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: 17.03.2017
FS 2014: 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, 14.02.2014

IAP day 2014

Zeit: 11:15 Uhr
Hörsaal: 099
 

link to Website: iapday2014

 
Freitag, 21.02.2014

Polarimetric calibration of SPIRA

Zeit: 10:15 Uhr
Hörsaal: A97
 
Marco Canavero
Institute of Applied Physics
University of Bern

Polarimetric radiometers (commonly referred as Polarimeters), which can measure the full spectra of incoming polarization from a target, are nowadays very common in atmospheric physics, astronomy and military applications. Such instruments can provide useful information about characteristics of matter analyzing the polarization characteristics of the electromagnetic waves radiated by the target. In order to obtain the correct Stokes parameters, which describe the incoming radiation from a target and its polarization state, the polarimeter must be calibrated in both total power and polarimetric sense. Generally, the polarimetric calibration must take in account any unbalance and imperfections in the instrument’s optics and receiver. In the talk it will be discussed the different techniques in order to polarimetrically calibrate SPIRA, the fully polarimetric imager operating in the W-Band of the spectrum here in IAP, presenting the novel method which takes advantage of the off-axis reflector configuration of our instrument.

 
Freitag, 28.02.2014

The Absorption Lookup Table and the Cloudbox: two features of the radiative transfer software ARTS

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

The talk will be divided into parts (one in the morning, the other in the afternoon at 14:15), each one covering a feature of the ARTS software: The Absorption Lookup Table and the Cloudbox.
The Absorption Lookup Table is a method to reduce the computing time of the radiative transfer simulations by precalculating the atmospheric absorption. Depending on the setup of the simulation, the time reduction can be substantial while the error introduced to the simulated brightness temperature is only very small. I will explain what the idea behind the lookup table is and how it works. Then, I will show in a hands-on demonstration how you can create your own absorption lookup table and also what you need to change in your forward simulation setup to use it. To conclude the first part of the talk, I will show what is important in the table setup to keep the introduced error as small as possible.
The second part will be about scattering calculations. ARTS is capable of including scattering in the radiative transfer simulations and can also handle polarisation using the Stokes formalism. The region of the model atmosphere where scattering can happen is called Cloudbox. I will explain this in more detail and show how clouds are defined in ARTS. The user can choose between two modules for the scattering calculations: A discrete ordinate iterative method (DOIT) and a Monte Carlo approach (MC). I will summarise the most important points of both modules and show their basic principle.

 
Freitag, 14.03.2014

Atmospheric water parameters in the WRF model and in observations

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

This seminar is divided in two parts. In the first part, after introducing the atmospheric water cycle and explaining the importance of water vapour and clouds for the climate system, I will focus on the parameterizations used in numerical models to represent cloud-related processes, the so-called microphysical schemes. I will show a comparison of several microphysical schemes implemented in the Weather Research and Forecasting (WRF) model using a simple idealized simulation. Only the differences in the water cycle parameters are evaluated and no ranking of the schemes is established, for the results of an idealized simulation cannot be compared with observations. In the second part, however, I will present a comparison of the results of a real-case WRF simulation with instrumental data taken with the TROWARA microwave radiometer. TROWARA measures Integrated Water Vapour (IWV) and Integrated cloud Liquid Water (ILW) at Bern since 1994, providing a high-resolution 20-years-long series of continuous measurements. TROWARA data is valuable for assessing whether WRF microphysical schemes correctly reproduce part of the water cycle. In particular, I will compare TROWARA's IWV and ILW with WRF simulations of the summer 2012 in Switzerland.

 
Freitag, 21.03.2014

Characterization of Atmospheric Aerosol Hygroscopicity by Raman Lidar

Zeit: 10:15 Uhr
Hörsaal: A97
 
Prof. Lucas Alados-Arboledas
Andalusian Institute for Earth System Research
and Department of Applied Physics, University of Granada, Spain

Aerosol particles are a key atmospheric component regarding its contribution to climate change. They affect the Earth-Atmosphere energy budget by means of direct and indirect effects. An improved knowledge about the effects of the size increase of the aerosol particles due to water uptake (hygroscopic growth) is necessary for better understanding these effects. There are already many in-situ studies about the hygroscopic effects on the aerosol properties. Under ambient conditions, analysis have usually been performed using humidified nephelometers or humidified tandem differential mobility analyzers. These instruments are unable to provide accurate results above 85% relative humidity (RH) and they modify the ambient conditions by drying the air sample and then exposing it to varying RH. Remote sensing systems can overcome these difficulties, e.g, by sampling the atmosphere without modifying ambient conditions. The combination of aerosol backscatter (or extinction) and relative humidity profiles retrieved from remote sensing systems and radiosounding represent the required information to perform hygroscopic studies. Appropriate constrains must be applied to the experimental conditions to guarantee the detection of a hygroscopic growth event. In this seminar, we illustrate the feasibility of characterizing the aerosol hygroscopic effect by a combination of Raman lidar and radiosounding (RS) data over the city of Granada (37.16ºN, 3.60ºW and 680 m asl).

 
Freitag, 04.04.2014

An update on the daily cycle in stratospheric ozone: results of modelling, global reanalysis and microwave radiometry

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

Biases in satellite-based ozone trend analysis due to measurements at different local time and drifting satellite orbits recently renewed the interest in diurnal variations of stratospheric ozone. Stratospheric ozone at 5 hPa shows diurnal variation of about up to 5 % at low and mid latitudes in observation from ground-based radiometry and space-borne instruments. Model simulations of the Whole Atmosphere Community Climate Model (WACCM) carried out at the IAP at Bern showed that ozone enhancement over daytime bases mostly on photochemical processes but also on temperature, atmospheric composition and dynamics. These global simulations indicate also a strong daily ozone cycle of up to 15 % at the polar circle in summer. Most recently, simulation results of WACCM were intercompared to reanalysis data of the MACC project which assembles stratospheric ozone from space-borne observations and calculates the feedback of ozone to temperature and dynamics. Aside data of the chemistry-climate model WACCM, the IAP holds an invaluable data set of 17 years of GROMOS observations which was utilized to derive a climatology of diurnal variation of stratospheric and mesospheric ozone over Bern, Switzerland. The presentation will summarize present research on diurnal variation in stratospheric ozone by modeling, reanalysis and observations.

 
Freitag, 18.04.2014

Easter holiday (Good Friday)

Zeit: 10:15 Uhr
Hörsaal: A97
 

 
Freitag, 25.04.2014

Easter holiday

Zeit: 10:15 Uhr
Hörsaal: A97
 

 
Freitag, 09.05.2014

Measurement of the atmospheres of Europa, Ganymede, and Callisto

Zeit: 10:15 Uhr
Hörsaal: A97
 
Prof. Dr. Peter Wurz
Physics Institute
Space Research & Planetary Sciences
University of Bern

The regular Jovian satellites are believed to be formed at the end of Jupiter's formation epoch, from the collisional accretion of solids originating in the Solar Nebula, and captured in a disk orbiting around the planet. The solids taking part to the formation of the satellites therefore originate from the initial protoplanetary disk, and have probably experienced lower temperature and pressure conditions as has the material incorporated in Jupiter, and their chemical composition has been probably less altered. By measuring the composition of the Jovian satellites, it is therefore possible to set constraints on the chemical composition of building blocks of planets and satellites, and ultimately on the thermodynamical conditions in the Solar Nebula.

The Particle Environment Package (PEP) suite has been selected for the JUICE mission of ESA, which contains instruments for the comprehensive measurements of electrons, ions and neutrals. One of the instruments is the Neutral and Ion Mass spectrometer instrument (NIM). NIM is a time-of-flight neutral gas and thermal ion mass spectrometer optimised for exospheric investigations. NIM will measure the composition of the exospheres of Europa, Ganymede, and Callisto. Various physical processes are acting on the surfaces of Jupiter’s icy moons to promote material from the surface into the exosphere. These processes are modelled in detail to relate the exospheric measurements to the surface composition of these moons.