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Roberts, W. O.

Publications and source records attributed to Roberts, W. O..

10 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Interplanetary magnetic field polarity and the size of low-pressure troughs near 180 deg W longitude

The relationship between interplanetary magnetic field polarity and the area of low pressure (300 mbar) troughs near 180 deg W longitude is examined. For most of the winters from 1951 to 1973, the trough size, as indicated by the vorticity area index, is found to be significantly greater when the interplanetary magnetic field is directed away from the sun than when the field is directed towards the sun. This relationship is shown to hold for various combinations of winters and for most months within a winter, and be most pronounced at the time when polarity was determined. It is suggested that the phenomenon is caused by merging of interplanetary magnetic field lines, when polarity is directed away from the sun, with geomagnetic field lines in the Northern Hemisphere (where these measurements were made), allowing energetic particle fluxes to have access to the north polar region

Wilcox, J. M.↗
NASA NTRS1978

Solar plages and the vorticity of the earth's atmosphere

Three superimposed epoch analyses of the vorticity area index (VAI) at 500 mbar are described. The analyses used the following definitions of the zero days: (1) the central meridian passage (CMP) of very active solar plages; (2) the occurrence of peak values of the 10.7 cm solar radio flux; and (3) the CMP of active solar plages also accompanied at CMP by sharp rises in 10.7 cm solar radio noise. All three superimposed epoch analyses show a sustained rise in VAI several days before the zero day; the rise continues through the zero day and is followed by a sustained minimum in VAI several days after the zero day. The results suggest that the location of the very active plages play an important role in determining their meteorological influence. It is possible that the initial rise in VAI is caused by enhanced electromagnetic radiation associated with the solar activity, and that the decrease some days later is the result of the geomagnetic storm particle emission that generally follows the zero date.

Olson, R. H.↗
NASA NTRS1978

Analysis of a possible sun-weather correlation

In an attempt to verify the relationship between solar activity and precipitation posited by Xanthakis (1973), annual precipitation records from 2,548 stations in both hemispheres from the period 1850 to 1973 were examined. The strong negative correlation between solar activity and rainfall in the 60 to 70 deg N latitude belt found by Xanthakis appeared much less distinct in the present study. In addition, a spectral analysis indicated no significant spectral peaks having periods between 6 and 20 years, a finding which cast further doubt on the solar cycle-precipitation correlation.

Gerety, E. J.↗
NASA NTRS1975

Relationships between solar activity and climate change

The relationship between recurrent droughts in the High Plains of the United States and the double sunspot cycle is discussed in detail. It is suggested that high solar activity is generally related to an increase in meridional circulation and blocking patterns at high and intermediate latitudes, especially in winter, and the effect is related to the sudden formation of cirrus clouds during strong geomagnetic activity that originates in the solar corpuscular emission.

Roberts, W. O.↗
NASA NTRS1974

Influence of solar magnetic sector structure on terrestrial atmospheric vorticity

The solar magnetic sector structure has a sizable and reproducible influence on tropospheric and lower stratospheric vorticity. The average vorticity during winter in the Northern Hemisphere north of 20N latitude reaches a minimum approximately one day after the passing of a sector boundary, and then increases during the following two or three days. The effect is found at all heights within the troposphere, but is not prominent in the stratosphere, except at the lower levels. No single longitudinal interval appears to dominate the effect.

Wilcox, J. M.↗
NASA NTRS1974

Relationships between solar activity and climate change

Recurrent droughts are related to the double sunspot cycle. It is suggested that high solar activity generally increases meridional circulations and blocking patterns at high and intermediate latitudes, especially in winter. This effect is related to the sudden formation of cirrus clouds during strong geomagnetic activity that originates in the solar corpuscular emission.

Roberts, W. O.↗
NASA NTRS1973

Influence of solar magnetic sector structure on terrestrial atmosphere vorticity

The solar magnetic sector structure has a sizable and reproducible influence on tropospheric and lower stratospheric vorticity. The average vorticity during winter in the Northhern Hemisphere north of 20 deg N latitude reaches a minimum approximately one day after the passing of a sector boundary, and then increases during the following two or three days. The effect is found at all heights within the troposphere, but is not prominent in the stratosphere, except at the lower levels. No single longitudinal interval appears to dominate the effect.

Wilcox, J. M.↗
NASA NTRS1973

Solar magnetic sector structure - Relation to circulation of the earth's atmosphere.

The solar magnetic sector structure appears to be related to the average area of high positive vorticity centers (low-pressure troughs) observed during winter in the Northern Hemisphere at the 300-millibar level. The average area of high vorticity decreases (low-pressure troughs become less intense) during a few days near the times at which sector boundaries are carried past the earth by the solar wind. The amplitude of the effect is about 10 per cent.

Wilcox, J. M.↗
NASA NTRS1966

Atmospheric sciences for the space age

Space-age research programs to increase knowledge about global atmospheric circulation and to obtain data on changing weather patterns

ATMOSPHERIC CIRCULATION↗