On the force of vertical winds in the upper atmosphere: consequences for small biological particles

For many decades, vertical winds have been observed at high altitudes of the Earth’s atmosphere, in the mesosphere and thermosphere layers. These observations have been used with a simple one-dimensional model to make estimates of possible altitude climbs by biologically sized particles deeper into the thermosphere, in the rare occurrence where such a particle has been propelled to these altitudes. A particle transport mechanism is suggested from the literature on auroral arcs, indicating that an altitude of 120 km could be reached by a nanometre-sized particle, which is higher than the measured 77 km limit on the biosphere. Vertical wind observations in the upper mesophere and lower thermosphere are challenging to make and so we suggest that particles could reach altitudes greater than 120 km, depending on the magnitude of the vertical wind. Applications of the larger vertical winds in the upper atmosphere to astrobiology and climate science are explored.

Review of Long-Term Trends in the Equatorial Ionosphere Due the Geomagnetic Field Secular Variations and Its Relevance to Space Weather

The Earth’s ionosphere presents long-term trends that have been of interest since a pioneering study in 1989 suggesting that greenhouse gases increasing due to anthropogenic activity will produce not only a troposphere global warming, but a cooling in the upper atmosphere as well. Since then, long-term changes in the upper atmosphere, and particularly in the ionosphere, have become a significant topic in global change studies with many results already published. There are also other ionospheric long-term change forcings of natural origin, such as the Earth’s magnetic field secular variation with very special characteristics at equatorial and low latitudes. The ionosphere, as a part of the space weather environment, plays a crucial role to the point that it could certainly be said that space weather cannot be understood without reference to it. In this work, theoretical and experimental results on equatorial and low-latitude ionospheric trends linked to the geomagnetic field secular variation are reviewed and analyzed. Controversies and gaps in existing knowledge are identified together with important areas for future study. These trends, although weak when compared to other ionospheric variations, are steady and may become significant in the future and important even now for long-term space weather forecasts.

Non-zonal structures of the midlatitude mesosphere/lower thermosphere dynamics studied by using atmospheric models and radar observations.

<p class="western" align="left">Radar observations from two SKiYMET radars at Collm (51°N, 13°E) and Kazan (56°N, 49°E) during 2016-2017 are used to investigate the longitudinal variability of the mesosphere/lower thermosphere (MLT) wind regime over western and eastern Europe. Both of the meteor radars have similar setups and apply the same analysis procedures to correctly compare MLT parameters and validate the simulated winds. The radar observations confirm the established seasonal variability of the wind distribution, but this distribution is not identical for the two stations. The results show good qualitative agreement with global circulations model predictions by the Middle and Upper Atmosphere Model (MUAM) and the Upper Atmosphere ICOsahedral Non-hydrostatic model (UA-ICON). The MUAM and UA-ICON models well reproduce the main dynamical features, namely the vertical and temporal distributions of the winds observed throughout the year. However, there are also some differences in the longitudinal wind variability of the models and radar observations. Numerical experiments with modified parameterization settings have also been carried out to study the response of the MLT wind circulation to the gravity waves originating from the lower atmosphere. The MUAM model results show that a decrease/increase in the gravity wave intensity at the lower atmosphere leads to an increase/decrease of the mesospheric zonal wind jet extension and the zonal wind reversal.</p>

Vulkanische Einflüsse auf Atmosphäre und Klima: Wissenschaftliche Highlights der DFG Forschungsgruppe VolImpact (FOR 2820)

<p>Vulkanausbrüche stellen eine der größten Unsicherheiten für die Entwicklung des Klimas auf Zeitskalen von einigen Jahren bis zu einem Jahrzehnt dar. Gleichzeitig ermöglichen sie die Untersuchung der Reaktion des Klimasystems auf diese Ereignisse und können so das theoretische Verständnis des Klimasystems verbessern. Im Rahmen der von der Deutschen Forschungsgemeinschaft geförderten Forschungsgruppe VolImpact (FOR 2820) werden in fünf wissenschaftlichen Projekten verschiedene Aspekte vulkanischer Einflüsse auf Atmosphäre und Klima untersucht, wie die initiale Entwicklung der Vulkanwolke, der Einfluss von Vulkanausbrüchen auf die stratosphärische Aerosolschicht, die Wechselwirkung vulkanischer Aerosole mit Wolken in der Troposphäre, sowie vulkanische Effekte auf die Dynamik der mittleren Atmosphäre und den troposphärischen Wasserkreislauf. In diesem Beitrag sollen nach einer Übersicht über die wichtigsten vulkanischen Einflüsse auf das Erdsystem exemplarisch einige wissenschaftliche Highlights aus der laufenden ersten Phase der Forschungsgruppe VolImpact vorgestellt werden. So zeigte sich beispielsweise, dass die Wechselwirkung der Asche mit kurzwelliger Strahlung zu Erwärmung und Auftrieb der Vulkanwolke führt, was die Lebensdauer der vulkanischen Aerosole in der Atmosphäre erhöht. Außerdem ergab die Analyse von SAGEIII/ISS Satellitenmessungen, dass stratosphärische Sulfataerosolpartikel nach vielen Eruptionen unerwarteterweise kleiner werden, was wichtige Konsequenzen für die physikalischen und chemischen Effekte der Aerosole nach sich zieht. Die zugrundeliegenden mikrophysikalischen Prozesse sind bisher nicht vollständig verstanden. Darüber hinaus konnte in Simulationen mit UA-ICON (Upper Atmosphere Version des ICON-Modells) gezeigt werden, dass die Erwärmung der unteren Stratosphäre durch vulkanische Aerosole zu einer starken Erwärmung an der Mesopause führen kann, die über eine vertikale Kopplung durch Schwerewellen vermittelt wird.</p>

Measurement and analysis of refractive index structure constant Cn2 profile over Delhi on diurnal and seasonal basis

jsfM;ksa rjax ds lapj.k dks izHkkfor djus esa jsfM;ks viorZdrk ,d egRoiw.kZ dkjd dk dk;Z djrh gSA jsfM;ks viorZdrk] ok;qeaMy dh HkkSfrd voLFkkvksa tSls & rkieku] nkc vkSj vknzZrk ij fuHkZj djrh gSA jsMkj vR;Ur NksVh vk—fr ds viorZukad fHkUurkvksa tks jsMkj ds rjax nS/;Z dh vk/kh gksrh gS] ds izfr laosnh gksrs gSA i'p izdh.kZu 'kfDr viorZukad fu;rkad Cn2 dh vk—fr ds ifjek.k ij fuHkZj djrh gSA vr% ekSle jsMkj] fo’k"k :i foaM izksQkbyj jsMkj ds fM+tkbu ds fy, fdlh LFkku ds Cn2 ds eku mi;ksxh gksrs gSA bl 'kks/k i= esa fnYyh ds Åij ds mijhru ok;qeaMy esa ok;qeaMyh; viorZukad fu;rkad Cn2 dh :ijs[kk nSfud ,oa _rqvksa ds vk/kkj ij rS;kj djus dh dksf’k’k dh xbZ gSA The radio refractivity is an important factor which effects radio wave propagation. Radio refractivity depends upon the physical states of atmosphere, i.e., its temperature, pressure and humidity. Radars are sensitive to refractive index irregularities on scale size equal to half wavelength of Radar. Backscattered power is dependent on the magnitude of refractive index structure constant Cn2. Hence Cn2values of a place are useful for designing weather radar specially wind profiler radars. This paper is an attempt to map the profile of refractive index structure constant Cn2 of atmosphere in the upper atmosphere, over Delhi on diurnal and seasonal basis.