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

intra annual variation of wave number 4 structure of vertical e b drifts in the equatorial ionosphere seen from rocsat 1 1 this paper studies the intra annual variation of the wave number 4 structure in the equatorial vertical e b drifts at high solar flux level based on of the rocsat 1 observations during the interval from 1999 to 2004 it is found that the daytime longitudinal structure is significant in northern summer and early autumn but weak in northern winter this is consistent with the intra annual variations of the tidal mode de3 at night the intra annual variation of the wave number 4 structure shows some differences from that in daytime which may relate to different dynamo mechanisms operating in different local time we also found that the wave number 4 structure mainly shifts eastward during daytime in most of months which is coincident with the eastward propagation of the de3 tide however it is largely disturbed near sunrise and sunset we attribute this disturbance as the jumping of the main dynamo region between e and f layers as well as the different dynamo mechanisms in different dynamo regions

observations of the diurnal tide in the mesosphere and lower thermosphere over christmas island atmospheric tidal variations in the mesosphere wind field have been studied extensively using radars most of the climatological studies of the tide have been done at middle and high latitudes previous tropical observations of the diurnal oscillation derived from campaign studies have shown the dominance of the migrating diurnal tide in the mesosphere and lower thermosphere by using wind measurements obtained with a meteor radar system located at christmas island the diurnal tidal behavior in the upper atmosphere of the equatorial pacific has been characterized over several years the data collected from august 1988 to december 1993 are presented in this paper and compared to various model results our observations show the meridional wind component of the diurnal tide maximizes in april near 94 km the observed meridional vertical wavelengths are large and indicate upward propagating energy even though the vertical wavelengths for the zonal diurnal component are also large the phase progression is upward corresponding to downward propagating energy there is considerable interannual and intraseasonal variation in the diurnal amplitudes throughout the year

global ray tracing simulations of the saber gravity wave climatology 1 since february 2002 the saber sounding of the atmosphere using broadband emission radiometry satellite instrument has measured temperatures throughout the entire middle atmosphere employing the same techniques as previously used for crista cryogenic infrared spectrometers and telescopes for the atmosphere we deduce from saber v1 06 data 5 years of gravity wave gw temperature variances from altitudes of 20 to 100 km a typical annual cycle is presented by calculating averages for the individual calendar months findings are consistent with previous results from various satellite missions based on zonal mean saber data for july and zonal mean gw momentum flux from crista a homogeneous and isotropic launch distribution for the grograt gravity wave regional or global ray tracer is tuned the launch distribution contains different phase speed mesoscale waves some of very high phase speed and extremely low amplitudes as well as waves with horizontal wavelengths of several thousand kilometers global maps for different seasons and altitudes as well as time series of zonal mean gw squared amplitudes based on this launch distribution match the observations well based on this realistic observation tuned model run we calculate quantities that cannot be measured directly and are speculated to be major sources of uncertainty in current gw parameterization schemes two examples presented in this paper are the average cross latitude propagation of gws and the relative acceleration contributions provided by saturation and dissipation on the one hand and the horizontal refraction of gws by horizontal gradients of the mean flow on the other hand

diurnal nonmigrating tides from timed doppler interferometer wind data monthly climatologies and seasonal variations 1 timed doppler interferometer tidi measurements of zonal and meridional winds in the mesosphere lower thermosphere are analyzed for diurnal nonmigrating tides june 2002 to june 2005 climatologies of monthly mean amplitudes and phases for seven tidal components are presented at altitudes between 85 and 105 km and latitudes between 45 s and 45 n westward propagating wave numbers 2 3 and 4 the standing diurnal tide and eastward propagating wave numbers 1 2 and 3 the observed seasonal variations agree well with 1991 1994 uars results at 95 km comparisons between the tidi results and global scale wave model gswm and thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm tidal predictions indicate that the large eastward propagating wave number 3 amplitude is driven by tropical tropospheric latent heat release alone in contrast latent heating and planetary wave migrating tidal interactions are equally important to westward 2 and standing diurnal tidal forcing there is good quantitative agreement between tidi and the model predictions during equinox but the latter tend to underestimate the westward 2 and standing diurnal tide during solstice neither model reproduces the observed seasonal variations of the eastward propagating components

tidal variability in the lower thermosphere comparison of whole atmosphere model wam simulations with observations from timed 1 the upper atmosphere and ionosphere exhibit variability on spatial and temporal scales characteristic of tides and planetary waves originating in the lower atmosphere to study their generation vertical propagation possible nonlinear interactions and effects a new whole atmosphere model wam has been developed as part of the integrated dynamics through earth s atmosphere idea project wam is a 150 layer general circulation model based on the us national weather service s operational global forecast system gfs model extended upward to cover the atmosphere from the ground to about 600 km first simulations reveal the presence of migrating and nonmigrating tides modulated at planetary wave periods in the upper atmosphere comparisons with observations from the timed satellite in the lower thermosphere show that wam reproduces the seasonal variability of tides remarkably well including the diurnal eastward harmonic with zonal wavenumber 3 de3 recently implicated in the observed spatial morphology of the ionosphere

the seasonal variation of the propagating diurnal tide in the mesosphere and lower thermosphere part i the role of gravity waves and planetary waves abstract the seasonal variation of the propagating diurnal tide in the mesosphere and lower thermosphere is examined using results from a 2 yr simulation of the extended version of the canadian middle atmosphere model cmam the cmam is shown to be able to reproduce not only the observed semiannual amplitude variation of the tide in the lower thermosphere but also more subtle features such as amplitude maxima that are stronger in march april than in september october a 4 to 6 h shift in phase between winter and summer in the northern hemisphere and a weaker seasonal variation of phase in the southern hemisphere part i of this two part series of papers investigates the importance of two of the mechanisms that have been proposed to explain the observed variation of tidal amplitude namely 1 interactions with small scale gravity waves and 2 interactions with planetary scale waves like the quasi 2 day wave analysis of the tidal momentum and thermodynamic budgets shows that the direct effects of param

seasonal and longitudinal variations of the solar quiet sq current system during solar minimum determined by champ satellite magnetic field observations 1 vector magnetometer observations from the challenging minisatellite payload champ satellite are used to determine the solar quiet sq current system during the recent solar minimum observations from 2006 to 2008 are combined and after removal of a main field model and accounting for field aligned currents the longitudinal and seasonal variation of the sq currents are determined through the method of spherical harmonic analysis comparison with sq currents derived from ground based magnetometers in the african european longitude sector reveals similar amplitudes and seasonal variations indicating that the champ observations can reliably determine the sq current system the seasonal variation is consistent with prior observations during solar minimum conditions and in the northern hemisphere exhibits a primarily annual variation with peak currents during local summer the seasonal variation in the southern hemisphere is characterized by a semiannual variation with the maxima occurring around the equinoxes significant longitudinal variations are also observed and they display a seasonal variability during northern hemisphere summer the predominant feature at local noon is a wave number 1 variation in longitude during the remainder of the year a wave 3 longitudinal structure is observed at this local time the longitudinal variations are considered to be due to a combination of the orientation and strength of the geomagnetic field as well as the tidal winds in the lower thermosphere variations in tidal winds due to nonmigrating tides may influence the dynamo generated electric fields and currents resulting in the observed longitudinal variations of the sq current function

mesospheric momentum flux studies at adelaide australia observations and a gravity wave tidal interaction model abstract we present here the results of an analysis of gravity wave momentum fluxes in the mesosphere and lower thermosphere inferred using a dual beam doppler radar near adelaide australia during june 1984 our analysis reveals that over 70 of the momentum flux and of the inferred zonal drag was due to gravity waves with observed periods less than one hour this suggests that it is the gravity waves with high intrinsic frequencies and small horizontal scales that are most effective at transporting momentum into the middle atmosphere the temporal variations in the momentum flux and flux divergence due to high frequency motions were also examined in detail in addition to daily variability a strong diurnal modulation was observed to occur this was found to be correlated with the phase of large amplitude diurnal tidal motions as a result of these observations a gravity wave tidal interaction model was proposed which accounts for all of the major features of the observed data including a reduction i

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

an empirical model of the earth s horizontal wind fields hwm07 1 the new horizontal wind model hwm07 provides a statistical representation of the horizontal wind fields of the earth s atmosphere from the ground to the exosphere 0 500 km it represents over 50 years of satellite rocket and ground based wind measurements via a compact fortran 90 subroutine the computer model is a function of geographic location altitude day of the year solar local time and geomagnetic activity it includes representations of the zonal mean circulation stationary planetary waves migrating tides and the seasonal modulation thereof hwm07 is composed of two components a quiet time component for the background state described in this paper and a geomagnetic storm time component dwm07 described in a companion paper

origin and distribution of daytime electron density irregularities in the low latitude f region electron density irregularities on the dayside in the low latitude f region are understood as remnants or fossils of nighttime plasma bubbles we provide observational evidence of the connection of daytime irregularities to nighttime bubbles and the transport of the daytime irregularities by the vertical motion of the background ionosphere the distributions of irregularities are derived using the measurements of the ion density by the first republic of china satellite from march 1999 to june 2004 the seasonal and longitudinal distributions of daytime and nighttime irregularities in low latitudes show a close similarity the high occurrence rate of daytime irregularities at the longitudes where strong irregularities occur frequently at night provides strong evidence of the association of daytime irregularities with nighttime bubbles nighttime irregularities are concentrated in the equatorial region whereas daytime irregularities spread over broader latitudes the seasonal and longitudinal variation of the latitudinal spread of daytime irregularities is consistent with the morphologies of plasma density and vertical plasma velocity the zonal wave number 4 pattern which corresponds to that in plasma density is identified in the distribution of daytime irregularities these observations lead to the conclusion that the morphology of daytime irregularities in the low latitude f region is dominated by the morphology of bubbles at night and the ionospheric fountain process on the dayside

direct observations of nonmigrating diurnal tides in the equatorial thermosphere 1 we present direct observations of nonmigrating diurnal tides in the 90 270 km range inferred from the upper atmosphere research satellite uars wind imaging interferometer windii a prominent zonal wavenumber 4 appears in daytime zonal winds extending to 180 km we interpret this signature as an eastward propagating diurnal wavenumber 3 de3 viewed from the satellite perspective this evidence of the extended upward propagation of de3 demonstrates that it acts as a direct coupling agent between the troposphere and the thermosphere and f region in addition to its role in the e region dynamo

nonmigrating semidiurnal tide over the arctic determined from timed doppler interferometer wind observations received 25 june 2009 revised 30 october 2009 accepted 5 november 2009 published 30 march 2010 1 the timed doppler interferometer tidi on the nasa thermosphere ionosphere mesosphere energetics and dynamics timed satellite has been measuring horizontal winds in the mesosphere and lower thermosphere mlt since 2002 because of the high inclination of the timed orbit tidi measures the horizontal winds from pole to pole every orbit this paper presents the first assessment of the spatial structure and temporal evolution of the nonmigrating semidiurnal tides over the arctic determined from the tidi wind measurements and a comparison of the structure of the nonmigrating semidiurnal tide between the arctic and antarctic the nonmigrating semidiurnal tides were determined as a 60 day average based on the yaw cycles of the spacecraft the nonmigrating semidiurnal tidal wind field over the arctic comprises mainly the westward propagating zonal wave numbers1 w1 and3 w3 andstandingzonalwavenumber0 s0 modes thew1modeis the most prominent maximizing above 90 km poleward of 60 n during the yaw interval ranging from mid march to mid may while this mode exhibits a slight amplitude increase toward the north pole during this interval its phase is nearly constant with latitude the s0 mode is enhanced over two yaw intervals ranging from mid january to mid may but its amplitude decreases toward the north pole compared to the w1 semidiurnal tide over the antarctic that over the arctic is smaller in amplitude of less extended duration achieves maximum amplitudes at higher altitudes by 10 km and exhibits a weaker amplitude increase toward the pole these differences likely result from differences in excitation mechanisms and efficiency and or in propagation conditions in the two responses for the nonmigrating semidiurnal tides between the arctic and antarctic

comparative study of short term diurnal tidal variability examination of the simultaneous temperature measurement from the sounding of the atmosphere using broadband emission radiometry saber instrument on board the thermosphere ionosphere mesosphere energetics and dynamics timed satellite not only confirms the existence of the inversion layer but also reveals the global nature of the inversion suggesting the presence of a transient planetary wave in the mesosphere the large tidal variability therefore is probably a consequence of the interaction between the transient planetary wave and tides this possibility is investigated by using the ncar thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm and by comparing model results with the lidar saber and timed doppler interferometer tidi measurements with a large transient planetary wave specified at the model lower boundary the model is able to produce strong diurnal tidal variability comparable to that from the lidar observation and the modeled temperature inversion is similar to that from the saber measurement the model results suggest that the planetary tidal wave interaction excites nonmigrating tides and modulates the gravity modes and or the rotational modes of the diurnal migrating tide among the nonmigrating tides the diurnal zonally symmetric s 0 component is the strongest and its interaction with the planetary wave leads to a strong diurnal eastward wave number 1 component

wavenumber 4 patterns of the total electron content over the low latitude ionosphere 1 the global ionospheric maps gims produced by jpl are used to investigate the longitudinal structure of the low latitude ionosphere as a proxy of the ionization parameter at low latitudes the latitudinally integrated total electron content itec is first extracted from low latitude gims and then fourier filtered to obtain the wavenumber 4 components we then study in detail the diurnal seasonal and solar cycle variations of the wave patterns it is found that the wavenumber 4 patterns are intense and well developed in boreal summer and early boreal autumn but quite weak in boreal winter this seasonal variation is consistent with that of the zonal wind of the non migrating tide mode de3 we also found that the wavenumber 4 patterns shift eastward with a shifting speed that is smaller in daytime than at night this is attributed to the contribution of both the eastward propagation of de3 in e region and the zonal e b ion drifts in f region our results support the suggestion that the longitudinal wavenumber 4 structure of the low latitude ionosphere should be originated from the non migrating tide mode de3

connections between deep tropical clouds and the earth s ionosphere 1 we report on a series of simulations with the national center for atmospheric research ncar thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm which were designed to replicate and facilitate the interpretation of the longitudinal structure discovered in image satellite airglow observations of the equatorial ionization anomaly eia at the far ultraviolet fuv 135 6 nm wavelength during march april 2002 equinox our time gcm results indicate that the four peaked longitudinal variation in the eia observed by image fuv near 20 00 local solar time can be explained by the effects of an eastward propagating zonal wavenumber 3 diurnal tide de3 that is excited by latent heat release associated with raindrop formation in the tropical troposphere

solar tides as revealed by measurements of mesosphere temperature by the mls experiment on uars abstract temperatures between 25 and 86 km measured by the microwave limb sounder mls experiment on the upper atmosphere research satellite uars are analyzed to delineate diurnal semidiurnal and terdiurnal tidal structures and stationary planetary waves these fourier components are determined from temperatures averaged in bins covering 5 latitude 30 longitude and 1 h in local time this study confirms the presence of diurnal nonmigrating tides with zonal wavenumbers s 0 2 3 s 0 s 0 implying westward eastward propagation and semidiurnal tides with s 1 and 3 and some components of lesser importance that were previously determined from uars wind measurements near 95 km the seasonal latitudinal and height structures of these components are now revealed and utilized to aid in interpreting their behaviors and ascertaining their origins new discoveries include the terdiurnal s 2 and s 4 components and trapped nonmigrating diurnal tides with s 0 and s 2 the former are like

observations of a nonmigrating component of the semidiurnal tide over antarctica 1 data obtained from the mf radars situated at davis syowa and rothera in antarctica are used to detect a nonmigrating component of the semidiurnal tide in the mesosphere and lower thermosphere these radars are at similar latitudes and so share a common migrating tidal component by fitting semidiurnal tide vectors to each stations data and performing subtractions of these vectors for pairs of stations the migrating component can be removed and the difference between the nonmigrating components revealed non zero differences in the summer months december to march indicate the presence of a significant nonmigrating component modeling studies and observations at other sites suggest that it is most likely the westward propagating wavenumber 1 nonmigrating component that is contributing to the semidiurnal tide the data presented here are found to be consistent with this hypothesis a climatology of this nonmigrating component is presented and discussed comparisons with the global scale wave model suggest that latent heat release is not a significant forcing mechanism at these heights and latitudes

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

tidal signatures and aliasing in temperature data from slowly precessing satellites 1 thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm data are used to simulate tidal patterns in satellite borne observations of the mesosphere and lower thermosphere mlt region the results are given for the measurement geometry of the sounding of the atmosphere using broadband emission radiometry saber instrument though the technique is applicable to any satellite based instrument time gcm tides are sampled along the instrument measurement track and analyzed in terms of ascending descending orbit node differences our simulations show a significant aliasing e g of migrating and nonmigrating diurnal and semidiurnal components into tidal fields of observed zonal wavenumbers s 0 above the mesopause the model tides induce a 10 k bias in daily means of zonally averaged temperatures an estimate of the tide induced vertical displacement of air parcels is given assuming tidal motions are adiabatic corresponding signatures are expected to be present in mlt observations of chemical species addressing tidal sampling issues is of general interest for comparing satellite observations with models climatologies and other measurements

high resolution vertical e b drift model derived from rocsat 1 data 1 the measurements of vertical ion velocity from the first republic of china satellite rocsat 1 provide a unique database for the development of an annually and longitudinally high resolution vertical plasma drift model in the equatorial ionosphere currently the rocsat 1 based empirical vertical drift models are available for three seasons equinox and solstices however the vertical drift patterns are not precisely divided by the three seasons a monthly vertical drift model with high longitudinal resolution is desirable to accurately model the low latitude ionosphere and to identify the coupling between the ionosphere and atmospheric tide here we introduce an empirical vertical drift model derived by using the rocsat 1 data in three solar flux conditions f 10 7 180 under k p 3 the local time day of the year and longitude of the model are binned by 15 min 1 month and 10 respectively under each solar flux condition our vertical drift model is validated by comparing the model with the measurements of the vertical drift velocity at the jicamarca radio observatory the characteristics and variability of the vertical drift are briefly discussed

nonmigrating semidiurnal and diurnal tides at 95 km based on wind measurements from the high resolution doppler imager on uars 1 for more than a decade derived results from the high resolution doppler imager hrdi on uars have provided an enormous amount of new and invaluable information on the global variability of atmospheric winds these and other results have given added impetus to theoretical modeling efforts until recent years the large majority of investigations have focused on migrating tides and now more results on nonmigrating tides have become available we provide new results for semidiurnal and diurnal nonmigrating tides based on data from hrdi at 95 km much of these results have not been obtained before and they are substantially different from those that have been previously reported our amplitudes are usually significantly larger with more periodicities in both day of year and latitude than results that have previously appeared in the literature we also find components up to longitude wave number 3 that are significant and have not been presented before and that traveling components of larger longitude wave numbers 4 5 and 6 can reach several m s in amplitude we compare our results with earlier results based on hrdi measurements and from selected models

nonmigrating diurnal tides in the equatorial middle atmosphere abstract data from the nimbus 7 limb infrared monitor of the stratosphere lims are used to extend the analysis of diurnal tides in the middle atmosphere to include the zonally symmetric and eastward propagating components these modes show vertical and meridional structures that are generally consistent with the predictions of linear tidal theory the zonal and meridional wind fields are calculated from the tidal temperatures diurnal perturbations in lims temperature and derived winds agree well with equinoctial model calculations comparisons with day night differences of radiosonde temperature and rocket winds show qualitative agreement in vertical structure and amplitude the zonally symmetric and eastward migrating tidal components show a higher degree of temporal variability than the sun synchronous component these modes at times contribute substantially to the diurnal signal in wind and temperature with combined amplitudes equal to or in excess of the amplitude of the main migrating diurnal tid

tidal gravity wave interactions and their influence on the large scale dynamics of the middle atmosphere model results results from a modified version of the quasi geostrophic model of mclandress and mcfarlane 1993 in combination with the tidal model of forbes 1982a b are used to delineate the role of tides in modulating gravity wave momentum fluxes and the ensuing effects on the large scale circulation of the middle atmosphere for solstice conditions the influence of the tidal wind fields on the location and strength of the gravity wave drag is strongest in the mesosphere and lower thermosphere where the tidal winds are of the same order as the zonal mean component due to the nonlinear dependence on the local wind speed the daily mean gravity wave drag in the model can differ significantly depending on whether or not tidal variations are included at middle and low latitudes these differences are largest and occur as a result of the filtering effects of the shorter vertical wavelength diurnal tide at more polar latitudes where the longer wavelength semidiurnal tide dominates a slight increase in drag occurs the interaction between the tidal wind fields and the localized orographic gravity wave momentum flux has important consequences for the in situ generation of planetary scale disturbances in particular the amplification of stationary planetary wavenumber 1 is enhanced by the presence of tides in addition forcing of nonmigrating tidal modes is predicted to occur as a result of the localized drag

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seasonal and latitudinal variations of the electron density nonmigrating tidal spectrum in the topside ionospheric f region as resolved from champ observations in this study we present for the first time the nonmigrating tidal spectrum for the electron density in the topside ionosphere on global scale for different seasons at both solar maximum and minimum conditions the electron density observations from the champ challenging minisatellite payload satellite provide evidence for prominent nonmigrating tides at different latitude regions at middle and high latitudes the most prominent diurnal tides are de1 d0 and dw2 as well as semidiurnal tides sw1 and sw3 preferably during equinox seasons de1 is only found in the northern middle and high latitudes while d0 and dw2 are much stronger in the southern hemisphere these tides are believed to be driven by the thermospheric winds through ion neutral interactions at equatorial and low latitude regions the most prominent diurnal tides are de2 and de3 de2 is found to be present at low latitude regions throughout the whole year with larger amplitudes in the southern hemisphere while de3 shows largest amplitudes symmetric above the dip equator at the equatorial ionization anomaly eia crest region during september equinox a general antiphase behavior between the eia crest and trough is observed for the tides de3 de2 dw2 and sw3 we consider this as strong evidence for the modulation of the eia electron density by the e layer zonal electric field via the ion fountain effect an exception is the tidal component d0 which exhibits antiphase variations between the two hemispheres the phase value at the equatorial trough is halfway between those of the two hemispheres presently we cannot give an explanation for it and study concerning special model effort is further needed

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

comparison of champ and time gcm nonmigrating tidal signals in the thermospheric zonal wind 1 four years 2002 2005 of continuous accelerometer measurements taken onboard the champ satellite orbit altitude 400 km offer a unique opportunity to investigate the thermospheric zonal wind on a global scale recently we were able to relate the longitudinal wave 4 structure in the zonal wind at equatorial latitudes to the influence of nonmigrating tides and in particular to the eastward propagating diurnal tide with zonal wave number 3 de3 the de3 tide is primarily excited by latent heat release in the tropical troposphere in deep convective clouds in order to investigate the mechanisms that couple the tidal signals to the upper thermosphere we undertook a comparison with the thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm developed at the national center for atmospheric research ncar we ran the model for a day in march june september and december and applied the same processing steps to the model output as was done for the champ tidal analysis the main results of the comparison can be summarized as follows 1 time gcm simulations do not correctly reproduce the observed intra annual variations of de3 and the eastward propagating diurnal tide with zonal wave number 2 de2 2 simulations of de3 for june are more successful both time gcm and champ show an increase in de3 amplitudes with decreasing solar flux level 3 the amplitudes of the simulated westward propagating diurnal tide with zonal wave number 2 dw2 and the standing diurnal tide d0 increase with increasing solar flux in june the predicted dependence of dw2 and do on solar flux is also observed by champ

winter temperature tides from 30 to 110 km at mcmurdo 77 8 s 166 7 e antarctica lidar observations and comparisons with wam we provide the first characterization of diurnal and semidiurnal thermal tides in temperature from 30 to 110 km in the winter season may through august at mcmurdo 77 8 s 166 7 e antarctica the observations were made with an fe boltzmann temperature lidar in 2011 and 2012 over 330 h of winter data are compiled into a composite day of temperature perturbations that significantly reduce the incoherent wave effects while preserving the coherent tidal signatures both diurnal and semidiurnal tides have small amplitudes less than 3 k below 100 km with vertical wavelengths of 29 and 23 km respectively a new finding of this study is the fast growth of diurnal and semidiurnal tidal amplitudes above 100 km to at least 15 k near 110 km exceeding that of the freely propagating tides originating from the lower atmosphere such fast growth exists for all kp index cases and diurnal amplitude increases to 15 30 k at 110 km with larger kp indices corresponding to larger tidal amplitudes and faster growth rates the slopes of diurnal tidal phases become steeper above 100 km and the tidal phases barely change with altitude from 100 to 106 km the tidal growth behavior is reproduced in the whole atmosphere model wam with phases comparable to the observations but magnitudes significantly underestimated wam compares reasonably well with the observations below 100 km the observed significant amplitude increases and phase structure changes suggest additional tidal sources near or above 100 km which deserve future investigation

sources of nonmigrating tides in the tropical middle atmosphere 1 temperature measurements from the cryogenic infrared spectrometers and telescopes for the atmosphere crista experiment taken during the u s space shuttle mission sts 66 in november 1994 provide a variety of zonally symmetric and asymmetric tidal signatures in the altitude range from 40 90 km the most prominent zonally asymmetric tidal pattern is identified to be the westward propagating nonmigrating diurnal tide of zonal wavenumber 2 s 2 this mode has an amplitude of approximately half the amplitude of the migrating s 1 component of the diurnal tide the observational findings are compared to model results from the global scale wave model gswm and from the thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm gswm and time gcm account for different tidal sources and therefore allow an analysis of the tidal forcing responsible for the observed signatures the gswm tidal forcing in the model version used is based upon latent heat release associated with tropical deep convection while nonmigrating tides in the time gcm are predominantly forced by nonlinear interactions between the migrating diurnal tide and stationary planetary waves it is shown that the latter mechanism forces a large part of the s 2 mode while the stationary zonally uniform s 0 diurnal nonmigrating tide is mainly driven by latent heat release this result suggests that dynamical models for the mesosphere lower thermosphere mlt region need to account for the tropospheric latent heat source and stationary planetary wave activity in order to predict realistic longitudinal diurnal tidal variability

global ionospheric response to nonmigrating de3 and de2 tides forced from below 1 in this paper we present the global spatial structure and seasonal variability of the cosmic electron density response to the forced from below de3 and de2 tides during the period january 2008 to march 2009 the cosmic electron density at fixed altitudes and saber temperatures were utilized in order to define the ionospheric de3 and de2 tidal response to the de3 and de2 temperature tides coming from below the tidal waves from both data sets have been extracted by the same data analysis method the latitude structure of the ionospheric response for heights up to 450 500 km is distributed on both sides of the dip equator at about 30 modified dip latitude above 500 km the response is approximately confined over the equator two altitude regions of enhanced ionospheric response are found an upper level response above 300 km and a bottom level one below 250 km the two regions are separated by a narrow altitude zone with no tidal response the different phase structure of the ionospheric response in both altitude regions suggests that 1 the upper level response is mainly due to the de3 de2 modulated vertical plasma drift and 2 the bottom level response is complex and in all likelihood is caused by more than one mechanism

first measurements of thermal tides in the summer mesopause region at antarctic latitudes 1 we present the first detection of thermal tides in the middle atmosphere at polar latitudes in summer the iap iron lidar is in operation in davis 69 s 78 e antarctica since december 2011 and measures temperatures in the height range 84 96 km with an accuracy of 1 3 k after 1 hour integration with an effective altitude resolution of 1 km iron densities are observed from 75 140 km we analyze 171 hours of observations in the period 11 28 january 2011 and find strong tidal modulations in fe density and temperatures typical amplitudes of thermal tides are 2 4 k for both the diurnal and semidiurnal component the diurnal tide is larger smaller than the semidiurnal component below above 90 km the phase of the diurnal tide decreases with altitude by 1 3 h km which corresponds to a vertical wavelength of 30 km a similar phase progression is observed in fe densities extending below and above the height range of temperature measurements the overlay of diurnal and semidiurnal components leads to tidal modulations of up to 6 k for temperatures and up to 4000 ccm 40 for fe number densities these modulations are much larger compared to most simulations and point to some missing processes in tidal modeling

longitudinal variation of f region electron density and thermospheric zonal wind caused by atmospheric tides 1 simultaneous observations of the electron density and the zonal wind obtained by the champ satellite at 400 km are used to study systematic longitudinal variations the time period selected is august september 2004 allowing observations at pre noon and post sunset hours the equatorial ionization anomaly eia and the zonal delta wind deviation from zonal average show a persistent and dominant 4 peaked longitudinal variation we interpret this structure as caused by the wavenumber 3 nonmigrating diurnal tide de3 the eia and the zonal delta wind exhibit extrema at about the same longitudes but while the intensifications of the eia and the delta wind are in phase during the evening hours they are out of phase in the morning possible coupling mechanisms are investigated

tidal wind mapping from observations of a meteor radar chain in december 2011 1 this article proposes a technique to map the tidal winds in the mesosphere and lower thermosphere mlt region from the observations of a four station meteor radar chain located at middle and low latitudes along the 120 e meridian in the northern hemisphere a 1 month dataset of the horizontal winds in the altitude range of 80 100 km is observed during december 2011 we first decompose the tidal winds into mean diurnal semidiurnal and terdiurnal components for each station it is found that the diurnal semidiurnal components dominate at the low latitude midlatitude stations their amplitudes increase at lower altitudes and then decrease at higher altitudes after reaching a peak in the mlt region hough functions of the classical tidal theory are then used to fit the latitudinal distribution of each decomposed component the diurnal component is found to be dominated by the first symmetric 1 1 mode yet for the semidiurnal and terdiurnal components the corresponding dominant modes are the second symmetric modes 2 4 and 3 5 and considerable contributions are also from the first antisymmetric modes 2 3 3 4 and second antisymmetric modes 2 5 3 6 based on the decomposed results we further map the horizontal winds in the domains of latitude altitude and local time the mapped horizontal winds successfully reproduce the local time versus altitudinal distributions of the original observations at the four stations thus we conclude that the meteor radar chain is useful to monitor and study the regional characteristics of the tidal winds in the mlt region

vertical connection from the tropospheric activities to the ionospheric longitudinal structure simulated by a new earth s whole atmosphere ionosphere coupled model 1 this paper introduces a new earth s atmosphere ionosphere coupled model that treats seamlessly the neutral atmospheric region from the troposphere to the thermosphere as well as the thermosphere ionosphere interaction including the electrodynamics self consistently the model is especially useful for the study of vertical connection between the meteorological phenomena and the upper atmospheric behaviors as an initial simulation using the coupled model we have carried out a 30 day consecutive run in september the result reveals that the longitudinal structure of the f region ionosphere varies on a day to day basis in a highly complex way and that a four peak structure of the daytime equatorial ionization anomaly eia similar to the recent observations appears as an averaged feature the simulation reproduces and thus confirms the vertical coupling processes proposed so far with respect to the formation of the averaged eia longitudinal structure the excitation of solar nonmigrating tides in the troposphere their propagation through the middle atmosphere and the modulation of ionospheric dynamo which in turn affects eia generation the simulation result indicates that not only the ionospheric averaged longitudinal structure but also the day to day variation can be modulated significantly by the lower atmospheric effect

vertical exb drifts from radar and c nofs observations in the indian and indonesian sectors consistency of observations and model in this paper we analyze vertical exb drifts obtained from the doppler shifts of the daytime 150 km radar echoes from two radar stations located off the magnetic equator namely gadanki in india and kototabang in indonesia and compare those with corresponding coupled ion neutral dynamics investigation cindi observations onboard the c nofs satellite and the scherliess fejer model in an effort to understand to what extent the low latitude vertical exb drifts of the 150 km region represent the f region vertical exb drifts the radar observations were made during 9 16 lt in january june july and december 2009 a detailed comparison reveals that vertical exb drifts observed by the radars at both locations agree well with those of cindi and differ remarkably from those of the model importantly the model and observed drifts show large disagreement when the observed drifts are either large or downward further while the cindi as well as the radar observations from the two longitudes are found to agree with each other on the average they differ remarkably on several occasions when compared on a one to one basis the observed difference in detail is due to measurements made in different volumes linked with latitudinal and or longitudinal differences and underlines the role of neutral dynamics linked with tides and gravity waves in the two longitude sectors on the respective vertical exb drifts the results presented here are the first of their kind and are expected to have wider applications in furthering our understanding on fine scale longitudinal variabilities in the ionosphere in general and ionospheric electrodynamics in the indian and indonesian sectors in particular

diurnal tide in the equatorial middle atmosphere as seen in lims temperatures abstract the distribution of day night temperature differences in the middle atmosphere determined by the nimbus 7 lims experiment is described day night differences maximize at and are approximately symmetric about the equator successive centers of opposite sign increase in amplitude with altitude the pattern having a vertical wavelength of 25 km profiles of rocket meridional wind at kwajalein 8 7 n and ascension island 8 0 s taken near local noon and averaged over the lims data period exhibit maxima which support the tidal interpretation of the equatorial temperature pattern these characteristics are in general agreement with previous observational and theoretical results for the solar driven diurnal tide substantial time variations in amplitude and in location of the temperature maxima are observed the diurnal tide near the equatorial stratopause appears to be influenced by the phase of the semiannual oscillation

ground magnetic effects of the equatorial electrojet simulated by the tie gcm driven by timed satellite data quiet time daily variations of the geomagnetic field near the magnetic equator due to the equatorial electrojet are simulated using the national center for atmospheric research ncar thermosphere ionosphere electro dynamics general circulation model tie gcm and compared to those observed by ground based magnetometers simulations are run both with and without tidal forcing at the height of the model lower boundary 97 km when the lower boundary forcing is off the wind that generates an electro motive force in the model is primarily the vertically non propagating diurnal tide which is excited in the thermosphere due to daytime solar ultra violet heating the lower boundary tidal forcing adds the effect of upward propagating tides which are excited in the lower atmosphere and propagate vertically to the thermosphere the main objective of this study is to evaluate the relative importance of these thermospherically generated tides and upward propagating tides in the generation of the equatorial electrojet fairly good agreement is obtained between model and observations when the model is forced by realistic lower boundary tides based on temperature and wind measurements from the thermosphere ionosphere mesosphere energetics and dynamics timed satellite as determined by wu et al 2012 the simulation results show that the effect of upward propagating tides increases the range of the geomagnetic daily variation in the magnetic northward component at the magnetic equator approximately by 100 it is also shown that the well known semiannual change in the daily variation is mostly due to upward propagating tides especially the migrating semidiurnal tide these results indicate that upward propagating tides play a substantial role in producing the equatorial electrojet and its seasonal variability

tidal signatures in temperature data from crista 1 mission temperature measurements in the stratosphere and mesosphere were taken during the first cryogenic infrared spectrometers and telescopes for the atmosphere crista 1 mission using co2 emissions these measurements range from 13 to close to 100 km and individual temperature measurements have a precision of 1 k the crista orbit was circular at an inclination of 57 so local time variations during the 7 day mission were small for a given latitude and orbit leg zonal averages of the data show significant structure in the vertical and as a function of latitude temperature differences between the zonal mean data from the ascending and descending portions of the orbit are of the form expected from the diurnal tide the maximum zonal mean difference is 20 k and occurs over the equator at an altitude of 75 km zonal variations in the temperature difference indicate that the tidal amplitude is not uniform at all longitudes at the equator the maximum amplitude 30 k appears over the african sector and the minimum 10 k over the pacific sector this variation is most likely a nonmigrating wavenumber 2 diurnal tide although other less plausible possibilities exist to facilitate comparisons with model results the temperature variations are converted to equivalent vertical displacements assuming the tidal motions are adiabatic such an approach is appropriate in the mesosphere where diurnal variations due to radiative effects are small and reduces the dependence of the measured temperature amplitude on the background temperature profile equivalent vertical displacements are also calculated using results from the global scale wave model for the most part the model results and observations are in excellent qualitative and good quantitative agreement from the tropopause to the mesopause however the observed vertical wavelength is smaller and its amplitude in terms of equivalent displacement is smaller in the upper mesosphere than that in the model the decrease in amplitude is consistent with that expected from the transition from equinox to solstice conditions

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

simulated equinoctial asymmetry of the ionospheric vertical plasma drifts 1 this paper studies the influence of the lower thermospheric tidal winds below 105 km on the equinoctial asymmetry of the equatorial vertical e b plasma drifts v using theoretical ionospheric dynamo model ii of the institute of geology and geophysics chinese academy of sciences tidm iggcas ii and tidal winds below 105 km from thermosphere ionosphere mesosphere energetics dynamics satellite doppler interferometer tidi observations although a series of other nonmigrating tides also affect the v asymmetry the simulated equinoctial asymmetry in v are mainly driven by the migrating diurnal tide dw1 migrating semidiurnal tide sw2 de3 and dw2 nonmigrating tides the asymmetry in daytime v varies with local time and longitude and mainly shows three features first the simulated daytime v during the march equinox is larger than that during the september equinox in most of longitudinal sectors this asymmetry is mainly driven by the semiannual oscillation sao of the migrating diurnal tide in the tropical mesosphere lower thermosphere mlt region and the equinoctial asymmetry of the migrating semidiurnal tide also plays an important role in the generation of this asymmetry second the daytime v asymmetry in the eastern hemisphere is more significant than that in the western hemisphere our simulation suggests that the longitudinal variations of the geomagnetic fields and dw2 tides play important roles in the generation of this hemisphere difference third there is an obvious wave number 4 longitudinal structure in the v asymmetry our simulation suggests that this wave number 4 structure is mainly driven by the equinoctial asymmetry of the de3 tide

intra annual variability of the low latitude ionosphere due to nonmigrating tides 1 in situ plasma density measurements from the champ satellite between about 350 420 km altitude are used to delineate intra annual variations in the longitudinal structure of the f region ionosphere it is shown that the longitude structures during mid day local times are dominated by the space based longitudinal wavenumbers ks 2 4 and 3 in january july and december respectively these conform to the same dominating ks values characterizing solar thermal tide zonal winds in the dynamo region namely the westward propagating semidiurnal tide with planetary fixed zonal wavenumber s 4 sw4 and the eastward propagating diurnal tides with s 3 de3 and s 2 de2 respectively de3 is the dominating tide during the other months the results presented indicate that nonmigrating tides other than de3 may significantly impact the longitudinal structure of the low latitude ionosphere during certain months

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

interannual variability in the longitudinal structure of the low latitude ionosphere due to the el nino southern oscillation 1 the ratio of monthly median fof2 values between the ionosondes at maui 20 8 n 156 e geographic 21 2 n 90 4 e geomagnetic and yamagawa 31 2 n 130 6 e geographic 20 6 n 160 9 e geomagnetic from january 1960 to june 1993 are used to investigate interannual variability in the wave 4 longitudinal structure of the low latitude f region ionosphere analysis of global positioning system total electron content between january 1998 and december 2008 reveals that the ratio between these two locations is a suitable proxy for the amplitude of the wave 4 longitudinal structure in the northern hemisphere significant interannual variability is present in the fof2 ratio after removing the solar cycle and intra annual variability the remaining variability is thought to be due in part to changes in atmospheric and oceanic circulations arising from the el nino southern oscillation enso wavelet analysis reveals that similar periodicities and occurrence times exist for the fof2 ratio monthly anomalies and sea surface temperature anomalies represented by the oceanic nino index oni furthermore the yearly oni extreme value is well correlated with the extreme value of the fof2 ratio monthly anomalies in the subsequent 5 months this surprising connection is attributed to changes in tropospheric convection and hence latent heating associated with changing sea surface temperatures due to the enso changing distributions of latent heat tidal forcing are thought to induce changes in the strength of the upward and eastward propagating diurnal tide with zonal wave number s 3 de3 which subsequently produces the observed changes in the amplitude of the wave 4 longitudinal structure through modulation of the electric fields generated by the dynamo mechanism in the ionospheric e region our results demonstrate that there is significant interannual variability in the ionospheric wave 4 longitudinal structure and further indicate that the enso phenomenon represents a source of ionospheric variability which has previously not been considered

planetary waves in coupling the stratosphere and mesosphere during the major stratospheric warming in 2003 2004 1 the vertical coupling of the stratosphere mesosphere system through quasi stationary and traveling planetary waves during the major sudden stratospheric warming ssw in the arctic winter of 2003 2004 has been studied using three types of data the uk met office ukmo assimilated data set was used to examine the features of the global scale planetary disturbances present in the winter stratosphere of the northern hemisphere sounding the atmosphere using broadband emission radiometry saber satellite measurements were used as well for extracting the stationary planetary waves in the zonal and meridional winds of the stratosphere and mesosphere radar measurements at eight stations four of them situated at high latitudes 63 69n and the other four at midlatitudes 52 55n were used to determine planetary waves in the mesosphere lower thermosphere mlt the basic results show that prior to the ssw the stratospheremesosphere system was dominated by an upward and westward propagating 16 day wave detected simultaneously in the ukmo and mlt zonal and meridional wind data after the onset of the ssw longer period 22 24 days oscillations were observed in the zonal and meridional mlt winds these likely include the upward propagation of stationary planetary waves from below and in situ generation of disturbances by the dissipation and breaking of gravity waves filtered by stratospheric winds citation pancheva d et al 2008 planetary waves in coupling the stratosphere and mesosphere during the major stratospheric warming in 2003 2004 j geophys res 113 d12105 doi 10 1029 2007jd009011

underwater acoustic signatures of glacier calving climate driven ice water interactions in the contact zone between marine terminating glaciers and the ocean surface show a dynamic and complex nature tidewater glaciers lose volume through the poorly understood process of calving a detailed description of the mechanisms controlling the course of calving is essential for the reliable estimation and prediction of mass loss from glaciers here we present the potential of hydroacoustic methods to investigate different modes of ice detachments high frequency underwater ambient noise recordings are combined with synchronized high resolution time lapse photography of the hans glacier cliff in hornsund fjord spitsbergen to identify three types of calving events typical subaerial sliding subaerial and submarine a quantitative analysis of the data reveals a robust correlation between ice impact energy and acoustic emission at frequencies below 200 hz for subaerial calving we suggest that relatively inexpensive acoustic methods can be successfully used to provide quantitative descriptions of the various calving types

global distribution and interannual variations of mesospheric and lower thermospheric neutral wind diurnal tide 1 migrating tide 1 using the timed doppler interferometer tidi mesospheric and lower thermospheric neutral wind multiyear data set 2002 2007 and ncar time general circulation models gcm 1 2 annual run results 2002 2005 at the tidi sampling points we study the migrating diurnal tide s global distribution interannual and seasonal variations in connection with the mean zonal wind interannual variations a strong quasi biennial oscillation qbo effect on the diurnal tide was observed in the tidi data and reproduced to a lesser degree in the time gcm run the migrating diurnal tide amplitude is larger during the eastward phase of the stratospheric qbo and weaker during the westward phase westward mesospheric equatorial mean zonal winds appeared during the eastward phase of the stratospheric qbo in 2002 2004 and 2006 the strongest qbo effect on both the migrating diurnal tide and mean zonal winds was observed during the march equinox the stronger tides may be related to the weaker gravity wave filtering in the stratosphere during the eastward phase stratospheric qbo the tidi data also exhibit large interhemispheric asymmetry the westward mean zonal winds in the mesosphere appeared to be associated with the enhanced diurnal tide the time gcm 1 2 diurnal tide amplitudes are in general smaller than those observed by the tidi instrument limited vertical spatial resolution for the time cgm 1 2 is suggested as the cause future improvements are expected with a higher spatial resolution in the model