Microwavephysics and Atmospheric Physics
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Biomedizinische Photonik
Ultrafast Science and Technology
Last update: 22.11.2018
FS 2013: Seminare über Microwavephysics and Atmospheric Physics
Friday 10-12
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Freitag, 22.02.2013

Variability of the Brewer-Dobson circulation

Zeit: 10:15 Uhr
Hörsaal: A97
Dr. Thomas Flury
Bundesamt für Gesundheit, Bern

I will show some results of my postdoctoral work performed in the Microwave Limb Sounder group at the Jet Propulsion Laboratory in California. Using satellite measurements of stratospheric water vapor as tracer for dynamics we inferred interannual variations in the speed of the Brewer-Dobson circulation (BDC) from 2004 to 2011. The BDC distributes air from the tropical upper troposphere into the stratosphere and is directed towards the winter pole where the air reenters the troposphere eventually. We observed a clear interannual variability of the vertical and horizontal branch of the circulation which reflects a period of approximately 2 years. Surprisingly the measurements show an anticorrelation of the meridional and vertical speed of the circulation. In this talk I will try to explain the reason for this anticorrelation and further how our stratospheric water vapor measurements can be used to assess the variability of tropospheric ozone in a future climate

Freitag, 01.03.2013

Recent progress in innovative manufacturing techniques for Terahertz passive components at SWISSto12 SA.

Zeit: 10:15 Uhr
Hörsaal: A97
Emile de Rijk
Head, Products & Services

SWISSto12 is a private start-up company, spin-off of the LPMN laboratory at the Swiss Federal Institute of Technology in Lausanne, (EPFL). Based on a portfolio of 6 patents licensed by the EPFL, the company aims at becoming a leading supplier of passive components and systems for Terahertz (THz) transmission.

The company name illustrates both its Swiss production technologies and the Tera of THz signals.

This talk will present the progress made at SWISSto12 to manufacture passive components such as corrugated waveguides, horn antennas, quasi-optical units and absorbers between 80 and 750 GHz. The results presented in this study are based two technologies:

-> The Stacked rings technology. By an assembly of rings, high precision corrugated components can be manufactured in order to efficiently propagate THz frequencies.

-> The metal coated plastics technology. Components are produced in plastic materials via rapid-prototyping techniques, before being metal plated on the surfaces interacting with the electromagnetic fields.

Ongoing developments and activities at frequencies up to 3 THz will also be presented.

Finally, applications of the above mentioned components in Plasma Physics or Magnetic Resonance Spectroscopy and Imaging techniques will also be presented, along with possible future fields of interest for these THz technologies.

Freitag, 08.03.2013

Atmospheric Vertical profiling by Raman lidar

Zeit: 10:15 Uhr
Hörsaal: A97
Dr. Francisco Navas Guzmán
Andalusian Center for Environmental Studies
University of Granada

In this seminar some results on the study of atmospheric aerosol particles and the characterization of the vertical structure of the atmosphere using the lidar technique are presented. The advantages of this active remote sensing technique include its non-invasive nature, in contrast to in situ measurements or chemical analyses, as well as the ability to depict the structure of the atmosphere with high vertical and temporal resolution. The multiwavelength Raman lidar used in my pre-doctoral research is routinely operated by the Atmospheric Physics Group in Granada (Spain). This instrument is part of the European Aerosol Research Lidar Network (EARLINET) whose main aim is the observation of the temporal and spatial distributions of atmospheric aerosol particles at the continental scale. The main advances performed during my research were the implementation and application of an appropriate methodology to characterize profiles of aerosol optical and microphysical properties and water vapour.

Freitag, 15.03.2013

The influence of energetic particles on atmospheric composition and dynamics

Zeit: 10:15 Uhr
Hörsaal: A97
Dr. Marco Calisto
International Space Science Institute, Bern

This talk will deal with the influence of energetic particles, especially the solar protons and the Galactic Cosmic Rays, on the Earth's atmosphere, including the dynamics using the chemistry-climate model SOCOL v2.0. We will see that the impact of these particles are mostly pronounced in the polar region, influencing odd nitrogen, HOx, ozone and the zonal winds. Depending on the energy level of the particle, these impacts can be visible down to the troposphere.

Freitag, 22.03.2013

Retrieval of atmospheric composition and structure of exoplanets from transit spectroscopy

Zeit: 10:15 Uhr
Hörsaal: A97
Dr. Jaemin Lee
Computational Astrophysics
Institute for Theoretical Physics
University of Zürich

Transit spectroscopy has been providing the best chance of characterising the atmosphere of planets around other stars. The current understanding of exoplanets implies great atmospheric diversity, requiring specialized software tools (e.g. optimal estimation retrieval) to overcome the degeneracy problem that is caused by the limits of available observations. In this talk, I'll discuss how to explore the family of plausible solutions for the atmospheric structure of known exoplanets and how to quantify the uncertainties and correlation between the atmospheric parameters caused by the degeneracy problem.

Freitag, 29.03.2013

Easter holiday (Good Friday)

Zeit: 10:15 Uhr
Hörsaal: A97

Freitag, 05.04.2013

Easter holiday

Zeit: 10:15 Uhr
Hörsaal: A97

Freitag, 12.04.2013

EGU Vienna

Zeit: 10:15 Uhr
Hörsaal: A97

Freitag, 19.04.2013

Development of Integrated Circuits and Modules up to 600 GHz. Based on mHEMT Technology

Zeit: 10:15 Uhr
Hörsaal: A97
Dr. Michael Schlechtweg
Fraunhofer Institute for Applied Solid State Physics (IAF)
Freiburg, Germany

A broad variety of Monolithic Millimeter-Wave Integrated Circuits (MMICs) and modules is developed at the Fraunhofer IAF for various applications in the frequency range up to 600 GHz, using the advanced metamorphic high electron mobility transistor (mHEMT) technology in the InGaAs/InAlAs material system on 4” GaAs substrates. To achieve very high operating frequencies and very low noise figure of the MMICs, the transit frequency of transistors has been pushed beyond 600 GHz by means of high indium content in the transistor channel and low gate lengths down to 20 nm.

The presented MMICs act as key components for radio astronomy (cooled and uncooled ultra-low-noise amplifiers), sensor systems (atmospheric sensors, collision avoidance radar, non-destructive materials testing), as well as wireless communication systems (satellite and radio links, mobile communication). The presentation will specifically address low-noise amplifiers up to 600 GHz, as well as a variety of multi-functional MMICs (including transmitters, receivers and complete radar circuits) comprising mixers, oscillators, switches, frequency dividers and frequency multipliers. Module packaging and system demonstrators will be also be addressed in the presentation.

Freitag, 26.04.2013

Trends and variability of atmospheric trace gases as observed by ground-based FTIR spectroscopy

Zeit: 10:15 Uhr
Hörsaal: A97
Dr. Thomas Blumenstock
Karlsruhe Institute of Technology
Institute for Meteorology and Climate Research
Karlsruhe, Germany

In the framework of the NDACC (Network for the Detection of Atmospheric Composition Change) we operate ground-based FTIR spectrometers at a few sites: Kiruna (Sweden), Izana (Tenerife Island) and Karlsruhe. These measurements are used to estimate chlorine activation and ozone depletion (Kiruna), to derive trends and to validate satellite data. This talk will present some examples.

Freitag, 03.05.2013

How to measure wind in the middle atmosphere?

Zeit: 10:15 Uhr
Hörsaal: A97
Rolf Rüfenacht
Institute of Applied Physics
University of Bern

Wind is one of the key parameters for the characterisation of the atmosphere and the understanding of its dynamics. Despite this, until now no routinely operating measurement application for wind in the upper stratosphere and lower mesosphere exists. Radiosondes rarely reach altitudes of more than 35 km and the different radar, lidar and airglow applications are normally limited to altitudes above about 70 km.

Recently, some efforts have been made to overcome the lack of wind data in this altitude range. These were on the one hand based on the extension of the altitude range of lidar techniques, but also the infrasound community whose primary subject is the monitoring of explosions and volcano activity begins to show interest in the topic and first sketches of wind retrievals based on measurements from infrasound stations have just been published.

The Institute of Applied Physics of the University of Bern aims to contribute to the closing of the data gap for wind measurements in the middle atmosphere with a new instrument called WIRA using ground-based microwave radiometry. In contrast to other techniques, WIRA is continuously running, independent of daylight and weather conditions, transportable, and relatively inexpensive. Two years of data from Bern and Sodankylä (Finland) are now available and show surprisingly good agreement with the model data from ECMWF. This summer, based on the first promising results, WIRA has been substantially upgraded improving its signal to noise ratio by a factor of 2.4.

The presentation will give an overview of the different wind measurement techniques in the middle atmosphere in a first part before focussing on the description of the technique, the instrumental setup and the data from WIRA.

Freitag, 24.05.2013

The influence of meteors on the atmosphere

Zeit: 10:15 Uhr
Hörsaal: A97
Elisavet Proedrou
Institute of Applied Physics
University of Bern

Meteor showers can change the atmospheric composition and ionization of the atmosphere, but their influence on the thermal state and dynamics of the middle atmosphere has not been studied in depth. The progress in Earth observation and atmospheric modelling of the past decades allows us to revisit the question of atmospheric heating by meteor showers. As an initial test, we performed a simulation with the Whole Atmosphere Community Climate model (WACCM). We assumed that the kinetic energy of the meteor shower heats up the mesosphere by 10 K at the start of the simulation. This perturbation caused significant differences in the evolution of the wind and temperature distribution of the lower and middle atmosphere even after 31 days. Particularly a Sudden Stratospheric Warming was suppressed by the change of the initial conditions in the mesosphere.

Freitag, 31.05.2013

Atmosphärische Fernerkundung mit einem bildgebenden Radiometer bei 91 GHz und einem Temperatur-Radiometer bei 50-60 GHz

Zeit: 10:15 Uhr
Hörsaal: B5
Oliver Stähli
Institute of Applied Physics
University of Bern