Ronald J. Angione

Worldwide Variations in Atmospheric Transmission: Baseline Results from Smithsonian Observations

Abstract Analysis is made of atmospheric transmission measurements taken during the first half of the twentieth century at thirteen widely separated sites by the Astrophysical Observatory of the Smithsonian Institution. Long and short period variations in the atmospheric transmission have been examined for the individual sites. Significant variations from one day to the next are not unusual. Seasonal variations are found for all sites, with characteristic summer maxima. The variations appear to be due almost entirely to variations in the aerosol component above the observing sites. The observed phases of these variations, the derived characteristic size distributions of the particles which cause them, and the correlations between atmospheric moisture and transmission lead to the conclusion that differences in the nature and sources of aerosols above arid and vegetated regions are detectable. Including the results of more recent studies, our best estimate is that, except for sporadic perturbations due to v...

Stratospheric ozone as viewed from the Chappuis band

Stratospheric total ozone values have been obtained for the period 1912–50 from analysis of Smithsonian data. Naturally caused variations of 25% or more are common over time scales ranging from months to decades. We suggest that the ozone layer acts as a shutter on the incoming solar energy, providing one of the long sought trigger mechanisms betwen solar activity and climatic change. The present state of knowledge of ozone climatology is not sufficient to support popular speculations about mans effects on the ozone layer.

Atmospheric transmission and climate: results from smithsonian measurements

Abstract A combination of published and archival observations from the Smithsonian Institutions Astrophysical Observatory (APO) is presented and analyzed. This paper concentrates on the data from the two primary sites—Mount Montezuma, Chile, and Table Mountain, California, from 1923 to 1957. Baseline values and their variations are presented for solar aureole brightness, precipitable water vapor, pyrheliometry, corrected pyrheliometry, and spectrobolometry. In addition to clouds and water vapor, possible causes for the observed variations in atmospheric transmission are volcanic eruptions, nuclear weapons testing, and aerosols from plants. Physical theories may not be sufficient to explain climate change, and considerations of biological processes may be required.

VARIATIONS IN ATMOSPHERIC WATER VAPOR: BASELINE RESULTS FROM SMITHSONIAN OBSERVATIONS

Analysis is made of midmorning measurements of absolute humidity at ground level, and spectroscopic determinations of total atmospheric precipitable water vapor above the field stations of the Astrophysical Observatory of the Smithsonian Institution (APO). The APO data used in this study cover the period 191252 and nine mountain sites (altitudes 1500 m-2711 m) in North and South America and Africa. Reported values for over 3000 days are used. Large seasonal variations are apparent, with the maximum amounts of precipitable water vapor occurring very close to midsummer at all sites. Substantial longer-term variations are also present. The observed mean amounts of precipitable water vapor for various APO sites show reasonable agreement with Kuipers generalized predictions. Study of the relation between precipitable water vapor and surface humidity shows a strong positive correlation, but the variance is so large that surface humidity is not a reliable indicator of precipitable water vapor for any particular day. Key words: atmospheric water vapor-atmospheric extinction

Spectroscopy of Galaxies in the Bootes Void

We investigate the physical properties of a sample of 26 galaxies in the Bootes void and classify these galaxies based on the emission lines in their spectra. Fourteen galaxies are classified as H II galaxies with properties similar to field H II galaxies. Two of these galaxies, 1432+5302 and 1507+4554, are extreme starburst galaxies. Approximately half of the galaxies with measurable Hα+[N II] emission have elevated rates of star formation. Analysis of the galaxy continua suggests that approximately one-third of the void galaxies have large populations of blue stars. Stellar absorption features from metals in more than half the galaxies in the sample indicate the presence of late-type stars. Emission lines are detected from the H I galaxy 1517+3949 for the first time. Two systems, 1510+4727 and 1517+3956, are identified as closely interacting galaxy pairs, bringing the total number of known galaxy pairs in the void to four. The galaxy 1458+4944 is a LINER, making at least five AGNs in the void. Classifications of eight galaxies in the sample remain unknown. The galaxies in the Bootes void are similar to field emission-line galaxies with respect to stellar populations, emission-line properties, fraction of AGN and fraction of galaxy pairs. This result is inconsistent with some models of galaxy formation in low-density environments.

Optical monitoring of 15 quasars

The data of fifteen quasars are analyzed to determine how well a short-term program of observation can characterize the general optical behavior as compared to a long-term program. Three major research objectives were pursued, namely, to measure archival brightness of the quasars, to compare the brightness observed (mid-1970) to that of the Harvard historical plate collection 1900-1950, and to compare the general behavior during a short-time (two years) to that found over 50 years. Results show that in eight of the 15 quasars the mean magnitude derived from the present short-epoch program differed by 0.11 mag or less from the mean determined in the long-epoch program. The mean difference for all 15 quasars was 0.20 mag. However, in two cases, the short program failed by 0.83 and 0.66 mag, respectively, in predicting the mean brightness. The largest rate of increase in brightness observed was 0.9 mag/day (3C263) and of decrease was 0.44 (3C345), and it is concluded that the rates of decrease and increase in brightness are essentially the same.

Baseline ozone results from 1923 to 1955

Abstract Baseline total atmospheric ozone values have been derived, using the Chappuis band, from historical data for 11 Smithsonian sites, including both Northern and Southern Hemispheres. The main baselines consist of 1194 and 970 days respectively for Mt. Montezuma, Chile and Table Mountain, California, covering a period of time from about 1923 to 1955. These are the two baselines reported on here. An earlier reported decrease in the ozone beginning in 1940 (Angione et al.) is erroneous and resulted from the use of the wavelengths published in the Smithsonian Annals, one of which was incorrect. A modern filter wheel radiometer was used to further develop and evaluate the Chappuis-band method. Two intercomparisons at Mauna Loa Observatory show the Chappuis-band measurements to be systematically lower than simultaneous Dobson values by about 14 percent. Because this difference could result from errors in the ozone absorption coefficients, it is important to firmly establish the correct values of these co...

TWENTY YEARS OF ATMOSPHERIC EXTINCTION AT MCDONALD OBSERVATORY

Atmospheric extinction coefficients in the U, B, V bands have been measured at McDonald Observatory on 382 nights covering the 20-year period December 1960 to December 1980. Analyses of these data characterize the natural levels and variations in atmospheric extinction during both perturbed (Mount Agung eruption) and unperturbed times. The need for nightly extinction measurements is clearly shown. No significant long-term trends were found. Power spectrum analysis shows only the sinusoidal seasonal variation with minimum extinction in January.

THE ALGOL SYSTEM XX CEPHEI

We present new five-color photometric and spectroscopic observations of the Algol system XX Cephei (V = 9.13, P = 2.3 days). This system is known to have a variable period. From analysis of both the period variations and the light curve we found no support for apsidal motion. However, there is a possible light-time effect. The period changes could also be episodic. Our spectroscopic analysis yielded a classification of A4. We found no evidence of features attributable to the cooler component or of active mass transfer. Our photometric solution, using the Wilson-Devinney modeling program, showed the system to be an Algol configuration with a mass ratio of 0.17. We determined the masses and radii, in solar units, to be M1 = 1.92, M2 = 0.33, R1 = 2.07, and R2 = 2.32, and the temperatures to be T1 = 8500 K and T2 = 4555 K. From the parallax given in the Hipparcos catalog, neglecting reddening, absolute magnitudes of MV = 1.73 and 4.43 were determined for the primary and secondary components, respectively.

The light curve of Comet Kohoutek

Abstract Visual estimates of total coma brightness define the light curve of Comet Kohoutek between November 24, 1973 and February 6, 1974. These data are well fitted by straight lines on the M -log r diagram. The preperihelion value of n is 2.2, and the post perihelion value is 3.8 up to January 16. A standstill in the decline is suspected between January 16 and 19. If the standstill is ignored the postperihelion data can be fitted less precisely by a single line with n = 3.3. From photoelectric measures on four nights between January 5 and 13 after perihelion, n is found to be 4.1. The average B-V with a 32.4 arc sec diaphragm for those four nights is 0.79 ± 0.04; no clear systematic variation with time is noted.