Microwavephysics and Atmospheric Physics
FS 2017  ·  HS 2016
FS 2016  ·  HS 2015
FS 2015  ·  HS 2014
FS 2014  ·  HS 2013
FS 2013  ·  HS 2012
FS 2012  ·  HS 2011
FS 2011  ·  HS 2010
Biomedizinische Photonik
Ultrafast Science and Technology
Last update: 03.04.2017
FS 2017: Seminare über Microwavephysics and Atmospheric Physics
Friday 10-12
Vorträge, die innerhalb der nächsten Tage stattfinden, sind speziell markiert.
Änderungen und Korrekturen bitte an Franziska Stämpfli (IAP Sekretariat) melden!
 
Freitag, 24.02.2017

Middle atmospheric wind measurements on La Réunion island by the microwave radiometer WIRA-C and comparison with lidar

Zeit: 10:15 Uhr
Hörsaal: A97
 
Jonas Hagen
Institute of Applied Physics
University of Bern

The passive microwave wind radiometer WIRA-C (Wind Radiometer for Campaigns) has been installed on the Maïdo observatory on the tropical island La Réunion (21° South, France) in August 2016. WIRA-C measures the Doppler shift of the ozone thermal emission line at 142 GHz and exploits the pressure broadening effect to retrieve an altitude resolved wind profile. The retrieval is based on a model of the atmosphere and optimal estimation techniques implemented by ARTS and Atmlab/Qpack. In contrast to previous versions of the retrieval process, the atmospheric model is three-dimensional. Meaningful wind speeds can be retrieved for an altitude range of 30 to 70 km and WIRA-C is able to measure continuously, independent of daylight and clouds. Co-located at the Maïdo observatory is the Rayleigh-Mie Doppler wind lidar of CNRS/INSU (Guyancourt, France) and OSUR (La Réunion, France). It has been operated routinely twice a week since September 2015 and delivers wind profiles up to 50 km altitude. This talk will give an overview over the WIRA-C instrument and the retrieval process involved and present the measured wind profiles from La Réunion island. The measurements will also be compared to ECMWF model data and coincident measurements from the Rayleigh-Mie Doppler wind lidar.

 
Freitag, 10.03.2017

Development and application of a radar target simulator for calibration purposes

Zeit: 10:15 Uhr
Hörsaal: A97
 
Dr. Marc Schneebeli
Palindrome Remote Sensing GmbH
7214 Grüsch
Switzerland

An accurate estimate of the weather radar derived rain rate depends on a thoroughly calibrated radar. However, the continuous determination of the exact value of the radar constant is difficult for a variety of reasons (i.e., wet radome conditions, gain fluctuations etc). The goal of this project is to develop a tool that allows to calibrate the radar without interrupting its operation and to continuously assess variations of the radar constant under all weather conditions. A radar target simulator (RTS) is an external transponder system that is set-up within the coverage of the radar. It receives the radar pulses, applies a predefined Doppler shift and a time delay and sends them back to the radar with a fraction of the received signal power, where this fraction corresponds to a specific radar cross section (RCS). If the fraction of the re-emitted power is sufficiently accurate, the virtual target that appears in the radar display at the distance that corresponds to the applied time delay has a known RCS and can therefore be used to estimate the radar constant. A low-cost RTS prototype has been recently developed. Pulses are received via a standard gain horn and a receiver, which consists of an RF amplifier, three down-conversion stages and an A/D conversion. The digital data stream is sent over a high-speed connection to a host computer, where the signal processing, i.e., the application of the time delay and the Doppler shift, is performed. The data is then converted to analog pulses, up-converted to the target frequency over three stages, amplified and sent back to the radar via the same horn antenna. First laboratory tests with a pulse generator showed that the time, frequency and amplitude stability of the re-emitted pulses is sufficiently high for the foreseen application. For further tests, an old X-band marine radar has been employed. With this test it was confirmed that the RTS can cope with the varying carrier frequency of a magnetron based system. The system has recently been tested with two different magnetron based X-band weather radars. First results of these activities will be presented.

 
Freitag, 17.03.2017

Rayleigh-Mie Doppler lidar for wind measurements in the middle atmosphere: design, performance and observations.

Zeit: 10:15 Uhr
Hörsaal: A97
 
S. M. Khaykin, A. Hauchecorne, J.-P. Cammas, N. Marqestaut, J.-F. Mariscal, F. Posny, G. Payen, J. Porteneuve, P. Keckhut LATMOS-IPSL, Université Versailles St.-Quentin, CNRS/INSU, Guyancourt, France, 2OSUR, UMS3365, Université de la Réunion

A unique Rayleigh-Mie Doppler wind lidar, measuring Doppler shift between the emitted and backscattered light using direct-detection technique is deployed at Haute-Provence Observatory (Southern France) and at Reunion island (tropical Indian Ocean). The instrument was shown capable of wind measurements between 5 and 50 km with accuracy better than 1 m/s up to 30 km. We evaluate instrument’s capacities in capturing fine structures in stratospheric wind profiles and their temporal and spatial variability through comparison with collocated radiosoundings and ECMWF analysis. Perturbations in the wind velocity are used to retrieve gravity wave frequency spectrum. Application of Doppler lidar for validation of the forthcoming ADM-Aeolus satellite mission is discussed as well.

 
Freitag, 17.03.2017

Application of a CubeSat-Based Passive Microwave Constellation to Operational Meteorology

Zeit: 14:15 Uhr
Hörsaal: A97
 
Prof. Dr. A. Gasiewski
University of Colorado at Boulder, Boulder, CO, USA

In their most recent decadal assessment (Earth Application from Space, 2007) of Earth science space missions the U.S. National Research Council identified the Precipitation and All- weather Temperature and Humidity (PATH) mission as one of ten recommended medium cost missions. Based on the NRC’s outlined goals, PATH would have the unique capability of providing all- weather temperature and moisture soundings and cloud and raincell imagery at spatial scales comparable to AMSU-A/B or ATMS, but at sub-hourly temporal resolution. The essential need is to provide the atmospheric penetrability and spatial resolution of operational microwave sensors but with temporal resolution commensurate with the natural rate of evolution of convectively driven weather. This seminar will focus on the merits of a constellation of passive microwave sounding and imaging CubeSats for achieving PATH goals from the multiple viewpoints of calibration accuracy, data assimilation and global sampling, downlink capability and latency, and orbital lifetime and launch availability. Microwave spectral imagery at 50, 118, and 183 GHz with spatial resolution of ~10-30 km and temporal resolution of ~15-60 minutes from such a fleet could be expected to significantly enhance forecasting of mesoscale convective weather and hurricane rain band evolution, along with provide valuable temporal gap-filling data for synoptic weather forecasting. It is argued that from a joint technology, science, and operational standpoint that a cost-effective realization of the PATH goals, but with the additional features of global coverage and improved NWP sensitivity, can be achieved by a low-cost random-orbit constellation of CubeSats supporting the ATMS and 118 GHz bands. The CU PolarCube mission will be discussed as a basis for this fleet concept.

 
Freitag, 24.03.2017

Co-located observations of middle-atmospheric wind by microwave radiometry and lidar

Zeit: 10:15 Uhr
Hörsaal: A97
 
Dr. Rolf Rüfenacht
IAP, Kühlungsborn

Wind is a key parameter characterising the state of the atmosphere and the most direct manifestation of dynamics. Nevertheless there is a substantial lack of wind observations from the upper stratosphere to the mesosphere. Established measurement techniques such as radiosondings, radars or airglow spectrometry cannot assess this altitude range, until recently direct observational knowledge of wind at these altitudes was solely based on rocket-aided techniques. This changed in 2009/2010 when two novel approaches providing much more frequent measurements reached their operational state: Doppler microwave wind radiometry and lidar single-edge iodine spectroscopy on the molecular backscatter signal. These completely independent measurement approaches are operated in co-location at polar latitudes since spring 2016. In this talk I will introduce the lidar and the radiometer method and highlight their advantages and limitations before presenting the first intercomparison of wind observation techniques in the upper stratosphere and mesosphere.

 
Freitag, 31.03.2017

Development of Microwave Calibration Targets for Meteorological Operational Satellites - Second Generation (MetOp-SG)

Zeit: 10:15 Uhr
Hörsaal: A97
 
Dr. Arne Schröder
Institute of Applied Physics
University of Bern

This talk summarizes the development of microwave calibration units for the second generation of meteorological operational satellites (MetOp-SG), developed by ESA and EUMETSAT. In particular, we focus on the design and manufacturing of on-board calibration targets (OBCT) for the microwave sounder (MWS) and the ice cloud imager (ICI), respectively. MWS operates in seven bands between 23GHz and 230GHz, while ICI covers five bands between 180GHz and 670GHz. As the OBCTs act as temperature reference for microwave radiometers, they are required to exhibit a low electromagnetic reflectivity and a uniform temperature distribution. Finding the best trade between these contrary properties is one of the main design challenges. While the electromagnetic analysis and design of OBCTs are well established, methods for simulating the target's brightness temperature, i.e. the temperature observed by the radiometer, are not available. In this talk, we will introduce a numerical technique which allows to compute the brightness temperature of arbitrary shaped targets. Fundamental theoretical investigations regarding various target parameters have been carried out and will be discussed in this contribution. Based on these studies, we have developed a pyramid target layout which reduces temperature gradients without impairing the electromagnetic performance. The designed targets were manufactured and coherent reflectivity measurements were conducted on a quasi-optical bench for the entire frequency spectrum and various incident angles. The experimental studies validate the numerically predicted performance and show that the manufactured OBCT prototypes fulfil the specific RF requirements in all frequency bands.

 
Freitag, 07.04.2017

Development of On-Ground Calibration Targets for the Ice Cloud Imager Instrument of the Meteorological Operational Satellites - Second Generation Programme

Zeit: 10:15 Uhr
Hörsaal: A97
 
Dr. Mikko Kotiranta
Institute of Applied Physics
University of Bern

The Ice Cloud Imager instrument is a scanning microwave radiometer developed as a part of the Meteorological Operational Satellites - Second Generation (MetOp-SG) Programme of the European Space Agency. It will perform cloud ice measurements in multiple frequency channels between 183 GHz and 664 GHz. In addition to the on-board calibration target that will be used as a brightness temperature reference together with the cold sky during the operational phase of the satellites, on-ground calibration targets are being developed to enable radiometric performance and calibration test measurements of the instrument in a thermal-vacuum chamber prior to the satellite launch. Two temperature controlled targets, both exhibiting a high temperature uniformity and a low reflectivity for electromagnetic waves, are needed to represent the observed Earth scene and the cold sky. These targets will take the form of a wedged cavity, and in this talk we discuss the methods and challenges in their design and analysis as well as present experimental results on the first wedge prototype.

 
Freitag, 14.04.2017

no seminar (Easter holiday)

Zeit: 00:00 Uhr
Hörsaal: A97
 

 
Freitag, 21.04.2017

no seminar (Easter holiday)

Zeit: 00:00 Uhr
Hörsaal: A97
 

 
Freitag, 28.04.2017

no seminar EGU

Zeit: 10:15 Uhr
Hörsaal: A97
 

 
Freitag, 05.05.2017

Receiver Unit of SWI/JUICE: Design and first measurements of the Calibration Hot Load and optics

Zeit: 10:15 Uhr
Hörsaal: A97
 
Karl Jacob
Institute of Applied Physics
University of Bern

 
Freitag, 12.05.2017

tba

Zeit: 10:15 Uhr
Hörsaal: A97
 
tba

 
Freitag, 19.05.2017

tba

Zeit: 10:15 Uhr
Hörsaal: A97
 
tba

 
Freitag, 26.05.2017

tba

Zeit: 10:15 Uhr
Hörsaal: A97
 
tba

 
Freitag, 02.06.2017

Promotions-Vortrag

Zeit: 14:15 Uhr
Hörsaal: B
 
Martin Lainer