secondary circulation in a region of flow curvature relationship with tidal forcing and river discharge 1 on the basis of a 301 day acoustic doppler current profiler mooring in an estuarine tidal strait the strength and structure of secondary circulation in a region of flow curvature is related to variations in tidal forcing and river discharge during low flow conditions the structure of secondary flow is consistent with a centrifugally forced helical flow with bottom flow toward the inside of the bend and surface flow toward the outside of the bend the strength of secondary flow increases linearly with tidal range and is consistent with a vertical eddy viscosity that is linearly dependent on tidal current speed during times of high river discharge the strength of secondary flow is significantly reduced and its vertical structure undergoes a fundamental change over the spring neap cycle during spring tides the classic helical flow pattern is evident albeit weaker than during low flow conditions however during neap tides a more complex two cell structure is evident the change between these two states occurs with a spring neap transition in the subtidal flow indicating that it is also accompanied by changing stratification simple scaling analysis suggests that during weakly stratified conditions secondary circulation will influence stream wise dynamics and dispersion for channels with widths on order or less than 0 1 h cd where h is the water column depth and cd is a quadratic bottom drag coefficient in contrast during highly stratified conditions lateral excursions due to secondary flows are limited to approximately one tenth of the channel s width and are an ineffective lateral mixing agent

the life cycle of baroclinic eddies in a storm track environment abstract the life cycle of baroclinic eddies in a controlled storm track environment has been examined by means of long model integrations on a hemisphere a time lagged regression that captures disturbances with large meridional velocities has been applied to the meteorological variables this regressed solution is used to describe the life cycle of the baroclinic eddies the eddies grow as expected by strong poleward heat fluxes at low levels in regions of strong surface baroclinicity at the entrance of the storm track in a manner similar to that of charney modes as the eddies evolve into a nonlinear regime they grow deeper by fluxing energy upward and the characteristic westward tilt exhibited in the vorticity vanishes by rotating into a meridional tilt in which the lower level cyclonic vorticity center moves poleward and the upper level center moves equatorward this rather classical picture of baroclinic evolution is radically modified by the simultaneous development of an upper level eddy downs

role of narrow mountains in large scale organization of asian monsoon convection abstract the asian summer monsoon is organized into distinct convection centers but the mechanism for this organization is not well understood analysis of new satellite observations reveals that narrow mountain ranges are an important organizing agent anchoring monsoon convection centers on the windward side the bay of bengal convection in particular features the heaviest precipitation on its eastern coast because of orographic lifting as the southwest monsoon impinges on the coastal mountains of myanmar also known as burma this is in contrast to the widely held view that this convection is centered over the open ocean as implied by coarse resolution datasets a view that would require an entirely different explanation for its formation narrow in width and modest in height 1 km these mountains are hardly mentioned in conceptual depictions of the large scale monsoon and poorly represented in global climate models the numerical simulations of this study show that orographic rainbands are not a

vertical mapping of hydrothermal fluids and alteration from bulk conductivity simple interpretation on the usdp 1 site unzen volcano sw japan abstract volcanic edifices often have hydrothermal systems in the shallow subsurface and these hydrothermal systems may discharge volcanic gases electrical conductivity resistivity surveys have potential for the estimation of the fluxes of volcanic gases because interstitial water conductivity steeply increases when salinity increases by the dissolution of volcanic gases however in the subsurface of volcanoes there are essentially two factors increasing bulk conductivity the salinity of hydrothermal fluids and conductive clays by hydrothermal alteration therefore the estimation of the fluxes of volcanic gases by electromagnetic methods requires to separate bulk conductivity simply into pore water conductivity f and matrix conductivity s which are related to salinity and hydrothermal alteration respectively the objective of this study is to separate observed bulk conductivity simply into f and s by the use of drillcore samples based on revil s model and to map the vertical variation of these two conductivity components for examination relation between bulk conductivity and hydrothermal fluids as the first step toward demonstrating the feasibility and practicality of using geophysical methods to constrain volcanic gas fluxes as a case study this study was conducted at the usdp 1 borehole site located on unzen volcano sw japan and the bulk conductivity was successfully separated the results consistently explained the vertical profiles of temperature and core permeability and suggested little hydrothermal alteration at this study site the simple method of separating bulk conductivity may be applicable to vertical or lateral mapping of hydrothermal fluids and alteration at volcanoes and separated values of f and s may be of great help for the estimation of the fluxes of volcanic gases and the intensity of hydrothermal alteration

ageostrophic geopotential fluxes in downstream and upstream development of baroclinic waves abstract with the use of a simple primitive equation model it is demonstrated that the convergence divergence of ageostrophic geopotential fluxes can be a major source sink of kinetic energy for both downstream and upstream development of baroclinic waves and can play a dominant role during the early stages of wave development it is also shown that both surface friction and effects lead to an asymmetry in the upstream versus downstream development with downstream development much stronger a total group velocity is defined based on ageostrophic fluxes and its relationship to the rate of wave packet spreading and to convective and absolute instability is discussed

origin of volcanic gases discharging from a cooling lava dome of unzen volcano japan abstract chemical and isotopic compositions were measured for volcanic gases discharged from the recently erupted heisei shinzan dome of unzen volcano the volcanic gases are largely mixed with the air whose content ranges from 60 to 90 chemical and isotopic compositions of the gases are corrected for the air mixing accounting not only for the major air components but also for contribution of the atmospheric moisture and co 2 the variation of the corrected composition revealed that these gases are derived from various sources including 1 the air circulating through the lava domes 2 the local meteoric water at various degrees of evaporation and vapor loss 3 the magmatic co 2 likely originated from a deep source and 4 the gases discharged from the cooling lava dome the gases discharged from the cooling lava dome are characterized by the oxygen and hydrogen isotopic composition typical of the subduction type volcanoes but with high cl content and high cl s and f s ratios in contrast discharges of co 2 with the magmatic 13 c values are not correlated with discharge of heat or acid gas species suggesting the ascent of co 2 rich fluids from a deep source possibly through the volcanic conduit

extreme alteration by hyperacidic brines at kawah ijen volcano east java indonesia ii metasomatic imprint and element fluxes abstract the hyperacidic brines of the kawah ijen crater lake and banyu pahit river east java indonesia induce an intense alteration on their magmatic host rock this alteration is a proxy for water rock interaction in magmatic hydrothermal systems and associated high sulphidation mineralizing environments as well as for how these systems translate changes in the magmatic system to surface emissions which are used in volcanic hazard monitoring detailed bulk chemical study of altered and unaltered samples shows that alteration is characterised by near complete leaching of all major and trace elements except for pb sn and sb which are progressively enriched pb up to 15 fold absolute enrichment the resulting element release is complementary to the observed changes in composition of the banyu pahit water downstream when corrected for dilution indicating that alteration progressively increases the element load the signature of the change in water chemistry is best explained by complete alteration of fresh rock rather than mature alteration which might be expected given the advanced altered state of the riverbed together with mass balance considerations this indicates that the dominant element source is material falling into the river from the valley flanks the chemical signature of the crater lake is inconsistent with the observed alteration in samples from the hydrothermal system and likewise is best explained by surface input of cations from rocks falling in from the crater walls this indicates that the lake water cation chemistry is not a direct reflection of the underlying magmatic hydrothermal system and that its cation content is therefore not an appropriate monitor of changes in volcanic activity

wave packets and life cycles of troughs in the upper troposphere examples from the southern hemisphere summer season of 1984 85 abstract in this paper reanalysis data for the southern hemisphere summer season of 1984 85 produced by the european centre for medium range weather forecasts have been analyzed to examine wave packets and life cycles of baroclinic waves a semiobjective algorithm has been devised to track wave packets it is found that the perturbations in the upper troposphere are dominated by wave packets some of these wave packets can be tracked for several weeks during which they can make up to two trips around the latitude circle the energy life cycles of waves that make up several of these wave packets were analyzed and apart from the incipient waves that started the wave packets most of the subsequent wave development was found to be dominated by convergence and divergence of energy fluxes rather than due to baroclinic or barotropic conversions demonstrating that these wave packets are indeed coherent entities that propagate due to downstream development or dispersion the energy life cycle of the most

major and trace element geochemistry of neutral and acidic thermal springs at el chichon volcano mexico implications for monitoring of the volcanic activity abstract four groups of thermal springs with temperatures from 50 to 80 c are located on the s sw w slopes of el chichon volcano a composite dome tephra edifice which exploded in 1982 with a 1 km wide 160 m deep crater left very dynamic thermal activity inside the crater variations in chemistry and migration of pools and fumaroles drastic changes in the crater lake volume and chemistry contrasts with the stable behavior of the flank hot springs during the time of observations 1974 2005 all known groups of hot springs are located on the contact of the basement and volcanic edifice and only on the w sw s slopes of the volcano at almost same elevations 600 650 m asl and less than 3 km of direct distance from the crater three groups of near neutral ph 6 springs at sw s slopes have the total thermal water outflow rate higher than 300 l s and are similar in composition the fourth and farthest group on the western slope discharges acidic ph 2 saline 10 g kg of cl water with a much lower outflow rate water rock interaction modeling of main types of the el chichon thermal waters using regular log q k graphs saturation indices vs temperature showed maximum equilibrium temperature slightly higher than 200 c acidic waters are equilibrated with some clay minerals at about 120 c three main sources of the salinity of thermal water are suggested on the basis of mixing plots and isotopic data a magmatic source for co2 boron sulfur and a limited part of cl volcanic rock source for the major cations and trace elements the oil bearing evaporitic basement source oil field brine for nacl br a part of ca and some trace elements all flank thermal springs end up in the river rio magdalena that has a variable seasonal flow rates from 4 to 20 m3 s any changes in the chemistry of springs must notably change the composition of the streams draining hot springs and eventually rio magdalena a monthly geochemical monitoring of rio magdalena and streams draining main hot springs would be a useful tool for surveying the activity of the volcano

sediment pumping by tidal asymmetry in a partially mixed estuary 1 observations collected at two laterally adjacent locations are used to examine the processes driving sediment transport in the partially mixed york river estuary estimates of sediment flux are decomposed into advective and pumping components to evaluate the importance of tidal asymmetries in turbulent mixing at the instrumented location in the estuarine channel a strong asymmetry in internal mixing due to tidal straining is documented with higher values of eddy viscosity occurring during the less stratified flood tide as a result of this asymmetry more sediment is resuspended during the flood phase of the tide resulting in up estuary pumping of sediment despite a net down estuary advective flux at the instrumented location on the adjacent shoal where no pronounced tidal asymmetry in internal mixing was found both the pumping flux and advective flux were directed down estuary the down estuary pumping of sediment on the shoal appears to be driven by asymmetries in bed stress the impact of tidal asymmetries in bed stress at the channel location was negated because the amount of sediment available for resuspension was limited as a result the pumping flux was dominated by the overlying asymmetries in internal mixing the asymmetries in stratification appear to exert an important control on the vertical distribution of sediment by both impacting the eddy diffusivity as well as the fall velocity during the more turbulent flood tide the fall velocities are smaller suggesting the kolmogorov microscale is setting the upper bound on floc diameter

trace elements in the thermal groundwaters of vulcano island sicily abstract the chemical concentrations of many trace elements that have never before been examined in vulcano island groundwaters are reported chemical data indicate that rock composition is not the only factor determining the metal content in the aqueous system the observed concentrations depend mainly on 1 the chemical composition of the host rocks 2 the chemical physical conditions of the weathering solution temperature acidity redox conditions 3 input of magmatic gases 4 adsorption of metal ions on oxide particles formation of soluble complexes and or precipitation of solid phases chloride complexes in solution are of minimal significance for all elements with the exception of cd whereas carbonate complexes are important for pb uo 2 zn and ni temperature and trace element distribution maps are also presented

lateral circulation and sediment transport driven by axial winds in an idealized partially mixed estuary 1 a 3d hydrodynamic model roms is used to investigate lateral circulation in a partially mixed estuary driven by axial wind events and to explore the associated transport of sediments the channel is straight with a triangular cross section the model results suggest that driving mechanisms for lateral circulation during axial wind events are different between stratified and unstratified conditions when the water column is largely unstratified rotational effects do not drive significant lateral circulation instead differential advection of the axial salinity gradient by wind driven axial flow is responsible for regulating the lateral salinity gradients that in turn drive bottom divergent convergent lateral circulation during down up estuary winds from the subtidal lateral salt balance it is found that the development of lateral salinity gradient by wind induced differential advection is largely counterbalanced by the advection of salt by lateral circulation itself when the water column is stratified the lateral flow and salinity structures below the halocline closely resemble those driven by boundary mixing and rotational effects are important lateral sediment flux and the event integrated sediment transport are from channel to shoals during down estuary winds but reversed for up estuary winds potential impacts of wind generated waves on lateral sediment transport are evaluated with two cases representing event conditions typical of upper chesapeake bay accounting for wind wave effects results in an order of magnitude increase in lateral sediment fluxes because of greater bottom stresses and sediment resuspension

southern hemisphere summertime rossby waves and weather in the australian region motivated by recent studies on the significant summertime weather patterns in the australian region the life cycle of summertime transient rossby wave packets in the southern hemisphere is investigated the strength of the interaction between the wave packets and the jet i is defined by the advection of potential vorticity by the divergent part of the wind on the 350 k isentropic surface the magnitude of i is used as the basis for time lagged composites in distinct regions sw chile sw africa over the indian ocean sw australia and over the w pacific the interaction is strongest on the stratospheric side of the jet core although in each case cyclogenesis from a pre existing disturbance in the upper troposphere precedes the generation of the rossby wave packets there are two types of interaction with the jet in the sw chile sw africa and indian ocean cases extratropical cyclogenesis and the associated convection lies on the poleward side of the jet and hence i is positive in the sw australia and w pacific cases extratropical cyclogenesis occurs 3 days earlier than the others and i is negative as it describes the interaction of a downstream propagating rossby wave packet with the subtropical jet in all cases as the cyclones develop the wave activity propagates from low levels to the upper levels of the troposphere and then downstream and equatorwards towards higher values of refractive index the equatorward refraction of the sw australia and w pacific wave packets is accompanied by enhanced tropical convection in the warm conveyor belt of the advancing front

uncertainties in a regional climate model in the midlatitudes due to the nesting technique and the domain size 1 deficiencies of the nesting technique for regional models and their internal variability represent a significant source of uncertainties in regional model outputs presented numerical experiments on four different size domains two of them being midlatitude channel domains show that the spatial structure and magnitude of uncertainties strongly depend on the domain size the experiments are performed by using the weather research and forecasting wrf model nested into the operational european centre for medium range weather forecasts ecmwf analyses on the same horizontal resolution 0 25 0 25 and by nesting wrf into a larger wrf domain with the same resolution uncertainties are quantified by the root mean square differences rmsd between the wrf results and their driving lateral boundary fields the results from the midlatitude channel domain show that uncertainties in the tropospheric wind associated with the imperfect nesting method are amplified in the baroclinically active regions of the atlantic and pacific the zonal wind rmsd have a dipole structure in the atlantic in both the midlatitude channel and the half channel simulations nested into ecmwf the dipole is absent when wrf is nested into itself on the contrary the maximal rmsd for the meridional wind are always located in the domain center when the domain centered on europe excludes the western atlantic and north america the simulated uncertainties become spatially nearly homogeneous and the magnitude of rmsd due to the imperfect nesting technique greatly reduces

characteristics of wave packets in the upper troposphere part i northern hemisphere winter abstract gridded data produced by the ecmwf reanalysis project have been analyzed to document the properties of wave packets in the northern hemisphere winter midlatitude upper troposphere based on results from earlier investigations 300 hpa meridional wind variations were chosen for analysis wave packet envelopes were also defined by performing complex demodulation on the wind data the properties of the wave packets are mainly illustrated using time lagged one point correlation maps performed both on and wave packet envelopes the results show that over most regions in the northern hemisphere winter with the exception of the deep tropics and near the aleutian low medium scale waves dominant wavenumber 5 8 exhibit the characteristics of downstream development and occur within wave trains that propagate with eastward group velocities much faster than the phase speeds of individual phases of the waves their group velocity is highly correlated with the local time mean 200 400 hpa wind while the

investigation of regional climate models internal variability with a ten member ensemble of 10 year simulations over a large domain previous investigations on regional climate models rcm internal variability iv were limited owing to small ensembles short simulations and small domains the present work extends previous studies with a ten member ensemble of 10 year simulations performed with the canadian regional climate model over a large domain covering north america the results show that the iv has no long term tendency but rather fluctuates in time following the synoptic situation within the domain the iv of mean sea level pressure mslp and screen temperature st show a small annual cycle with larger values in spring which differs from previous studies for precipitation pcp the iv shows a clear annual cycle with larger values in summer as previously reported the 10 year climatology of the iv for mslp and st shows a well defined spatial distribution with larger values in the northeast of the domain near the outflow boundary a comparison of the iv of mslp and st in summer with the transient eddy variance reveals that the iv is close to its maximum in a small region near the outflow boundary same analysis for pcp in summer shows that the iv reaches its maximum in most parts of the domain except for a small region on the western side near the inflow boundary finally a comparison of the 10 year climate of each simulation of the ensemble showed that the iv may have a significant impact on the climatology of some variables

structure and evolution of baroclinic waves as inferred from regression analysis abstract the structure of transient disturbances with periods shorter than a week is documented an the basis of one point regression maps and longitude height sections derived from the national meteorological center nmc operational analyses for nine winter seasons the reference time series for the regression coefficients is highpass filtered normalized 500 mb height at a grid point in the pacific stormtrack the field variables that were regreesed on the reference time series were not filtered the regression statistics yield quantitative estimates of the amplitudes of the high frequency fluctuations in the geopotential height temperature wind ageostrophic wind vorticity divergence vertical velocity and outgoing longwave radiation fields the observed high frequency fluctuations exhibit a vertical and meridional structure suggestive of baroclinic waves evolving through the mature phase of their life cycle most of the results are in qualitative agreement with previous studies but the ageostrop

the chemical and hydrologic structure of poa s volcano costa rica comparison of the chemical characteristics of spring and river water draining the flanks of poa s volcano costa rica indicates that acid chloride sulfate springs of the northwestern flank of the volcano are derived by leakage and mixing of acid brines formed in the summit hydrothermal system with dilute flank groundwater acid chloride sulfate waters of the rio agrio drainage basin on the northwestern flank are the only waters on poa s that are affected by leakage of acid brines from the summit hydrothermal system acid sulfate waters found on the northwestern flank are produced by the interaction of surface and shallow groundwater with dry and wet acid deposition of so2 and h2so4 aerosols respectively the acid deposition is caused by a plume of acid gases that is released by a shallow magma body located beneath the active crater of poa s no evidence for a deep reservoir of neutral ph sodium chloride brine is found at poa s the lack of discharge of sodium chloride waters at poa s is attributed to two factors 1 the presence of a relatively volatile rich magma body degassing at shallow depths 1 km into a high level summit groundwater system and 2 the hydrologic structure of the volcano in which high rates of recharge combine with rapid lateral flow of shallow groundwater to prevent deep seated sodium chloride fluids from ascending to the surface the shallow depth of the volatile rich magma results in the degassing of large quantities of so2 and hcl these gases are readily hydrolyzed and quickly mix with meteoric water to form a reservoir of acid chloride sulfate brine in the summit hydrothermal system high recharge rates and steep hydraulic gradients associated with elevated topographic features of the summit region promote lateral flow of acid brines generated in the summit hydrothermal system however the same high recharge rates and steep hydraulic gradients prevent lateral flow of deep seated fluids thereby masking the presence of any sodium chloride brines that may exist in deeper parts of the volcanic edifice structural stratigraphic and topographic features of poa s volcano are critical in restricting flow of acid brines to the northwestern flank of the volcano a permeable lava lahar sequence that outcrops in the rio agrio drainage basin forms a hydraulic conduit between the crater lake and acid chloride sulfate springs spring water residence times are estimated from tritium data and indicate that flow of acid brines from the active crater to the rio agrio source springs is relatively rapid 3 to 17 years hydraulic conductivity values of the lava lahar sequence calculated from residence time estimates range from 10 5 to 10 7 m s these values are consistent with hydraulic conductivity values determined by aquifer tests of fractured and porous lava pyroclastic sequences at the base of the northwestern flank of the volcano fluxes of dissolved rock forming elements in rio agrio indicate that approximately 4300 and 1650 m3 of rock are removed annually from the northwest flank aquifer and the active crater hydrothermal system respectively over the lifetime of the hydrothermal system 100 s to 1000 s of years significant increases in aquifer porosity and permeability should occur in marked contrast to the reduction in permeability that often accompanies hydrothermal alteration in less acidic systems average fluxes of fluoride chloride and sulfur calculated from discharge and compositional data collected in the rio agrio drainage basin over the period 1988 1990 are approximately 2 38 and 30 metric tons day these fluxes should be representative of minimum volatile release rates at poa s in the last 10 to 20 years

one way nested regional climate simulations and domain size abstract the impact of domain size on regional climate simulations is explored in the context of a state of the art regional model centered over western europe it is found that the quality of the climate simulations is highly dependent on the domain size moreover the choice of an optimal version is more complex than usually thought the less appropriate domain having an intermediate size about 3000 km 3000 km and the best versions nearly cover a quarter of the northern hemisphere the use of periodically reinitialized trajectories does improve the climate of suboptimal models but leads to unrealistic dynamical behaviors the implications for regional climate simulations are briefly discussed

the effect of grid spacing and domain size on the quality of ensemble regional climate downscaling over south asia during the northeasterly monsoon the performance of an ensemble based dynamical regional climate downscaling system is evaluated over southern asia in a northeasterly monsoon season for different choices in grid spacing and domain size a seven member ensemble of the echam4 5 global climate model at a resolution of about 300 km grid size was used to drive the regcm3 regional climate model with grid sizes of 100 50 25 and 20 km respectively the performance is reported in detail over sri lanka two sets of regional model runs were undertaken to assess the effect of grid spacing and model domain size on the downscaling performance the regcm3 simulation with 100 km grid size significantly underestimates the height of the central mountain range in sri lanka in a manner that is too coarse to capture orographic influences on the rainfall however the regcm3 simulations with grid sizes from 20 to 50 km capture mesoscale features that arise from uplift condensation on the windward side of the monsoon winds due to the topography these simulations also capture the orographic influences on the month to month rainfall over sri lanka that were absent in the echam4 5 while the small domain runs where only the forcings for the region immediately around sri lanka 48 118n 768 858e are used are computationally more efficient the results are overly controlled by the lateral boundary driving of the echam4 5 so they inherit large uncertainty from the seven echam4 5 realizations used for the regcm3 ensemble runs the large domain simulation used a domain comprising both land and ocean approximately 48s 228n 658 968e the large domain group of simulations produced reasonable spatial distribution of precipitation over the region moreover the ensemble spread was considerably reduced in the large domain high resolution runs therefore fine enough grid resolution 25 km or less and sufficiently large domain size are both needed to simulate the essential features of precipitation in this tropical and monsoonal region

a geochemical model for fumaroles of the mutnovsky volcano kamchatka ussr abstract on the basis of the chemical isotopic and thermodynamic characteristics of fluids sampled between 1964 and 1989 a genetic model description is given for fumaroles of the mutnovsky volcano there are three individual groups of fumaroles in the mutnovsky crater which show stable activity for a long period of time the active funnel temperatures exceed 600 c the upper field up to 320 c and the bottom field from 100 to 150 c the three principal zones of emission have different gas composition water isotopic composition radioactivity and 3he 4he ratios the abundance of magmatic components in the high temperature fumaroles of the active funnel is much higher than those in gases from the other groups emission rate of so2 from the active funnel is about 200 t d which requires complete degassing as a minimum of 1 km3 of magma every 20 years fluids of the upper field contain up to 80 of steam from the mutnovsky geothermal system temperature variations of the bottom field fumaroles from 97 c before 1982 to 151 c in 1989 result from changes in hydrological conditions in the crater evaporation of high saline acid brine which is formed in the interior of the volcano is responsible for the composition of the bottom field gas steam discharges

on the dynamics of a storm track abstract an idealized primitive equation model is used to determine the factors controlling the dynamics and maintenance of eddy activity in a storm track the results show that localized regions of enhanced baroclinicity do not necessarily lead to localization of eddy activity by studying the energetics of the storm track it is shown that while baroclinic conversion does indeed correlate with the region of maximum baroclinicity it is the downstream radiation of energy through the ageostrophic geopotential fluxes which acts as a trigger for the development and maintenance of eddy activity over less baroclinic regions extending the region of eddy activity much further downstream from the region of high baroclinicity examples of eddy life cycles are given that show that convergence and divergence of ageostrophic fluxes can dominate baroclinic and barotropic conversion especially in regions with weak baroclinicity factors that may limit the zonal extent of a storm track are discussed evidence of down

wrf hindcasts of cold front passages over the arm eastern north atlantic site a sensitivity study abstractthe present study explores the ability of the weather research and forecasting wrf model to accurately reproduce the passage of extratropical cold fronts at the doe arm eastern north atlantic ena observation site on the azores an analysis of three case studies is performed in which the impact of the wrf domain size position of the model boundary relative to the ena site grid spacing and spectral nudging conditions are explored the results from these case studies indicate that model biases in the timing and duration of cold front passages change with the distance between the model domain boundary and the ena site for these three cases if the western model boundary is farther than 1500 km from the site the front becomes too meridional and fails to reach the site making 1000 or 1500 km the optimal distances in contrast integrations with small distances e g 500 km between the site and domain boundaries have inadequate spatial spinup i e the domain is too small for the model to pr

an energetic view of the relation between the mediterranean storm track and the north atlantic oscillation the time tendency equation of eddy kinetic energy eke includes some important forcing terms such as baroclinic conversion bcc barotropic conversion btc and energy flux this article compares the ensemble mean distribution of these forcing terms as well as the baroclinic generation bcg term in critical positive and critical negative months of the north atlantic oscillation nao focusing on the mediterranean and middle east regions results show that all the computed terms attain larger values and all the extrema are stronger in the positive phase the energy flux vectors point to energy transfer from the west of the atlantic and north of europe to the mediterranean region with the transfer being weaker in the positive phase there is energy flux divergence over the central region of the mediterranean sea which is more extensive in the positive phase relative to the negative phase the energy flux divergence leads to a radiation source in this region the direction of the energy flux vectors then indicates that the energy radiated from the central mediterranean region is transferred southeastward leading to an energy flux convergence over the red sea and the northeast of africa this convergence is stronger and more extensive in the positive phase which may be responsible for the observed larger value of the upper level eddy kinetic energy in the positive phase the patterns of the bcg and bcc together with the energy flux convergence suggest that while the mediterranean storm track is affected by the north atlantic storm track more strongly in the negative phase it acts as an independent centre of action by radiating energy southeastward in the positive phase copyright 2011 royal meteorological society

mobility and fluxes of major minor and trace metals during basalt weathering and groundwater transport at mt etna volcano sicily abstract the concentrations and fluxes of major minor and trace metals were determined in 53 samples of groundwaters from around mt etna in order to evaluate the conditions and extent of alkali basalt weathering by waters enriched in magma derived co 2 and the contribution of aqueous transport to the overall metal discharge of the volcano we show that gaseous input of magmatic volatile metals into the etnean aquifer is small or negligible being limited by cooling of the rising fluids basalt leaching by weakly acidic co 2 charged water is the overwhelming source of metals and appears to be more extensive in two sectors of the s sw paterno and e zafferana volcano flanks where out flowing groundwaters are the richest in metals and bicarbonate of magmatic origin thermodynamic modeling of the results allows to evaluate the relative mobility and chemical speciation of various elements during their partitioning between solid and liquid phases through the weathering process the facts that rock forming minerals and groundmass dissolve at different rates and secondary minerals are formed are taken into account at mt etna poorly mobile elements al th fe are preferentially retained in the solid residue of weathering while alkalis alkaline earth and oxo anion forming elements as se sb mo are more mobile and released to the aqueous system transition metals display an intermediate behavior and are strongly dependent on either the redox conditions mn cr v or solid surface related processes v zn cu the fluxes of metals discharged by the volcanic aquifer of etna range from 7 0 10 3 t a th to 7 3 10 4 t a na they are comparable in magnitude to the summit crater plume emissions for a series of elements na k ca mg u v li with lithophile affinity but are minor for volatile elements basalt weathering at mt etna also consumes about 2 1 10 5 t a of magma derived carbon dioxide equivalent to ca 7 of contemporaneous crater plume emissions the considerable transport of some metals in etna s aquifer reflects a particularly high chemical erosion rate evaluated at 2 3 10 5 t a enhanced by the initial acidity of magmatic co 2 rich groundwater

andesitic magma degassing investigated through h2o vapour melt partitioning of halogens at soufriere hills volcano montserrat lesser antilles magma degassing at soufriere hills volcano shv is characterised by an almost permanent so2 flux and a hcl production rate which mainly depends on dome growth rate degassing processes have been studied through textural h2o and halogen analyses of clasts collected between 1995 and 2006 on the dome and in pyroclastic flows and vulcanian eruption deposits cl br and i are strongly depleted in melts during h2o degassing with no significant cl br i fractionation whereas f is almost unaffected all magmas erupted at shv have followed a multi step degassing path from the magma chamber up to a shallow depth 1 km p 20 mpa from that depth however effusive and explosive paths are distinct vulcanian eruptions are the result of closed system degassing csd while effusive dome growth is the result of csd up to a very shallow depth 200 m p 5 2 mpa followed by open system degassing osd csd is modelled using the h2o solubility law the perfect gas law and partition coefficients of halogens between a rhyolitic melt and h2o vapour dv li gas loss characteristic of osd is modelled using a rayleigh law degassing induced crystallisation is introduced through the ratio of crystallisation and degassing rates which ranges from 150 500 dv lcl for osd ranges between 50 300 increasing with melt cl content for csd the lower effective dv lcl 20 is attributed to kinetic effects dome forming activity has a greater impact on atmospheric chemistry than vulcanian eruptions because osd is much more efficient at extracting halogens the model shows that hcl flux is a good proxy for the dome forming eruption rate comparison between model and measured gas compositions suggests a high hbr bro conversion rate bro total br 1 3 in the shv gas plume the degassing behaviour of cl br and i implies similar cl br 160 and br i 90 in initial melts volcanic clasts and high temperature gases the low cl br at shv compared to other island arcs 250 300 is attributed to a shallow pre eruptive br enrichment the almost permanent dome extrusion at shv since 1995 has likely had a significant regional atmospheric impact because of the very efficient effusive degassing and the high conversion rate of halogens into reactive species within the gas plume

axial convergence in a well mixed estuary abstract transverse secondary circulations involving surface convergence observed in a well mixed estuary in north wales are made visible by the collection of surface material along an axial line which extends continuously for many kilometres through the estuary the circulation and axial convergence however are seen only during the flood phase of the tide and no similar behaviour has been observed during the ebb phase convergent circulations in the estuary are associated with small but steady transverse density gradients in the cross section produced by non uniform advection of the longitudinal gradient through the channel a diagnostic model using measured mean distributions of cross sectional density indicates surface transverse velocities 0 1 ms 1 similar to those observed in the estuary the model further predicts appreciable transverse divergent currents at a fractional depth of 0 75 a prediction which has been tested in the estuary using a vertical array of accurately resolving current direction indicators

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

dynamics of the surface wind field over the equatorial indian ocean the annual cycle and interannual variability of the equatorial westerlies over the indian ocean are examined in the context of the equations of motion using long term surface ship observations eastward pressure gradient along the equator may accelerate equatorial westerlies but the process is more intricate the south indian ocean trade winds can recurve in the southern hemisphere only with an eastward pressure gradient this is counteracted by the coriolis acceleration directed at right angles to the left of the motion with weak trades and strong eastward pressure gradient the flow can recurve at relatively high southern latitudes thus allowing a broad equatorial zone in which westerlies can develop in the annual cycle the southern indian ocean high and trade winds are closest to the equator and strongest in austral winter when however the eastward pressure gradient in the equatorial zone is also steepest accordingly the latitude of flow recurvature in the southern trade winds stays farthest away from the equator in boreal spring and autumn consequently the equatorial westerlies peak in these short transition seasons the boreal autumn equatorial westerlies are the surface manifestation of a powerful zonal circulation cell along the indian ocean equator the interannual variability of boreal autumn is characterized by weak westerlies accompanying a slack zonal pressure gradient and strong southern trade winds with recurvature near the equator such an ensemble of circulation departures is characteristic of abundant rainfall in east africa and deficient precipitation in indonesia copyright 2004 royal meteorological society

lateral circulation and suspended sediment transport in a curved estuarine channel winyah bay sc usa 1 shipborne vertical profiles of flow and suspended sediment concentration collected on a transect across a curved nonsymmetrical estuarine channel are presented analysis of the transient cross channel momentum balance equation shows that the lateral circulation pattern is controlled by the interaction between centrifugal and lateral baroclinic forcings although those two might not be necessarily in balance as suggested earlier by seim and gregg 1997 instead differential along channel advection and local acceleration appear to influence greatly lateral circulation dynamics during ebb when the water column is highly stratified the interaction between centrifugal acceleration and opposite directed lateral baroclinic forcing results in weak lateral flows during flood lateral flows are dominated by centrifugal acceleration which is directed toward the outside of the curvature at the mid depth because of the nonlogarithmic current profile and reinforced by lateral baroclinic forcing this results in strong two layer clockwise circulation looking up estuary during flood the eastward directed bottom currents during ebb deliver only a small amount of suspended sediment from the relatively narrow western shoal to the channel bed during flood the west directed near bed currents deliver a significant amount of sediments from the gentle broad eastern shoal which in conjunction with the locally resuspended sediment load promotes the development of the estuarine turbidity maximum increased lateral advection of sediments during flood reinforces a tidal asymmetry in the development of turbidity maximum decomposition analysis of lateral sediment fluxes averaged over a tidal cycle suggests convergence of sediment toward the center of the channel is driven mainly by the oscillatory tidal component

effects of winds on stratification and circulation in a partially mixed estuary 1 numerical experiments are conducted to investigate how axial winds affect stratification and circulation in the partially mixed estuary of chesapeake bay in the absence of rotational effects stratification in the estuary decreases following both down estuary and up estuary winds but stratification experiences larger reduction and takes longer to recover under up estuary winds in the presence of rotational effects wind driven lateral circulations cause the lateral straining of density field and weaken the shear in the along channel flows under the down estuary winds a counterclockwise lateral circulation steepens isopycnals in the cross channel sections while the coriolis force acting on it decelerates the downwind current in the surface layer and the upwind directed current in the bottom layer under the up estuary winds a clockwise lateral circulation flattens isopycnals in the cross channel sections and reduces the shear between the surface and bottom currents hence in the presence of rotational effects the lateral straining offsets the effects of longitudinal straining such that the asymmetry in stratification reduction is significantly reduced between the down estuary and up estuary winds regime diagrams based on wedderburn w and kelvin ke numbers are constructed to summarize the net effects of winds on estuarine stratification during both wind perturbation and postwind adjustment periods

the relationship between the southern hemisphere annular mode and antarctic peninsula summer temperatures analysis of a high resolution model climatology abstract the large regional summer warming on the east coast of the northern antarctic peninsula ap which has taken place since the mid 1960s has previously been proposed to be caused by a trend in the southern hemisphere annular mode sam the authors utilize a high resolution regional atmospheric model climatology 14 km grid spacing to study the mechanisms that determine the response of the near surface temperature to an increase in the sam t sam month to month variations in near surface temperature and surface pressure are well represented by the model it is found that north of 68 s t sam is much larger on the eastern lee side than on the western windward side of the barrier this is because of the enhanced westerly flow of relatively warm air over the barrier which warms and dries further as it descends down the lee slope the downward motion on the eastern side of the barrier causes a decrease in surface mass balance and cloud cover south of 68 s vertical deflection across

disappearance of a crater lake implications for potential explosivity at soufriere volcano st vincent lesser antilles soufriere volcano in st vincent west indies is one of the most active volcanoes in the eastern caribbean with at least six eruptions since 1718 ad the latest of which occurred in 1979 prior to the 1979 eruption the active crater hosted deep water lakes during periods of repose which were always replenished within a few years after the eruptions in 1979 the crater was filled with 108 m3 of fragmental material and despite constant precipitation has remained virtually dry ever since with the exception of a small shallow pond a resistivity survey was conducted in july 2006 to investigate groundwater occurrence in the crater results from the resistivity data inversion on several 2 d profiles show a shallow horizontal conductor across the crater floor consistent with a water saturated aquifer they also show that the post 1979 pond currently present in the crater lake is in fact an outcropping part of the groundwater water reservoir the reservoir water table is 28 m above the pre 1979 lake level and reflects mass equilibrium in the system where constant seepage underground balances the meteoric recharge we suggest that the groundwater body extends at depth to the bottom of the pre 1979 crater lake either due to a significant structural discontinuity or because of a reduction of permeability at depth the estimated maximum volume of water stored underground is 10 30 106 m3 and energy considerations indicate that 2 4 7 3 1010 kg of magma would potentially be sufficient to vaporise the whole groundwater body this amount of magma represents only 13 41 of the mass erupted during the last eruption in 1979 which was the smallest of the past 3 eruptions 1902 1971 72 1979 since explosive phreatic or phreatomagmatic eruptions at soufriere seem to be linked to magma water interaction within confined space the results from this survey suggests that phreatic or phreatomagmatic activity is a distinct possibility during future magma intrusion in the summit area despite the apparent disappearance of water in the summit crater

the influence of lateral advection on the residual estuarine circulation a numerical modeling study of the hudson river estuary abstract in most estuarine systems it is assumed that the dominant along channel momentum balance is between the integrated pressure gradient and bed stress scaling the amplitude of the estuarine circulation based on this balance has been shown to have predictive skill however a number of authors recently highlighted important nonlinear processes that contribute to the subtidal dynamics at leading order in this study a previously validated numerical model of the hudson river estuary is used to examine the forces driving the residual estuarine circulation and to test the predictive skill of two linear scaling relationships results demonstrate that the nonlinear advective acceleration terms contribute to the subtidal along channel momentum balance at leading order the contribution of these nonlinear terms is driven largely by secondary lateral flows under a range of forcing conditions in the model runs the advective acceleration terms nearly always act in concert with the baroclinic pressure gradie

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

subsurface fluid distribution and possible seismic precursory signal at the salse di nirano mud volcanic field italy mud volcanoes are geological systems often characterized by elevated fluid pressures at depth deviating from hydrostatic conditions this near critical state makes mud volcanoes particularly sensitive to external forcing induced by natural or man made perturbations we used the nirano mud volcanic field as a natural laboratory to test pre and post seismic effects generated by distant earthquakes we first characterized the subsurface structure of the nirano mud volcanic field with a geoelectrical study next we deployed a broad band seismic station in the area to understand the typical seismic signal generated by the mud volcano seismic records show a background noise below 2 s sometimes interrupted by pulses of drumbeat like high frequency signals lasting from several minutes to hours to date this is the first observation of drumbeat signal observed in mud volcanoes in 2013 june we recorded a m4 7 earthquake that occurred approximately 60 km far from our seismic station according to empirical estimations the nirano mud volcanic field should not have been affected by the m4 7 earthquake yet before the seismic event we recorded an increasing amplitude of the signal in the 10 20 hz frequency band the signal emerged approximately two hours before the earthquake and lasted for about three hours our statistical analysis suggests the presence of a possible precursory signal about 10 min before the earthquake

northern hemisphere rossby wave initiation events on the extratropical jet a climatological analysis abstracta climatology of rossby wave initiation rwi events on the northern hemisphere mid latitude jet is compiled by applying an objective rwi identification algorithm to the era interim re analysis dataset in winter rwi events occur most frequently over the northwestern pacific and less often over the north atlantic in summer the total number of rwi events is lower than in winter and the north pacific rwi region shifts towards the tibetan plateau composite analysis of the large scale flow prior to during and after winter north pacific rwi events shows an upstream wave train propagating across asia on the arctic waveguide prior to rwi the composite wave forms on a relatively weak zonal jet streak exhibits a baroclinic structure and is strongly amplified by latent heat release in the warm conveyor belt of a deepening surface cyclone moreover the wave forms in a region of large scale upper level deformation upstream of a pre existing ridge further active tropical convection affects the longit

the impact of wave packets propagating across asia on pacific cyclone development abstract in this paper ecmwf 40 yr reanalysis data have been examined to study the influence of upper level wave packets propagating across asia into the pacific on surface cyclone development over the pacific previous studies have shown that in winter wave packets propagate across asia over two branches a northern branch over siberia and a southern branch along the subtropical jet across southern asia results presented here show that subsequent to the presence of wave packets on either branch the frequency of occurrence of deep cyclones defined as cyclones with central pressure below 960 hpa as well as explosively deepening cyclones those with a deepening rate of 1 bergeron or more are significantly enhanced this enhancement also clearly follows the wave packet eastward as it propagates across the pacific wave packets from the two branches are found to interfere with each other such that if wave packets of the appropriate configuration are present on both the northern and southern branch s

bathymetric controls on sediment transport in the hudson river estuary lateral asymmetry and frontal trapping 1 analyses of field observations and numerical model results have identified that sediment transport in the hudson river estuary is laterally segregated between channel and shoals features frontal trapping at multiple locations along the estuary and varies significantly over the spring neap tidal cycle lateral gradients in depth and therefore baroclinic pressure gradient and stratification control the lateral distribution of sediment transport within the saline estuary sediment fluxes are strongly landward in the channel and seaward on the shoals at multiple locations bottom salinity fronts form at bathymetric transitions in width or depth sediment convergences near the fronts create local maxima in suspended sediment concentration and deposition providing a general mechanism for creation of secondary estuarine turbidity maxima at bathymetric transitions the lateral bathymetry also affects the spring neap cycle of sediment suspension and deposition in regions with broad shallow shoals the shoals are erosional and the channel is depositional during neap tides with the opposite pattern during spring tides narrower deeper shoals are depositional during neaps and erosional during springs in each case the lateral transfer is from regions of higher to lower bed stress and depends on the elevation of the pycnocline relative to the bed collectively the results indicate that lateral and along channel gradients in bathymetry and thus stratification bed stress and sediment flux lead to an unsteady heterogeneous distribution of sediment transport and trapping along the estuary rather than trapping solely at a turbidity maximum at the limit of the salinity intrusion

chemical and isotopic composition of fumarolic gases and the so2 flux from volcan de colima mexico between the 1994 and 1998 eruptions volcan de colima is the most active volcano in mexico including a significant effusive eruption in 1991 and a weak explosive event in 1994 geochemical monitoring of the volcano started in january 1996 with collection of fumarolic gases approximately every 3 months from two sites in the summit crater z3 800 c and z2 400 c chemical compositions of volcanic gases from the z2 fumarole showed a peak in s cl in the middle of 1997 14 15 months before the start of the 1998 lava eruption high temperature volcanic vapors from z3 changed progressively in water isotopic composition and showed a weak trend of increasing hcl hf and a peak in s cl at the same time starting from the summer of 1997 the volcanic water became gradually enriched in deuterium which probably indicated an increasing contribution from deep less degassed magma a negative correlation between d and cl content for the z3 fumarolic gases is explained by shallow degassing of the colima hot lava plug this hypothesis is consistent with published data on cl contents and solubilities in magmas and supported by the observed positive trends of s cl and hcl hf with d for the z3 fumarole until september 1998 the so2 flux from the volcano was at a low level 100 tons day and often below the detection limit of the instrument 30 tons day a sharp increase in the so2 flux was recorded 1 month before the eruption started it jumped from 400 50 tons day to 1600 tons day 2 days before new lava emerged on 20 november 1998 the so2 flux correlated well with seismicity

volatilization transport and sublimation of metallic and non metallic elements in high temperature gases at merapi volcano indonesia abstract condensates silica tube sublimates and incrustations were sampled from 500 800 c fumaroles and lava samples were collected at merapi volcano indonesia in jan feb 1984 with respect to the magma merapi gases are enriched by factors greater than 105 in se re bi and cd 104 105 in au br in pb and w 103 104 in mo cl cs s sn and ag 102 103 in as zn f and rb and 1 102 in cu k na sb ni ga v fe mn and li the fumaroles are transporting more than 106 grams day g d of s cl and f 104 106 g d of al br zn fe k and mg 103 104 g d of pb as mo mn v w and sr and less than 103 g d of ni cu cr ga sb bi cd li co and u with decreasing temperature 800 500 c there were five sublimate zones found in silica tubes 1 cristobalite and magnetite first deposition of si fe and al 2 k ca sulfate acmite halite sylvite and pyrite maximum deposition of cl na k si s fe mo br al rb cs mn w p ca re ag au and co 3 aphthitalite k na sulfate sphalerite galena and cs k sulfate maximum deposition of zn bi cd se and in higher deposition of pb and sn 4 pb k chloride and na k fe sulfate maximum deposition of pb sn and cu and 5 zn cu and k pb sulfates maximum deposition of pb sn ti as and sb the incrustations surrounding the fumaroles are also chemically zoned bi cd pb w mo zn cu k na v fe and mn are concentrated most in or very close to the vent as expected with cooling atmospheric contamination and dispersion the highly volatile elements br cl as and sb are transported primarily away from high temperature vents ba si p al ca and cr are derived from wall rock reactions incomplete degassing of shallow magma at 915 c is the origin of most of the elements in the merapi volcanic gas although it is partly contaminated by particles or wall rock reactions the metals are transported predominantly as chloride species as the gas cools in the fumarolic environment it becomes saturated with sublimate phases that fractionate from the gas in the order of their equilibrium saturation temperatures devolatilization of a cooling batholith could transport enough acids and metals to a hydrothermal system to play a significant role in forming an ore deposit however sublimation from a high temperature high velocity carrier gas is not efficient enough to form a large ore deposit re se cd and bi could be used as supporting evidence for magmatic fluid transport in an ore deposit

application of the ncar regional climate model to eastern africa 2 simulation of interannual variability of short rains we have applied the ncar regcm2 to the simulation of the interannual variability of precipitation over eastern africa for the short rains season by performing a set of experiments for the years 1982 to 1993 the model reproduced the observed interannual variability of precipitation in most of the years the results show that remote factors play a dominant role in determining the precipitation anomalies interannual variability of precipitation over tanzania is closely related to el nino events in their mature phase and sea surface temperature sst anomalies over the indian and atlantic oceans the southward shift of the arabian high results in a southward shift of the zonal component of the intertropical convergence zone itcz which is responsible for early onset of the rainy season e g 1982 and 1986 the enhanced st helena high and weaker mascarene high lead to the eastward shift of the meridional branch of the itcz for the wet years model simulations confirmed a strong positive correlation between precipitation anomalies over lake victoria and the warm el nino southern oscillation events by which enhanced moist westerly flow from the atlantic ocean and the mainly easterly flow from the indian ocean converge over lake victoria during wet years the interannual variability of precipitation over lake victoria and the western kenya highlands wkh are strongly coupled positive precipitation anomalies over the wkh region are usually associated with weaker arabian high and mascarene high which weaken the large scale divergence over the wkh region and favor the development of convection the interannual variability of precipitation over eastern kenya highlands ekh is not directly related to the el nino events but the association with a warm sst anomaly pattern over the western indian ocean is evident during wet years an el nino signal is however evident for wet years over the turkana channel warm sst anomalies over the northern indian ocean contribute enhanced water vapor transport over the region

why precipitation is mostly concentrated over islands in the maritime continent abstract high resolution observations and regional climate model simulations reveal that precipitation over the maritime continent is mostly concentrated over islands analysis of the diurnal cycles of precipitation and winds indicates that this is predominantly caused by sea breeze convergence over islands reinforced by mountain valley winds and further amplified by the cumulus merger processes comparison of a regional climate model control simulation to a flat island run and an all ocean run demonstrates that the underrepresentation of islands and terrain in the maritime continent weakens the atmospheric disturbance associated with the diurnal cycle and hence underestimates precipitation the implication of these regional modeling results is that systematic errors in coarse resolution global circulation models probably result from insufficient representation of land sea breezes associated with the complex topography in the maritime continent it is found that precipitation in the maritime continent

mud volcanism an updated review abstract mud volcanism or sedimentary volcanism represents one of the most intriguing phenomena of the earth s crust with important implications in energy resource exploration seismicity geo hazard and atmospheric budget of greenhouse gases since the first review papers were issued at the beginning of 2000s a large amount of new geological geophysical and geochemical data has been acquired which clarified ambiguous concepts and significantly improved our knowledge of mud volcanism here we offer an updated review of the knowledge and implications of mud volcanoes with emphasis on the terminology used to describe different processes and structures the physical chemical and morphological characteristics of the several fluid emission structures the chemical properties of the released fluids in particular the molecular and isotopic composition of the gas the mud volcano formation dynamics and the several implications for petroleum exploration geo hazards and global atmospheric methane budget this review integrates new fluids data collected in azerbaijan and is complemented with field observations from various mud volcano provinces worldwide although the total number of mud volcanoes on earth is still uncertain 600 main onshore structures with a large variety in shapes and sizes are documented in recent global data sets and several thousand are assumed to exist in the oceans it is clear that a mud volcanoes are broadly distributed throughout the globe in active margins compressional zones of accretionary complexes thrust and overthrust belts passive margins deep sedimentary basins related to active plate boundaries as well as delta regions b they are specifically located in hydrocarbon bearing basins along anticline axes strike slips and normal faults and fault related folds in petroleum systems c they represent a specific category of natural gas oil seepage manifestation often related to deep and pressurised reservoirs d the main engine driving mud volcanism is given by a combination of gravitative instability of shales and fluid overpressure build up followed by hydrofracturing e hydrocarbons are generally of thermogenic origin while microbial gas is released in only a few cases mud volcanism on other planets e g mars and titan and microbial activity associated with gas seepage represent emerging issues and opportunities for future research

a uniform and variable resolution stretched grid gcm dynamical core with realistic orography the impact of introducing a realistic orographic forcing into a uniform and variable resolution stretched grid gcm dynamical core is investigated by performing long term and medium range integrations comparisons are made between various stretched grid simulations and a control that consists of a uniform grid integration at high resolution these comparisons include those where the orography has and has not been filtered to eliminate small scale noise results from the region of interest with highest resolution show that 1 the stretched grid gcm provides an efficient downscaling over the area of interest that is it properly simulates not only largescale but also mesoscale features and 2 the introduction of orography has a greater impact than the effect of stretching results presented here suggest that dynamical core integrations with both uniform and stretched grids should consider orographic forcing as an integral part of the model dynamics

lateral variability of sediment transport in the delaware estuary lateral processes contribute significantly to circulation and material transport in estuaries the mechanisms controlling transport may vary spatially such that shallow and deep regions of an estuary contribute differently to the total transport an observational study was conducted to explore the importance of lateral variability in sediment transport mechanisms in the delaware estuary seven moorings were deployed across the channel in the region of the estuarine turbidity maximum etm zone from april to august 2011 time series of along channel sediment transport reveal a consistent pattern of sediment export across the entire estuary during periods of high river discharge followed by a transition to import within the channel and export on the flanks during low river flow there is a persistent divergence of across channel sediment fluxes on the delaware side where sediment from the flank is transported toward both the channel and wetland coast decomposition of the fluxes highlight that across channel sediment transport is driven by mean lateral circulation whereas along channel transport is driven primarily by mean advection with tidal pumping contributing to about 30 of total transport the spatial and temporal variability of mean advection and tidal pumping were generally complementary with both contributing to the observed sediment transport pathways tidal pumping linked to tidal asymmetries in stratification and sediment resuspension was shown to drive both ebb driven export and flood driven import depending on the tidal variability of stratification the spatiotemporal patterns of sediment transport highlight the three dimensional structure of the etm and shed light on the variability of sediment transport mechanisms

influences of north pacific ocean domain extent on the western u s winter hydroclimatology in variable resolution cesm author s rhoades am jones ad o brien ta o brien jp ullrich pa zarzycki cm abstract 2020 american geophysical union all rights reserved variable resolution global climate models vrgcms are a dynamical downscaling method that can reach spatiotemporal scales needed for regional climate assessments over the years several users of vrgcms have assumed where the location and extent of the refinement domain should be based on knowledge of the prevailing storm tracks and resolution dependence of important regional climate processes e g atmospheric rivers ars and orographic uplift but the effect of high resolution domain size and extent on the simulation of downstream hydroclimatic phenomena has not been systematically evaluated here we use variable resolution in the community earth system model vr cesm to perform such a test to do this three vr cesm grids were generated that span the entire two thirds and one third of the north pacific and evaluated for a 30 year climatology using atmospheric model intercomparison project protocols simulations are compared with reanalysis products offshore fifth generation of the european centre for medium range weather forecasts atmospheric reanalysis era5 and onshore livneh 2015 https doi org 10 1038 sdata 2015 42 and parameter elevation regressions on independent slopes model prism of the western united states the westward expansion of refinement domain influenced integrated vapor transport ivt which was generally high biased but minimally impacted ar characteristics due to slight differences in landfalling ar counts in the western united states california winter precipitation generally improved with westward expansion of the refinement domain western u s mountain snowpack and surface temperatures were insensitive to refinement domain size and were more influenced by changes in topographic resolution and or land surface model version given minimal dependence of simulated western u s hydroclimate on refinement domain size over the north pacific we advise future vr cesm studies to focus grid resolution on better resolving land surface heterogeneity

adventive hydrothermal circulation on stromboli volcano aeolian islands italy revealed by geophysical and geochemical approaches implications for general fluid flow models on volcanoes on march 15th 2007 a paroxysmal explosion occurred at the stromboli volcano this event generated a large amount of products mostly lithic blocks some of which impacted the ground as far as down to 200 m a s l about 1 5 km far away from the active vents two days after the explosion a new vapour emission was discovered on the north eastern flank of the volcanic edifice at 560 m a s l just above the area called nel cannestra this new vapour emission was due to a block impact in order to investigate the block impact area to understand the appearance of the vapour emission we conducted on may 2008 a multidisciplinary study involving electrical resistivity tomography ert ground penetrating radar gpr self potential sp co2 soil diffuse degassing and soil temperature surveys this complementary data set revealed the presence of an anomalous conductive body probably related to a shallow hydrothermal level at about 10 15 m depth more or less parallel to the topography it is the first time that such a hydrothermal fluid flow with a temperature close to the water boiling point 76 c has been evidenced at stromboli at this low elevation on the flank of the edifice the ert results suggest a possible link between 1 the main central hydrothermal system of stromboli located just above the plumbing system feeding the active vents with a maximum of subsurface soil temperature close to 90 c and limited by the neostromboli summit crater boundary and 2 the investigated area of nel cannestra at 500 m a s l a buried eruptive fissure active 9 ka ago in parallel sp and co2 soil diffuse degassing measurements suggest in this sector at slightly lower elevation from the block impact crater a magmatic and hydrothermal fluid rising system along the n41 regional fault a complementary ert profile on may 2009 carried out from the neostromboli crater boundary down to the block impact crater displayed a flank fluid flow apparently connected to a deeper system the concept of shallow hydrothermal level have been compared to similar ert results recently obtained on mount etna and la fossa cone of vulcano this information needs to be taken into account in general fluid flow models on volcanoes in particular peripheral thermal waters as those bordering the north eastern coast of stromboli could be contaminated by hydrothermal and magmatic fluids coming from regional faults but also from the summit

developing wave packets in the north pacific storm track developing wave packets in the western north pacific storm track are diagnosed observationally an abrupt upstream edge to baroclinic wave activity over the western north pacific facilitates comparisons between the observational results and previous theoretical predictions on the spatiotemporal evolution of an impulse disturbance results show that surface cyclogenesis events are preceded by a sharply peaked wave packet that originates poleward of the himalaya plateau and develops rapidly across the north pacific to north america composite wave packet structure is broadly consistent with linear theory for idealized models such as eady s the longitude height structure of the mature packet reveals deep growing waves with horizontal wavelengths of approximately 4000 km near the packet peak downstream from the peak amplitude decays exponentially and wavelength decreases approximately linearly to about 2500 3000 km at the leading edge meridional potential vorticity gradients are concentrated near the tropopause in contrast to linear theory the packets show an abrupt upstream edge and no evidence of upstream development as the packet travels through the along stream variations of the pacific jet stream the packet peak and leading edge group velocity vary these accelerations change the packet length and suggest that the pacific jet may act to focus the packets a sample of north atlantic storm track events reveals similar results and suggests that the atlantic storm track is often seeded by wave packets that originate over the western north pacific ocean in contrast atlantic packets refract equatorward and become trapped on the subtropical jet to the south of himalaya plateau suggesting perhaps less potential for seeding disturbances in the pacific storm track

simulations of the indian summer monsoon using a nested regional climate model domain size experiments seasonal simulations of the indian summer monsoon using a 50 km regional climate model rcm are described results from three versions of the rcm distinguished by different domain sizes are compared against those of the driving global general circulation model agcm precipitation over land is 20 larger in the rcms due to stronger vertical motions arising from finer horizontal resolution the resulting increase in condensational heating helps to intensify the monsoon trough relative to the agcm the rcm precipitation distributions show a strong orographically forced mesoscale component similar in each version this component is not present in the agcm the rcms produce two qualitatively realistic intraseasonal oscillations isos associated respectively with monsoon depressions which propagate northwestward from the bay of bengal and repeated northward migrations of the regional tropical convergence zone the rcm simulations are relatively insensitive to domain size in several respects 1 the mean bias relative to the agcm is similar for all three domains 2 the variability simulated by the rcm is strongly correlated with that of the driving agcm on both daily and seasonal time scales even for the largest domain 3 the mesoscale features and isos are not damped by the relative proximity of the lateral boundaries in the version with the smallest domain results 1 and 2 contrast strongly with a previous study for europe carried out with the same model probably due to inherent differences between mid latitude and tropical dynamics

convergence of lateral flow along a coastal plain estuary a set of velocity profiles obtained in the james river estuary with an acoustic doppler current profiler was used in combination with the results of an analytic tidal model to depict the appearance of surface lateral flow convergences v y during both flood and ebb stages of the tidal cycle the bathymetry of the estuary was characterized by a main channel and a secondary channel separated by relatively narrow shoals lateral surface flow convergences appeared over the edges of the channels and were produced by the phase lag of the flow in the channel relative to the shoals flood convergences developed in the late tidal stages and ebb convergences appeared soon after maximum currents most of these convergences caused fronts in the density field and flotsam lines that also appeared over the edges of the channel and that lasted 2 hours the transverse flows associated with the convergences were mostly in the same direction throughout the water column in fact the vertically averaged flow produced the same convergence patterns as those near the surface the analytic tidal model reproduced well the timing and location of the convergences as observed in the james river model results with different bathymetry emulated the results in other estuaries e g axial convergence in an estuary with a channel in the middle this work showed that the strength of lateral convergences along the estuary was proportional to the tidal amplitude and the channel steepness it also suggested that the convergences were produced mainly by the tidal flow interacting with the channel shoal bathymetry i e that they did not require the presence of density gradients however the analytic model underestimated the magnitude of the convergences and did not account for vertical circulations associated with fronts the formation of fronts resulted from the interaction of the tidal flow with the bathymetry and the density field

influence of lateral advection on residual currents in microtidal estuaries abstract the influence of nonlinear lateral advection on estuarine exchange flow is examined with a scaling analysis and eight groups of idealized numerical experiments nonlinear lateral advection is related to the linkage between lateral circulation and the lateral shear of the along estuary flow the relative contribution of lateral advection to the overall dynamics of a microtidal estuary is found to be a function of width and depth and of vertical mixing lateral advection is dynamically important in narrow and deep estuaries particularly under relatively weak vertical mixing the relative importance of lateral advection and the earth s rotation on estuarine dynamics can be evaluated in terms of the nondimensional rossby and ekman numbers ro and ek lateral advection is most effective at large ro and small ek and is negligible at small ro and large ek as expected the earth s rotation is most significant at small ro and ek and is negligible at large ro and ek under the influence of lateral adv

application of scale selective data assimilation to tropical cyclone track simulation tropical cyclone track is strongly controlled by the large scale environmental circulation in limited area models lams driven by global analyses or forecasts through a conventional lateral boundary nesting approach the global analyses are often distorted by the use of sponge zone or interpolation when they are passed into the lam in this study a dynamical downscaling approach based on scale selective data assimilation ssda is applied to a limited area numerical weather prediction model with emphasis on tropical cyclone track simulation the idea of the ssda approach is to drive the lam not only from the lateral boundary but also from the model domain interior the large scale flow from global analyses or forecasts is assimilated into the regional model using 3 d variational data assimilation the large scale features in the lam are thus constrained to follow the global analyses while allowing the regional model itself to develop the regional and small scale characteristics the results from the case study of hurricane katrina 2005 show that both large and small scale flows in the regional model benefited from the ssda approach leading to an improvement in the accuracy of storm track simulation when provided with an accurate large scale circulation from global analyses in addition the ssda procedure is shown to be an effective method to construct a nested grid regional modeling system that reduces model sensitivity to model domain geometry and location

the relationship between boundary layer stability and cloud cover in the post cold frontal region using nasa aqua modis and airs data the relationship between low level cloud cover cloud top below the 700 hpa level and boundary layer stability is explored in post cold frontal conditions a linear relationship is found between seasonal cloud cover and two separate measures of inversion strength the lower tropospheric stability lts and the estimated inversion strength eis for two specific regions in the north atlantic and pacific in quiescent and weakly subsiding conditions the relationship barely changes when considering dynamically active and subsiding post cold frontal conditions for the same regions to explore the generality of this result and increase sample size cold front centered composites of cloud cover and stability are constructed the northern and southern hemisphere seasonal cloud cover and stability distributions in the post cold frontal regions are then compared a fairly good correlation between cloud cover and eis is found in both hemispheres across all seasons suggesting that a linear relationship between cloud cover and inversion strength proposed for quiescent conditions exists also in more dynamically active subsiding post cold frontal conditions however for a given season and hemisphere the correlation between cloud cover and eis degrades in post cold frontal regions especially in the northern hemisphere at these scales other large scale factors tend to correlate better with cloud cover

baffin island snow extent sensitivity insights from a regional climate model 1 recent modeling efforts suggest that the little ice age lia onset could be explained by a series of four large decadally spaced volcanic eruptions at that time glaciers on baffin island advanced and did not retreat until the past century perhaps due to arctic and north atlantic ocean sea ice feedbacks to try to determine what parameters sustain snow cover we investigate the relative impacts of changes in radiation and advection on minimum summer snow extent over baffin island we used the weather research and forecasting wrf model to run eight 6 month long april september 10 km resolution simulations in which we varied boundary condition temperatures solar radiation and sea ice cover although the control run underestimated cloud cover and thus produced an exaggerated diurnal 2 m temperature cycle the relative changes of snow extent show that wrf accurately simulates snow expansion into the same regions as during the lia with an average temperature decrease from current temperatures by 3 9 1 1 k it only requires one season for the model to lower the snowline by comparable elevation changes seen during the descent into the lia wrf s maximum snow line sensitivity is 7 k km within the range of the typically assumed lapse rate of 5 7 k km in the canadian arctic thus if a shift in the arctic climate greatly expanded sea ice coverage following large volcanic eruptions this would have been enough to perpetuate an ice sheet on baffin island throughout the lia

the importance of soil type contrast in modulating august precipitation distribution near the edwards plateau and balcones escarpment in texas the balcones escarpment in central texas is a sloped region between the edwards plateau and the coastal plain the metropolitan areas located along the balcones escarpment e g san antonio austin and dallas fort worth are prone to heavy rain and devastating flood events while the associated hydrological issues of the balcones escarpment have been extensively studied the meteorological impacts of the edwards plateau and balcones escarpment are not well understood the indeterminate impacts of the thermal and dynamic effects of the edwards plateau on august climatological precipitation are investigated in this study using the multi sensor stage iv precipitation data high resolution dynamic downscaling and short term sensitivity simulations analysis results indicate that the total august precipitation east of the balcones escarpment is suppressed and precipitation over the eastern part of the edwards plateau is enhanced locally initiated moist convection in the afternoon contributes most to the total precipitation during august in the region the dynamic downscaling output captures the spatial pattern of afternoon precipitation which is well aligned with the simulated upward motions the clay based soil types that dominate the edwards plateau have great potential to retain soil moisture and limit latent heat fluxes consequently leading to higher sensible heat flux than over the plain to the east as a result vertical motion is induced triggering the afternoon moist convection over the edwards plateau under favorable conditions in comparison the sloping terrain plays a smaller role in triggering the convection short term sensitivity simulations for a clear day confirm and further prove such a diagnosis

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

intrusive and basement rock sources of lead in hydrothermal systems of the taupo volcanic zone new zealand abstract the taupo volcanic zone is a complex volcanic tectonic region over 250 km long corresponding to the volcanic arc of the taupo hikurangi subduction system volcanism is dominantly rhyolitic with minor amounts of andesite dacite and basalt the volcanics overlie a downfaulted basement of mesozoic metasediment waipapa and torlesse terranes over twenty major geothermal systems are active related to the young volcanism samples of sulfides galena sphalerite chalcopyrite and pyrite from five of the geothermal systems were collected from drill core and their pb isotopic compositions measured representative fresh samples from all volcanic and basement rock types of the region were also analyzed and show a range of values by which they may be distinguished sulfides from the broadlands and waiotapu geothermal systems are homogeneous in their pb isotopic compositions with values similar to the average for the fresh rhyolites and andesites the results indicate that the source of pb and possibly other metals in the broadlands and waiotapu hydrothermal fluids is related to the parent magma of the volcanics a magmatic fluid could be the source consistent with independent geochemical and isotopic evidence for other magmatic fluid derived components at broadlands and to a lesser extent at waiotapu which are both anomalously mineralized in precious and base metals in contrast pyrite pb from the unmineralized kawerau geothermal system has isotopic compositions which vary over a range similar to that of the underlying waipapa metasedimentary basement present at depths of only 1000 m this observation suggests that the pb at kawerau was mainly leached from the basement rocks with a component of isotopically homogenous magma related pb not present in the hydrothermal fluids isotopic compositions of pb from the unmineralized wairakei and mokai systems are intermediate between the broadlands and kawerau examples these data are interpreted to result from leaching of pb from both the basement and volcanic rocks consistent with the thick at least 3 km sequence of volcanics in the center of the zone where wairakei and mokai are located these results suggest that epithermal gold prospects may be distinguished on the basis of their pbisotopic signature those exhibiting a homogeneous and magmatic signature have a higher potential to contain ore all else being equal because of the potential for higher magmatic derived metal concentrations in the hydrothermal fluid this suggestion appears to be applicable only to dilute hydrothermal systems perhaps because the low salinity precludes leaching as an effective process to solubilize metals

effects of quasi stationary large scale anomalies on some mesoscale features associated with the 1993 flood a regional model simulation we investigate the effect of quasi stationary large scale anomalies on mesoscale factors contributing to the 1993 u s midwest flood by performing 30 day simulations with a mesoscale model the contributions of anomalous mesoscale features to the flood were quantified by contrasting model integrations forced by initial and lateral boundary conditions with and without large scale anomalous stationary waves that are believed to have been responsible for the flood supplementing previous investigations the present study finds the following 1 the large scale anomalies produced environmental conditions that favored a generation of mcc like systems rather than individual convective cells or squall lines that would have produced less precipitation over large areas ambient conditions favoring mesoscale convective complex mcc include an intensified east west orientation of quasistationary fronts weaker upper tropospheric inertial stability and a strong low level jet llj 2 the anomalous ageostrophic wind component to the far south of the flood region texas area and geostrophic wind component over the flood region bridged together to form an extended moisture conveyer that sustained the long lasting 1993 flood

the role of advection straining and mixing on the tidal variability of estuarine stratification abstractdata from the hudson river estuary demonstrate that the tidal variations in vertical salinity stratification are not consistent with the patterns associated with along channel tidal straining these observations result from three additional processes not accounted for in the traditional tidal straining model 1 along channel and 2 lateral advection of horizontal gradients in the vertical salinity gradient and 3 tidal asymmetries in the strength of vertical mixing as a result cross sectionally averaged values of the vertical salinity gradient are shown to increase during the flood tide and decrease during the ebb only over a limited portion of the cross section does the observed stratification increase during the ebb and decrease during the flood these observations highlight the three dimensional nature of estuarine flows and demonstrate that lateral circulation provides an alternate mechanism that allows for the exchange of materials between surface and bottom waters even when direct turbu

geochemical and geo electrical study of mud pools at the mutnovsky volcano south kamchatka russia behavior of elements structures of feeding channels and a model of origin this study presents data on the geochemical composition of boiling mud pools at the mutnovsky volcano the physicochemical characteristics of the pools and the concentrations of major minor and trace elements in pool solutions vary widely a comparison of the geochemical compositions of host rocks and solutions indicates that leaching from rocks is not the only source of chemicals in thermal solutions geophysical studies reveal the inner structure of thermal fields which reflect the shapes of the underground reservoirs and feed channels using geophysical methods electrical resistivity tomography and frequency domain investigations it was shown that the vertical structure and complex geochemical zonation of the feed channels leads to a high contrast in the compositions of the mud solutions these findings answer questions about the origin and composition of surface manifestations to elucidate the mechanisms of solution formation an attempt was made to describe the magmatic fluid evolution and the resulting mixing of waters by physical and mathematical models the model illustrates fluid migration from a magma chamber to the surface it is shown that the formation of brines corresponding to the mud pool composition is possible during secondary boiling

absolute and convective instability of the african easterly jet abstractthe stability of the african easterly jet aej is examined using idealized numerical simulations it is found that a zonally homogeneous representation of the aej can support absolute instability in the form of african easterly waves aews this finding is verified through a local energy budget which demonstrates the presence of both upstream and downstream energy fluxes these energy fluxes allow unstable wave packets to spread upstream and downstream relative to their initial point of excitation this finding is further verified by showing that the ground relative group velocity of these wave packets has both eastward and westward components in contrast with normal mode instability theory which emphasizes wave growth through energy extraction from the basic state the life cycle of the simulated aews is strongly governed by energy fluxes convergent fluxes at the beginning of the aew storm track generate new aews whereas divergent fluxes at the end of the storm track lead to their decay i

geochemistry mineralogy and chemical modeling of the acid crater lake of kawah ijen volcano indonesia the kawah ijen volcano with a record of phreatic eruptions has its 1000 m wide crater filled with a lake that has existed for at least one century at present the lake waters are hot t 37 c strongly mineralized tds 105 g l and extremely acidic ph 0 4 by its volume the javanese lake is probably the largest accumulation in the world of such acidic waters mineralogy of the suspended solids within the lake waters suggests that concentrations of si ca ti and ba are controlled by precipitation of silica gypsum anatase and barite lake sediment is composed of chemical precipitates with composition similar to the suspended solids thermodynamic calculations predict that the lake waters have reached equilibrium with respect to cristobalite barite gypsum anglesite celestite and amorphous silica in agreement with the analytical observations significant concentrations of ferric iron suggest that the current lake waters are fairly oxidized sulfides are absent in the water column but are always present in the native s spherules that form porous aggregates which float on the lake the presence of native s provides direct evidence of more reduced conditions at the lake floor where h 2 s is probably being injected into the lake with progressive addition of h 2 s to the acid waters native s pyrite and enargite are theoretically predicted to be saturated reactions between upward streaming h 2 s bearing gases discharged by subaqueous fumaroles and metals dissolved in the acidic waters could initiate precipitation of these sulfides a model of direct absorption of hot magmatic gases into cool water accounts for the extreme acidity of the crater lake results show that strongly acidic sulfate rich solutions are formed under oxidizing conditions at high gas water ratios reactions between the acidic fluids and the ijen andesite were modeled to account for elevated cation concentrations in lake water current concentrations of conservative rockforming elements are produced by dissolution of approximately 60 g of andesite per kg of acid solution complete neutralization of the acid lake waters by reaction with the wallrock produces a theoretical alteration assemblage equivalent to that observed in volcano hosted acid sulfate epithermal ore deposits

lateral entrapment of sediment in tidal estuaries an idealized model study two physical mechanisms leading to lateral accumulation of sediment in tidally dominated estuaries are investigated involving coriolis forcing and lateral density gradients an idealized model is used that consists of the three dimensional shallow water equations and sediment mass balance conditions are assumed to be uniform in the along estuary direction a semidiurnal tidal discharge and tidally averaged density gradients are prescribed the erosional sediment flux at the bed depends both on the bed shear stress and on the amount of sediment available in mud reaches for resuspension the distribution of mud reaches over the bed is selected such that sediment transport is in morphodynamic equilibrium that is tidally averaged erosion and deposition of sediment at the bed balance analytical solutions are obtained by using perturbation analysis results suggest that in most estuaries lateral density gradients induce more sediment transport than coriolis forcing when frictional forces are small ekman number e 0 02 the lateral density gradient mechanism dominates and entraps sediment in areas with fresher water results also show that the lateral sediment transport induced by the semidiurnal tidal flow is significant when frictional forces are small e 0 02 model predictions are in good agreement with observations from the james river estuary

tropical rainfall measuring mission observation and regional model study of precipitation diurnal cycle in the new guinean region 1 the diurnal cycle of precipitation in the new guinean region is studied on the basis of satellite observations from tropical rainfall measuring mission trmm precipitation radar pr measurements and regional atmospheric model simulations the study focuses on the effects of both the land sea breeze and the orographic forcing on the diurnal evolution of precipitation during the rainy season january march in the region the 7 year trmm pr data composite reveals several distinct features of the precipitation diurnal cycle in the region precipitation bands develop in the inland coastal region in the late morning to early afternoon and migrate inland from both northeast and southwest sides of the new guinean island following the inland penetration of the sea breeze fronts a separate convective rainband develops over the central mountain ridge in the early afternoon as a result of the development of the upslope winds due to the elevated surface warming over the mountain in the morning hours this mountain ridge rainband intensifies and becomes the dominant rainband as the coastal rainbands associated with the sea breeze fronts weaken during the late afternoon and the early evening in the midnight to the early morning the rainband over the mountaintop weakens as downslope winds develop and splits into two rainbands propagating away from the mountain ridge one to the north and one to the south and weakens over the lowland some distance away from the coasts meanwhile a coastal rainband develops offshore on each side of the island in the late evening to midnight and remains strong through early morning before it migrates offshore as a result the rainfall rate peaks in the late afternoon to early evening in most land areas except for in the lowland regions between the coastlines and the mountain where the rainfall rate peaks during the midnight while the rainfall rate peaks in the late evening to early morning in most coastal regions offshore the distribution of the diurnal amplitude shows two maxima one over the mountains and the other in the coastal regions offshore convective rainfall rate peaks in the late afternoon while stratiform rainfall rate peaks in the midnight to early morning the latter dominates the large diurnal amplitude over the mountain areas in the early morning the above broad features are simulated reasonably well in a control experiment with a high resolution regional atmospheric model a sensitivity experiment with the terrain removed is conducted to elucidate the role of orographic forcing in the diurnal evolution of both the local circulation and rainfall patterns the results show that the orographic forcing affects the diurnal precipitation through three major processes first the orography increases the moisture convergence at low levels by blocking and deflecting the mean flow second the upslope winds help initiate convection in the afternoon at the mountaintop finally the deep convection over the mountain acts as a source of propagating gravity waves which help initiate rainbands in the coastal regions offshore in the late evening to early morning implication of the results is discussed

characteristics of wave packets in the upper troposphere part ii seasonal and hemispheric variations abstract gridded 300 hpa meridional wind data produced by the ecmwf reanalysis project were analyzed to document the seasonal and hemispheric variations in the properties of upper tropospheric wave packets the properties of the wave packets are mainly illustrated using time lagged one point correlation maps performed on based on indices that show the coherence of wave propagation as well as examination of correlation maps schematic waveguides were constructed for the summer and winter seasons of both hemispheres along which waves preferentially propagate with greatest coherence in the summers the waveguides basically follow the position of the midlatitude jets in the northern hemisphere winter the primary waveguide follows the subtropical jet over southern asia into the pacific but there is a secondary branch running across russia joining the primary waveguide near the entrance to the pacific storm track over the atlantic the waveguide passes east southeastward toward north africa then bac

type b cyclogenesis in a zonally varying flow abstract it is hypothesized that surface cyclogenesis in the northern hemisphere storm track regions can be described by the structural modification of baroclinic wave packets traversing a zonally varying flow field we test this hypothesis using a linear quasigeostrophic model with a zonally varying basic state and zonally varying ekman layer eddy viscosity at midchannel the basic state consists of a region of strong low level baroclinicity and weak ekman dissipation surrounded by regions of weak low level baroclinicity strong ekman dissipation and enhanced low level static stability eigenanalyses and initial value integrations support this model of type b cyclogenesis the results can be summarized as follows 1 a disturbance initiated upstream of the midchannel baroclinic zone rapidly evolves into a wave packet with maximum amplitude near the tropopause the wave packet undergoes a structural modification upon entering the low level baroclinic zone developing maximum amplitude at the surface t

summertime post cold frontal marine stratocumulus transition processes over the eastern north atlantic abstractmarine boundary layer mbl cloud morphology associated with two summertime cold fronts over the eastern north atlantic ena is investigated using high resolution simulations from the weat

a comparative evaluation of impact of domain size and parameterization scheme on simulation of tropical cyclones in the bay of bengal 1 a large number of processes and factors control the quality of simulations with a numerical weather prediction model and especially with mesoscale models identification and optimization of these processes are critical for improving forecast skill the importance of cumulus parameterization schemes in simulation of tropical cyclones was recognized early and a large number of studies have addressed this issue however certain other aspects have received relatively less attention in particular unlike simulation with a global circulation model a mesoscale simulation is characterized by a limited domain and hence inhomogeneous lateral boundary conditions that strongly affect the quality of the simulation in this work we investigate the relative impact of size of the model domain and the cumulus parameterization scheme on simulation of 10 cyclones over the bay of bengal during the period 1999 2009 for five domains with different spatial extents simulations were carried out for three different cumulus parameterization schemes anthes kuo grell and kain fritsch2 for each of the 10 events using the mesoscale model mm5 our results show that the size of the domain also plays an equally critical role as the parameterization scheme in simulation of maximum intensity track and spatial structure of the cyclones the impact of domain size is not linear while each domain chosen is large enough neither the largest nor the smallest domain provides the best simulation however there is consistency in the sense that a single domain emerges as best for intensity and track among the five considered while the specific conclusions may depend on the ocean basin the methodology is generic and can be applied to any ocean basin of cyclogenesis

the role of the central asian mountains on the midwinter suppression of north pacific storminess abstractthe role of the central asian mountains on north pacific storminess is examined using an atmospheric general circulation model by varying the height and the areas of the mountains a series of model integrations show that the presence of the central asian mountains suppresses the north pacific storminess by 20 30 during boreal winter their impact on storminess is found to be small during other seasons the mountains amplify stationary waves and effectively weaken the high frequency transient eddy kinetic energy in boreal winter two main causes of the reduced storminess are diagnosed first the decrease in storminess appears to be associated with a weakening of downstream eddy development the mountains disorganize the zonal coherency of wave packets and refract them more equatorward as the zonal traveling distance of wave packets gets substantially shorter downstream eddy development gets weaker second the central asian mountains suppress the global baroclinic energy conversion the decre

numerical study of convection observed during the winter monsoon experiment using a mesoscale two dimensional model abstract a two dimensional version of the pennsylvania state university mesoscale model has been applied to winter monsoon experiment data in order to simulate the diurnally occurring convection observed over the south china sea the domain includes a representation of part of borneo as well as the sea so that the model can simulate the initiation of convection also included in the model are parameterizations of mesoscale ice phase and moisture processes and longwave and shortwave radiation with a diurnal cycle this allows use of the model to test the relative importance of various heating mechanisms to the stratiform cloud deck which typically occupies several hundred kilometers of the domain frank and cohen s cumulus parameterization scheme is employed to represent vital unresolved vertical transports in the convective area the major conclusions are ice phase processes are important in determining the level of maximum large scale heating and vertical motion because there is a strong anvil componen

modeling the lateral circulation in straight stratified estuaries the dynamics of lateral circulation in an idealized straight estuary under varying stratification conditions is investigated using a three dimensional hydrostatic primitive equation model in order to determine the importance of lateral circulation to the momentum budget within the estuary for all model runs lateral circulation is about 4 times as strong during flood tides as during ebbs this flood ebb asymmetry is due to a feedback between the lateral circulation and the along channel tidal currents as well as to time varying stratification over a tidal cycle as the stratification is increased the lateral circulation is significantly reduced because of the adverse pressure gradient set up by isopycnals being tilted by the lateral flow itself when rotation is included a timedependent cross channel ekman circulation is driven and the tidally averaged bottom lateral circulation is enhanced toward the right bank when looking toward the ocean in the northern hemisphere this asymmetry in the tidally averaged bottom lateral circulation may lead to asymmetric sediment transport leading to asymmetric channel profiles in straight estuaries for the weakly stratified model run advection due to lateral currents is a dominant term in both the along channel and cross channel momentum equations over a tidal cycle and for the tidally averaged momentum equations in the tidally averaged along channel momentum equation lateral advection acts as a driving term for the estuarine exchange flow and can be larger than the along channel pressure gradient therefore it should not be ignored when estimating momentum budgets in estuaries

spectral nudging to eliminate the effects of domain position and geometry in regional climate model simulations 1 it is well known that regional climate simulations are sensitive to the size and position of the domain chosen for calculations here we study the physical mechanisms of this sensitivity we conducted simulations with the regional atmospheric modeling system rams for june 2000 over north america at 50 km horizontal resolution using a 7500 km 5400 km grid and ncep ncar reanalysis as boundary conditions the position of the domain was displaced in several directions always maintaining the u s in the interior out of the buffer zone along the lateral boundaries circulation biases developed a large scale structure organized by the rocky mountains resulting from a systematic shifting of the synoptic wave trains that crossed the domain the distortion of the large scale circulation was produced by interaction of the modeled flow with the lateral boundaries of the nested domain and varied when the position of the grid was altered this changed the large scale environment among the different simulations and translated into diverse conditions for the development of the mesoscale processes that produce most of precipitation for the great plains in the summer season as a consequence precipitation results varied sometimes greatly among the experiments with the different grid positions to eliminate the dependence of results on the position of the domain we used spectral nudging of waves longer than 2500 km above the boundary layer moisture was not nudged at any level this constrained the synoptic scales to follow reanalysis while allowing the model to develop the small scale dynamics responsible for the rainfall nudging of the large scales successfully eliminated the variation of precipitation results when the grid was moved we suggest that this technique is necessary for all downscaling studies with regional models with domain sizes of a few thousand kilometers and larger embedded in global models

inferring stress from faulting from early concepts to inverse methods abstract we review the evolution of concepts on and methods of estimating the state of stress from fault movements theories of failure in isotropic materials suggested a simple geometrical construction of optimal principal stress directions from a fault plane and its associated slip these optimal directions align shear stress and slip directions and maximize the difference between shear stress and frictional resistance on the fault plane optimal stress directions for calcite twinning are obtained by a similar construction with the difference that they maximize shear stress force representation of seismic sources independently introduced pressure p and tension t axes at positions that also maximize shear stress on both nodal planes frictional slip theory and the constraint that slip and shear stress directions be parallel allowed to address reactivation of pre existing faults this suggested that stress could also be inverted from reactivated fault and slip data or earthquake focal mechanisms early methods relied on geometrical constructions as a substitute for calculations whereas later methods relied on software as these calculations became tractable with the help of computers similar methods were developed for the inversion of stress from crystal twin gliding with non optimal geometry with a different criterion that relies on a threshold of the component of shear stress along the gliding line even though these methods seek a common stress tensor compatible with fault and slip data their main use is to separate polyphase data into homogeneous subsets and help deciphering complex tectonic histories fault and slip data can also be analyzed to constrain the strain rather than the stress tensor in most cases this involves a summation and yields an average strain for the considered rock volume stress inversion thus appears better suited for differentiating heterogeneous data whereas strain analysis appears better suited for homogenizing them