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

ionospheric electron density inversion for global navigation satellite systems radio occultation using aided abel inversions the abel inversion of ionospheric electron density profiles with the assumption of spherical symmetry applied for radio occultation soundings could introduce a greater systematic error or sometimes artifacts if the occultation rays trespass regions with larger horizontal gradients in electron density the aided abel inversions have been proposed by considering the asymmetry ratio derived from ionospheric total electron content tec or peak density nmf2 of reconstructed observation maps since knowledge of the horizontal asymmetry in ambient ionospheric density could mitigate the inversion error here we propose a new aided abel inversion using three dimensional time dependent electron density ne based on the climatological maps constructed from previous observations as it has an advantage of providing altitudinal information on the horizontal asymmetry improvement of proposed ne aided abel inversion and comparisons with electron density profiles inverted from the nmf2 and tec aided inversions are studied using observation system simulation experiment osse comparison results show that all three aided abel inversions improve the ionospheric profiling by mitigating the artificial plasma caves and negative electron density in the daytime e region the equatorial ionization anomaly crests in the f region become more distinct the statistical results show that the ne aided abel inversion has less mean and rmse of error percentage above 250 km altitudes and the performances for all aided abel inversions are similar below 250 km altitudes

paleointensity of the geomagnetic field from dated lavas of the chaine des puys france 1 7 12 thousand years before present paleointensities were determined by the thellier method for six dated lava flows from the chaine des puys france with ages from 7 to 12 ka ka kiloannum before present the three younger flows overlap the archaeomagnetic period for europe and the older flows extend the record to more ancient times our results support the quasi sinusoidal variation of the geomagnetic field intensity since 10 ka for europe punctuated by a peak virtual dipole moment of about 11 1022 a m2 between 8 and 10 ka the data from 10 to 12 ka show considerably lower virtual dipole moments between 4 and 5 1022 a m2 about 60 of the global average since 10 ka when compared with available worldwide data the maximum in the virtual dipole moment between 8 and 10 ka is supported by measurements from japan and possibly hawaii lower than average virtual dipole moments between 10 and 12 ka have also been observed in north america and hawaii the existing data suggest that from 8 to 10 ka the geomagnetic field supported a dipole moment up to 30 above and from 10 to 12 ka about 30 below the average value since 10 ka

longitudinal variability of low latitude total electron content tidal influences 1 recently nighttime ultraviolet uv observations obtained by image fuv and timed guvi instruments have revealed a longitudinal wave number four pattern in the nighttime airglow intensity and in the position of the equatorial anomalies during equinox and high solar flux conditions in the present study we have extended this work and determined the longitudinal variability of the low latitude total electron content tec climatology during different geophysical conditions with a special emphasis on the longitudinal wave number four structure in the low latitude ionosphere we have used more than 5 million low latitude topex tec observations covering the entire 13 years of topex tec data from august 1992 until october 2005 this data set was used to determine the local time seasonal solar cycle and geomagnetic activity dependence of the longitudinal variability of tec at equatorial and low latitudes and in particular to address the existence and evolution of the wave number four longitudinal pattern under these conditions our study shows that the wave number four pattern is created during the daytime hours at equinox and june solstice but is absent or washed out by other processes during december solstice during equinox the wave number four pattern is created around noon with well defined longitudinal enhancements in the low latitude tec these enhancements which are symmetric about the geomagnetic equator during this season last for many hours and can be clearly seen past midnight the longitudinal patterns are found to be nearly identical between the vernal march april and autumnal september october equinoxes and largely independent of the solar cycle conditions the wave number four pattern is also observed during geomagnetically active conditions indicating that the processes that create this pattern are also present during active times the variations between the well defined longitudinal maxima and minima are of the order of 20 during june solstice the wave number four pattern is also observed in the afternoon hours but in contrast to the equinox cases it exhibits a strong hemispheric asymmetry and is not observed during the night the low latitude tec exhibits clear longitudinal variations during december solstice with large daytime enhancements over the east asian and pacific regions and a third enhancement emerging in the afternoon over the atlantic ocean but a clear wave number four pattern is not observed during this season although the equatorial and low latitude tec values exhibit clear longitudinal patterns during all seasons a significant amount of scatter remains in the tec data that is not accounted for by changes in the solar cycle the season or the local time or by the longitudinal variability this remaining scatter is largest near the poleward edges of the anomalies and is of the order of 40

equatorial zonal plasma drifts measured by the c nofs satellite during the 2008 2011 solar minimum 1 we use the measurements by the vector electric field investigation vefi on board the communication navigation outage forecasting system c nofs satellite to study the local time and seasonal and longitudinal dependent climatology of equatorial f region zonal plasma drifts during 2008 2011 these drifts are essentially westward during the day and eastward at night over jicamarca radio observatory the satellite measurements are in good agreement with incoherent scatter radar drifts our data show strong longitudinal variations particularly in the south american sector during the solstices the equinoctial data exhibit short lived and largely enhanced westward drifts near sunrise and wave 4 structures from the early afternoon to late night equinoctial periods the nighttime eastward drifts are largest near the western american sector at all seasons the june solstice postmidnight eastward drifts decrease sharply at longitudes of about 310 and have much smaller values in the entire eastern hemisphere we also briefly discuss the relationship between the longitude dependent vertical and zonal plasma drifts

longitudinal variations in the f region ionosphere and the topside ionosphere plasmasphere observations and model simulations 1 constellation observing system for meteorology ionosphere and climate cosmic observations of the total electron content tec above and below 800 km are used to study the local time and seasonal variation of longitude structures in both the f region ionosphere as well as the topside ionosphere and plasmasphere the cosmic observations reveal the presence of distinct longitude variations in the topside ionosphere plasmasphere tec and these further exhibit a seasonal and local time dependence the predominant feature observed at all local times in the topside ionosphere plasmasphere tec is a substantial maximum minimum during northern hemisphere winter summer around 300 360 geographic longitude around equinox at a fixed local time a wave 4 variation in longitude prevails in the daytime f region tec as well as the topside ionosphere plasmasphere tec the wave 4 variation in longitude persists into the nighttime in the f region however the nighttime topside ionosphere plasmasphere tec exhibits two maxima in longitude the cosmic observations clearly reveal the presence of substantial longitude variations in the f region and topside ionosphere plasmasphere and to elucidate the source of the longitude variations results are presented based on the coupling between the global ionosphere plasmasphere model and the thermosphere ionosphere electrodynamics general circulation model the model simulations demonstrate that the orientation of the geomagnetic field plays a fundamental role in generating significant longitude variations in the topside ionosphere plasmasphere but does not considerably influence longitude variations in the f region ionosphere the model results further confirm that nonmigrating tides are the primary mechanism for generating longitude variations in the f region ionosphere the coupled model additionally demonstrates that nonmigrating tides are also of considerable importance for the generation of longitude variations in the topside ionosphere plasmasphere tec

broad trends in geomagnetic paleointensity on hawaii during holocene time paleointensity determinations have been obtained from 22 basaltic lava flows on the island of hawaii using the thelliers method radiocarbon dating indicates that these flows erupted at intervals ranging from about 200 to 1000 years and results of the experiments provide an estimate of broad trends in geomagnetic paleointensity during holocene time in the vicinity of hawaii most of the samples were obtained from quickly cooled flow margins and as a consequence typically contain two titanomagnetite populations only two of the 79 samples analyzed failed to yield an estimate of the paleofield demonstrating that paleointensities can be obtained from such samples if carefully selected virtual dipole moments calculated for the flows are compared with a published curve of dipole field intensity that was constructed using worldwide archeomagnetic data the large nondipole fields that were previously postulated for the vicinity of hawaii are confirmed and the present data indicate that they were present from about 5000 years b p to perhaps as recently as the past 200 years the data indicate however that these nondipole sources must have been virtually absent between about 12 000 and 5000 years b p as they are at the present time

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

the variability of nonmigrating tides detected from timed saber observations this paper deals with the variability of the nonmigrating tides detected from the observation of the saber instrument on board the timed satellite during the 11 year solar period from 2002 to 2012 the longitudinal wave number spectra with 1 day resolution were first estimated from the temperature data measured at the mlt altitudes 70 110 km and at the lower midlatitudes and low latitudes between 45 then we used the wave number 4 component to obtain the nonmigrating tides in which the dominant component de3 was further analyzed in detail we found that the properties of the spatial distribution and large time scale variation of the de3 component are similar to those of the previous works which used the interpolated data with 2 month resolution these properties are that the de3 component occurs mainly at the low latitudes within 30 and at the altitudes from 90 to 110 km the tidal amplitude is larger during boreal summer and early autumn smaller in spring and almost tends to disappear in winter the component is slightly stronger during the eastward wind qbo phase than the westward phase practically the higher resolution data were used to reveal the day to day variability of the de3 component it is found that 1 the variability occurs mainly at the altitudes from 100 to 110 km with a peak at 106 km 2 it is strong at the low latitudes and peaks around the equator as well slightly stronger in the southern hemisphere than in northern one 3 it is considerably larger around solstitial months than equinoctial months and 4 it would not experience an obvious interannual variation the day to day variability of the de3 component may be explained by the variance of the absolute amplitudes and the contribution of the wave phases and the later seems to play more important role

fluvial sediment transport in response to moderate storm flows following chaparral wildfire ventura county southern california chaparral wildfire has a profound effect on erosion and sedimentation in southern california the wheeler fire in july 1985 burned the entire basin of a tributary drainage area 2 14 km 2 of the north fork of matilija creek near ventura california after the fire fine gravel was delivered to the channel by the process of dry ravel dry particle by particle sliding of debris under the force of gravity at a rate of 0 29 m 3 km 2 month the first winter flow 2 1 m 3 s following the fire deposited 550 m 3 of fine gravel in the 270 m study reach near the mouth of the tributary at least 90 of this fine gravel was derived from colluvium delivered by dry ravel processes from hillslopes near the channel the second winter flow 2 5 m 3 s eroded the channel to the pre fire thalweg a reduction in particle size and critical shear stress associated with deposition of small gravel following the fire allowed these moderate magnitude flows to transport large volumes of sediment deposits of two debris flows were identified in the tributary basin radiocarbon dating of these deposits gives dates of 1045 95 yr b p for the older deposit and between 295 35 and 385 84 yr b p for the younger deposit these dates indicate that the recurrence interval of large debris flows in the study basin is at least an order of magnitude greater than the recurrence interval of fire in the area

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

longitudinal variation of the e region electric fields caused by atmospheric tides 1 polarization electric fields created by the e and f region dynamos cause the uplift of f region plasma the subsequent redistribution of that plasma along the magnetic field lines creates the equatorial ionospheric anomaly eia observations of the post sunset eia made by the image and timed satellites are compared here with champ orsted and sac c observations of the noontime equatorial electrojet eej during magnetically quiet periods around equinox the eia and eej show a remarkably similar four peaked wave like longitudinal variation its structure is consistent with the longitudinal variation in the strength of diurnal tides that drive the e region dynamo this indicates a strong vertical coupling between the ionosphere and troposphere because the four peaked tidal structure is driven by tropospheric weather furthermore the dayside ionospheric conditions are found to perform the global scale longitudinal structure of the post sunset ionosphere at low latitudes

signatures of the 3 day wave in the low latitude and midlatitude ionosphere during the january 2010 ursi world day campaign 1 recent studies of the equatorial ionosphere have found evidence of forcing by atmospheric ultra fast kelvin ufk waves this study investigates the quasi 3 day ufk wave and its effects on the variations of the ionosphere at low latitudes and midlatitudes using coordinated observations of both the atmosphere and ionosphere during the january 2010 ursi world day campaign the global maps of tec from the igs ground based gps product demonstrate a 3 day periodic variation during january 15 25 this variation has the largest amplitude at 15 magnetic latitude and extends into lower latitudes simultaneously a 3 day wave is observed in the mesosphere in the zonal wind measurements by a meteor radar at the magnetic equator the latitudinal range of the tec variation 20 s 20 n is also consistent with that of the 3 day wave the incoherent scatter radar isr observations show a 3 day signature in vertical ion drifts over jicamarca 11 9 s 76 w and in the electron densities in the top side of ionosphere measured from millstone hill 42 6 n 71 5 w this signature is consistent with the fountain effect in the equatorial region and shows the impact on the topside ionosphere at midlatitudes the ufk wave is trapped within 30 geographic latitude but this study shows that the effects of the wave could reach the ionosphere at the higher latitude even as high as 40 n 50 n magnetic latitude

intensity of the earth s magnetic field evidence for a mesozoic dipole low the variation of the strength of the earth s magnetic field throughout geological time is known only poorly large uncertainties spoil indirect paleointensity determinations based on magnetic anomaly amplitude or remanence of sedimentary rocks even when paleointensity data are obtained from direct thermomagnetic studies of magmatic units fundamental problems related to the actual nature of the primary remanence and to the effects of different cooling rates may result in erroneous determinations these uncertainties combined with well known experimental difficulties can explain the large scatter in paleointensity data reported in most previous review papers because experimental difficulties are more rigourously dealt with using the thellier method which also offers some opportunities to minimize some fundamental uncertainties we carried out a compilation of all triassic and younger paleointensity determinations made using this method this selected data set indicates the occurrence of large long term changes of the geomagnetic dipole strength with time the average dipole strength seems to have been approximately constant since late cretaceous time but a dipole strength only one third of the cenozoic value prevailed during most of mesozoic time following a period of larger strength ending possibly during early jurassic times the mesozoic dipole low may be correlated with a cessation of relative motion between the geomagnetic axis and the mantle the terrestrial dynamo seems therefore to exhibit different long term stable states which are probably controlled by the thermal structure in the lowermost mantle

tidal variability in the ionospheric dynamo region 1 the seasonal and interannual variability of migrating sun synchronous and nonmigrating solar atmospheric tides at altitudes between 100 and 116 km are investigated using temperature measurements made with the saber instrument on the timed spacecraft during 2002 2006 quasi biennial variations of order 10 15 in migrating diurnal and semidiurnal tidal amplitudes are found presumably due to modulation by the quasi biennial oscillation qbo as the tides propagate from their troposphere and stratospheric sources to the lower thermosphere a number of nonmigrating tidal components are found that have the potential to produce significant longitudinal variability of the total tidal fields the most prominent of these i e those that appear at amplitudes of order 5 10 k in a 5 year mean climatology include the zonally symmetric s 0 diurnal tide d0 the eastward propagating diurnal and semidiurnal tides with zonal wave numbers s 2 de2 and se2 and s 3 de3 and se3 and the following westward propagating waves diurnal s 2 dw2 semidiurnal s 1 sw1 s 3 sw3 and s 4 sw4 and terdiurnal s 5 tw5 these waves can be plausibly accounted for by nonlinear interaction between migrating tidal components and stationary planetary waves with s 1 or s 2 or by longitudinal variations of tropospheric thermal forcing additional waves that occur during some years or undergo phase cancellation within construction of a 5 year climatology include dw5 se1 se4 sw6 te1 tw1 and tw7 it is anticipated that the winds that accompany all of these waves in the 100 170 km region will impose longitudinal variability in the electric fields produced through the ionospheric dynamo mechanism thereby modulating vertical motion of the equatorial ionosphere and the concomitant plasma densities in addition to the wave 4 modulation of the equatorial ionosphere that has recently been discovered and replicated in modeling studies the waves revealed here will generate wave 1 sw1 sw3 d0 dw2 wave 2 sw4 tw1 wave 3 de2 se1 wave 4 de3 se2 dw5 sw6 te1 tw7 wave 5 se3 and wave 6 se4 components of this ionospheric variability depending on year and time of year however the absolute and relative efficiencies with which these waves produce electric fields remains to be determined

applications in geomorphology abstract geomorphology is a pure science with the goal of understanding earth surface processes and landscape evolution and it is also an applied science with the goal of addressing the needs of society with many new high resolution methods of depicting topography and much improved numerical dating geomorphologists are working on problems involving rates of surface processes landscape evolution and applications to areas of concern to society that were impossible to address a few decades ago some of the areas of enquiry where geomorphology has been applied include natural hazards landslides floods earthquakes and tsunamis ecosystem management site anthropology land use planning engineering geology expert witness testimony and hazard reduction assessment and perception how people perceive and respond to potential hazards how their vulnerability can increase their risk and how preparedness and response can be improved depends as much on the social sciences as on physical science

determination of geomagnetic palaeointensities in vacuum summary specimens with low and intermediate curie points from six hawaiian historic basalt flows were used for the determination of the intensity of the historic geomagnetic field by the thelliers method the specimens were heated either in air or in a vacuum of lo torr the regional intensity of the earth s magnetic field at the time of extrusion of these rocks is known from direct observations the palaeointensities determined in vacuum from four low and intermediate curie point flows are correct within the uncertainty caused by the local field anomalies whereas those determined in air from the same four flows are of lesser quality and accuracy unaltered submarine basalts have similarly low curie points and thus may also be amenable to palaeointensity determination in vacuum the behaviour of the remaining two flows which had higher curie points was more erratic and they yielded less accurate palaeointensities regardless of whether they were determined in air or vacuum the thelliers technique thellier thellier 1959 is one of the most widely used methods for the determination of palaeointensities of the earth s magnetic field from rocks it consists of comparing the thermal spectrum of the natural remanent magnetization nrm of an igneous rock with that of an artifically induced thermoremanent magnetization trm in the same specimen it is assumed that the nrm is a trm acquired during the initial cooling of the rock and that its original thermal spectrum remained unchanged throughout the history of the rock in practice these conditions are not easily met because of two reasons first the nrm acquired by the rock at the time of its formation may be different from that measured in the laboratory because of viscous decay or the superimposition on the nrm of secondary components of magnetization in some cases however this problem may be overcome by thermal cleaning which is an integral part of this technique second when rocks are heated they undergo alterations which affect the chemical composition size and shape of their magnetic mineral grains the effect of these changes may be such that the nrm and trm are produced in two magnetically different materials thus rendering the determination of palaeointensity unreliable because oxidation is the change most likely to occur when heating is carried out in air many authors have recommended the use of high curie temperature rocks which

paleointensity determination magnetic domain structure and selection criteria this special section is focused on the impact of kittel s theory of magnetic domains on rock magnetism and this paper is focused on the implications for paleointensity determinations absolute paleointensity determination is based on specific properties of thermoremanent magnetizations trms mainly the linear dependence of a trm s intensity on the inducing field and the additivity and independence of partial trms these properties are exhibited by populations of noninteracting single domain sd grains but not by populations of multidomain grains the situation is more complex in the pseudo single domain population the most common one in natural rocks usable for paleointensity studies which sometimes exhibit sd like behavior but not always if the experiments were restricted to sd rocks it would not be possible to find enough outcrops to have the spatial and temporal resolution needed for interpretation of the data in terms of geodynamo however as paleointensity determination is very time consuming a preselection of suitable samples is necessary a new procedure will be proposed using a direct test of partial trm s properties with a fully automated experiment fast to implement

strong evidence for the tidal control on the longitudinal structure of the ionospheric f region this paper presents for the first time the global latitude structure and seasonal variability of the ionospheric response to the forced from below de3 and de2 tides during the period of time january 2008 march 2009 the cosmic hmf2 and saber temperature data have been utilized in order to define the ionospheric de3 and de2 tidal response to the de3 and de2 temperature tides propagating from below the cosmic de3 and de2 hmf2 tidal oscillations are derived by the same method as the tides seen the saber temperatures it has been shown that the longitude wave 4 and wave 3 hmf2 structures observed respectively in september and may 2008 are forced mainly by de3 wave 4 and de2 wave 3 temperature tides coming from below the longitude wave 3 hmf2 structure observed in january 2008 however is forced by the combined action of the de2 temperature tide coming from below and the spw3 probably generated in situ

the effects of wildfire on the sediment yield of a coastal california watershed the occurrence of two wildfi res separated by 31 yr in the chaparral dominated arroyo seco watershed 293 km 2 of california provides a unique opportunity to evaluate the effects of wildfi re on suspended sediment yield here we compile discharge and suspended sediment sampling data from before and after the fi res and show that the effects of the postfi re responses differed markedly the 1977 marble cone wildfi re was followed by an exceptionally wet winter which resulted in concentrations and fl uxes of both fi ne and coarse suspended sediment that were 35 times greater than average sediment yield during the 1978 water year was 11 000 t km 2 yr we suggest that the combined 1977 1978 fi re and fl ood had a recurrence interval of greater than 1000 yr in contrast the 2008 basin complex wildfi re was followed by a drier than normal year and although suspended sediment fl uxes and concentrations were signifi cantly elevated compared to those expected for unburned conditions the sediment yield during the 2009 water year was less than 1 of the post marble cone wildfi re yield after the fi rst postfi re winters sediment concentrations and yield decreased with time toward prefi re relationships and continued to have signifi cant rainfall dependence we hypothesize that the differences in sediment yield were related to precipitationenhanced hillslope erosion processes such as rilling and mass movements the millennialscale effects of wildfi re on sediment yield were explored further using monte carlo simulations and these analyses suggest that infrequent wildfi res followed by flincrease long term suspended sediment fl markedly thus we suggest that the current approach of estimating sediment yield from sediment rating curves and discharge data without including periodic perturbations from wildfi res may grossly underestimate actual sediment yields

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

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

effect of storms during drought on post wildfire recovery of channel sediment dynamics and habitat in the southern california chaparral usa author s florsheim joan l chin anne kinoshita alicia m nourbakhshbeidokhti samira abstract current global warming projections suggest a possible increase in wildfire and drought augmenting the need to understand how drought following wildfire affects the recovery of stream channels in relation to sediment dynamics we investigated post wildfire geomorphic responses caused by storms during a prolonged drought following the 2013 springs fire in southern california usa using multi temporal terrestrial laser scanning and detailed field measurements after the fire a dry season dry ravel sediment pulse contributed sand and small gravel to hillslope channel margins in big sycamore creek and its tributaries a small storm in wy 2014 generated sufficient flow to mobilize a portion of the sediment derived from the dry ravel pulse and deposited the fine sediment in the channel totaling 0 60 m3 m of volume per unit length of channel the sediment deposit buried step pool habitat structure and reduced roughness by over 90 these changes altered sediment transport characteristics of the bed material present before and after the storm the ratio of available to critical shear stress t o t c increased by five times storms during wy 2015 contributed additional fine sediment from tributaries and lower hillslopes and hyperconcentrated flow transported and deposited additional sediment in the channel together these sources delivered sediment on the order of six times that in 2014 further increasing t o t c these storms during multi year drought following wildfire transformed channel dynamics the increased sediment transport capacity persisted during the drought period characterized by the longer residence time of relatively fine grained post fire channel sedimentation this contrasts with wetter years when post fire sediment is transported from the fluvial system during the same season as the post fire sediment pulse results of this short term study highlight the complex and substantial effects of multi year drought on geomorphic responses following wildfire these responses influence pool habitat that is critical to longer term post wildfire riparian ecosystem recovery

sediment yield from the tectonically active semiarid western transverse ranges of california sediment yields from the world s rivers are generally highest from steep drainage basins with weak lithology active tectonics or severe land use impacts here we evaluate sediment yields from the western transverse ranges of california in an attempt to explain why they are two to tenfold greater than the surrounding areas of california we found that suspended sediment yields across the gauged basins of the western transverse range during 1969 1999 varied by approximately an order of magnitude 740 5300 t km2 yr similarly fine sediment concentrations for normalized discharge rates varied by almost two orders of magnitude e g 1 3 110 g l for the mean annual flood for 11 previously unmonitored drainages of the santa ynez mountains areas with high sediment yields consistently have weakly consolidated bedrock quaternary pliocene marine formations and are associated with the highest rates of tectonic uplift of the region 5 mm yr these regions are important to the sediment discharge budgets because 50 of the total suspended sediment discharge from the western transverse range is estimated to be generated within these regions even though they represent only 10 of the total watershed area previous estimates of suspended sediment discharge from the ventura river have likely been underestimated by 50 because the gauging station is located immediately upstream of a high sediment yield region we also found a significant and positive correlation between sediment yield and the percentage of a watershed with grassland and agricultural land use these results suggest that there is adequate variation within the lithology tectonics and land use of the broader western transverse range geologic province to induce large variations in sediment yield at the local scale

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

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

large scale waves in the mesosphere and lower thermosphere observed by saber observations made by the sounding of the atmosphere using broadband emission radiometry saber instrument on board nasa s thermosphere ionosphere mesosphere energetics and dynamics timed satellite have been processed using salby s fast fourier synoptic mapping ffsm algorithm the mapped data provide a first synoptic look at the mean structure and traveling waves of the mesosphere and lower thermosphere mlt since the launch of the timed satellite in december 2001 the results show the presence of various wave modes in the mlt which reach largest amplitude above the mesopause and include kelvin and rossby gravity waves eastward propagating diurnal oscillations non sunsynchronous tides and a set of quasi normal modes associated with the so called 2 day wave the latter exhibits marked seasonal variability attaining large amplitudes during the solstices and all but disappearing at the equinoxes saber data also show a strong quasi stationary rossby wave signal throughout the middle atmosphere of the winter hemisphere the signal extends into the tropics and even into the summer hemisphere in the mlt suggesting ducting by westerly background zonal winds at certain times of the year the 5 day rossby normal mode and the 4 day wave associated with instability of the polar night jet are also prominent in saber data

longitudinal variations in the equatorial vertical drift in the topside ionosphere 1 the vertical ion drift is important for understanding and modeling the electrodynamics at low latitudes measurements from the ion drift meter on the defense meteorological satellite program dmsp f15 are used to examine longitudinal variations in the vertical ion drift at the dip equator in the topside ionosphere local time was restricted to 0930 and the data were organized by month for 2001 and 2002 two features were found contributing to the longitudinal variations in the electrodynamics meridional winds contribute to the equatorial vertical ion drift at the 830 km magnetic apex due to their dynamo action at the foot points of the magnetic field lines in the f region at magnetic latitudes near 15 electric fields producing a downward perturbation drift at 0930 are produced by hemispheric differences in the dynamo current due primarily to the different orientation of the magnetic meridian relative to the terminator this produces the seasonally dependent variation as a function of longitude that is observed a wavenumber 4 longitudinal variation also appears to be present throughout the year but is more influential during equinox conditions this variation also shows a seasonal cycle shifting east during northern summer and west during northern winter further analysis would be required to isolate the characteristics of a wavenumber 4 driver from the wavenumber 4 component of the fourier series used here to fit the data

paleointensity of the earth s magnetic field recorded by two late quaternary volcanic sequences at the island of la reunion indian ocean a paleomagnetic study has been undertaken on two late quaternary volcanic sequences from the piton de la fournaise volcano island of la reunion in order to provide absolute paleointensities of the earth s magnetic field from a site in the southern hemisphere the pattern of secular variation recorded by both sequences clearly indicates that the extrusion rate of the lava flows was not constant with time a detailed investigation of the magnetic properties of the samples was carried out in parallel with paleointensity experiments which were performed with the thellier method samples with minimum overprint composed by single domain or pseudo single domain magnetite showing good thermal stability and a narrow blocking temperature spectrum were the most successful during thellier s experiments values of the paleofield strength from 19 to 55 mt have been obtained on 23 flows among the 30 which were sampled few variations 7 5 9 9 1022 a m2 are observed in the virtual dipole moments vdms determined on the youngest sequence 5 12 ka those values are within the range of fluctuations of the worldwide variations of vdms for this period on the other hand data from the oldest sequence 82 98 ka are the first paleointensity values obtained in that time period and the observed vdms extend from 4 1 to 8 8 1022 a m2 these results suggest that for this time interval the field did not depart from its average behavior

absolute paleointensity and magnetomineralogical changes determinations of absolute paleointensity are often hampered by magnetomineralogical changes produced within samples of lava flows during successive heatings such changes which directly affect the capacity for a sample to acquire a partial thermoremanent magnetization ptrm are reflected by negative ptrm checks a deviation between the original ptrm and a repeated measurement after heating at a higher temperature because the deviations indicated by the ptrm checks can provide a direct estimate of the effects to the ptrms we suggest that they can be used to correct ptrms the correction method we present requires additional measurements in particular ptrm checks performed after each ptrm and specific diagrams to detect acquisition of chemical remanence performing multiple successive ptrm checks can also provide information on the blocking temperatures of the alteration product these experiments conducted on lava flows from different localities show that the magnetomineralogical changes mainly involved grains with blocking temperatures lower than the last heating step the corrections have been tested on recent and historic lava flows from several localities we have also compared results on samples from the same lava flows that were heated in air and in vacuum the mean paleointensity values were found to lie within less than 10 from the expected field intensity at each site the corrections resulted in the recovery of reliable paleointensity determinations for about twice as many specimens heated in vacuum and 65 additional data for specimens heated in air successive heatings at the same temperature in air are often accompanied by a time dependent oxidation of the natural remanent magnetization which is responsible for paleointensity values lower than the expected field a problem that is not related to the corrections we conclude that corrections can be used with fairly high confidence to the ptrms performed in vacuum and in air

longitudinal variation in global navigation satellite systems tec and topside ion density over south american sector associated with the four peaked wave structures 1 recent observations of the low latitude ionospheric electron density revealed a four peaked longitudinal structure in the equatorial ionization anomaly when plotted at a constant local time frame it was proposed that neutral wind driven e region dynamo electric fields due to nonmigrating tidal modes are responsible for this pattern we examine the four peaked structure in the observed topside ion density and its manifestation as longitudinal structures in total electron content tec over south america the strong longitudinal variation in tec characterized by larger value over brazilian eastern longitude sector as compared to that over the peruvian western longitude is modeled using the sheffield university plasmasphere ionosphere model supim aiming to identify the control factors responsible for the longitude variation we found that the supim runs using as input the existing standard models of vertical drift and thermospheric winds do not explain the tec longitudinal structure realistic values of these control parameters were generated based on the strong vertical drift longitudinal variation as determined from magnetometer and digisonde data and appropriately adjusted winds horizontal wind model these realistic vertical drifts together with the modified thermospheric wind when used as input to the supim are found to satisfactorily explain the longitudinal differences in the tec and topside ion density ni over south america the study shows that the tec in the whole latitude distribution is larger over the east coast than over the west coast of south america and that the vertical drift and thermospheirc winds control the longitudinal four wave structure in the tec and ni

troposphere thermosphere tidal coupling as measured by the saber instrument on timed during july september 2002 1 coupling between the troposphere and lower thermosphere due to upward propagating tides is investigated using temperatures measured from the saber instrument on the timed satellite the data analyzed here are confined to 20 120 km altitude and 40 latitude during 20 july to 20 september 2002 apart from the migrating sun synchronous tidal components the predominant feature seen from the satellite frame during this period is a wave 4 structure in longitude with extrema of up to 40 50 k at 110 km amplitudes and longitudes of maxima of this structure evolve as the satellite precesses in local time and as the wave s responsible for this structure vary with time the primary wave responsible for the wave 4 pattern is the eastward propagating diurnal tide with zonal wave number s 3 de3 its average amplitude distribution over the interval is quasi symmetric about the equator similar to that of a kelvin wave with maximum of about 20 k at 5 s and 110 km de3 is primarily excited by latent heating due to deep tropical convection in the troposphere it is demonstrated that existence of de3 is intimately connected with the predominant wave 4 longitude distribution of topography and land sea difference at low latitudes and an analogy is drawn with the strong presence of de1 in mars atmosphere the predominant wave 2 topography on mars and the wave 2 patterns that dominate density measurements from the mars global surveyor mgs spacecraft near 130 km additional diurnal semidiurnal and terdiurnal nonmigrating tides are also revealed in the present study these tidal components are most likely excited by nonlinear interactions between their migrating counterparts and the stationary planetary wave with s 1 known to exist in the southern hemisphere during this period just prior to the austral midwinter stratospheric warming of 2002

archaeomagnetic paleointensity in the american southwest during the past 2000 years abstract an archaeomagnetic paleointensity study was carried out on pottery samples from the hohokam anasazi and mogollon cultures of the american southwest the thellier thellier paleointensity experiment was used on 187 specimens from 77 different sherds derived from 23 archaeological sites interpretations were made for 127 specimens from 54 sherds about a two thirds success rate the median value for the quality factor was 12 the results were corrected for magnetic anisotropy owing to a fabric in the pottery using an easy plane model of magnetization the anisotropy of the hard axis relative to the easy plane of magnetization averaged 31 the correction factor for the paleointensity was typically 5 4 and systematically increased the paleointensities because the laboratory heatings were applied within the easy plane the sample average paleointensities were compiled along with other data from north america the hohokam data were kept as a separate set because of uncertainties concerning the hohokam chronology curves of the virtual axial dipole moment vadm variation for the hohokam and non hohokam data sets were derived using a moving window smoothing technique the hohokam and non hohokam curves show good agreement regardless of which hohokam chronology is used relative paleointensity records from north american lake sediments are also congruent with the archaeointensity results despite the scatter in the archaeomagnetic data the correlation of these records suggests that the secular variation pattern is being recovered the field strength at 300 bc is 30 40 higher than at present a low from 250 to 1250 ad is 10 15 weaker than at present and a peak at 1500 ad is about 30 higher than at present the low from 250 to 1250 ad in comparison with global paleointensity compilations suggests a substantial non dipole field in north america at that time the rate of change of the archaeomagnetic vadm is similar to rates observed today

equatorial longitude and local time variations of topside magnetic field aligned ion drifts at solar minimum 1 in the topside ionosphere the high mobility of the plasma along the magnetic field allows field aligned ion drifts to occur readily as a result of field aligned gravitational forces collisional forces or pressure gradients therefore variations in the field aligned ion drifts can be used to explore the influence of thermospheric electrodynamic and chemical processes on the ionosphere longitude and local time variations in the field aligned ion drifts near the magnetic equator are presented using observations from the coupled ion neutral dynamics investigation on board the communications navigation outage forecast system satellite these observations were obtained during the period of extremely low solar activity present in 2008 and 2009 allowing the seasonal local time and longitudinal variations to reveal the relative importance of the processes responsible for topside field aligned plasma drifts during solar minimum this investigation found that the low altitude winds and tides the net ionization or loss and the meridional e b drift were all influential in creating longitudinal and local time variations in the field aligned drift though the strength of the influence seen by each driver was found to vary with season local time and longitude

short term post wildfire dry ravel processes in a chaparral fluvial system abstract dry ravel the transport of sediment by gravity transfers material from steep hillslopes to valley bottoms during dry conditions following wildfire dry ravel greatly increases in the absence of vegetation on hillslopes thereby contributing to sediment supply at the landscape scale dry ravel has been documented as a dominant hillslope erosion mechanism following wildfire in chaparral environments in southern california however alteration after initial deposition is not well understood making prediction of post fire flood hazards challenging the majority of big sycamore canyon burned during the may 2013 springs fire leaving ash and a charred layer that covered hillslopes and ephemeral channels dry ravel processes following the fire produced numerous deposits in the hillslope channel transition zone field data focus on 1 deposition from an initial post wildfire dry ravel pulse and 2 subsequent alteration of dry ravel deposits over a seven month period between september 2013 and april 2014 we quantify geomorphic responses in dry ravel deposits including responses during the one small winter storm that generated runoff following the fire field measurements document volumetric changes after initial post wildfire deposition of sediment derived from dry ravel erosion and deposition mechanisms that occurred within dry ravel deposits situated in the hillslope channel transition zone included 1 mobilization and transport of a portion or the entire deposit by fluvial erosion 2 rilling on the surface of the unconsolidated deposits 3 deposition on deposits via continued hillslope sediment supply and 4 mass wasting that transfers sediment within deposits where surface profiles are near the angle of repose terrestrial lidar scanning point clouds were analyzed to generate profiles quantifying depth of sediment erosion or deposition over remaining dry ravel deposits after the first storm season this study contributes to the understanding of potential effects of wildfire on fine sediment delivery to fluvial systems in chaparral ecosystems

local time seasonal and solar cycle dependency of longitudinal variations of tec along the crest of eia over india 1 the global wave number 4 structure in the indian longitudinal region spanning from 70 to 95 e forming the upward slope of the peak in the total electron content tec are reported along the crest of equatorial ionization anomaly eia the continuous and simultaneous measurements from five gps stations of gps aided geo augmented navigation gagan network are used in this study the long term database 2004 2012 is utilized for examining the local time seasonal and solar cycle dependency on the longitudinal variations of tec our results confirm the existence of longitudinal variations of tec in accordance with wave number 4 longitudinal structure including its strength the results suggest that these variations in general start to develop at 09 lt achieve maximum strength at 12 15 lt and decay thereafter the decay rate depending on the season they are more pronounced in equinoctial season followed by summer and winter the longitudinal variations persist beyond midnight in equinox seasons whereas in winter they are conspicuously absent interestingly they also exhibit significant solar cycle dependence in the solstices whereas in the equinoxes they are independent of solar activity the comparison of crest to trough ratio ctr in the eastern 92 e and western 72 e extreme longitudes reveals higher ctr on the eastern side than over the western extreme suggesting the role of nonmigrating tides in modulating the exb vertical drift and the consequential eia crest formation

monthly tidal temperatures 20 120 km from timed saber 1 the saber instrument on the timed satellite provides unprecedented geographical coverage for the determination and study of atmospheric tides however the slow local time precession rate of timed can cause longer term temperature variations to alias into the tidal signals a new method of analyzing satellite data for tides has been developed to circumvent this difficulty but at the expense of temporal resolution of the tidal fields i e 120 day mean tidal structures are obtained in this work we apply this method to saber temperature data to derive a series of 120 day mean tidal structures extending between 20 and 120 km altitude 50 s 50 n latitude and centered on each month from september 2003 to september 2004 in addition to the migrating sun synchronous diurnal and semidiurnal tides a number of nonmigrating tides are revealed in the saber measurements some of these waves are thought to originate via nonlinear coupling between the migrating tides and the stationary planetary wave with zonal wave number s 1 other nonmigrating tidal components appear to be forced by latent heating due to deep tropical convection of the latter the eastward propagating diurnal tide with s 3 is dominant and is as large as the migrating diurnal tide during some months of particular interest is the wave 4 structure with respect to longitude that characterizes both the diurnal and semidiurnal total tidal fields this feature is a result of the predominant wave 4 topography land sea longitude dependence at the surface which is reflected in the diurnal and semidiurnal components of the latent heating rates due to deep tropical convection the ability of the global scale wave model gswm to approximate the observed tidal fields including the wave 4 total tidal structures is also assessed

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

the source of the longitudinal asymmetry in the ionospheric tidal structure 1 we examine the source of the longitudinal asymmetry in the ionospheric tidal structure by using the measurements of the plasma density and vertical plasma drift by the first republic of china satellite the consistent feature in plasma density and vertical plasma drift in all months is the development of the wave crests near 0 10 e and 90 100 e longitude the appearance of the global wave 4 or wave 3 structure is determined by the morphology between 150 e and 300 e longitude two crests are pronounced in july september and only one crest appears during the december solstice in that longitude region the crests of the wave 4 structure between 150 e and 300 e longitude are much weaker than the crests near the longitudes of 0 and 90 e during july september the wave 3 structure is pronounced in all months the phase difference between the wave 3 and wave 4 structures is small near the longitudes of 0 and 90 e and thus the superposition of the wave 3 structure amplifies the wave 4 crest intensity in those regions the phase difference is large between 150 e and 300 e longitude and thus the destructive superposition of the wave 3 component weakens the wave 4 crest in that region the wave 3 and wave 4 structures are the permanent ionospheric features and the significant portion of the longitudinal asymmetry is explained by the phase difference of the two structures

paleointensity of the earth s magnetic field in the jurassic new results from a thellier study of the lesotho basalt southern africa thellier paleointensity experiments carried out on the jurassic 180 m y old karoo basalt lesotho southern africa provided paleointensity estimates for 40 samples from 10 distinct lava flows with reversed magnetization mean paleointensity was found to be equal to 24 2 11 3 t standard deviation with a minimum of 12 t and a maximum of 41 3 t this corresponds to a mean virtual dipole moment vdm of 4 6 2 0 1022 am2 the between flow dispersion is ascribed to paleosecular variation which thus would approach up to 40 of the mean paleointensity as is observed from the published paleointensity data set covering last 20 m y this result yields further evidence for the period of low geomagnetic field in jurassic to early cretaceous time mesozoic dipole low a symmetrical intensity versus time pattern is suggested for this time interval with a minimum vdm of 3 1022 am2 in late jurassic and substantially higher 4 5 1022 am2 vdms in early to middle jurassic and early cretaceous respectively

post fire bedload sediment delivery across spatial scales in the interior western united states post fire sediment yields can be up to three orders of magnitude greater than sediment yields in unburned forests much of the research on post fire erosion rates has been at small scales 100 m2 or less and post fire sediment delivery rates across spatial scales have not been quantified in detail we developed relationships for post fire bedload sediment delivery rates for spatial scales up to 117 ha using sediment yield data from six published studies and two recently established study sites sediment yields and sediment delivery ratios sdrs sediment delivered at the catchment scale divided by the sediment delivered from a plot nested within the catchment were related to site factors including rainfall characteristics area length and ground cover unit area sediment yields significantly decreased with increasing area in five of the six sites the annual sdrs ranged from 0 0089 to 1 15 and these were more closely related to the ratio of the plot lengths than the ratio of plot areas the developed statistical relationships will help quantify post fire sediment delivery rates across spatial scales in the interior western united states and develop process based scaling relationships published in 2013 this article is a u s government work and is in the public domain in the usa

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

sediment yield from disturbed earth systems changes of sediment yield rates through time reflect evolutionary changes within a landscape when a drainage basin is perturbed significantly by base level climatic or tectonic change sediment yields increase dramatically but with no further disturbance they decline rapidly these sediment yield changes have been documented at all scales from small experimental studies to incised channels to the colorado river basin and to the himalaya mountains thus the shape of the sediment yield curve can be used to estimate future sediment yields and to interpret past tectonic events

fluvial geomorphology of a boulder bed debris flow dominated channel in an active tectonic environment abstract numerous streams with a drainage area of a few square kilometers draining the south flank of the santa ynez range in southern california are characterized by steep boulder bed debris flow dominated channels rattlesnake creek is a good example approximately 90 of the stored sediment in the stream valley is stable debris flow deposits found in debris flow terraces and levees adjacent to the channel the remaining 10 of stored sediment resides in the active channel where the channel morphology is dominated by large boulders 1 to 4 m in diameter derived from debris flows or rock fall that along with bedrock outcrops form rock or boulder transverse ribs with frequent step pools the dominant channel pool morphology is the step pool which accounts for most of the pools and approximately 30 of relief drop in elevation through the study reaches less common pool types identified in the study reaches include forced pools that result from convergence of flow with scour between lbres large boulder roughness elements and bedrock outcrop along the channel at near bankfull discharge the lbres and boulders in step pools armor the channel and are primary controls on channel morphology and gradient rock strength is a secondary control on channel morphology location and abundance of pools we hypothesize that step pools when inundated with sand and fine gravel from a disturbance such as wildfire during a flow event fill near bankfull stage and scour on falling stage below bankfull when unit stream power is a maximum over the step thus as with forced pools step pool maintenance depends on a specific pattern of discharge and process the process of scour during falling stage reestablishes step pools during moderate flows following disturbance

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

geomagnetic paleointensities from excursion sequences in lavas on oahu hawaii paleomagnetic data demonstrating three late tertiary excursions in the direction of the geomagnetic field recorded in sequences of basaltic lavas on the island of oahu hawaii were published by r r doell and g b dalrymple in 1973 we have determined geomagnetic paleointensities by the thelliers method for 14 lavas from the three sites during these experiments considerable difficulty was encountered because of the presence of titanomaghemite in many lavas and the contamination of natural remanent magnetization by lightning in many others moreover we often observed the production of spurious high temperature chemical remanent magnetization during the thellier experiments an analysis of this particularly troublesome problem is presented two of the sites showed low paleointensities associated with angular departures of the paleomagnetic field direction from that of a geocentric axial dipole which suggests that these excursions represent aborted reversals or fragments of reversals at the third site however the paleointensity did not become low as the field diverged this excursion may reflect the variation of a large nondipole source near hawaii

the comparative importance of de3 se2 and spw4 on the generation of wavenumber 4 longitude structures in the low latitude ionosphere during september equinox 1 numerical simulations are performed to investigate the generation of the wave 4 longitude variation in the low latitude ionosphere due to the diurnal eastward propagating nonmigrating tide with zonal wavenumber 3 de3 semidiurnal eastward propagating nonmigrating tide with zonal wavenumber 2 se2 and stationary planetary wave 4 spw4 from a fixed local time perspective the de3 se2 and spw4 all appear as wave 4 structures in longitude and thus each of these waves must be considered as a potential source of the wave 4 variation in the ionosphere both thede3 and spw4 are found to produce significant wave 4 variations in the equatorial verticale bdrift velocity and in the ionospheric peak density nmf2 at 15 n magnetic latitude the daytime wave 4 variation in nmf2 is driven by the combination of verticale bdrift variability and in situ effects due largely to meridional neutral winds the simulation results indicate that these2 is not a contributor to the wave 4 longitude variation our results further demonstrate that the actual wave 4 longitude variation is due to a combination of thede3 and spw4 we therefore conclude that in addition to the de3 the spw4 also needs to be considered as an important driver of the wave 4 longitude variation in the low latitude ionosphere we additionally present evidence for the generation of thespw4 due to the nonlinear interaction between the migrating diurnal tide and the de3 and demonstrate the impact of de3 variability on the amplitude of the spw4

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

resolving daily wave 4 nonmigrating tidal winds at equatorial and midlatitudes with windii de3 and se2 the wind imaging interferometer observed nonmigrating tidal winds from 90 to 260 km during daytime and at 99 and 250 km during the night and found that the amplitudes and phases of the daytime and nighttime extracted wave 4 for a given day were different indicating the presence of more than one component the objective of this study is to resolve those components local time versus longitude propagation plots over individual seasons revealed the diurnal eastward propagating wave number 3 de3 the semidiurnal eastward propagating wave number 2 se2 and the stationary planetary wave number 4 spw4 using a fitting procedure for individual days it was then found possible to determine the amplitudes and phases of de3 and se2 and the amplitude of spw4 for each day using a constant phase for the spw4 obtained from the propagation plot these de3 and se2 values were compared with data constrained model results yielding good agreement at 99 km but with mixed agreement at 250 km time series analysis of 164 days duration showed considerable variability in the amplitudes of the zonal wind for de3 with the spw4 tending to follow de3 power spectral peaks occurred near 12 16 and 32 days the se2 showed less variability also displaying spectral peaks but shifted from the de3 peaks monthly averages of the de3 and se2 show that the de3 is predominant at the equatorial mesosphere lower thermosphere region on the other hand the se2 is uniformly present at lower and midlatitudes and all altitudes

daytime ionospheric longitudinal gradients seen in the observations from a regional beidou geo receiver network many studies have devoted to the longitudinal variations of the ionosphere globally however the ionospheric longitudinal variations in a small region are rarely reported in this paper we for the first time use tec data from a beidou geostationary orbit geo receiver network to observe and investigate ionospheric longitudinal variations within the zonal scale of 1000 km over central china 112 122 e 27 31 n 20 24 n magnetic latitudes during june 2015 december 2016 the beidou geo tec provides a good dataset to study longitudinal variations compared with non geo tec without contaminating the spatial variations and elevation changes due to satellite motion pronounced daytime longitudinal gradients within the distance of 1000 km are present in beidou geo tec it was found that the tec is generally larger in the west than in the east in some cases the tec gradient magnitude is larger than 45 tecu for most events the obvious daytime longitudinal gradients are accompanied by the tec enhancement the occurrence rate of daytime longitudinal gradients under different geomagnetic activities is similar whereas strong daytime longitudinal gradients mainly occur under the moderate and strong disturbance geomagnetic activities these observations suggest that the electric field disturbances could have significant effects on producing the observed ionospheric longitudinal gradients

the variability of se2 tide extracted from timed saber observations based on the temperature observations of the timed saber in mlt region 70 110 km altitudes and at the low and mid latitudes 45 s 45 n from 2002 to 2012 the variability of the non migrating tide se2 with one day resolution is analyzed using the method from li et al 2015 it is found that the climatological features large scale variability of the se2 tide are similar with the results from the previous researches the se2 tide manifests mainly at the low mid latitudes around 30 the northern hemisphere tidal amplitudes below 110 km are larger than the southern hemisphere tide at the same time its peaks below 110 km mainly present between 100 and 110 km altitude the tidal amplitudes below 110 km occur a north south asymmetry about the equator in the annual variation in the southern hemisphere se2 occurs with an obvious annual variation with a maximum of tidal amplitudes in december while in the northern one the semi annual variations with maximum at the equinoxes herein owing to the high resolution tidal data we could research the short term day to day variations of se2 we found that the day to day variations manifests mainly at between 100 and 110 km altitudes it increases gradually with latitudes and it is stronger at the low mid latitudes it is relatively slightly stronger around solstices than equinoxes it does not present a remarkably inter annual variation the se2 day to day variations may be composed by the absolute amplitudes variance and the impact of the wave phases and the latter ones are more important

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

fire floods and woody debris interactions between biotic and geomorphic processes fire and floods interact in the riparian zone as processes that structure plant communities and landforms although much of the immediate impact of fire is on the vegetation fire related changes in runoff sediment supply riparian vegetation and woody debris volume have ongoing geomorphic impacts on the valley floor consequent hydrogeomorphic changes in turn affect the composition and distribution of vegetation this paper reviews these interactions and provides an example of how fires and floods intersect to supply burnt trees as woody debris because the temporal and spatial distribution of woody debris is initially controlled by patterns of tree mortality ecological disturbances like fire can be an important source for pulses of woody debris in riparian systems to understand these interactions we examine woody debris inputs 3 years after a wildfire in the riparian gallery forests of the western transverse ranges california within our sample of 339 burned stems snags fell in distinctive patterns species were variable in susceptibility to falling and fell at greater rates at sites with greater subsequent flooding discordance between the species composition of fallen snags and that of overall burned stems indicates that variability in forest composition must be considered in predicting post disturbance inputs of woody debris variation in snagfall timing among species suggests that woody debris inputs are likely to occur in multiple sequential pulses after wildfire the role of flooding is superimposed on this ecological influence as the timing and spatial variability of floods affect the recruitment of woody debris from the supply of snags created by fire

longitudinal structure of the equatorial anomaly in the nighttime ionosphere observed by image fuv 1 the far ultraviolet imager fuv on board the image satellite provides an instantaneous global view of the oi 135 6 nm nightglow with 2 min time resolution because the oi 135 6 nm emission from the nighttime ionosphere is determined by the line of sight integrated plasma density the nightglow images are useful for studying the nighttime low latitude ionosphere globally with the image fuv 135 6 nm observations from march to june 2002 we have examined the global characteristics of the nighttime equatorial anomaly ea by constructing a constant local time map lt map in which pixels within an assigned local time range are extracted from the image fuv nightglow images obtained over an observation period of 3 days or more and are put together to compose a global distribution map of emission intensities at that local time these lt maps show that the development of the ea has a significant longitudinal structure in which peaks and dips of the crest emission intensity and the crest latitude have about 90 longitudinal separation in the longitude range from 0 to 250 although there is not enough data over the american sector this result suggests that the ea longitudinal structure has a prominent zonal component of the wave number 4 the observed longitudinal structure of the nighttime ea could not be fully explained by factors such as the empirical electric field and neutral wind models the geomagnetic declination angle or the displacement of the geomagnetic equator from the geographic equator to explain the observed longitudinal structure of the ea in particular the wave number 4 feature we may need to consider other forcing for example nonmigrating tide originated from the lower atmosphere

climatology of f region zonal plasma drifts over jicamarca 1 we use extensive incoherent scatter radar observations made at the jicamarca radio observatory between 1970 and 2003 to study and model empirically the equatorial zonal plasma drifts near the f region peak using bernstein polynomials as base functions our quiet time model results confirm that the daytime drifts are westward and are nearly season and solar cycle independent the nighttime drifts are eastward have larger magnitudes and increase strongly with solar flux particularly near equinox and december solstice enhanced geomagnetic activity drives small eastward perturbation drifts during the day and much larger westward disturbance drifts at night the nighttime drift perturbations are largest near midnight and increase strongly with solar flux near equinox and december solstice but are essentially absent near june solstice the jicamarca zonal disturbance drifts can be largely accounted for by disturbance dynamo electric fields with a dominant time delay of about 3 15 hours following enhanced geomagnetic activity in the postmidnight sector there are also smaller westward disturbance drifts associated with time delays of about 15 24 hours and perhaps even longer our results strongly suggest that the longitudinal dependence of both the quiet and disturbed equatorial nighttime zonal drifts varies with season

empirical model of the thermospheric mass density based on champ satellite observations 1 the decadal observations from champ satellite have provided ample information on the earth s upper thermosphere reshaping our understandings of the vertical coupling in the atmosphere and near earth space an empirical model of the thermospheric mass density is constructed from these high resolution observations using the multivariable least squares fitting method it describes the density variation with latitude longitude height local time season and solar and geomagnetic activity levels within the altitude range of 350 420 km it represents well prominent thermosphere structures like the equatorial mass density anomaly ema and the wave 4 longitudinal pattern furthermore the empirical model reveals two distinct features first the ema is found to have a clear altitude dependence with its crests moving equatorward with increasing altitude second the equinoctial asymmetry is found to strongly depend on solar cycle with its magnitude and phase being strongly regulated by solar activity levels the equinoctial density maxima occur significantly after the actual equinox dates toward solar minimum which may signal growing influence from the lower atmosphere forcing this empirical model provides an instructive tool in exploring thermospheric density structures and dynamics it can also be easily incorporated into other models to have a more accurate description of the background thermosphere for both scientific and practical purposes

global structure and seasonal and interannual variability of the migrating diurnal tide seen in the saber timed temperatures between 20 and 120 km 1 the present paper is focused on the global spatial altitude and latitude structure and seasonal and interannual variability of the migrating diurnal tide derived from the sounding of the atmosphere using broadband emission radiometry thermosphere ionosphere mesosphere energetics and dynamics saber timed temperature measurements for 6 full years january 2002 to december 2007 the tidal results are obtained by a new analysis method where the tides migrating and nonmigrating and the planetary waves zonally traveling and stationary are simultaneously extracted from the satellite data it has been found that above 70 km height the saber migrating diurnal tide reflects mainly the distinctive features of the first symmetric propagating 1 1 mode while below this height it reflects the features of the first symmetric trapped 1 2 mode the trapped component amplifies near 50 km and its phase is close to 1600 lt the seasonal behavior of the diurnal tide over the equator is dominated by semiannual variation with a primary maximum in february march 18 k average amplitude for 6 years and a secondary maximum in august september 15 k the tidal amplitude grows rapidly in the mesosphere lower thermosphere however it undergoes some decay near 90 km defining ubiquitous double peaked vertical structure a very rapid reduction in amplitude is detected at heights near 115 km however above this level the diurnal tide amplifies again the vertical wavelength of the propagating diurnal tide is 20 km over the equator at middle latitudes it is not very different from that over the equator but its magnitude depends on the season in the winter it is longer than that in summer the interannual variability of the diurnal tide indicates a clear correlation with the stratospheric quasi biennial oscillation

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

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

an empirical model of the occurrence of an additional layer in the ionosphere from the occultation technique preliminary results about 8 year electron density profile edp data from the cosmic formosat 3 satellites radio occultation technique were used to investigate the additional stratification of the f2 the so called f3 layer layer over the equatorial and low latitude ionosphere on a global scale for both the bottomside and topside ionosphere the f3 layer was recognized through the altitude differential profile featured by two maxima existing from the selected edp profile there were 37 000 bottomside and 25 000 topside cases of f3 layer selected out of 1 27 million occultation events at equatorial and low latitude areas during the period of april 2006 to august 2014 the statistical results for the bottomside ionosphere resemble that reported in zhao et al 2011a while in the topside the highest occurrence of f3 layer shows a 3 4 h delay depending on the altitude range of the stratification the magnetic latitude distribution shows different dependence with a tendency to form a single crest toward high altitude also the seasonal variation is weaker in the topside ionosphere compared to the bottomside one especially in the high altitude then we build up an empirical model of the f3 layer occurrence using the bottomside statistics based on empirical orthogonal function eof decomposition as it gets the inherent characters inside the data set and converges quickly the model well grasps the main features of the f3 occurrence e g the f3 occurrence s sensitivity on the magnetic latitude further in order to accommodate the ground observation a corrected factor was introduced as f3 layer is an important phenomenon in the low latitude ionosphere we have made an attempt to describe its feature with a consecutive function although future work needs to be done for an overall expression of this structure

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

correlation between the ionospheric wn4 signature and the upper atmospheric de3 tide 1 the present work studies the correlation relationship between the longitudinal ionospheric structure of wave number 4 wn4 and the upper atmospheric tide of nonmigrating tidal mode de3 diurnal eastward wave number 3 global ionospheric maps produced by the jet propulsion laboratory were used to deduce the latitudinal integration of total electron content in the low latitude ionosphere and tidi timed observations were used to retrieve the atmospheric zonal and meridional winds by applying fourier filtering and fitting techniques the wn4 wave and de3 tidal components are derived from the ionospheric and upper atmospheric observations respectively we found that the observed wn4 wave and de3 zonal wind components experience very similar annual and interannual variations but the de3 meridional wind component behaves in a quite different manner both wn4 and de3 zonal winds are very intense during northern summer and autumn they also appear in the later spring but tend to vanish in winter their amplitudes increase as the solar activity decreases and both are stronger in the quasi biennial oscillation qbo eastward wind phase than in the westward phase at the same time the de3 meridional wind likes to occur only in winter and seems not change with solar activity and qbo phase we further studied the correlation between the wn4 wave and the two wind components of the de3 tide we found that the cross correlation coefficient between the wn4 wave and the de3 zonal wind is much larger while that between the wn4 wave and the de3 meridional wind is relatively smaller such different correlations are attributed to the different latitudinal symmetry of different de3 wind components the de3 zonal wind is likely in latitudinally symmetric tidal mode hence it can efficiently affect the f region ion drifts in contrast the meridional wind is mainly in antisymmetric mode and thus seldom affects the ionospheric drifts the present results support the suggestion that the longitudinal wn4 structure in the ionospheric f region originates from the symmetric modes mainly the zonal wind component of the upper atmospheric nonmigrating tidal mode de3 in the ionospheric e region

phase reversal of the diurnal cycle in the midlatitude ionosphere 1 the typical diurnal cycle of the midlatitude f region electron density consists of a midday maximum and a midnight minimum however a phase reversal of this diurnal cycle has been found to occur in three distinct regions on the globe they are the east asian ea region centered around 53 n 150 e the northern atlantic na region centered around 45 n 50 w and the south pacific sp region centered around 60 s 110 w the intensively reported weddell sea anomaly falls inside the sp region the phase reversal occurs during march august in ea and na regions and between august and march in sp region being most prominent in local summer furthermore this diurnal anomaly is more pronounced at solar minimum than at solar maximum and more pronounced in sp region than in na and ea regions in terms of larger diurnal magnitude and more months it lasts in a year it is emphasized that the diurnal anomaly consists of not only a nighttime enhancement but also a concurrent noontime depletion hence midlatitude summer nighttime enhancements reported in previous studies are just part of this reversed diurnal cycle the cause for the phase reversal involves several interplaying physical processes among these the neutral wind combined with the geomagnetic field configuration plays a pivotal role it generates a one wave longitudinal pattern at southern middle latitudes and a two wave pattern at northern middle latitudes whose wave peaks correspond to the center of the sp ea and na regions respectively the seasonal variation of neutral winds and downward motion of the ionization induced by thermal contraction of the ionosphere at sunset may largely control the occurring local time of the nighttime density enhancement and how long it persists in different months the phase reversal occurs as a result of close ion neutral coupling it is further noted that winter anomaly in the ea na and sp regions is very weak or missing

effect of atmospheric tides on the morphology of the quiet time postsunset equatorial ionospheric anomaly longitudinal wave number four pattern in the magnetic latitude and concentration of the f region peak ion density when measured at a fixed local time in a new comparison of two data sets with observations made by the ogo 4 satellite this pattern is seen to be persistent over many days around equinox during magnetically quiet conditions close to solar maximum but can be dominated by other processes such as cross equator winds during other periods it is found that the longitudinal variability is created by a processes occurring in the dayside ionosphere a longitudinal modulation of the dayside equatorial fountainisthemostlikelydrivingmechanism throughcomparisonwithgwsm 02model it isshownthatthepredictedmodulationofthedaysidethermosphericwindsandtemperaturesat e region altitudes created by non migrating diurnal tides can explain the modulation in the dayside equatorial fountain this result highlights the importance of understanding the temporal variability of tropospheric weather systems on our understanding and possible predictability of the development of the f region ionosphere it may also provide a possible further means of testing our understanding of atmospheric tides on a global scale

hydrological response of small watersheds following the southern california painted cave fire of june 1990 following the painted cave fire of 25 june 1990 in santa barbara california which burned 1214 ha an emergency watershed protection plan was implemented consisting of stream clearing grade stabilizers and construction of debris basins research was initiated focusing on hydrological response and channel morphology changes on two branches of maria ygnacio creek the main drainage of the burned area research results support the hypothesis that the response of small drainage basins in chaparral ecosystems to wildfire is complex and flushing of sediment by fluvial processes is more likely than by high magnitude debris flows during the winter of 1990 1991 35 66 cm of rainfall and intensities up to 10 cm per hour for a five minute period were recorded with a seasonal total of 100 of average normal rainfall average 63 cm year during the winter of 1991 1992 48 74 cm of rainfall and intensities up to 8 cm per hour were recorded with a seasonal total of 115 of normal even though there was moderate rainfall on barren saturated soils no major debris flows occurred in burned areas the winter of 1992 1993 recorded total precipitation of about 170 of normal annual average intensities were relatively low and again no debris flows were observed the response to winter storms in the first three years following the fire was a moderate but spectacular flushing of sediment most of which was derived from the hillslopes upstream of the debris basins the first significant storm and stream flow of the 1990 1991 winter was transport limited resulting in large volumes of sediment being deposited in the channel of maria ygnacio creek the second storm and stream flow was sediment limited and the channel scoured debris basins trapped about 23 000 m3 the majority coming from the storm of 17 20 march 1991 sediment transported downstream during the three winters following the fire and not trapped in the debris basins was eventually flushed to the estuarine reaches of the creeks below the burn area where approximately 108 000 m3 accumulated changes in stream morphology following the fire were dramatic as pools filled with sediment which greatly smoothed longitudinal and cross sectional profiles major changes in channel morphology occur following a fire as sediment derived from the hillslope is temporarily stored in channels within the burned area however this sediment may quickly move downstream of the burned region where it may accumulate reducing channel capacity and increasing the flood hazard ecological consequences of wildfire to the riparian zone of streams in the chaparral environment are virtually unknown but must be significant as the majority of sediment particularly gravel necessary for fish and other aquatic organisms entering the system does so in response to fires 1997 john wiley sons ltd

tropospheric tidal effects on the middle and upper atmosphere 1 numerical experiments that explore the effects of tides of tropospheric origin on the upper and middle atmosphere reveal strong signatures of an eastward propagating zonal wave number 3 diurnal tide de3 which peaks near 110 km and penetrates into the upper thermosphere we demonstrate that nonmigrating tidal dissipation dominated by de3 effects in the upper mesosphere and lower thermosphere mlt strongly accelerates the zonal mean wind field affecting both the altitude and magnitude of the low latitude jets we also quantify for the first time a stationary planetary wave 4 oscillation spw4 in the mlt which is excited by nonlinear interaction between the de3 and the migrating diurnal tide dw1 our results suggest that the spw4 modulates the de3 mlt response and may impact the e region dynamo as well as ionospheric and thermospheric signatures at much higher altitudes