Microwavephysics and Atmospheric Physics
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Last update: 18.10.2017
HS 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, 21.09.2012

Präsentation der Masterarbeit: Post-Processing techniques for radiometric images and polarimetric ray tracing

Zeit: 10:15 Uhr
Hörsaal: A97
 
Stefan Siegenthaler
Institute of Applied Physics
University of Bern

 
Freitag, 28.09.2012

Diurnal variations in ozone as observed by GROMOS above Bern

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

Research on ozone variability in recent years has mainly focused on the analysis of ozone trends. Diurnal changes in stratospheric ozone are less explored and a comprehensive picture of diurnal ozone variations in the middle atmosphere does not exist. However, knowledge of the diurnal ozone cycle is required for the correction of systematic errors in long-­term timeseries of stratospheric ozone merged from satellites in different sun-­synchronous orbits. The ground-­based millimeter-­wave ozone spectrometer GROMOS retrieves ozone profiles from approximately 20 to 65 km at Bern since 1994 in the frame of the Network for the Detection of Atmospheric Composition Change (NDACC). Continuous night-­ and daytime measurements of GROMOS allow us to derive the mean diurnal cycle of ozone, which depends on dynamics (e.g. transport) and chemistry (e.g. photodissociation). In the seminar, I will give an introduction and will present and discuss the derived diurnal ozone cycle at Bern for different seasons.

 
Freitag, 05.10.2012

Orographic effects on precipitation and atmospheric water cycle in the Weather Research and Forecasting Model

Zeit: 10:15 Uhr
Hörsaal: A97
 
Federico Cossu
Institute of Applied Physics
University of Bern

Regional Climate Models (RCM) simulate the effects of local orography on precipitation and clouds much better than Global Climate Models (GCM) thanks to their higher spatio-temporal resolution. However, a RCM still needs parameterizations for microphysical processes such as the evolution of cloud droplets into rain or snowfall. Sometimes these parameterizations are well suited for short-term forecasts but their effect on long-term climate simulations can introduce large errors. Our objective is to assess the fundamental characteristics of different schemes of microphysics by performing an idealized simulation with the Weather Research and Forecasting (WRF) model. The knowledge of the effects of parameterization on the atmospheric water cycle is required to enhance the quality of long-term RCM simulations. In the seminar I will first explain the physical processes responsible for the generation of clouds and precipitation in the atmosphere and how they can be parameterized through microphysical schemes. Then I will talk about the importance of the water cycle in today's climate simulations. Finally I will describe the setup chosen for our simulations, present the results and give an outlook for the future.

 
Freitag, 19.10.2012

Modelling of orographic precipitation THIS SEMINAR IS CANCELLED!

Zeit: 10:15 Uhr
Hörsaal: A97
 
Dr. Assela Pathirana
UNESCO-IHE Institute for Water Education

THIS SEMINAR IS CANCELLED!

 
Freitag, 26.10.2012

Promotionsvortrag: Retrieval of tropospheric and middle atmospheric water vapour profiles from ground based microwave radiometry

Zeit: 15:15 Uhr
Hörsaal: B7
 
René Bleisch
Institute of Applied Physics
University of Bern

 
Freitag, 02.11.2012

Variability of middle atmospheric water vapor on timescales from days to weeks

Zeit: 10:15 Uhr
Hörsaal: A97
 
Dominik Scheiben
Institute of Applied Physics
University of Bern

At the Institute of Applied Physics, middle atmospheric water vapor has been measured for many years by ground-based microwave radiometry. Currently, there are three instruments dedicated to such measurements. The observations can be used to study the temporal and spatial variability of the middle atmosphere. Since water vapor has a long chemical lifetime, it is often used as a tracer to study middle atmospheric dynamics. The first part of my talk will consist in a case study on middle atmospheric transport processes during the sudden stratospheric warming of 2010, as observed from Bern, Onsala and Sodankyla. The short-term anomalies in our observations reflect meridional advection of stratospheric and mesospheric air and polar vortex displacements. Additionally, an approach to combine observations from ground-based instruments from different locations into one synoptical map is presented. The second part of the talk is dedicated to diurnal variations in middle atmospheric water vapor. Ground-based instruments are well suited for studying diurnal variations, since they are operating continuously during all hours of the day. The diurnal variations obtained from our observations are compared to data from the chemistry-climate model WACCM. With WACCM, we made a decomposition of the diurnal cycle into contributions from meridional, zonal and vertical advection and (photo-)chemistry

 
Freitag, 23.11.2012

A global view on the diurnal variation of stratospheric ozone

Zeit: 10:15 Uhr
Hörsaal: A97
 
Ansgar Schanz
Institute of Applied Physics
University of Bern

For a long time the IAP microwave group is researching the atmosphere and its composition with remote sensing techniques. Several instruments are measuring watervapour and ozone from the stratosphere up to the mesosphere by ground-based microwave radiometry. In spring 2012, the group started to work with Whole Atmosphere Chemistry Climate Model (WACCM) which is a powerful tool for middle-atmospheric research in addition to our observations.

In the Seminar, I will give an overview to WACCM and the local installations at UniBe. I will present a first analysis of simulations focusing on diurnal variations of ozone in the middle atmosphere. In contrast to our ground-based instruments, the model provides global data coverage which gives a more expansive view of the diurnal cycle. The simulated stratospheric ozone shows a maximum in concentration all-season at late afternoon. With the GROMOS instrument this effect is observed too espacially during the winter seasons. In order to study the origin and the extend of the maximum, the model can be forced to provide more information about reaction rates of the ozone chemistry. A decomposition of model chemistry at 4 hPa shows that the diurnal cycle is governed by the Chapman Cycle and depleting reactions which include NO and Cl.

 
Freitag, 30.11.2012

Temperature profiles from the ground to the stratopause with TEMPERA

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

With the new Temperature Radiometer TEMPERA it is possible to measure temperature profiles from ground to about 50 km. This instrument was built at our Institute and since 2012 it is measuring continuously in our lab on the roof. TEMPERA operates in the frequency range from 51 to 57 GHz in the oxygen-emission region of the microwave spectrum. The spectral analysis is done with a filterbank with 12 channels for the troposphere and with a digital FFT spectrometer which measures two oxygen-emission lines around 53 GHz with 32000 channels for the stratosphere. In the measured spectra the influence of the zeeman effect can be seen. In the presentation I firstly present the motivation and the design of TEMPERA. The second part consists of a short theory of the temperature retrieval. Following this I will show the results over the first half year of 2012 which are also compared with radiosonde and satellite data (MLS). Finally I will give an outlook for future work.

 
Freitag, 07.12.2012

Retrieval of aerosol optical depth from the Advanced Very High Resolution Radiometer (AVHRR) over Europe

Zeit: 10:15 Uhr
Hörsaal: A97
 
Dr. Michael Riffler
Oeschger Centre for Climate Research
University of Bern

Aerosols are a key component in the Earth's atmosphere influencing the radiation budget due to scattering and absorption of solar and terrestrial radiation and changing cloud physics by serving as cloud condensation and ice nuclei. Estimating the consequences and feedbacks based on these effects is still a field of large uncertainties.

In addition to ground-based and in situ measurements, an increasing number of satellite observations has helped to extend our knowledge of the dispersed particles over the past years. Some of the sensors were specifically designed for aerosol research, others were initially foreseen for different purposes. The Advanced Very High Resolution Radiometer (AVHRR) is among the latter. It is of particular interest as a heritage sensor already providing more than 30 years of satellite data. Up to now, AVHRR-based climatologies of aerosol optical depth (AOD) are constrained to surfaces with low reflectance and well-known spectral properties like oceans or large water bodies. Problems associated with aerosol remote sensing over land include that the heterogeneous land surfaces are brighter with inhomogeneous and a priori unknown reflectance characteristics and, in addition, the magnitude of the backscattered signal from the particles is smaller than over dark surface types.

Within this seminar talk, I will focus on the retrieval technique and challenges faced by using AVHRR data to derive AOD over land surfaces. In addition, I will present some case studies based on the AVHRR AOD data set and problems which need to be solved before a climatology over European land surfaces can be presented.

 
Freitag, 14.12.2012

Diurnal chemistry of atmospheric compositions from upper stratosphere to the top of the atmosphere investigated by the observation of Superconductive Submillimeter-wave Limb Emission Sounder(SMILES) from International Space Station

Zeit: 10:15 Uhr
Hörsaal: A97
 
Prof. Yasuko Kasai
National Institute of Information and Communications Technology (NICT)
Tokyo, Japan

We performed observation of atmospheric short-lived species, such as HO2, HOCl, ClO, BrO, as well as HCl and O3, using the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES), attached to the Japanese Experiment Module (JEM) on the International Space Station (ISS) during 12 October 2009 and 21 April 2010. SMILES employed a 4 K superconducting mixers for 600 GHz submillimeter-wave passive observation, and its sensitivity is one order magnitude better than the past similar satellite instruments. I will show you the radical chemistry in the vertical region from upper stratosphere to the top of the atmosphere, which revealed by SMILES observation for the first time.