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Last update: 03.04.2017
FS 2012: Seminare über Microwavephysics and Atmospheric Physics
Friday 10-12
Vorträge, die innerhalb der nächsten Tage stattfinden, sind speziell markiert.
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Freitag, 24.02.2012

Research and development at millimetre wave bands

Zeit: 10:15 Uhr
Hörsaal: A97
 
Dipl.-Ing. Denis Nötel
Teamleader Radiometry
Millimetre Wave Radar and High Frequency Sensors
Fraunhofer Institute for High Frequency Physics and Radar Techniques FHR
Wachtberg, Germany

MEMPHIS, COBRA and SUMATRA are the names connected with three consecutive generations of versatile radar sensors at Fraunhofer FHR. The Department of Millimetre Wave Radar and High Frequency Sensors (MHS) has realized these sensors from the conceptual beginnings to the RF frontend and digital backend designs. In the same group, the sensors are in use for a wide range of measurement applications in projects and co-operations, covering frequency ranges from 10 GHz over 35, 94 and up to 210 GHz. Recently, these airborne radar sensors have been complemented with systems for specific purposes like material probing, airport runway safety and security imaging. The purpose of this presentation is to deliver an insight into the mmW system developments conducted at Fraunhofer FHR/MHS.

 
Montag, 27.02.2012

Promotionsvortrag: Campaign based measurements of middle atmospheric water vapor using the ground based microwave radiometer MIAWARA-C

Zeit: 14:15 Uhr
Hörsaal: 119
 
Corinne Straub
Institute of Applied Physics
University of Bern

 
Freitag, 02.03.2012

Numerical studies on ozone and NOx production by mesospheric lightning

Zeit: 10:15 Uhr
Hörsaal: A97
 
Dr. Yasutaka Hiraki
National Institute for Fusion Science (NIFS)
Toki Gifu 509-5292
Japan

Mesospheric lightning called sprites are known to be induced by intense tropospheric lightning, covering an altitude range of 40 to 100 km. Its horizontal scale is larger than tens of kilometer, while the duration is very short as 10-100 milli-seconds. It has been identified as a cold discharge where electrons are highly accelerated, electron avalanche occurs through impact ionization, and various chemical reactions are excited. We have made a one-dimensional ion-neutral chemical reaction model to treat the non-thermal electron processes and estimate the amounts of produced ozone and NOx species. In this seminar, I would introduce details of this phenomenon and calculated results of ozone and NOx production, along with a discussion on its effect on ozone chemistry.

 
Freitag, 09.03.2012

A new window to the Universe: Gravitational Waves

Zeit: 10:15 Uhr
Hörsaal: A97
 
Dr. Hyunjoo Kim
Max-Planck-Institut für Gravitationsphysik
Hannover
Germany

I present an overview of the current status of Gravitational wave searches in direct detection methods of both laser interferometer technique and pulsar timing. These methods are dedicated to the detection of gravitational waves and pioneering the new field of gravitational wave astronomy. This talk will briefly describe the nature of gravitational waves, possible astrophysical sources of detectable gravitational waves such as merging pairs of black holes and neutron stars, supernovae and the big bang, and how laser interferometers and pulsar timing method works. And finally, I present the Einstein@Home project, a volunteer distributed computing project. Einstein@Home searches for radio pulsars (or binary pulsars) through data from the Arecibo Observatory and Parkes Observatory. The results from the radio pulsar search enable us to improve our understanding of how many binaries with neutron stars may be out there and to increase the probability of detecting gravitational waves by finding more sources of gravitational waves.

 
Freitag, 16.03.2012

Role of Observations in Understanding Climate Sensitivity and Climate Feedbacks

Zeit: 10:15 Uhr
Hörsaal: A97
 
Dr. Andrew Gettelman
National Center For Atmospheric Research
1850 Table Mesa Dr, Boulder, CO, USA
Currently on Sabbatical @ ETH Zurich

The sensitivity of future climate to radiative forcing is dependent on different climate feedbacks. Uncertainty in the feedbacks is the largest contribution to uncertainty in future climate projections. It is often difficult to use observations to attempt to constrain these feedbacks. The presentation will discuss the basic issues with feedbacks, particularly of water vapor and clouds, and focus on how observations can (and cannot) be used to constrain these feedbacks. For water vapor feedbacks, there seem to be good analogs and constraints, but cloud feedbacks are very difficult to constrain with observations, and remain the largest uncertainty in climate projections.

 
Freitag, 23.03.2012

First results from the microwave Doppler radiometer WIRA

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

Despite the high wind velocities encountered in the middle atmosphere there is currently no continuously running instrument for wind measurements between 40 and 70 km altitude. Still, such observations could provide a deeper insight in the dynamics and transport processes and a better understanding of the coupling between the upper and lower atmosphere.

As a contribution to the closing of this data gap our new ground-based wind radiometer WIRA started its routine operation in September 2010. The radiometer measures the emission of ozone at 142 GHz wherefrom the Doppler shift can be determined to conclude on the horizontal wind speeds in the stratosphere and mesosphere. The first part of the talk will give an overview of WIRA's instrumental properties. Further, the methods for retrieving altitude dependent wind speeds from the measured spectra will be discussed, before a first time series of 11 months of wind data over Bern is presented and compared to ECMWF operational analysis data.

 
Freitag, 20.04.2012

Application of ground-based microwave radiometers to operational meteorology: from 1DVAR to networking

Zeit: 10:15 Uhr
Hörsaal: A97
 
Dr. Domenico Cimini
Institute of Methodologies for Environmental Analysis (IMAA)
Italian National Research Council (CNR)
L'Aquila
Italy

Ground-based microwave radiometer profilers (MWRP) operating in the 20-60 GHz range are nowadays commercially available, and continuous thermodynamic profiles are retrieved by operational MWRP at numerous sites world wide. In the last years, the feasibility of a One-Dimensional Variational (1DVAR) technique applied to MWRP observations has been demonstrated. The 1DVAR approach avoids error inherent in other retrieval methods and benefits from recent surface, radiosonde, satellite, radar and other data residing in the local analysis/forecast. Recently, this technique has been applied to observations from the MWRPs deployed at Whistler, British Columbia, operated by the Meteorological Service of Canada (MSC) and at Lindenberg, Germany, operated by the German Weather Service (DWD). In this presentation, we show the 1DVAR results obtained during these deployments, comparing the products with radiosonde profiles to quantify the achieved accuracy with respect to other traditional methods. Finally, we discuss the potential of 1DVAR technique for a large scale network of MWRP currently being established.

 
Freitag, 27.04.2012

New challenges in mm and sub-mm astronomy optical system design and its experimental verification: the B-Polarisation satellite

Zeit: 10:15 Uhr
Hörsaal: A97
 
Dr. Massimo Candotti
National University of Ireland, Maynooth

The B-Pol instrument is characterised by a complete refractive optical system for a receiver potentially capable of detecting the B-mode component of the polarized Cosmic Microwave Background (CMB) anisotropy. The major challenge of such optical design is represented by the measurement of polarisation with a high degree of purity, together with a large focal surface area to maximise the number of detectors. The instrument design presented here provides a separate telescope barrel for each of the 5 frequency bands (70, 100, 143, 217 and 353 GHz), with a half field of view of 9.5° on the sky. The optical system is based on a modified Petzval camera design meeting the stringent scientific requirements on dual orthogonal beam purity. The focal surface can accommodate sufficient detectors to meet or exceed the instrument sensitivity requirements for a four-year mission scenario, assuming the incorporation of ultra-Gaussian feed-horns. To accurately characterise the systematic errors introduced by the optical system affecting the orthogonal beam differential effects, specific near-field measurements will be required in terms of precise alignments of the optics under test and the near-field measurement plane. A summary of the test set-up and procedures, essential to validate the simulation results, will be finally discussed.

 
Freitag, 04.05.2012

A study of the Molecular Envelope of the Red Supergiant Betelgeuse

Zeit: 10:15 Uhr
Hörsaal: A97
 
Elisavet Proedrou
Argelander-Institut für Astronomie
Universität Bonn
Germany

Betelgeuse, the second brightest star in the Orion constellation, is a Red Supergiant with an extended Circumstellar Envelope (CSE). New observations of the CO and 13CO (sub)millimeter lines, conducted with the APEX telescope, the JCMT telescope, and the Herschel Space Observatory have managed to penetrate deeper than ever before into the CSE. I reduced, analysed, and conducted radiative transfer modelling of the observed spectral lines, in an attempt to derive the main physical parameters of the cold molecular envelope. The radiative transfer modelling was conducted with the Radiative Transfer and molecular excitation code RATRAN.

 
Freitag, 11.05.2012

Ground-based observation of the atmospheric composition in the infrared and microwave spectral region

Zeit: 10:15 Uhr
Hörsaal: A97
 
Prof. Dr. Justus Notholt
Institute of Environmental Physics
University of Bremen
Germany

The ground-based remote sensing has been established as a powerful tool for atmospheric studies. Using the sun or moon as light source, or working in emission allows measuring the total column concentrations of more than 30 trace gases. For a few trace gases the analysis of the spectral line shape of isolated spectral lines allows to retrieve the concentration profiles in the atmosphere. We perform such measurements in the infrared and microwave spectral region at several sites, from the high Arctic in Spitsbergen via mid-latitudes to the tropics in Suriname. Results from the different sites will be presented. Our research topics are investigations on the carbon cycle in troposphere, the stratospheric ozone chemistry, and transport processes in the upper stratosphere/mesosphere

 
Freitag, 25.05.2012

Results from the measurement campaigns of MIAWARA-C at Zimmerwald and Sodankylä

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

The Institute of Applied Physics is operating three ground-based 22 GHz radiometers for middle atmospheric water vapor, namely MIAWARA, SWARA and MIAWARA-C. Over the last years all three instruments have been optimized allowing to retrieve water vapor profiles with temporal resolution in the order of several hours. In contrast to the other two instruments MIAWARA-C is not designed for long term monitoring but for the use on measurement campaigns. These campaigns can focus on intercomparison of instruments, on the observation of atmospheric processes or on a combination of both. In this talk I will focus on the previous and on the current campaigns of MIAWARA-C. The Zimmerwald campaign in 2010/11 offers the unique opportunity to do a side by side intercomparison of the similar instruments MIAWARA and MIAWARA-C. During this campaign the receiver of MIAWARA-C was updated from a cross-correlation to a dual-polarization receiver leading to a remarkable increase in the temporal resolution. The data obtained in Zimmerwald and in Sodankylä in 2010 is used to perform a thorough intercomparison study including satellite data. In addition, first results of the current campaign are presented.

 
Freitag, 01.06.2012

Excursion to MeteoSwiss at Payerne

Zeit: 08:08 Uhr
Hörsaal: MeteoSwiss
 
Scientists from MeteoSwiss

We invite you to the Microwave Department's annual excursion to visit MeteoSwiss at Payerne. There we have the possibility to see the meteorological station and a ballon sounding. In the morning we will make a light walking tour of about 1.5 hours through the roman heritages of Avenches. Thereafter we continue by train to Payerne and have lunch at the Mensa of MeteoSwiss. After the visit we enjoy the cultural aspect of the village of Payerne. We will be back at Bern at 18:00.

Travel Details: Train from Bern to Avenches (via Murten): 1 June 2012; Departure: 08:08 - Platform 12A - Back Train Section (Direction: Murten)

Those who wish to attend the excursion must register by email - oliver.staehli@iap.unibe.ch - before Tuesday 29th May 2012 at 12.00 and please mention whether you have a half price ticket or an GA (General-Abo).