gravity wave propagation and dissipation from the stratosphere to the lower thermosphere 1 one night 28 october 2003 temperature and horizontal wind measurements by a resonance sodium na wind temperature lidar at maui 20 7 n 156 3 w and temperature measurement by a rayleigh lidar at mauna loa observatory mlo 19 5 n 155 6 w hawaii were used to study gravity wave gw propagation from the lower stratosphere to the lower thermosphere a dominant wave mode was identified from 35 to 103 km the wave was partially dissipated and propagating upward with a scale height of temperature amplitude at 14 km a damping layer was present around the stratopause where the wave amplitude was small which also corresponded to a low static stability layer the vertical wavelengths were larger in the mesosphere 12 13 km than in the stratosphere 6 7 km consistent with the decreasing static stability with altitude hodograph analysis of the na lidar wind data showed that the wave was propagating northward and the horizontal wavelength was 2140 km and intrinsic period was 15 h in the region 84 103 km the apparent period was 6 h and consistent with doppler shift of the background wind it is suggested that the convective zone over the equator to the south of hawaii provided a constant gw source that is responsible for the observed gw throughout the night

bias corrected population size distribution and impact hazard for the near earth objects abstract utilizing the largest available data sets for the observed taxonomic binzel et al 2004 icarus 170 259 294 and albedo delbo et al 2003 icarus 166 116 130 distributions of the near earth object population we model the bias corrected population diameter limited fractional abundances of the taxonomic complexes are a 0 2 c 10 d 17 o 0 5 q 14 r 0 1 s 22 u 0 4 v 1 x 34 in a diameter limited sample 30 of the neo population has jovian tisserand parameter less than 3 where the d types and x types dominate the large contribution from the x types is surprising and highlights the need to better understand this group with more albedo measurements combining the c d and x complexes into a dark group and the others into a bright group yields a debiased dark to bright ratio of 1 6 overall the bias corrected mean albedo for the neo population is 0 14 0 02 for which an h magnitude of 17 8 0 1 translates to a diameter of 1 km in close agreement with morbidelli et al 2002 icarus 158 2 329 342 coupling this bias corrected taxonomic and albedo model with the h magnitude dependent size distribution of stuart 2001 science 294 1691 1693 yields a diameter distribution with 1090 180 neos with diameters larger than 1 km as of 2004 june the spaceguard survey has discovered 56 of the neos larger than 1 km using our size distribution model and orbital distribution of stuart 2001 science 294 1691 1693 we calculate the frequency of impacts into the earth and the moon globally destructive collisions 10 21 j of asteroids 1 km or larger strike the earth once every 0 60 0 1 myr on average regionally destructive collisions with impact energy greater than 4 10 18 j 200 m diameter strike the earth every 56 000 6000 yr collisions in the range of the tunguska event 4 8 10 16 j occur every 2000 3000 yr these values represent the average time between randomly spaced impacts actual impacts could occur more or less closely spaced solely by chance as a verification of these impact rates the crater production function of shoemaker et al 1990 geological society of american special paper 247 has been updated by combining this new population model with a crater formation model to find that the observed crater production function on both the earth and moon agrees with the rate of crater production expected from the current population of neos

airborne sodium lidar observations of horizontal and vertical wave number spectra of mesopause density and wind perturbations we present kinetic energy horizontal and vertical wave number spectra of wind and density perturbations at mid latitudes for the altitude range from approximately 80 to 100 km the spectra are inferred from na density profiles collected with an airborne lidar during two flights conducted in november 1986 the two flights included one round trip from denver colorado to springfield illinois and another round trip from denver to the pacific coast the horizontal wave number spectra exhibited an approximately kh 1 2 dependence at horizontal scales from 70 to 700 km while the vertical wave number spectra exhibited an approximately kz 2 7 dependence at vertical scales from 2 to 10 km these spectra are compared with spectra obtained from ground based lidar radar shuttle re entry and global atmospheric sampling program observations the rms horizontal wind velocity inferred from the airborne na lidar data increased with time and with longitude from the pacific coast to the great plains the inferred mean rms horizontal wind velocity was 32 m s 1 and the mean horizontal velocity variance was about 1100 m2 s 2 this horizontal velocity variance is comparable to horizontal velocity variances inferred from radar observations but larger than horizontal velocity variances inferred from shuttle re entry observations during the round trip flight from denver colorado to springfield illinois two quasi monochromatic waves were observed the longer wavelength wave had an intrinsic zonal wavelength of 772 km intrinsic zonal phase velocity of 35 m s 1 westward and intrinsic period of 6 1 hours this wave appears to be propagating almost due west the shorter wavelength wave had an intrinsic zonal wavelength of 263 km zonal phase velocity of 43 m s 1 westward and period of 1 7 hours

gravity wave and equatorial wave morphology of the stratosphere derived from long term rocket soundings fluctuations in vertical profiles of atmospheric temperature and horizontal wind in the 20 60 km altitude range have been isolated from meteorological rocket measurements during 1977 87 at 15 widely separated sites the seasonal geographical and vertical variability of the variance of horizontal velocities u 2 2 and relative temperature perturbations t 2 were studied the bulk of the variance of both quantities in the 2 10 km and 2 20 km vertical wavelength bands was associated with gravity wave motions although in depth study of the wave polarization shows that planetary scale equatorial wave modes contribute to the variance at equatorial sites annual mean variances varied widely among the 15 stations suggesting appreciable geographical variability in stratospheric wave activity

observations of high frequency temporal gravity wave spectra in the middle upper stratosphere there is a paucity of high frequency temporal gravity wave spectra in the middle upper stratosphere 30 40 km as most instruments that are capable of accessing this region do not have the capability to make measurements for any extended period of time the spectral analysis of density fluctuations obtained with the purple crow rayleigh scatter lidar has shown that middle upper stratospheric temporal spectra follow the expected 1 5 to 2 0 power law relationship for frequencies less than 1 10 3 s 1 at frequencies greater than 1 10 3 s 1 the shape of the temporal spectrum is much more variable with strong quasi monochromatic features appearing intermittently on certain nights these higher frequency features have been attributed to nonlinear wave interactions and suggest that estimates of gravity wave activity in the middle upper stratosphere may be larger and much more variable than previously assumed this variability also suggests that middle upper stratospheric energy dissipation and eddy diffusion values may be much larger and more variable than previously assumed current parameterizations of subgrid dynamical processes in general circulation models that resolve this region may need to be reexamined in this light

rayleigh lidar measurements of the temporal frequency and vertical wavenumber spectra in the mesosphere over the rocky mountain region temporal and spatial spectral analysis techniques were applied to lidar data collected over a period of 18 months above the rocky mountain region at an altitude range from 45 to 70 km by a rayleigh lidar system located in logan utah 41 7 n 111 8 w examination of the averaged temporal frequency f and vertical wavenumber f m spectra showed spectral slope values of 1 49 0 03 and 2 3 0 1 respectively the observed slope for the overall averaged f m spectrum is considerably more positive than the value of 3 predicted by the linear instability theory but close to the value of 2 that is predicted by the scale independent diffusive filtering theory using the measured f slope parameter however examination of the monthly averaged f m spectra for the transition from winter to summer showed the spectra became flatter suggesting that doppler shift effects caused by the seasonal change in the magnitude and direction of the background wind field are significant the characteristic vertical wavelength was found to be 12 km for the altitude region of 45 70 km comparison of this value with the characteristic wavelengths from other lidar observations at lower and higher altitude ranges showed an overall increase of with height the observed enhancement of the f m spectral magnitude in winter is believed to be caused in part by the low frequency wave activity observed in the temperature profiles

rayleigh lidar observations of quasi sinusoidal waves in the tropical middle atmosphere 1 rayleigh lidar observations of temperature for 2 7 hours on 38 nights during the period of 18 january 5 march 1999 and for 3 hours on 29 nights during 29 february 2 april 2000 in the altitude region of 27 60 km over gadanki 13 5 n 85 e clearly show the dominance of the quasi sinusoidal waves of periods in the range of 6 13 hours in temperature in the tropical middle atmosphere during 1999 the vertical wavelength of these waves ranges from 7 1 to 17 km with a mean value of 12 0 2 4 km while during 2000 it ranges from 5 5 to 17 km with a mean value of 11 4 3 5 km the wave periods estimated from the observations during 1999 are generally greater than the observation period on each night and are estimated to be in the range of 6 5 13 1 hours with an average period of 9 7 1 8 hours which is significantly smaller than the inertial period of 53 hours the amplitudes of these waves are in the range of 1 to 8 k such sinusoidal wave modes are clearly discernible in the temperature profiles for 50 nights of observation another striking feature is that the quasi sinusoidal structure is clearly observed in the equivalent day analysis also indicating only small day to day variability in phase a property that is characteristic of atmospheric tides

rayleigh lidar observations of mesosphere temperature structure ground based observations of atmospheric density profiles to 92 km were obtained for four successive seasons between summer 1989 and spring 1990 these results were obtained with a powerful rayleigh lidar facility located at wright patterson air force base dayton ohio this instrument combined a 14 w xef laser transmitter with a 2 54 m receiver mirror to observe returns from altitudes between 40 and 95 km analysis of the scale height dependence of the density profiles produced temperatures with a measurement error of about 5 k 2 5 at 90 km when the lidar data was averaged for 20 min and smoothed in height over 2 7 km examination of these profiles for the total of 18 nights showed that there often existed in the mesophere a layer of enhanced temperatures when compared with the u s standard profile the layer centroid height was about 85 km for summer and 70 to 75 km for winter data obtained for the equinoctial periods showed the amplitude of these layers to be weak the winter temperature profiles showed evidence forlong period waves passing through the region of the thermal anomaly while the equinox profiles revealed more sporadic wave activity with shorter vertical wavelengths both the winter and summer temperature data displayed regions where the observed lapse rate approached the adiabatic lapse rate in the summer the wave activity near the inversion layer was weak

improved middle atmosphere climate and forecasts in the ecmwf model through a nonorographic gravity wave drag parameterization abstract in model cycle 35r3 cy35r3 of the ecmwf integrated forecast system ifs the momentum deposition from small scale nonorographic gravity waves is parameterized by the scinocca scheme which uses hydrostatic nonrotational wave dynamics to describe the vertical evolution of a broad constant and isotropic spectrum of gravity waves emanating from the troposphere the cy35r3 middle atmosphere climate shows the following i an improved representation of the zonal mean circulation and temperature structure ii a realistic parameterized gravity wave drag iii a reasonable stationary planetary wave structure and stationary wave driving in july and an underestimate of the generation of stationary wave activity in the troposphere and stationary wave driving in january iv an improved representation of the tropical variability of the stratospheric circulation although the westerly phase of the semiannual oscillation is missing and v a realistic horizontal distribution of momentum flux in the

noctilucent clouds and wave dynamics observations at sondrestrom greenland rayleigh lidar measurements of the arctic summer stratosphere and mesosphere have been conducted routinely since 1994 at the sondrestrom atmospheric research facility near kangerlussuaq greenland 67 0n 50 9w between 1994 and 1996 seventeen separate events of noctilucent clouds nlcs as well as corresponding stratospheric wave structure have been observed we present in this study two main results 1 the occurrence of persistent quasi monochromatic wave structure in the stratosphere having observed vertical wavelengths of 8 to 12 km and observed temporal periods of approximately 2 3 hours and 2 evidence that the strength of such lower altitude waves may be associated with the overall strength of the observed nlc volume backscatter coefficient

a new method to determine the grain size of planetary regolith abstract airless planetary bodies are covered by a dusty layer called regolith the grain size of the regolith determines the temperature and the mechanical strength of the surface layers thus knowledge of the grain size of planetary regolith helps to prepare future landing and or sample return missions in this work we present a method to determine the grain size of planetary regolith by using remote measurements of the thermal inertia we found that small bodies in the solar system diameter less than 100 km are covered by relatively coarse regolith grains with typical particle sizes in the millimeter to centimeter regime whereas large objects possess very fine regolith with grain sizes between 10 m and 100 m

the surface properties of small asteroids peculiar betulia a case study abstract we present the results of extensive thermal infrared observations of the c type near earth asteroid 1580 betulia obtained in june 2002 with the 3 m nasa infrared telescope facility irtf on mauna kea hawaii betulia is a highly unusual object for which earlier radiometric observations interpreted on the basis of simple thermal models indicated a surface of high thermal inertia a high thermal inertia implies a lack of thermally insulating regolith radiometric observations of other asteroids of comparable size indicate that regolith is present in nearly all cases knowledge of the surface thermal properties of small near earth asteroids is crucial for meaningful calculations of the yarkovsky effect which is invoked to explain the delivery of collisional fragments from the main belt into near earth orbits and apparently has a significant influence on the orbital evolution of potentially hazardous near earth asteroids furthermore apart from being an indicator of the presence of thermally insulating regolith on the surface of an asteroid the thermal inertia determines the magnitude of the diurnal temperature variation and is therefore of great importance in the design of instrumentation for lander missions to small asteroids in the case of betulia our database is sufficiently broad to allow the use of more sophisticated thermal models than were available for earlier radiometric observations the measured fluxes have been fitted with thermal model emission continua to determine the asteroid s size and geometric albedo p v fits obtained with a new thermophysical model imply an effective diameter of 4 57 0 46 km and an albedo of 0 077 0 015 and indicate a moderate surface thermal inertia of around 180 j m 2 s 0 5 k 1 it is difficult to reconcile our results with earlier work which indicate a larger diameter for betulia and a high thermal inertia surface of bare rock

lidar temperature measurements of gravity waves over kuhlungsborn 54 n from 1 to 105 km a winter summer comparison 1 since august 2002 temperature measurements from 1 to 105 km are performed at the leibniz institute of atmospheric physics in kuhlungsborn 54 n with a combination of different lidars results from 14 nights in winter and 31 in summer are presented nightly mean profiles and fluctuations with a temporal and vertical resolution of 15 min and 1 km respectively are derived in both seasons wave energy propagates upward phase propagates downward with vertical phase speeds of 0 25 to 1 9 m s phase speeds are generally larger in the mesosphere compared to the stratosphere because of decreasing static stability wave periods are found in the entire range of 1 8 hours given by experimental constraints with no preference for particular periods the observed vertical wavelengths cover the entire instrumental range of 5 50 km but the majority lies below 22 km in both seasons in single nights a few waves up to three dominate the wave spectrum and represent 45 65 of the entire variability wave amplitudes generally increase with altitude with a scale height of 18 22 km i e less than expected 14 km for propagation conserving momentum flux density the gravity wave energy loss changes with altitude and is different in both seasons local fluctuation minima nodes are often observed frequently colocated with convective instabilities temperature fluctuations are generally smaller in summer compared to winter maximum values are 10 and 25 k respectively applying gravity wave polarization relations to the mean winter and summer lidar temperature profiles the difference of fluctuations is basically determined by the background conditions especially at 60 80 km

a coordinated study of 1 h mesoscale gravity waves propagating from logan to boulder with crrl na doppler lidars and temperature mapper we present the first coordinated study using two lidars at two separate locations to characterize a 1 h mesoscale gravity wave event in the mesopause region the simultaneous observations were made with the student training and atmospheric research star na doppler lidar at boulder co and the utah state university na doppler lidar and temperature mapper at logan ut on 27 november 2013 the high precision possessed by the star lidar enabled these waves to be detected in vertical wind the mean wave amplitudes are 0 44 m s in vertical wind and 1 in relative temperature at altitudes of 82 107 km those in the zonal and meridional winds are 6 1 and 5 2 m s averaged from 84 to 99 km the horizontal and vertical wavelengths inferred from the mapper and lidars are 219 4 and 16 0 0 3 km respectively the intrinsic period is 1 3 h for the airglow layer doppler shifted by a mean wind of 17 m s the wave packet propagates from logan to boulder with an azimuth angle of 135 clockwise from north and an elevation angle of 3 from the horizon the observed phase difference between the two locations can be explained by the traveling time of the 1 h wave from logan to boulder which is about 2 4 h the wave polarization relations are examined through the simultaneous quantifications of the three wind components and temperature this study has developed a systematic methodology for fully characterizing mesoscale gravity waves inspecting their intrinsic properties and validating the derivation of horizontal wave structures by applying multiple instruments from coordinated stations

rayleigh lidar observations of gravity wave activity in the upper stratosphere at urbana illinois abstract during 13 nights of rayleigh lidar measurements at urbana illinois in 1984 86 thirty six quasi monochromatic gravity waves were observed in the 35 50 km altitude region of the stratosphere the characteristics of the waves are compared with other lidar and radar measurements of gravity waves and with theoretical models of wave saturation and dissipation phenomena the measured vertical wavelengths 2 ranged from 2 to 11 5 km and the measured vertical phase velocities cz ranged from 10 to 85 cm s 1 the vertical wavelengths and vertical phase velocities were used to infer observed wave periods tob which ranged from 100 to 1000 min and horizontal wavelengths x which ranged firm 70 to 2000 km there may be errors in the inferred values of the horizontal wavelengths because they were calculated by assuming that the observed period inferred the intrinsic period dominant wave activity was found at vertical wavelengths between 2 4 km and 7 10 km no significant seasonal variations were evide

the gravity wave response above deep convection in a squall line simulation abstract high frequency gravity waves generated by convective storms likely play an important role in the general circulation of the middle atmosphere yet little is known about waves from this source this work utilizes a fully compressible nonlinear numerical two dimensional simulation of a midlatitude squall line to study vertically propagating waves generated by deep convection the model includes a deep stratosphere layer with high enough resolution to characterize the wave motions at these altitudes a spectral analysis of the stratospheric waves provides an understanding of the necessary characteristics of the spectrum for future studies of their effects on the middle atmosphere in realistic mean wind scenarios the wave spectrum also displays specific characteristics that point to low physical mechanisms within the storm responsible for their forcing understanding these forcing mechanisms and the properties of the storm and atmosphere that control them are crucial first steps toward developing

mg spinel lithology a new rock type on the lunar farside 1 high resolution compositional data from moon mineralogy mapper m3 for the moscoviense region on the lunar farside reveal three unusual but distinctive rock types along the inner basin ring these are designated oos since they are dominated by high concentrations of orthopyroxene olivine and mg rich spinel respectively the oos occur as small areas each a few kilometers in size that are widely separated within the highly feldspathic setting of the basin rim although the abundance of plagioclase is not well constrained within the oos the mafic mineral content is exceptionally high and two of the rock types could approach pyroxenite and harzburgite in composition the third is a new rock type identified on the moon that is dominated by mg rich spinel with no other mafic minerals detectable 5 pyroxene olivine all oos surfaces are old and undisturbed since basin formation they are effectively invisible in image data and are only recognized by their distinctive composition identified spectroscopically the origin of these unusual lithologies appears to be linked to one or more magmatic intrusions into the lower crust perhaps near the crust mantle interface processes such as fractional crystallization and gravity settling within such intrusions may provide a mechanism for concentrating the mafic components within zones several kilometers in dimension the oos are embedded within highly anorthositic material from the lunar crust they may thus be near contemporaneous with crustal products from the cooling magma ocean

remote compositional analysis of lunar olivine rich lithologies with moon mineralogy mapper m3 spectra 1 a systematic approach for deconvolving remotely sensed lunar olivine rich visible to near infrared vnir reflectance spectra with the modified gaussian model mgm is evaluated with chandrayaan 1 moon mineralogy mapper m3 spectra whereas earlier studies of laboratory reflectance spectra focused only on complications due to chromite inclusions in lunar olivines we develop a systematic approach for addressing through continuum removal the prominent continuum slopes common to remotely sensed reflectance spectra of planetary surfaces we have validated our continuum removal on a suite of laboratory reflectance spectra suites of olivine dominated reflectance spectra from a small crater near mare moscoviense the copernicus central peak aristarchus and the crater marius in the marius hills were analyzed spectral diversity was detected in visual evaluation of the spectra and was quantified using the mgm the mgm derived band positions are used to estimate the olivine s composition in a relative sense spectra of olivines from moscoviense exhibit diversity in their absorption features and this diversity suggests some variation in olivine fe mg content olivines from copernicus are observed to be spectrally homogeneous and thus are predicted to be more compositionally homogeneous than those at moscoviense but are of broadly similar composition to the moscoviense olivines olivines from aristarchus and marius exhibit clear spectral differences from those at moscoviense and copernicus but also exhibit features that suggest contributions from other phases if the various precautions discussed here are weighed carefully the methods presented here can be used to make general predictions of absolute olivine composition fe mg content

a survey of karin cluster asteroids with the spitzer space telescope abstract the karin cluster is one of the youngest known families of main belt asteroids dating back to a collisional event only 5 8 0 2 myr ago using the spitzer space telescope we have photometrically sampled the thermal continua 3 5 22 m of 17 karin cluster asteroids of different sizes down to the smallest members discovered so far in order to make the first direct measurements of their sizes and albedos and study the physical properties of their surfaces our targets are also amongst the smallest main belt asteroids observed to date in the mid infrared the derived diameters range from 17 3 km for 832 karin to 1 5 km for 75176 with typical uncertainties of 10 the mean albedo is p v 0 215 0 015 compared to 0 20 0 07 for 832 karin itself for h 11 2 0 3 consistent with the view that the karin asteroids are closely related physically as well as dynamically the albedo distribution 0 12 p v 0 32 is consistent with the range associated with s type asteroids but the variation from one object to another appears to be significant contrary to the case for near earth asteroids our data show no evidence of an albedo dependence on size however the mean albedo is lower than expected for young fresh s type surfaces suggesting that space weathering can darken main belt asteroid surfaces on very short timescales our data are also suggestive of a connection between surface roughness and albedo which may reflect rejuvenation of weathered surfaces by impact gardening while the available data allow only estimates of lower limits for thermal inertia we find no evidence for the relatively high values of thermal inertia reported for some similarly sized near earth asteroids our results constitute the first observational confirmation of the legitimacy of assumptions made in recent modeling of the formation of the karin cluster via a single catastrophic collision 5 8 0 2 myr ago

airborne sodium lidar measurements of gravity wave intrinsic parameters we describe a data analysis technique for determining gravity wave intrinsic parameters including wave propagation direction the technique involves measuring the altitude variations of the wave induced density perturbations of the atmospheric na layer this technique can be used with airborne lidars multiple ground based lidars and steerable lidars in this paper the technique is applied to airborne na lidar data obtained during a roundtrip flight from denver colorado to the pacific coast in november 1986 during the flight strong wave perturbations were observed in the na layer near the pacific coast over a horizontal distance of nearly 700 km the intrinsic horizontal wavelength of this wave was estimated to be about 85 km and the vertical wavelength was 4 1 km the intrinsic period was about 102 min and the propagation direction was almost due south