A solar pattern in the longest temperature series from three stations in Europe

We analyze the longest temperature series from Prague, Bologna and Uccle. We partition daily minimum and maximum temperatures and their differences in two subsets as a function of high vs low solar activity, using the superimposed epochs method. Differences display patterns with significant amplitudes and time constants ～3 months. These are recognized in all stations and are stable against a change in the analyzed period. Amplitude of variations is ～1 °C. Differences between average annual values corresponding to high vs low activity periods are also ～1 °C. Solar activity may account for these long-term temperature variations. These variations also present local characteristics, which may render identification of a global correlation delicate. We discuss possible physical mechanisms by which solar variation could force climate changes (e.g. through solar activity itself, the EUV part of the solar flux, cosmic rays, the downward ionosphere-earth current density, etc.).     

A possible long-term solar impact on air temperature in relation to solar motion

Summary Using the long-term relations between solar motion and solar activity, long-term relations between solar activity and air temperature variations on the Earth's surface have been studied. A long-term periodicity in the period range from 25 to 250 years, corresponding to the periodicity of solar motion and solar activity, has been found in four very long European surface air temperature series. The positions of the spectral peaks approximately obey the relation p_i=178.7/i, i=1, 2, ... . Similar long-term patterns of solar and geomagnetic activity and of global surface air temperature have been found in the years 1861 to 1990. The results indicate that the solar activity impact on the climate could be significant, and that the prolonged minimum of solar activity, predicted from solar motion for the next 2 – 3 decades, could decreace global air temperatures.     

On possible drivers of Sun-induced climate changes

We tested the validity of two current hypotheses on the dependence of climate change on solar activity. One of them states that variations in the tropospheric temperature are caused directly by changes of the solar radiance (total or spectral). The other suggests that cosmic ray (CR) fluctuations, caused by the solar/heliospheric modulation, affect the climate via cloud formation. Confronting these hypotheses with seven different sets of the global/hemispheric temperature reconstructions for the last 400 years, we found that the former mechanism is in general more prominent than the latter. Therefore, we can conclude that in so far as the Sun–climate connection is concerned tropospheric temperatures are more likely affected by variations in the UV radiation flux rather than by those in the CR flux.     

Evidence for solar forcing in variability of temperatures and pressures in Europe

Daily temperature and pressure series from 55 European meteorological stations covering the 20th century are analyzed. The overall temperature mean displays a sharp minimum near 1940 and a step-like jump near 1987. We evaluate the evolution of disturbances of these series using mean squared inter-annual variations and “lifetimes”. The decadal to secular evolutions of solar activity and temperature disturbances display similar signatures over the 20th century. Because of heterogeneity of the climate system response to solar forcing, regional and seasonal approaches are key to successful identification of these signatures. Most of the solar response is governed by the winter months, as best seen near the Atlantic Ocean. Intensities of disturbances vary by factors in excess of 2, underlining a role for the Sun as a significant forcing factor of European atmospheric variations. We speculate about the possible origin of these solar signatures. The last figure of the paper exemplifies its main results.     

Solar and geomagnetic activity effects on climate at regional and global scales: Case study—Romania

We analyze 100–150 years-long temperature and precipitation records from 14 meteorological stations in Romania, in connection with long-term trends in solar and geomagnetic activities. The comparison of solar (sunspot number) and geomagnetic (aa index) parameters with the mean air temperature over the Romanian territory, at interdecadal timescales, shows positive correlation coefficients, while the comparison with the mean precipitation shows negative correlation coefficients. The correlation of climatic parameters seems to be stronger for geomagnetic activity than for solar activity. The Romanian temperature series are examined in the context of other European stations and of averages on the European, northern hemisphere, and global scale, respectively. Long-term (interdecadal and centennial) trends and differences between local trends and average trends for larger areas are discussed. The study indicates that solar and geomagnetic activity effects are present on the 22-year Hale cycle timescale. The temperature variation on this timescale lags the solar/geomagnetic ones by 5–9 years.     

Solar–geomagnetic activity and Aa indices toward a standard classification

Legrand and Simon [1989. Solar cycle and geomagnetic activity: a review for geophysicists. Part I. The contributions to geomagnetic activity of shock waves and of the solar wind. Annales Geophysicae 7(6), 565–578] classified one century (1868–1978) of geomagnetic activity, using the Mayaud's Aa index, in four classes related to solar activity: (1) the magnetic quiet activity due to slow solar wind flowing around the magnetosphere, (2) the recurrent activity related to high wind speed solar wind, (3) the fluctuating activity related to fluctuating solar wind and (4) the shock activity due to shock events (CME). In this paper, we use this classification to analyse the solar–geomagnetic activity from 1978 to 2005. We found that during the last three decades the level of geomagnetic quiet activity estimated by Aa indices is decreasing: 2003 is the year of the smallest level of quiet geomagnetic activity since 1868. We compare Legrand and Simon's classification with new in situ solar wind data [Richardson, I.G., Cliver, E.W., Cane, H.V., 2000. Sources of geomagnetic activity over the solar cycle: relative importance of coronal mass ejections, high-speed streams, and slow solar wind. Journal of Geophysical research 105(A8), 18,200–18,213; Richardson, I.G., Cane, H.V., 2002. Sources of geomagnetic activity during nearly three solar cycles (1972–2000). Journal of Geophysical Research 107(A8), 1187] and find a rather good agreement. The differences are only due to minor definitions of the extent of the classes. An attempt is made at defining a more precise standard classification of solar phenomena and at defining time scales of these to understand more precisely the geomagnetic signatures of solar activity.     

Characterization of low latitude GPS-TEC during very low solar activity phase

We present the mean diurnal, seasonal and annual variations in TEC during the lowest solar activity phase from low latitude Indian zone recorded at Udaipur (Geog. Lat. 24.6°N, Geog. Long.73.7°E, Geomag. Lat. 15.6°N) using a GPS receiver. Seasonal variations in daytime TEC show a semiannual periodicity, with a minimum in winter. Results of seasonal variations have been compared with that of the IRI-2007 model. Model calculations reveal significant seasonal as well as longitudinal differences in TEC. Seasonal variations in the nighttime TEC reveal an annual periodicity. Near the crest of the EIA, TEC shows a very good correlation with the solar flux. The results also point to weakening of the anomaly crest as well as its spatial and temporal contraction with declining solar activity.     

Network analysis methods of heliorelated time series

In this work, we present the diagnostics results of the similarity between different temperature paleoreconstructions using network approaches. The correlation patterns of time series are transformed into the geometry of the corresponding graph, which can be analyzed geometrically. To detect a possible nonlinear connection between climatic series and solar activity, we use networks constructed by embedding time series in the space of an appropriate dimension. Finally, we present Markov networks for climatic reconstructions and annual Wolf numbers.     

Influence of climatic factors on the past atmospheric content of the C-14 isotope

Reconstructions of solar activity in the past epochs based on information on the past atmospheric content of the cosmogenic ¹⁴C isotope are nowadays actively discussed. The ¹⁴C isotope is generated in the atmosphere of the Earth under the influence of cosmic rays, and its concentration in annual tree rings carries information on the past solar activity. However, the concentration of this isotope in annual tree rings may also be influenced by climatic factors. In the present work, the possible correlation between variations in the ¹⁴C atmospheric content and in the Earth’s global temperature from the late 14th century to the middle of the 19th century is studied. It is shown that variations in global temperature may produce changes in the ¹⁴C atmospheric content and consequently have to be taken into account in reconstructions of the past solar activity.     

北京地区上空OH转动温度的季节性变化

在北京东北方向的兴隆天文台,自主搭建的大气辐射观测仪器对OH夜气辉从2011年12月开始进行观测.利用高分辨率的OH(8-3)带的振转光谱计算了转动温度,并与TIMED/SABER探测的温度进行了比较.观测表明,两年(2012—2013)的OH(8-3)带转动温度平均值为203.0±11.2K,有明显的季节变化,冬季高,夏季低,温差可达60K.与SABER观测温度的季节变化一致.对日平均的转动温度进行年振荡和半年振荡分量的拟合分析表明,年振荡强度(10.8K)远大于半年振荡(2.7K).研究还发现,不同夜晚转动温度变化形态差别很大,既有很强的潮汐控制的波动,又有相对短周期的波动.     

Simulations of lunar equatorial regolith temperature profile based on measurements of Diviner on Lunar Reconnaissance Orbiter

Lunar equatorial regolith temperature profiles were simulated using the half-limited solid heat conduction model. Based on the infrared data measured using the Diviner radiometer on the Lunar Reconnaissance Orbiter launched by the United Sates in June 2009, three factors influencing temperature profiles were analyzed. The infrared brightness temperature data from Diviner channel 7 were used to retrieve surface temperature. In simulating regolith temperature profiles, the retrieved temperature, rather than temperatures calculated from solar radiance at the lunar surface, were used as the input for surface temperature in solving the heat-conductive equation. The results showed that the bottom-layer temperature at depths of 6 m approached almost 246 K after 10000 iterations. The temperature was different to the temperature of 250 K at the same depth encountered in simulations using solar radiance. Simulations from both methods of surface temperatures over a lunar day gave similar variations. At lunar night, the temperature difference between the two was about 2 K; the main differences occurred when the solar elevation angle was very low when surface temperatures are largely affected by terrain topography. With no certainty in lunar temperature profiles at present, the advantage of the retrieval method using infrared sensor data as input to the boundary conditions in solving the lunar heat conduction equation is that simulations of surface temperature variations are more accurate. This is especially true in areas with large variations in terrain topography, where surface temperatures vary greatly because of shading from the sunlight.     

Latitude dependency of solar flare index–temperature relation occuring over middle and high latitudes of Atlantic–Eurasian region

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.     

The 11-year solar cycle,the sun’s rotation,and the middle stratosphere in winter: Part I: Response of zonal means

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.     

Transition of solar cycle length in association with the occurrence of grand solar minima indicated by radiocarbon content in tree-rings

In this paper, we review the variation of the 11-year solar cycle since the 15th century revealed by the measurement of radiocarbon content in single-year tree-rings of Japanese cedar trees. Measurements of radiocarbon content in absolutely dated tree-rings provide a calibration curve for accurate dating of archaeological matters, but at the same time, enable us to examine the variations of solar magnetic activity in the pre-historical period. The Sun holds several long-term quasi-cyclic variations in addition to the fundamental 11-year sunspot activity cycle and the 22-year polarity reversal cycle, and it is speculated that the property of the 11-year and the 22-year solar cycle varies in association with such long-term quasi-cycles. It is essential to reveal the details of solar variations around the transition time of solar dynamo for illuminating the mechanisms of the long-term solar variations. We therefore have investigated the property of the 11-year and 22-year cycles around the two grand solar minima; the Maunder Minimum (1645–1715 AD) and the Spoerer Minimum (1415–1534 AD), the periods of prolonged sunspot minima. As a result, slight stretching of the “11-year” and the “22-year” solar cycles was found during these two grand solar activity minima; continuously during the Maunder Minimum and only intermittently during the Spoerer Minimum. On the contrary, normal or slightly shortened 11-year cycles were detected during the interval period of these two minima. It suggests the inverse correlation between the solar cycle length and solar magnetic activity level, and also the change of meridional flow during the grand solar activity minima. Further measurements for the beginning of the grand solar minima will provide a clue to the occurrence of such prolonged sunspot disappearance. We also discuss the effect of solar variations to radiocarbon dating.     

Solar activity imprints in tree ring width from Chile (1610–1991)

We have investigated the solar activity signal in tree ring data from two locations in Chile. The tree ring time series extended over a period of ∼400 yr. Spectral and wavelet analysis techniques were employed. We have found evidence for the presence of the solar activity Schwabe (∼11 yr), Hale (∼22 yr), fourth-harmonic of the 208-yr Suess cycle (∼52 yr) and Gleissberg (∼80 yr) cycles. The Gleissberg cycle of tree ring data is in anti-phase with solar activity. Wavelet and cross-wavelet techniques revealed that the periods found are intermittent, possibly because solar activity signals observed in tree rings are mostly due to solar influence on local climate (rainfall, temperature, and cloud cover) where trees grow up. Further, cross-wavelet analysis between sunspot and tree ring time series showed that the cross power around the 11 yr solar cycle is more significant during periods of high solar activity (grand maximum) than during periods of low solar activity (grand minimum). As Glaciar Pio XI is practically at the Pacific Ocean level, the tree-ring response may be stronger due to the heating of the Pacific Ocean water following an increase of the solar radiation incidence rather than at the higher altitudes of Osorno region.     

Episodes of relative global warming

Solar activity is regulated by the solar dynamo. The dynamo is a non-linear interplay between the equatorial and polar magnetic field components. So far, in Sun–climate studies, only the equatorial component has been considered as a possible driver of tropospheric temperature variations. We show that, next to this, there is a significant contribution of the polar component. Based on direct observations of proxy data for the two main solar magnetic fields components since 1844, we derive an empirical relation between tropospheric temperature variation and those of the solar equatorial and polar activities. When applying that relation to the period 1610–1995, we find some quasi-regular episodes of residual temperature increases and decreases, with semi-amplitudes up to ～0.3 °C. The present period of global warming is one of them.     

Four decades of geomagnetic and solar activity: 1960–2001

We analyze the relationship between some space weather indices (Dst, Ap, F10.7) and geomagnetic effects on the regional (European) scale, over the period 1960–2001. The remaining external field signal (RES) detected in the Northward magnetic component of the European observatory annual means are used as an indicator of the regional geomagnetic activity. Relationship RES-F10.7 suggests correction factors for getting the geomagnetic annual means of the Northern component less affected by the external sources. We have found some time lags among investigated parameters. These delays may suggest that the Ap responds to the solar activity in a differently than Dst and RES, Ap being more sensitive to the high-speed streams (HSS) and the Alfvenic waves present in HSS, while Dst and RES being more influenced by the coronal mass ejections activity (CME).     

Modelling the Northern Hemisphere temperature for solar cycles 24 and 25

It is uncertain whether the solar cycle 24 will have a high or a low sunspot maximum number. In its last revision the Solar Cycle 24 Prediction Panel indicates that the low prediction is the most likely. Also, solar cycle 25 is considered to present an equal or lower activity than cycle 24. In order to assess the possible effect of the solar activity on temperature, in the present work we attempt to model the tendency of the Northern Hemisphere temperature for the years 2009–2029, corresponding to solar cycles 24 and 25, using a thermodynamic climate model. We include as forcings the atmospheric carbon dioxide (CO₂) and the solar activity by means of the total solar irradiance, considering that the latter has not only a direct effect on climate, but also an indirect one through the modulation of the low cloud cover. We use two IPCC-2007 CO₂ scenarios, one with a high fossil consumption and other with a low use of fossil sources. Also we consider higher and lower solar activity conditions. We found that in all the performed experiments the inclusion of the solar activity produces a noticeable reduction in warming respect to the IPCC-2007 CO₂ scenarios. Such reduction goes between ～14% and ～44%. In order to evaluate the efficiency of the TCM, we use the root mean square (RMS) between the observed and model temperatures for the period 1980–2003. We find that the RMS for the experiment using the CO₂ as the only forcing is 0.06 °C,while for the experiment that includes also the solar activity it is higher, 0.13 °C.     

Long-term variations of the solar-geomagnetic correlation,total solar irradiance,and northern hemispheric temperature (1868–1997)

Time series for annual means of sunspot numbers, aa-indices of geomagnetic activity and annual numbers of 3-h time intervals with different values of aa-indices (aa≤4 and aa≥30) from 1868 to 1997 have been examined by the method of running-window cross-correlation analysis. It has been found that the solar-geomagnetic correlation varies over time. In particular, long-term variations of the 23-year running correlation appear to have a quasi periodicity of about 40–50 years, superposed on a linear trend, where the trend describes a general decrease of the 23-year running-window correlation between 1868 and the present. Long-term variations of the solar-geomagnetic correlation may result from the quasi-periodic fluctuations of the time lag of geomagnetic indices relative to sunspot numbers, superposed on an upward linear trend of time lag. Secular variations of the northern hemisphere land-air surface temperature anomalies and two solar indices that are potential proxy measures for the total solar irradiance (i.e., the length of the sunspot cycle and the Hoyt and Schatten (Hoyt, D.V., Schatten, K.V., 1993. Journal of Physical Research 98, 18,895–18,906.) composite index) have been compared with the long-term variations of the solar-geomagnetic correlation. The extremum points (points where the derivative vanishes to zero) of these variations are found to occur contemporaneously during the periods of low solar-geomagnetic correlation, suggesting, perhaps, that the long-term variations of solar-geomagnetic correlation are due to some long-term processes on the Sun and that they have a measurable effect on the Earth.     

极区电离层F2层峰值电子浓度对太阳活动依赖性的共轭研究

本文利用南极中山站(ZHS),以及北极与其地理共轭的Tromso站(TRO)、地磁共轭的Longyearbyen站(LYB)各自约一个太阳活动周的观测数据,对比分析了极区电离层F₂层峰值电子浓度(N_mF₂)对太阳活动的依赖性.结果表明,三个台站N_mF₂月中值随修正太阳10.7 cm通量指数F_10.7P(简称P)增大在总体上呈线性增长,这说明在这三个台站,太阳辐射仍是其F₂层主要电离源.其中TRO站N_mF₂与P线性关系最好,ZHS站的次之,LYB站的最差.在日变化中,TRO站N_mF₂对太阳活动响应最为敏感的时刻出现在地方时中午附近,LYB站出现在磁中午,ZHS站则出现在地方时中午和磁地方时中午之间.这主要是由地理/地磁纬度差异引起的不同强度的光致电离与极区等离子体对流共同作用的结果.在年变化中,TRO站N_mF₂随太阳活动变化上升最快的季节出现在冬季,夏季上升最慢.在ZHS站与LYB站,N_mF₂对太阳活动变化的响应都在两分季最为敏感.这种季节上的差异则是由于三个台站光致电离与中性大气成分R[O/N₂]的不同所致.