首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 15 毫秒
1.
The lidar measurements at Verhnetulomski observatory (68.6°N, 31.8°E) at Kola peninsula detected a considerable increase of stratospheric aerosol concentration after the solar proton event of GLE (ground level event) type on the 16/02/84. This increase was located at precisely the same altitude range where the energetic solar protons lost their energy in the atmosphere. The aerosol layer formed precipitated quickly (1–2 km per day) during 18, 19, and 20 February 1984, and the increase of R(H) (backscattering ratio) at 17 km altitude reached 40% on 20/02/84. We present the model calculation of CN (condensation nuclei) altitude distribution on the basis of an ion-nucleation mechanism, taking into account the experimental energy distribution of incident solar protons. The meteorological situation during the event was also investigated.deceased  相似文献   

2.
The present study reports long-term variabilities and trends in the middle atmospheric temperature (March 1998–2008) derived from Rayleigh backscattered signals received by the Nd:YAG lidar system at Gadanki (13.5°N, 79.2°E). The monthly mean temperature compositely averaged for the years 1998–2008 shows maximum temperature of 270 K in the months of March–April and September at altitudes between 45 and 55 km. The altitude profile of trend coefficients estimated from the 10 years of temperature observations using regression analysis shows that there exists cooling at the rate with 1σ uncertainty of 0.12±0.1 K/year in the lower stratospheric altitudes (35–42 km) and 0.2±0.08 K/year at altitudes near 55–60 km. The trend is nearly zero (no significant cooling or warming) at altitudes 40–55 km. The regression analysis reveals the significant ENSO response in the lower stratosphere (1 K/SOI) and also in mesosphere (0.6 K/SOI). The solar cycle response shows negative maxima of 1.5 K/100F10.7 units at altitudes 36 km, 41 km and 1 K/100F10.7 units at 57 km. The response is positive at mesospheric altitude near 67 km (1.3 K/100F10.7 units). The amplitudes and phases of semiannual, annual and quasi-biennial oscillations are estimated using least squares method. The semiannual oscillation shows larger amplitudes at altitudes near 35, 45, 62 and 74 km whereas the annual oscillation peaks at 70 km. The quasi-biennial oscillations show larger amplitudes below 35 km and above 70 km. The phase profiles of semiannual and annual oscillations show downward propagation.  相似文献   

3.
Layers of stratospheric aerosol with optical thicknesses as small as 10–4 cause noticeable perturbations in the monochromatic logarithmic brightness gradient,G, and the color ratio,C, of the twilight sky. Modeling of the twilight's radiant properties shows that definite single-valued relationships exist between maxima inC or minima inG and optical thickness, , physical thickness h, and mean altitude, , of stratospheric layers. It is therefore possible to determine , h and and monitor their variations by performing either single wavelength measurements ofG or two-wavelength spectrophotometric measurements ofC. The presence of haze in the lower troposphere and the occurrence of multiple scattering both have relatively minor influences on the recovery of the stratospheric dust properties, provided that 10< <30 km.Formal mathematical inversions of the single-scattering twilight equations are possible in principle, but difficult in practice because of non-linearities. Inversions incorporating an iterative linearization process with constrained smoothing, successfully recovered the features of the haze layer, but tended to oversmooth the vertical profile and underestimate the mean altitude of the haze layer.  相似文献   

4.
We report observations of a noctilucent cloud (NLC) over central Alaska by a ground-based lidar and camera on the night of 9–10 August 2005. The lidar at Poker Flat Research Range (PFRR), Chatanika (65°N, 147°W) measured a maximum integrated backscatter coefficient of 2.4×10?6 sr?1 with a peak backscatter coefficient of 2.6×10?9 m?1 sr?1 corresponding to an aerosol backscatter ratio of 120 at an altitude of 82.1 km. The camera at Donnelly Dome, 168 km southeast of PFRR, recorded an extensive NLC display across the sky with distinct filamentary features corresponding to wave structures measured by the lidar. The occurrence of the maximum integrated backscatter coefficient corresponded to the passage of a bright cloud band to the southwest over PFRR. The camera observations indicate that the cloud band had a horizontal width of 50 km and a length of 150 km. The horizontal scale of the cloud band was confirmed by medium-frequency radar wind measurements that reported mesopause region winds of 30 m/s to the southwest during the period when the cloud band passed over PFRR. Comparison of these measurements with current NLC microphysical models suggests a lower bound on the water vapor mixing ratio at 83 km of 7–9 ppmv and a cloud ice mass of 1.5–1.8×103 kg. Satellite measurements show that this NLC display occurred during a burst of cloud activity that began on 5 August and lasted for 10 days. This cloud appeared 10 days after a launch of the space shuttle. We discuss the appearance of NLCs in August over several years at this lower polar latitude site in terms of planetary wave activity and space shuttle launches.  相似文献   

5.
Pyroclastic flow emplacement is strongly influenced by eruption column height. A surface along which kinetic energy is zero theoretically connects the loci of eruption column collapse with all coeval ignimbrite termini. This surface is reconstructed as a two-dimensional energy line for the 1912 Katmai pyroclastic flow in the Valley of Ten Thousand Smokes from mapped flow termini and the runup of the ignimbrite onto obstructions and through passes. Extrapolation of the energy line to the vicinity of the source vent at Novarupta suggests the eruption column which generated the ignimbrite eruption was approximately 425 m high. The 1912 pyroclastic flow travelled about 25 km downvalley. Empirical velocity data calculated from runup elevations and surveyed centrifugal superelevations indicate initial velocities near Novarupta were greater than 79–88 m s–1. The flow progressively decelerated and was travelling only 2–8 m s–1 when it crossed a moraine 16 km downvalley. The constant slope of the energy line away from Novarupta suggests the flow was systematically slowed by internal and basal friction. Using a simple physical model to calculate flow velocities and a constant kinetic friction coefficient (Heim coefficient) of 0.04 derived from the reconstructed energy line, the flow is estimated to have decelerated at an average rate of –0.16 m s–2 and to have taken approximately 9.5 minutes to travel 25 km down the Valley of Ten Thousand Smokes. The shear strength of the flowing ignimbrite at the moraine was approximately 0.5 kPa, and its Bingham viscosity when it crossed the moraine was 3.5 × 103 P. If the flow was Newtonian, its viscosity was 4.2 × 103 P. Reynolds and Froude numbers at the moraine were only 41–62 and 0.84–1.04, respectively, indicating laminar, subcritical flow.  相似文献   

6.
Summary Ozone observations made during 1964 and 1965 at nine Mediterranean, central and southeast European stations (latitudes 38–52°N, longitudes 9–23°E) reveal patterns of seasonal and shorter time-variations in total ozone as well as in vertical ozone distribution. During the winter-spring season, a significant increase (20%) of ozone occurs essentially simultaneously with the spring stratospheric warming, and is noticed at all stations.—Autocorrelation coefficients show that the total ozone on any day is strongly related to the total ozone of the preceding four days in summer or one or two days in winter-spring or autumn. Changes of total ozone in southeast Europe correlate closely with those in Mediterranean Europe, and less closely with those from north central Europe.—Power spectrum analysis detects the dependence of ozone changes on processes with periods longer than 6–8 days, and indicates a significant oscillation with a period of 14–15 days, perhaps a result of the direct influence of lower stratospheric circumhemispheric circulation. — Reliable vertical ozone soundings were not available from all stations. The mean vertical profiles at Arosa, Switzerland (47°N) and Belsk, Poland (51°) are very similar. More than 60% of the variability of the total ozone is contributed by changes in ozone concentration between 10 and 24 km; less than 10% is due to variations above 33 km. Changes in ozone partial pressure at different altitudes, and relationships of those changes to total ozone, indicates that a mean vertical ozone distribution may be described adequately by considering the ozone changes in four layers: a) the troposphere, b) the lower stratosphere up to 24 km, c) a transition layer from 24 km to a variable upper border at 33–37 km, and d) the layer above 33–37 km.Part of this paper was presented at the Ozone Seminar in Potsdam, Germany, 27 September 1966.  相似文献   

7.
It could be shown by measurements of the air conductivity and using a mean profile for the ionization rate that experimental and theoretical values of the recombination rate of small ions based on a three body recombination process (Thomson) are in very good agreement up to 20 km altitude. The divergency of the experimental and theoretical curves above 20 km can be interpreted by assuming that there exists in this altitude region a crossover from the three body recombination to a two body recombination process. The value of the recombination coefficient is about 4·10–7 cm3 s–1 in 25 km altitude, compared with 1.4·10–6 cm3 s–1 at ground level. Furtheron it was possible for the first time to get some experimental data of attachment coefficients up to 13 km from simultaneous measurements of the air conductivity and Aitken nuclei concentration. These values are in good agreement with those obtained by theoretical considerations.  相似文献   

8.
Eighteen digital AVHRR (advanced very high resolution radiometer) data sets from NOAA-6 and NOAA-9 polar-orbiting satellites recorded between 27 March and 7 April 1986 depict the eruptive activity of Augustine volcano, located 280 km SW of Anchorage, Alaska. The synoptic view (resolution of either 1.1 or 4.4 km), frequent coverage (often twice a day), and multispectral coverage (five bands: 0.58–0.68; 0.72–1.1; 3.55–3.93; 10.5–11.3; and 11.5–12.5 m) makes the AVHRR broadly applicable to analyzing explosive eruption clouds. The small scale of the Augustine activity (column heights of 2–13 km and eruption rates of 2x106–8x107 metric tonnes/day) facilitated intensive multispectral study because the plumes generally covered areas within the 550x550 km area of one easily manipulated image field. Hourly ground weather data and twice-daily radiosonde measurements from stations surrounding the volcano plus numerous volcanological observations were made throughout the eruption, providing important ground truth with which to calibrate the satellite data. The total erupted volume is estimated to be at least 0.102 km3. The pattern of changing eruption rates determined by satellite observations generally correlate with more detailed estimates of explosion magnitudes. Multispectral processing techniques were used to distinguish eruption clouds from meteorological clouds. Variable weather during the Augustine eruption offered an opportunity to test various trial algorithms. A ratio between thermal IR channels four and five, served to delineate the ashbearing eruption plumes from ordinary clouds. Future work is needed to determine whether the successful multispectral discrimination is caused by wavelength-dependent variable emission of silicate ash or reflects a spectral role of sulfuric acid aerosol in the plume.  相似文献   

9.
We report on the development and current capabilities of the ALOMAR Rayleigh/Mie/Raman lidar. This instrument is one of the core instruments of the international ALOMAR facility, located near Andenes in Norway at 69°N and 16°E. The major task of the instrument is to perform advanced studies of the Arctic middle atmosphere over altitudes between about 15 to 90 km on a climatological basis. These studies address questions about the thermal structure of the Arctic middle atmosphere, the dynamical processes acting therein, and of aerosols in the form of stratospheric background aerosol, polar stratospheric clouds, noctilucent clouds, and injected aerosols of volcanic or anthropogenic origin. Furthermore, the lidar is meant to work together with other remote sensing instruments, both ground- and satellite-based, and with balloon- and rocket-borne instruments performing in situ observations. The instrument is basically a twin lidar, using two independent power lasers and two tiltable receiving telescopes. The power lasers are Nd:YAG lasers emitting at wavelengths 1064, 532, and 355 nm and producing 30 pulses per second each. The power lasers are highly stabilized in both their wavelengths and the directions of their laser beams. The laser beams are emitted into the atmosphere fully coaxial with the line-of-sight of the receiving telescopes. The latter use primary mirrors of 1.8 m diameter and are tiltable within 30° off zenith. Their fields-of-view have 180 rad angular diameter. Spectral separation, filtering, and detection of the received photons are made on an optical bench which carries, among a multitude of other optical components, three double Fabry-Perot interferometers (two for 532 and one for 355 nm) and one single Fabry-Perot interferometer (for 1064 nm). A number of separate detector channels also allow registration of photons which are produced by rotational-vibrational and rotational Raman scatter on N2 and N2+O2 molecules, respectively. Currently, up to 36 detector channels simultaneously record the photons collected by the telescopes. The internal and external instrument operations are automated so that this very complex instrument can be operated by a single engineer. Currently the lidar is heavily used for measurements of temperature profiles, of cloud particle properties such as their altitude, particle densities and size distributions, and of stratospheric winds. Due to its very effective spectral and spatial filtering, the lidar has unique capabilities to work in full sunlight. Under these conditions it can measure temperatures up to 65 km altitude and determine particle size distributions of overhead noctilucent clouds. Due to its very high mechanical and optical stability, it can also employed efficiently under marginal weather conditions when data on the middle atmosphere can be collected only through small breaks in the tropospheric cloud layers.  相似文献   

10.
The mechanisms contributing to the attenuation of earthquake ground motion in the distance range of 10 to 200 km are studied with the aid of laboratory data, coda wavesRg attenuation, strong motion attenuation measurements in the northeast United States and Canada, and theoretical models. The frequency range 1–10 Hz has been studied. The relative contributions to attenuation of anelasticity of crustal rocks (constantQ), fluid flow and scattering are evaluated. Scattering is found to be strong with an albedoB 0=0.8–0.9 and a scattering extinction length of 17–32 km. The albedo is defined as the ratio of the total extinction length to the scattering extinction length. TheRg results indicate thatQ increases with depth in the upper kilometer or two of the crust, at least in New England. CodaQ appears to be equivalent to intrinsic (anelastic)Q and indicates that thisQ increases with frequency asQ=Q o f n , wheren is in the range of 0.2–0.9. The intrinsic attenuation in the crust can be explained by a high constantQ (500Q o2000) and a frequency dependent mechanism most likely due to fluid effects in rocks and cracks. A fluid-flow attenuation model gives a frequency dependence (QQ o f 0.5) similar to those determined from the analysis of coda waves of regional seismograms.Q is low near the surface and high in the body of the crust.  相似文献   

11.
There are differences between existing models of solar EUV with < 1050 Å and between laboratory measurements of the O+ + N2 – reaction rate coefficient, both parameters being crucial for the F2-region modeling. Therefore, indirect aeronomic estimates of these parameters may be useful for qualifying the existing EUV models and the laboratory measured O+ + N2 – rate coefficient. A modified self-consistent method for daytime F2-region modeling developed by Mikhailov and Schlegel was applied to EISCAT observations (32 quiet summer and equinoctial days) to estimate the set of main aeronomic parameters. Three laboratory measured temperature dependencies for the O+ + N2 – rate coefficient were used in our calculations to find self-consistent factors both for this rate coefficient and for the solar EUV flux model from Nusinov. Independent of the rate coefficient used, the calculated values group around the temperature dependence recently measured by Hierl et al. in the 850–1400 K temperature range. Therefore, this rate coefficient may be considered as the most preferable and is recommended for aeronomic calculations. The calculated EUV flux shows a somewhat steeper dependence on solar activity than both, the Nusinov and the EUVAC models predict. In practice both EUV models may be recommended for the F2-region electron density calculations with the total EUV flux shifted by ±25% for the EUVAC and Nusinov models, correspondingly.  相似文献   

12.
Augustine, an island volcano in Lower Cook Inlet, southern Alaska, erupted in January, 1976, after 12 years of dormancy. By April, when the eruptions ended, a new lava dome had been extruded into the summit crater and about 0.1 km3 of pyroclastics had been deposited on the island, mainly as pyroclastic debris avalanches and pumice flows. The ventclearing phase in January was highly explosive and we have been able to document 13 major vulcanian eruptions.The timing, thermal energy, mass loading of fine particles and the horizontal dispersion of these eruption clouds were determined from radar measurements of cloud height, reports of pilots flying in plumes, satellite photography, seismic records and infrasonic detection of air waves. A lower estimate of the mass of fine (r < 68 μm) particles injected into the troposphere from the 13 main eruptions in January is 5.5–18 × 1012 g. The corresponding mass loading of fine particles within individual eruption clouds is 0.3–1 g m−3. We calculated thermal energies of 4 × 1014 to 35 × 1014 J for individual eruptions by applying convective plume rise theory to observed cloud heights and seismically determined eruption durations. This energy range compares favorably with the 4–16 × 1014 J of thermal energy, calculated from the cooling of juvenile material contained in a typical eruption cloud.The vulcanian eruption clouds stayed intact for at least 700 km downwind. Satellite images in both visible and infrared wavebands, showing the Gulf of Alaska just after sunrise on January 23, reveal a series of puffs strung out downwind from the volcano, 20–30 km in diameter and with their tops at altitudes of about 8 km, overlying a continuous plume at altitude 4 km. Each puff corresponded to a seismically and infrasonically timed eruption. A substantial portion of the material injected into the atmosphere between January 22 and 25 was rapidly transported by the subpolar jet stream through southwestern Canada and the western United States, then northeast across the States into the Atlantic. The clouds were observed passing over Tucson, Arizona, on January 25 at an elevation of 7 km.Several of the eruptions penetrated into the stratosphere. Sun photometer measurements, taken at Mauna Loa, Hawaii, six weeks after the eruption, showed an increased stratospheric optical thickness of 0.01 (wavelength 0.5 μm), which decayed in about 5 months. The maximum column mass loading of the veil was 4–10 × 10−7 g cm−2. The mass of the veil, spread-ever a fourth of the earth's surface, is 10 to 100 times larger than can be accounted for by assuming that injected ash and converted sulfate particles from the 13 main Augustine eruptions are the only components contributing to the stratospheric turbidity observed at Mauna Loa.  相似文献   

13.
During 1990–2007, there were 894 lidar observations of nocturnal mesopause region temperatures over Fort Collins, Colorado. In an earlier analysis with data to April 1997, an unexpected episodic warming, peaking in 1993 with a maximum value over 10 K, was reported and attributed to the Mount Pinatubo eruption in June 1991. With all data, long-term temperature trends from a 7-parameter linear regression analysis including solar cycle effect and long-term trends leads to a cooling of as much as 6.8 K/decade at 100 km, consistent with some reported observations but larger than model predictions. Including the observed episodic warming response in an 11-parameter nonlinear regression analysis reduces the maximum long-term cooling trends to 1.5 K/decade at 91 km, with magnitude and altitude dependences consistent with the prediction of two models, Spectral Mesosphere/Lower Thermosphere Model (SMLTM) and Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA). In addition, the mid-latitude middle-atmospheric response to solar flux variability in Thermosphere–Ionosphere-Energetics and Dynamics (TIMED)/Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) temperatures is presented.  相似文献   

14.
The HOBr molecule is a potential reservoir of Br compounds in the atmosphere. In this work, the UV-visible spectrum of HOBr was measured over the range 242–400 nm. Its absorption consists of two maxima at 280 nm (max=2.7±0.4×10-19 cm2 molecules−1) and 355 nm (max=7.0±1.1×10-20 cm2 molecules−1), respectively, where the error is ±1. Atmospheric photolysis lifetime calculations for HOBr in the lower stratosphere have been made using the PHOTOGT model. The results show a strong dependence on the solar zenith angle (SZA) implying a longer lifetime at high latitudes and a relatively short lifetime at low latitudes for example 714 s (albedo of 25%, SZA of 20° and an altitude of 17 km), and 3226 s (albedo of 25%, SZA of 88° and an altitude of 17 km). The UV-visible absorption spectrum of Br2O, which is an intermediate in the preparation, used in this study and is together with H2O in equilibrium with HOBr, was measured from 205 to 450 nm. The spectrum shows a maximum at 315 nm (max=2.3±0.3×10-18 cm2 molecules−1) with a shoulder at 355 nm. From the results of the atmospheric lifetime calculations for Br2O, it is clear that this molecule has a short stratospheric lifetime and is not likely to have a large daytime concentration, for example, 20 s (albedo of 25%, SZA of 20° and an altitude of 17 km), and 83 s (albedo and 25%, SZA of 88° and an altitude of 17 km).  相似文献   

15.
Stratospheric warming effects on the tropical mesospheric temperature field   总被引：1，自引：0，他引：1  
Temperature observations at 20–90 km height and 5–15°N during the winter of 1992–1993, 1993–1994 and 2003–2004, from the Wind Imaging Interferometer (WINDII) and Microwave Limb Sounder (MLS) experiments on the Upper Atmosphere Research Satellite (UARS) satellite and the Sounding the Atmosphere using Broadband Emission Radiometry (SABER) experiment on the Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics (TIMED) satellite are analyzed together with MF radar winds and UK Meteorological Office (UKMO) assimilated fields. Mesospheric cooling is observed at the time of stratospheric warming at the tropics correlative with stratospheric warming events at middle and high latitudes. Planetary waves m=1 with periods of 4–5, 6–8, 10 and 12–18 days are found to dominate the period. Westward 7- and 16-day waves at the tropics appear enhanced by stationary planetary waves during sudden stratospheric warming events.  相似文献   

16.
We propose a thermal model of the subducting Ionian microplate. The slab sinks in an isothermal mantle, and for the boundary conditions we take into account the relation between the maximum depth of seismicity and the thermal parameter Lth of the slab, which is a product of the age of the subducted lithosphere and the vertical component of the convergence rate. The surface heat-flux dataset of the Ionian Sea is reviewed, and a convective geotherm is calculated in its undeformed part for a surface heat flux of 42 mW m–2, an adiabatic gradient of 0.6 mK m–1, a mantle kinematic viscosity of 1017 m2 s–1 and an asthenosphere potential temperature of 1300°C. The calculated temperature-depth distribution compared to the mantle melting temperature indicates the decoupling limit between lithosphere and asthenosphere occurs at a depth of 105 km and a temperature of 1260°C. A 70–km thick mechanical boundary layer is found. By considering that the maximum depth of the seismic events within the slab is 600 km, a Lth of 4725 km is inferred. For a subduction rate equal to the spreading rate, the corresponding assimilation and cooling times of the microplate are about 7 and 90 Myr, respectively. The thermal model assumes that the mantle flow above the slab is parallel and equal to the subducting plate velocity of 6 cm yr–1, and ignores the heat conduction down the slab dip. The critical temperature, above which the subduced lithosphere cannot sustain the stress necessary to produce seismicity, is determined from the thermal conditions governing the rheology of the plate. The minimum potential temperature at the depth of the deepest earthquake in the slab is 730°C.  相似文献   

17.
Fernald前向积分法能否用于机载大气探测激光雷达气溶胶后向散射系数的反演一直是一个有争议的课题.本文利用青岛机载大气探测激光雷达实测数据、国外机载大气探测激光雷达实测数据和机载大气探测激光雷达模拟数据,对Fernald前向积分法应用于不同高度的机载大气探测激光雷达气溶胶后向散射系数反演的误差进行了定量分析,分析结果表明:飞机的飞行高度在3.5 km左右,标定值存在20%的误差时,离地面2 km的高度范围内反演得到的气溶胶后向散射系数的相对误差在12%以内,但在标定点附近相对误差可达20%;飞机飞行高度在7 km左右,当标定值存在100%的误差时,反演得到的气溶胶后向散射系数的相对误差大都在10%~15%之间,标定值存在400%的误差时,反演得到的气溶胶后向散射系数的相对误差大部分在15%~50%之间.本文从理论上对Fernald前向积分法应用于机载大气探测激光雷达气溶胶后向散射系数反演出现负值的原因进行了探讨.研究表明:Fernald前向积分法能够较准确地反演出中高空探测(4.5 km以上)机载大气探测激光雷达气溶胶后向散射系数,但应用于低空探测(4.5 km以下)机载大气探测激光雷达气溶胶后向散射系数反演时,反演误差较大甚至反演结果会出现负值.  相似文献   

18.
Radio waves undergo angular scattering when they propagate through a plasma with fluctuating density. We show how the angular scattering coefficient can be calculated as a function of the frequency spectrum of the local density fluctuations. In the Earths magnetosheath, the ISEE 1–2 propagation experiment measured the spectral power of the density fluctuations for periods in the range 300 to 1 s, which produce most of the scattering. The resultant local angular scattering coefficient can then be calculated for the first time with realistic density fluctuation spectra, which are neither Gaussian nor power laws. We present results on the variation of the local angular scattering coefficient during two crossings of the dayside magnetosheath, from the quasi-perpendicular bow shock to the magnetopause. For a radio wave at twice the local electron plasma frequency, the scattering coefficient in the major part of the magnetosheath is b(2fp) 0.5–4 × 10–9 rad2/m. The scattering coefficient is about ten times stronger in a thin sheet (0.1 to IRE) just downstream of the shock ramp, and close to the magnetopause.  相似文献   

19.
Lidar observations during 2007–2008 in Kamchatka revealed aerosol layers in the upper stratosphere at heights of 35–50 km and in the mesosphere at heights of 60–75 km. It is well known that forces of gas-kinetic nature, i.e., photophoretic forces, act on aerosol particles that absorb solar radiation and terrestrial IR radiation; these forces can counteract the gravitational force and even lead to the levitation of these particles at particular heights. The accumulation of particles at these heights may lead to the formation of aerosol layers. We calculated these forces for the conditions of lidar observations in Kamchatka. Aerosol layers were observed at heights where particle levitation can occur. Thus, the stratospheric and mesospheric aerosol layers, detected at heights of 30–50 and 60–75 km, respectively, may be due to the effect of the photophoretic force on aerosol particles.  相似文献   

20.
The atmospheric spectral transparency variations at 344 nm and 369 nm, averaged at eight Soviet stations between 69°N and 55°N, have been compared with sunspot numbers, or Wolf numbers (WN). The data were taken for the seasonal interval May-August during the period 1972 – 1989. Good negative correlations –0.76 and –0.82 have been found. The correlation coefficient between aerosol extinction at 344 nm and WN is equal to +0.75. Insignificant correlation is found for the transparency variations at 344 nm for stations situated to the south of latitude 50°. The best correlation with WN for both transparency and aerosol extinction at northern stations occurs for the shift of WN ahead of the optical parameters by 6 months. The connection of transparency with cosmic rays in Apatity is also examined. It displays a sign opposite to that for WN, smaller values of the correlation coefficient, and an improbable shift of transparency ahead of cosmic ray intensity. The relative changes of the transparency during a solar cycle can be evaluated at 10% in the ozone-free UVA region  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号