Sensitivity of the 4–10-Day Planetary Wave Structures in the Middle Atmosphere to the Solar Activity Effects in the Thermosphere

Numerical simulation of the general atmospheric circulation was performed to estimate changes in amplitudes of the westward-travelling planetary waves (PWs) at altitudes from the Earth’s surface up to 300 km under different solar activity (SA) levels. The three-dimensional nonlinear mechanistic model of circulation of the middle and upper atmosphere “MUAM” was used. The atmospheric general circulation and PW amplitudes were calculated based on ensembles containing 16 model runs for conditions corresponding to low and high SA. PWs having periods of 4–10 days were considered. Comparison with the data of digital ionosondes showed that the MUAM model is capable of reproducing the considered PW modes at thermospheric heights. It is shown that under high SA conditions, PW amplitudes are significantly larger in the thermosphere and smaller in the middle atmosphere. The observed PW structures are influenced not only by changes in atmospheric refractive index and Eliassen–Palm flux but also by varying PW reflection in the lower thermosphere, which can change proportions of the wave energy transferred from the lower atmosphere to the upper layers and reflected downwards

Manifestations of Different El Niño Types in the Dynamics of the Extratropical Stratosphere

The behavior of planetary waves and their influence on the global circulation of the Northern Hemisphere during different El Niño types is studied. Three sets of five boreal winters were chosen for each El Niño type: Modoki I and II and canonical El Niño. Based on data of the Japanese 55-year Reanalysis and the Modern-Era Retrospective Analysis for Research and Applications, the spatio-temporal structure of planetary waves and the residual mean circulation were analyzed. The results show that the canonical El Niño type is characterized by the weakest wave activity in March. It is also demonstrated that warming of the polar stratosphere, accompanied by maximizing wave activity and weakening of the zonal wind, may lead to earlier stratospheric polar vortex collapse and the early spring transition under Modoki I conditions. This study is the next step in understanding of the so-called long-range teleconnections, consisting of the propagation of a signal from the tropical El Niño Southern Oscillation source into the polar stratosphere

Manifestations of Different El Niño Types in the Dynamics of the Extratropical Stratosphere

The behavior of planetary waves and their influence on the global circulation of the Northern Hemisphere during different El Niño types is studied. Three sets of five boreal winters were chosen for each El Niño type: Modoki I and II and canonical El Niño. Based on data of the Japanese 55-year Reanalysis and the Modern-Era Retrospective Analysis for Research and Applications, the spatio-temporal structure of planetary waves and the residual mean circulation were analyzed. The results show that the canonical El Niño type is characterized by the weakest wave activity in March. It is also demonstrated that warming of the polar stratosphere, accompanied by maximizing wave activity and weakening of the zonal wind, may lead to earlier stratospheric polar vortex collapse and the early spring transition under Modoki I conditions. This study is the next step in understanding of the so-called long-range teleconnections, consisting of the propagation of a signal from the tropical El Niño Southern Oscillation source into the polar stratosphere

The formation of human populations in South and Central Asia

By sequencing 523 ancient humans, we show that the primary source of ancestry in modern South Asians is a prehistoric genetic gradient between people related to early hunter-gatherers of Iran and Southeast Asia. After the Indus Valley Civilization's decline, its people mixed with individuals in the southeast to form one of the two main ancestral populations of South Asia, whose direct descendants live in southern India. Simultaneously, they mixed with descendants of Steppe pastoralists who, starting around 4000 years ago, spread via Central Asia to form the other main ancestral population. The Steppe ancestry in South Asia has the same profile as that in Bronze Age Eastern Europe, tracking a movement of people that affected both regions and that likely spread the distinctive features shared between Indo-Iranian and Balto-Slavic languages.N.P. carried out this work while a fellow at the Radcliffe Institute for Advanced Study at Harvard University. P.M. was supported by a Burroughs Wellcome Fund CASI award. N.N. is supported by a NIGMS (GM007753) fellowship. T.C. and A.D. were supported by the Russian Science Foundation (project 14-50-00036). T.M.S. was supported by the Russian Foundation for Basic Research (grant 18-09-00779) “Anthropological and archaeological aspects of ethnogenesis of the population of the southern part of Western and Central Siberia in the Neolithic and Early Bronze Age.” D.P., S.S., and D.L. were supported by European Research Council ERC-2011-AdG 295733 grant (Langelin). O.M. was supported by a grant from the Ministry of Education and Sciences of the Russian Federation No. 33.1907, 2017/Π4 “Traditional and innovational models of a development of ancient Volga population”. A.E. was supported by a grant from the Ministry of Education and Sciences of the Russian Federation No. 33.5494, 2017/BP “Borderlands of cultural worlds (Southern Urals from Antiquity to Early Modern period).” Radiocarbon dating work supported by the NSF Archaeometry program BCS-1460369 to D.Ken. and B.J.C. and by the NSF Archaeology program BCS-1725067 to D.Ken. K.Th. was supported by NCP fund (MLP0117) of the Council of Scientific and Industrial Research (CSIR), Government of India, New Delhi. N.Bo., A.N., and M.Z. were supported by the Max Planck Society. D.Re. is an Investigator of the Howard Hughes Medical Institute, and his ancient DNA laboratory work was supported by National Science Foundation HOMINID grant BCS-1032255, by National Institutes of Health grant GM100233, by an Allen Discovery Center grant, and by grant 61220 from the John Templeton Foundation