太阳活动11年周期对气象参数影响

利用多种资料研究了太阳活动11年周期对全球气温、风场、海表温度(SST)的影响,结果表明:(1)在第21、22太阳活动周,中低纬对流层顶以上大气温度变化具有类似太阳黑子变化的11年左右周期,相对于太阳黑子数,气温变化具有1～2年的延迟性;相对于太阳活动低年,200～10 hPa大气在太阳活动高年整层增温,以赤道低纬地区...     

Diffuse solar radiation and associated meteorological parameters in India

Solar diffuse radiation data including global radiation, shortwave and longwave balances, net radiation and sunshine hours have been extensively analyzed to study the variation of diffuse radiation with turbidity and cloud discharges appearing in the form of atmospherics over the tropics. Results of surface radiation measurements at Calcutta, Poona, Delhi and Madras are presented together with some meteorological parameters. The monthly values of diffuse radiation and the monthly ratios of diffuse to global solar radiation have been examined, with a special emphasis in relation to the noise level of atmospherics at Calcutta in the very low frequency band. The results exhibit some definite seasonal changes which appear to be in close agreement with one another.     

Signatures of interplanetary transients behind shocks and their associated near-surface solar activity

Interplanetary transients with particular signatures different from the normal solar wind have been observed behind interplanetary shocks and also without shocks. In this paper we have selected four well-known transient interplanetary signatures, namely: magnetic clouds, helium enhancements and bidirectional electron and ion fluxes, found in the solar wind behind shocks, and undertaken a correlative study between them and the corresponding solar observations. We found that although commonly different signatures appear in a single interplanetary transient event, they are not necessarily simultaneous, that is, they may belong to different plasma regions within the ejecta, which suggests that they may be generated by complex processes involving the ejection of plasma from different solar regions. We also found that more than 90% of these signatures correspond to cases when an H flare and the eruption of a filament occurred near solar central meridian between 1 and 4 days before the observation of the disturbance at 1 AU, the highest association being with flares taking place between 2 and 3 days before. The majority of the H flares were also accompanied by soft X-ray events. We also studied the longitudinal distribution of the associated solar events and found that between 80% and 90% of the interplanetary ejecta were associated with solar events within a longitudinal band of ±30° from the solar central meridian. An east-west asymmetry in the associated solar events seems to exist for some of the signatures. We also look for coronal holes adjacent to the site of the explosive event and find that they were present almost in every case.     

Ionospheric variability over Grocka during low solar activity conditions

The variability of the critical frequency of F2 layer, foF2, over ionospheric station Grocka (44.48N, 20.31E) has been studied during the declining phase of solar cycle 23 from 2004 to 2006. The variability index was introduced to identify the daily and seasonal patterns characterizing the local mid-latitude ionosphere during quiet and disturbed geomagnetic conditions. In addition, the behaviour of the vertical total electron content values, vTEC, obtained from global positioning system (GPS) measurements in the surrounding area under these conditions is reported. The analysis shows a number of interesting features representative of the ionospheric variability relevant for ionospheric modelling as well as ionospheric propagation applications based on a single station approach.     

On the relation between solar motion and the long term variability of solar activity

Summary The Sun's motion round the barycentre of the solar system was found to consist of two basic alternately repeating elements of the noose and of the arc. The mean time for solar motion around each of these elements was found to be 9.93 yr. The relation between solar motion and solar variability was determined as follows: Approximately coincident periodicities ranging from 60 to 2200 yr were traced in both phenomena and a coincidence of all prolonged minima in solar activity with the epochs of the highest deviations from the Jupiter—Saturn order was found over a time interval of 3100 yr.

---

ma, m ¶rt;uu a ma mmu um mum u ¶rt; , n nmu m — u nmu u u au. uu a a¶rt; u mu m ¶rt;um ¶rt; 9.93¶rt;a. am a maa ¶rt; ¶rt;uu a u au amumu: a mu m n¶rt;anum—am a aa nuuum maa u¶rt;um ¶rt;uuu a n¶rt;ea 60–2200 m, a u amumu, a mu umaa ¶rt;umm 3100 m a¶rt; n na¶rt;u ¶rt; uu amumu nu¶rt;au aua mu m n¶rt;a — u am.

     

Phase-coherent oscillatory modes in solar and geomagnetic activity and climate variability

Oscillatory modes with the period of approximately 7–8 yr were detected in monthly time series of sunspot numbers, geomagnetic activity aa index, NAO (North Atlantic Oscillation) index and near-surface air temperature from several mid-latitude European locations. Instantaneous phases of the modes underwent synchronization analysis and their statistically significant phase coherence, beginning from 1950s, has been observed. Thus the statistical evidence for a coupling between solar/geomagnetic activity and climate variability has been obtained from continuous monthly data, independent of the season, however, confined to the temporal scale related to oscillatory periods about 7–8 yr.     

Selected solar wind parameters at 1 AU through two solar activity cycles

In situ measurements of the solar wind largely cover more than two solar magnetic activity cycles, namely 20 and 21. This is a very appealing opportunity to study the influence of the activity cycle on the behaviour of the solar wind parameters. As a matter of fact, many authors so far have studied this topic comparing the long-term magnetic field and plasma averages. However, when the average values are evaluated on a data sample whose duration is comparable with (or even longer than) the solar rotation period we lose information about the contribution due to the fast and the slow solar wind components. Thus, discriminating in velocity plays a key role in understanding solar cycle effects on the solar wind. Based on these considerations, we performed a separate analysis for fast and slow wind, respectively. In particular, we found that: (a) fast wind carries a slightly larger momentum flux density at 1 AU, probably due to dynamic stream-stream interaction; (b) proton number density in slow wind is more cycle dependent than in fast wind and decreases remarkably across solar maximum; (c) fast wind generally carries a magnetic field intensity stronger than that carried by the slow wind; (d) we found no evidence for a positive correlation between velocity and field intensity as predicted by some theories of solar wind acceleration; (e) our results would support an approximately constant divergence of field lines associated with corotating high-velocity streams.     

Temperature variability in central Mexico and its possible association to solar activity

Minimum extreme temperature variability from five meteorological stations in the central part of Mexico covering a period from 1920 to 1990 is examined. We found a correlation coefficient (r=0.65) between these temperature records and geomagnetic activity. Furthermore, by performing spectral analysis peaks were obtained with similar periodicities to those found in the sunspot number, the magnetic solar cycle, cosmic ray fluxes and geomagnetic activity; all of these phenomena are modulated by solar activity. Signals with periodicities comparable to those observed in El Niño and the Quasi-Biennial Oscillation were also identified. We conclude that the solar signal is probably present in the minimum extreme temperature record of the central part of Mexico.     

High-latitude methane sulphonic acid variability and solar activity: the role of the total solar irradiance

The direct impact of solar activity on climate has been widely studied through Total Solar Irradiance (TSI). Biological processes also impact climate and are deeply affected by TSI. Marine phytoplankton emissions into the atmosphere have been proposed to change cloud albedo through cloud formation. In this work, we use wavelet analysis to investigate the decadal relation between high-latitude concentrations of methane sulphonic acid, a product of seawater algae, and TSI. We found that some of the methane sulphonic acid main periodicities coincide with periods of solar activity periods.     

Effect of solar dynamics parameters on the formation of substorm activity

An algorithm for retrieving the AL index dynamics from the parameters of solar-wind plasma and the interplanetary magnetic field (IMF) has been developed. Along with other geoeffective parameters of the solar wind, an integral parameter in the form of the cumulative sum Σ[N*V ²] is used to determine the process of substorm formation. The algorithm is incorporated into a framework developed to retrieve the AL index of an Elman-type artificial neural network (ANN) containing an additional layer of neurons that provides an “internal memory” of the prehistory of the dynamical process to be retrieved. The ANN is trained on data of 70 eight-hour-long time intervals, including the periods of isolated magnetospheric substorms. The efficiency of this approach is demonstrated by numerical neural-network experiments on retrieving the dynamics of the AL index from the of solar wind and IMF parameters during substorms.     

Long-period fading in atmospherics during severe meteorological activity and associated solar geophysical phenomena at low latitudes

The records of VLF atmospherics over Calcutta and then over Kalyani (West Bengal) during the torrential rainfall, caused by violent monsoon and post-monsoon depressions, exhibit distinct long-period fadings both at day and night. Interesting results obtained from an analysis of round-the-clock atmospherics data and associated meteorological parameters are reported in this paper. A possible correlation between the severe meteorological activity with the solar geophysical phenomena was studied. The results are indicative of an interesting sequence of solar-terrestrial events. A tentative conclusion is reached, suggesting an origin of the fading from atmospheric gravity waves generated in the centre of activity of the depressions concerned.Currently at: Department of Physics, Serampore College, Serampore, 712 201 West Bengal     

Effects of solar and geomagnetic activities in variations of power spectra of electrical and meteorological parameters in the near-Earth atmosphere in Kamchatka during October 2003 solar events

We perform spectral analysis of records of meteorological (temperature, humidity, pressure of the atmosphere) and electrical (strength of quasi-static electric field and electric conductivity of air) parameters observed simultaneously at the Paratunka observatory during the solar events of October 21–31, 2003. Also, we use simultaneous records of X-ray fluxes of solar radiation, galactic cosmic rays, and the horizontal component of the geomagnetic field. We show that the power spectra of the meteorological parameters under fine weather conditions involve oscillations with a period of thermal tidal waves (T ～ 12 and 24 h) caused by the influx of thermal radiation of the Sun. During strong solar flares and geomagnetic storm of October 29–31 with a prevailing component of T ～ 24 h, their spectra involve an additional component of T ～ 48 h (the period of planetary-scale waves). With the development of solar and geomagnetic activities, the power spectra of atmospheric electric conductivity and electric field stress involve components of both thermal tidal and planetary-scale waves, which vary highly by intensity. In the power spectra of galactic cosmic rays accompanying the strong solar flares, components with T ～ 48 h were dominant with the appearance of additional (weaker by intensity) components with T ～ 24 h. The simultaneous amplification of components with T ～ 48 h in the power spectra of electric conductivity and electric field strength provides evidence of the fact that the lower troposphere is mainly ionized by galactic cosmic rays during strong solar flares and geomagnetic storms. The specified oscillation period with T ～ 48 h in their spectra, as well as in the spectra of X-ray radiation of the sun, is apparently caused by the dynamics of solar and geomagnetic activities with this time scale.     

The impact of solar radiation and solar activity on climate variability after the end of the last glaciation

This paper analyzes climate changes since the end of the last glaciations 19–20 thousand years ago, including the modern warm interglacial Holocene age, which started about 11.5 thousand years ago. The connection between the impact of the orbital effect and solar activity on the Earth’s climate is studied. This is important for estimation of the duration of the modern interglacial period. It is shown that there is significant inconsistency between temperature variations in Holocene, which is deduced from the large amount of recently obtained indirect data and the temperatures reproduced in the climate models. The trends of climate cooling in the Holocene on the whole and during the last 2000 years are investigated.     

Variations in ionospheric parameters during solar flares

Results of studying the ionospheric response to solar flares, obtained based on the incoherent scatter radar observations of the GPS signals and as a result of the model simulations, are presented. The method, based on the effect of partial “shadowing” of the atmosphere by the globe, has been used to analyze the GPS data. This method made it possible to estimate the value of a change in the electron content in the upper ionosphere during the solar flare of July 14, 2000. It has been shown that a flare can cause a decrease in the electron content at heights of the upper ionosphere (h > 300 km) according to the GPS data. Similar effects in the formation of a negative disturbance in the ionospheric F region were also observed during the solar flares of May 21 and 23, 1967, at the Arecibo incoherent scatter radar. The mechanism by which negative disturbances are formed in the upper ionosphere during solar flares has been studied based on the theoretical model of the ionosphere-plasmasphere coupling. It has been shown that an intense ejection of O⁺ ions into the above located plasmasphere under the action of a sharp increase in the ion production rate and the thermal expansion of the ionospheric plasma cause the formation of a negative disturbance in the electron concentration in the upper ionosphere.     

Analysis of meteorological drought variability in Niger and its connection with climate indices

Based on a three-month-scale standardized precipitation index (SPI-3) computed from the available rainfall data of 13 stations of Niger, meteorological drought trends, periodicities and the relationships with 10 oceanic–atmospheric variables were analysed using the Mann-Kendall test, continuous wavelet transform and cross-wavelet analysis, respectively. The results revealed a significant (p < 5%) increase in drought at five of the 13 stations. A common dominant drought periodicity of 2 years was found at all of the stations, whereas significant periodicities varied from 2 to 32 years at six stations. Among the considered climate indices, South Atlantic sea-surface temperature, Southern Oscillation Index, sea-level pressure, geopotential height and relative humidity from the Atlantic basin oscillated in anti-phase relative to the SPI-3 at an inter-annual to decadal time scale from 1960 to 1990. In this period, relative humidity from the Mediterranean basin and zonal wind oscillated in phase with the drought index.     

Bottomside profile shape parameters during low solar activity and comparisons with IRI-2007 model

Modern digital ionosonde measurements at low–middle latitude station, New Delhi, India, are used to assess the IRI-2007 model for the bottomside profile shape parameters B0 and B1 during solar minimum. Comparative analysis shows that in general, the IRI (B0 Table) option reveals better agreement with the B0 observations during daytime in all the seasons, while outside this time period, the IRI (Gulyaeva) predicted B0 values are closer to the observations. For B1 parameter, both the options in the IRI reproduce similar diurnal variations in all the seasons and are closer to observed values except during pre-sunrise and post-sunset hours.     

Modelling the impact of solar variability on climate

Computer simulations of the impact on climate of solar variability generally fall into four categories. First, there are lower atmosphere GCM experiments, in which enhanced solar activity is represented by changes in spectrally integrated solar constant. Secondly, there are GCM studies of the dynamical response of the middle atmosphere to changes in solar ultraviolet, mainly concentrating on the northern hemisphere winter, and how these impact the troposphere. These studies have been instructive in providing an understanding of some of the mechanisms involved but, because of the very different nature of the assumptions made, give rather different suggestions as to potential patterns of change. In particular predicted zonal mean temperature changes in the lower stratosphere are usually of opposite sign in these two types of experiment. None of these GCM studies include interactive photochemistry and the third category of modelling work is concerned with the photochemical response of the middle atmosphere to enhanced solar ultraviolet. These generally employ 2D models to predict changes in ozone and other gaseous species. Recently it has been realised that the responses (to a variety of external forcings) of the lower and middle atmospheres are linked through both radiative and dynamical mechanisms and should not be viewed in isolation from each other. Thus the fourth type of modelling study, which is still in its infancy, attempts to represent solar variability by realistic changes in both irradiance and ozone concentrations. In this paper these various modelling studies are reviewed and some new results presented which confirm previous theoretical suggestions that, in the northern hemisphere winter, the atmosphere may respond to solar changes in a similar way as to the injection of volcanic aerosol. The implications of the results of the model studies for the detection of solar-induced climate change are discussed.     

Effects of short-term solar uv variability on the stratosphere

Changes in solar ultraviolet flux produce changes in ozone concentration in the upper stratosphere with associated radiative and dynamical effects. At low latitudes, the response of ozone mixing ratio to solar UV variations on the time scale of the solar rotation period is well characterized observationally. In addition, there is some provisional evidence for an ozone response at intermediate periods of 60-80 days. Current two-dimensional stratospheric models simulate the observed 27-day response amplitudes and phase lags with reasonable accuracy in the upper stratosphere. The observed response of total ozone on the 27-day time scale is also in approximate agreement with the same models although observed ozone sensitivities and phase lags are slightly larger than expected theoretically. Future studies of the 27-day response at higher latitudes and altitudes are needed to test more completely our understanding of the direct effects of solar UV variability on the middle atmosphere.     

Defining area-average parameters in meteorological models for land surfaces with mesoscale heterogeneity

After a brief review of existing methods developed to describe the subgrid variability of soil and vegetation at large scale, the paper summarizes aggregation results obtained in the framework of the Hapex-Mobilhy and EFEDA field experiments. The parameter aggregation method is based on the estimation of effective parameters for the soil and for the vegetation, representative of the large area. In conditions of moderate land-surface variability, the effective surface fluxes computed using a single column model forced by effective surface parameters are close to the areally-averaged turbulent fluxes estimated by a mesoscale model. A simple method for accounting for the subgrid variability of intercepted rain is tested.