migrating and nonmigrating semidiurnal tides in the upper atmosphere excited by tropospheric latent heat release migrating and nonmigrating semidiurnal tides

modeling ionospheric super fountain effect based on the coupled timegcm sami3 1 recently efforts have been undertaken to develop a coupled thermosphere ionosphere plasmasphere model based on two well established models namely the thermosphere ionosphere mesosphere general circulation model timegcm developed at the national center for atmospheric research and the sami3 ionosphere model developed at the naval research laboratory this paper presents the first results from the coupled model on the investigation of a prompt penetration electric field ppef event that took place on 9 november 2004 the coupled model eliminates two major upper boundary limitations of the stand alone timegcm e g the upper boundary height and the prescribed o fluxes at the upper boundary it is found that the f layer peak height is raised above 800 km in response to the large ppef the o fluxes in the top ionosphere vary drastically during the course of the ppef with strong upward and downward fluxes with a magnitude greater than 109 cm 2 s 1 in localized regions for the first time the coupled model allows us to simulate and visualize the super fountain effect on a global scale future model development is also envisaged including the implementation of a more realistic magnetic field model and a fully two way coupling between neutrals and ions

detection of migrating diurnal tide in the tropical upper troposphere and lower stratosphere using the challenging minisatellite payload radio occultation data 1 the atmospheric limb sounding technique making use of radio signals transmitted by the global positioning system gps has already proven to be a promising approach for global atmospheric measurements in this study we assess for the first time the potential of gps radio occultation soundings for detecting the migrating diurnal tide retrieved temperatures between 10 and 30 km in the tropics from the challenging minisatellite payload champ occultation observations during may 2001 to august 2005 are analyzed using space time spectrum analysis to isolate diurnal waves because of incomplete local time lt coverage of the monthly champ occultation data in any given year data from all available years are merged to obtain complete 24 h lt coverage the effects of aliasing associated with uneven data sampling and measurement noise are estimated using synthetic data the results show the feasibility of determining tidal structures from the composite champ occultation data and the vertical seasonal and latitudinal structures of the diurnal tide are presented the estimated diurnal amplitude generally increases with altitude exhibiting a maximum of order 1 k at 30 km the estimated phase indicates an upward propagating mode above 14 km with a vertical wavelength about 20 km the observed diurnal tide at 30 km exhibits a distinct seasonallatitudinal variation comparison of the observed diurnal tide to the simulated tide in the extended canadian middle atmosphere model cmam and global scale wave model version 2 gswm02 indicates that cmam overestimates the amplitude but reproduces the seasonal latitudinal variation of the diurnal tide while gswm02 simulates well the annual mean amplitude but lacks the seasonal latitudinal variation of the diurnal tide

variabilities of low latitude migrating and nonmigrating tides in gps tec and timed saber temperature during the sudden stratospheric warming event of 2013 the global positioning system gps deduced total electron content tec data at 15 n geomagnetic which is the crest region of equatorial ionization anomaly are used to study tidal variabilities during the 2013 sudden stratospheric warming ssw event the results from space time spectral analysis reveal that the amplitudes of migrating diurnal dw1 and semi diurnal sw2 tides are larger than those of non migrating tides after the ssw onset the amplitudes of dw1 sw2 sw1 and ds0 increase moreover they show 16 day variations similar to the periodicity of the high latitude stratospheric planetary wave pw suggesting that the non migrating tides sw1 and ds0 are possibly generated due to non linear interaction of migrating tides with pw similar spectral analysis on temperature at 10 n obtained from the sounding of atmosphere by broadband emission radiometry saber shows that the sw2 enhances at stratospheric heights and the sw2 is more dominant at 80 90 km but its amplitude decreases around 100 km the amplitudes of non migrating tides become comparable to those of sw2 around 100 km and their contribution become increasingly important at higher heights this suggests that the non linear interaction between migrating tides and pw occur at low latitude upper mesospheric heights as sw2 exhibits 16 day periodicity in saber temperature at 100 km as observed in tec besides it is observed that the eastward propagating tides are less dominant than westward propagating tides in both tec and saber temperature

temporal modulation of the four peaked longitudinal structure of the equatorial ionosphere by the 2 day planetary wave 1 observations of electron densities by the constellation observing system for meteorology ionosphere and climate in august to october 2008 have shown a prominent four peaked longitudinal structure in the height of the f2 layer hmf2 in the equatorial ionosphere the development of this ionospheric structure in daytime is found to be consistent with the forcing by the eastward propagating nonmigrating diurnal tide with zonal wave number 3 de3 it is believed that tidal winds can modify the e region electric fields and subsequently produce variations in the ionosphere through the dynamo effect this study reveals that the amplitude of the hmf2 four peaked longitudinal structure is subject to a 2 day periodic modulation on certain intervals in the two month time period simultaneously wind measurements from the skiymet meteor radar at thumba 8 5 n 77 e india indicate corresponding 2 day planetary wave activity in the mesosphere and lower thermosphere mlt the 2 day planetary wave has both zonal and meridional wind components and it is the variability in the zonal component that most closely corresponds to f2 layer changes the zonal wind observations by the radar also show that the amplitude of the diurnal tide is modulated by the 2 day wave this study suggests that the identified 2 day variation of the hmf2 four peaked longitudinal structure in the equatorial ionosphere is caused by the interaction between the de3 tide and the 2 day planetary wave

water level response in back barrier bays unchanged following hurricane sandy on 28 30 october 2012 hurricane sandy caused severe flooding along portions of the northeast coast of the united states and cut new inlets across barrier islands in new jersey and new york about 30 of the 20 highest daily maximum water levels observed between 2007 and 2013 in barnegat and great south bay occurred in 5 months following hurricane sandy hurricane sandy provided a rare opportunity to determine whether extreme events alter systems protected by barrier islands leaving the mainland more vulnerable to flooding comparisons between water levels before and after hurricane sandy at bay stations and an offshore station show no significant differences in the transfer of sea level fluctuations from offshore to either bay following sandy the post hurricane sandy bay high water levels reflected offshore sea levels caused by winter storms not by barrier island breaching or geomorphic changes within the bays

nonmigrating diurnal tides in mesospheric and lower thermospheric winds and temperatures abstract this paper presents analyses of nonmigrating diurnal tide signatures in high resolution doppler imager mesospheric and lower thermospheric winds and temperatures a global comparison of both winds and temperature reveals equatorial features corresponding to nonmigrating tides structures interpreted as zonal mean and eastward nonmigrating diurnal tides display consistency between horizontal winds and temperatures the second symmetric mode is prominent in the zonal mean and wavenumber 1 the gravest antisymmetric mode and the gravest symmetric or kelvin mode are the main features in zonal wavenumbers 2 and 3 the amplitudes of the tides generally increase with altitude and maximize within 90 110 km

on modeling migrating solar tides recent updates and extensions to a steady state two dimensional linearized model of global scale atmospheric waves have facilitated improved calculations of the subset of those waves which are subharmonics of a solar day and propagate with the apparent motion of the sun the model improvements are briefly described and some updated predictions of the migrating solar diurnal component are highlighted the latter represent the first numerical modeling effort to examine the seasonal variability of the migrating diurnal harmonic as it propagates into the mesosphere and lower thermosphere

diurnal nonmigrating tidal oscillations forced by deep convective clouds the global distribution of latent heat released by the diurnal oscillations in deep convective precipitating clouds is investigated as a forcing mechanism of diurnal nonmigrating atmospheric tidal modes the seasonal distribution of this forcing is deduced from 3 hour temporal resolution infrared 11 m radiance measured by four geostationary and two polar orbiting satellites which was transformed into the zonal wavenumber domain yielding migrating and non migrating oscillations the dominant wavenumbers in the forcing include the westward propagating 5 2 and 1 oscillations the eastward propagating 3 oscillation and the standing oscillation these dominant wavenumber oscillations were decomposed into hough functions to describe their meridional structure a vertical profile of latent heating rate was estimated and the dominant 22 tidal modes were used in an f plane model to determine the middle atmospheric response to this tropospheric forcing the f plane model was also excited using heating rates associated with the solar insolation absorption by water vapor the magnitude of the model atmosphere diurnal winds from both water vapor and latent heat is similar at certain locations this response suggests that the superposition of many nonmigrating tidal modes forced by the latent heat release of precipitating clouds is important in understanding the middle atmospheric circulation

climatology of upward propagating diurnal and semidiurnal tides in the thermosphere 1 a major challenge in delineating and understanding the space weather of the ionosphere thermosphere system is the lack of global tidal observations in the 120 400 km thermospheric gap between satellite remote sensing and in situ tidal diagnostics this paper aims to close this gap by presenting an observation based climatological tidal model of the thermosphere ctmt of self consistent upward propagating migrating and nonmigrating diurnal and semidiurnal tides from 80 400 km and pole to pole for moderate f10 7 110 sfu solar flux conditions ctmt includes the 6 8 most important diurnal semidiurnal tidal components for temperature density and zonal meridional and vertical winds and is based on hough mode extension fits to 2002 2008 mean timed satellite tidal diagnostics in the mesosphere lower thermosphere mlt validation with independent 2002 2008 champ tidal diagnostics f10 7 105 sfu around 400 km proves that the approach captures nonmigrating tides well indicating that these waves propagate directly upward without significant tidal forcing occurring in the thermosphere notable exceptions are the dw2 and d0 components that are most likely generated in situ by nonlinear interaction forcing in the upper thermosphere ctmt is suitable for driving upper atmosphere models that require self consistent tidal fields in the mlt region as a lower boundary condition it does not include migrating tides due to in situ euv absorption in the upper thermosphere but allows us to quantitatively assess thermospheric variability due to tides from the lower atmosphere this is done by discussing longitude latitude maps of reconstructed diurnal and semidiurnal tidal variations as function of altitude and local time

source regions for antarctic mlt non migrating semidiurnal tides 1 source regions for the westward propagating zonal wavenumber one and three components of the semidiurnal tide observed in the summer mesosphere and lower thermosphere over antarctica are identified by correlating local tidal variations with global planetary wave one activity in the stratosphere and lower mesosphere the advantages of using zonal wavenumber resolved tidal amplitudes for such a study are described the results support the prediction of a source region in the northern hemisphere

long term oscillations of the wind field in the tropical mesosphere and lower thermosphere from hawaii mf radar measurements 1 wind measurements in the mesosphere and lower thermosphere obtained with a medium frequency mf radar in hawaii 22 n 160 w spanning 16 years are employed to examine the intra annual and interannual variability of the mean and tidal motions at altitudes between 84 and 94 km intra annual periodicities range from 3 to 12 months with significant coherence in altitude and between the zonal and meridional components of each motion field interannual variations confirm the dominant periodicities identified previously at this site and elsewhere in particular the significant diurnal and less significant semidiurnal tidal responses at periods of 28 and 48 months amplitudes of these long period oscillations of the diurnal tide increase with altitude below 92 km and are larger than the amplitudes of the 12 month oscillations above 90 km phases of the 28 and 48 month oscillations show a downward progression with a slightly larger altitude variation in the meridional diurnal tide for the 28 month oscillation and a significantly larger altitude variation in the zonal diurnal tide for the 48 month oscillation the long and nearly continuous hawaii data set also enables characterization of the responses of the wind fields to the 11 year solar cycle both wind and tidal fields exhibit this periodicity but these responses display interesting and different relations to the phase of the solar cycle the 11 year oscillation of the meridional wind is nearly in phase with the solar cycle while the 11 year oscillation of the zonal wind is in approximate quadrature with the solar cycle the 11 year oscillations of the semidiurnal tidal amplitudes and the meridional diurnal amplitude are all in approximate quadrature with the solar cycle with the tidal amplitudes leading by 29 to 37 months while the 11 year oscillation of the zonal diurnal amplitude is somewhat nearer an antiphase than a quadrature relation to the solar cycle leading by 54 months

the diurnal cycle of tropical convection the diurnal cycle of tropical convection is investigated with global cloud imagery constructed from 11 m radiance measurements taken aboard six satellites four harmonics of the diurnal cycle are resolved in the cloud imagery with about 50 km horizontal resolution to isolate deep convective activity from other processes which cause diurnal fluctuations in longwave radiance an index of deep convective activity is constructed by thresholding to brightness temperatures less than 230 k significant diurnal amplitude of deep convection is found only over tropical landmasses over the tropical oceans the diurnal cycle is weak and is barely discernible from the background red spectrum of convective variance nonetheless oceanic convection exhibits a systematic diurnal fluctuation with maximum intensity in the early morning nocturnal subsidence along the cloud free equator is postulated to play a role in forcing diurnal variation in the intertropical convergence zones other mechanisms are also implied to contribute as a similar early morning maximum in deep convection is seen even where no adjoining cloud free regions occur the diurnal cycle of deep convection is found to be organized on planetary scales predominantly in nonmigrating modes i e modes with phase speeds not equal to that of the sun the nonmigrating modes are postulated to be produced by the nonuniform distribution of convective centers the nonmigrating zonally symmetric component is found to be especially large while the role of this mode in forcing diurnal variations of the tropospheric circulation e g the hadley cell is questionable its role in modulating the ionospheric electric potential is well established discrepancies with the traditional notion that cloud to ground lightning is the dominant mechanism by which the earth is negatively charged are discussed in particular the probable role of nonlightning producing clouds e g the stratiform portion of convective complexes in diurnally modulating the negative charge on earth is discussed

tidal oscillations of the arctic upper mesosphere and lower thermosphere in winter the upper mesosphere and lower thermosphere of the northern polar cap was investigated using fabry perot interferometer measurements of the horizontal wind velocity in the lower thermosphere meridian scanning photometer observations of atomic oxygen green line brightness in the lower thermosphere and michelson interferometer records of the infrared meinel oh bands brightness and rotational temperature in the upper mesosphere tidal airglow oscillations in the absence of local solar heating were studied using a superposed epoch analysis of observations obtained around three new moon intervals november 9 22 1993 december 7 20 1993 and january 4 17 1994 in eureka 80 n tidal harmonics were uncovered with an iterated least chi squared fit and their existence in the data tested using a goodness of fit probability against a null hypothesis of no oscillations no single dominant tide was found at all times and altitudes of the winter arctic upper mesosphere and lower thermosphere the horizontal wind velocity of the lower thermosphere exhibited all the first three harmonics of the tide with the largest amplitude oscillations shown by the diurnal component of the meridional wave speed the atmospheric layer near the mesopause that contributes to the oh airglow emission experienced terdiurnal oscillations throughout the winter season theoretical polarization relations for evanescent tides considerations of energy density propagation with altitude and a day by day analysis of the zonal and meridional wind speed and temperature all indicate that the terdiurnal tide observed on november was an evanescent zonally symmetric tide other data indicate propagating tides migrating tides or a mixture of both

first results from the meteor radar at south pole a large 12 hour oscillation with zonal wavenumber one the first mesopause region ca 92 5 km wind measurements from the meteor radar at amundsen scott station at south pole are described measurements are made along four orthogonal azimuth directions approximately 2 from the geographic south pole a large 20 ms 1 oscillation in the northward wind is observed with 12 hour period and zonal wavenumber one a similar wave was observed during august 1 13 1992 at south pole by hernandez et al 1993 using optical methods the predominant semidiurnal tide in the atmosphere is migrating with the apparent motion of the sun with s 2 the s 1 oscillation is interpreted here to result from the nonlinear interaction between the migrating semidiurnal tide and a stationary wave with s 1 the present mechanism represents an alternative to the gravity wave driven pseudotide theory put forth by walterscheid et al 1986 to explain the occurrence of unexpectedly large semidiurnal tidal oscillations at high latitudes

seasonal variations of mlt tides revealed by a meteor radar chain based on hough mode decomposition seasonal variations of different tides in the mesosphere and lower thermosphere are investigated from wind observations of a meteor radar chain on the basis of hough mode decomposition first the observed winds are decomposed into different diurnal semidiurnal and terdiurnal tidal components different seasonal patterns are revealed for each component pronounced semiannual oscillation sao is presented in the diurnal component while latitude dependent seasonal variation is found in the semidiurnal and terdiurnal components at the low midlatitude stations the semiannual annual oscillation is relatively stronger then hough mode decomposition is utilized to extract the dominant tidal modes of each decomposed component it is found that each component is dominated by one of its symmetric tidal modes with strong seasonal dependency apparent sao is observed in the dominant 1 1 mode 2 4 mode is strong in the autumn and winter months after the september equinox based on the extracted results we further map the three dimensional distribution latitude altitude season of each tidal component the mapped results are finally compared with the corresponding values observed by the thermosphere ionosphere mesosphere energetics and dynamics doppler interferometer tidi and modeled from the global scale wave model gswm each mapped tidal component agrees well with corresponding tidi observation in the seasonal variation meanwhile coincidences are found in the seasonal dependency of the diurnal component between the mapped values and the modeled results from gswm while difference between them exists in that of the semidiurnal one

revised global model of thermosphere winds using satellite and ground based observations thermospheric wind data obtained from the atmosphere explorer e and dynamics explorer 2 satellites have been combined with wind data for the lower and upper thermosphere from ground based incoherent scatter radar and fabry perot optical interferometers to generate a revision hwm90 of the hwm87 empirical model and extend its applicability to 100 km comparison of the various data sets with the aid of the model shows in general remarkable agreement particularly at mid and low latitudes the ground based data allow modeling of seasonal diurnal variations which are most distinct at mid latitudes while solar activity variations are now included they are found to be small and not always very clearly delineated by the current data they are most obvious at the higher latitudes the model describes the transition from predominately diurnal variations in the upper thermosphere to semidiurnal variations in the lower thermosphere and a transition from summer to winter flow above 140 km to winter to summer flow below significant altitude gradients in the wind are found to extend to 300 km at some local times and pose complications for interpretation of fabry perot observations

darwin area wave experiment dawex field campaign to study gravity wave generation and propagation 1 a field campaign studying aspects of the atmospheric dynamics from the ground to the lower thermosphere was conducted in australia during october to december 2001 this darwin area wave experiment dawex involved participation from nine institutions in the usa japan and australia and focused on studying wave perturbations in the middle atmosphere in conjunction with detailed observations of tropospheric moist convection the experiment involved extended deployment of six airglow imagers medium frequency radars and a boundary layer wind profiler tropospheric convection was observed by meteorological radars including the australian bureau of meteorology research centre c band polarized radar this paper provides an overview of the experimental setup and also discusses the basic meteorological fields during the experiment including some examples of convective activity near darwin wind and temperature fields extending up into the lower thermosphere were constructed on the basis of campaign observations and the ukmo global meteorological analysis these fields can be used for the modeling of gravity wave propagation through the middle atmosphere

substantial agreement on the timing and magnitude of late holocene ice cap expansion between east greenland and the eastern canadian arctic a commentary on lowell et al 2013

nonlinear interactions in the upper atmosphere the s 1 and s 3 nonmigrating semidiurnal tides 1 a semidiurnal oscillation with zonal wave number s 1 has been observed over the south pole and longitudinal variations of the semidiurnal tide at northern midlatitudes have been ascribed to the presence of nonmigrating tides a three dimensional nonlinear spectral model is used herein to study nonlinear wave wave interaction as a possible mechanism for the generation of nonmigrating tides in the mesosphere and lower thermosphere in particular the s 1 and s 3 nonmigrating semidiurnal tides are studied as a by product of the nonlinear interaction between the semidiurnal s 2 migrating tide and a stationary s 1 planetary wave in the lower and middle atmosphere this process is found to yield significant amplitudes 10 30 m s 1 of the nonmigrating semidiurnal components with s 1 and s 3 in the upper atmosphere comparisons with monthly nonmigrating tidal amplitudes and phases at 95 km derived from high resolution doppler imager and wind imaging interferometer wind measurements from uars show good agreement with the model simulations the effect of the dissipating nonmigrating tides on the zonal mean circulation is found to reinforce that of the migrating component contributing 10 20 m s 1 to the zonal wind field and 5 10 m s 1 to the mean meridional wind field several other wave components are generated through nonlinear interactions including 6 hour tides with zonal wave numbers s 0 1 4 and a semidiurnal oscillation with s 6 these wave components have amplitudes in the range 6 30 m s 1 in the 110 150 km height regime the combination of all nonmigrating tides together with the migrating component suggests significant longitudinal variations in the semidiurnal tide in the e region which may be important for studies of the quiet time generation of ionospheric electric fields by the dynamo mechanism

longitudinal structure of the equatorial ionosphere time evolution of the four peaked eia structure 1 longitudinal structure of the equatorial ionosphere during the 24 h local time period is observed by the formosat 3 cosmic f3 c satellite constellation by binning the f3 c radio occultation observations during september and october 2006 global ionospheric total electron content tec maps at a constant local time map local time tec map referred as lt map can be obtained to monitor the development and subsidence of the four peaked longitudinal structure of the equatorial ionosphere from lt maps the four peaked structure starts to develop at 0800 1000 lt and becomes most prominent at 1200 1600 lt the longitudinal structure starts to subside after 2200 2400 lt and becomes indiscernible after 0400 0600 lt in addition to tec ionospheric peak altitude also shows a four peaked longitudinal structure with variation very similar to tec during daytime the four peaked structure of the ionospheric peak altitude is indiscernible at night with global local time maps of ionospheric tec and peak altitude we compare temporal variations of the longitudinal structure with variations of e b drift from the empirical model our results indicate that the observations are consistent with the hypothesis that the four peaked longitudinal structure is caused by the equatorial plasma fountain modulated by the e3 nonmigrating tide additionally the four maximum regions show a tendency of moving eastward with propagation velocity of several 10 s m s

nonmigrating diurnal tides in the thermosphere 1 horizontal wind measurements from the hrdi and windii instruments on the upper atmosphere research satellite are analyzed to reveal the most prominent nonmigrating diurnal tidal components at 95 km the eastward propagating diurnal tide with zonal wave number s 3 de3 the standing s 0 diurnal oscillation d0 and the westward propagating diurnal tide with s 2 dw2 the strongest de3 occurs primarily during northern hemisphere summer fall with maximum eastward winds near the equator of order 15 ms 1 and is a vertical extension of the s 3 kelvin wave the first antisymmetric mode of de3 dominates during october april with maximum meridional winds near the equator of order 8 ms 1 d0 exists during nearly all months and is nonsymmetric about the equator with maximum northward wind amplitudes in the southern hemisphere of order 7 10 ms 1 dw2 closely resembles the first symmetric propagating mode from classical tidal theory with maximum northward wind amplitudes of order 10 12 ms 1 during september through february the combination of de3 d0 and dw2 with dw1 gives rise to significant longitude variations in the diurnal tide between 40 latitude forcing in the global scale wave model gswm is calibrated according to the above observations thus enabling global estimates of nonmigrating tidal temperatures and other fields for instance it is estimated that the temperature and eastward wind perturbations associated with de3 may be as large as 20k and 35 ms 1 at 145 km and 115 km respectively over the equatorial region during july

variations of the nighttime thermospheric mass density at low and middle latitudes 1 the latitudinal structure of the nighttime thermospheric mass density at 385 km has been investigated using observations made by the accelerometer onboard the champ satellite between 2002 and 2007 the nighttime thermospheric mass density had a clear latitudinal variation there was a local density peak around the geographic equator and two minima at about 30 this nighttime equatorial mass anomaly nema was opposite to the latitudinal variations of the daytime ionospheric equatorial anomaly and thermospheric mass density anomaly as both have minima at the magnetic dip equator and maxima around 20 in magnetic latitudes this anomalous behavior of the nighttime thermospheric mass density had strong local time seasonal hemispheric and solar cycle dependences the largest crest to trough ratio between the peak density at the equator and the minima at the anomaly latitudes 30 occurred between 0000 and 0200 local time the nema appeared to be more pronounced during solstice seasons it was also stronger during solar minimum than during solar maximum in addition under the same geophysical conditions the empirical nrlmsise 00 model shows similar but much weaker nighttime mass density anomaly features at low and middle latitudes a high resolution national center for atmospheric research thermosphere ionosphere mesosphere energetics global circulation model timegcm simulation reproduced most of the observed latitudinal variations of the nighttime mass density as well as the thermospheric midnight temperature maximum mtm model results suggest that superposition of diurnal and semidiurnal migrating tides of modes up to wave number 6 is the likely cause of both the nema and mtm phenomena