Interannual fluctuations of the stratospheric temperature over the north polar region

The monthly means for the years 1964–1991 of 30 hPa temperatures over the North Pole and averaged over the 70–90°N region are analyzed. A multiple regression model is used to find long-term monthly trends and possible linear associations between these temperatures and the QBO, ENSO, and the 11-yr solar cycle. The model's residuals are examined for detection of other periodic interannual fluctuations in Arctic temperatures.It is found that the interannual variations of temperature at 30 hPa over the Arctic are a superposition of the oscillations due to the QBO, ENSO, the 11-yr solar cycle, and approximate 6-yr periodic fluctuations of unknown origin. The QBO, ENSO, and the solar cycle effects in the Arctic temperature explain about 35% of the total variance of the temperature monthly anomalies. In winter, the QBO, ENSO, and the 11-yr solar cycle signals in the temperature data depend on the phase of the equatorial QBO. The polar vortex seems to be warmer (colder) than normal when the West (East) phase of the equatorial QBO in a period of high solar activity. The monthly temperature trends over the Arctic show seasonal variations with positive trends in February and March. The year-round trends (sum of the monthly trends) are about −0.5 K per decade.     

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.     

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.     

A search for a solar cycle-temperature relationship in the middle atmosphere over Volgograd

The variation of temperature in the middle atmosphere (15–80 km) at Volgograd (49°N, 44°E) during an 11-year solar cycle (1971–1982) has been studied. The temperature of the stratosphere did not show any significant influence of the sunspot cycle, but the temperatures of the mesosphere showed a strong in-phase relationship with the solar cycle. Computed correlation and regression coefficients were positive and highly significant in this region. At 60 and 70km the temperature variations were almost linearly related to the sunspot number. Seasonal studies indicated that solar activity has a much stronger influence on temperature during the winter than during the summer.     

Variability of the solar cycle length during the past five centuries and the apparent association with terrestrial climate

Solar data have been used as parameters in a great number of studies concerning variations of the physical conditions in the Earth's upper atmosphere. The varying solar activity is distinctly represented by the 11-yr cycle in the number of sunspots. The length of this sunspot period is not fixed. Actually, it varies with a period of 80–90 yr. Recently, this variation has been found to be strongly correlated with long-term variations in the global temperature. Information about northernhemisphere temperature based on proxy data is available back to the second half of the sixteenth century. Systematic monitoring of solar data did not take place prior to 1750. Therefore, a critical assessment of existing and proxy solar data prior to 1750 is reported and tables of epochs of sunspot minima as well as sunspot cycle lengths covering the interval 1500–1990 are presented. The tabulated cycle lengths are compared with reconstructed and instrumental temperature series through four centuries. The correlation between solar activity and northern hemisphere land surface temperature is confirmed.     

Satellite and rocket studies of relativistic electrons and their influence on the middle atmosphere

Magnetospheric electrons from hundreds of keV to over 10MeV in energy have been systematically measured at geostationary altitude (6.6 R_E) for well over a decade. We find evidence of significant diurnal, solar-rotational (27-day), annual, and solar-cycle (11-yr) variations in the fluxes of the relativistic electron component. We have also used low-altitude satellite data and sounding rocket measurements to characterize the location and strength of the relativistic electron precipitation into the atmosphere. We conclude that the magnetospheric electrons, when dumped into the middle atmosphere, represent a very significant ionization source which affects the pattern of conductivity, electric fields, and atmospheric chemistry. These measurements—when combined with global atmospheric modeling—suggest that relativistic electrons provide a robust coupling mechanism to impose long-term solar wind and magnetospheric variability onto the Earth's deep atmospheric regions. A strong 11-yr cycle of relativistic electron effects is found in available atmospheric data sets.     

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.     

Solar cycle and long-period variations of mesospheric temperatures

Evidence for a temperature variation above about 55 km between years of high and low solar activity is found in rocket data of Volgograd (49°N, 44°E) 1969–1983, reaching a solar-cycle amplitude of 6K, whereas below 55 km no statistically significant solar cycle effect is detected. This mesospheric temperature variation is in qualitative agreement with a pressure variation at 80 km derived from lower ionosphere radio reflection heights near 51°N, 13°E, measured at Kühlungsborn/GDR, covering almost two solar cycles. When the solar cycle variation has been removed from these 80 km pressure data by means of a regression analysis, there remains a quasi-cycle of about 20 yr, which agrees well with observations of a general cooling of the northern mid-latitude stratosphere between 1965 and 1977, reported by other authors.     

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.     

Long term periodicities in lower thermospheric wind variations

An analysis of long term meteor radar wind measurements for three temperature latitude stations shows that significant solar cycle oscillations with periods of 22 years and 11 years can be detected in the data.     

Solar cycle and seasonal variations of the low latitude OI 630 nm nightglow

Regular zenith measurements of the OI 630 nm nightglow emission have been carried out at Cachoeira Paulista (22.7°S, 45.0°W; geomag. 11.9°S), Brazil, since 1975. The long series of observations during the period 1975–1982, including the ascending phase of the last solar cycle, permitted studies of solar cycle effects and seasonal variations. A large intensity increase, about seven times, from low solar activity to high solar activity has been observed. Also, the seasonal-nocturnal intensity variations show large changes between years of low and high solar activity. The characteristics of the variations observed are closely related to the equatorial electric field variations, since the observation site is under the southern equatorial ionospheric anomaly crest.     

The 27 day solar UV response of stratospheric ozone: solar cycle 21 vs. solar cycle 22

A correlative study of ozone and the solar UV flux on the time scale of a solar rotation shows an anomalous response of ozone in the upper stratosphere during solar cycle 22. The study, which is based on the analysis of ozone and solar UV flux measured by the SBUV/2 spectrometer on NOAA 11 (January 1989–December 1990), shows a sharp transition from an in-phase relation between ozone and the solar UV flux below 2 mb to an almost out-of-phase relation above 1 mb. Such a phase change is not predicted by photochemical models and was not observed during solar cycle 21. The ozone measurements from the Nimbus-7 SBUV spectrometer from 1979 to 1984 showed an almost in-phase relation between ozone and the solar UV flux at these heights (in agreement with model predictions). Similar studies of ozone and temperature relations between 30 and 1 mb did not show significant changes from the solar cycle 21 to 22. The temperature oscillations appear to be primarily of dynamical origin, with no apparent correlation with solar UV flux.     

Long-period variations of wind parameters in the mesopause region and the solar cycle dependence

A solar dependence of wind parameters below 100 km was found by Sprenger and Schminder on the basis of long-term continuous ionospheric drift measurements (D1) in the l.f. range. For winter they obtained for the prevailing wind a positive correlation with solar activity and for the amplitude of the semi-diurnal tidal wind a negative correlation. Later on this result was confirmed by radar meteor wind measurements (D2) at Obninsk and further D1 measurements at KÜhlungsborn and Collm.However, after the years 1973–1974 a change in the behaviour of the zonal prevailing wind was observed. At this time we found a significant negative correlation with solar activity with an indication of a new change after 1983. This was obtained from D1 results in Collm and D2 results in Kühlungsborn not only for winter, but also for summer and even for annual averages. We conclude that this long-term behaviour points rather to a climatic variation with an internal atmospheric cause than to a direct solar control. The negative correlation with solar activity of the semi-diurnal tidal wind in winter remained unchanged (up to 1984) and also proved to be the same in summer and for annual averages. Recent satellite data of the solar u.v. radiation and the upper stratospheric ozone have shown that the possible variation of the thermal tidal excitation during the solar cycle amounts to only a few per cent. This is, therefore, insufficient to account for the 40–70% variation of the tidal amplitudes. Some other possibilities of explaining this result are discussed.     

明清时期(1440-1899年)长江中下游地区冬季异常冷暖气候研究

本文以长江中下游地区的七个省市为研究对象 ,利用方志资料 ,在有记载的年份中从各省市每年只取一条资料 ,按照资料冷暖程度分别赋予一定的值 ,以十年为单位 ,将这些值相加 ,然后将所得的总数除以 10 ,本文称之为温度指数 ,共得到 4 6个温度指数值 ,取其平均数 1.7为参数 ,大致可将明清时期 (14 4 0年到 1899年 )冬季异常气候变化的过程分为三个暖时段 ,即 14 4 0 -14 89年 ,15 2 0 - 16 19年和 172 0 - 1789年 ;三个冷时段即 14 90 - 15 19年 ,16 2 0 - 1719年和 1790 -1899年。无论在暖时段还是冷时段 ,总存在着与之相反的极端个别或一些年份的冷或暖的回旋。如在第二个暖时段中 15 6 0年至 15 6 9年、第三个暖时段中 174 1至 174 6年冷冬的回旋和在第二个冷时段中 170 0至 170 9年、第三个冷时段中 185 0至 185 9年暖冬的回旋     

foF2 hysteresis variations and the semi-annual geomagnetic wave

Seasonal and solar cycle variations of the foF2 hysteresis magnitude are investigated. Data for the noon foF2 monthly medians for Slough (51.48°N, 0.57°W), the monthly means for the sunspot numbers, and for the geomagnetic activity index aa(N) for the northern hemisphere for the period 1933–1986, covering solar cycle from 17 to 21, are used. It is found that: (1) the greatest negative amplitudes of the foF2 hysteresis variation are near the equinoxes, and (2) the solar cycle average noon foF2 hysteresis magnitude is linearly correlated with the solar cycle average semi-annual geomagnetic amplitude of the aa-index. These results support the hypothesis that the foF2 hysteresis is due to the geomagnetic activity variation during the sunspot cycle.     

QBO and solar activity effects on temperatures in the mesopause region

This statistical correlation study is based on two upper mesospheric temperature data sets for the region around 90 km, on the phase of the quasi-biennial oscillation (QBO) and on the solar 10.7-cm radiation. The temperatures are measurements from passive OH1-spectrometers and lidar sounding experiments carried out between 1980 and 1988 at geographic latitudes between 50°N and 70° N. An anticorrelation exists betwen the 10.7-cm flux and the temperatures. Two different types of significance tests were used to check the confidence level of the correlation. The anti-correlation is highly significant (confidence ⪢ 99.99%) for latitudes around 50°N if the QBO is in its east phase and for the spring/summer temperatures. The anti-correlation is not significant for the QBO west phase and for fall/winter temperatures (confidence < 95%). For higher latitudes, around 79°N, no significant correlation was found.     

Modulation of the solar daily geomagnetic variation

A least squares spectral analysis is used to investigate cyclic and seasonal changes of the harmonic coefficients of the solar daily and semi-diurnal variation over the 24 year interval from 1 January 1960 to 31 December 1983 at a single magnetic observatory (Dourbes, Belgium). As a preparation for the treatment of other long runs of observations a statistical method is presented to combine the output of the spectral and harmonic analyses of a group of stations. The annual means of the Fourier coefficients are significantly correlated with the solar cycle. The spectra show peaks at periods of 11 years, 1 year, 6 months and 27 days, which entails an important amplitude and phase modulation of the daily and semi-diurnal variation. No simple relationship between the peaks in the broad solar rotation band can be proposed.     

Biodeterioration dynamics of marine wreck-sites determine the need for their in situ protection

The condition of a wooden shipwreck varies considerably according to the nature of the site environment. Each marine site exhibits a unique biodeteriogenic potential influenced by prevailing hydrographic factors. The potential rate of degradation of organic archaeological material can be determined by monitoring the diversity and activity of marine organisms and is important in determining if in situ protection is required. To illustrate the deteriogenic potential of marine archaeological sites a cold water site (Langstone Harbour, UK) was compared with a warm water site (Zakynthos, Greece). The warm water site supported a greater diversity and activity of wood-boring crustaceans and molluscs than the cold water site. However, although the mycodiversity at the two sites was different the deteriogenic potential was similar. These results indicated that warm water sites are more hazardous and in situ protection is required during and after excavation.     

Experimental daytime VLF ionospheric parameters

Measured field strengths from VLF transmitters are used to determine improved daytime values of ionospheric parameters to enable improved VLF propagation predictions. These parameters are the traditional H′ (height in km) and β (sharpness in km⁻¹) as used by Wait and by NOSC in their Earthionosphere waveguide computer program. They are found by comparing the predictions of the NOSC program with the observed VLF field strengths over both long and short paths.Experimental observations from two nearly north-south paths are used to determine the solar zenith angle dependence of both H′ and β for low latitude (or summer mid-latitude) conditions. These results are then used to predict the daytime variations in VLF field strengths with solar zenith angle (and hence time) on other suitable paths and good agreement is found with measurements made on these paths.The absolute value of β for overhead Sun is found to be 0.45 km⁻¹ and is principally determined by the attenuation on the very long, west to east, fully sunlit, 14.4 Mm path from NWC (Australia, 22°S) to San Francisco (37°N), after applying small corrections for the solar zenith angle variations along the path at midday. Further support is obtained from results from the 8.6 Mm path NDT (Japan) to San Francisco, an 8.2 Mm path NPM (Hawaii) to New Zealand, and an east to west 7.5 Mm path from NPM to Townsville, Australia. The conditions studied are solar maximum. The frequencies studied are 15–30 kHz.     

Dynamics and the ozone distribution in the winter stratosphere : modelling the inter-hemispheric differences

Results from a two year simulation of a General Circulation Model are used to illustrate the main differences found in the lower stratosphere dynamics and the ozone distribution between the Southern and the Northern Hemispheres in winter.The model extends from ground to mesospheric levels with a spectral horizontal resolution up to isotropic wavenumber 42. It incorporates a fully interactive scheme for the ozone mixing ratio which accounts for photochemical sources and sinks, advection by the model winds and coupling with radiative calculations.The model reproduces the large scale inter hemispheric differences quite well, with a very stable and cold vortex in the Southern Hemisphere and a warmer vortex often distorted in the Northern Hemisphere. It is concluded that due to interactions between dynamics, polar stratospheric cloud formation and chemistry, there is a possibility that some stratospheric ozone depletion could be effective in late winter near the night terminator in the Northern Hemisphere, whereas significant ozone depletion only occurs in early spring in the Southern Hemisphere.The importance of synoptic scale dynamics on the ozone transport between the high latitudes and the equator is also stressed. The model develops tongues of ozone-rich air from the high latitudes which are irreversibly mixed at mid-latitudes with tongues of ozone-poor air from the low latitudes. Similar tongues or filaments are clearly visible in the TOMS satellite data. They result from the activity of medium scale-waves in the Southern Hemisphere, whereas in the Northern Hemisphere the larger scale planetary waves play a major role in their development, and their size and extension are larger. It is concluded that transport of the ozone depletion to the mid-latitudes could be more effective in the Northern than in the Southern Hemisphere.