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1.
介绍了利用北京师范大学研制的ＩＲＡ－９３５型红外水汽测量仪对云南丽江高美古天文候选点及昆明凤凰山对比点上空垂直大气水汽积分含量Ｗ０的观测结果,给出了两地Ｗ０的日变化曲线及分布图,并对全年测量数据的统计结果作了分析和讨论 相似文献
2.
Vladimir V. Svetsov 《Planetary and Space Science》2005,53(12):1205-1220
Vertical impacts on the Earth of asteroids 500-3000 km in diameter at 15 km/s have been numerically modelled using the hydrodynamic SOVA code. This code has been modified for the spherical system of coordinates well suited for simulations of very large impacts when the entire Earth is involved in motion. The simulations include cratering process, upward motion of deep mantle layers, fall of ejecta on the Earth, escape of matter to space, and formation of rock vapour atmospheres. The calculations were made for the period preceding disappearance of rock vapour atmospheres caused by radiation several years after the largest impacts. For very large vertical impacts at 15 km/s, escaping masses proved to be negligibly small. Quantities of kinetic, internal, potential, and radiated away energies are obtained as functions of time and space. After the impacts, a global layer of condensed ejecta covers the whole of the Earth's surface and the ejecta energy is sufficient to vaporise an ocean 3 km deep. The mass of rock vapour atmosphere is 10-23% of the impactor mass. This atmosphere has a greater mass than the water atmosphere if impactor is 2000 km in diameter or larger. 相似文献
3.
云南天文台凤凰山大气含水量全年测量数据的统计分析 总被引：1，自引：0，他引：1
给出了云南天文台上空垂直大气含水量Ｗ０的全年测量数据的统计结果和精度分析。包括Ｗ０的逐日变化,Ｗ０分别在雨季和旱季的分布 相似文献
4.
We have developed a numerical model of the diurnal transport of water across the martian surface. The atmospheric boundary layer is modelled in terms of local radiative-convective processes. The radiative effects of ice fogs near the surface are included in the model. The diffusion of water in the ground is treated for the cases of adsorption and condensation.The model is applied to the diurnal variation of water vapour in the atmosphere as observed by Barker (1974a,b,; 1975). We can explain the morning rise in the amount of water vapour in terms of the evaporation of ground fogs. The evening decrease is compatible with our model if adsorption dominates in the soil. The average level of vapour concentration requires that the atmosphere above the boundary layer be relatively dry. The ground fogs persist until midmorning and should be observable. Some consequences of these conclusions are discussed. 相似文献
5.
6.
A large number of spectra measured by the planetary Fourier spectrometer aboard the European Mars Express mission have been studied to identify the average properties of methane in the Martian atmosphere. Using the line at 3018 cm−1, we have studied the seasonal, diurnal, and spatial variations of methane through the analysis of large averages of spectra (more than 1000 measurements). Methane mixing ratio has been obtained simultaneously with water vapour mixing ratio and water ice content, by best fitting (minimising the χ2) the computed averages with synthetic spectra. These spectra were computed for different values of the three parameters (methane and water vapour mixing ratio, and water ice optical depth).The methane mixing ratio shows a slow decrease from northern spring to southern summer with an average value of 14±5 ppbv (part per billion by volume) and it does not show a particular trend with latitude. The methane mixing ratio seems not to be uniform in longitude in the Martian atmosphere, as already reported by Formisano et al. [2004. Detection of methane in the atmosphere of Mars. Science 306, 1758-1761]. Two maxima are present at −40°E and +70°E longitude. In local time, the methane mixing ratio seems to follow the water vapour diurnal cycle. The most important point for future understanding is, however, that there are special orbits in which methane mixing ratio has a very high value. 相似文献
7.
Hugh R. A.Jones YakivPavlenko SerenaViti JonathanTennyson 《Monthly notices of the Royal Astronomical Society》2002,330(3):675-684
M-star spectra, at wavelengths beyond 1.35 μm, are dominated by water vapour, yet terrestrial water vapour makes it notoriously difficult to obtain accurate measurement from ground-based observations. We have used the short-wavelength spectrometer on the Infrared Space Observatory at four wavelength settings to cover the 2.5–3.0 μm region for a range of M stars. The observations show a good match with previous ground-based observations and with synthetic spectra based on the Partridge & Schwenke line list, although not with the SCAN line list. We have used a least-squared minimization technique to systematically find best-fitting parameters for the sample of stars. The temperatures that we find indicate a relatively hot temperature scale for M dwarfs. We consider that this could be a consequence of problems with the Partridge & Schwenke line list which leads to synthetic spectra predicting water bands that are too strong for a given temperature. Such problems need to be solved in the next generation of water vapour line lists, which will extend the calculation of water vapour to higher energy levels with the good convergence necessary for reliable modelling of hot water vapour. Then water bands can assume their natural role as the primary tool for the spectroscopic analysis of M stars. 相似文献
8.
Hugh R. A. Jones Yakiv Pavlenko Serena Viti R. J. Barber Larisa A. Yakovina David Pinfield Jonathan Tennyson 《Monthly notices of the Royal Astronomical Society》2005,358(1):105-112
We compare high-resolution infrared observations of the CO 2–0 bands in the 2.297–2.310 μm region of M dwarfs and one L dwarf with theoretical expectations. We find a good match between the observational and synthetic spectra throughout the 2000–3500 K temperature regime investigated. None the less, for the 2500–3500 K temperature range, the temperatures that we derive from synthetic spectral fits are higher than expected from more empirical methods by several hundred kelvin. In order to reconcile our findings with the empirical temperature scale, it is necessary to invoke warming of the model atmosphere used to construct the synthetic spectra. We consider that the most likely reason for the back-warming is missing high-temperature opacity due to water vapour. We compare the water vapour opacity of the Partridge–Schwenke line list used for the model atmosphere with the output from a preliminary calculation by Barber & Tennyson. While the Partridge–Schwenke line list is a reasonable spectroscopic match for the new line list at 2000 K, by 4000 K it is missing around 25 per cent of the water vapour opacity. We thus consider that the offset between empirical and synthetic temperature scales is explained by the lack of hot water vapour used for computation of the synthetic spectra. For our coolest objects with temperatures below 2500 K, we find best fits when using synthetic spectra which include dust emission. Our spectra also allow us to constrain the rotational velocities of our sources, and these velocities are consistent with the broad trend of rotational velocities increasing from M to L. 相似文献
9.
We have independently investigated water masers associated with the star-forming region W3 IRS5 with the VLBA. Imai et al., found that the maser 3-D motions exhibit outflows, which likely originate from two of the hyper-compact HII regions in this source. Sarma et al., have detected the Zeeman effect in water masers toward W3 IRS5 and measured line-of-sight magnetic field strengths of between 14 and 42 mG. The directions of maser linear polarization are well aligned in the whole maser region and perpendicular to the estimated magnetic field. These polarimetric results are consistent with an hourglass model of the magnetic field in W3 IRS5. Imai et al., also have analyzed the microstructures found in the individual maser features (1AU), which exhibit the fractal fashion and express turbulence on very small scales. Together, we have demonstrated that observations of water masers enable us to comprehensively enhance our understanding of the early stages of the formation of massive stars in clusters. 相似文献
10.
Michael C. Isherwood 《Planetary and Space Science》1977,25(1):45-51
A positive correlation is reported between sodium nightglow intensity and radio wave absorption of the previous midday for the period October 1970–March 1971. For the same period a weak correlation, at best, exists for the green line (5577 Å) nightglow and absorption. The correlations are briefly discussed and water vapour is suggested as a possible link between the sodium nightglow intensity and radio wave absorption for the October–March period. 相似文献
11.
This paper reports on mapping of water frost and ice on Mars, in the range of latitudes between 30°S and 30°N. The study has been carried out by analysing 2485 orbits acquired during almost one martian year by the Mars Express/OMEGA imaging spectrometer. Water frost/ice is identified by the presence of ∼1.5 μm, ∼2 μm and ∼3.0 μm absorptions. Although the orbits analysed in this study cover all seasons, water frost/ice is observed only near the aphelion seasons, at Ls = 19° and at Ls = 98-150°. Water frost/ice is detected mainly on the southern hemisphere between 15°S and 30°S latitude while it has not been identified within 15°S-15°N. In the northern hemisphere, the water frost/ice detection is complicated by the presence of clouds. Usually, water frost/ice is found in shadowed areas, while in few cases it is exposed to the sunlight. This indicates a clear relationship with the local illumination conditions on the slopes which favour the water frost/ice deposition on the surface when the temperatures are very low. OMEGA observations span from 10 to 17 LT and the frost/ice is detected mainly between 15 and 16 LT, with practically no detection before 13 LT. We think this is due to the fact that the 10-12 LT observations occur at large distances and it is not a local time effect. A thermal model is used to determine the deposition conditions on the sloped surfaces where water frost/ice has been found. There, daily atmospheric saturation does not occur on pole facing 10-25° slopes with current water vapour abundances but only by assuming values greater than 40 pr μm. Moreover, the water frost/ice is not detected during the northern winter, even if the thermal model foresees daily saturation on 25° slopes. 相似文献
12.
Konrad J. Kossacki Wojciech J. Markiewicz Yuri Skorov Norbert. I. Kmle 《Planetary and Space Science》1999,47(12):1521-1530
In papers dealing with evolution of cometary nuclei it is commonly assumed that the coefficients of sublimation s and condensation c of vapour are both equal to one. The experimental investigation of ice samples under simulated cometary-like conditions (Kossacki, K.J., Kömle, N.I., Leliwa-Kopysty
ski, J., Kargl, G., 1997. Thermal and structural evolution of cometary subsurface layer: selfconsistent model and experimental verification. Icarus 128, 127–144) suggests, however, that the sublimation flux calculated with the Hertz–Knudsen formula and the above assumption is nearly an order of magnitude too high. This may imply that actual values of s for the ice/dust sample used in these experiments are of the order of 0.1. A similar conclusion can be drawn for c from the results of various experiments concerning growth of ice crystals from the vapour phase and their sublimation (Lamb, D., Scott, W.D., 1972. Linear growth rates of ice crystals grown from the vapor phase. Journal of Crystal Growth 12, 21–31; Beckmann, W., Lacmann, R., 1982. Interface kinetics of growth and evaporation of ice II. Journal of Crystal Growth 58, 433–442; Sei, T., Gonda, T., 1989. The growth mechanism and the habit change of ice crystals growing from the vapour phase. Journal of Crystal Growth 94, 697–707). The exact values of both of these coefficients depend on various parameters such as temperature, concentration of surface impurities and deviation of the vapour pressure from that of the phase equilibrium. In this work the temperature dependence of the sublimation and condensation coefficients is discussed and an appropriate formula is proposed to fit the experimental results. This new formulation is then used to analyse the implications for the thermal conductivity of a porous cometary-like ice and the rate of vapour flux from a cometary nucleus. 相似文献
13.
Wu Yue-fang Shi Jian-rong Wang Jun-zhi Jiang Dong-rong Huang Xin-yong 《Chinese Astronomy and Astrophysics》1999,23(4):111-462
Using the 25-m telescope of Shanghai Observatory, Joint Radio Astronomy Laboratory, 19 known maser sources and 20 candidates in H II regions were surveyed for water vapour maser emission at 22.2 GHz. 21 sources were detected, of which two are for the first time. Combining with some previous data, the time variations in the flux and velocity are obtained and discussed. Time variation in the peak flux density is common and is of two types, a change in the intensity of the same peak, and a swapping-over of two peaks. The corresponding IRAS sources were identified and the relation between the maser emission and the infrared parameters discussed. It is shown that maser production rate is more sensitive to the infrared flux intensity than the infrared colour distribution. 相似文献
14.
L. Colangeli J.J. Lopez-Moreno P. Nørnberg V. Della Corte F. Esposito E. Mazzotta Epifani J. Merrison C. Molfese P. Palumbo J.F. Rodriguez-Gomez A. Rotundi G. Visconti J.C. Zarnecki 《Planetary and Space Science》2009,57(8-9):1043-1049
Dust and water vapour are fundamental components of the Martian atmosphere. In view of tracing the past environmental conditions on Mars, that possibly favoured the appearing of life forms, it is important to study the present climate and its evolution. Here dust and water vapour have (and have had) strong influence. Of major scientific interest is the quantity and physical, chemical and electrical properties of dust and the abundance of water vapour dispersed in the atmosphere and their exchange with the surface. Moreover, in view of the exploration of the planet with automated systems and in the future by manned missions, it is of primary importance to analyse the hazards linked to these environmental factors. The Martian Environmental Dust Systematic Analyser (MEDUSA) experiment, included in the scientific payload of the ESA ExoMars mission, accommodates a complement of sensors, based on optical detection and cumulative mass deposition, that aims to study dust and water vapour in the lower Martian atmosphere. The goals are to study, for the first time, in-situ and quantitatively, physical properties of the airborne dust, including the cumulative dust mass flux, the dust deposition rate, the physical and electrification properties, the size distribution of sampled particles and the atmospheric water vapour abundance versus time. 相似文献
15.
J. Cernicharo 《Astrophysics and Space Science》1998,263(1-4):175-192
I present some of the results we have obtained with the four instruments on board of the ISO satellite. The determination
of water vapour abundance, the study of star forming regions and the determination of the physical and chemical conditions
in evolved stars are discussed. The implication of these results for future space-based observatories like FIRST and large
ground-based infrared telescopes are analyzed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
16.
Surface soil moisture parameterization of the VIC-2L model: Evaluation and modification 总被引：9，自引：0，他引：9
HAPEX-MOBILHY data, consisting of one year of hourly atmospheric forcing data at Caumont (SAMER No. 3, 43.68°N, 0.1°W) were used repeatedly to run the two-layer Variable Infiltration Capacity (VIC-2L) land-surface scheme until the model reached equilibrium in its water and energy balance. The equilibrium results are compared with one year of weekly soil moisture measurements at different depths, the estimated latent heat fluxes for 35 days of the intensive observation period (IOP), and the accumulated evaporation, runoff and drainage for the entire soya crop season. The latent heat flux comparisons show that VIC-2L tends to underestimate the evaporation due to the low soil moisture in its upper layer. The soil moisture comparison shows that the total soil water content is well simulated in general, but the soil water content in the top 0.5 m is underestimated, especially in May and June. These comparisons suggest that the lack of a mechanism for moving moisture from the lower to the upper soil layer in VIC-2L is the main cause for model error in the HAPEX-MOBILHY application. A modified version of VIC-2L, which has a new feature that allows diffusion of moisture between soil layers, and a 0.1 m thin layer on top of the previous upper layer, is described. In addition, the leaf area index (LAI) and the fraction vegetation cover are allowed to vary at each time step in a manner consistent with the rest PILPS-RICE Workshop, rather than being seasonally fixed. With these modifications, the VIC-2L simulations are re-evaluated. These changes are shown to resolve most of the structural deficiencies in the original version of the model. The sensitivity analysis of the new version of the model to the choices of soil depths and root distribution show that the evapotranspiration and soil moisture at the model equilibrium state are more sensitive to the root distribution than to the soil depth. 相似文献
17.
18.
G.V. Groves 《Planetary and Space Science》1983,31(1):67-71
The global mean vertical energy flux of the (1,1,1) mode of atmospheric oscillation is evaluated at 80 km altitude by classical tidal theory for mean January, April, July and October conditions using revised profiles of water vapour and ozone heating. Fluxes calculated for January and July are lower than those for April and October due to seasonal changes in water vapour, solar declination and Sun-Earth distance. Flux values obtained are compared with a previously stated requirement for maintaining the residual thermosphere and are adequate unless damping, which is ignored in the present calculations, introduces a factor of more than an order of 10 in magnitude. The relative changes of flux between the above four months are noted to be similar in form to the semi-annual variation of thermospheric air densities. 相似文献
19.
Diedrich T.F. Möhlmann 《Icarus》2010,207(1):140-1033
It is investigated whether conditions for melting can be temporarily created in the upper sub-surface parts of snow/ice-packs on Mars at subzero surface temperatures by means of the solid-state greenhouse effect, as occurs in snow- and ice-covered regions on Earth. The conditions for this possible temporary melting are quantitatively described for bolometric albedo values A = 0.8 and A = 0.2, and with model parameters typical for the thermo-physical conditions at snow/ice sites on the surface of present Mars. It is demonstrated by numerical modelling that there are several sets of parameters which will lead to development of layers of liquid water just below the top surface of snow- and ice-packs on Mars. This at least partial liquefaction occurs repetitively (e.g. diurnally, seasonally), and can in some cases lead to liquid water persisting through the night-time in the summer season. This liquid water can form in sufficient amounts to be relevant for macroscopic physical (rheology, erosion), for chemical, and eventually also for biological processes. The creation of temporary pockets of sub-surface water by this effect requires pre-existing snow or ice cover, and thus is more likely to take place at high latitudes, since the present deposits of snow/ice can mainly be found there. Possible rheologic and related erosion consequences of the appearance of liquid sub-surface water in martian snow/ice-packs are discussed in view of current observations of recent rheologic processes. 相似文献
20.
Water-ice and dust optical depths in Mars’ north polar region are mapped as function of season, latitude and longitude, and their characteristics and variability on a geographic, seasonal, and interannual basis are discussed. We use water-ice and dust optical depth data provided by the Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES), covering nearly three northern spring and summer periods. We find that interannual variability exists in both the water ice and dust behavior, although there are trends that repeat year to year as well. The optical thickness of the north polar hood (NPH) exhibits interannually varying longitudinal structure, both during springtime recession and late-summer onset. We define the characteristics associated with the transition to and from the NPH and find that the disappearance occurs near Ls=75° and the reappearance near Ls=160-165°. We find that the late spring to early summer time frame is characterized by very low water-ice optical depths and enhanced dust activity, with a preference for lower water-ice and higher dust optical depths in the 0-90°W quadrant. We see possible evidence for stationary wavenumber 2 systems in a few of the maps examined. 相似文献