Monthly Sunspot Research Articles

Effect of Solar Activity on Atmospheric Ozone

THE ozone layer in the atmosphere constitutes a physical link of considerable importance between the upper atmosphere on one hand, and the lower atmosphere on the other. The former is known to respond directly to variations in the ultra-violet and corpuscular radiation from the Sun as evidenced by ionospheric and geomagnetic variations. On the other hand, the response of terrestrial weather and climate to solar activity has not been established with any degree of certainty; indeed, many of the solar-weather relationships investigated from time to time have remained controversial. The possible effect of solar activity on the ozone layer itself is thus of considerable importance in the context of the general problem of solar-terrestrial relationships. Ever since systematic measurements of total ozone by the Dobson spectro-photometer commenced, numerous attempts have been made to seek a relation between long-period variations in total ozone and solar activity, but the results obtained so far have been inconclusive. Among recent investigations on this problem may be mentioned that of Willet1, who after a study of world-wide ozone for a period of about 27 years came to the conclusion that there is a significant negative correlation between world-wide monthly average of total ozone and the monthly mean sunspot number. Mitchell2 has, however, reviewed Willet's statistical results and expressed doubts about the significance of the results. London and Haurwitz3 have also re-examined Willet's data and method of analysis and have shown that the correlations have no significance. The behaviour of total ozone in response to geomagnetic activity at individual stations has been examined by Ahmed and Halim4, who did not find any significant correlation. Kulkarni5, however, after studying the meridional gradient of total ozone during severe magnetic storms, has shown that in association with such storms the total ozone in high latitudes tends to decrease and that in middle latitudes it tends to increase. All this work refers to the total ozone. The relationship between solar activity and the fractional amount of ozone that is in photochemical equilibrium in the upper stratosphere appears not to have been examined.

The Zurich sunspot number and its variations for 1700-1957

A compilation of the monthly and annual daily relative sunspot number is given for the years 1749 to 1957. Wolf's annual values are recompiled and given, back to 1700 from 1749. Tabular data include monthly, annual, and moving 11-year means and totals. Times of cycle minima and maxima and appearances of first and last spots are indicated. Graphical presentations are given for the annual, 11- and 22-year means, cycle means and cycle totals, and for some monthly and five-monthly means. A check for continuation of a relationship of secular change to cycle length is made.

A new index of solar activity based on ionospheric measurements

The monthly mean relative sunspot number ( R M ) is assumed to contain a component ( R v ) which has a one-to-one correlation with the critical frequency of the F 2-layer in an undisturbed ionosphere and which is, therefore, an idealized index of solar activity. The residual component ( R x ) may be regarded as an error which has a Standard Deviation of about 20 per cent. A new index ( I F 2) has been constructed for the period 1938–1954; like R M , it can also be regarded as giving an approximate value of R v , but its residual error component ( R z ) has an S.D. which is only about one tenth that of R x . The magnitude of I F 2, for a given month is computed from the mean noon critical frequencies in the F 2-layer at Slough, Huancayo, and Watheroo, which are normally available within a few weeks of the end of each month. The index is based, in effect, on a calibration of the F 2-layer critical frequencies at these observatories in terms of R v , using data extending back as far as possible. Precautions have been taken to reduce to negligible proportions the effects of ionospheric disturbances on the magnitude of the new index.

Circulation of the Earth's Atmosphere

AT the International Meteorological Conference at Utrecht in September 1923, a resolution was passed that arose from a proposal of the late Prof. Exner for the calculation of coefficients of correlation between weather anomalies in distant parts of the world. This resolution was to the effect that long and homogonoous scries of observations of pressure, temperature and rainfall should be published with the view of furthering the study of the general circulation of the earth's atmosphere; that a small number of stations at a mutual distance of 500-1,000 kilometres should bo included, preferably stations belonging to the Roseau Mondial (a network of stations for which annual summaries are published); and that this material for publication should be collected with the aid of various meteorological institutes, the long series being taken up to the year 1920. This resolution took shape in vol. 79 of tho Smithsonian Miscellaneous Collections under the title “World Weather Records”, to which has been added recently a supplementary volume with the same title covering the period 1921-30, but also including some summaries of long records that were not available in time for vol. 79. The new material occupies the whole of vol. No. 90 of the same series of Miscellaneous Collections, the cost of publication being met by a grant from Mr. John A. Roebling. It is scarcely necessary to point out the advantage to students of world weather of a collection of data of this kind, which gathers together in a compact form material that is often obtainable only at great troublo and expense. It can be used by those who carry out statistical studies with the view of establishing equations for long-period forecasting on the lines developed by Sir Gilbert Walker and others, and also for the study of periodicities, while the addition of monthly sunspot and solar radiation data makes it possible to add the study of solar-terrestrial relationships. The supplementary material includes the long Edinburgh series, which goes back to 1731 for temperature and to 1770 for precipitation.

Emission of Light by Solid Nitrogen and the Origin of the Auroral Spectrum

The monthly mean relative sunspot number (RM) is assumed to contain a component (Rv) which has a one-to-one correlation with the critical frequency of the F2-layer in an undisturbed ionosphere and which is, therefore, an idealized index of solar activity. The residual component (Rx) may be regarded as an error which has a Standard Deviation of about 20 per cent. A new index (IF2) has been constructed for the period 1938–1954; like RM, it can also be regarded as giving an approximate value of Rv, but its residual error component (Rz) has an S.D. which is only about one tenth that of Rx. The magnitude of IF2, for a given month is computed from the mean noon critical frequencies in the F2-layer at Slough, Huancayo, and Watheroo, which are normally available within a few weeks of the end of each month. The index is based, in effect, on a calibration of the F2-layer critical frequencies at these observatories in terms of Rv, using data extending back as far as possible. Precautions have been taken to reduce to negligible proportions the effects of ionospheric disturbances on the magnitude of the new index.