Long-term trends and year-to-year variability of mid-latitude mesosphere/lower thermosphere winds

Abstract. Recent years have shown a continuing interest in studies of the mesosphere-lower thermosphere region at low latitudes, with more than 50 papers dealing specifically with this area published over the past 5 years. Experimental ground-based work has been carried out mainly in South America and the Caribbean, India and the Pacific areas. Subjects of interest include gravity waves, tides and planetary waves, the temperature structure of the mesopause region, with special reference to temperature inversions and the two-level mesopause, sporadic neutral layers and their relationship with ionized layers, the possible effects of the micrometeoroid influx, and long-term trends in the MLT region. Experimental techniques in use include MF, MST and meteor radar, lidar, airglow (including satellite-borne limb-scanning measurements) and rocket-borne instruments. Airglow imaging has shown itself to be a particularly useful technique, mainly for studying gravity wave propagation in the MLT region. This paper will present highlights of recent work and will discuss some of the problems which remain to be resolved.

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Low-frequency lower E-region wind and reflection height measurements as sensor for climate variability

Advances in Radio Science ◽

10.5194/ars-6-331-2008 ◽

2008 ◽

Vol 6 ◽

pp. 331-335 ◽

Cited By ~ 1

Author(s):

C. Jacobi

Keyword(s):

Oblique Incidence ◽

Lower Thermosphere ◽

Low Frequency ◽

Time Interval ◽

Radio Waves ◽

Reflection Height ◽

E Region ◽

Long Term Trends ◽

Mlt Region

Abstract. Measurements of reflection heights of low-frequency (LF) radio waves at oblique incidence and estimates of mesosphere/lower thermosphere (MLT) region horizontal winds applying the D1 spaced receiver method on LF field strength registrations are analyzed with respect to possible long-term trends and interdecadal variability in the time interval from ~1980 to date. While no clear signal of mesospheric height trend is registered during the last two decades, significant trends of MLT horizontal winds are found. These trends are non-linear, in particular a change of trends around 1990 is found, which is probably connected with changes in tropospheric and stratospheric conditions at that time.

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Long-term trends and decadal variability of upper mesosphere/lower thermosphere gravity waves at midlatitudes

Journal of Atmospheric and Solar-Terrestrial Physics ◽

10.1016/j.jastp.2013.05.009 ◽

2014 ◽

Vol 118 ◽

pp. 90-95 ◽

Cited By ~ 12

Author(s):

Christoph Jacobi

Keyword(s):

Gravity Waves ◽

Decadal Variability ◽

Lower Thermosphere ◽

Long Term Trends

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Long-term trends of <i>f</i>oE and geomagnetic activity variations

Annales Geophysicae ◽

10.5194/angeo-21-751-2003 ◽

2003 ◽

Vol 21 (3) ◽

pp. 751-760 ◽

Cited By ~ 13

Author(s):

A. V. Mikhailov ◽

B. A. de la Morena

Keyword(s):

Geomagnetic Activity ◽

Lower Thermosphere ◽

Chemical Pollution ◽

Anthropogenic Activity ◽

Ionospheric Disturbances ◽

Time Period ◽

Long Term Trends ◽

First Time ◽

Long Term Variations

Abstract. A relationship between foE trends and geomagnetic activity long-term variations has been revealed for the first time. By analogy with earlier obtained results on the foF2 trends it is possible to speak about the geomagnetic control of the foE long-term trends as well. Periods of increasing geomagnetic activity correspond to negative foE trends, while these trends are positive for the decreasing phase of geomagnetic activity. This "natural" relationship breaks down around 1970 (on some stations later) when pronounced positive foE trends have appeared on most of the stations considered. The dependence of foE trends on geomagnetic activity can be related with nitric oxide variations at the E-layer heights. The positive foE trends that appeared after the "break down" effect may also be explained by the [NO] decrease which is not related to geomagnetic activity variations. But negative trends or irregular foE variations on some stations for the same time period require some different mechanism. Chemical pollution of the lower thermosphere due to the anthropogenic activity may be responsible for such abnormal foE behavior after the end of the 1960s.Key words. Ionosphere (ionosphere-atmosphere interactions; ionospheric disturbances)

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