006 including the eruptive period of 2000 lake caviahue waters evolved over time with the most concentrated waters in 2000 during the eruptive period followed by gradual dilution that was interrupted by renewed acidification in 2003 2004 inversion of the lake water data and application of a dynamic non steady state model for the lake provides our best quantitative estimates for the variation in element fluxes over the 9 year period the model flux results agree well with most of the measured fluxes the copahue hydrothermal system had gently declining element fluxes between 1997 and mid 1999 although the lake was still becoming more concentrated about 2 3 months before the 2000 eruption element fluxes increased strongly but the hydrothermal fluxes almost shutoff directly after the main eruptive events the fluxes of several elements recovered post 2001 with an increase in element fluxes in 2003 2004 the lake became more dilute between 2004 and 2006 the intrusion of new magma into the hydrothermal system just prior to the 2000 eruption led to enhanced water rock interaction with higher concentrations of the rock forming elements in the fluids and the hot spring flow rate increased as a result of the higher pressure in the reservoir the fluids became saturated in alunite and jarosite and they were already saturated with anhydrite precipitation of these minerals possibly led to a decreased permeability of the hydrothermal reservoir leading to the strongly reduced element fluxes just after the eruption in addition k al and s were retained in the newly precipitated minerals as well further diminishing their export the acidification in 2003 2004 may have resulted from a new small intrusion of magma or resulted from seismic activity that created new permeability and fresh rock surfaces for water rock interaction the volcano is a significant source of toxic trace elements such as f as b and li as well as a nutrient p for the local watershed monitoring of the hydrothermal fluids in the river that drains copahue especially the s cl mg cl and mg k values as well as the magnitude of the element fluxes would provide the best information for eruption forecasting for this volcano

investigating the scale adaptivity of a size filtered mass flux parameterization in the gray zone of shallow cumulus convection abstractin this study the scale adaptivity of a new parameterization scheme for shallow cumulus clouds in the gray zone is investigated the eddy diffusivity multiple mass flux ed mf n scheme is

posteruption chemical evolution of a volcanic caldera lake karymsky lake kamchatka 1 the 1996 short lived subaqueous eruption at the karymsky caldera lake suddenly changed the composition of the lake water the lake with a surface area of 10 km2 and a volume of 0 5 km3 became acidic increased its salinity to 1000 mg kg and became dominated by so42 and ca2 since the eruption the lake chemistry has evolved in a predictable manner described by simple box model as a result of dilution by incoming so4 ca mg poor water so4 ca and mg concentrations follow a simple exponential decrease with a characteristic time close to the residence time of the lake na k and cl decrease relatively significantly slower indicating a continuing input of these constituents into the lake that was initiated during the eruption thus the dynamics of two groups of lake water solutes can be predicted by a simple box model for water and solute mass balance

geochemistry of the magmatic hydrothermal system of kawah ijen volcano east java indonesia samples from kawah ijen crater lake spring and fumarole discharges were collected between 1990 and 1996 for chemical and isotopic analysis an extremely low ph 0 3 lake contains so 4 cl waters produced during absorption of magmatic volatiles into shallow ground water the acidic waters dissolve the rock isochemically to produce immature solutions the strong d and 18 o enrichment of the lake is mainly due to enhanced evaporation at elevated temperature but involvement of a magmatic component with heavy isotopic ratios also modifies the lake d and 18 o content the large so4 s d 23 8 26 4 measured in the lake suggest that dissolved so 4 forms during disproportionation of magmatic so 2 in the hydrothermal conduit at temperatures of 250 280 c the lake 18 o so4 and 18 o h2o values may reflect equilibration during subsurface circulation of the water at temperatures near 150 c significant variations in the lake s bulk composition from 1990 to 1996 were not detected however we interpret a change in the distribution and concentration of polythionate species in 1996 as a result of increased so 2 rich gas input to the lake system thermal springs at kawah ijen consist of acidic so 4 cl waters on the lakeshore and neutral ph hco 3 so 4 cl na waters in blawan village 17 km from the crater the cation contents of these discharges are diluted compared to the crater lake but still do not represent equilibrium with the rock the so 4 cl ratios and water and sulfur isotopic compositions support the idea that these springs are mixtures of summit acidic so 4 cl water and ground water the lakeshore fumarole discharges t 170 245 c have both a magmatic and a hydrothermal component and are supersaturated with respect to elemental sulfur the apparent equilibrium temperature of the gas is 260 c the proportions of the oxidized so 2 dominated magmatic vapor anti of the reduced h 2 s dominated hydrothermal vapor in the fumaroles varied between 1979 and 1996 this may be the result of interaction of so 2 bearing magmatic vapors with the summit acidic hydrothermal reservoir this idea is supported by the lower h 2 s so 2 ratio deduced for the gas producing the so 4 cl reservoir feeding the lake compared with that observed in the subaerial gas discharges the condensing gas may have equilibrated in a liquid vapor zone at about 350 c elemental sulfur occurs in the crater lake environment as banded sediments exposed on the lakeshore and as a subaqueous molten body on the crater floor the sediments were precipitated in the past during inorganic oxidation of h 2 s in the lake water this process was not continuous but was interrupted by periods of massive silica poorly crystallized precipitation similar to the present day lake conditions we suggest that the factor controlling the type of deposition is related to whether h 2 s or silica rich volcanic discharges enter the lake this could depend on the efficiency with which the lake water circulates in the hydrothermal cell beneath the crater quenched liquid sulfur products show 34 s values similar to those found in the banded deposits suggesting that the subaqueous molten body simply consists of melted sediments previously accumulated at the lake bottom

a scale adaptive turbulent kinetic energy closure for the dry convective boundary layer abstracta pragmatic scale adaptive turbulent kinetic energy tke closure is proposed to simulate the dry convective boundary layer for a variety of horizontal grid resolutions from 50 m typical of large eddy simulation models that use three dimensional turbulence parameterizations closures up to 100 km typical of climate models that use one dimensional turbulence and convection parameterizations closures since parameterizations closures using the tke approach have been frequently used in these two asymptotic limits a simple method is proposed to merge them with a mixing length scale formulation for intermediate resolutions this new scale adaptive mixing length naturally increases with increasing grid length until it saturates as the grid length reaches mesoscale model resolution the results obtained using this new approach for dry convective boundary layers are promising the mean vertical profiles of potential temperature and heat flux remain in good agreement for different resolutions a contin

surveillance of ruapehu crater lake new zealand by aqueous polythionates abstract aqueous sulfur speciation of samples of crater lake water from crater lake collected at mt ruapehu new zealand since 1968 has been determined using high performance liquid chromatography polythionates s x o 6 2 are produced in the lake through reactions between sulfur dioxide and hydrogen sulfide gases from the subaqueous fumaroles their concentrations vary from 0 to a few hundred mg l corresponding to the activity of the volcano the concentration of the total polythionates s x o 6 2 s 4 o 6 2 s 5 o 6 2 s 6 o 6 2 is found to be a good indicator of changes in the subaqueous fumarolic activity at crater lake the molar s x o 6 2 cl ratios of the lake water can be used to divide the volcanic activity of crater lake into four stages 1 stage i period of weak volcanic activity with no hydrothermal explosions this stage is characterized by low total s x o 6 2 with a distribution order of s 5 o 6 2 s 4 o 6 2 s 6 o 6 2 h 2 s is predominant among dissolved gases in the lake water 2 stage iia quiescent period with minor hydrothermal explosions the lake water contains high s x o 6 2 with a distribution order of s 5 o 6 2 s 4 o 6 2 s 6 o 6 2 dissolved h 2 s and so 2 gases are very low 3 stage iib increased fumarolic activity with frequent hydrothermal explosions low s x o 6 2 with a distribution order of s 4 o 6 2 s 5 o 6 2 s 6 o 6 2 sulfur dioxide but no h 2 s is detected in the water 4 stage iii period of phreatomagmatic eruptions with lahars and intensive seismic activity no s x o 6 2 exists but dissolved so 2 is high in the lake water the moderate sized explosion of december 8 1988 which was not preceded by any changes in lake water polythionate chemistry or seismic activity is hypothesized to be a vent cleaning eruption caused by blockage of ascending magmatic gases that was caused by solidification of a molten sulfur pool at the bottom of crater lake

tracing thermal aquifers of el chichon volcano hydrothermal system mexico with 87sr 86sr ca sr and ree abstract the volcano hydrothermal system of el chichon volcano chiapas mexico is characterized by numerous thermal manifestations including an acid lake steam vents and boiling springs in the crater and acid and neutral hot springs and steaming ground on the flanks previous research on major element chemistry reveals that thermal waters of el chichon can be divided in two groups 1 neutral waters discharging in the crater and southern slopes of the volcano with chloride content ranging from 1500 to 2200 mg l and 2 acid to neutral waters with cl up to 12 000 mg l discharging at the western slopes our work supports the concept that each group of waters is derived from a separate aquifer aq 1 and aq 2 in this study we apply sr isotopes ca sr ratios and ree abundances along with the major and trace element water chemistry in order to discriminate and characterize these two aquifers waters derived from aq 1 are characterized by 87 sr 86 sr ratios ranging from 0 70407 to 0 70419 while sr concentrations range from 0 1 to 4 mg l and ca sr weight ratios from 90 to 180 close to average values for the erupted rocks waters derived from aq 2 have 87 sr 86 sr between 0 70531 and 0 70542 high sr concentrations up to 80 mg l and ca sr ratio of 17 28 aquifer 1 is most probably shallow composed of volcanic rocks and situated beneath the crater within the volcano edifice aquifer 2 may be situated at greater depth in sedimentary rocks and by some way connected to the regional oil gas field brines the relative water output l s from both aquifers can be estimated as aq 1 aq 2 30 both aquifers are not distinguishable by their ree patterns the total concentration of ree however strongly depends on the acidity all neutral waters including high salinity waters from aq 2 have very low total ree concentrations 4 ground waters draining fresh and old pyroclastic deposits rich in magmatic anhydrite it is suggested that the main mechanism controlling the concentration of ree in waters of el chichon is the acidity as low ph results from the shallow oxidation of h 2 s contained in hydrothermal vapors ree distribution in thermal waters reflects the dissolution of volcanic rocks close to the surface or lake sediments as is the case for the crater lake

investigating crater lake warming using aster thermal imagery case studies at ruapehu poas kawah ijen and copahue volcanoes abstract a two channel or split window algorithm designed to correct for atmospheric conditions was applied to thermal images taken by the advanced spaceborne thermal emission and reflection radiometer aster of lake yugama on kusatsu shirane volcano in japan in order to measure the temperature of its crater lake these temperature calculations were validated using lake water temperatures that were collected on the ground overall the agreement between the temperatures calculated using the split window method and ground truth is quite good typically 1 5 c for cloud free images data from fieldwork undertaken in the summer of 2004 at kusatsu shirane allow a comparison of ground truth data with the radiant temperatures measured using aster imagery further images were analyzed of ruapehu poas kawah ijen and copahue volcanoes to acquire time series of lake temperatures a total of 64 images of these 4 volcanoes covering a wide range of geographical locations and climates were analyzed results of the split window algorithm applied to aster images are reliable for monitoring thermal changes in active volcanic lakes these temperature data when considered in conjunction with traditional volcano monitoring techniques lead to a better understanding of whether and how thermal changes in crater lakes aid in eruption forecasting

methanogenesis in the sediment of the acidic lake caviahue in argentina the biogeochemistry of methane in the sediments of lake caviahue was examined by geochemical analysis microbial activity assays and isotopic analysis the ph in the water column was 2 6 and increased up to a ph of 6 in the deeper sediment pore waters the carbon isotope composition ofch 4 was between 65 and 70 which is indicative for the biological origin of the methane the enrichment factor e increased from 46 o in the upper sediment column to more than 80 in the deeper sediment section suggesting a transition from acetoclastic methanogenesis to co 2 reduction with depth in the most acidic surface layer of the sediment ph 4 methanogenesis is inhibited as suggested by a linear ch 4 concentration profile activity assays and mpn analysis the ch 4 activity assays and the ch 4 profile indicate that methanogenesis in the sediment of lake caviahue was active below 40 cm depth at that depth the ph was above 4 and sulfate reduction was sulfate limited methane was diffusing with a flux of 0 9 mmol m 2 d 1 to the sediment surface where it was probably oxidized methanogenesis contributed little to the sediments carbon budget and had no significant impact on lake water quality the high biomass content of the sediment which was probably caused by the last eruption ofcopahue volcano supported high rates of sulfate reduction which probably raised the ph and created favorable conditions for methanogens in deeper sediment layers

monitoring of jokulhlaups and element fluxes in proglacial icelandic rivers using osmotic samplers the quantification of volatile emissions from volcanoes is an integral part of understanding magmatic systems with the exsolution and extent of volcanic degassing having a large impact on the nature of an eruption measurements of volatiles have traditionally focused on gas emissions into the atmosphere but volatiles can also become dissolved in proximal water bodies en route to the surface thus the monitoring of rivers draining active volcanic areas can provide insights to identifying changes in activity this process is particularly important for sub glacial volcanoes in iceland where much of the volatile release is transported within glacial outbreak floods termed jokulhlaups monitoring and characterising these phenomena is hampered by the dependence on spot sampling of stochastic events under challenging field conditions which often leads to bias in the collected data a recent technological advance is the osmotic sampler an electricity free pump that continuously collects water that can subsequently be divided into time averaged samples this technique allows for continued and unsupervised deployment of a sampler for weeks to months representing a cost efficient form of chemical monitoring in this study we deployed osmotic samplers in two rivers in southern iceland skalm is a proglacial river from m rdalsjokull glacier and katla volcano while skafta is a larger drainage system from the western part of vatnajokull glacier both rivers are prone to jokulhlaups from geothermal and volcanic sources and a small jokulhlaup of geothermal origin occurred during the second deployment in skafta in january 2014 the two deployments show that osmotic samplers are capable of delivering accurate chemical data in turbulent conditions for several key elements total dissolved fluxes for the deployment at skafta are calculated to be na 9 9 tonnes day mg 10 5 t d si 34 7 t d cl 11 0 t d ca 31 6 t d dic 50 8 t d and so4 28 3 t d with significant elevations of element concentrations during the jokulhlaup dissolved fluxes vary considerably on temporal scales from days to seasons so that spot sampling may miss pulses in concentrations this is particularly important for elements such as mn the continuous geochemical records from the osmotic samplers make it possible to identify pulses of fluxes attributed to sea spray groundwater and subglacial sources the samplers can also be combined with existing methods of river monitoring such as conductivity and discharge to accurately assess changes to fluvial chemistry due to volcanic inputs moreover there is the potential to deploy osmotic samplers in a range of other affected water bodies e g wells springs lakes to gain further insights into volcanic processes

a grid refinement based approach for modeling the convective boundary layer in the gray zone algorithm implementation and testing abstracta grid refinement based method is implemented in a community atmospheric model to improve the representation of convective boundary layer cbl turbulence on gray zone i e o 1 km grids at this resolution cbl convection is partially resolved and partially subgrid scale sgs such that neither traditional mesoscale planetary boundary layer pbl schemes nor sgs closures for large eddy simulations less are appropriate the proposed method utilizes two way interactive nesting to refine the horizontal resolution of the unstable surface layer of the daytime cbl sgs turbulent mixing in the fine nest and coarse parent grids are parameterized by an les turbulence closure and a pbl scheme respectively the method does not rely on predetermined empirical functions to introduce grid scale dependency and in theory works with any pbl scheme compared to the stand alone gray zone simulation the proposed approach shows improvements in terms of higher order statistics the timing of the onset of re

geochemistry of the acid kawah putih lake patuha volcano west java indonesia abstract kawah putih is a summit crater of patuha volcano west java indonesia which contains a shallow 300 m wide lake with strongly mineralized acid sulfate chloride water the lake water has a temperature of 26 34 c ph s tot 2500 4600 ppm and cl 5300 12 600 ppm and floating sulfur globules with sulfide inclusions are common sulfur oxyanion concentrations are unusually high with s 4 o 6 2 s 5 o 6 2 s 6 o 6 2 2400 4200 ppm subaerial fumaroles thermodynamic modeling of the lake fluids indicates that the lake water is saturated with silica phases barite pyrite and various pb sb cu as bi bearing sulfides when sulfur saturation is assumed precipitating phases predicted by the model calculations are consistent with the bulk chemistry of the sulfur rich bottom sediments and their identified mineral phases much of the lake water chemistry can be explained by congruent rock dissolution in combination with preferential enrichments from entering fumarolic gases or brines and element removal by precipitating mineral phases as indicated by a comparison of the fluids volcanic rocks and lake bed sediment flank springs on the mountain at different elevations vary in composition and are consistent with local rock dissolution as a dominant factor and ph dependent element mobility discharges of warm sulfate and chloride rich water at the highest elevation and a near neutral spring at lower level may contain a small contribution of crater lake water the acid fluid induced processes at patuha have led to the accumulation of elements that are commonly associated with volcano hosted epithermal ore deposits the dispersal of heavy metals and other potentially toxic elements from the volcano via the local drainage system is a matter of serious environmental concern

electrodynamic coupling of high and low latitudes observations on may 27 1993 the penetration of disturbance electric fields from the polar region to the magnetic equator on the dayside of the earth is examined with geomagnetic data on may 27 1993 first we examine a dayside equatorial disturbance that followed the rapid recovery of magnetic activity from a storm and that has the characteristics of overshielding caused by persistent region 2 field aligned currents it lasted 0 3 hours second we analyze a series of fluctuations with periods of 25 75 min to determine the variations of amplitude and phase with magnetic latitude and magnetic local time the fluctuations were highly coherent at all latitudes between the magnetic equator and the auroral zone but the coherency decreasedin the polar cap a northward fluctuation at the equator during midday hours accompanied auroral zone fluctuations that were southward before noon eastward around noon and northward after noon the amplitudes decreased away from the auroral zone toward midlatitudes but were amplified under the equatorial electrojet no detectablep hased ifferencesa re found indicating that any temporal lags which might be inducedb y persistencein the region 2f ield alignedc urrentsa re less than i min for fluctuations having periods like those examined here a synoptic inversion analysis of the high latitude magnetic data to estimate the time varying high latitude electric potential patterns shows that fluctuations of the high latitude east west potential gradient tended to be concentrated around midday where they were in phase with fluctuations in the midday east west potential gradient at the magnetic equator

gas buildup in lake nyos cameroon the recharge process and its consequences the gases dissolved in lake nyos cameroon were quantified recently december 1989 and september 1990 by two independent techniques in situ measurements using a newly designed probe and laboratory analyses of samples collected in pre evacuated stainless steel cylinders the highest concentrations of co2 and ch4 were 0 30 mol kg and 1 7 mmol kg respectively measured in cylinders collected 1 m above lake bottom probe measurements of in situ gas pressure at three different stations showed that horizontal variations in total dissolved gas were negligible total dissolved gas pressure near the lake bottom is 1 06 mpa 10 5 atm 50 as high as the hydrostatic pressure of 2 1 mpa 21 atm comparing the co2 profile constructed from the 1990 data to one obtained in may 1987 shows that co2 concentrations have increased at depths to below 150 m based on these profiles the average rate of co2 input to bottom waters was 2 6 108 mol a increased deep water temperatures require an average heat flow of 0 32 mw into the hypolimnion over the same time period the transport rates of co2 heat and major ions into the hypolimnion suggest that a low temperature reservoir of free co2 exists a short distance below lake bottom and that convective cycling of lake water through the sediments is involved in transporting the co2 into the lake from the underlying diatreme increased ch4 concentrations at all depths below the oxycline and a high14c content 41 modern in the ch4 4 m above lake bottom show that much of the ch4 is biologically produced within the lake the ch4 production rate may vary with time but if the co2 recharge rate remains constant co2 saturation of the entire hypolimnion below 50 m depth would require 140a given present day concentrations

global electrodynamics observed during the initial and main phases of the july 1991 magnetic storm data acquired by seven fortuitously positioned satellites in the interplanetary medium the magnetosphere and the topside ionosphere as well as from numerous ground magnetometers have allowed us to follow the evolution of global currents and electric fields during the geomagnetic storm on july 8 9 1991 an interplanetary disturbance collided with the magnetosphere at 1636 ut on july 8th compressing the magnetopause inside of geostationary orbit for about 3 hours as observed by magnetometers on two goes satellites the resulting storm developed in four segments with a 7 hour lull separating the initial and main phases the initial phase was characterized by 1 an extensive dp 2 current system that produced an ae perturbation of 3500 nt with reporting stations on the dayside 2 a twenty fold increase in auroral electron fluxes and 3 the immediate appearance of electric fields in the inner magnetosphere the main phase intensification and earthward movement of the ring current are associated with southward turnings of the interplanetary magnetic field imf and a polar cap potential increase above 200 kv a significant fraction of the ring current growth was observed prior to the first of several substorms that occurred during the main and recovery phases the beginning of recovery was characterized by a diminution of the southward imf component the cross polar cap potential and magnetospheric electric fields it was also marked by a substorm onset considering the timing of dst modulations relative to substorm occurrence we conclude that during this magnetic storm the electric fields responsible for ring current transport energization were mostly associated with the dp 2 current system finally in the evening sector penetration electric fields of the initial and main phases led to the formation of upward moving equatorial plasma bubbles that were detected by two dmsp satellites in the topside ionosphere

convectively induced secondary circulations in fine grid mesoscale numerical weather prediction models abstractmesoscale numerical weather prediction models using fine grid o 1 km meshes for weather forecasting environmental assessment and other applications capture aspects of larger than grid mesh size convectively induced secondary circulations ciscs such as cells and rolls that occur in the convective planetary boundary layer pbl however 1 km grid spacing is too large for the simulation of the interaction of ciscs with smaller scale turbulence the existence of ciscs also violates the neglect of horizontal gradients of turbulent quantities in current pbl schemes both aspects poorly resolved ciscs and a violation of the assumptions behind pbl schemes are examples of what occurs in wyngaard s terra incognita where horizontal grid spacing is comparable to the scale of the simulated motions thus model ciscs m ciscs cannot be simulated reliably this paper describes how the superadiabatic layer in the lower convective pbl together with increased horizontal resolution allow the critical ra

a statistical study of the response of the dayside equatorial f2 layer to the main phase of intense geomagnetic storms as an indicator of penetration electric field 1 the response of the dayside equatorial f2 layer to the main phases of the 22 intense geomagnetic storms dst 150 nt in 1998 2008 is investigated using the digital ionosonde data from the equatorial stations in brazilian indian and australian longitudes together with equatorial electrojet strength and imf bz the storms include 15 superstorms dst 200 nt the observations show that there is a period during all mps when the f2 layer peak rises and falls rapidly with large peak electron density nmax reduction the rise velocity strongly correlates with the intensity dst of the storms and the duration of the nmax reduction corresponds to that of strong eastward electrojet when imf bz remains highly negative the observations indicate the occurrence of strong eastward prompt penetration electric fields ppef during the rapid f2 layer response the ppef drives the f2 layer peak rapidly upward which reduces nmax due to vertical expansion and diffusion the results therefore suggest that the rapid f2 layer response rapid rise and fall of peak height hmax with large nmax reduction observed by ionosondes can be used to detect the occurrence of the daytime eastward ppef during intense geomagnetic storms irrespective of season and level of solar activity the data also show two rare events of strong daytime westward electric fields due to disturbance dynamo and or prompt penetration the results are important when radars are not available to monitor the occurrence of the ppef

nighttime turbulent events in a steep valley a nested large eddy simulation study this numerical study investigates the nighttime flow dynamics in owens valley california nested highresolution large eddy simulation les is used to resolve stable boundary layer flows within the valley on 17 april during the 2006 terrain induced rotor experiment the valley atmosphere experiences weak synoptic forcings and is largely dominated by buoyancy driven downslope and down valley flows tower instruments on the valley floor record a continuous decrease in temperature after sunset except for a brief warming episode this transient warming event is modeled with good magnitude and temporal precision with les analysis of the les flow field confirms the event to be the result of a slope to valley flow transition as previously suggested by researchers based on field observations on the same night a northerly cold airflow from the great basin is channeled through a pass on the eastern valley sidewall the current plunges into the stable valley atmosphere overshooting the altitude of its neutral buoyancy and generating a large scale oscillatory motion the resulting cross valley flow creates strong vertical shear with the down valley flow in the lower layers of the atmosphere a portion of the cross valley flow is captured by a scanning lidar the nested les is in good agreement with the lidar recorded radial velocity furthermore the les is able to resolve kelvin helmholtz waves and ejection and sweep events at the two layer interface which lead to topdown vertical mixing

role of imf b y in the prompt electric field disturbances over equatorial ionosphere during a space weather event on 7 january 2005 a p 40 prompt penetration electric field perturbations of opposite polarities were observed over thumba and jicamarca on a few occasions during 13 45 16 30 ut however the electric field was found to be eastward during 14 45 15 30 ut over both thumba and jicamarca contrary to the general expectation wherein opposite polarities are expected at nearly antipodal points on closer scrutiny three important observational features are noticed during 14 10 15 15 ut first during 14 10 14 45 ut despite increasing southward interplanetary magnetic field imf b z condition the already westward electric field over thumba weakened less westward while the eastward electric field over jicamarca intensified more eastward second the electric field not only became anomalously eastward over thumba but also got intensified further during 14 45 15 00 ut similar to jicamarca third during 15 00 15 15 ut despite imf b z remaining steadily southward the eastward electric field continued to intensify over thumba but weakened over jicamarca it is suggested that the changes in imf b y component under southward imf b z condition are responsible for skewing the ionospheric equipotential patterns over the dip equator in such a way that thumba came into the same dp2 cell as that of jicamarca leading to anomalous electric field variations magnetic field measurements along the indian and jicamarca longitude sectors and changes in high latitude ionospheric convection patterns provide credence to this proposition thus the present investigation shows that the variations in imf b y are fundamentally important to understand the prompt penetration effects over low latitudes

a physical mechanism of positive ionospheric storms at low latitudes and midlatitudes 1 a physical mechanism of the positive ionospheric storms at low latitudes and midlatitudes is presented through multi instrument observations theoretical modeling and basic principles according to the mechanism an equatorward neutral wind is required to produce positive ionospheric storms the mechanical effects of the wind 1 reduce or stop the downward diffusion of plasma along the geomagnetic field lines 2 raise the ionosphere to high altitudes of reduced chemical loss and hence 3 accumulate the plasma at altitudes near and above the ionospheric peak centered at around 30 magnetic latitudes daytime eastward prompt penetration electric field ppef if it occurs also shifts the equatorial ionization anomaly crests to higher than normal latitudes up to approximately 30 latitudes the positive ionospheric storms are most likely in the longitudes where the onset of the geomagnetic storms falls in the ionization production dominated morning noon local time sector when the plasma accumulation due to the mechanical effects of the wind largely exceeds the plasma loss due to the chemical effect of the wind the mechanism agrees with the multi instrument observations made during the supergeomagnetic storm of 7 8 november 2004 with 18 h long initial phase ip and 10 h long main phase mp the observations which are mainly in the japanese australian longitudes where the mp onset was in the morning 0600 lt 2100 ut show 1 strong positive ionospheric storms in ne nmax hmax global positioning system total electron content gps tec and 630 nm airglow intensity in both northern and southern hemispheres started at the morning 0600 lt mp onset and lasted for a day 2 repeated occurrence of strong eastward ppef events penetrated after the mp onset and superposed with westward electric field started before the mp onset and 3 storm time equatorward neutral winds inferred from 1 and 2 repeated occurrence of an unusually strong f3 layer with large density depletions around the equator was also observed during the morning noon mp

volcanic lake systematics ii chemical constraints abstract a database of 373 lake water analyses from the published literature was compiled and used to explore the geochemical systematics of volcanic lakes binary correlations and principal component analysis indicate strong internal coherence among most chemical parameters compositional variations are influenced by the flux of magmatic volatiles and or deep hydrothermal fluids the chemistry of the fluid entering a lake may be dominated by a high temperature volcanic gas component or by a lower temperature fluid that has interacted extensively with volcanic rocks precipitation of minerals like gypsum and silica can strongly affect the concentrations of ca and si in some lakes a much less concentrated geothermal input fluid provides the mineralized components of some more dilute lakes temporal variations in dilution and evaporation rates ultimately control absolute concentrations of dissolved constituents but not conservative element ratios most volcanic lake waters and presumably their deep hydrothermal fluid inputs classify as immature acid fluids that have not equilibrated with common secondary silicates such as clays or zeolites many such fluids may have equilibrated with secondary minerals earlier in their history but were re acidified by mixing with fresh volcanic fluids we use the concept of degree of neutralization as a new parameter to characterize these acid fluids this leads to a classification of gas dominated versus rock dominated lake waters a further classification is based on a cluster analysis and a hydrothermal speedometer concept which uses the degree of silica equilibration of a fluid during cooling and dilution to evaluate the rate of fluid equilibration in volcano hydrothermal systems

chemical evolution and volcanic activity of the active crater lake of poas volcano costa rica 1993 1997 abstract concentrations of chloride and sulfate and ph in the hot crater lake laguna caliente at poas volcano and in acid rain varied over the period 1993 1997 these parameters are related to changes in lake volume and temperature and changes in summit seismicity and fumarole activity beneath the active crater during this period lake level increased from near zero to its highest level since 1953 lake temperature declined from a maximum value of 70 c to a minimum value of 25 c and ph of the lake water increased from near zero to 1 8 in may 1993 when the lake was nearly dry chloride and sulfate concentrations in the lake water reached 85 400 and 91 000 mg l 1 respectively minimum concentrations of chloride and sulfate after the lake refilled to its maximum volume were 2630 and 4060 mg l 1 respectively between january 1993 and may 1995 most fumarolic activity was focused through the bottom of the lake after may 1995 fumarolic discharge through the bottom of the lake declined and reappeared outside the lake within the main crater area the appearance of new fumaroles on the composite pyroclastic cone coincided with a dramatic decrease in type b seismicity after january 1996 between may 1995 and december 1997 enhanced periods of type a seismicity and episodes of harmonic tremor were associated with an increase in the number of fumaroles and the intensity of degassing on the composite pyroclastic cone adjacent to the crater lake increases in summit seismic activity type a b and harmonic tremor and in the height of eruption plumes through the lake bottom are associated with a period of enhanced volcanic activity during april september 1994 at this time visual observations and remote fumarole temperature measurements suggest an increase in the flux of heat and gases discharged through the bottom of the crater lake possibly related to renewed magma ascent beneath the active crater a similar period of enhanced seismic activity that occurred between august 1995 and january 1996 apparently caused fracturing of sealed fumarole conduits beneath the composite pyroclastic cone allowing the focus of fumarolic degassing to migrate from beneath the lake back to the 1953 1955 cone changes in the chemistry of summit acid rain are correlated changes in volcanic activity regardless of whether fumaroles are discharging into the lake or are discharging directly into the atmosphere

intense magmatic degassing through the lake of copahue volcano 2013 2014 here we report on the first assessment of volatile fluxes from the hyperacid crater lake hosted within the summit crater of copahue a very active volcano on the argentina chile border our observations were performed using a variety of in situ and remote sensing techniques during field campaigns in march 2013 when the crater hosted an active fumarole field and in march 2014 when an acidic volcanic lake covered the fumarole field in the latter campaign we found that 566 to 1373 t d 1 of so2 were being emitted from the lake in a plume that appeared largely invisible this combined with our derived bulk plume composition was converted into flux of other volcanic species h2o 10989 t d 1 co2 638 t d 1 hcl 66 t d 1 h2 3 3 t d 1 and hbr 0 05 t d 1 these levels of degassing comparable to those seen at many open vent degassing arc volcanoes were surprisingly high for a volcano hosting a crater lake copahue s unusual degassing regime was also confirmed by the chemical composition of the plume that although issuing from a hot 65 c lake preserves a close to magmatic signature eq3 6 models of gas water rock interaction in the lake were able to match observed compositions and demonstrated that magmatic gases emitted to the atmosphere were virtually unaffected by scrubbing of soluble s and cl species finally the derived large h2o flux 10 988 t d 1 suggested a mechanism in which magmatic gas stripping drove enhanced lake water evaporation a process likely common to many degassing volcanic lakes worldwide

gas geochemistry of the magmatic hydrothermal fluid reservoir in the copahue caviahue volcanic complex argentina abstract copahue volcano is part of the caviahue copahue volcanic complex ccvc which is located in the southwestern sector of the caviahue volcano tectonic depression argentina chile this depression is a pull apart basin accommodating stresses between the southern liquine ofqui strike slip and the northern copahue antinir compressive fault systems in a back arc setting with respect to the southern andean volcanic zone in this study we present chemical inorganic and organic and isotope compositions 13c co2 15n 3he 4he 40ar 36ar 13c ch4 d ch4 and d h2o and 18o h2o of fumaroles and bubbling gases of thermal springs located at the foot of copahue volcano sampled in 2006 2007 and 2012 helium isotope ratios the highest observed for a southern american volcano r ra up to 7 94 indicate a non classic arc like setting but rather an extensional regime subdued to asthenospheric thinning 13c co2 values from 8 8 to 6 8 vs v pdb 15n values 5 3 to 5 5 vs air and co2 3he ratios from 1 4 to 8 8 109 suggest that the magmatic source is significantly affected by contamination of subducted sediments gases discharged from the northern sector of the ccvc show contribution of 3he poor fluids likely permeating through local fault systems despite the clear mantle isotope signature in the ccvc gases the acidic gas species have suffered scrubbing processes by a hydrothermal system mainly recharged by meteoric water gas geothermometry in the h2o co2 ch4 co h2 system suggests that co and h2 re equilibrate in a separated vapor phase at 200 220 c on the contrary rock fluid interactions controlling co2 ch4 production from sabatier reaction and c3h8 dehydrogenation seem to occur within the hydrothermal reservoir at temperatures ranging from 250 to 300 c fumarole gases sampled in 2006 2007 show relatively low n2 he and n2 ar ratios and high r ra values with respect to those measured in 2012 such compositional and isotope variations were likely related to injection of mafic magma that likely triggered the 2000 eruption therefore changes affecting the magmatic system had a delayed effect on the chemistry of the ccvc gases due to the presence of the hydrothermal reservoir however geochemical monitoring activities mainly focused on the behavior of inert gas compounds n2 and he should be increased to investigate the mechanism at the origin of the unrest started in 2011

fluid volcano interaction in an active stratovolcano the crater lake system of poas volcano costa rica rowe g l jr brantley s l fernandez m fernandez j f borgia a and barquero j 1992 fluid volcano interaction in an active stratovolcano the crater lake system of po is volcano costa rica j volcanol geotherm res 49 2351 seismic and geochemical data collected at po is volcano costa rica since 1978 suggest that temperature and chemical variations recorded in subaerial fumaroles and the crater lake are related to episodic release of heat and volatiles associated with hydrofracturing of the upper margin of the shallow magma body power outputs associated with these events approach 600 mw and are superimposed on a baseline energy flux of approximately 200 mw the baseline heat flux suggests a magma solidification rate of 0 012 km3 yr and background volatile release rates of 1000 t d h20 66 t d s 13 t d ci and 0 5 t d f these fluxes are comparable to fluxes of f c1 and s exiting the magmatic hydrothermal system through acidic flank springs and are about a factor of five less than estimated volatile fluxes through summit fumaroles during the high temperature event of 1981 1983 mass balance considerations suggest that heat released at the lake surface is primarily supplied by the ascent of heated brines supplemented by condensation of fumarolic steam calculated average seepage rates out of the lake 450 kg s indicate rapid convection of acidic lake brine through underlying lake sediments and pyroclastic deposits circulation of the extremely corrosive lake brine through the volcanoclastic material beneath the lake may enhance subsurface permeabilities fluxes of rock forming elements observed in the rio agrio basin on the northwest flank of po is suggest that dissolution and removal of volcano elastic material occurs at a rate of approximately 1650 m3 yr however estimated sulfur fluxes from the cooling magma body suggest that porosity created by this dissolution could quickly be filled by the deposition of native sulfur finally analysis of heat and water budgets for the crater lake over the period 1978 1989 indicates that the recent decline and disappearance of the lake was caused by variations in summit rainfall combined with an increase in subsurface heat flow to the lake in 1987 1988 the increase in heat flow is related to continued degassing of high temperature volatiles following a hydrofracturing magma ascent episode that occurred in 1986

global equatorial plasma bubble occurrence during the 2015 st patrick s day storm an analysis of the occurrence of equatorial plasma bubbles epbs around the world during the 2015 st patrick s day geomagnetic storm is presented a network of 12 global positioning system receivers spanning from south america to southeast asia was used in addition to colocated vhf receivers at three stations and four nearby ionosondes the suppression of postsunset epbs was observed across most longitudes over 2 days the epb observations were compared to calculations of the linear rayleigh taylor growth rate using coupled thermosphere ionosphere modeling which successfully modeled the transition of favorable epb growth from postsunset to postmidnight hours during the storm the mechanisms behind the growth of postmidnight epbs during this storm were investigated while the latter stages of postmidnight epb growth were found to be dominated by disturbance dynamo effects the initial stages of postmidnight epb growth close to local midnight were found to be controlled by the higher altitudes of the plasma i e the gravity term modeling and observations revealed that during the storm the ionospheric plasma was redistributed to higher altitudes in the low latitude region which made the plasma more susceptible to rayleigh taylor growth prior to the dominance of the disturbance dynamo in the eventual generation of postmidnight epbs

penetration of magnetospheric electric fields to the equator during a geomagnetic storm 1 penetration of the magnetospheric electric field to the equatorial ionosphere was examined for the geomagnetic storm on 6 november 2001 by analyzing the difference in magnitude of the geomagnetic storm recorded at the dayside geomagnetic equator yap 0 3 gml and low latitude okinawa 14 47 gml the penetrated electric field caused the dp2 currents at the equator i e eastward currents during the main phase of the storm while the overshielding currents i e westward currents dominated during the recovery phase it is shown that the ring current started to develop simultaneously with the onset of the equatorial dp2 within the temporal resolution of a few minutes these results imply prompt transmission of the dawn to dusk convection electric field to the inner magnetosphere as well as to the equatorial ionosphere it is found that the equatorial dp2 started to decrease one hour after the onset of the ring current development indicating shielding effects becoming effective at the equator during the latter half of the storm main phase the dp2 was then overwhelmed by the overshielding which resulted in the counter electrojet cej in the beginning of the storm recovery phase the image magnetometer chain data indicate that the westward auroral electrojet aej in the dawn sector was driven over midlatitude centered at 57 corrected geomagnetic latitude cgml during the main phase while the aej shifted rapidly poleward to the auroral latitude centered at 67 cgml in the beginning of the recovery phase the overshielding must be caused by the abrupt poleward shift of the rl facs as inferred from the poleward shift of the aej in addition to the decrease in their magnitude due to the decrease in magnitude of the southward imf the geomagnetic storm at the dayside geomagnetic equator was enhanced in amplitude with the ratio of 2 7 as compared with the geomagnetic storm at low latitude this amplification is a result of both effects of the dp2 currents and the cej associated with the main and recovery phases respectively it is suggested that the electric field associated with the dp2 currents contributed to the development of the ring current during the main phase while the overshielding electric field may contribute to cease developing the ring current during the recovery phase

downstream composition changes of acidic volcanic waters discharged into the banyupahit stream ijen caldera indonesia abstract the crater lake of kawah ijen volcano contains extremely low ph we discuss the downstream composition changes affecting the banyupahit waters by using stable isotope chemical and mineralogical data collected from sites along the stream length the saturation of the stream waters with respect to minerals was evaluated with solveq and wateq4f and compared with the geochemical observations an aluminous mineralogy alunogen pickeringite tamarugite and kalinite develops in the upper part of the banyupahit due to concentration of the headwaters by evaporation downstream attenuation of dissolved element concentrations results principally from dilution and from mineral precipitation the stream ph changes from 0 at the source to 4 close to the mouth the d and 18o values and the relative so4 cl f contents of the banyupahit waters indicate that the tributaries are mostly meteoric dissolved so4 in the acidic stream come only from the crater lake seepages and are not involved later in microbially mediated reactions as shown by their 34s and 18o values re equilibration of the stream so4 oxygen isotope composition with h2o from tributaries does not occur calcium sio2 al fe k and so4 behave non conservatively in the stream waters gypsum silica amorphous or poorly ordered a basic aluminum hydroxysulfate basaluminite k jarosite and amorphous ferric hydroxide may exert a solubility control on these elements along the entire stream length or in certain stream sections consistent with the thermochemical model results downstream concentration trends and mineral saturation levels suggest that precipitation of sr pb rich barite and celestite consume ba sr and pb whereas dissolved cu pb and zn may adsorb onto solid particles especially after the junctions of the acidic stream with non acidic rivers we calculated that significant fluxes of so4 f cl al sio2 ti mn and cu may reach the irrigation system possibly causing serious environmental impacts such as soil acidification and induration

the convective boundary layer in the terra incognita numerical simulations of a convective boundary layer cbl are performed to investigate model behavior in the terra incognita also known as the gray zone the terra incognita of the cbl refers to a range of model grid spacing that is comparable to the size of the most energetic convective eddies which are on the order of the boundary layer depth using the rayleigh benard thermal instability as reference a set of idealized simulationsisused toshow that grayzone modelingisnot onlya numericalchallenge but also poses dynamical difficulties when the grid spacing falls within the cbl gray zone grid dependent convection can occur the size of the initial instability structures is set by the grid spacing rather than the natural state of the flow this changes higher order flow statistics and poses fundamental difficulties for gray zone modeling applications

using crater lake chemistry to predict volcanic activity at poas volcano costa rica monitoring of crater lake chemistry during the recent decline and disappearance of the crater lake of poas volcano revealed that large variations in so4 cl f cl and mg cl ratios were caused by the enhanced release of hcl vapor from the lake surface due to increasing lake temperature and solution acidity variation in the concentration of polythionic acids h2sxo6 x 4 6 was the most reliable predictor of renewed phreatic eruptive activity at the volcano exhibiting sharp decreases three months prior to the initiation of phreatic eruptions in june 1987 polythionic acids may offer a direct indicator of changing subsurface magmatic activity whereas chloride based element ratios may be influenced by surface volatilization of hcl and subsequent recycling of acidic fluids in crater lake volcanoes

volcanic lake systematics i physical constraints volcanic lakes have a wide range of characteristics and we make an attempt to delineate the limiting physical conditions for several lake classes the ratio between heat input and heat dissipation capacity of a lake constrains the temperature for perfectly mixed steady state volcanic lakes poorly mixed lakes are also conditioned by this ratio but their temperature structure is also strongly influenced by the hydrodynamics resulting from different mechanisms of heat transfer the steady state temperatures of volcanic lakes are largely determined by the magnitude of the volcanic heat influx relative to the surface area of the lake small lakes have only a small capacity for heat dissipation and their temperature rises quickly with only small heat inputs large lakes are buffered against variations in heat input both the heat dissipation and meteoric water input into a lake are functions of lake surface area and therefore each lake water temperature demands a certain precipitation rate for mass conservation independent of lake size the results of energy mass balance modeling shows that under common atmospheric conditions most steady state volcanic lakes are unlikely to maintain a temperature in excess of 45 50 c validation of the volcanic lake model was performed using published data from yugama lake japan and the keli mutu lakes indonesia also the model was applied to 24 natural systems to provide a baseline assessment of energy fluxes under the model assumptions so future work on those systems can identify nuances in individual systems that deviate from the simple model conditions we recommend the model for use in assessing temperature variations and volcanic lake stability in settings with known physical and atmospheric conditions application of the energy mass balance calculations of model lakes provides a genetic classification scheme largely based on physical process parameters

a grid refinement based approach for modeling the convective boundary layer in the gray zone a pilot study abstractthe model gray zone refers to the range of grid spacings comparable to the dominant length scale of the flow in the gray zone the flow is partially resolved and partially subgrid scale sgs neither ensemble averaging based parameterizations nor turbulence closures are appropriate for parameterizing the effects of sgs motions on the resolved flow the gray zone of the convective boundary layer cbl is in the range of cbl depth typically o 1 km a new approach that seeks explicit resolution of the unstable surface layer through a nest layer of fine grid spacing is proposed to improve cbl parameterization in the gray zone to provide the theoretical basis for the approach a linear analytic model is presented and one way nested simulations are performed to investigate the dynamical coupling between the surface layer and the mixed layer the analytic model shows that at the onset of thermal instability the vertical and horizontal structures of the mixed layer are set by surface layer forcings

positive and negative ionospheric storms occurring during the 15 may 2005 geomagnetic superstorm this study focuses on the 15 may 2005 geomagnetic superstorm and aims to investigate the global variation of positive and negative storm phases and their development observations are provided by a series of global total electron content maps and multi instrument line plots coupled thermosphere ionosphere plasmasphere electrodynamics ctipe simulations are also employed results reveal some sunward streaming plumes of storm enhanced density sed over asia and a well developed midlatitude trough over north america forming isolated positive and negative storms respectively the simultaneous development of positive and negative storms over north america is also shown then some enhanced auroral ionizations maintained by strong equatorward neutral winds appeared in the depleted nighttime ionosphere meanwhile the northern nighttime polar region became significantly depleted as the sed plume plasma could not progress further than the dayside cusp oppositely a polar tongue of ionization toi developed in the daytime southern polar region according to ctip simulations solar heating locally maximized minimized over the southern northern magnetic pole furthermore strong upward surges of molecular rich air created o n decreases both in the auroral zone and in the trough region while some sed related downward surges produced o n increases from these results we conclude for the time period studied that 1 composition changes contributed to the formation of positive and negative storms 2 strengthening polar convection and increasing solar heating of the polar cap supported polar toi development and 3 a weaker polar convection and minimized solar heating of the polar cap aided the depletion of polar plasma

convergence behavior of idealized convection resolving simulations of summertime deep moist convection over land convection resolving models crms can explicitly simulate deep convection and resolve interactions between convective updrafts they are thus increasingly used in numerous weather and climate applications however the truncation of the continuous energy cascade at scales of mathcal o 1 km poses a serious challenge as in kilometer scale simulations the size and properties of the simulated convective cells are often determined by the horizontal grid spacing delta x in this study idealized simulations of deep moist convection over land are performed to assess the convergence behavior of a crm at delta x 8 4 2 1 km and 500 m two types of convergence estimates are investigated bulk convergence addressing domain averaged and integrated variables related to the water and energy budgets and structural convergence addressing the statistics and scales of individual clouds and updrafts results show that bulk convergence generally begins at delta x 4 km while structural convergence is not yet fully achieved at the kilometer scale despite some evidence that the resolution sensitivity of updraft velocities and convective mass fluxes decreases at finer resolution in particular at finer grid spacings the maximum updraft velocity generally increases and the size of the smallest clouds is mostly determined by delta x a number of different experiments are conducted and it is found that the presence of orography and environmental vertical wind shear yields more energetic structures at scales much larger than delta x sometimes reducing the resolution sensitivity overall the results lend support to the use of kilometer scale resolutions in crms despite the inability of these models to fully resolve the associated cloud field

naturally acid waters from copahue volcano argentina volcanic acid sulfate chloride brines form through absorption of volcanic vapors in shallow reservoirs of meteoric water reaction with surrounding volcanic rocks leads to partial neutralization of the fluids and precipitation of secondary minerals chemical data of such acid waters from copahue volcano argentina covering 8 years of observations show evidence for changes in composition related to water rock interaction at depth prior to emergence of the fluids at the surface the chemical composition changed dramatically during the 2000 eruption of copahue with enhanced concentrations and fluxes of mg na fe and al followed in 2001 by rapidly declining concentrations and element fluxes the subsequent 5 years saw more variable element ratios and strong depletions in k and al most incompatible elements are released from the rock matrix stochiometrically whereas some elements are enriched through vapor input from the magma as pb zn most fluids have lree enrichments relative to the rock matrix but during periods of new magma intrusion the lree enrichment decreases as does the magnitude of the negative eu anomaly in the fluids these observations are interpreted assuming early dissolution of plagioclase olivine and volcanic glass that occurs during intrusion of new magma into the hydrothermal system the high field strength elements are virtually immobile even in these hot acid fluids with nb and ta more so than hf and zr the mobility of u and th in these fluids is comparable at variance with th behavior in neutral fluids the local rivers and lakes of copahue are fertilized by volcanic dissolved p and most surface waters with ph 3 have high levels of as the acid fluids from copahue may be surficial analogs for deep subduction fluids that evolve below zones of arc magma generation as well as for early mars environments that are thought to have had large acid lakes