Microwavephysics and Atmospheric Physics
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Biomedizinische Photonik
Ultrafast Science and Technology
Last update: 03.04.2017
FS 2016: Seminare über Microwavephysics and Atmospheric Physics
Friday 10-12
Vorträge, die innerhalb der nächsten Tage stattfinden, sind speziell markiert.
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Freitag, 26.02.2016

Ultra High Field Magnetic Resonance Imaging

Zeit: 10:15 Uhr
Hörsaal: A97
 
Dr. Irena Zivkovic
Max Planck Institute for Biological Cybernetics
Tübingen, Germany

Magnetic Resonance Imaging (MRI) is a modern medical diagnostic tool. MRI does not put any strain on the health of the person being examined which is not a case with X ray diagnostics, computer tomography (CT) or positron emission tomography (PET). With MRI technique it is possible to perform traditional imaging (which reveals anatomical structures) as well as functional MRI (fMRI) which detects neuronal activation. MRI is also very useful for mapping neurochemical and neurobiological processes directly. In order to perform advanced measurements magnetic field stronger than that of clinical instruments is necessary. In our institute two ultra high-field MRI systems were acquired – a whole body MR system with a field strength of 9.4 Tesla for human studies and 14.1 Tesla MR system for animal studies. Basics of MRI technique and advantages of using ultra high field scanners will be presented.

 
Freitag, 04.03.2016

Development of a 71-116GHz RF module for the EMIR receiver upgrade

Zeit: 10:15 Uhr
Hörsaal: A97
 
Dr. Anne-Laure Fontana
IRAM (Institut de RadiAstronomie Millimetrique)
Grenoble, France

IRAM is an institute of Radioastronomy operating two Observatories: the NOEMA interferometer, currently composed of seven 15-m diameter antennas in the South Alps, in France, and which will be extended to twelve antennas in the coming years, and the Pico Veleta Radiotelescope, a 30-m diameter single dish antenna located in the Sierra Nevada Mountains, in Spain. Each of these Observatories is equipped with instruments allowing observations at wavelengths comprised between ~0.8mm to ~4mm.

At the end of 2015, the Eight MIxers Receiver (EMIR), which was installed at Pico Veleta Telecope in 2009, was upgraded to cover almost the full 3mm atmospheric transmission window observable at Pico Veleta, e.g. the 71-116GHz band. EMIR is composed of four cryogenic dual polarization SIS RF modules covering frequencies from 71GHz to 365GHz and implemented in a single cryostat. Outside EMIR cryostat, some switchable dichroic filters can be inserted in the optical path to allow simultaneous dual band observations of the same point of the sky (the possible band combinations are: 3mm+2mm band, 3mm + 1.3mm band and 2mm + 0.8mm band). EMIR has it own calibration system, composed of ambient and cryogenic (15K) loads and of a set of focusing mirrors used to fold the beams on the various loads.

To upgrade the 3mm band, the former 3mm cryogenic module, designed for the 84-116GHz band, was replaced by a new one composed of : - a pair of focusing mirrors, which ensure a frequency indepedant illumination of the Telescope ; - a corrugated feed horn with circular waveguide output coupled to a waveguide Ortho Mode Transducer (OMT) which diplexs the two linear orthogonal polarizations of the receiver ; - Two side band separating SIS mixers with integrated IF couplers delivering four 4-12GHz IF channels. The overall EMIR system will be presented, and the upgraded 3mm module will be detailed.

 
Freitag, 18.03.2016

Defense of PhD thesis: Three-dimensional Simulations of the Ozone Layer and Atmospheric Dynamics of Earth-like Habitable Planets

Zeit: 14:15 Uhr
Hörsaal: B5
 
Elisavet Proedrou
Institute of Applied Physics
and Center for Space and Habitability
University of Bern

 
Freitag, 25.03.2016

no seminar (Easter holiday)

Zeit: 00:00 Uhr
Hörsaal:
 

 
Freitag, 01.04.2016

no seminar (Easter holiday)

Zeit: 00:00 Uhr
Hörsaal:
 

 
Freitag, 08.04.2016

Chemistry-Climate Models: Assessing performance and sensitivities

Zeit: 10:15 Uhr
Hörsaal: A97
 
Prof. Peter Braesicke
Institut für Meteorologie und Klimaforschung
Karlsruher Institut für Technologie KIT
Karlsruhe, Germany

Chemistry-Climate Models (CCMs) are essential tools for our understanding of past composition changes in e.g. stratospheric ozone. We can use them to assess how composition changes can affect climate. The talk will show examples of sensitivity studies and how they aid our understanding of the coupled climate system, including composition feedbacks. An outlook will be given towards the next generation of CCMs currently under development.

 
Freitag, 15.04.2016

Climate impacts of atmospheric aerosols - characterization of key aerosol properties in field experiments

Zeit: 10:15 Uhr
Hörsaal: A97
 
Dr. Martin Gysel
Aerosol Physics Group
Paul Scherrer Institute PSI
Villigen

Atmospheric aerosol particles are emitted from natural and anthropogenic sources. They influence the earth climate directly through extinction of solar radiation. Results from field experiments to characterize the scattering and absorption coefficient of atmospheric aerosols will be presented, including the effects of high relative humidity as well as methodological aspects. Aerosol particles can also act as cloud condensation nuclei or heterogeneous ice nuclei in clouds. The resulting modification of cloud albedo causes a climate forcing, if the particles are of anthropogenic origin. The uncertainties associated with aerosol-cloud interactions remain the major source of uncertainty in our understanding of anthropogenic radiative forcing. Results from our in-situ investigations of aerosol-cloud interactions at the high-alpine Jungfraujoch site in warm and mixed-phase clouds will also be presented.

 
Freitag, 22.04.2016

The natural oscillations in stratospheric ozone observed by the GROMOS microwave radiometer

Zeit: 10:15 Uhr
Hörsaal: A97
 
Lorena Moreira
Institute of Applied Physics
University of Bern

A multilinear parametric regression analysis was performed to assess the seasonal and inter-annual variations of stratospheric ozone profiles from the GROMOS (GROund-based Millimeter-wave Ozone Spectrometer) microwave radiometer at Bern, Switzerland (46.95°N, 7.44°E, 577 m). GROMOS takes part in the Network for the Detection of Atmospheric Composition Change (NDACC). The study covers the stratosphere from 50 to 0.5 hPa (from 21 to 53 km) and extends over the period from January 1997 to January 2015. The natural variability was fitted during the regression analysis through the annual and semi-annual oscillations (AO, SAO), the quasi-biennial oscillation (QBO), the El Niño-Southern Oscillation (ENSO) and the solar activity cycle. Seasonal ozone variations mainly appear as an annual cycle in the middle and upper stratosphere and a semi-annual cycle in the upper stratosphere. Regarding the inter-annual variations, they are primarily present in the lower and middle stratosphere. In the lower and middle stratosphere ozone variations are controlled predominantly by transport processes, due to the long lifetime of ozone whereas in the upper stratosphere its lifetime is relatively short and ozone is controlled mainly by photochemistry. The present study shows agreement in the observed naturally induced ozone signatures with other studies. Further, we present an overview of the possible causes of the effects observed in stratospheric ozone due to natural oscillations at a northern mid-latitude station. For instance regarding the SAO, we find that polar winter stratopause warmings contribute to the strength of this oscillation since these temperature enhancements lead to a reduction in upper stratospheric ozone. We have detected a strong peak amplitude of about 5% for the solar cycle in lower stratospheric ozone for our 1.5 cycles of solar activity. Though the 11-year ozone oscillation above Bern is in phase with the solar cycle, we suppose that the strong amplitude is partly due to meteorological disturbances and associated ozone anomalies in the Northern hemisphere. Further, our observational study gave the result that ozone above Bern is anti-correlated to the ENSO phenomenon in the lower stratosphere and correlated in the middle stratosphere.

 
Freitag, 20.05.2016

Abgesagt! Cancelled!

Zeit: 10:15 Uhr
Hörsaal: A97
 
Dr. Jean-Marie Bettems
Federal Department of Home Affairs FDHA
Federal Office of Meteorology and Climatology MeteoSwiss
Zurich

 
Freitag, 27.05.2016

Defense of PhD thesis: Middle-atmospheric ozone profile measurements by a novel ground-based microwave radiometer for campaigns

Zeit: 14:15 Uhr
Hörsaal: B7
 
Susana Fernandez
Institute of Applied Physics
University of Bern

 
Freitag, 10.06.2016

Cloud Effect on Temperature Profiles from Microwave Measurements

Zeit: 10:15 Uhr
Hörsaal: A97
 
Leonie Bernet
Institute of Applied Physics
University of Bern

The microwave temperature radiometer TEMPERA retrieves atmospheric temperature profiles by measuring emitted radiation of molecular oxygen at 60 GHz. The influence of clouds is low in the microwave spectrum, but the cloud effect can't be neglected at certain frequencies. The project aims to improve temperature measurements from TEMPERA radiometer by incorporating cloud liquid water into the retrievals. For this purpose, clouds are characterized using data from a ceilometer, a HATPRO radiometer and a sky camera, all located in Payerne, Switzerland. It can be shown that the temperature measurements improve when cloud properties from those instruments are included into the TEMPERA retrievals.