This thesis is devoted to the experimental quantitative characterization of the shape and orientation distribution of ice particles in clouds. The characterization is based on measured and modeled elevation dependencies of the polarimetric parameters differential reflectivity and correlation coefficient. The polarimetric data is obtained using a newly developed 35-GHz cloud radar MIRA-35 with hybrid polarimetric configuration and scanning capabilities. The full procedure chain of the technical implementation and the realization of the setup of the hybrid-mode cloud radar for the shape determination are presented. This includes the description of phase adjustments in the transmitting paths, the introduction of the general data processing scheme, correction of the data for the differences of amplifications and electrical path lengths in the transmitting and receiving channels, the rotation of the polarization basis by 45°, the correction of antenna effects on polarimetric measurements, the determination of spectral polarimetric variables, and the formulation of a scheme to increase the signal-to-noise ratio. Modeling of the polarimetric variables is based on existing backscattering models assuming the spheroidal representation of cloud scatterers. The parameters retrieved from the model are polarizability ratio and degree of orientation, which can be assigned to certain particle orientations and shapes. In the thesis the first quantitative estimations of ice particle shape at the top of liquid-topped clouds are presented. Analyzed ice particles were formed in the presence of supercooled water and in the temperature range from -20 °C to -3 °C. The estimation is based on polarizability ratios of ice particles measured by the MIRA-35 with hybrid polarimetric configuration, manufactured by METEK GmbH. For the study, 22 cases observed during the ACCEPT (Analysis of the Composition of Clouds with Extended Polarization Techniques) field campaign were used. Polarizability ratios retrieved for cloud layers with cloud-top temperatures of about -5, -8, -15, and -20 °C were 1.6, 0.9, 0.6, and 0.9, respectively. Such values correspond to prolate, quasi-isotropic, oblate, and quasi-isotropic particles, respectively. Data from a free-fall chamber were used for the comparison. A good agreement of detected shapes with well-known shape{temperature dependencies observed in laboratories was found.

The ITG section 7.5 "Wellenausbreitung" within the VDE (German Association for Electrical, Electronic & Information Technologies) organised a conference on Wave Propagation in Communication, Microwave Systems and Navigation which was held during 25th - 27th of November 2009 in Chemnitz, Germany. The conference philosophy is to emphasize the commonalty between propagation aspects of microwave remote sensing sensors and microwave systems at large. The following topics of Remote Sensing, Communication and Navigation are eligible for presentation: Microwave Propagation in Communication and Microwave Sensors - Satellite Communications - Multi-Path Propagation - Indoor Propagation - Digital Broadcast Planning - MIMO Systems and Reuse - Ionospheric Propagation - Urban Communication - Microwave Measurements in Propagation Applications of Microwave Sensors - Radar Polarimetry - Bistatic and Multistatic Radar - Polarimetric and Multistatic Interferometry - Multi-Parameter Weather Radar Systems - Automotive and Airborne Radars - System Calibration - Biological Effects of EM-Radiation - Wave Modulation Remote Sensing Radars Antenna Design and Measurements / Im Rahmen der Aktivitäten des ITG-Fachausschusses 7.5 "Wellenausbreitung" im VDE wurde eine Fachtagung auf dem Gebiet Wellenausbreitung bei Funk-, Mikrowellensystemen und Navigation vom 25. - 27. November 2009 in Chemnitz abgehalten. Die Tagungsphilosophie betont den gemeinsamen Nenner der Wellenausbreitung in diversen Bereichen wie Mikrowellensensorik und Mikrowellensystemen. Dem Leitthema zugeordnet, werden die folgenden Themen aus Fernerkundung, Kommunikation und Navigation besonders berücksichtigt. Mikrowellenausbreitung in der Kommunikation und Mikrowellensensorik - Satellitenkommunikation - Mehrwegeausbreitung - Innen-Gebäude-Übertragung - Frequenzplanung für den digitalen Rundfunk - MIMO Systeme - Wellenausbreitung in der Ionosphäre - urbane Kommunikation - Mikrowellenmessungen der Wellenausbreitung Nutzung und Anwendung in der Mikrowellensensorik - Radar-Polarimetrie - Bistatische und Multistatische Radarverfahren - Polarimetrische und Multistatische Interferometrie - Multiparameter-Wetterradar-Verfahren - Automobil- und Flugzeugradar - Systemkalibrierung - Biologische Effekte der EM-Strahlung - Antennenentwicklung und -messungen für wellenmodulierte Fernerkundungsradare

The aim of this thesis is to determine to what extent aircraft-borne radar remote sensing can be used as the sole method for making recordings of the surface of the earth as a basis for compiling topographical and relief maps of mountainous areas. This is done using three test areas: the Edelsberg area in the Allgäu Alps and the Silvretta and Verwall Groups in the Central Alps. The basis for discussion is provided by examination of the interaction between the objects to be imaged and the radar signal, the sensor-specific characteristics thereby being taken into account. Following this some data processing and conditioning methods used for extracting information on the relief and surface coverage for preparation of cartographical products are presented. Analysis of the quality of the results shows that, measured against the requirements of mountain cartography, radar remote sensing is a practical and useful tool for making maps in Alpine regions. As the sole source of information, however, aircraft-borne radar remote sensing p roves to date to be inadequate for cartographical applications in high-mountain regions. / Ziel der vorliegenden Arbeit ist, festzustellen, inwieweit die flugzeuggetragene Radarfernerkundung als alleinige Erfassungsmethode der Erdoberfläche zur Erstellung von topographischen und reliefbeschreibenden Karten in Gebirgslandschaften dienen kann. Dies wird anhand von drei Testgebieten, dem Edelsberggebiet in den Allgäuer Alpen sowie der Silvretta- und Verwallgrupe in den Zentralalpen, untersucht. Die Betrachtung der Interaktion zwischen den abzubildenden Objekten und dem Radar-Signal unter Berücksichtigung der sensorspezifischen Charakteristika bildet dabei die Diskussionsgrundlage. Im weiteren werden Methoden zur Datenprozessierung und -aufbereitung vorgestellt, die eine Informa-tionsextraktion bezüglich des Reliefs und der Oberflächenbedeckung für die Erstellung kartographischer Produkte ermöglichen. Die Qualitätsanalyse der Ergebnisse zeigt, dass die Radarfernerkundung, gemessen an den Anforderungen der Gebirgskartographie, ein sinnvolles und nutzbringendes Werkzeug für die Kartenerstellung in alpinen Regionen ist. Für kartographische Anwendungen in Hochgebirgsregionen erweist sich die flugzeuggetragene Radarfernerkundung als einzige Informationsquelle bislang allerdings als nicht ausreichend.

This thesis is devoted to the experimental quantitative characterization of the shape and orientation distribution of ice particles in clouds. The characterization is based on measured and modeled elevation dependencies of the polarimetric parameters differential reflectivity and correlation coefficient. The polarimetric data is obtained using a newly developed 35-GHz cloud radar MIRA-35 with hybrid polarimetric configuration and scanning capabilities. The full procedure chain of the technical implementation and the realization of the setup of the hybrid-mode cloud radar for the shape determination are presented. This includes the description of phase adjustments in the transmitting paths, the introduction of the general data processing scheme, correction of the data for the differences of amplifications and electrical path lengths in the transmitting and receiving channels, the rotation of the polarization basis by 45°, the correction of antenna effects on polarimetric measurements, the determination of spectral polarimetric variables, and the formulation of a scheme to increase the signal-to-noise ratio. Modeling of the polarimetric variables is based on existing backscattering models assuming the spheroidal representation of cloud scatterers. The parameters retrieved from the model are polarizability ratio and degree of orientation, which can be assigned to certain particle orientations and shapes. In the thesis the first quantitative estimations of ice particle shape at the top of liquid-topped clouds are presented. Analyzed ice particles were formed in the presence of supercooled water and in the temperature range from -20 °C to -3 °C. The estimation is based on polarizability ratios of ice particles measured by the MIRA-35 with hybrid polarimetric configuration, manufactured by METEK GmbH. For the study, 22 cases observed during the ACCEPT (Analysis of the Composition of Clouds with Extended Polarization Techniques) field campaign were used. Polarizability ratios retrieved for cloud layers with cloud-top temperatures of about -5, -8, -15, and -20 °C were 1.6, 0.9, 0.6, and 0.9, respectively. Such values correspond to prolate, quasi-isotropic, oblate, and quasi-isotropic particles, respectively. Data from a free-fall chamber were used for the comparison. A good agreement of detected shapes with well-known shape{temperature dependencies observed in laboratories was found.:1 Introduction 2 Formation and development of ice particles: Laboratory studies and remote observations 2.1 Heterogeneous ice formation in the atmosphere 2.2 Laboratory investigations of ice crystal development 2.3 Polarimetric radar observations of ice microphysics 2.3.1 Polarimetry in weather radar networks 2.3.2 Polarimetry in cloud radars 2.3.3 Polarization coupling 2.4 Aims and scientific questions 3 Effects of antenna patterns on cloud radar polarimetric measurements 3.1 Measurements of complex antenna patterns 3.1.1 Problem definition 3.1.2 Measurement description 3.1.3 Results of antenna pattern measurements 3.2 Correction of LDR measurements 3.3 Discrimination between insects and clouds 4 Cloud radar MIRA-35 with hybrid mode 4.1 Implementation and phase adjustment 4.2 Processing of the coherency matrix 4.3 Correction of the coherency matrix for differences of channels 4.4 The coherency matrix in the slanted basis 4.5 Correction for the antenna coupling 4.6 Spectral polarimetric variables 4.7 Sensitivity issue 5 Shape and orientation retrieval 5.1 Backscattering model 5.2 Retrieval technique 5.3 Case study 6 Shape-temperature relationship of pristine ice crystals 6.1 Instrumentation and data set 6.2 Examples of the shape retrieval 6.2.1 Case 1: 12 October 2014, 15:00-16:00 UTC 6.2.2 Case 2: 18 October 2014, 01:00-02:00 UTC 6.2.3 Case 3: 20 October 2014, 18:00-19:00 UTC 6.2.4 Case 4: 10 November 2014, 02:00-03:00 UTC 6.2.5 Case 5: 7 November 2014, 20:00-21:00 UTC 6.3 Comparison of shape with laboratory studies 6.4 Orientation of pristine ice crystals 7 Summary and outlook Bibliography List of Abbreviations List of Symbols