eof analysis and modeling of gps tec climatology over north america an empirical ionospheric model of the total electron content tec over north america 20 60 n 40 140 w is constructed using the gps tec data collected by massachusetts institute of technology mit haystack observatory during the years 2001 2012 this model is based on an analysis of quiet time monthly averages using the empirical orthogonal function eof decomposition technique allowing for separation of spatial and temporal variations the importance of different types of spatial temporal variations to the overall tec variability can be well represented by the characteristics of eof basis functions and associated principal components coefficients with various modes the mode one eof decomposition constitutes 97 5 of the total variance and therefore represents the essential feature of north america spatial and diurnal variation of the tec the mode two eof as reported in an earlier study reveals a large and significant symmetric longitudinal variation of the ionosphere organized with respect to magnetic declination the mode three eof decomposition shows midlatitude latitudinal structure that varies with season in a manner very similar to the so called winter anomaly because of the quick convergence of eof decomposition modes the first four eof modes are utilized for constructing a tec empirical model for each of the eof modes the temporal variations are expressed analytically in terms of local time season and solar activity and the spatial variations by cubic spline functions an analysis of accuracy and quality indicates that this regional empirical tec model can reflect the majority of the quiet time monthly means and represent characteristic temporal spatial variations in the north america

constant concentration boundary condition lessons from the hydrocoin variable density groundwater benchmark problem in a solute transport model if a constant concentration boundary condition is applied at a node in an active flow field a solute flux can occur by both advective and dispersive processes the potential for advective release is demonstrated by reexamining the hydrologic code intercomparison hydrocoin project case 5 problem which represents a salt dome overlain by a shallow groundwater system the resulting flow field includes significant salinity and fluid density variations several independent teams simulated this problem using finite difference or finite element numerical models we applied a method of characteristics model mocdense the previous numerical implementations by hydrocoin teams of a constant concentration boundary to represent salt release by lateral dispersion only as stipulated in the original problem definition was flawed because this boundary condition allows the release of salt into the flow field by both dispersion and advection when the constant concentration boundary is modified to allow salt release by dispersion only significantly less salt is released into the flow field the calculated brine distribution for case 5 depends very little on which numerical model is used as long as the selected model is solving the proper equations instead the accuracy of the solution depends strongly on the proper conceptualization of the problem including the detailed design of the constant concentration boundary condition the importance and sensitivity to the manner of specification of this boundary does not appear to have been recognized previously in the analysis of this problem

a total electron content space weather study of the nighttime weddell sea anomaly of 1996 1997 southern summer with topex poseidon radar altimetry this paper reports on a total electron content space weather study of the nighttime weddell sea anomaly overlooked by previously published topex poseidon climate studies and of the nighttime ionosphere during the 1996 1997 southern summer to ascertain the morphology of spatial tec distribution over the oceans in terms of hourly geomagnetic longitudinal and summer winter variations the topex tec magnetic and published neutral wind velocity data are utilized to understand the underlying physical processes the tec results are combined with inclination and declination data plus global magnetic field line maps to investigate spatial and temporal tec variations geographic magnetic latitudes and local times are computed as results show the nighttime weddell sea anomaly is a large 1 600 2 22 million km2 estimated for a steady ionosphere space weather feature extending between 200 e and 300 e geographic it is an ionization enhancement peaking at 50 s 60 s 250 e 270 e and continuing beyond 66 s it develops where the spacing between the magnetic field lines is wide medium easterly declination is large medium 20 50 and inclination is optimum 55 s its development and hourly variations are closely correlated with wind speed variations there is a noticeable 43 reduction in its average area during the high magnetic activity period investigated southern summer nighttime tecs follow closely the variations of declination and field line configuration and therefore introduce a longitudinal division of four indian western eastern pacific atlantic northern winter nighttime tecs measured over a limited area are rather uniform longitudinally because of the small declination variation topex maps depict the expected strong asymmetry in tec distribution about the magnetic dip equator

the antarctic dipole and its predictability this study investigates the nature of interan nualvariability ofantarcticseaiceanditsrelationshipwith the tropical climate we nd that the dominant interan nual variance structure in the sea ice edge and surface air temperature elds is organized as a quasi stationary wave which we call the antarctic dipole adp it is charac terized by an out of phase relationship between the ice and temperature anomalies in the central eastern pacic and atlantic sectors of the antarctic the dipole consists of a strong standing mode and a weaker propagating motion within each basin s ice eld it has the same wavelength as the antarctic circumpolar wave acw and dominates the acw variance the dipole is clearly associated with tropical enso events it can be predicted with moderate skill using linear regression involving surface temperature two to four months ahead the prediction performs better in extreme warm cold years and best in la ni na years

on the relationship between the postmidnight thermospheric equatorial mass anomaly and equatorial ionization anomaly under geomagnetic quiet conditions the equatorial mass anomaly ema in the thermosphere and equatorial ionization anomaly eia in the ionosphere are two interesting phenomena in low equatorial latitude regions previous studies have shown that the ema appears between 1000 and 2000 local time lt and its location of trough is aligned with dip equator indicating the plausible role of the eia structure in the development of ema in this report we conducted a statistical study of the occurrence of postmidnight ema and eia on the basis of the champ in situ measurements during 2002 2008 our results revealed that clear ema and eia structures are sometimes visible in the postmidnight sector 0100 0600 lt during geomagnetic quiet periods kp 3 the postmidnight ema is not necessarily accompanied by the eia signature in both case study and statistics sense being distinct from the daytime situation in addition the occurrence rates of postmidnight ema and eia display contrasting behavior with respect to their local time longitudinal and solar activity dependences the highest occurrence rate for ema is 8 at around 0300 lt while the occurrence rate of the eia decreases gradually from about 30 at around 2300 lt to similar to 5 at 0600 lt longitudinal occurrence of postmidnight eia presents a wave like pattern however no salient feature appears for the longitudinal occurrence of ema postmidnight ema is more likely to occur at lower solar activity whereas an opposite trend presents in the eia on the basis of above results our findings imply that a simple eia ema cause effect relationship does not hold in the postmidnight sector

simulated midlatitude summer nighttime anomaly in realistic geomagnetic fields 1 in the present work using the three dimensional theoretical ionospheric model of the earth in institute of geology and geophysics chinese academy of sciences time3d iggcas we simulate the temporal spatial distribution of the midlatitude summer nighttime anomaly msna and the influences of thermospheric meridional and zonal winds on the formation of msna msna mainly appears in three distinct regions the east asian region the northern atlantic europe region and the south pacific region msna in the south pacific region is obviously stronger than that in the other two regions in these three regions msna not only occurs in local summer but also often occurs in equinox through lifting up or lowering the f region ionization thermospheric winds mainly drive the formation of msna in the east asian region and the northern atlantic europe region msna are mainly driven by the thermospheric meridional wind and the influence of the thermospheric zonal wind can be neglected however although msna in the south pacific region or weddell sea anomaly are mainly driven by the thermospheric meridional wind the thermospheric zonal wind also plays an important role in the formation of msna

ice and ocean processes in the bellingshausen sea antarctica 1 in the vicinity of the antarctic peninsula observations show diminishing sea ice and a rapid warming of atmosphere and ocean these changes have led to the collapse of ice shelves and retreat acceleration and thinning of inland ice however ocean observations in the center of the nearby bellingshausen sea are spatially and temporally coarse in this study ocean and sea ice models forced by atmospheric reanalyses are used to investigate this data gap by simulating processes in the bellingshausen sea for the years 1979 2007 the model suggests flow features in the region and predicts the basal melting of local ice shelves modeled ocean conditions are found to be less variable than in the nearby amundsen sea which is situated closer to foci of annual and interannual atmospheric variability melt rates beneath george vi ice shelf are investigated in detail concluding that the ice shelf may have been melting out of balance and therefore thinning for decades the melt rate contains significant interannual variability that the model links to variation in sea ice conditions offshore of the southern end of the ice shelf this stands in contrast to the amundsen sea where models suggest that ice shelf melting is controlled by variable transport of circumpolar deep water onto the continental shelf

annular modes in the extratropical circulation part i month to month variability the leading modes of variability of the extratropical circulation in both hemispheres are characterized by deep zonally symmetric or annular structures with geopotential height perturbations of opposing signs in the polar cap region and in the surrounding zonal ring centered near 458 latitude the structure and dynamics of the southern hemisphere sh annular mode have been extensively documented whereas the existence of a northern hemisphere nh mode herein referred to as the arctic oscillation ao has only recently been recognized like the sh mode the ao can be defined as the leading empirical orthogonal function of the sea level pressure field or of the zonally symmetric geopotential height or zonal wind fields in this paper the structure and seasonality of the nh and sh modes are compared based on data from the national centers for environmental prediction national center for atmospheric research reanalysis and supplementary datasets the structures of the nh and sh annular modes are shown to be remarkably similar not only in the zonally averaged geopotential height and zonal wind fields but in the mean meridional circulations as well both exist year round in the troposphere but they amplify with height upward into the stratosphere during those seasons in which the strength of the zonal flow is conducive to strong planetary wave mean flow interaction midwinter in the nh and late spring in the sh during these active seasons the annular modes modulate the strength of the lagrangian mean circulation in the lower stratosphere total column ozone and tropopause height over mid and high latitudes and the strength of the trade winds of their respective hemispheres the nh mode also contains an embedded planetary wave signature with expressions in surface air temperature precipitation total column ozone and tropopause height it is argued that the horizontal temperature advection by the perturbed zonal mean zonal wind field in the lower troposphere is instrumental in forcing this pattern a companion paper documents the striking resemblance between the structure of the annular modes and observed climate trends over the past few decades

theoretical study of the ionospheric weddell sea anomaly using sami2 1 the ionospheric weddell sea anomaly wsa was first reported more than five decades ago based on ionosonde data near the antarctica peninsula the wsa is an ionospheric structure characterized by a larger nighttime electron density than daytime density recent satellite observations indicate that the wsa can extend from south america and antarctica to the central pacific the major physical mechanisms that have been suggested for the wsa formation are an equatorward neutral wind an electric field the photoionization and the downward diffusion from the plasmasphere on the basis of the theoretical modeling performed in this study using the sami2 model an equatorward neutral wind is identified as the major cause of the wsa while the downward flux from the plasmasphere provides an additional plasma source to enhance or maintain the density of the anomalous structure

interpretation of recent antarctic sea ice variability 1 trends in the satellite derived antarctic sea ice concentrations 1979 2002 show pronounced increase decrease in the central pacific sector bellingshausen western weddell sector by 4 10 per decade confidence levels for these regional trends exceed 95 positive polarities of the antarctic oscillation aao lead to more less ice in the eastern ross amundsen sector bellingshausen northern weddell sector which are qualitatively opposite to the impacts of positive polarities of the el nino southern oscillation enso the mechanisms responsible for the covariability between the ice and the a aao and b enso are demonstrated over the last 24 years a positive aao trend and a slightly negative enso trend produce a spatial pattern of ice changes similar to the regional ice trends however the magnitude of the ice changes associated with the aao and enso is much smaller than the regional ice trends more local or less understood large scale processes should be investigated for the explanations

longitudinal variations of topside ionospheric and plasmaspheric tec the upward looking ionospheric total electron content tec from the metop a and tsx satellites during 2008 2015 has been used to systematically study the longitudinal variations of the topside ionosphere and plasmasphere the results of this study are summarized as follows 1 there are significant longitudinal variations in the topside ionosphere and plasmasphere at low latitudes the tec maximum during the june solstice over the western and central pacific ocean corresponds to a tec minimum at the same location during the december solstice but the opposite behavior occurs over south america and the atlantic ocean 2 during the solstices the relative longitudinal variations in the geomagnetic equatorial region do not have a strong dependence on local time and solar activity 3 the tec in the winter hemisphere decreases with increasing solar activity especially at higher altitudes and at night the topside tec depletion with solar activity depends on longitude 4 the solstice like longitudinal pattern lasts much longer than the equinox like patterns with the june solstice pattern lasting the longest furthermore the equinox like longitudinal patterns occur in march when expected whereas they extend from the autumnal equinox until the end of october 5 the longitudinal variations of upward looking tec are different from the corresponding longitudinal variations of electron densities around the f2 peak and orbital altitudes this indicates that the topside ionosphere structure is strongly influenced by the physical processes in the topside region rather than being a pure reflection of the ionospheric f2 peak structure

variation of the topside ionosphere during the last solar minimum period studied with multisatellite measurements of electron density and temperature using the ionospheric measurements of champ demeter and dmsp f15 the seasonal and spatial variations of the topside ionosphere during the last solar minimum period were investigated and compared with ionospheric models in all the satellite measurements equatorial ionization anomaly eia shows clearly longitudinal asymmetry with wave number 3 or 4 patterns anomalous increases of ne in the nighttime surpassing daytime ne known as the weddell sea anomaly wsa or mid latitude summer nighttime anomaly msna were also observed in the global ne distribution with differences in detailed geometry of the geomagnetic field according to the altitude in the nighttime ionosphere the reduced te in the equatorial region at the dmsp altitude identified as the equatorial plasma temperature anomaly epta was ascribed to the leftover of the prereversal enhancement of the upward plasma drift though the eia wsa msna and epta are all associated with the upward plasma movement the difference in the thermal evolution is ascribable to the geometry of drift in which the plasma moves across the geomagnetic field line for the eia and the epta while along the field line for the wsa and the msna

behavior of the f2 peak ionosphere over the south pacific at dusk during quiet summer conditions from cosmic data 1 the six satellite constellation observing system for meteorology ionosphere and climate cosmic mission makes routine ionospheric measurements over the entire globe using occultation techniques these observations have been used in this study to develop global scale climate maps of nmf2 and hmf2 during the southern northern summer winter enhanced electron densities that appear to be associated with the southern equatorial appleton anomaly are displaced far southward at dusk and within about an hour form the weddell sea anomaly coincidentally the height of the f2 peak increases on the northern boundary of this anomaly this height increase is also displaced southward as the enhanced electron densities are displaced southward suggesting that the electron density increases are associated with the f2 peak rising as well as being an interesting phenomenon in its own right this behavior may shed new light on the formation of the weddell sea anomaly no unambiguous explanation for this behavior can be determined from the data presently available but an examination of some possibilities suggests that an evening downward flux of plasma from the plasmasphere may be at least partly responsible for the phenomenon

field aligned neutral wind bias correction scheme for global ionospheric modeling at midlatitudes by assimilating formosat 3 cosmic hmf2 data under geomagnetically quiet conditions this study demonstrates the usage of a data assimilation procedure which ingests the formosat 3 cosmic f3 c hmf2 observations to correct the model wind biases to enhance the capability of the new global ionosphere plasmasphere electrodynamics ipe model under geomagnetically quiet conditions the ipe model is built upon the field line interhemispheric plasma model with a realistic geomagnetic field model and empirical model drivers the hmf2 observed by the f3 c radio occultation technique is utilized to adjust global thermospheric field aligned neutral winds i e a component of the thermospheric neutral wind parallel to the magnetic field at midlatitudes according to a linear relationship between time differentials of the field aligned wind and hmf2 the adjusted winds are further applied to drive the ipe model the comparison of the modeled electron density with the observations of f3 c and ground based gps receivers at the 2012 march equinox suggests that the modeled electron density can be significantly improved in the midlatitude regions of the southern hemisphere if the wind correction scheme is applied moreover the f3 c observation the ipe model and the wind bias correction scheme are applied to study the 2012 southern hemisphere midlatitude summer nighttime anomaly southern msna weddell sea anomaly wsa event at december solstice for examining the role of the neutral winds in controlling the longitudinal variation of the southern msna wsa behavior with the help of the wind bias correction scheme the ipe model better tracks the f3 c observed eastward movement of the southern msna wsa feature the apparent eastward movement of the southern msna wsa features in the local time coordinate is primarily caused by the longitudinal variation in the declination angle of the geomagnetic field that controls the field aligned projection of both geographic meridional and zonal components of the neutral wind both the ipe simulations and the f3 c observations show the significant longitudinal variation in the speed of the eastward movement of the southern msna wsa

trends and connections across the antarctic cryosphere satellite observations have transformed our understanding of the antarctic cryosphere the continent holds the vast majority of earth s fresh water and blankets swathes of the southern hemisphere in ice reductions in the thickness and extent of floating ice shelves have disturbed inland ice triggering retreat acceleration and drawdown of marine terminating glaciers the waxing and waning of antarctic sea ice is one of earth s greatest seasonal habitat changes and although the maximum extent of the sea ice has increased modestly since the 1970s inter annual variability is high and there is evidence of longer term decline in its extent this paper discusses how antarctic ice has changed over recent decades and how these changes have been recorded in satellite observations

variation of the equatorial height anomaly during the main phase of 2015 st patrick s day geomagnetic storm using annim and tiegcm

interpretation of recent southern hemisphere climate change climate variability in the high latitude southern hemisphere sh is dominated by the sh annular mode a large scale pattern of variability characterized by fluctuations in the strength of the circumpolar vortex we present evidence that recent trends in the sh tropospheric circulation can be interpreted as a bias toward the high index polarity of this pattern with stronger westerly flow encircling the polar cap it is argued that the largest and most significant tropospheric trends can be traced to recent trends in the lower stratospheric polar vortex which are due largely to photochemical ozone losses during the summer fall season the trend toward stronger circumpolar flow has contributed substantially to the observed warming over the antarctic peninsula and patagonia and to the cooling over eastern antarctica and the antarctic plateau

an antarctic circumpolar wave in surface pressure wind temperature and sea ice extent the southern ocean is the only oceanic domain encircling the globe it contains the strong eastward flow of the antarctic circumpolar current and is the unifying link for exchanges of water masses at all depths between the world s major ocean basins1 as these exchanges are an important control on mean global climate the southern ocean is expected to play an important role in transmitting climate anomalies around the globe interannual variability has been often observed at high southern latitudes and observations of sea ice extent suggest that such features propagate eastwards around the southern ocean2 3 here we use data from a variety of observational techniques to identify significant interannual variations in the atmospheric pressure at sea level wind stress sea surface temperature and sea ice extent over the southern ocean these anomalies propagate eastward with the circumpolar flow with a period of 4 5 years and taking 8 10 years to encircle the pole this system of coupled anomalies which we call the antarctic circumpolar wave is likely to play an important role in climate regulation and dynamics both within and beyond the southern ocean

synchronous variability in the southern hemisphere atmosphere sea ice and ocean resulting from the annular mode zonally symmetric fluctuations of the midlatitude westerly winds characterize the primary mode of atmospheric variability in the southern hemisphere during all seasons this is true not only in observations but also in an unforced 15 000 yr integration of a coarse resolution r15 coupled ocean atmosphere model here it is documented how this mode of atmospheric variability known as the southern annular mode sam generates ocean circulation and sea ice variations in the model integration on interannual to centennial timescales that are tightly in phase with the sam the positive phase of the sam is associated with an intensification of the surface westerlies over the circumpolar ocean around 608s and a weakening of the surface westerlies farther north this induces ekman drift to the north at all longitudes of the circumpolar ocean and ekman drift to the south at around 308s through mass continuity the ekman drift generates anomalous upwelling along the margins of the antarctic continent and downwelling around 458s the anomalous flow diverging from the antarctic continent also increases the vertical tilt of the isopycnals in the southern ocean so that a more intense circumpolar current is also closely associated with positive sam in addition the anomalous divergent flow advects sea ice farther north resulting in an increase in sea ice coverage finally positive sam drives increases in poleward heat transport at about 308s while decreases occur in the circumpolar region ocean and sea ice anomalies of the opposite sign occur when the sam is negative the ocean and sea ice fluctuations associated with the sam constitute a significant fraction of simulated ocean variability poleward of 308s year round the robustness of the mechanisms relating the sam to oceanic variability suggests that the sam is likely an important source of large scale variability in the real southern hemisphere ocean

definition of antarctic oscillation index following walker s work about his thmous three oscillations published during the 1920 30s many papers were written about atmospheric oscillations a iburth atmospheric oscillation in the middle and high southern latitudes was lbund and nanted the grotarctic oscillation ao a refiers to a large scale alternation of atmospheric mass between the mid latitudes and high latitudes surthce pressure in order to understand the spatial structure of sea level pressure variation in detail empirical orthogonal fitnction analysis is applied an objective index of the antarctic oscillation index aoi is defined as the diffierence of zonal mean sea level pressure between 40os and 65os the aoi has the potential tbr clarifying climate regimes in the southern hemisphere similar to how the na and the npo has been used in the northern hemisphere were there other oscillation s besides nao npo and s especially in the southern hemisphere it had been supposed that there might be other atmospheric oscillation s in the high southern latitudes although as early as in the first quarter of this century walker 1928 had stated that just as in the north atlantic there is a pressure opposition between the azores and iceland there is an opposition between the high pressure belt across chile and the argentine on the one hand and the low pressure area of weddell sea and the bellingshausen sea on the other the scarcity of data in the southern hemisphere hindered the search tbr new oscillation s during the last two decades more comprehensive data over the southern hemisphere became available and more analyses were carried out see kidson 1975 rogers and van loon 1982 mo and l 7 ite 1985 2 4o 1986 connolley 1997 gong and wang 1998 a tburth atmospheric oscillation in the middle and high southern latitudes was tbund and nanted as the antarctic oscillation a wang 1992 gong and wang 1998 the term ao relrs to a large scale alternation of atmospheric mass between the mid latitude sur hce pressure

antarctic sea ice velocity as derived from ssm i imagery sea ice velocities derived from remotely sensed microwave imagery of the special sensor microwave imager ssm i have been analyzed for changes over time in antarctic sea ice velocity for the period 1988 2004 year to year variability in mean antarctic annual ssm i derived ice speed is small 17 year standard deviation sd 0 008 ms 1 with greater interannual variability in the zonal eastward positive velocity components 17 year sd 0 016ms 1 seasonally minimum ice speed is encountered during summer when nearly all antarctic sea ice is within the marginal ice zone ice motion peaks during winter and spring due to high velocities encountered in the outer pack of the seasonal sea ice zone the correlation r 2 0 47 between winter southern annular mode sam and mean winter ice speed highlights the importance of atmospheric forcing on sea ice dynamics the spatial pattern of the correlation of the standardized sam index with the june november ice speed exhibits a wave 3 pattern which matches the sea level pressure distribution sea ice speed in the upstream regions of quasi stationary centres of low sea level pressure is likely to increase decrease during high low samyears and the opposite for sea ice speed in the downstream regions of the centres

a study on the nighttime midlatitude ionospheric trough constellation observing system for meteorology ionosphere and climate cosmic electron density profiles are used to investigate the nighttime midlatitudeionospheric trough mit we find that at midnight the longitudinally deepest mit occursto the west of the geomagnetic pole in both the northern and southern hemispheres duringthe equinox seasons and local summer the deepest mit could be ascribable to theenhanced depletion caused by horizontal neutral wind in the early evening the eastwardneutral wind prevails in the midlatitude f region which blows the plasma downwardwhere the declination is eastward in the northern hemisphere but westward in thesouthern hemisphere both lying to the west of the geomagnetic pole the downward driftwould enhance the plasma depletion for more molecular composition at lower altitude in addition we find for the first time that the location of nighttime mit minimumoscillated with a periodicity of 9 days and an amplitude of about 1 1 5 geomagneticlatitude during 2007 2008 associated with the recurrent high speed solar wind ourresults shed new light on the empirical description and numerical simulation of mit

the summer evening anomaly and conjugate effects 1 the constellation observing system for meteorology ionosphere and climate cosmic gps occultation data have been analyzed in this study to provide a better understanding of the weddell sea anomaly wsa and to place it in the wider context of a general phenomenon that occurs near dusk in summer which we are calling the summer evening anomaly to better capture its global nature the terminator and the magnetically conjugate points for the terminator in the other hemisphere have been plotted on top of global maps of cosmic nmf2 and hmf2 for 2 months either side of the december and june solstices for 2006 2008 these plots show that there are distinct enhancements of nmf2 and increases in hmf2 as soon as the conjugate footprint of the field line on the winter terminator is seen at middle latitudes in the summer hemisphere this effect is most pronounced where the wsa is formed but it also occurs across the south pacific ocean in the southern summer and across much of the north atlantic ocean siberia and kamchatka during the northern summer an hmf2 increase occurs between the two terminators even at locations where there is no increase in nmf2 a similar but reversed effect occurs in hmf2 near dawn this behavior appears to be most consistent with upward and poleward ion drifts in the evening but neutral wind and downward precipitation may make important contributions to this effect

first tomographic observations of the midlatitude summer nighttime anomaly over japan 1 recently a chain of digital beacon receivers has been established over japan mainly for the tomographic imaging of the ionosphere these receivers are installed at shionomisaki 33 45 n 135 8 e shigaraki 34 85 n 136 1 e and fukui 36 06 n 136 e which continuously track the low earth orbiting satellites leos and the simultaneous line of sight total electron content tec data are used for tomographic reconstruction in the images obtained during july 2008 it is seen that the nighttime electron densities exceed the daytime values on almost all days over latitudes 33 34 n on several days these northern latitudes show enhanced electron densities compared to the low latitude region during nighttime these are the prominent features of the midlatitude summer nighttime anomaly msna that is recently observed in the northern hemisphere and is considered similar to the nighttime weddell sea anomaly wsa this is the first study of the msna using tomographic technique and found its significant day to day variability the ionosonde data from wakkanai 45 4 n 141 7 e ground based gps tec observations using the geonet champ in situ electron density measurements and formosat3 cosmic f3 c occultation measurements are also used to confirm the presence of msna over this region and to examine its variability it is seen that in general during the local summer period electron density over the northern latitudes is highest at 2000 2100 lt and the latitudinal enhancement in electron density also begins to appear around the same time which continues to exist even at later hours

topside ionospheric electron temperature and density along the weddell sea latitude it has been well known that the ionospheric electron density ne is greater in the summer nighttime than daytime around the weddell sea region which is named weddell sea anomaly wsa this paper for the first time reports unusual increases decreases of the daytime nighttime electron temperature te at about 830 km altitude over the wsa latitudes probed by tatiana 2 during december 2009 to january 2010 concurrent measurements at 660 830 km altitude observed by tatiana 2 detection of electro magnetic emissions transmitted from earthquake regions demeter and formosa satellite 3 constellation observing system for meteorology ionosphere and climate f3 c reveal the anticorrelation between te and ne along the wsa latitudes in the daytime and nighttime based on f3 c ne along the wsa latitudes observed at various local times the associated te values are computed the tatiana 2 and demeter observations as well as the computed results show that te yield the maximum values over the wsa region during daytime and over the indian and atlantic ocean area during nighttime the maxima or minima in f3 c ne and the computed te reveal eastward phase shifts

the ionospheric midlatitude trough observed by formosat 3 cosmic during solar minimum 1 this paper for the first time reports global three dimensional 3 d structures of the ionospheric midlatitude trough using electron density profiles derived from the gps radio occultation experiment on board formosat 3 cosmic f3 c satellites during the solar minimum period february 2008 to january 2009 results show that the midlatitude trough extends from dusk to dawn in all four seasons and is most pronounced in the winter hemisphere the troughs in the two hemispheres are asymmetric where the trough in the northern hemisphere is more evident and stronger than that in the southern hemisphere during the equinoctial seasons in general the trough minimum position shows a high low high latitudinal variation with magnetic local time and occurs at lower latitudes under higher magnetic activity on the other hand the midlatitude trough structures become more complex in the southern hemisphere because of the nighttime plasma density enhancement of the weddell sea anomaly our results demonstrate that the new data set of gps radio occultation by f3 c is useful to probe the global 3 d electron density structures of the midlatitude trough

satellite derived maps of arctic and antarctic sea ice motion 1988 to 1994 standard image processing methods applied to 85 5 ghz special sensor microwave imager ssm i data provide previously unseen details about sea ice motion in the arctic and southern oceans means calculated from daily ice motions for 1988 1994 confirm the basic circulation patterns established from drifting stations and buoys but extend these observations to illustrate less well known transport patterns in the arctic coastal zones and sub arctic seas in the antarctic the gridded motion fields show a nearly continuous westward transport along the antarctic coast with well defined regions of exchange between this east wind drift and the antarctic circumpolar current this detailed view of mean ice motion in the southern ocean is unique and presents a comprehensive overview not previously available for antarctic ice motions