Influence of solar activity on climate : Poles to Tropics

Solar activities are directly or indirectly responsible for climate variability around the globe. Evidences of such correspondences between solar activities and palaeoclimatic proxy data have been reported from polar as well as tropical regions, suggesting solar influence over climate dynamics. However, these findings need to be further strengthened by covering vast geographical region for generating palaeoclimatic data and corresponding variations in solar activities. A better time control on proxy data is essential to arrive at conclusive understanding and plausible causal linkages between solar activity and climate changes from poles to tropics.

Analysis of pre-monsoon thunderstorm frequency over Srlniketan, Alipore and Kalaikunda -The possible association with solar activity

ABSTRACT -General characteristic features of thunderstorm frequency (TSF) observed during (1951-89) during pre-monsoon season at Sriniketan (23°39'N, 87"42'E), Alipore (22° 32'N, 88"20'E) and Kalaikunda (21°20'N, 87" 13'E) have been studied. It is seen that premonsoon TSF follows a rough periodicity 0f 6.6) year. For Kalaikunda (KLK) there is an overal1 upward trend and for Sriniketan (SKT) an overall downward trend; whereas, for Alipore (ALP) the trend pattern remains practically constant. The maximum TSF attained by all these three stations is nearly twice that of mean TSF of respective stations. The solar influence on the frequency of thunderstorm (TS) has been investigated and found to be interesting. TSF over SKT and KLK attained minimum value while that over ALP was near minimum during 1957; which in turn was the year of maximum sunspot (SS) number over the entire period of analysis. Now in general, if we take SS number and TSF of same year and calculate correlation coefficient (CC) considering all the years. i.e., taking SS without any restriction, the CC comes out to be quite small. But the result is just the reverse when the TSF value of those years is considered when SS number is higher. In particular when SS number exceeds some critical value (~140), TSF decreases sharply. The effect of solar sub-cycle, 11-yearcycle and 22-yearcycle un TS has also been discussed. It is seen that during min-max sub-phases, mean TSF is comparatively higher than its value in neighbouring max-min sub-phases and also it is in opposite phase in relation with mean SS. During 11-yearcycle also in most of the cases an opposite phase relationship exists between mean TSF and mean SS.

Pre-monsoon maximum temperatures over New Delhi, Mumbai & Chennai and possible solar influence

Lkkj & o"kZ 1951 ls 2001 rd dh 51 o"kksZa dh vof/k ds fy, ubZ fnYyh] eqEcbZ vkSj psUuS esa ekulwu iwoZ vf/kdre rkieku esa lkekU; fofHkUurkvksa ds lkSj {kksHk [lw;Z ds /kCcksa ¼,l- ,l-½ dh la[;k ds okf"kZd vkSlr ds laca/k esa vkdyu] ds lkFk laHkkfor laca/k dk lkaf[;dh; :Ik ls fo’ys"k.k fd;k x;k gSA rkieku ds Ja`[kykc) vk¡dM+ksa ds vk/kkj ij dsoy psUuS ds fy, rkieku esa o`f) dh izo`fRr dks NksM+dj vU; lHkh dsanzksa ij yxHkx 3 o"kksZa ds vUrjky ij bldh iqujko`fr dk irk pyk gS A lkSj voLFkkvksa ¼o`f) nj fun’kZ dk mi;ksx djds½ dh fofHkUurkvksa ds fo’ys"k.k ls lw;Z dh U;wure vkSj vf/kdre voLFkkvksa ds nkSjku 73 izfr’kr ekeyksa esa rkieku esa o`f) dh izo`fRr dk irk pyk gS A xr o"kZ ds ekulwu iwoZ rkieku vkSj lw;Z ds /kCcksa dh la[;k ds okf"kZd vkSlr ds chp lglaca/k ds xq.kkad :Ik ls ldkjkRed gksus dk irk pyk gS tc lw;Z ds /kCcksa dh la[;k dk okf"kZd vkSlr yxHkx 140 ds pje eku ls vf/kd gks tkrk gS vkSj ;g ¼$0-647½ ubZ fnYyh ds laca/k esa egRoiw.kZ gS A ;g ifj.kke iwohZ Hkkjr ds dsanzksa ds fy, fd, x, blh rjg ds v/;;uksa ds vuq:Ik gS A The general variations of pre-monsoon maximum temperature over New Delhi, Mumbai and Chennai for the 51 years period from 1951 to 2001 and its possible association with solar activity [estimated in terms of annual mean sunspot (SS) numbers] have been analysed statistically. The temperature series indicate an approximate periodicity of 3 years for all the stations with an increasing trend for Chennai only. Analysis of the variations with respect to solar phases (using a growth rate model) indicates an increasing trend of temperature in 73% cases during solar minimum to maximum phases. The correlation coefficient between pre-monsoon temperature and annual mean SS nos. of the preceding year indicate a positive association when the latter exceeds some critical value approximately 140 and it (+0.647) is significant for New Delhi. The present result is consistent with similar studies for stations over eastern India.

Climate history of the principality of Transylvania during the Maunder Minimum (MM) years (1645–1715 CE)

This paper deals with the climate in the former Grand Duchy of Transylvania, now one of the three major geographical provinces of Romania, within the so-called Maunder Minimum (MM) (1645–1715), an astrophysically defined part of the Little Ice Age (LIA), which was characterized by reduced solar activity. The historical data from Transylvania are compared with that from Germany, Austria and Switzerland. This comparison for the period 1645–1715 shows good agreement but also reveals geographic characteristics of the region. For the first time, we present here a comparison between the four geographic areas in text and tabular form. Quotes from mostly German-language sources are reproduced in English translation. Furthermore, we examine for a longer period (1500–1950) the extent to which the climate of Transylvania might have been affected by long-term fluctuations in solar activity, as deduced from isotopic reconstructions from ice cores. This comparison suggests a certain solar influence but the agreement is not very pronounced. Future investigation in a pan-European context is needed to reach reliable statements. Some results are unexpected – like an unusually small number of severe winters during the last decades of the MM, where extreme cold was restricted to a few years, like the extreme winters 1699/1700 and 1708/1709.

Role Of the Sun and the Middle atmosphere/thermosphere/ionosphere In Climate (ROSMIC): a retrospective and prospective view

While knowledge of the energy inputs from the Sun (as it is the primary energy source) is important for understanding the solar-terrestrial system, of equal importance is the manner in which the terrestrial part of the system organizes itself in a quasi-equilibrium state to accommodate and re-emit this energy. The ROSMIC project (2014–2018 inclusive) was the component of SCOSTEP’s Variability of the Sun and Its Terrestrial Impact (VarSITI) program which supported research into the terrestrial component of this system. The four themes supported under ROSMIC are solar influence on climate, coupling by dynamics, trends in the mesosphere lower thermosphere, and trends and solar influence in the thermosphere. Over the course of the VarSITI program, scientific advances were made in all four themes. This included improvements in understanding (1) the transport of photochemically produced species from the thermosphere into the lower atmosphere; (2) the manner in which waves produced in the lower atmosphere propagate upward and influence the winds, dynamical variability, and transport of constituents in the mesosphere, ionosphere, and thermosphere; (3) the character of the long-term trends in the mesosphere and lower thermosphere; and (4) the trends and structural changes taking place in the thermosphere. This paper reviews the progress made in these four areas over the past 5 years and summarizes the anticipated research directions in these areas in the future. It also provides a physical context of the elements which maintain the structure of the terrestrial component of this system. The effects that changes to the atmosphere (such as those currently occurring as a result of anthropogenic influences) as well as plausible variations in solar activity may have on the solar terrestrial system need to be understood to support and guide future human activities on Earth.

The Sun's Role for Decadal Climate Predictability in the North Atlantic

Despite several studies on decadal-scale solar influence on climate, a systematic detection of solar-induced signals at the surface and the Sun's contribution to decadal climate predictability is still missing. Here, we disentangle the solar-cycle-induced climate response from internal variability and from other external forcings such as greenhouse gases. We utilize two 10-member ensemble simulations with a state-of-the-art chemistry climate model, to date a unique data set in chemistry climate modelling. We quantify the potential predictability related to the solar cycle and demonstrate that the detectability of the solar influence on surface climate depends on the magnitude of the solar cycle. Further, we show that a strong solar cycle forcing organizes and synchronizes the decadal-scale component of the North Atlantic Oscillation, the dominant mode of climate variability in the North Atlantic region.