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1.
An altitude profile of the ozone concentration from 55 to 95 km was measured at sunset in January by simultaneous measurements of the 1.27 μm radiation and the solar UV radiation using rocket-borne radiometers at Uchinoura, Japan (31°N). The ozone profiles deduced by two different methods agree with each other at approximately 70 km. The profile was consistent with our previous results obtained at the same station in September, and with the sunset profile obtained at Wallops Island (38°N) during the WMO/FAA/NASA international ozone rocketsonde intercomparison. Our data show no seasonal variation of ozone in the 55 – 95 km region at Uchinoura.  相似文献   

2.
The influence of horizontal eddy diffusion on photochemical oscillations of minor gas constituents in the mesopause region of the Earth’s atmosphere is investigated. It is shown that, when the spectrum of oscillations contains a pronounced second subharmonic (nonlinear response of the photochemical system to diurnal variations of solar radiation), reaction-diffusion waves in the form of travelling fronts and pulses of the phase of two-day oscillations may be excited in this region of the atmosphere.  相似文献   

3.
The Langmuir-probe technique for measurement of electron concentration in the mesosphere is capable of excellent altitude resolution, of order 1 m. Measurements from nine rocket flights frequently show small-scale ionization structures in the altitude region 60–90 km. These are believed to be identical with regions of strong coherent backscatter seem by VHF radars at Jicamarca, Peru and Urbana, Illinois. They are believed to represent intermittent turbulence attributable to nonlinear interaction of waves in the mesosphere. Parameters of the turbulent regions are estimated.  相似文献   

4.
A model study of the solar eclipse induced variations in mesospheric ozone concentrations was undertaken. This study includes, in addition to the Chapman reactions, the chemistry involving hydrogen species (H, OH and HO2) which are found to be important in the destruction of odd oxygen in this altitude region. Coupled time dependent continuity equations are solved for the eclipse duration. The results from the present study are compared with earlier theoretical model and the experimental observations during the 16 February 1980 solar eclipse as well as the results obtained during earlier solar eclipses.  相似文献   

5.
A new and original stereo imaging method is introduced to measure the altitude of the OH nightglow layer and provide a 3D perspective map of the altitude of the layer centroid. Near-IR photographs of the OH layer are taken at two sites separated by a 645 km distance. Each photograph is processed in order to provide a satellite view of the layer. When superposed, the two views present a common diamond-shaped area. Pairs of matched points that correspond to a physical emissive point in the common area are identified in calculating a normalized cross-correlation coefficient (NCC). This method is suitable for obtaining 3D representations in the case of low-contrast objects. An observational campaign was conducted in July 2006 in Peru. The images were taken simultaneously at Cerro Cosmos (12°09′08.2″ S, 75°33′49.3″ W, altitude 4630 m) close to Huancayo and Cerro Verde Tellolo (16°33′17.6″ S, 71°39′59.4″ W, altitude 2272 m) close to Arequipa. 3D maps of the layer surface were retrieved and compared with pseudo-relief intensity maps of the same region. The mean altitude of the emission barycenter is located at 86.3 km on July 26. Comparable relief wavy features appear in the 3D and intensity maps. It is shown that the vertical amplitude of the wave system varies as exp (Δz/2H) within the altitude range Δz = 83.5–88.0 km, H being the scale height. The oscillatory kinetic energy at the altitude of the OH layer is comprised between 3 × 10−4 and 5.4 × 10−4 J/m3, which is 2–3 times smaller than the values derived from partial radio wave at 52°N latitude.  相似文献   

6.
Important observational manifestations of subvisible mesospheric dust are Polar Mesospheric Summer Echoes (PMSEs) which are produced by scattering from electron irregularities produced by dust charging. It has been observed that the PMSE strength can be artificially modified by using a ground-based ionospheric heating facility to perturb the electron irregularity source region that is believed to produce PMSE. Recently it has become evident that significant diagnostic information may be available about the dust layer from the temporal behavior of the electron irregularities during the heating process which modifies the background electron temperature. Particularly interesting and important periods of the temporal behavior are during the turn-on and turn-off of the radio wave heating. Most past theoretical models and experimental investigations have concentrated primarily on the later period. The objective here is to consider the temporal behavior and possibilities for diagnostic information available during the turn-on period of the radio wave. First, approximate analytical models are developed and compared to a more accurate full computational model as a reference. Then from the temporal behavior of the electron irregularities during the turn-on of the radio wave, the analytical models are used to obtain possible diagnostic information for various charged dust and background plasma quantities.  相似文献   

7.
Spores of Bacillus subtilis (TKJ 3412), cells of Deinococcus radiodurans R1 (wild type) and conidia of Aspergillus ochraceus (strain 3174) have been UV irradiated (254 nm) in the dry state (3% relative humidity, argon) or in aqueous suspension at room temperature, at −55°C to −70°C and at −165°C to −170°C. The following effects have been analyzed: decrease in viability, occurrence of DNA strand breaks (pulsed-field gel electrophoresis) and production of DNA-protein cross-links (membrane filter method). The loss in viability is usually more pronounced at around −70°C than at room temperature, but it is lowest around −170°C. The kind of prevailing DNA damage varies from organism to organism. The amount of UV induced DNA-protein cross-link products steadily decreases with the temperature and is lowest at −170°C. The decrease in highly polymeric DNA by double strand breaks follows no universal pattern. The observed hypersensitivity of the three very different species at −70°C can therefore not be simply explained on the basis of the number of DNA lesions analyzed in the course of this work. We suggest that also the changing state of cellular water below and above about −130°C significantly contributes to the change in photosensitivity.  相似文献   

8.
MST radar studies at low latitude stations have documented regions in the mesosphere from where enhanced echoes (Low Latitude Mesospheric Echoes (LMEs)) are observed. Such echoes cannot, in general, be explained by considering the dynamical aspects (such as turbulence, winds, waves, etc.) of the region alone. Mesospheric dust/aerosols can enhance the radar echoes considerably and dust is known to exist at all heights and latitudes of the mesosphere. This study investigates the presence of dusty plasma in the mesosphere through the heterogeneous ion-chemistry of the region.Dust of meteoric origin is incorporated in the conventional ion chemistry scheme and the equilibrium height profiles of charged and neutral dust densities corresponding to effective dust sizes (radii) of 1, 10 and 30 nm are computed for the equatorial quiet daytime conditions.The model derived dust density profiles show structures with respect to dust size, height and season that are indicative of the possible role of mesospheric dust in the production/enhancement mechanisms of the LMEs observed over the equatorial station at Gadanki (13.5°N, 79.2°E), India.  相似文献   

9.
Slit spectra and spectroheliograph observations were obtained during the fourth rocket flight of the High Resolution Telescope and Spectrograph (HRTS) on 7 March 1983. A curved slit 900 arc sec in length was placed at the solar limb on the western edge of the south polar coronal hole, giving both coronal hole and quiet region coverage. In addition, spectroheliograph images tuned to cover a passband around 1550 Å (primarily C IV at 105 K) were taken over an 8 × 15 arc min field. Simultaneous Hα images were obtained at Sac Peak Observatory. The C IV spectroheliograms show general spiked emission above the limb, and also several small loo- or prominence-like events. Slit spectra along the tops of several of these structures show tilted features which could be interpreted as rotational velocities of approximately 50 km s?1.  相似文献   

10.
A new convective gravity wave source spectrum parameterization has been implemented in the Whole Atmosphere Community Climate Model version 2 (WACCM2). This parameterization specifies the momentum flux phase speed spectrum of gravity waves in the Tropics based on the properties of underlying convection; Hence, this parameterization provides realistic global estimates of gravity wave activity. In this paper, we show the estimated gravity wave phase speed spectra in the Tropics from a WACCM2 simulation, at the source level and at 85 km. Spatial distribution of gravity wave activity at 85 km is also presented. Subsequently, we discuss the factors that are primarily responsible for the estimated differences in gravity wave distribution across phase speeds with latitude and asymmetries in direction of gravity wave propagation in the mesosphere. We also examine which of the model assumptions can lead to uncertainties in our estimates of mesospheric gravity wave activity and we discuss how these assumptions provide challenges for comparison with observations of gravity waves in the mesosphere.  相似文献   

11.
In the context of prebiotic chemistry in space, some of the outer planetary objects display H, C, N and O rich chemistry similar to the one in the biosphere of Earth. Of particular interest are Saturn's moon, Titan; Neptune's moon, Triton; and Pluto where extreme cold conditions prevail. Identifications of chemical species on these objects (surfaces and atmospheres) is essential to a better understanding of the radiation induced chemical reactions occurring thereon. There have been several ground based observations of these planetary objects in the infrared windows from 1 to 2.5 micrometers. Voyager also provided spectra in the thermal infrared (6 to 50 micrometers) region. Interpretation of these data require laboratory infrared spectra of relevant species under the temperature conditions appropriate to these objects. The results of some of these studies carried out in our laboratory and elsewhere and their impact on the analyses of the observed data will be summarized.  相似文献   

12.
Deoxynucleoside 5'-monophosphates were condensed by cyanamide or by l-ethyl-3-(3-dimethylaminopropyl) carbodiimide in the presence of ammonium chloride at 0 degree, 37 degrees or 60 degrees C through several cycles of evaporation to dryness with replenishment of all reactants at each cycle. We found that at 37 degrees or 60 degrees cyanamide gives distinctly more high molecular weight material than does carbodiimide. Indeed, the yield of condensed products for the cyanamide reaction (dimers and higher oligomers) was found to be between 60 percent and 80 percent. The molecular weight distribution of the product shifts to higher molecular weights as cycling continues at 37 degrees or 60 degrees for both condensing agents. The water soluble carbodiimide gives higher yields of low molecular weight product but much lower yields of the higher molecular weight products. At 0 degree yields of high molecular weight product were low for both condensing agents. Results of characterization of the products demonstrate the synthesis of oligodeoxynucleotides including tetramers, with 3'-5' phosphodiester linkages.  相似文献   

13.
The design and performance of SAMS, an infrared limb-scanning instrument for sounding the temperature and composition of the atmosphere from 15 to 150 km altitude, are reviewed. Some examples of preliminary results on temperature and water vapour and nitrous oxide abundance versus latitude and height are presented.  相似文献   

14.
An all-sky CCD imager capable of measuring wave structure in the airglow OH, O2 and OI (557.7 nm) emissions was operated in the equatorial region at São João do Cariri (Cariri), Brazil (7°S, 36°W), in collaboration with the Instituto Nacional de Pesquisas Espaciais (INPE). Occurrence of mesospheric bore events was studied using the data from September 2000 to September 2002. Sixty-four bore events were detected during the observation period. Most of the bores showed the complementary effects suggested by Dewan and Picard [E.M. Dewan, R.H. Picard, Mesospheric bores. Journal of Geophysical Research 103, 6295–6305, 1998], except in a few cases where the relative variations were inconsistent with this model.  相似文献   

15.
A sodium lidar, capable of measuring temperature in the 80–100 km region, has been in operation at São José dos Campos (23° S, 46 W) since March 2007. Good quality data have been obtained for late autumn, winter and spring, but weather conditions make it extremely difficult to make measurements from mid-November to mid- February. We find the temperature structure to be strongly modulated by tides and gravity waves, but average profiles typically show a primary mesopause height close to 100 km with temperatures around 180 K, and a tendency for a secondary minimum of about 185 K to occur close to 90 km. Vertical temperature gradients greater than 50 K/km are sometimes seen even on profiles averaged over several hours. The strongest gradients are always positive and are frequently associated with strong gradients in sodium concentration. On the other hand, we frequently see rapid changes in the temperature profile, suggesting that models and non-local temperature measurements, as made by satellite radiometers, for example, are of little use in applications such as the analysis of gravity wave propagation seen in airglow images.  相似文献   

16.
The response of mesosphere and lower thermosphere (MLT) temperature to energetic particle precipitation over the Earth’s polar regions is not uniform due to complex phenomena within the MLT environment. Nevertheless, the modification of MLT temperatures may require an event-based study to be better observed. This work examines the influence of precipitation, triggered by solar wind stream interfaces (SI) event from 2002 to 2007, on polar MLT temperature. We first test the relationship between the ionospheric absorption measured by the SANAE IV (South African National Antarctic Expedition IV) riometer and the layer of energetic particle precipitation from POES (Polar Orbiting Environmental Satellites). The combined particle measurements from POES 15, 16, 17 and 18 were obtained close in time to the pass of the SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) temperature retrieval. Here, a superposed epoch technique is described and implemented to obtain average temperature profiles during SI-triggered particle precipitation. The superposed epoch average shows no significant temperature decrease below 100 km prior to the onset of SI-triggered precipitation, whereas a clear superposed average temperature decrease is observed at 95 km after the SI impact. A case study of SI event also yields similar observations. Results indicate that cooling effects due to the production of mesospheric odd hydrogen might be major contributors to temperature decrease under compressed solar wind stream.  相似文献   

17.
Upper atmospheric CO above 24 km has been observed over Poker Flat (147°W, 65°N, altitude 0.61 km), Alaska using ground-based solar absorption infrared spectroscopy. This is the first reported detection of stratospheric–mesospheric CO using this method from the ground. The results clearly indicate that there is a seasonal variation of the CO profile with enhanced abundances in spring while remaining low from May onwards.The Poker Flat Research Range is one of the many measurement sites that constitute the Network for the Detection of Stratospheric Change (NDSC). The method used in this work, estimating the CO partial column abundances above the middle stratosphere, can be applied to spectra observed using FTIR spectrometry at many other NDSC sites. This suggests the availability of this established technique as a new method for CO measurements in the upper atmosphere.  相似文献   

18.
Earthly microorganisms might have contaminated Mars for millions of years by intellectual activities or natural transfer. Knowledge on the preservation of microorganisms may help our searching for life on outer planets, particularly Mars-contaminated earthly microorganisms at ancient time. Extreme dryness is one of the current Mars characteristics. However, a humid or watery Mars at earlier time was suggested by evidence accumulated in recent decades. It raises the question that whether water helps preservation of the microorganisms or not, particularly those with high possibility of interplanetary transfer like spores and Deinococci. In this study, we examined the effects of desiccation and high humidity on survival and DNA double strand breaks (DSB) of Escherichia coli, Deinococcus radiodurans and spores of Bacillus pumilus at 25, 4 and −70 °C. They exhibited different survival rates and DSB patterns under desiccation and high humidity. Higher survival and less DSB occurred at lower temperature. We suggest that some Mars-contaminated bacteria might have been viably preserved on cold Mars regions for long periods, regardless of water availability. It is more likely to find ancient spores than ancient Deinococci on Mars. In our search for preserved extraterrestrial life, priority should be given to the Mars Polar Regions.  相似文献   

19.
We summarize two years of Mesosphere Lower Thermosphere Photometer (MLTP) operation of mesospheric OH and O2 emission monitoring. The deduced mesospheric OH and O2 temperatures show large variability. Nightly temperature variations over Gadanki (13.5°N, 79.2°E) are dominated by the short period wave features, while tidal amplitudes are relatively small. Our measurements are the first to report a long period seasonal variation at two upper mesospheric altitudes simultaneously over the Indian sector. Our observations reveal the presence of a dominant semi-annual oscillation (∼6 months periodicity) together with a shorter period (∼2.5  months periodicity) oscillation in both OH and O2 data.  相似文献   

20.
Mesopause temperatures were derived from ground measurements of the near infrared OH1 spectrum. Preliminary data are presented. Seasonal variations at Wuppertal (51° N, 7° E) are well represented if the Cole and Kantor (1978) model [1] is raised by 10 K and shifted by about 18 days. Latitudinal variations from 68° N to 51° N are found much smaller than the model variations. During a stratospheric warming, mesopause and stratosphere temperatures were found to be in anticorrelation only if a substantial longitudinal shift is introduced.  相似文献   

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