Microwavephysics and Atmospheric Physics
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HS 2011: Seminare über Microwavephysics and Atmospheric Physics
Friday 10-12
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Freitag, 23.09.2011

NASA satellite studies of water vapor and cirrus clouds in the tropical tropopause layer

Zeit: 10:15 Uhr
Hörsaal: A97
Dr. Thomas Flury
Aerosol and Cloud Science
NASA-Jet Propulsion Laboratory
Pasadena CA, USA

Water vapor in the tropical tropopause layer (TTL) has a significant radiative cooling effect on the Earth's climate system. As a source for cirrus clouds, however, it can also indirectly produce infrared heating. The amount of water vapor in the TTL is strongly controlled by temperature with a seasonal cycle of about 1 - 2 ppm vmr in amplitude at 100 hPa and minimum values in northern hemisphere winter. NASA A-Train satellite measurements by CALIPSO and Aura/MLS reveal that the cirrus seasonal cycle is highly anticorrelated with the water vapor variation in the TTL, showing higher cloud occurrence during northern hemisphere winter. I will show that the high anticorrelation occurs generally in the Intertropical Convergence Zone. The seasonal cycle of the cirrus ice water content is also highly anticorrelated to water vapor and the results I am going to present support the hypothesis that the total water is roughly constant in the TTL at 100 hPa, meaning that the source of water, which is convection, has no strong seasonal cycle. Temperature acts as a main regulator for balancing the partition between water vapor and cirrus clouds. Thus, to a large extent, the depleting water vapor in the TTL during NH winter is a manifestation of cirrus cloud formation. Further I will show an example of a well known general circulation model which does neither yield conservation of total water nor the right partitioning between ice and vapor. Since vapor and ice have opposite effects on Earth's radiative balance our results might help to reduce uncertainty in future climate model forecasts if models can be better tuned to the observations.

Freitag, 14.10.2011

Analysis and Simulation of Edge Effects of Focal Plane Array Facet Reflectors with High Filling Factor

Zeit: 10:15 Uhr
Hörsaal: A97
Matthias Renker
Institute of Applied Physics, University of Bern

We present the concept of high relative beam proximity facet reflector arrays and how their edge effects contribute to reflector performance. The analysis was carried out using PO & PTD and MoM techniques. In the first part general differences between these computational techniques are highlighted as well as basic edge effects and possible improvements on an imaginary reflector array. In the second part a more in depth analysis of the STEAMR focal plane array is presented.

Freitag, 21.10.2011

Energetic Particle Precipitation Effects in the Stratosphere and Mesosphere

Zeit: 10:15 Uhr
Hörsaal: A97
Dr. Dan Marsh
Atmospheric Chemistry Division, National Center for Atmospheric Research
Boulder, USA

In the declining phase of solar cycle 23, ionization from energetic particle precipitation (EPP) in the polar regions during several large solar proton events resulted significant increases in the concentration of odd nitrogen (N, NOx, NO, NO2). This direct EPP NOx led to large changes in mesospheric and stratospheric ozone that were observed by several satellite instruments. In addition, there is observational evidence that NOx produced in the upper mesosphere and thermosphere, primarily by electron precipitation, can be transported downward at the poles to the stratosphere during wintertime. The magnitude of the indirect NOx source in the northern hemisphere appears to be significantly affected by the occurrence of a major stratospheric sudden warming (SSW).  In this study, NCAR's Whole Atmosphere Community Climate Model (WACCM) is used to examine the chemical response of the middle atmosphere to both direct and indirect EPP NOx. All simulations are constrained to reanalysis data in troposphere and stratosphere to best reproduce the transport of NOx. Comparisons will be made between the 2003 "Halloween" solar proton event, the major SSW that occurred early in 2006 and a year without a significant SPE or SSW, in order to quantify the relative effectiveness of indirect versus direct NOx production.

Freitag, 11.11.2011

Countering asymmetric threats in the maritime environment

Zeit: 10:15 Uhr
Hörsaal: A97
Joachim Kimpel
Bundesamt für Wehrtechnik und Beschaffung
Koblenz, Germany

Since the protection of entrusted objects is one of the tasks to be fulfilled in a stabilization scenario, it is essential to use remote units and, if necessary, UAVs to expand one's own surveillance, protection and effective range. Even though, in an asymmetric conflict, the opponent does not usually respect any legal or political rules, he cannot override the laws of physics. This circumstance allows a systematic analysis of movement patterns and constructional particularities. This may yield information that permits identification of the threat.

To defeat this threat, it is imperative to "come to know" the opponent, to understand his tactics and to create the technological prerequisites that permit the prevention of or successful defense against attacks.

The tasks of command and weapons control systems include input data processing, intelligent sensor data fusion and subsystem management at sensor and weapon level. Input data are all data acquired by on-board sensors, like radar, IR (SWIR and LWIR) and Sonar, or by remote sensor carriers, external data from other units, reconnaissance data from intelligence services and information from civilian bodies, such as air traffic control and shipping authorities. All this information contributes to the generation of an overall situation picture. The situation display – broken down into individual range groups – depends on the threat scenario.

Freitag, 18.11.2011

Calibration of the Herschel HIFI Heterodyne spectrometer using a gas absorption cell

Zeit: 10:15 Uhr
Hörsaal: A97
Dr. Ronan Higgins
Physikalisches Institut
Universität zu Köln

HIFI is a heterodyne spectrometer on board the Herschel space observatory. HIFI covers 2 frequency ranges from 480-1250 and 1410-1910 GHz using a combination of SIS and HEB mixer technology. Using Heterodyne techniques the HIFI (Heterodyne Instrument for the Far-Infrared) spectrometer takes very high resolution spectra of stellar regions of diverse chemistry. In order to maximize the scientific return of this instrument an extensive ground test campaign was undertaken prior to launch in 2009. One key component of this test campaign was the use of a gas absorption cell. By observing well understood gases (12CO, 13CO, H2O, CH3CN, CH3OH) with HIFI the instrument response could be estimated. In addition to measuring the instrument response, the gas cell spectra provided a useful playground for developing the data processing pipeline and analysis tools for the astronomical data. In this seminar the design and operation of the gas cell is described. The analysis routine and results are presented. In addition some lessons learned for future gas cell calibration campaigns of heterodyne instruments are detailed.

Freitag, 25.11.2011

Global Navigation Satellite System (GNSS) meteorology in Southeast Europe

Zeit: 10:15 Uhr
Hörsaal: A97
Dr. Guergana Guerova
Department of Meteorology and Geophysics
Sofia University
Sofia, Bulgaria

The Global Navigation Satellite Systems (GNSS), a new technology that revolutionised the navigation, is becoming an indispensable part of our daily life with millions of chips installed in portable car navigation devices and mobile phones. Beside the numerous civilian and commercial applications GNSS proved to be an accurate atmospheric sensor of the most abundant greenhouse gas namely atmospheric water vapour. Application of GNSS in Meteorology is a well established research field in Europe and GNSS data from 1,600 stations are available for model validation and assimilation in the state-of-art models used for operational weather prediction by the National Meteorologic Services. Advances in GNSS data processing is making possible to also use the GNSS data for climatic trend analysis, an emerging new area of research both attractive and important.

The first results from application of GNSS for Meteorology and Climatic studies in Bulgaria/Southeast Europe will be shown. In particular, the temperature-water vapour-precipitation feedback during the 2003 and 2007 heat waves in Switzerland and Bulgaria will be discussed.

Freitag, 02.12.2011

Impact of energetic particles from solar or geomagnetic storms onto the chemical composition and dynamics of the middle atmosphere

Zeit: 10:15 Uhr
Hörsaal: A97
Dr. Miriam Sinnhuber
Helmholtz Young Investigators Group Leader
Karlsruhe Institute of Technology (KIT)
Institute for Meteorology and Climate Research
Eggenstein-Leopoldshafen, Germany

Energetic particles - protons and electrons from the solar wind, solar eruptions and the terrestrial radiation belts - can precipitate into the middle atmosphere in polar regions. Precipitating energetic particles will excite, dissociate, or ionise the most abundant species in the middle atmosphere, initiating a chain of fast reactions which will significantly change the chemical composition of the middle atmosphere. We investigate the impact of energetic particle precipitation onto the composition of the middle atmosphere and its coupling to the atmosphere below using a combination of atmospheric models of different complexity with observations from the ENVISAT instruments MIPAS and SCIAMACHY.

Freitag, 09.12.2011

Orographically-induced convective precipitation - measurement strategy and results of the COPS campaign

Zeit: 10:15 Uhr
Hörsaal: A97
Dr. Andreas Behrendt
Institute of Physics and Meteorology, COPS Project, Universität Hohenheim
Stuttgart, Germany

The Convective and Orographically-induced Precipitation Study (COPS) was a Research and Development Project of the World Weather Research Programme carried out in summer 2007 in an area covering the Vosges mountains, the Rhine Valley, and the Black Forest mountains. The goal of COPS is to advance the quality of forecasts of orographically-induced convective precipitation by 4-dimensional observations and modelling of its life cycle. The pre-convective environment, the formation of clouds and the onset and development of precipitation were observed with a suite of ground-based and airborne instruments. An overview of the measurement strategy of COPS, a summary of the results gained so far from COPS, and a discussion of open questions will be given. University of Hohenheim operated two new scanning lidar instruments during COPS. A water vapor differential absorption lidar (DIAL) and a rotational Raman lidar (RRL) for temperature measurements. Technical details of these two instruments will be presented and their measurements will be discussed.

Freitag, 16.12.2011

Icethrow simulations at wind turbines

Zeit: 10:15 Uhr
Hörsaal: A97
Dr. Stefan Müller
Meteotest, Bern

Icing is an important issue when operating wind turbines in high altitude or arctic areas as it can cause not only significant production losses but also it represent a safety risk due to falling ice. Ice is accreated at the rotor blades and later on ice is released off the blades and falls down to Earth, which is a risk for people, animals or buildings. There exists single observations of ice several 100m away from turbines. In Switzerland wind turbines are mainly located or projected in the Jura or in the Alps where we also find winter walkways, ski slopes or cross country skiing runs nearby. Thus there is a need for risk studies already in the planing phase. In 2006-2008 METEOTEST has acquired a dataset of ice particles at the Wind turbine at the Gütsch (UR) 2300m above sea level. This is a worldwide unique systematical measurement of icethrow. In the following a model was developed to simulate the risk of icethrow. Results of the icethrow study and a comparison to the simulations will be presented.