Intensity of tropospheric circulation associated with solar magnetic sector boundary transits

The fractional decrease in the vorticity area index associated with transits past the Earth of interplanetary magnetic sector boundaries increases as the value of vorticity used to compute the index increases. This suggests that after the boundary transit there is an approximately uniform reduction in all the values of vorticity that are ≥20 × 10⁻⁵s⁻¹. In low latitudes and large absolute vorticities (≥ 30 × 10⁻⁵s⁻¹) the average change in the vorticity area index approaches 50%.     

Comment on connections between the 11-year solar cycle,the Q.B.O. and total ozone

Global total ozone does not show any evident connection during the period 1958–1984 with 10.7 cm solar flux (F_10.7). However, when the data are separated according to the east or west phase of the Quasi-Biennial-Oscillation (Q.B.O.) in the equatorial stratosphere, the following connection is found: when the Q.B.O. is in its west phase the global total ozone is positively correlated with the solar cycle; the opposite holds for the east phase of the Q.B.O.     

Influence of latitudinal and longitudinal variations of ozone and water vapour on the solar semidiurnal tide

A new tidal source model, based on climatological global ozone and water vapour distributions, has been obtained for January, April, July and October. The source model is used for modelling the solar semidiurnal tide in the lower thermosphere within the framework of the classical tidal theory. The observed phase quasibimodality of the semidiurnal tide at middle latitudes is possibly formed, to a great extent, by two types of hemispheric asymmetry (changing sharply near the equinox) of the ozone distribution. Near 95 km at middle latitudes, the ozone and water vapour distribution nonzonality yields typical values ~2 m/s for maximum longitudinal variations of the zonal and meridional wind amplitudes, and the range ~0.2–0.5 h for maximum longitudinal phase variations in the Northern hemisphere, while they can reach ~10 m/s and ~1.5 h in the Southern hemisphere. The hemispheric asymmetry is mainly caused by the effect of the water vapour tidal source.     

The boundary dispute between Chile and Argentina

In November 1920, James Young Simpson, Professor of Natural Science in New College, Edinburgh and Trinity College, Glasgow, was invited by the governments of Latvia and Lithuania to chair a commission which would settle the disputed border between the two newly‐independent states. Upon his return to Edinburgh in May 1921, Simpson deposited the papers and final report on the commission's decision with the Royal Scottish Geographical Society, of which he was an active member. This article will explain why and how Simpson came to be involved in diplomatic decisions so remote from his home life and work, and will analyse the significance of the results of Simpson's efforts on the arbitration commission.     

Influence of solar flares and disturbances of the interplanetary medium on the atmospheric circulation

The atmospheric circulation response to solar flares and geomagnetic disturbances is studied. It is shown that solar flares cause an increase of the zonal circulation intensity in the latitudinal belt ϑ = 45–65°, while geomagnetic disturbances are associated with a decrease of the circulation intensity.The energy necessary to produce the observed atmospheric circulation changes is estimated. The variation of the atmospheric transparency is suggested to be a possible source of that energy.     

The role of stratospheric minor warmings in producing the total ozone deficiencies over Europe in 1992 and 1993

During 1992 and 1993, record low total ozone values were observed over the middle and high northern latitudes. The ozone data from the long-operating station at Belsk, Poland, have been used to examine their departures from climatological behaviour in 1992 and 1993. It seems that not only do the exceptionally low ozone amounts recorded over the northern mid-latitudes need an explanation but also their occurrence for two years in a row. One of the possible mechanisms which may be responsible for this event is suggested to be connected with the occurrence of stratospheric minor warmings. They occur without a breakdown of the polar vortex but only with the displacement of very cold air towards lower latitudes (as in January 1992 and February 1993). It is known that air masses in the polar vortex have been chemically disturbed and, when they arrive over the sunlit middle latitudes, chemical destruction of ozone is likely to occur. During the periods under study, the strongest negative total ozone deviations correspond to strong negative temperature deviations at 30 hPa and to large potential vorticity values; this points to the presence over Europe of air masses of polar vortex origin. It has been shown that the characteristics of mid-winter stratospheric warmings and the interannual variability of winter-spring total ozone averages at Belsk are associated with each other.     

The nocturnal intermediate layer over South Georgia : solar and magnetic influence on occurrence

Ionograms from South Georgia (54°S, 37°W; L = 1.9) are used to investigate the influence of magnetic and solar activity upon the occurrence of the nocturnal intermediate layer. The diurnal variation in occurrence of this layer exhibits a peak at about 2000 LT and a subsidiary peak after midnight. It is shown that magnetic activity has no significant influence on the behaviour before midnight, but is positively correlated with the size of the post-midnight peak. The effect of varying solar activity is to introduce a local time shift (42 min for a change in mean solar activity from 80 to 130× 10⁻²² Wm⁻²Hz⁻¹)inthediurnal variation without otherwise changing the overall morphology of the layer significantly. Most of the features of the intermediate layer before midnight can be explained by a wind shear mechanism associated with the solar semi-diurnal tide. Some possible causes for the post-midnight observations are considered, but no firm conclusions can be made.     

Interaction of solar wind with the magnetopause-boundary layer and generation of magnetic impulse events

The transport of mass, momentum, energy and waves from the solar wind to the Earth's magnetosphere takes place in the magnetopause-boundary layer region. Various plasma processes that may occur in this region have been proposed and studied. In this paper, we present a brief review of the plasma processes in the dayside magnetopause-boundary layer. These processes include

• 1.(1) flux transfer events at the dayside magnetopause,
• 2.(2) formation of plasma vortices in the low-latitude boundary layer by the Kelvin-Helmholtz instability and coupling to the polar ionosphere,
• 3.(3) the response of the magnetopause to the solar wind dynamic pressure pulses and
• 4.(4) the impulsive penetration of solar wind plasma filaments through the dayside magnetopause into the magnetospheric boundary layer. Through the coupling of the magnetopause-boundary layer to the polar ionosphere, those above processes may lead to occurrence of magnetic impulse events observed in the high-latitude stations.

     

The middle atmospheric response to short and long term solar UV variations: analysis of observations and 2D model results

We have investigated the middle atmospheric response to the 27-day and 11-yr solar UV flux variations at low to middle latitudes using a two-dimensional photochemical model. The model reproduced most features of the observed 27-day sensitivity and phase lag of the profile ozone response in the upper stratosphere and lower mesosphere, with a maximum sensitivity of +0.51% per 1% change in 205 nm flux. The model also reproduced the observed transition to a negative phase lag above 2 mb, reflecting the increasing importance with height of the solar modulated HO_x chemistry on the ozone response above 45 km. The rnodel revealed the general anti-correlation of ozone and solar UV at 65–75 km, and simulated strong UV responses of water vapor and HO_x species in the mesosphere. Consistent with previous 1D model studies, the observed upper mesospheric positive ozone response averaged over ±40° was simulated only when the model water vapor concentrations above 75 km were significantly reduced relative to current observations. Including the observed temperature-UV response in the model to account for temperature-chemistry feedback improved the model agreement with observations in the middle mesosphere, but did not improve the overall agreement above 75 km or in the stratosphere for all time periods considered. Consistent with the short photochemical time scales in the upper stratosphere, the model computed ozone-UV sensitivity was similar for the 27-day and 11-yr variations in this region. However, unlike the 27-day variation, the model simulation of the 11-yr solar cycle revealed a positive ozone-UV response throughout the mesosphere due to the large depletion of water vapor and reduced HO_x-UV sensitivity. A small negative ozone response at 65–75 km was obtained in the 11-yr simulation when temperature-chemistry feedback was included,In agreement with observations, the model computed a low to middle latitude total ozone phase lag of +3 days and a sensitivity of +0.077% per 1% change in 205 nm flux for the 27-day solar variation, and a total ozone sensitivity of +0.27% for the 11-yr solar cycle. This factor of 3 sensitivity difference is indicative of the photochemical time constant for ozone in the lower stratosphere which is comparable to the 27-day solar rotation period but is much shorter than the 11-yr solar cycle.     

UVB radiation changes in Berlin between 1967 and 1990 following alterations in the ozone layering

Long-term measurements covering the past 24 yr in the vicinity of the city of Berlin have shown that ozone has increased in the troposphere and in the middle stratosphere and has decreased in the lower stratosphere. The total ozone column amount, however, has remained constant.Possible changes of the UV irradiance [280 nm ⩽ λ ⩽ 320 nm (UVB)], due to this observed vertical ozone redistribution, have been calculated. The analysis reveals an UVB irradiance increase at those times of each year where maximum ozone concentrations have occurred as well as during summer times. On the contrary, UVB has remained unchanged whenever ozone concentrations were minimal. In any case, however, the UVB irradiance oscillates with the sunspot cycle of ~ 11 yr period with an amplitude ⪝1%.     

On the problem of a connection between ozone dynamics at high latitudes and magnetospheric processes

Two data sets of ozone density measurements over a wide latitudinal range in the Arctic during summer and winter seasons arc presented. It is shown that geophysical effects manifest themselves in the O₃ dynamics in the high latitude region under various circumstances. Therefore a type of total ozone content diurnal variation is a distinctive feature in the auroral oval as well as the polar cap and must be taken into account in any full model of ozone dynamics in the polar regions.     

Heritage as sector,factor and vector: conceptualizing the shifting relationship between heritage management and spatial planning

Heritage is a highly malleable concept that is constantly in flux and whose substance and meaning are continuously being redefined by society. From such a dynamic perspective, it is inevitable that new approaches and practices have developed for dealing with heritage in the context of planned development. While most scholars acknowledge the existence of various heritage approaches, one of the major defining features is often neglected: their distinctive outlook on spatial dynamics. In this article, the shifting role and purpose of heritage conservation in Dutch spatial planning is analysed. A conceptual framework is introduced that frames three approaches to the planning treatment of heritage; the sector, factor and vector approach, respectively. Although these approaches have developed in a historical sequence, the new did not replace the old but rather gained ground amongst different actors. Thus, three quite different ways of treating the past in the present now coexist in Dutch planning practice. Although this coexistence can raise conflict, we argue that contemporary heritage planning does not call for a one-size-fits-all approach, but rather for a mixed-mode model.     

左、李塞防与海防之争新论

清同治、光绪年间,统治阶级内部在国防部署上曾有过一次塞防与海防之争.海防派以李鸿章为首,认为东南沿海千里海防是国防重点,主张弃新疆,专注海防.塞防派以左宗棠为首,主张塞防、海防并重,强调新疆在国防上的重要地位,坚决要求收复新疆.这场争论的实质是国防前线的战略部署和国家有限的财力如何分配;争论的焦点则是收复新疆还是放弃新疆.这场争论是公开的、正常的,其主张有正确与错误之分,其见解有高低之别,但不是爱国与卖国之争,不应因此给李鸿章戴上卖国或投降主义的帽子.     

Relation between Northern Hemisphere winter temperatures and geomagnetic or solar activity at different QBO phases

In our previous work a dominant coupling was shown between solar and geomagnetic activity, and surface air temperature of the QBO-west and east phases, respectively. The aim of the present study is to define ‘typical’ regions of positive and negative deviations from the long-term temperature average, to determine their magnitude and to find the conditions under which such a ‘typical’ distribution of temperature fields occurs.     

Associations between the 11-year solar cycle,the QBO and the atmosphere. Part I: the troposphere and stratosphere in the northern hemisphere in winter

Linear correlations between the three solar cycles in the period 1956–1987 and high-latitude stratospheric temperatures and geopotential heights show no associations. However, when the data are stratified according to the east or west phase of the quasi-biennial-oscillation (QBO) in the equatorial stratosphere significant correlations result: when the QBO was in its west phase the polar data were positively correlated with the solar cycle while those in middle and low latitudes were negatively correlated. The converse holds for the east phase of the QBO. Marked relationships existed throughout the troposphere too.No major mid-winter warming occurred in the west phase of the QBO during a minimum in the three solar cycles. In the east phase major warmings tended to take place in the minima of the cycle. Thus the signal of the quasi-biennial-oscillation in the extratropical stratosphere tends to be strengthened in solar minima, and weakened in solar maxima.     

On the influence of climatic factors on the ratio between the cosmogenic isotope 14C and total carbon in the atmosphere in the past

Radiocarbon ¹⁴C is a cosmogenic isotope, which is most extensively used by scientists from a wide variety of fields. Its rate of generation in the atmosphere depends on solar modulation and thus, studying ¹⁴C concentration in natural archives, one can reconstruct solar activity level in the past. The paper shows results of box-model calculations of generation of the ¹⁴C isotope in the atmosphere and its relative abundance during the time interval 1389–1800 AD, taking into account influence of changing climate. This interval includes the deep minimum of solar activity and period of significant change in atmospheric concentration of CO₂ and global temperature. The performed analysis showed that concentration of ¹⁴C in the atmosphere reflects not only variations of the galactic cosmic rays intensity but as well changes of temperature and atmospheric CO₂ concentration. It is shown that the decrease in CO₂ concentration in the atmosphere during 1550–1600 can be connected with absorption of CO₂ by the ocean surface layer. Thus, taking into account the climatic changes is an important condition for the reconstruction of solar activity in the past using data based on cosmogenic isotopes.