Clear air turbulence: detection by infrared observations of water vapor

"Forward-looking" infrared measurements of water vapor from the C-141A Kuiper Airborne Observatory of the National Aeronautics and Space Administration Ames Research Center show large, distinctly identifiable, signal anomalies from 4 to 10 minutes in advance of subsequent encounters with clear air turbulence (CAT). These anomalies are characteristically different from the signals not followed by CAT encounters. Results of airborne field trials in which the infrared radiometer was used indicate that, out of 51 situations, 80 percent were CAT alerts followed by CAT encounters, 12 percent were "false alarms" (CAT alerts not followed by CAT encounters), and 8 percent were CAT encounters not preceded by an infrared signal anomaly or CAT alert.     

Water vapor: observations of galactic sources

We measured the emission of water vapor at a wavelength of 1.35 centimeters from nine sources with the 120-foot (36.5-meter) Haystack antenna. Eight sources lie within 30 seconds of arc of the hydroxyl sources of 18 centimeters but not all hydroxyl sources produced detectable emission of water vapor. All sources are smaller than 30 seconds of arc in angular diameter, but we resolved at least three separate sources in the Orion Nebula. We do not find that the known hyperfine components are present with the equilibrium intensity distribution.     

Origin of the hard x-ray emission from the Galactic plane

The Galactic plane is a strong emitter of hard x-rays (2 to 10 kiloelectron volts), and the emission forms a narrow continuous ridge. The currently known hard x-ray sources are far too few to explain the ridge x-ray emission, and the fundamental question of whether the ridge emission is ultimately resolved into numerous dimmer discrete sources or truly diffuse emission has not yet been settled. In order to obtain a decisive answer, using the Chandra X-ray Observatory, we carried out the deepest hard x-ray survey of a Galactic plane region that is devoid of known x-ray point sources. We detected at least 36 new hard x-ray point sources in addition to strong diffuse emission within a 17' by 17' field of view. The surface density of the point sources is comparable to that at high Galactic latitudes after the effects of Galactic absorption are considered. Therefore, most of these point sources are probably extragalactic, presumably active galaxies seen through the Galactic disk. The Galactic ridge hard x-ray emission is diffuse, which indicates omnipresence within the Galactic plane of a hot plasma, the energy density of which is more than one order of magnitude higher than any other substance in the interstellar space.     

Mars: water vapor in its atmosphere

With the use of newly obtained spectrograms of Mars in the region of the water vapor band at 8200 angstroms, we have derived a value of 35 +/- 15 microns for the amount of precipitable water in a vertical column in the Martian atmosphere.     

Mercury: observations of the 3.4-millimeter radio emission

Observations of the 3.4-millimeter radio emission from Mercury during 1965 and 1966 yielded the following relationship between average brightness temperature T(B) of the disk and the planetocentric phase angle i: T(B) = 277 (+/- 12) + 97 (+/- 17) cos [i + 29 deg (+/- 10 deg)] degrees K The errors are statistical standard; the phase shift corresponds to a phase lag-that is, the maximum and minimum of insolation lag the maximum and minimum of planetary radiation.     

Enceladus' water vapor plume

The Cassini spacecraft flew close to Saturn's small moon Enceladus three times in 2005. Cassini's UltraViolet Imaging Spectrograph observed stellar occultations on two flybys and confirmed the existence, composition, and regionally confined nature of a water vapor plume in the south polar region of Enceladus. This plume provides an adequate amount of water to resupply losses from Saturn's E ring and to be the dominant source of the neutral OH and atomic oxygen that fill the Saturnian system.     

Mars: northern summer ice cap--water vapor observations from viking 2

Observations of the latitude dependence of water vapor made from the Viking 2 orbiter show peak abundances in the latitude band 70 degrees to 80 degrees north in the northern midsummer season (planetocentric longitude approximately 108 degrees ). Total column abundances in the polar regions require near-surface atmospheric temperatures in excess of 200 degrees K, and are incompatible with the survival of a frozen carbon dioxide cap at martian pressures. The remnant (or residual) north polar cap, and the outlying patches of ice at lower latitudes, are thus predominantly water ice, whose thickness can be estimated to be between 1 meter and 1 kilometer.     

Photoinduced nucleation of water vapor

Strong photoinduced nucleation of pure water vapor was found to occur in a wavelength range where no ultraviolet absorption of water vapor has been reported. Systematic studies were made of the dependence of the nucleation rate and the delay time for the initiation of nucleation on light intensity. The results obtained were accurately fitted by a phenomenological mechanism whereby the nucleation is initiated by clusters accumulating an appropriate number of photoexcited water molecules.     

Venus: further evidence of impact cratering and tectonic activity from radar observations

Earth-based radar images at a resolution of 10 kilometers show a diverse surface terrain on Venus, probably produced by both impact events and tectonic activity. Only a small number of craters of apparent impact origin are seen. Large-scale features show lineaments and parallel ridges suggesting tectonic origins.     

Venus: new microwave measurements show no atmospheric water vapor

Two sets of passive radio observations of Venus-measurements of the spectrum of the disk temperature near the 1-centimeter wavelength, and interferometric measurements of the planetary limb darkening at the 1.35-centimeter water vapor resonance-show no evidence of water vapor in the lower atmosphere of Venus. The upper limit of 2 x 10(-3) for the mixing ratio of water vapor is substantially less than the amounts derived from the Venera space probes (0.5 x 10(-2) to 2.5 x 10(-2)). This amount of water vapor cannot produce dense clouds, and it is doubtful that it may contribute significantly to a greenhouse effect.     

Viking: Mars atmospheric water vapor mapping experiment--preliminary report of results

Observations made from the Viking I orbiter show very little water vapor in the Mars atmosphere in the southern hemisphere (0 to 3 precipitable micrometers) with a gradual increase across the equator to northern latitudes. Maximum amounts between 20 and 30 micrometers have been observed in the short period covered by the observations to date. The season, northern midsummer, corresponds to the beginning of the water vapor cycle in that hemisphere. A strong repetitive diurnal cycling between the solid and vapor phases is observed at a site to the east of the Tharsis Ridge at 10 degrees north latitude; the vapor lies close to the martian surface and is most probably in saturation equilibrium with a surface haze or fog throughout much of the day.     

Stratospheric ozone with added water vapor: influence of high-altitude aircraft

Simple, steady-state models for ozone photochemistry, radiative heat balance, and eddy-diffusive mass transport can be combined to estimate water-induced changes in the stratospheric ozone concentrations and temperatures, the integrated ozone column, the solar power transmitted to the earth's surface, and the surface temperature. These changes have been computed parametrically for mixing fractions of water vapor between 3 x 10(-6) and 6.5 x 10(-6). With added water from the exhausts of projected fleets of stratospheric aircraft, the ozone column may diminish by 3.8 percent, the transmitted solar power increase by 0.07 percent, and the surface temperature rise by 0.04 degrees K in the Northern Hemisphere. Due to a cancellation of terms, temperatures in the lower stratosphere remain essentially unchanged. These results are sensitive to the form of the water profile and emphasize the potential role of convective transients near 30 kilometers.     

Tunable infrared laser spectroscopy of atmospheric water vapor

Absorption lines in the v, band of water vapor at 6.3 micrometers have been fully resolved by using a tunable semiconductor laser. Three attnospheric water vapor lines near 5.32 micrometers were studied in detail and found to have linle widths two to four times narrower than the width calculated by Benedict and Kaplan.     

The short-term temporal spectrum of precipitable water vapor

Short-term power spectra of the fluctuations in the precipitable water vapor measured with a dual-channel microwave radiometer are presented. The spectra, taken over 34-hour sampling periods, encompass periodicities from I day to about 10 minutes. The fluctuation power is associated with the average precipitable water vapor for the sampling period. The background noise spectrum of the radiometric instrument is also discussed.     

Venus: implications from microwave spectroscopy of the atmospheric content of water vapor

From comparison of theoretical and observed microwave brightness temperatures of Venus at 1.35 centimeters, the center of a water-vapor line, we obtain an upper limit of 0.8 percent for the water-vapor mixing ratio in the lower atmosphere. This limit is consistent with the amount of water vapor detected by Venera 4, the existence of aqueous ice clouds, and a greenhouse effect caused by water vapor and carbon dioxide. The computed spectra suggest that a sensitive procedure for detection of water vapor is examination of the wavelength region between I and 1.4 centimeters.     

Spectroscopic measurements of stratospheric nitric oxide and water vapor

Spectroscopic measurements have been made of the nitric oxide and water vapor concentrations in the stratosphere at an altitude of 28 kilometers. The measurements, carried out in situ with the use of a spin flip Raman laser, represent the first accurate determination of nitric oxide as a function of time (as the sun rose) from about 6: 30 to 14: 00 C. D. T.     

Galactic evolution: a survey of recent progress

Current observational knowledge bearing on the evolution of elliptical and disk galaxies is reviewed. Particular emphasis is placed on identifying the factors that appear common to all galaxies of a particular type as opposed to those that seem to depend on environmental conditions. The success of various classes of galactic formation and evolution models used to confront these data is evaluated.     

Galactic X-rays: Variable Sources in Hydromagnetic Waves

Galactic sources of x-rays fluctuating in intensity are explained as being small regions, of enhanced gas density and temperature, emitting thermal Coulomb bremsstrahlung of kiloelectron-volt energies. Hydromagnetic wave motions, of the magnetic fields in the galactic spiral arms, produce the enhanced regions by compressing the clouds of ionized gas to which they are tied by their high electrical conductivity. From the observed periods of fluctuation of a few months, together with the hydromagnetic velocity, it is estimated that the average size of sources does not exceed 10(16) centimeters. By using the formula for Coulomb bremsstrahlung and requiring that the sources shall produce the observed x-ray fluxes, one finds a second estimate of size of sources in agreement at about 1016 centimeters. Such regions are too small to be observable radio sources with current radio telescopes.