Middle and Upper Atmosphere

Research at LIM

Middle Atmosphere

The middle atmosphere includes the atmospheric region above the

tropopause up to the lower thermosphere (10-100 km). The middle

atmosphere, mainly through wave coupling, acts as a sensor of

lower atmosphere variability. Research at Leipzig mainly aims into

two directions:

VHF radar wind and temperature measurements at 80-100 km

Numerical modeling of the middle and upper atmosphere and its

variability due to natural and anthropogenic forcing

printed at Rechenzentrum Leipzig poster available on http://www.uni-leipzig.de/~jacobi/docs/WG.pdf

Thermosphere/Ionosphere

The thermosphere / ionosphere region is mainly forced by solar

variability, but also reacts on the variability of lower regions.

Research focuses on solar variability, and long-term changes of the

thermosphere and ionosphere system.

EUV measurements on board ISS, and ionization from measured

EUV spectra

Planetary waves in ionospheric electron density

Lower E-region variability

Collm Observatory

At Collm, since the 1950 remote sensing instruments are operated

especially for the investigation of the upper and middle atmosphere,

which form the basis for the middle and upper atmosphere

research:

- VHF meteor radar

- LF receiver

- GPS receiver

At Collm, also seismic measurements are run by the Institute of

Geophysics and Geology of the University of Leipzig.

Information and contact: http://www.uni-leipzig.de/~jacobi/collm

jacobi@uni-leipzig.de

Vertical Coupling

Middle and upper atmosphere dynamics is, besides solar forcing,

also determined by forcing from below. We look for forcing

mechanisms that couple the lower and the upper atmosphere, as

well as the neutral and ionized part.

Fakultät für Physik und Geowissenschaften

Figures show transmitting antenna

(right), and transmitter and receiver

units (above) of the meteor radar.

Left: EUV-TEC index, defined as normalized

primary ionization calculated from TIMED

SEE solar EUV spectra. Also shown is global

total electron content (TEC) and F10.7 solar

proxy. The figure below shows energy

absorbed by different species.

1985 1990 1995 2000 200585

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Year

Collm 21-1 UT mean

LF

nig

httim

e r

efle

ctio

n h

eig

ht (k

m)

Right: The equatorial lower ionosphere shows

a wave 4 signature (colors), owing to neutral

atmosphere dynamcis (contours). The figure

shows GPS sporadic E occurrence rates

together with satellite temperature anomalies.

Figures on the left show zonal (upper panel)

and meridional (lower panel) prevailing winds

at midlatitudes according to measurements.

The zonal mean flow is characterized by

mesospheric westerlies in winter and

easterlies in summer, and a wind reversal in

the lower thermosphere.

This reversal is forced by breaking gravity

waves that also lead to an equatorward

meridional circulation in summer.

Figures on the right show mean temperatures

and zonal winds according to numerical model

results.

In the lower panels differences between solar

maximum and minimum conditions are shown.

Results refer to Northern Hemisphere winter

conditions.

Left: The figure shows solar EUV fluxes as

measured with the SolACES spectrometer

on board ISS (see figures below).

Left: Long-term measurements of LF reflection heights

in the lower ionosphere. The time series show a

decadal change due to the 11-year solar cycle.

-2 -1 0 1 20

3

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Zo

na

l w

ind

at 9

0 k

m (

m/s

)

NAO index

r = 0.52

Left: The figure shows mesopause region zonal

winds vs. NAO indices. The correlation shows

that there is a coupling throughout the winter

atmosphere via the strength of the polar vortex.

Right: Modulation of gravity waves by

planetary wave (yellow lines) shows the same

seasonal cycle as planetary wave-type os-

cillations (upper line) in the ionosphere do.

This shows that the signature of planetary

waves in the ionosphere is probably due to

modulation of gravity waves.

Left: Sporadic E layers in the lower ionosphere

(colors) show a semidiurnal signature, which is

owing to wind shear variability (contours) in the

neutral atmosphere. The figure shows GPS

measurements together with Collm radar wind

data. The symbols denote the phases of the

semidiurnal signature.

-180° -150° -120° -90° -60° -30° 0° 30° 60° 90° 120° 150° 180°

Longitude

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Collm Observatory, about 50 km east of

Leipzig, was founded in 1932 by Ludwig

Weickmann, the former Director of the

Geophysical Institute.

SolACES

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Time (LT)

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