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1.
Measurements of solar EUV irradiance show, besides the ～11-year Schwabe cycle, a series of oscillations with a ～27-day period. They are generally explained by the passage of active regions across the solar surface resulting from the Sun's rotation, but the calculated amplitude underestimates the observed long-term variation in irradiance (Lean 1991). The variant of this model proposed here is modulation of EUV emission from the corona by rotation of the Sun's radiative zone. The response would be immediate, raising the prospect of short-term forecasting of EUV effects on space weather and on the Earth's atmospheric circulation.  相似文献   

2.
Stars with the same temperature, luminosity, chemical composition, and activity as the Sun may be designated “sunlike stars.” The variability of several dozen reasonably sunlike stars has been monitored regularly since 1966 in chromospheric Ca II HK emission, and since 1984 in the visual continuum; larger stellar samples have been observed less comprehensively. Similar solar time series exist. A comparison of solar variability with its stellar analogs indicates that the Sun's current behavior is not unusual among sunlike stars, although the amplitude of the Sun's cyclic variation, measured photometrically, may be smaller than that of its stellar analogs. If the ensemble characteristics of a sample of sunlike stars are representative of the Sun's possible behavior, then such samples may provide insight about states of solar activity, such as Maunder Minima, which have not been observed on the Sun during the contemporary era of space-based measurements. Future progress in solar–stellar research will likely require studies of (1) rigorously selected samples of sunlike field stars, and (2) larger samples from stellar clusters, observed using 4-m class telescopes equipped with multi-object spectrographs and CCD photometers.  相似文献   

3.
In this study, data from MODIS land surface temperature product level 3 (MOD11A2) were used to investigate the spatiotemporal variation of Eurasian lakes water surface temperature (LSWT) from 2001 to 2015, and to examine the most influencing factors of that variation. The temperature of most lakes in the dry climate zone and in the equatorial climatic zone varied from 17 to 31°C and from 23 to 27°C, respectively. LSWTs in the warm temperate and cold climatic zones were in the range of 20 to 27°C and −0.6 and 17°C, respectively. The average day time LSWT in the polar climate zone was −0.71°C in the summer. Lakes in high latitude and in the Tibetan Plateau displayed low LSWT, ranging from −11 to 26°C during the night time. Large spatial variations of diurnal temperature difference (DTD) were observed in lakes across Eurasia. However, variations in DTDs were small in lakes located in high latitude and in tropical rainforest regions. The shallow lakes showed a rapid response of LSWT to solar and atmospheric forcing, while in the large and deep lakes, that response was sluggish. Results of this study demonstrated the applicability of remote sensing and MODIS LST products to capture the spatial–temporal variability of LSWT across continental scales, in particular for the vast wilderness areas and protected environment in high latitude regions of the world. The approach can be used in future studies examining processes and factors controlling large scale variability of LSWT.  相似文献   

4.
Long-term series of midnight temperature in the mesopause region have been obtained from spectral observations of hydroxyl airglow emission (OH(6-2) λ840 nm band) at the Tory station (52° N, 103° E) in 2008–2016 and Zvenigorod (56° N, 37° E) station in 2000–2016. On their basis, the Lomb-Scargle spectra of the variations in the period range from ~12 days to ~11 years have been determined. Estimates of the amplitudes of statistically significant temperature fluctuations are made. The dominant oscillations are the first and second harmonics of the annual variation, the amplitudes of which are 23–24 K and 4–7 K, respectively. The remaining variations, the number of which was 16 for the Tory and 22 for Zvenigorod stations, have small amplitudes (0.5–3 K). Oscillations with combinational frequencies, which arise from modulation of the annual variation harmonics, are observed in a structure of the variation spectra in addition to interannual oscillations (periods from ~2 to ~11 years) and harmonics of the annual variation (up to its tenth harmonic).  相似文献   

5.
Changes in the Earth's radiation budget are driven by changes in the balance between the thermal emission from the top of the atmosphere and the net sunlight absorbed. The shortwave radiation entering the climate system depends on the Sun's irradiance and the Earth's reflectance. Often, studies replace the net sunlight by proxy measures of solar irradiance, which is an oversimplification used in efforts to probe the Sun's role in past climate change. With new helioseismic data and new measures of the Earth's reflectance, we can usefully separate and constrain the relative roles of the net sunlight's two components, while probing the degree of their linkage. First, this is possible because helioseismic data provide the most precise measure ever of the solar cycle, which ultimately yields more profound physical limits on past irradiance variations. Since irradiance variations are apparently minimal, changes in the Earth's climate that seem to be associated with changes in the level of solar activity—the Maunder Minimum and the Little Ice age for example—would then seem to be due to terrestrial responses to more subtle changes in the Sun's spectrum of radiative output. This leads naturally to a linkage with terrestrial reflectance, the second component of the net sunlight, as the carrier of the terrestrial amplification of the Sun's varying output. Much progress has also been made in determining this difficult to measure, and not-so-well-known quantity. We review our understanding of these two closely linked, fundamental drivers of climate.  相似文献   

6.
Using ground-based spectral measurements in the near-infrared range at the Zvenigorod scientific station of the Institute of Atmospheric Physics (56° N, 37° E) for 2000–2013, we obtained average nighttime changes in rotational and vibrational temperatures of hydroxyl with its emission layer localized at mesopause heights. The rotational temperature reflects the kinetic temperature of the emission layer of the atmosphere. The analysis made it possible to determine the characteristics of the first three harmonics of diurnal temperature dynamics in the mesopause region both with and without altitudinal oscillations of the OH emission layer. In both cases, the second and third harmonics are statistically significant: their amplitudes are ～1 K and the phases of their first maxima are near 0300 and 0130 local solar time.  相似文献   

7.
湖泊热力结构不仅影响湖泊内部生态环境,而且与区域气象和气候系统相互影响,但目前对湖泊垂直温度的观测研究仍非常匮乏.本研究基于青藏高原拉昂错连续的湖温和气象观测,分析了小时尺度和日尺度热力分层规律和混合层深度的变化特征.结果表明:拉昂错为冷多次完全混合型湖泊;湖表温度8月达到最大值,湖面敞水区和沿岸的湖表温度季节震荡相同,但存在一定的空间差异;与空气温度相比,湖表温度变幅小,降温更慢,峰值滞后约1个月.同时发现,拉昂错混合层深度变化较为规律,辐射和风速是影响湖泊混合层深度的主要外界因子.探明真实的高原湖泊分层规律,有利于提高湖泊模拟能力,为优化湖泊参数化方案提供参考.  相似文献   

8.
Shrinking or expansion of the solar shape and irradiance variations are ultimately related to solar activity. We give here a review on existing ground-based or space solar radius measurements, extending the concept to shape changes. We show how helioseismology results allow us to look at the variations below the surface, where changes are not uniform, putting in evidence a new shallow layer, the leptocline, which is the seat of solar asphericities, radius variations with the 11-yr cycle and the cradle of complex physical processes: partial ionization of the light elements, opacities changes, superadiabaticity, strong gradient of rotation and pressure. Based on such physical grounds, we show why it is important to get accurate measurements from scheduled dedicated space missions: PICARD, SDO, DynaMICCS, ASTROMETRIA, SPHERIS. Such measurements will provide us a unique opportunity to study in detail the relationship between global solar properties and changes in the Sun's interior.  相似文献   

9.
The mean palaeomagnetic pole position obtained from Upper Cretaceous rocks in west Sicily is at 21°N, 100°E (A95 = 15°), and at 38°N, 67°E (A95 = 31°) obtained from Middle Jurassic rocks. These pole positions are completely different from comparable pole positions for southeast Sicily and Africa and imply a clockwise rotation of west Sicily since the Upper Cretaceous of about 90° relative to southeast Sicily and Africa and also a clockwise rotation of about 60° relative to “stable” Europe. The sense of rotation of west Sicily is opposite to any known rotation of other crustal blocks in the central Mediterranean.  相似文献   

10.
In an effort to better understand the dynamics of westward velocities of the nocturnal F-region plasma, the climatology of the westward traveling plasma bubbles – WTB – occurring during quiettime is studied here. The climatology of the WTB is analyzed here based on airglow images obtained during 14 quiet days between 2001 and 2006 at the Brazilian station São João do Cariri (Geographic 7.45°S, 36.5°W, dip ～20°S). The frequency of occurrence of the WTB maximizes in the descending phase of the solar cycle. The WTB velocities ranged between ～20 and 40 ms?1. The frequency of occurrence had a peak value of only 3.65% at 2345 LT. The maximum occurrence of the WTB was in July–September. No WTB have been observed from November until April in all years 2001–2006. We show for the first time theoretically that the WTB dominant forcing mechanisms during geomagnetically quiet days are westward thermospheric winds.  相似文献   

11.
—Maximum entropy spectral analysis (MESA) has been applied to 24 series of hourly daily data and only one daily mean series for the horizontal (H) and vertical (Z) components of the geomagnetic field for the year 1983 as observed at Narssarssuaq, Greenland (71.2°N, 36.7°E) (gm coordinate). The method has isolated some prominent medium frequency signal components. The maximum peaks for H are at 06 hr (0.174 cycles per day (cpd), 3.2 × 104 db) and 08 hr (0.09 cpd, 3.5 × 104 db). Similarly, the maximum peak in Z is observed at 04 hr (0.114 cpd, 5.7 × 104 db). The spectral results for the daily-mean data indicate periods are greater than two days, with 178.5 days (nearly semiannual) being common to both H and Z. Other harmonics have been found for all the series of H and Z components which are mainly caused by the "Effective Period", i.e., the period produced by the combined effect of the sunspot numbers and the sun’s rotation period. Such frequencies correspond very well with those found in the geomagnetic indices A p ?, C p and AE. This suggests that the disturbance transient variations are caused by viscous interaction of the solar energies emanating from sunspot regions with the outermost magnetospheric boundary which, in turn, influences the magnetosphere-iono sphere coupling and produces the medium intensity long-duration continuous auroral activities (MILD CAAs) over high latitude regions. Thus, the higher latitude geomagnetic activities are nothing but the "effective period driven MILDCAAs" having a recurrence tendency of 27/n, where n is an integer.  相似文献   

12.
By applying multitaper methods and Pearson test on the surface air temperature and flare index used as a proxy data for possible solar sources of climate-forcing, we investigated the signature of these variables on middle and high latitudes of the Atlantic–Eurasian region (Turkey, Finland, Romania, Ukraine, Cyprus, Israel, Lithuania, and European part of Russia). We considered the temperature and flare index data for the period ranging from January 1975 to the end of December 2005, which covers almost three solar cycles, 21st, 22nd, and 23rd.We found significant correlations between solar activity and surface air temperature over the 50–60° and 60–70° zones for cycle 22, and for cycle 23, over the 30–40°, 40–50°, and 50–60° zones.The most pronounced power peaks for surface air temperature found by multitaper method are around 1.2, 1.7, and 2.5 years which were reported earlier for some solar activity indicators. These results support the suggestion that there is signature of solar activity effect on surface air temperature of mid-latitudes.  相似文献   

13.
Measurements of both broadband and spectral UV radiation have been carried out at Lhasa (29°40′N, 91°08′E, 3648 m above sea level) on the Tibetan Plateau, using a moderate bandwidth filter instrument (NILUV) and a Fixed Imaging Compact Spectrometer (FICS). In this paper, the erythemal UV dose rates deduced from broadband measurements during the period from 1 July 1996 to 10 December 1997 are presented. The observed highest erythemal UV dose rate is 500 (or 458) mW/m2 in July 1996 (or 1997), and the corresponding daily erythemal UV dose can reach up to 7.60 (or 7.00) kJ/m2 and 9.18 (or 8.96) kJ/m2, respectively, for the monthly mean and the monthly maximum. Comparisons with the UV levels at other locations at similar latitudes show that both the monthly mean and monthly maximum erythemal UV doses at Lhasa can be higher by a factor of 1.3–1.5 than those at San Diego (32°05′N, 117°1′W) in summer (from May to August), and exceed the corresponding values at Perth (32°0′S, 115°8′E) in the southern hemisphere summer (from November to February) by a factor of 1.2–1.4. Comparisons of both the broadband measurements and spectral measurements with the outputs of a discrete ordinate method (DOM) radiative transfer model have also been conducted. The results from the comparisons of broadband measurements with model outputs show that a 15, 11 and 10% agreement may be achieved around solar noon (with solar zenith angle smaller than 60°), respectively, for global irradiances in the 305, 320 and 340 mm channels, whilst the corresponding agreements are about 8 and 4% for the erythemal UV dose rate and the 340–305 nm ratio, respectively. The comparisons of the measured spectral irradiance with model calculations indicate that large discrepancies may appear at wavelengths shorter than 310 nm and longer than 380 nm. However, a 10% agreement may be generally achieved in UVA for solar zenith angle lower than 55°C. The corresponding agreement is about 20 and 5%, respectively, for UVB and the erythemal UV dose rate.  相似文献   

14.
The effect of the 11-year solar cycle on the response of the stratospheric geopotential height and temperature fields at 10 and 30 hPa in winter to solar activity oscillations with periods related to the period of the Sun’s rotation (27.2 days) is discussed, applying methods of statistical spectral analysis to daily data for the period from 1965 to 1996. Atmospheric responses for three periodicities — 27.2 days (period of the Sun’s rotation), 25.3 days (periodicity caused by the modulation of the 27.2 days oscillation by annual atmospheric variation), and 54.4 days (doubled period of the solar rotation) — are studied. A significant effect of the 11-year solar cycle on the atmospheric response to the 27.2 days solar periodicity has not been found. We explain it by a frequency shift of the response from the 27.2 days to the 25.3 days periodicity via amplitude modulation. For the 25.3 days oscillation, prominent differences between the maximum and minimum of the 11-year solar cycle have been found in the coherence between the 10.7 cm solar radio flux and the height/temperature fields: the relationships are stronger at solar maximum than at the minimum of the 11-year cycle. The same differences, but to a greater extent, are revealed for the oscillation with a period of 54.4 days. Coherence and amplitude estimates for this doubled solar rotation periodicity exhibit strong differences between extrema of the 11-year solar cycle. Phase estimates also demonstrate a clear difference between high and low solar activity: on the average, the delay of the atmospheric response after the solar signal is smaller at solar maximum than at solar minimum. Thus, we conclude that the mechanism of the influence of the 11-year solar cycle on the winter middle stratosphere can include both a direct effect of the frequency corresponding to the doubled solar rotation periodicity and an indirect effect of modulation of the intensity of the interaction between the solar 27.2 days oscillation and seasonal atmospheric variations.  相似文献   

15.
The instrumental observations of geomagnetic variations in the middle latitudes are analyzed. The main periodicities are revealed in the background local variations of the magnetic field of the Earth. Besides the 27–29-day variations, which are associated with the rotation of the Sun around its axis, also the harmonic components with periods of ～1, 6–8, 13–14, 57–60 days, and about a year are identified. It is shown that the periodicities in the background variations are both regular and sporadic. The peculiarities in the time behavior of some spectral components of geomagnetic variations are established.  相似文献   

16.
In several xenolithic ultramafic rocks from the Kola Peninsula, including a magnetic separate, abnormally high40Ar/39Ar ratios persisted at low and high temperatures. The lowest40Ar/39Ar ratio was consistently observed at intermediate temperatures (900–1100°C), indicating an apparent age of 2.8–3.1 b.y.; however, this may not indicate the formation age.The quantity of excess40Ar was estimated at each temperature fraction, adopting ages inferred from published Rb-Sr ages or the minimum40Ar/39Ar age. Excess40Ar is abundantly trapped both in mineral lattices and nonretentive trapping sites, but the trapping sites are different from those of in-situ radiogenic40Ar. The high temperature component of excess40Ar is considered to represent Ar dissolved during mineral formation in the upper mantle or the lower crust.A correlation between the amount of high temperature excess40Ar and36Ar exists for some samples. The40Arexcess/36Ar ratios of the rocks of probable upper mantle or lower crust origin vary from about 10 000 to 35 000, which may suggest large fluctuations of this ratio in the deep interior of the earth. The high value implies that most36Ar was already degassed from the earth's interior at least 2 or 3 b.y. ago.  相似文献   

17.
We report on the recent studies on the long-term influence of cosmic rays on the Earth's environment. While on short time-scales solar activity is the driver for atmospheric changes suspected to be due to cosmic rays, for long time-scales the heliosphere, i.e. the circumsolar region occupied by the expanding part of the Sun's atmosphere, has to be considered. The heliosphere is identified as an important shield against interstellar influences and hazards. It has been demonstrated by quantitative modelling that a change of the interstellar medium surrounding the heliosphere as a result of the Sun's quasi-Keplerian motion around the galactic center triggers significant changes of planetary environments caused by enhanced fluxes of neutral atoms as well as by the increased cosmic ray fluxes. We give a compilation of recent space science results of interest to the atmospheric science community.  相似文献   

18.
The properties of turbulent fluctuations of the solar wind plasma near the interplanetary shock observed at September 12, 2014 by the BMSW instrument are considered. The spectra of the density fluctuations in the solar wind and their statistical characteristics up-and downstream of the shock front are analyzed. They are compared with each other and with characteristics corresponding to different turbulence models. It is shown that the spectral and statistical characteristics of the density fluctuations in the solar wind conserve their basic properties after the arrival of an interplanetary shock. Intermittency is observed both before and after the front, but its level increases on average in the second case. In both regions, the scaling of the structure functions of the density fluctuations in the solar wind differ from the scaling of the classical Kolmogorov model and can be described by the log-Poisson turbulence model. Parameterization of the scaling of the structure functions revealed the presence of filamentary structures in the solar wind plasma, which provide the density intermittency in the studied space regions.  相似文献   

19.
This article is a continuation of the previous one considering the evolution of a long-period comet. The changes of the local radius and the moment of inertia as well as the orientation of the rotation axis are calculated. With reference to the previous model, the time-dependent orbital parameters are introduced. The procedure of sublimation-driven evolution is implemented to the comets 67P/Churyumov-Gerasimenko, 9P/Tempel 1, and 81P/Wild. The inclination of the rotation axis of Comet Ch-G is calculated. The position of the rotation axis is a result of the best fit of the water production rate curve received from modelling to the observational water production rate curve. The method is verified through application to Comets 9P/Tempel 1 and 81P/Wild with well-known positions of the rotation axes. The best fit is for inclination of the rotation axis which is close to the position of the rotation axis with minimum energy (maximum of the moment of inertia). For the best fitted position of the rotation axis I = 90° and Φ = 60°, the largest decrease of radius was about 5.6 m in the northern polar region. The smallest decrease of radius, of about 0.3 m, was noticed on cometographic latitudes between 39° and 46°.  相似文献   

20.
The thermoluminescence (TL) levels of 45 ordinary chondrites were measured to obtain information about the meteorite orbits. The low-temperature TL reaches equilibrium while the meteorite is in space and reflects the temperature of the meteorite at perihelion. Samples of Pribram, Lost City, and Innisfree, whose orbits are accurately known, were used as control samples. The TL levels in 40 out ot 42 meteorites are similar to the three control samples, indicating that the vast majority of ordinary chondrites that survive atmospheric entry have perihelia similar to three known orbits, i.e., in the range 0.8–1 AU. The effects of albedo and rotation are also considered. A simple model indicates that temperature gradients of 1–2°K/cm are possible in slowly rotating meteoroids and such a temperature gradient is consistent with the unusually large TL gradient measured in the Farmville meteorite. Since slow rotation rates are improbable, other possibilities are examined but no satisfactory explanation has been found. The TL level measured in the Malakal meteorite is two orders of magnitude lower than control samples and is best explained by thermal draining due to solar heating in an orbit with a small perihelion distance. The perihelion is estimated to be～0.5–0.6AU.  相似文献   

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