Investigation of the responses of the general circulation at 700 mbar to solar geomagnetic disturbance

Abstract

The northern hemisphere 700-mbar contour heights from 20 ø to 70øN for the period 1947-1970 are studied in conjunction with 272 key days, where the daily increase of the Ci index equals or exceeds 1.0. The superposed epoch method is applied from 33 days before to 66 days after the key day for a variety of zonal and meridional indices. It is shown that the 700-mbar height difference between 20 ø and 55øN increases significantly in winter 4 days following geomagnetic disturbance (in summer a less prominent but statistically significant increase is found 2 days earlier). The effect is most clear in winter in the quadrant 90ø-175øW and corresponds to a 7% increase in the mean geostrophic westerly flow. The statistical significance of the results is established by applying Student's t test to the difference of each daily mean from the continuum. Synoptic analyses of the departures of the mean 700-mbar contour heights from seasonal climatology following geomagnetic disturbance reveal that the effect proceeds with the growth and development of large negative centers in the latitude belt 40ø-60øN and smaller positive departures at lower latitudes.A number of studies [Mustel et al., 1965; Mustel, 1966; Kubyshkin, 1965 Kubyshkin, , 1966 claim to have discovered surface pressure responses to solar geomagnetic disturbances. On the other hand, studies by Stolov and Spar [1968] and Stolov and Shapiro [1969] failed to substantiate the reported claims. More recent studies by Sarukhanyan and Smirnov [1970] and Mustel [1970] indicate that the zonal character of the atmospheric circulation is disrupted and that meridional processes are enhanced during disturbed periods. However, Stolov and Shapiro [1971] find no evidence for this claim.In earlier work, Shapiro [1956, 1959, 1972] working with sea level pressure data found significantly high persistence during the first week after large increases in geomagnetic activity along with an increase in the average north-south pressure gradient. A current study by Roberts and Olson [1973] confirms their earlier result connecting geomagnetic activity with a subsequent deepening of 300-rribar troughs.Encouraged by these positive results, we have been stimulated to extend our previous investigation. In this latest study the strong seasonal trend in the 700-mbar heights introduced by ordinary meteorological factors is removed as a possible obscuration in the detection of real general circulation changes following solar geomagnetic activity. Apparently, just such an approach was necessary. DATA The meteorological data consist of 1200 UT sea level pressures and 700-mbar heights from 20 ø to 70øN for the period January 1, 1947, to December 31, 1970. The data are available at 5 ø latitude intervals and 10 ø longitude intervals in a diamond-shaped grid. As measures of solar geomagnetic disturbance we selected in the preliminary investigation [Stolov and Shapiro, 1971]: (1) the 41 chromospheric flares (1956-1960) producing geomagnetic disturbance used by Mustel et al. [1965], (2) the 39 chromos...

Holocene environmental and climatic change in the Northern Great Plains as recorded in the geochemistry of sediments in Pickerel Lake, South Dakota

“…The decrease is greatest between 70 and 1103 west longitude and between 40 and 703 north latitude and corresponds to an increase by as much as 7% in tropospheric westerly #ow, which translates to an increase in mean zonal wind velocity of about 0.6 m/s. The Northern Great Plains lie near the center of the region where the strongest response by zonal winds has been reported (Stolov and Shapiro, 1974; see discussions by Anderson, 1992Anderson, , 1993. Statistical analyses by Tinsley and Deen (1991) of 33 yr of meteorological data show a clear correlation between the intensity of cyclonic circulation in mid-latitude oceanic regions with changes in cosmic-ray #ux following geomagnetic storms.…”

“…It is not known, however, how these upper-atmosphere winds affect the lower atmosphere (troposphere). Roberts and Olson (1973) observed that strong solar}geomagnetic disturbances in the troposphere during winter were often followed within a few days by a deepening of subpolar low-pressure systems (300 mbar troughs) over the North Paci"c. Stolov and Shapiro (1974) studied the 700 mbar heights in the northern hemisphere between 20 and 703 N for 33 d before and 66 d following 272 solar}geomagnetic disturbances over the period from 1947 to 1970. They noted that the most signi"cant response to these disturbances was a decrease in the 700 mbar height in winter relative to the average for the same period (`climatologya) four days following a disturbance.…”

Linkage between rainfall singularities and geomagnetic activity

“…The heaviest rainfalls are mostly associated with the increase in easterlies on or around the dates of singularities noticed. Shapiro and Stolov [26] have found significant increases in westerly winds at the 700 mb level in the longitude belt from 90°W to 180°W three to four days after the magnetic storms. Comparing geomagnetic data with the data on tropospheric and stratospheric circulation character-140 R.S.…”

Holocene climatic and limnologic history of the north-central United States as recorded in the varved sediments of Elk Lake, Minnesota: A synthesis

“…days later by an increase in tropospheric zonal winds at 700 mbar, and by the fact that Elk Lake lies near the center of the region between the Great Lakes and Hudson Bay where the strongest response to zonal winds has been reported (Stolov and Shapiro, 1974; see discussion by Anderson, Chapter 5). Another interesting aspect of the association is that the strongest oscillations in both varve thickness (regional surface winds) and radiocarbon (solar activity) occur at the time scale of the Maunder deviations, during which there appears to be a maximum effect on the solar wind (E. J.…”