Relationships between the North Pacific Oscillation and the typhoon/hurricane frequencies

Relationships between the North Pacific Oscillation (NPO) and the typhoon as well as hurricane fre-quencies are documented. The correlation between NPO index in June-July-August-September and the annual typhoon number in the western North Pacific is 0.37 for the period of 1949―1998. The NPO is correlated with the annual hurricane number in the tropical Atlantic at -0.28 for the same period. The variability of NPO is found to be concurrent with the changes of the magnitude of vertical zonal wind shear, sea-level pressure patterns, as well as the sea surface temperature, which are physically asso- ciated with the typhoons and hurricanes genesis. The NPO associated atmospheric circulation vari- ability is analyzed to explain how NPO is linked with variability of the tropical atmospheric circulation in the western Pacific and the tropical Atlantic, via the atmospheric teleconnection.     

>0.3 MeV高能电子注入辐射带槽区事件的分析与预报

本文利用低高度太阳同步轨道系列卫星NOAA/POES从1996年到2006年的>0.3 MeV高能电子观测数据,分析了>0.3 MeV高能电子注入辐射带槽区的特征,研究了注入槽区事件与行星际条件、太阳活动和地磁扰动之间的联系.研究表明>0.3 MeV高能电子注入辐射带槽区事件与磁暴的发生密切相关,注入事件的发生与太阳活动的强度有一定的相关性.在此研究的基础上,本文通过分析辐射带槽区>0.3 MeV高能电子通量和Dst指数的相关性,提出了利用Dst指数推算辐射带槽区>0.3 MeV高能电子通量的方法,继而给出了可行的辐射带槽区高能电子辐射环境的预警模式.     

Statistical study on great geomagnetic storms during solar cycle 23

Characteristics of great geomagnetic storms during solar cycle 23 were statistically investigated. Firstly, we focused on the uniqueness of solar cycle 23 by analyzing both the great storm number and sunspot number from 1957 to 2008. It was found that the relationship between the sunspot number and great storm number weakened as the activity of the storms strengthened. There was no obvious relationship between the annual sunspot number and great storm number with Dstxi≤-300 nT. Secondly, we studied the relationship between the peak Dst and peak Bz in detail. It was found that the condition Bz≤-10 nT is not necessary for storms with Dst≤-100 nT, but seems necessary for storms with Dst≤-150 nT. The duration for Bz≤-10 nT has no direct relationship with the giant storm. The correlation coefficient between the Dst peak and Bz peak for the 89 storms studied is 0.81. After removing the effect of solar wind dynamic pressure on the Dst peak, we obtained a better correlation coefficient of 0.86. We also found the difference between the Dst peak and the corrected Dst peak was proportional to the Dst peak.     

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.     

行星际扰动对地磁活动的影响

利用第23太阳活动周中WIND和ACE资料,统计分析行星际扰动对不同水平地磁活动的影响,研究磁暴强度与不同行星际参数之间的相关性,结果发现:①从长期来看,地磁活动指数Dst与太阳风速度的相关性最好,相关性在太阳活动谷年时最高;②多磁暴时序叠加结果证实了导致小、中、强磁暴开始的经验行星际南向磁场条件,磁暴过程中行星际磁场...     

Generation of the Katrine hurricane during the geomagnetic extrastrom at crossing of the heliospheric current sheet: Is it an accidental coincidence or physical essence?

Attention is paid to the generation of the Katrine hurricane with destructive consequences during the geomagnetic extrastorm of August 24, 2005, at a repeated crossing of the strongly disturbed IMF sector boundary. This fact is discussed in the light of the Eigenson-Usmanov hypothesis that solar activity can affect generation of hurricanes. According to the law of enhancement, solar activity and corresponding geomagnetic disturbances increase baric contrasts in the lower atmosphere over oceans on the Earth’s dayside hemisphere and decrease background pressure at tropical latitudes. It has been assumed that this can be one of the factors facilitating triggering of the positive feedback mechanisms necessary for generation and maintenance of hurricanes according to the Golitsyn [1999] model.     

Relationships between the AE, ap and Dst indices near solar minimum (1974) and at solar maximum (1979)

Three-hourly average values of the Dst, AE and ap geomagnetic activity indices have been studied for 1 years duration near the solar minimum (1974) and also at the solar maximum (1979). In 1979 seven intense geomagnetic storms (Dst < –100 nT) occurred, whereas in 1974 only three were reported. This study reveals: (1) the yearly average of AE is greater in 1974 than in 1979, whereas the inverse seems to be true for the yearly average of Dst, when a higher number of intense storms is present. These averages indicate the kind of activity occurring on the sun as shown in earlier work. (2) The seasonal variation of Dst is higher than that of ap and is almost negligible in AE. (3) The correlation coefficient of ap × AE is in general the highest, as the magnetometers that monitor both indices are close, and is surpassed only by the ap × Dst correlation during geomagnetic storms, when the influence of the ring current is dominant. The correlation of ap × Dst also shows a seasonal variability. (4) For the first time a study of correlation between ap and a linear combination of AE and Dst has also been made. We found higher correlation coefficients in this case as compared to those between ap × Dst and ap ×xs AE.     

Identifying non-stationary and long-term river–aquifer interactions as a response to large climatic patterns and anthropogenic pressures using wavelet analysis (Mancha Oriental Aquifer,Spain)

The objective of this study was to analyse periodicities and the long-term variability of monthly Júcar River–Mancha Oriental Aquifer interactions (RAI) and regionally measured precipitation (PP) with special focus on the correlations between these local hydrological variables and the large climatic patterns governing the Iberian Peninsula, represented by their teleconnection indices – the North Atlantic Oscillation index (NAOi) and the Western Mediterranean Oscillation index (WeMOi). To that end, wavelet analysis has been applied since it not only provides insight into the time-series dynamics but also permits statistical interpretation and correlation analysis. As a result, several periodicities have been detected: intermittent semi-annual periodicity in PP and the NAOi and annual periodicity in the RAI, NAOi and WeMOi time series. Long cycles (approximately 14 years) are also observed in the PP and WeMOi time series. The cross-wavelet spectra show a correlation between the RAI and the rest of the variables on the semi-annual and the annual scales, while wavelet coherence detects common behaviour with longer cycles – 5–6 years between the NAOi and the RAI and cycles of both 1–5 years and 7–10 years between PP and the RAI. Furthermore, results show that the periodicities in the teleconnection indices and precipitation propagate into the RAI with certain lead times: 3 months between the RAI and PP and 6 months between the RAI and the NAOi. The results indicate that the detected periodicities and the coherence between the studied variables could have applications in strategic planning on a river basin scale, taking into account the propagation times and the frequency scale. This methodological approach can be applied into strategic water resource planning independently of the geographical location of the hydrogeological system, the basin size and the climate region.     

Changes in geomagnetic activity and global temperature during the past 40 years

The purpose of this study is to investigate the effect of geomagnetic activity (used as a measure of solar wind parameters) on the variability of large-scale climate patterns and on changes in the global temperature. We show that positive statistically significant correlations between global temperature and the distribution of surface temperature over Eurasia, the East and Equatorial Pacific and over the North Atlantic for the period 1966?C2009 correspond to large-scale climate patterns defined by climate indices. We found very similar positive correlations between geomagnetic activity and the distribution of surface temperature in the mentioned regions. As an effect of geomagnetic storms, energetic particles penetrate from the magnetosphere into the region of the stratospheric polar vortex. The increase of temperature and pressure can be observed over northern Canada. The vortex shifts towards Europe, rotates counter-clockwise and the wind blows from the polar region over Greenland southwards. It diverts the warm flow proceeding northward over the Atlantic, eastward along the deep Icelandic low extending as far as the Barents Sea and takes part in warming Eurasia. The strengthened zonal flow from Siberia cools the western Pacific with the impact on the warming of the equatorial and eastern Pacific when also a distinct 1976?C78 climate shift occurred. Processes in the Atlantic and Pacific play a significant role and a time delay (wind forcing over the previous 1?C4 yr) appears to be the most important for the relocation of the oceanic gyres. Results showing statistically significant relations between time series for geomagnetic activity, for the sum of climate indices and for the global temperature help to verify findings concerning the chain of processes from the magnetosphere to the troposphere.     

Thunderstorm activity dynamics during hurricanes

Results of studying the thunderstorm activity dynamics during the Pacific hurricanes in August and October 2001, using broadband recording of the time forms of atmospherics on Kamchatka, have been presented. The number of atmospherics per minute at simultaneously determined azimuths of their sources has been used as an example of thunderstorm activity. An analysis of data processing results has indicated (a) in the absence of hurricanes, the maximal atmospheric flux level (10 ± 4 pulse/min) was observed at night, and the daylight level was 3 ± 1 pulse/min; (b) thunderstorm activity increases at the stage of tropical depression regardless of depression development into hurricane; in this case the flux of atmospherics can increase to 250 pulse/min at night and can be widely variable (5–100 pulse/min) in daytime; (c) in the sate of hurricane maturity, the thunderstorm activity level is not higher than the background level. It has been indicated that IGWs in the Earth’s atmosphere and the lower ionosphere are caused by lightning strokes accompanied by shock waves during expansion of the lighning channel. The results obtained are of interest in studying anomalous effects in the natural electromagnetic field in the VLF band during increased seismic activity on Kamchatka.     

North Atlantic Oscillation influences on Turkish lake levels

The North Atlantic Oscillation (NAO) is a large‐scale mode of natural climate variability governing the path of Atlantic mid‐latitude storm tracks and precipitation regimes in the Atlantic and Mediterranean sectors. The primary focus of this study is to investigate the variability of lake levels in seven lakes scattered across Turkey using the method of continuous wavelet transforms and global spectra. The long winter (December, January, February and March) lake‐level series and the NAO index (NAOI) series were subjected to wavelet transform. The global wavelet spectrum (energy spectrum of periodicities) of lake levels and winter NAOI anomalies, in most cases, revealed a significant correlation. It was shown that the Tuz, Sapanca, and Uluabat lakes reflect much stronger influences of the NAO than the other four lakes. In contrast, weak correlations were found in the coastal areas of the Mediterranean and eastern Turkey. The periodic structures of Turkish lake levels in relation to the NAO revealed a spectrum between the 1‐year and 10‐year scale level. Although the periodicities of more than 10‐year scale levels were detected, explaining significant relations between the NAO and these long‐term periodicities remains a challenging task. The results of this study are consistent with the earlier studies concerning the teleconnection between the NAO and climate variables in Turkey. Copyright © 2009 John Wiley & Sons, Ltd.     

On the interaction between a hurricane,the Gulf Stream and coastal sea level

Tropical storms and hurricanes in the western North Atlantic Ocean can impact the US East Coast in several ways. Direct effects include storm surges, winds, waves, and precipitation and indirect effects include changes in ocean dynamics that consequently impact the coast. Hurricane Matthew [October, 2016] was chosen as a case study to demonstrate the interaction between an offshore storm, the Gulf Stream (GS) and coastal sea level. A regional numerical ocean model was used, to conduct sensitivity experiments with different surface forcing, using wind and heat flux data from an operational hurricane-ocean coupled forecast system. An additional experiment used the observed Florida Current (FC) transport during the hurricane as an inflow boundary condition. The experiments show that the hurricane caused a disruption in the GS flow that resulted in large spatial variations in temperatures with cooling of up to ~?4 °C by surface heat loss, but the interaction of the winds with the GS flow also caused some local warming near fronts and eddies (relative to simulations without a hurricane). A considerable weakening of the FC transport (~?30%) has been observed during the hurricane (a reduction of ~?10 Sv in 3 days; 1Sv?=?10⁶ m³ s^?1), so the impact of the FC was explored by the model. Unlike the abrupt and large wind-driven storm surge (up to 2 m water level change within 12 h in the South Atlantic Bight), the impact of the weakening GS on sea level is smaller but lasted for several days after the hurricane dissipated, as seen in both the model and altimeter data. These results can explain observations that show minor tidal flooding along long stretches of coasts for several days following passages of hurricanes. Further analysis showed the short-term impact of the hurricane winds on kinetic energy versus the long-term impact of the hurricane-induced mixing on potential energy, whereas several days are needed to reestablish the stratification and rebuild the strength of the GS to its pre-hurricane conditions. Understanding the interaction between storms, the Gulf Stream and coastal sea level can help to improve prediction of sea level rise and coastal flooding.     

Relation of PC index to the geomagnetic storm Dst variation

Relationships between the polar cap magnetic activity index PC and the magnetic storm Dst index have been studied for the magnetic storms with duration more 12 h and peak value Dst<?30 nT and, observed in 1998–2002 and 2004–2005. Along with PC index the geoeffective interplanetary electric field Em was also examined. It has been found that all examined storms, lying in range from ?30 to ?373 nT, started when the PC index and, correspondingly, the Em field firmly exceeded the threshold >2 mV/m. In particular, the “anomalous” magnetic storm on January 21–22, 2005 occurring under conditions of northward IMF B_Z (Du et al., 2008) is usual phenomena fitted well with the threshold restriction owing to the large IMF By component input. The maximal storm depression (the peak value of Dst) is linearly related to the quantities Em and PC, averaged for the time interval from the storm beginning to the storm maximum. The correlation between Dst and PC is more steady and larger than correlation between Dst and Em, the latter being dependent on Em value (effect of “Dst saturation”). The moment of the firm descent of the Em and PC quantities below the threshold level ～2 mV/m is indicative of the depression damping and transition to the recovery phase. The results are consistent with the similar peculiarities revealed for substorms development (Troshichev and Janzhura, 2009) and support the conclusion that the PC index is a reliable proxy characterizing the solar wind energy having been entered into the magnetosphere.     

第23太阳活动周期太阳风参数及地磁指数的统计分析

日冕物质抛射(Coronal Mass Ejection,简称CME)和共转相互作用区(Corotating Interaction Region,简称CIR)是造成日地空间行星际扰动和地磁扰动的两个主要原因,提供了地球磁暴的主要驱动力,进而显著影响地球空间环境.为深入研究太阳风活动及受其主导影响的地磁活动的时间分布特征,本文对大量太阳风参数及地磁活动指数的数据进行了详细分析.首先,采用由NASA OMNIWeb提供的太阳风参数及地磁活动指数的公开数据,通过自主编写matlab程序对第23太阳活动周期(1996-01-01—2008-12-31)的数据包括行星际磁场Bz分量、太阳风速度、太阳风质子密度、太阳风动压等重要太阳风参数及Dst指数、AE指数、Kp指数等主要的地磁指数进行统计分析,建立了包括269个CME事件和456个CIR事件列表的数据库.采用事例分析法和时间序列叠加法分别对两类太阳活动的四个重要太阳风参数(IMF Bz、太阳风速度、太阳风质子密度、太阳风动压)和三个主要地磁指数(Dst、AE、Kp)进行统计分析,并研究了其统计特征.其次,根据Dst指数最小值确定了第23太阳活动周期内的355个孤立地磁暴事件,并以Dst指数最小值为标准将这些磁暴进一步分类为145个弱磁暴、123个中等磁暴、70个强磁暴、12个剧烈磁暴和5个巨大磁暴.最后,采用时间序列叠加法对不同强度磁暴的太阳风参数和地磁指数进行统计分析.统计分析表明,对于CME事件,Nsw/Pdyn(Nsw表示太阳风质子密度,Pdyn表示太阳风动压)线性拟合斜率一般为正;对于CIR事件,Nsw/Pdyn线性拟合斜率一般为负,这可作为辨别CME和CIR事件的一种有效方法.从平均意义上讲,相较于CIR事件,CME事件有更大的南向IMF Bz分量、太阳风动压Pdyn、AE指数、Kp指数以及更小的Dstmin.一般情况下,CME事件有更大的可能性驱动极强地磁暴.总体而言,对于不同强度的地磁暴,Dst指数的变化呈现出一定的相似性,但随着地磁暴强度的增强,Dst指数衰减的速度变快.CME和CIR事件以及其各自驱动的地磁暴事件有着很多不同,因此,需要将CME事件驱动的磁暴及CIR事件驱动的磁暴分开研究.建立CME、CIR事件及地磁暴的数据库以及获取的统计分析结果,将为深入研究地球磁层等离子体片、辐射带及环电流对太阳活动的响应特征提供有利的帮助.     

Correlation between tropical cyclones and magnetic storms during cycle 23 of solar activity

The correlation between cyclic (11-year) variations in geomagnetic activity and tropical cyclogenesis during the completed solar activity cycle (cycle 23, 1996–2006) is studied. The total number of the semidiurnal intervals, with the mean values of the planetary a _p index not less than 40, for each year and the annual number of cyclones, regardless of their intensity, are used as the characteristics. The correlation coefficients r are calculated for each of the following four cyclogenesis regions: the Atlantic, northeastern and central Pacific, northwestern Pacific, and water areas of oceans and seas in the Southern Hemisphere. The conclusion that the correlation exists between magnetic storms and tropical cyclones in the Atlantic, obtained earlier by Ivanov [2006] on the basis of the data for 1996–2005, is confirmed. It has been found that the linear correlation coefficient r changed in different regions from positive to negative values: 0.55, 0, ?0.50, and ?0.50, respectively.     

Oscillations of galactic cosmic rays and solar indices before the arrival of relativistic solar protons

Using modern wavelet analysis techniques, we have made an attempt to search for oscillations of intensity of galactic cosmic rays (GCR), sunspot numbers (SS) and magnitudes of coronal index (CI) implying that the time evolution of those oscillations may serve as a precursor of Ground Level Enhancements (GLEs) of solar cosmic rays (SCR). From total number of 70 GLEs registered in 1942–2006, the four large events — 23 February 1956, 14 July 2000, 28 October 2003, and 20 January 2005 — have been chosen for our study. By the results of our analysis, it was shown that a frequency of oscillations of GCR decreases as time approaches to the event day. We have also studied a behaviour of common periodicities of GCR and SCR within the time interval of individual GLE. The oscillations of GLE occurrence rate (OR) at different stages of the solar activity (SA) cycle is of special interest. We have found some common periodicities of SS and CI in the range of short (2.8, 5.2, 27 and 60 days), medium (0.3, 0.5, 0.7, 1.3, 1.8 and 3.2 years) and long (4.6 and 11.0 years) periods. Short and medium periodicities, in general, are rather concentrated around the maxima of solar cycles and display the complex phase relations. When comparing these results with the behaviour of OR oscillations we found that the period of 11 years is dominating (controlling); it is continuous over the entire time interval of 1942–2006, and during all this time it displays high synchronization and clear linear ratios between the phases of oscillations of η, SS and CI. It implies that SCR generation is not isolated stochastic phenomena characteristic exclusively for chromospheric and/or coronal structures. In fact, this process may have global features and involve large regions in the Sun’s atmosphere.     

外源S_q等效电流体系电流涡中心电流强度与太阳活动关系

本文选取了INTERMAGNET地磁台网2001年到2012年的地磁数据,对其进行世界时(UT)到地方时(LT)的转换后利用自然正交分量法(NOC)从所选资料中提取出太阳静日变化Sq成分,再通过球谐分析方法建立模型分离内、外源Sq成分,逐日反演出内、外源Sq等效电流体系,并得到外源Sq等效电流体系南北电流涡中心电流强度.本文将外源Sq等效电流体系南北电流涡中心电流强度与同一时期的Dst指数进行了对比分析,研究表明它们之间具有同步变化的规律,且北半球电流涡中心电流强度在磁暴发生时的异常现象远高于南半球.对F10.7cm太阳射电流量与外源Sq等效电流体系南、北半球电流涡中心电流强度的长短周期分析发现,Sq等效电流表现出明显的11年周期特点,与太阳活动周期一致.外源南、北半球电流涡中心电流强度和F10.7cm年均值的相关系数分别达到了0.93和0.90,说明太阳活动是导致外源Sq电流体系变化的最直接也最主要的因素,这可能与电离层电导率受控于太阳的电磁辐射相关.     

Investigation of El Niño and La Niña effects and the impact of Atlantic sea surface temperatures (SSTs), on precipitation in Nigeria from 1950 to 1992

Monthly precipitation data from meteorological stations in Nigeria are analysed from 1950 to 1992, in relation to sea surface temperatures (SSTs) in the tropical Pacific and Atlantic Oceans. The analyses have shed some light on understanding the variability of rainfall anomalies observed in Nigeria for this period. The correlation values between rainfall anomaly indices (RAI) and different meteorological indices are not all significant. Thus, the analyses show some indication that rainfall in Nigeria is associated with El Niño-related circulation and rainfall anomalies. The low correlations between RAI and SST in the Pacific confirm low correlations between rainfall and southern oscillation indices (SOI). SST correlations in the tropical Atlantic suggest that warm surface water in this part of the Atlantic moves the Inter Tropical Convergence Zone (ITCZ) southward and away from the SouthEast of Nigeria, indicating less rainfall, while, in SouthWest of Nigeria, the warm surface waters in this part of the Atlantic are likely to be responsible for a more northern position of the ITCZ, which produces more rainfall. The lower correlation in Northern Nigeria may be attributed to its continentality, away from the influence of the sea surface conditions in the Gulf of Guinea and the tropical Atlantic. The drought, or rainfall, cycles in Northern Nigeria are more closely connected to the land surface conditions in the nearby Sahel region.     

Relationship between solar radiation and dimethylsulfide concentrations using in situ data for the pristine region of the southern hemisphere

The biological processes have been proposed as climate variability contributors. Dimethylsulfide (DMS) is the main biogenic sulfur compound in the atmosphere; it is mainly produced by the marine biosphere and plays an important role in the atmospheric sulfur cycle. Currently it is accepted that terrestrial biota not only adapts to environmental conditions but also influences them through regulations of the chemical composition of the atmosphere. In the present study we used a wavelet method to investigate the relationship between DMS, Low cloud cover (LCC), Ultraviolet Radiation A (UVA), Total Solar Irradiance (TSI) and Sea Surface Temperature (SST) in the so called pristine zone of the Southern Hemisphere. We found that the series analyzed have different periodicities which can be associated with large scale climatic phenomena such as El Niño (ENSO) or the Quasi-Biennial Oscillation (QBO), and/or to solar activity. Our results show an intermittent but sustained DMS-SST correlation and a DMSUVA anti correlation; but DMS-TSI and DMS-LCC show nonlinear relationships. The time-span of the series allow us to study only periodicities shorter than 11 years, then we limit our analysis to the possibility that solar radiation influences the Earth climate in periods shorter than the 11-year solar cycle. Our results also suggest a positive feedback interaction between DMS and solar radiation.     

Variable Solar Forcing and Climate Changes

Numerous studies of interrelations between solar activity and global climate changes report contradictory conclusions. The topic as such is too complex, and manifestations of the studied relationship appear to differ in time and space, and sometimes are even of the opposite sense, In this study the data on air temperature and precipitation totals from Hurbanovo, one of the oldest meteorological observatories in Europe, are used to study their evolution within the interval 1871–1995, covering solar cycles 12–22, The variability of the meteorological elements mentioned is compared with that of the sunspot number and aa index of geomagnetic activity. The sensitivity of climate changes to variable solar forcing is presented as a comparison of extreme (maximum/minimum) activity conditions. Harmonic components with periods close to the length of the solar secular and solar magnetic cycles were found in climate evolution profiles.