solar and lunar tidal variabilities in gps tec and geomagnetic field variations seasonal as well as during the sudden stratospheric warming of 2010 the global positioning system gps deduced total electron content tec data at 15 n geomagnetic which is the northern crest region of equatorial ionization anomaly are used to study solar and lunar tidal variabilities during the years 2008 and 2009 and also during the 2009 2010 winter when a major sudden stratospheric warming ssw event has occurred the diurnal and semidiurnal tidal amplitudes show semiannual variation with maximum amplitudes during february march and september november whereas terdiurnal tide is larger during april september they show significant longitudinal variability with larger smaller amplitudes over 250 e 150 e 200 e 250 e lunar semidiurnal tidal amplitudes show sporadic enhancements during northern winter months and negligible amplitudes during northern summer months they also show notable longitudinal variabilities the solar migrating tides dw1 and sw2 show semiannual variation with larger amplitudes during spring equinox months whereas tw3 maximizes during northern summer dw2 shows larger amplitudes during summer months during the ssw except tw3 the migrating tides dw1 and sw2 show considerable enhancements among solar nonmigrating tides sw1 tw2 and ds0 show larger enhancements solar tides in tec and equatorial electrojet strength over tirunelveli vary with the time scale of 60 days during october 2009 march 2010 similar to ozone mass mixing ratio at 10 hpa and this confirms the vital role of ozone in tidal variabilities in ionospheric parameters lunar tidal amplitudes in changes in horizontal component of geomagnetic field h are larger over tirunelveli a station near dip equator solar semidiurnal tides in h have larger amplitudes than lunar tides over polar stations mawson and godhavn

present and recent sedimentation in the loyalty basin along the thio lifou profile new caledonia southwest pacific abstract the loyalty basin northeast of new caledonia is about 100 km wide and 2350 m deep in the transect between thio new caledonia and the island of lifou it is bounded to the southwest by new caledonia and its surrounding barrier reef and to the northeast by the barrier reef of the loyalty ridge lifou island a raised atoll is an emerged part of the loyalty ridge the sediments cored in the loyalty basin during the biocal mission in 1985 are bioturbated and composed of an alternation of turbidites and hemipelagites the hemipelagites are brown yellowish muddy oozes to calcareous muds the turbidites are composed of sandy and silty oozes capped transitionally with muddy oozes the hemipelagite and the t e division of the bouma sequence have different characteristics but are not located in the core however they can be distinguished by carbonate composition and grain size all the sediments originate from five sources 1 new caledonia quartz mud and heavy minerals 2 the barrier reef fragments of algae madreporarian corals foraminifera and mud of the periplatform 3 plankton foraminifera coccoliths and pteropoda 4 the bathyal community and 5 pyroclastic fragments turbidites distributed in cores between thio and lifou constitute a low profile submarine fan fed by the main canyons of the slope opposite the thio pass the fan developed from a rim of slumps and mud flows located near the base of the slope the fan extends 50 km toward the northeast as far as the tectonic levi ridge the hemipelagites are predominant beyond this ridge the modern sedimentation rate is 60 m ma on the proximal fan it is 4 6 times less than the average sedimentation rate calculated for the period since the origin of the basin in the late eocene

landform effect on rockfall and hazard mapping in cappadocia turkey the cappadocia region has unique geomorphological features resulting from differential erosional processes which make it very attractive to tourists besides the fairy chimneys for which the area is best known there are also impressive buttes and mesas buttes and mesas are formed in regions having flat lying strata in which the uppermost levels are composed of well cemented limestones and granular ignimbrites whereas the lower parts and slopes consist of low durability tuff and ignimbrites this durability difference results in serious rockfall events this study involves two dimensional rockfall analyses in and near the avanos zelve and cavusini areas where volcano sedimentary units of neogene age outcrop to provide a rockfall hazard map in which areas of tourism activity are also considered

the 8 hour tide in the arctic mesosphere and lower thermosphere an all sky vhf meteor radar at esrange 68 n 21 e near kiruna in northern sweden has been used to investigate the 8 hour tide in the arctic mesosphere and lower thermosphere we present a climatology of the 8 hour tide over the period october 1999 to april 2001 the tide appears to be a persistent feature of the arctic atmosphere although a large day to day variability of the tidal amplitude is observed at times the 8 hour tide reaches amplitudes over 30 m s 1 the amplitude of the tide increases with height across the observed height range of 80 100 km monthly mean tidal amplitudes range from 2 m s 1 to values as large as 10 m s 1 a clear seasonal behavior is apparent with maximum amplitudes observed in the autumn vertical wavelengths are shortest in winter and spring 25 35 km and longest in summer and autumn 50 90 km at least on some occasions the vertical wave number relationships between the 8 12 and 24 hour tides suggest that the 8 hour tide is being generated by nonlinear interaction between the 12 and 24 hour tides

the effects of rockfall volume on runout distance the main goal of this paper is to clarify the effects of rockfall volume on its fluidization for this purpose outdoor rockfall experiments were carried out to analyze runout distances and individual movements of rockfall blocks and numerical simulations were conducted for these experiments to learn more about the mechanism of rockfall fluidization the rockfall experiments were conducted using an artificial slope on which granite slabs were surfaced and overlaid with cubiformed granite blocks the size and number of blocks were varied in this series of experiments further numerical simulations were carried out in which the coordinates of individual rockfall blocks were traced in three dimensional space from rockfall initiation to final deposition it became clear from the experiments and simulations that the runout distance had a positive correlation with the rockfall volume number of rockfall blocks and the runout distance of the gravity center of deposited rockfall mass had a negative correlation with the rockfall volume to clarify the mechanism of these two phenomena the positions of individual blocks from initial arrangements to final depositions were traced in the experimental and numerical simulations this revealed that the relative positions of each block along the slope direction were not changed during rockfall movement the reason for the block sequence preservation was that front facing blocks in the initial cube arrangement accelerated and rear facing blocks decelerated along the slope by internal collision between blocks further as the rockfall volume increased the opportunities for impact among the rockfall blocks increased with the front facing blocks pushed farther whereas the gravity center of the deposited rockfall mass had an inclination to travel shorter distances as rockfall blocks increased according to the increase of kinetic energy dispersed by the collision of blocks

terdiurnal migrating tide signature in ionospheric total electron content we report the latitudinal seasonal and solar cycle variations of terdiurnal migrating tide i e terdiurnal westward wave number 3 tw3 signature in ionospheric total electron content tec our investigations are based on the jpl global ionospheric maps gims during 1999 2011 the absolute amplitude of tw3 exhibits maximum values in the magnetic equatorial region which reaches about 8 tecu under high solar activity and 1 5 tecu under low solar activity the relative amplitude of zonal mean tec in equatorial region however shows persistent patterns from 1999 to 2011 with little solar activity dependence the relative amplitude of tw3 has a peak of similar to 10 in the magnetic equatorial region and a second one of similar to 7 at magnetic middle latitudes 30 degrees 50 degrees at high latitudes in local winter seasons the maximum relative amplitude occurs which varies between 8 and 15 with slightly larger amplitudes in the northern hemisphere the global structure of tw3 signature in tec should shed some light on the coupling between the ionosphere thermosphere and the lower atmosphere

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

the terdiurnal tide in the mesosphere and lower thermosphere over london canada 43 n 81 w radars have been used successfully for many years to measure atmospheric diurnal and semidiurnal tides but studies of the atmospheric terdiurnal tide have only rarely been reported to date in the literature in this paper we investigate the amplitude phase and vertical wavelength for the terdiurnal tide using the university of western ontario uwo 2 mhz radar near london canada emphasis is placed on short term monthly seasonal and annual variations of the terdiurnal tide the results of the present study bring out certain new aspects of the terdiurnal tide at midlatitudes in the northern hemisphere we show that terdiurnal tides have significant amplitudes in the mesosphere and lower thermosphere indeed the terdiurnal amplitudes are often comparable to the diurnal ones we also draw attention to the annual variability and especially highlight the occurrence of the terdiurnal tide in non winter months for example the occurrence of the terdiurnal tide in spring months is not uncommon thus it seems that the 8 hour component observed over london canada cannot be explained by the terdiurnal tide being due to solar heating alone particular cases of the terdiurnal tide are examined and the observed amplitude and phase profiles of the terdiurnal tide at certain times of the year are discussed in terms of nonlinear interaction between the diurnal and semidiurnal tides we suspect that this effect may also explain the fact that diurnal and semidiurnal tides at our station often seem suppressed relative to other sites thayaparan et al 1995a on the basis of our previous and present observations it is also possible that large terdiurnal amplitudes observed at certain times of the year may be partly explained in terms of tidal gravity wave interactions however this possibility needs to be further investigated in the future

terdiurnal tidelike variability in sporadic e layers 1 time series analysis was performed on a large database of ionosonde recordings taken over 12 years for the 6 month period from the beginning of may to the end of october when sporadic e layer occurrence is frequent the results show that in addition to the well known 24 and 12 hour tidal variations there is also a weaker but regular 8 hour periodicity in midlatitude sporadic e layers es statistically this terdiurnal periodicity is significant and occurs in both the sporadic e layer critical frequency foes and the layer virtual height h es becoming strongest around summer solstice and later in october after a minimum in september at times a weak 6 hour periodicity can also be present in es but its effects are much less significant than those of the 8 hour oscillation the 8 hour periodicity in es is attributed to the terdiurnal tide presumably acting through its vertical wind shear forcing of the metallic ions in the lower thermosphere the relation to the terdiurnal tide was inferred from simultaneous ionosonde recordings from three widely spaced stations in the same midlatitude zone showing the 8 hour oscillation to be present simultaneously in all ionosonde stations and have phases which are consistent with a westward propagating terdiurnal wave of zonal wave number 3 the present study establishes the regular occurrence of a terdiurnal tidelike oscillation in es which needs to be incorporated into the physics and modeling of sporadic e layer formation and dynamics

combining field and modelling techniques to assess rockfall dynamics on a protection forest hillslope in the european alps adequate management of a mountain forest that protects downslope areas against impacts of rockfall requires insight into the dynamics of the hillslope environment therefore we applied a combined approach using field and modelling techniques to assess the determining factors for rockfall source areas rockfall tracks and rockfall runout zones on a forested slope in mountainous terrain the first objective of this study was to understand why rockfall occurs in the study area the second objective was to translate the knowledge obtained in the field into a model that simulates rockfall dynamics on a forested slope realistically the third objective was to assess which hillslope characteristics primarily determine the distribution of active rockfall tracks to achieve these objectives we made a geomorphological map of the whole study area and we measured the major discontinuity planes in the bedrock that are exposed in the rockfall source areas furthermore a test site for simulation modelling within the larger study area was defined in which both a forest and a hillslope inventory were carried out the available data and our developed rockfall simulation model allowed us to assess the slope characteristics that mainly determine the distribution of areas affected by rockfall we found that in decreasing order of importance both standing and felled trees the surface roughness and rockfall resistant shrubs primarily determine the distribution of rockfall affected areas simulation tests without a forest cover produced similar rockfall runout zones as fossil rockfall events identified in the field we believe that the combined field and modelling approach is a prerequisite for understanding how forests can protect against rockfall

rockfall hazard assessment in a cultural and natural heritage ortahisar castle cappadocia turkey the cappadocia region is one of the most important tourism centers of turkey owing to its natural beauty and historical heritage the natural landscapes predominantly contribute to the tourism capacity of the region this is controlled directly by the characteristic lithological units and surface processes however rockfall events which are sometimes observed in the region are typical natural hazards conditioned by discontinuities steep topography and human activities the ortahisar castle is one of the natural monuments and also one of the historical places of this region this castle is located on a steep hill formed by jointed ignimbrite and its height and settlement area are approximately 50m and 500m2 respectively however some blocks on the castle have begun to exhibit serious rockfall potential rock hewn structures carved by man for various purposes contribute to increase in rockfall hazard for this reason the castle was closed to touristic visits the purpose of this study was to evaluate this hazard potential and perform a series of rockfall analyses and discuss the results besides location and dimension of fallen blocks were determined at the final stage of the fieldwork location and size of detached blocks having potential to fall were described during the analysis stage runout distance bounce height kinetic energy and velocity of the detached blocks were determined by using rocfall v 4 software the results obtained from rockfall analyses were used to map the areas under rockfall threat in the close vicinity of the castle and the potential risk was interpreted

modeling and analysis of the structure and generation of the terdiurnal tide the terdiurnal or 8 h tide has been seen in a number of midlatitude radar measurements and has recently been mapped globally at 95 km a series of calculations and model simulations are used to examine the processes responsible for generating this tide and for its strong hemispheric asymmetry the model tidal structure deviates significantly from the structure of a single hough mode in contrast to the diurnal tide the dominant cause of the hemispheric asymmetry is the sensitivity of the propagation to the background state particularly the static stability several conceptual views of the tide are explored to give a heuristic view of this asymmetry this analysis predicts that particular modes are prohibited from propagating in large regions of the summer mesosphere the tide occurs naturally in a three dimensional nonlinear model extending from the tropopause to the lower thermosphere the model tide shows a number of features in common with observations including amplitude maxima in midlatitudes a wintertime peak and zonal winds larger than meridional winds the tidal amplitude in the model is weaker than observed at 95 km several interactive model integrations are performed to determine the forcing mechanism for the tide these calculations indicate that the direct solar forcing of the terdiurnal tide is the dominant mechanism occurring in the model at middle and high latitudes nonlinear interactions contribute to the low latitude tide

assessment of environmental and engineering geological problems for the possible re use of an abandoned rock hewn settlement in urgup cappadocia turkey the cappadocia region of central anatolia having a very distinct culture is one of the attractive touristic sites of turkey due to its spectacular and unique landforms and historical heritages in this region the structures carved into thick to massive tuffs survived and kept their original integrity for a number of centuries environmental and anthropological factors at the cappadocia region have been the main reasons for extensive subsurface and multi purpose use in the past and present in addition thermal insulation properties of the tuffs make these rocks suitable for use in underground openings the kayakapi neighborhood located in the town of urgup is one of the famous historical sites this site is situated within the goreme national park and the rock sites of cappadocia which was inscribed on the world heritage list in 1985 in order to develop the tourism potential of this abandoned site while preserving its cultural and natural values a natural environmental conservation and revitalization project was initiated as an integral part of this project in this study environmental and engineering geological problems including rock fall potential and stability of about 1 200 rock hewn structures were investigated and an inventory was prepared for the possible re use of the underground openings and other structures at the site and remedial measures were recommended the assessments based on observations and experimental studies indicated that the tuffs do not show significant changes both perpendicular and parallel to layering and discontinuities and rock weathering seem to be more important factors controlling the stability of rock hewn structures the major stability problems threatening the re use of the openings are structurally controlled block instabilities overbreaks and erosion and shearing of the pillars made of tuff on the other hand the area at the entrance of the site requires some protection measures such as the construction of a retaining wall systematic bolting of rock slabs and removal of some blocks having rock fall potential the inventory for the openings suggests that there are a number of openings that can be re used after necessary remedial measures

global response of the ionosphere to atmospheric tides forced from below comparison between cosmic measurements and simulations by atmosphere ionosphere coupled model gaia 1 this paper for the first time presents a detailed comparison between simulated and observed global electron density responses to different atmospheric tides forced from below the recently developed earth s whole atmospheric model from the troposphere to the ionosphere called gaia has been used for the simulation of the electron density tidal responses they have been compared with the extracted from the cosmic electron density data tidal responses for the period of time october 2007 to march 2009 particular attention has been paid to the nonmigrating de3 de2 and migrating dw1 sw2 and tw3 electron density responses the gaia model reproduced quite well the cosmic de3 de2 responses both simulations and observations revealed three altitude regions of enhanced electron density responses 1 an upper level response above 300 km height apparently shaped mainly by the fountain effect 2 a response located near altitudes of 200 270 km and 3 a lower thermospheric response situated near 120 150 km height a possible mechanism is suggested for explaining the two lower level responses for the first time the gaia model simulations supported the observational evidence found in the cosmic measurements that the ionospheric wn4 wn3 longitude structure is not generated only by the de3 de2 tide as it has been often assumed as regards the comparison of the migrating dw1 sw2 and tw3 responses the obtained results clearly demonstrate that the gaia model reproduce very well of the sw2 and tw3 cosmic electron density responses the only main discrepancy is seen in the migrating dw1 response the observation does not support the splitting of the simulated response at both sides of the equator this is due mainly to the difference between the saber and gaia sw2 tide in the lower thermosphere as it turned out that the dw1 electron density response strongly depends on the mean features of the lower thermospheric sw2 tide

rockfall activity from an alpine cliff during thawing periods abstract rockfall activity during thawing periods was investigated by collecting rockfall debris fallen on the snow covered talus slope in a cirque in the japanese alps near surface rock temperature was also monitored on the cirque wall maximum rockfall activity occurs on average about 10 days after the meltout of the cirque wall the intensive activity is rarely associated with precipitation events or diurnal frost cycles on the rockface a thermal conduction model suggests that rockfalls at this site occur most frequently when the seasonal thawing front penetrates to a depth of about 1 m in the bedrock while the freeze thaw penetration controls the maximum dimensions of detachable rock mass joint spacing on the rockface affects the size distribution of rockfall debris boulder falls resulting from seasonal frost weathering are considered to be the most important process responsible for the contemporary modification of the cirque wall the rockfall volume during a thawing period is usually 1 3 m3 which is equivalent to the rate of cirque wall retreat of the order of 0 01 mm year 1 however big boulder falls that occur once per decade can increase the retreat rate significantly

terdiurnal tide in the extended canadian middle atmospheric model cmam 1 we use the extended canadian middle atmosphere model cmam a general circulation model gcm to investigate the nature of the terdiurnal tide temperature and horizontal winds from a model run are analyzed to delineate the character of this tide for zonal wave numbers s 5 to 5 descriptions of the annual mean amplitudes seasonal variations and total tide superposed from the migrating and 10 nonmigrating components are provided the amplitudes and vertical wavelengths of the various components and the total terdiurnal tide are found to depend strongly on season latitude and altitude the migrating terdiurnal component maximizes at mid and high latitudes with significant amplitudes annual mean amplitude in wind temperature 10 m s k in the upper mesosphere and lower thermosphere mlt region between 80 and 100 km maximum amplitudes occur in winter in both hemispheres whereas above 100 km maximum amplitudes occur during solstices for the zonal wind field the nonmigrating terdiurnal components te5 te3 te4 tw4 and tw5 tend to peak at 50 n s with amplitudes between 2 and 8 m s the other nonmigrating components maximize in the polar regions with amplitudes of 2 10 m s possible generation mechanisms solar heating and nonlinear interactions for the migrating terdiurnal tide in the mlt region are also examined correlation analysis indicates that nonlinear interactions between the migrating diurnal and semidiurnal tides are unlikely to be the source of the migrating terdiurnal tide

incoherent scatter radar study of the terdiurnal tide in the e and f region heights at arecibo 1 we report the analysis of the terdiurnal tide in the meridional wind from 90 to 350 km at a low latitude station our data is based on nine days of consecutive observation made by the arecibo incoherent scatter radar during january 14 23 2010 the terdiurnal tide is observed to be prominent at e region heights in the first four days jan 14 18 and at the f region heights in the last five days jan 18 23 the terdiurnal tide is among the two strongest tidal components in both regions the vertical wavelength of the terdiurnal tide is about 100 km and 950 km for the altitude range of 128 to 142 km and 180 to 320 km respectively the f region terdiurnal tide amplitude is found to be well correlated with the background meridional wind in the lower f region our analysis does not reveal any evidence that non linear interaction between diurnal and semidiurnal tides is important for the f region terdiurnal tide

mio pliocene basin development in the eastern part of the cappadocian volcanic province central anatolia turkey and its implications for regional tectonics the cappadocian volcanic province cvp comprises predominantly of a thick succession of volcanogenic rocks and interbedded siliciclastic sediments of middle miocene to recent age in central anatolia turkey the conditions of basin development in the eastern part of the cvp have been elucidated by using sedimentological and geomorphological approaches the prevailing tectonic regime its extent and causes are also discussed sedimentological analysis supported by geomorphological observations revealed a major ne trending probably normal border fault and its several synthetics this tectonic element constitutes the se margin of the basin and divided the cvp from the tauride range during middle miocene to pliocene the basin fill in the study area comprises gravelly alluvial fans near the border fault while fluvial clastics and lacustrine carbonates dominate towards the centre some pyroclastic rocks and lava flows are also made part of the fill the southeastern basin margin is characterized morphologically by a number of uplifted basement blocks probably associated with synthetic faults and some deeply incised canyons in the footwall these canyons were subsequently filled with a mid pliocene ignimbrite sheet and represent the sediment supply conduits to the basin the cessation of filling in the basin was determined by strike slip faults that uplifted and detached the basin about 2 6 ma this date also marks the onset of the neotectonic period in the region the overall extensional tectonic regime inferred for the eastern cvp appears coeval with events recognised in the southern basins i e adana and mut basins and the eastern mediterranean some physical connections between these basins also have been demonstrated it is suggested that the cvp and the southern basins were all created during a phase of extension resulting from continued northward subduction of the african plate beneath the eurasia during the late cenozoic

on the occurrence and variability of the terdiurnal tide in the equatorial mesosphere and lower thermosphere and a comparison with the kyushu gcm 1 we studied the occurrence characteristics and variability of the terdiurnal tide 8 hour period in the equatorial mesosphere and lower thermosphere mlt using a meteor radar at koto tabang 0 2 s 100 3 e and mf radars at tirunelveli 8 7 n 77 8 e and pameungpeuk 7 4 s 107 4 e these locations one being located right over the equator and the other two at conjugate points around the equator within 10 form a unique experimental setup to study equatorial mlt dynamics the terdiurnal tide exists as a distinct wave signature at all three locations while the daily amplitudes can be as large as 15 m s 1 the monthly mean amplitudes lie between 1 and 10 m s 1 the amplitude of the terdiurnal tide at pameungpeuk is generally smaller than that observed at tirunelveli and koto tabang the seasonal variation in amplitude shows both annual and semiannual oscillations of 1 m s 1 at all three locations the present observations combined with previous reports indicate that the timing of the primary maximum of the terdiurnal tide amplitude shifts from autumn to late spring and early summer as one moves from high latitudes to the equator all with respect to the northern hemisphere the amplitudes and seasonal variation in the present observations show good comparison with that simulated by the general circulation model gcm developed by kyushu university japan this study supports the occurrence of nonlinear interaction between diurnal and semidiurnal tides and shows that gravity waves play an important role in the generation of the terdiurnal tide

structure of the terdiurnal tide at 95 km satellite wind observations from the high resolution doppler interferometer hrdi instrument on the upper atmosphere research satellite uars are used to describe the latitudinal structure and seasonal variation of the terdiurnal 8 hour atmospheric tide at 95 km the amplitude of the annual average tide is 5 m s meridional and 15 m s zonal within the range observed 60 s to 60 n the maximum amplitudes are found during fall and winter at midlatitudes only weak temporal correlations with the diurnal and semidiurnal tides are seen on the monthly time scales resolved