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Last update: 21.08.2018
FS 2011: Seminare über Microwavephysics and Atmospheric Physics
Friday 10-12
Vorträge, die innerhalb der nächsten Tage stattfinden, sind speziell markiert.
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Freitag, 04.03.2011

Intraseasonal Oscillations of Stratospheric Ozone above Switzerland

Zeit: 10:15 Uhr
Hörsaal: A97
Simone Studer
Institute of Applied Physics, University of Bern

In the presentation, I analyse if some of the observed stratospheric ozone variations above Bern can be explained in the wake of intraseasonal oscillations of the troposphere. A relationship between stratospheric ozone and tropospheric dynamics is possible since the meridional Brewer-Dobson circulation of the middle atmosphere is strongly forced by upward propagation of tropospheric planetary waves into the winter stratosphere. I investigate this link by relating intraseasonal oscillations of the troposphere as described by the time series of MJO (Madden-Julian Oscillation) and NAO (North Atlantic Oscillation) indices to intraseasonal oscillations of extratropical ozone as measured by the GROMOS microwave radiometer above Bern. Particularly, I present mean characteristics of intraseasonal oscillations of stratospheric ozone above Bern including their interannual variability and their relationship to sudden stratospheric warmings. Because of the nonlinear nature of the middle atmosphere, we cannot expect that all ozone variations can be understood. However, a good description of the ozone variability is the first step towards progress in observation, data analysis, modeling, and understanding.

Freitag, 11.03.2011

Optical Design of the Stratosphere-Troposphere Exchange And Climate Monitor Radiometer (STEAMR)

Zeit: 10:15 Uhr
Hörsaal: A97
Dr. Mark Whale
Institute of Applied Physics, University of Bern

The subject of this talk will be a summary of the optimisation and design of the optics for the STEAMR multi-beam limb sounder instrument that has been performed here at IAP Bern. This instrument is a Swedish national contribution to the upcoming ESA PREMIER mission, which is a candidate for the Earth Core Explorer mission. The aim of the PREMIER mission, which stands for Process Exploration through Measurement of Infrared and millimetre-wave Emitted Radiation, will be to advance current understanding of the processes that link trace gases, radiation and chemistry in the upper troposphere and lower stratosphere. This optimisation process was necessary to find a suitable optics solution that would achieve the simultaneous goals of beam amplitude circularisation and phase shift matching and was conducted using a combination of analytical and numerical methods. The results of this optimisation have been verified through a combination of first order Gaussian beam analysis coupled with physical optics calculations. Additionally, the concept and design for a focal plane array element which will couple the individual beams to their corresponding feeds will be presented.

Freitag, 18.03.2011

New Developments in Quasi-Optics

Zeit: 10:15 Uhr
Hörsaal: A97
Prof. J. Anthony Murphy
Department of Experimental Physics
National University of Ireland, Maynooth

Beam propagation of radiation in far infrared optical systems is dominated by diffraction and the modelling of such so-called quasi-optical systems requires a special approach. Originally such long wavelength systems were single pixel in which the propagating beam could be assumed to be coherent and therefore described efficiently in term of Gaussian beam modes. With the development of partially coherent and multi-element arrays, such as for the ESA Planck satellite, issues associated with the propagation and imaging of a field of view have arisen requiring further developments in long-wave optics. In this talk we review such new developments in quasi-optical systems including for next generation space satellite systems, where compact optics tends to drive the design.

Freitag, 25.03.2011

Ground-based remote sensing of land surfaces -
The influence of periodic patterns and relief on thermal microwave emission

Zeit: 10:15 Uhr
Hörsaal: B5
Ingo Völksch
Eidg. Forschungsanstalt WSL

Freitag, 08.04.2011

Continuous Wave Photo-Mixing for THz Generation

Zeit: 10:15 Uhr
Hörsaal: A97
Prof. Luis Enrique García Muñoz
Departamento Teoría de la Señal y Comunicaciones,
Universidad Carlos III de Madrid

This presentation focuses on latest developments of continuous-wave (CW) photomixing for Terahertz (THz) generation. The presentation explains the limiting factors for operation at high frequencies » 1 THz, namely transit– or lifetime roll-off, RCroll- off, current screening and –blocking and heat dissipation. It will present various realizations of both photoconductive and p-i-n diode based photomixers to overcome these limitations, including prospectives on novel materials for high power photomixers operating at telecom wavelengths (1550 nm). Applications such as spectroscopical applications, the field with probably the highest impact of THz research will be presented with measurements. It will be pointed out that CW spectroscopy systems may potentially be compacter, cheaper, and more accurate than conventional pulsed systems. Future trends and breakthroughs will be overcoming. Several novel approaches for increasing the efficiency of the systems will be presented with measurements, getting efficiencies 2 order of magnitude higher than state of the art.

Freitag, 15.04.2011

Oscilloscope workshop

Zeit: 10:15 Uhr
Hörsaal: A97
Daniel Weber and Andres Luder
Electronics lab of IAP

The oscilloscope is an integral instrument in the modern electronics laboratory and are as common as dBm-calculations are to microwave physicists. They are an indispensable tool for circuit development and analysis of a large variety of complex electronic signals from a wide selection of sources. In this seminar/workshop, the IAP electronics lab will provide a general introduction to oscilloscopes, with an historical overview covering early vintage equipment up to today's sophisticated DSOs The workshop attendees will then be given the opportunity to interact with the different scopes and apply their their new skill sets.

Freitag, 06.05.2011

A new radiometer for measurements of the Canadian Arctic atmosphere

Zeit: 10:15 Uhr
Hörsaal: A97
Niall Ryan
Atmospheric Physics
University of Toronto

In this presentation I will talk about the development of a new ground-based millimetre-wave radiometer, being designed and built at the University of Toronto, in the context of polar stratospheric remote sounding. The project is part of the Canadian Network for the Detection of Atmospheric Change (CANDAC) and the radiometer will join and complement an array of different instruments housed at the PEARL laboratory in Eureka, Nunavut (80°N 86°W). Operating between 260 – 280 GHz, the radiometer will observe emissions from species related to ozone chemistry; mainly ozone (O3), chlorine monoxide (ClO), and nitric acid (HNO¬3), so we may better understand the processes controlling the Arctic ozone budget. This year has shown the largest depletion of Arctic ozone on record and illustrates the need for continuous measurements of these trace gases, ClO in particular. I will discuss the recent Arctic ozone loss as well as the instrument; its general design, the observation scheme, and some simulations.

Freitag, 13.05.2011

Polarimetric Modeling, Calibration and Active Imaging at 91 GHz

Zeit: 10:15 Uhr
Hörsaal: A97
Marco Canavero
Institute of Applied Physics
University of Bern

The potential and success of remote sensing heavily depends on the existence of complete understanding of the processes to be investigated. The tasks involved are advancements of models that describe the phenomena to be studied, the improvements in calibration techniques and new applications for radiometers. In this seminar a short presentation of SPIRA radiometer will be followed by a general discussion about recent improvements achieved in modeling, calibration techniques and active imaging at 91 GHz. All these topics are still under development and others will be investigated in the future. For this reason, in the final part of the presentation some new ideas will be presented.

Freitag, 20.05.2011

Why is the Earth warm?

Zeit: 07:39 Uhr
Hörsaal: Berner Oberland

We invite you to the Microwave Department Annual Excursion - the topic of this years excursion will be "Why is the Earth warm ?" Our trip will start from the top of the Niesen where we can enjoy the fantastic panorama, after which we will begin a 3.5 hour walk from the Schwandegg to Frutigen. In the Frutigen Tropenhaus we will tour through the special exhibition - "Why is the Earth warm?", before finally returning to Bern via train. For the hike we recommend strong footwear and bring some food along as well. If you do not wish to participate in the hike it will be possible to remain on the Niesen summit for longer and then rejoin with the group via train in Frutigen.

Travel Details:
Train from Bern to Mülenen: 20th May 2011; Departure: 07.39 - Platform 5 - Front Train Section

Train from Frutigen to Bern: To be determined after the size of group is known (for discount ticket purposes). We will be back at Bern before 19:30.

Those who wish to attend the excursion must register by email - renker@iap.unibe - before Monday 16th May 2011 at 18.00 and please mention whether you will join the hike or not.

Freitag, 27.05.2011

First results of the new temperature radiometer - TEMPERA

Zeit: 10:15 Uhr
Hörsaal: A97
Oliver Stähli
Institute of Applied Physics
University of Bern

The new Temperature Radiometer TEMPERA operates in the frequency range from 51 to 57 GHz and is built to measure the atmospheric temperature profile. In this frequency region the absorption of oxygen plays a key role and we can retrieve the temperature profile of the tropo- and stratosphere. In a first step we will determine temperature profiles of the troposphere (0-10 km). Later on we will use also a spectrometer to measure two absorption lines around 53 GHz. With the spectrometer we are able to retrieve the temperature profile in the stratosphere (10-50 km). At the end we get a temperature profile for the troposphere and the stratosphere in a altitute range of 0-50 km at the same time.
Firstly I will talk about the design of TEMPERA. Then I will show some simulations with Qpack2 for the tropospheric temperature retrieval. At the end of the talk I will talk about the stratospheric temperature retrieval (theory, influence of the Zeeman effect) and give an outlook for future work.

Montag, 30.05.2011

Präsentation der Bachelor-Arbeiten

Zeit: 14:15 Uhr
Hörsaal: A97
Brigitta Mathys
Matthias Lüthi
Panos Stergiotis

Brigitta Mathys: WRF Simulationen von orographischen Wellen
Matthias Lüthi: Simulation von Konvektionszellen mit dem Weather Research and Forecasting Model
Panos Stergiotis: Software based narrowband FFT Spectrometer with USRP