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Dalin P.,Swedish Institute of Space Physics | Dalin P.,Russian Academy of Sciences | Pertsev N.,Russian Academy of Sciences | Dubietis A.,Vilnius University | And 12 more authors.
Journal of Atmospheric and Solar-Terrestrial Physics | Year: 2011

A comparison is made between ground-based observations of noctilucent clouds (NLCs), obtained with a network of automated digital cameras, and Aura satellite data (the MLS instrument). The Aura data (water vapor and temperature) demonstrate reasonable values around the summer mesopause fostering NLC formation in June through August, when supersaturated air conditions occur. The temperature decrease leads, in general, to amplification of the NLC brightness. The 2- and 5-day planetary waves, extracted from the Aura temperature field, have definite influence on the brightness variations of NLCs. The temperature behavior around the summer mesopause at 60°N demonstrated a remarkable feature, namely, in 2007 the minimum of a Gaussian fitted seasonal temperature variation was observed, on average, 14 days earlier and was broader than the corresponding minimum in 2008. The different temperature climatology resulted in different seasonal variation of NLCs in 2007 and 2008; in particular, the maximum of a Gaussian fitted seasonal variation of the NLC brightness cycle in 2007 was advanced by 12-29 days relative to that in 2008. © 2011 Elsevier Ltd.

Dubietis A.,Vilnius University | Dalin P.,Swedish Institute of Space Physics | Balciunas R.,Vilnius University | Cernis K.,Vilnius University | And 15 more authors.
Applied Optics | Year: 2011

Noctilucent, or "night-shining," clouds (NLCs) are a spectacular optical nighttime phenomenon that is very often neglected in the context of atmospheric optics. This paper gives a brief overview of current understanding of NLCs by providing a simple physical picture of their formation, relevant observational characteristics, and scientific challenges of NLC research. Modern ground-based photographic NLC observations, carried out in the framework of automated digital camera networks around the globe, are outlined. In particular, the obtained results refer to studies of single quasi-stationary waves in the NLC field. These waves exhibit specific propagation properties-high localization, robustness, and long lifetime-that are the essential requisites of solitary waves. © 2011 Optical Society of America.

Dalin P.,Swedish Institute of Space Physics | Dalin P.,Russian Academy of Sciences | Perminov V.,Russian Academy of Sciences | Pertsev N.,Russian Academy of Sciences | And 15 more authors.
Journal of Geophysical Research: Atmospheres | Year: 2013

Detailed tracing of an exhaust plume from a rocket's initial trajectory is a scientifically and diagnostically useful technique. It can provide detailed information on the atmosphere's mean winds, wind shears, turbulent regime, and physical state over a wide altitude range from 50 to 200 km. We analyze Soyuz rocket exhaust plumes from Plesetsk on 21 May 2009 and 27 June 2011, which uncovered significantly different atmospheric states and underlying dynamics. The first case showed highly dynamical conditions in the mesosphere, characterized by vortex structures, wind shears, and small-scale turbulent eddies. The estimated turbulent energy dissipation rates ranged 330-460 mW kg-1. A characteristic balloon-shaped trail was observed at altitudes between 105 and 160 km, having rapid expansion rates of 500-800 m s -1 over the time period of 2 min which can be explained by complex gas dynamic processes in the rocket wake involving the collision of shock waves. In the second case, we show evidence that the rocket exhaust trail persisted without any changes during its motion from Plesetsk via Denmark to the UK for 9 h, indicating extremely stable atmospheric conditions. This case introduces a new state of the summer mesosphere - remarkably quiet conditions, probably never observed before. The rocket plumes studied, related to the initial rocket trajectory, are essentially twilight phenomena as seen from the ground using wideband spectrum cameras, that is, the Sun should be below the horizon by 6°. For the first time, we analyze the dynamics of rocket exhaust products at the initial trajectory in the mesosphere and lower thermosphere using detailed photographic imaging taken from the ground. Key Points Soyuz rocket launches uncovered different atmospheric states and dynamics A characteristic balloon-shaped trail was observed between 105 and 160 km A rocket exhaust trail persisted without any changes during its motion for 9 hrs ©2013. American Geophysical Union. All Rights Reserved.

Dalin P.,Swedish Institute of Space Physics | Dalin P.,Russian Academy of Sciences | Connors M.,Athabasca University | Schofield I.,Athabasca University | And 13 more authors.
Geophysical Research Letters | Year: 2013

We report on the first common volume ground-based and space measurements of the mesospheric front in noctilucent clouds (NLCs). The detailed ground-based observations were performed with automated digital cameras located at the Athabasca University Geophysical Observatory (Canada) on the night of 29-30 June 2012, while simultaneous space measurements were conducted onboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics satellite using the Sounding of the Atmosphere using Broadband Emission Radiometry instrument. The large temperature difference of 20-25 K between two different air masses at about 85 km altitude was responsible for the front jump separating the area filled with NLCs from the area with no NLCs. The front jump (soliton) had a pronounced elevation of 12 km up to the altitude of 96 km relative to the undisturbed NLC layer located between 84.5 and 86.3 km. Considering present and previous ground-based measurements of the NLC height, we conclude that altitude of 96-97 km is the upper limit of possible heights of NLCs. ©2013. American Geophysical Union. All Rights Reserved.

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