Microwavephysics and Atmospheric Physics
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Last update: 18.10.2017
HS 2013: Seminare über Microwavephysics and Atmospheric Physics
Friday 10-12
Vorträge, die innerhalb der nächsten Tage stattfinden, sind speziell markiert.
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Freitag, 27.09.2013

Promotionsvortrag:
Variability of middle atmospheric ozone observed by the GROund-based Millimeter-wave Ozone Spectrometer (GROMOS)

Zeit: 10:15 Uhr
Hörsaal: B7
 
Simone Studer
Institute of Applied Physics
University of Bern

 
Freitag, 27.09.2013

Promotionsvortrag:
Studying atmospheric dynamics based on ground-based observations of middle atmospheric water vapor

Zeit: 14:15 Uhr
Hörsaal: B7
 
Dominik Scheiben
Institute of Applied Physics
University of Bern

 
Freitag, 04.10.2013

Signal processing techniques for the enhancement of an UWB multi-static radar-based modality

Zeit: 10:15 Uhr
Hörsaal: A97
 
Dr. Mantalena Sarafianou
University of Bristol, UK

Breast cancer is the most common cancer in women worldwide. Alternative imaging modalities are under development for the detection of breast cancer, complementary to x-ray mammography. Microwave radar-based imaging is one of them based on the electrical property contrast between healthy and cancerous breast tissues at microwaves for tumour localising. The radar system constructed at Bristol consists of a hemispherical antenna array used in multi-static mode for early stage breast cancer detection. Two distinct ways of enhancing the detection performance of this system will be discussed in this presentation; measuring the fitting of the patient’s breast in the experimental set-up prior to a measurement and estimating the breast’s relative permittivity which will be used to modify the assumed delays in a Delay-and-Sum imaging algorithm.

 
Freitag, 11.10.2013

Presentation of Master thesis: Analysis of sub-millimeter spectra from STEAMR breadboard receiver

Zeit: 10:15 Uhr
Hörsaal: A97
 
Michael von Grünigen
Institute of Applied Physics
University of Bern

 
Mittwoch, 16.10.2013

Seminar in the frame of the seminar series of WP:
Submillimeter Wave Instrument for JUICE

Zeit: 14:15 Uhr
Hörsaal: B5
 
Dr. Axel Murk
Institute of Applied Physics
University of Bern

JUpiter ICy moons Explorer (JUICE) is an ESA mission to Jupiter and its icy moons, Ganymede, Callisto and Europa. The JUICE payload includes the Submillimeter Wave Instrument (SWI), which is a passive radiometer/spectrometer tunable over a frequency range of 530–600 GHz. The main objective of SWI is to investigate the structure, composition and dynamics of the middle atmosphere of Jupiter and exospheres of its moons, as well as thermophysical properties of the satellites surfaces. In particular SWI will measure and map temperatures, and chemical species (e.g. CO, CS, HCN, H2O, CH4) in Jupiter’s stratosphere.
The Institute of Applied Physics is involved in the SWI development. The presentation will start with a short introduction to microwave remote sensing of the atmosphere and related projects at IAP. It will then provide details of SWI and the planned contributions from Bern.

 
Freitag, 08.11.2013

First results from the campaign on La Réunion

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

Since late August 2013 our campaign radiometers for middle atmospheric wind and water vapour are measuring at Maïdo observatory on La Réunion. So far, all campaign-based measurements have been taken at polar or mid latitudes of the northern hemisphere. With La Réunion being located at 21°S we have the opportunity to investigate the southern tropical atmosphere where ground-based measurements are rare.
After giving an introduction to the observation site, we describe the general behaviour of the atmosphere above La Réunion by using satellite and model data. Following the presentation of the measurements conditions we encountered on La Réunion, our time series of wind and water vapour are shown and interpreted.
We conclude the seminar with some foto impressions from La Réunion

 
Freitag, 15.11.2013

Spatial variability of tropospheric water vapor measured by airborne lidar

Zeit: 10:15 Uhr
Hörsaal: A97
 
Dr. Christoph Kiemle
Institut für Physik der Atmosphäre, DLR
Oberpfaffenhofen
Germany

Airborne water vapor differential absorption lidar measurements provide two-dimensional vertical cross sections of humidity and its variability along the aircraft flight track with high spatial resolution (0.2 km vertical, 2 km horizontal). The scaling exponents of horizontal structure functions take different values, depending on whether or not the observations took place in an air mass where convective clouds were present. Details on this research, as well as lidar measurements of other sources of humidity variability such as turbulence in the boundary layer and intrusions of stratospheric air into the troposphere will be presented.

 
Freitag, 22.11.2013

NORS: Demonstration Network Of Remote Sensing Ground-based Observations in support of the Copernicus Atmospheric Service

Zeit: 10:15 Uhr
Hörsaal: A97
 
PD Dr. Klemens Hocke
Institute of Applied Physics
University of Bern

NORS is a project within the Copernicus Earth Observation programme (http://www.copernicus.eu/) of the European Union. Copernicus is previously known as GMES (Global Monitoring for Environment and Security). Copernicus will launch a series of Earth observation satellites, the so-called Sentinels. For calibration and data quality control of the Sentinels, the NORS project established a Rapid Data Delivery System (RDDS) for delivery, archiving and distribution of ground-based remote sensing data of atmospheric composition. The ground-based microwave radiometers GROMOS and MIAWARA of IAP already deliver their data to RDDS. RDDS is not only good for the satellite community but it is a valuable tool for atmospheric researchers. The presentation gives an overview about the structure, instruments and data products of RDDS and its connection to the Network for the Detection of Atmospheric Composition Change (NDACC). A web-based intercomparison tool for observations and chemical reanalysis data is introduced. The reanalysis data of atmospheric composition originate from a chemical weather forecast model developed by the MACC project (Monitoring Atmospheric Composition and Climate). MACC also belongs to the Copernicus programme, and the MACC model assimilates observations from RDDS and satellites.

 
Freitag, 29.11.2013

Infrasound as verification technology for CTBT and beyond

Zeit: 10:15 Uhr
Hörsaal: A97
 
Dr. Alexis Le Pichon
CEA, DAM, DIF
Arpajon, France

The infrasound field, the science of low-frequency acoustic waves, has developed into a broad interdisciplinary field encompassing academic disciplines of physics and recent technical and scientific developments.

In 1996, the United Nations General Assembly adopted the Comprehensive Nuclear-Test-Ban Treaty (CTBT), prohibiting atmospheric nuclear explosions worldwide. The global International Monitoring System (IMS) infrasound network comprises 60 stations distributed over the globe. Nearly 70% of this global network is now operational. All technical aspects of infrasound monitoring were re-developed for CTBT verification using all state of the art advances. Today, highly sensitive sensors, efficient array designs and improved processing methods allow the detection low-amplitude signals within non-coherent noise. Beyond engineering sciences, also significant advances in meteorology and propagation modelling have helped to interpret the recordings.

Operational infrasound monitoring systems demonstrate the capability of the global network to detect, locate and characterize a large number of geophysical and man-made infrasound sources. Reference events provide a unique opportunity to better understand the details of the propagation in relation with high-resolution atmospheric models and to quantitatively assess the network performance. Systematic investigations of comprehensive reference event databases confirm that the performance of the network will fulfill the treaty verification requirements.

Recent studies have evidenced potential benefits of this network for civil applications. It can for example serve as a component in geophysical hazard warning systems. Furthermore, detailed analyses of the detected low-frequency signals point out new insights on quantitative relationships between observables and atmospheric specifications by applying the mathematics of geophysical inverse problems for atmospheric remote sensing.

 
Freitag, 13.12.2013

Water Vapour Radiometers in Radio Astronomy

Zeit: 10:15 Uhr
Hörsaal: A97
 
Dr. Alan Roy
Max Planck Institute for Radioastronomy
Bonn
Germany

Tropospheric water vapour is problematic for radio astronomical imaging, astrometry, and geodesy since it causes variable absorption and wavefront distortion leading to image blurring, bias, and sensitivity loss. These can often be recovered using self-calibration and increasingly with water vapour radiometers. A number of radio observatories have developed WVRs in the last ten years, especially for short- (millimetre) wavelength astronomy. I will give an overview of design features and performance of some of those with particular detail on our own 22 GHz radiometer at the Effelsberg 100 m radio telescope.

 
Freitag, 20.12.2013

First results from GROMOS-C

Zeit: 10:15 Uhr
Hörsaal: A97
 
Susana Fernandez Vidal
Institute of Applied Physics
University of Bern

Stratospheric ozone is of major interest as it absorbs harmful UV radiation from the sun, thus allowing life on Earth. It also influences the thermal balance of the atmosphere. Ground based microwave remote sensing is the only method that allows to measure ozone profiles up to the mesopause, 24-hours and under different weather conditions. In this seminar I will present a new ground based microwave radiometer, called GROMOS-C (GRound based Ozone MOnitoring System for Campaigns), which is designed to measure the vertical profile of ozone distribution in the middle atmosphere, by observing ozone emission spectra at a frequency of 110.836 GHz. The instrument is designed in a compact way which makes it transportable and suitable for campaign use, an advantageous feature that is lacking in present day ozone radiometers. GROMOS-C is a total power radiometer which uses a preamplified single sideband heterodyne receiver, and a digital Fast Fourier Transform spectrometer for the spectral analysis. Its quasi-optical system combines an ultra-gaussian feed horn with ellipsoidal and flat mirrors to couple different calibration loads into the optical path. Calibration is performed with a classical hot-cold concept. However instead of using a liquid nitrogen load a new cold calibration load was specifically designed and constructed for this instrument. It is based on a wedge geometry with an optimal millimeter-wave absorber at the desired frequency which is cooled with Peltier-elements. As the calibration scheme does not depend on the use of liquid nitrogen, GROMOS-C can be operated also at remote places. The radiometer concept further allows also to use a noise diode for calibration as a super-hot target. The noise is coupled into the receiver before the RF amplification stage, and calibrated periodically with the hot and cold loads. A description of the main characteristics of GROMOS-C and the results of the first tests and spectra measurements will be presented.