impact of atmospheric water vapor on the thermal infrared remote sensing of volcanic sulfur dioxide emissions a case study from the pu u o vent of kilauea volcano hawaii the december 18 1999 launch of nasa s terra satellite put two multispectral thermal infrared imaging instruments into earth orbit experiments with airborne instruments have demonstrated that the data from such instruments can be used to detect volcanic so2 plumes and clouds however one of the greatest challenges that will confront efforts to monitor volcanic so2 emissions from space is the need to characterize the local atmosphere in this paper we evaluate the sensitivity of the so2 retrieval procedure to our knowledge of the local atmospheric conditions we compare so2 retrievals obtained with distant radiosonde and local fourier transform infrared ftir soundings atmospheric measurements and find that the relative difference is typically 25 for ground temperature retrievals the relative difference is 1 5 these results lead us to conclude that while local measurements of atmospheric conditions are preferable useful retrievals can be obtained using atmospheric measurements from distant sites in addition we find very good agreement between so2 and ground temperature retrievals obtained from thermal infrared imagery and ftir soundings

spaceborne observations of the 2000 bezymianny kamchatka eruption the integration of high resolution aster data into near real time monitoring using avhrr abstract since its launch in december 1999 the advanced spaceborne thermal emission and reflection radiometer aster instrument has been observing over 1300 of the world s volcanoes during the day and night and at different times of the year at the onset of an eruption the temporal frequency of these regularly scheduled observations can be increased to as little as 1 3 days at higher latitudes however even this repeat time is not sufficient for near real time monitoring which is on the order of minutes to hours using poorer spatial resolution 1 km pixel instruments the eruption of bezymianny volcano kamchatkan peninsula russia in march 2000 was detected by the alaska volcano observatory avo and also initiated an increased observation frequency for aster a complete framework of the eruptive cycle from april 2000 to january 2001 was established with the advanced very high resolution radiometer avhrr data used to monitor the large eruptions and produce the average yearly background state for the volcano twenty nearly cloud free aster scenes 2 days and 18 nights show large thermal anomalies covering tens to hundreds of pixels and reveal both the actively erupting and restive background state of the volcano aster short wave infrared swir and thermal infrared tir data were also used to validate the recovered kinetic temperatures from the larger avhrr pixels as well as map the volcanic products and monitor the thermal features on the summit dome and surrounding small pyroclastic flows these anomalies increase to greater than 90 c prior to a larger eruption sequence in october 2000 in addition aster has the first multispectral spaceborne tir capability which allowed for the modeling of micrometer scale surface roughness vesicularity on the active lava dome where coupled with ongoing operational monitoring programs like those at avo aster data become extremely useful in discrimination of small surface targets in addition to providing enhanced volcanic mapping capabilities

a census of eddy activities in the south china sea during 1993 2007 1 numerous mesoscale eddies occur each year in the south china sea scs but their statistical characteristics are still not well documented a pacific basin wide three dimensional physical biogeochemical model has been developed and the result in the scs subdomain is used to quantify the eddy activities during the period of 1993 2007 the modeled results are compared with a merged and gridded satellite product of sea level anomaly by using the same eddy identification and tracking method on average there are about 32 9 2 4 eddies predicted by the model and 32 8 3 4 eddies observed by satellite each year and about 52 of them are cyclonic eddies the radius of these eddies ranges from about 46 5 to 223 5 km with a mean value of 87 4 km more than 70 of the eddies have a radius smaller than 100 km the mean area covered by these eddies each year is around 160 170 km2 equivalent to 9 8 of the scs area with water depths greater than 1000 m linear relationships are found between eddy lifetime and eddy magnitude and between eddy vertical extent and eddy magnitude showing that strong eddies usually last longer and penetrate deeper than weak ones interannual variations in eddy numbers and the total eddy occupied area indicate that eddy activities in the scs do not directly correspond to the el nino southern oscillation events the wind stress curls are thought to be an important but not the only mechanism of eddy genesis in the scs

upper layer circulation in the south china sea abstract upper layer circulation is investigated by using all available historical temperature profiles combined with climatological temperature salinity relationships in the south china sea two cyclonic eddies are revealed one is located east of vietnam called the east vietnam eddy and the other is off northwest luzon called the west luzon eddy both local ekman pumping and remotely forced basin scale circulation are important mechanisms controlling these two eddies the luzon strait transport relative to 400 db is estimated to be of the order 3 0 sv 1 sv 1 106 m3 s 1 in the mean and has a seasonal cycle dominated by the annual signal with a maximum 5 3 sv in january february and a minimum 0 2 sv in june july pressure gradients are also examined to explore the dynamics of the intrusion of waters from the pacific into the south china sea through the luzon strait

winter eddy genesis in the eastern south china sea due to orographic wind jets abstract generation of mesoscale eddies in the eastern south china sea scs in winters during august 1999 to july 2002 is studied with a reduced gravity model it is found that the orographic wind jets associated with the northeast winter monsoon and the gaps in the mountainous island chain along the eastern boundary of the scs can spin up cyclonic and anticyclonic eddies over the scs results suggest that direct wind forcing could be an important generation mechanism for the rich eddy activity in the scs and that to simulate this mechanism the resolution of the wind forcing has to be high enough to resolve the local wind jets induced by orographic effects

three long lived anticyclonic eddies in the northern south china sea 1 in august 2007 three long lived anticyclonic eddies ace1 ace2 and ace3 were detected by both satellite sea level anomaly sla map and in situ measurements in the northern south china sea scs ace3 had a two core ace3 1 and ace3 2 structure in situ stations along 18 degrees n almost cut through the centers of ace2 and ace3 2 near the centers of ace2 and ace3 2 mean temperature and sound velocity are similar to 0 65 degrees c and similar to 2 m s 1 larger than those in their surrounding areas respectively while mean salinity and density are similar to 0 02 psu and similar to 0 15 m 3 s 1 smaller than those in their surrounding areas due to downwelling near the eddy cores the depths of maximum and minimum salinity near the eddy cores are similar to 65 m and similar to 35 m larger than those in their surrounding areas the vertical depth with current speed larger than 0 05 m s 1 can reach similar to 900 m their detailed evolutionary processes were depicted based on the variation of geostrophic currents and the trajectories of five drifting buoys ace1 lasted 147 days while ace2 and ace3 lasted 168 days and 210 days respectively ace1 had a smaller mean sla 18 8 cm in its lifetime than ace2 21 8 cm and ace3 25 3 cm but had a larger negative mean vorticity 7 7 x 10 6 s 1 than ace2 7 0 x 10 6 s 1 and ace3 7 0 x 10 6 s 1 one short lived anticyclonic eddy that split from ace2 and another one that merged with ace3 both had a smaller sla negative vorticity and diameter than ace2 and ace3 respectively

a gis based method for depicting the characteristics of mesoscale eddies a case study in the northern south china sea the paper presents a geographical information system gis based method for depicting the characteristics particularly the internal structures and evolutionary processes of mesoscale eddies this was done by examining topologic relations among closed sea surface height ssh contours that were reconstructed from the naval research laboratory navy layered ocean model nlom different scenarios of the topological relations among the contour lines permitted the identification of the outermost outline of eddies and the depiction of the number of cores in each mesoscale oceanic eddy with full consideration of the internal structure of the eddies we then reconstructed the evolutionary processes of these eddies and the results were compared with empirical observations on three long lived mesoscale eddies in the northern south china sea scs tracking results were similar thereby validating our method as being efficient and robust in reconstructing mesoscale ocean eddies especially their evolutionary processes based on their internal structures

the use of multispectral thermal infrared image data to estimate the sulfur dioxide flux from volcanoes a case study from mount etna sicily july 29 1986 the authors have found that image data acquired with nasa s airborne thermal infrared multispectral scanner tims can be used to make estimates of the so sub 2 content of volcanic plumes tims image data are most applicable to the study of partially transparent so sub 2 plumes such as those released during quiescent periods or nonexplosive eruptions the estimation procedure is based on the lowtran 7 radiative transfer code which the authors use to model the radiance perceived by tims as it views the ground through an so sub 2 plume the input to the procedure includes the altitudes of the aircraft and ground the altitude and thickness of the so sub 2 plume the emissivity of the ground and altitude profiles of the atmospheric pressure temperature and relative humidity they use the tims data to estimate both ground temperatures beneath a plume and so sub 2 concentrations within a plume applying this procedure to tims data acquired over mount etna sicily on july 29 1986 the authors estimate that the so sub 2 flux from the volcano was approximately 6700 t d sup minus 1 the use of tims to study so sub 2 plumes represents a bridge between highly localized methods such as correlation spectroscopy or directmore sampling and small scale mapping techniques involving satellite instruments such as the total ozone mapping spectrometer or microwave limb sounder the authors require further airborne experiments to refine their estimation procedure this refinement is a necessary preparation for the scheduled 1998 launch of the advanced spaceborne thermal emission and reflectance radiometer which will allow large scale multispectral thermal infrared image data to be collected over virtually any volcano on earth at least once every 16 days less

generation and life cycle of the dipole in the south china sea summer circulation 1 the south china sea scs summer circulation often has a dipole structure associated with an eastward jet appearing off central vietnam the dipole has an anticyclonic eddy ae south of the jet and a cyclonic eddy ce north of it the life cycle of the dipole structure is analyzed using satellite altimetry data and a reduced gravity model on average the dipole structure begins in june peaks in strength in august or september and disappears in october the dipole evolution lags behind the basin scale wind by about 40 days and 40 days are exactly what it takes for baroclinic planetary waves to cross the southern scs our results show that the vorticity transports from the nonlinear effect of the western boundary currents are crucial for the generation of the dipole structure in addition the strength and direction of the offshore wind jet also play a significant role in determining the magnitudes and the core positions of the two concomitant eddies

diffusion reaction in a thermal gradient implications for the genesis of anorthitic plagioclase high alumina basalt and igneous mineral layering abstract piston cylinder experiments investigating the interaction between basaltic andesite melt and partially molten gabbro in a thermal gradient provide insight into melt rock reaction processes occurring during magma differentiation in the crust in two experiments juxtaposing basaltic andesite and gabbro at 0 5 gpa pressure for durations of either 13 or 26 days diffusive chemical exchange between the two materials results in mineral layering and notable mineral compositions such as anorthitic plagioclase specifically the basaltic andesite gains al2o3 mgo and cao from the gabbro and loses na2o k2o sio2 and feo to it with a plagioclase rich layer developing at the interface between the two materials in a process termed diffusion reaction the percent crystallinity of the basaltic andesite increases during the process and the plagioclase crystals within the interface region develop anorthitic cores up to an90 that abruptly shift in composition to thin rims that are in na ca exchange equilibrium with the co existing melt both the mineralogical layering and bulk compositional change occurring at the interface are reproduced in model simulations of diffusion reaction isotopic tracers 45ca 6li 84sr and 136ba initially deposited at the basaltic andesite gabbro interface in the 13 day experiment were detected in the cores of the anorthitic plagioclase after the experiment demonstrating that the melt chemically communicates with the plagioclase cores over the duration of the diffusion reaction experiment the formation of anorthitic plagioclase during diffusion reaction may explain its widespread occurrence in terrestrial volcanic rocks without requiring the presence of ultra calcic melts textures and mineralogical changes in the gabbro indicate that chemical transport occurs throughout the experiments despite temperatures at the cold end of the experimental capsule approaching 500 c for instance apatite fenis olivine and almost pure albite occur at distinct specific horizons in the gabbro within the 26 day experiment because the bulk element profiles indicating chemical transport reflect analyses of almost completely solid gabbro equilibration between minerals and fluids melts must be rapid the overall effect of the diffusion reaction process is to make an ascending magma more primitive in composition and in this case produce anorthitic plagioclase while making surrounding crustal wall rocks more evolved several observations within igneous rocks support the occurrence of this process suggesting that the genesis of porphyritic high alumina basalt ubiquitously observed at convergent margins could reflect a diffusion reaction process in the crust

spatial structure of anticyclonic eddies in the algerian basin mediterranean sea analyzed using the okubo weiss parameter abstract three algerian eddies open sea big anticyclonic eddies in the algerian basin western mediterranean sea are studied in detail using altimetric and in situ data to characterize their spatial structure we make use of the okubo weiss parameter which allows to separate the flow into vorticity dominated and deformation dominated regions the application of this parameter to geostrophic velocity fields obtained from sea level anomaly maps show that the observed eddies have a spatial structure in close resemblance to that found in coherent vortices of two dimensional turbulence these eddies appear to have a rather coherent vorticity dominated core region surrounded by an outer region dominated by deformation with a very complicated and variable in time structure this analysis is also applied to ctd data collected across three eddies sampled between 1997 and 1998 from these data eddy cores are equivalently defined as the interior region enclosed by the maximum of azimuthal velocity and are consistent with the horizontal structures seen in sla maps the distinction between the core and the outer region circulation cell is particularly important to understand the role of transport and stirring of properties associated to eddies as illustrated by the observed salinity structure some selected sst images and drifter trajectories the core is characterized by very small isopycnal salinity gradients while the surrounding cell is characterized by a strong slope of isohalines with respect to isopycnals persistent stagnation points are observed around the eddy and correspond to regions of high values of deformation with respect to vorticity these regions allow analyzing characteristic patterns seen in the corresponding sst images in addition drifters trajectories exhibit very different behavior when crossing such regions

monitoring eruptive activity at mount st helens with tir image data 1 thermal infrared tir data from the master airborne imaging spectrometer were acquired over mount st helens in sept and oct 2004 before and after the onset of recent eruptive activity pre eruption data showed no measurable increase in surface temperatures before the first phreatic eruption on oct 1 master data acquired during the initial eruptive episode on oct 14 showed maximum temperatures of 330 c and tir data acquired concurrently from a forward looking infrared flir camera showed maximum temperatures 675 c in narrow 1 m fractures of molten rock on a new resurgent dome master and flir thermal flux calculations indicated a radiative cooling rate of 714 j m2 s over the new dome corresponding to a radiant power of 24 mw master data indicated the new dome was dacitic in composition and digital elevation data derived from lidar acquired concurrently with master showed that the dome growth correlated with the areas of elevated temperatures low so2 concentrations in the plume combined with sub optimal viewing conditions prohibited quantitative measurement of plume so2 the results demonstrate that airborne tir data can provide information on the temperature of both the surface and plume and the composition of new lava during eruptive episodes given sufficient resources the airborne instrumentation could be deployed rapidly to a newly awakening volcano and provide a means for remote volcano monitoring

mapping variations in weight percent silica measured from multispectral thermal infrared imagery examples from the hiller mountains nevada usa and tres virgenes la reforma baja california sur mexico remotely sensed multispectral thermal infrared 8 13 m images are increasingly being used to map variations in surface silicate mineralogy these studies utilize the shift to longer wavelengths in the main spectral feature in minerals in this wavelength region reststrahlen band as the mineralogy changes from felsic to mafic an approach is described for determining the amount of this shift and then using the shift with a reference curve derived from laboratory data to remotely determine the weight percent sio 2 of the surface the approach has broad applicability to many study areas and can also be fine tuned to give greater accuracy in a particular study area if field samples are available the approach was assessed using airborne multispectral thermal infrared images from the hiller mountains nevada usa and the tres virgenes la reforma baja california sur mexico results indicate the general approach slightly overestimates the weight percent sio 2 of low silica rocks e g basalt and underestimates the weight percent sio 2 of high silica rocks e g granite fine tuning the general approach with measurements from field samples provided good results for both areas with errors in the recovered weight percent sio 2 of a few percent the map units identified by these techniques and traditional mapping at the hiller mountains demonstrate the continuity of the crystalline rocks from the hiller mountains southward to the white hills supporting the idea that these ranges represent an essentially continuous footwall block below a regional detachment results from the baja california data verify the most recent volcanism to be basaltic andesite

using the landsat thematic mapper to detect and monitor active volcanoes an example from lascar volcano northern chile the landsat thematic mapper tm offers a means of detecting and monitoring thermal features of active volcanoes using the tm we have discovered a prominent thermal anomaly on lascar volcano northern chile data from two short wavelength infrared channels of the tm show that material within a 300 m diameter pit crater was at a temperature of at least 380 c on two dates in 1985 the thermal anomaly closely resembles in size and radiant temperature the anomaly over the active lava lake at erta ale in ethiopia an eruption took place at lascar on september 16 1986 tm data acquired on october 27 1986 revealed significant changes within the crater area we find that lascar is in a much more active state than any other volcano in the central andes and for this reason it merits further careful monitoring our studies show that the tm is capable of confidently identifying thermal anomalies less than 100 m in size at temperatures of above 150 c and thus it offers a valuable means of monitoring the conditions of active or potentially active volcanoes particularly those in remote regions

global observations of large oceanic eddies 1 ten years of sea surface height ssh fields constructed from the merged topex poseidon t p and ers 1 2 altimeter datasets are analyzed to investigate mesoscale variability in the global ocean the higher resolution of the merged dataset reveals that more than 50 of the variability over much of the world ocean is accounted for by eddies with amplitudes of 5 25 cm and diameters of 100 200 km these eddies propagate nearly due west at approximately the phase speed of nondispersive baroclinic rossby waves with preferences for slight poleward and equatorward deflection of cyclonic and anticyclonic eddies respectively the vast majority of the eddies are found to be nonlinear

vortices of the mediterranean sea an altimetric perspective the presence of coherent vortices makes observed mesoscale fields of the ocean resemble twodimensional turbulence using this analogy a common definition of a coherent structure has been used to study the statistical properties of mediterranean sea vortices observed by satellite altimeters over a 7 yr period a vortex has been defined as the simply connected region with values of the okubo weiss parameter w 0 2w where w is the spatial standard deviation of w and the same sign of vorticity this definition is shown to be appropriate to detect and characterize statistically properties such as size mean kinetic energy and amplitude of vortices in the mediterranean basin from sea level anomaly maps corresponding to the period from october 1992 to october 1999 the distribution of such properties for the mediterranean vortices suggests a heuristic criterion to extract and select very coherent and long lived vortices from the whole set of structures identified in altimetric maps such coherent vortices appear to be selected for amplitudes greater than 2w where the amplitude has been defined in terms of the okubo weiss parameter rather than vorticity and strongly correspond to those reported from observations with independent data systematic locating and tracking of such vortices provide for the first time a general picture of their preferential paths in the mediterranean basin which are characterized by complex but rather well defined patterns

mesoscale eddies off peru in altimeter records identification algorithms and eddy spatio temporal patterns relatively little is known about coherent vortices in the eastern south pacific along the peruvian coast even with regard to basic facts about their frequency of occurrence longevity and structure this study addresses these issues with nearly 15 years of relatively high resolution satellite altimetry measurements we first compare two distinct automated methods for eddy identification the objective validation protocol shows that the rarely used geometrical or winding angle method based on the curvature of the streamline functions is more accurate than the commonly used okubo weiss algorithm which defines a vortex as a simple connected region with values of okubo weiss parameter weaker than a given threshold we then investigate vortices off peru using more than 20 000 mesoscale eddies identified by the winding angle method coherent eddies characterized by a high ratio of vorticity to deformation rate are typically formed along the coast and propagate westward at 3 6 cm s 1 the vortices have a mean radius of 80 km increasing northward and are most frequently observed off of chimbote 9s and south of san juan 15s the mean eddy lifetime is about 1 month but if eddies survive at least 2 months the probability for surviving an additional week or month is constant at 90 or 67 anticyclonic eddies tend to propagate northwestward whereas cyclonic vortices migrate southwestward in general cyclones and anticyclones are similar except for eddies surviving at least 6 months in this case after a similar 3 4 months of radius and amplitude growth amplitudes or sizes decay particularly rapidly for anticyclonic or cyclonic eddies in terms of intensity cyclonic eddies show a rapid decay during the first 3 months before arriving at a quasi constant value whereas anticyclones exhibit steady decline finally eddy temporal variations were examined at seasonal and interannual scales in the coastal region favorable to the formation of energetic mesoscale structures on seasonal scales eddy activity is maximal in fall and minimum in spring at interannual scales the eddy activity index was maximal during the strong el nino of 1997 1998 but another strong maximum of eddy activity also occurred late in 2004 these temporal variations are probably associated with the intensification of the upwelling thermal front and with the passage of coastal trapped waves which generate baroclinic instabilities further investigation of the mechanisms involved on the eddy genesis is needed

mesoscale eddies in the south china sea observed with altimeter data 1 a composite time series 1993 2000 of sea surface height anomaly from several satellites is used to identify eddies in the south china sea scs the eddy lifetime radius strength and straight line travel distance are estimated altogether 58 anticyclonic eddies and 28 cyclonic eddies are identified for this period they are grouped into four geographical zones according to known eddy generation mechanisms and their statistics are discussed accordingly our geographical classification is a useful first step in gaining an overview of their generation

average circulation seasonal cycle and mesoscale dynamics of the peru current system a modeling approach h isolines the pccc appears to be directly forced by the cyclonic wind stress curl the model is able to produce the upwelling front the cold water tongue which extends toward the equator and the equatorial front as described in the literature model seasonal changes in sst and ssh are compared to measurements for the central pcs model eke is 10 to 30 lower than the observations the model eddy diameters follow a strong equatorward increase the injection length scales derived from the energy spectra strongly correlate to the rossby radius of deformation confirming the predominant role of baroclinic instability at 3 s the model solution appears to switch from a turbulent oceanic regime to an equatorial regime dominated by zonal currents

divergent pathways of cyclonic and anti cyclonic ocean eddies satellite altimetry is used to study the propagation pathways of warm and cold ocean eddies in different ocean basins we consider eddies that have a life span longer than 3 months and we present three regional studies in the southeast indian the southeast atlantic and the northeast pacific oceans the case studies show that simple theories for vortex propagation on a plane work in regions where energetic eddies propagate though a weak background flow under these conditions anticyclonic cyclonic eddies propagate westward and equatorward poleward this divergence in the eddy pathways implies a net equatorward eddy heat flux and has implications for the meridional transport of freshwater carbon nutrients etc