Probing the Atmospheric Boundary Layer Using Remotely Piloted Aircraft With Special Regard to the Morning Transition and Wind Energy Research

The thesis at hand is a work in the field of atmospheric physics. It deals with the experimental study of physical processes in the so-called atmospheric boundary layer. The atmospheric boundary layer is the lowest part of the earth’s atmosphere, which is in direct contact with the earth surface. It is important to have considerable knowledge about the processes in the boundary layer to understand the concepts of weather and climate. Two scientific problems have been addressed in this dissertation. An experimental study of the morning transition of the atmospheric boundary layer was conducted to assess the applicability of a theoretical model of the convective boundary layer at all times during the transition period. Limited evidence was found for such a uniform description based on the used parameters. It has been found that the entrainment layer is far from homogeneous, and single events of entrainment and convection have a strong influence on the local boundary layer’s thermal stratification. A further experiment was conducted within striking distance of wind-energy converters (WEC). In-situ measurements of meteorological quantities were taken in the wake of a WEC to quantify its extension and intensity. The measuring instrument described and used in this thesis is a small unmanned aircraft. Aircraft of this kind are frequently used in all types of civil applications and are of great benefit for airborne meteorology in particular. A significant part of this thesis describes the development of sensors for the unmanned aircraft MASC, developed at the University of Tübingen, and their test and first measurement results. Two fast, lightweight temperature sensors of different types were developed and validated against established instrumentation at the Richard-Aßmann-Observatory of the German Meteorological Service in Lindenberg. The common method of measuring the airflow vector with multi-hole probes was scrutinised with regard to its applicability in turbulence measurement and optimized for integration into the MASC system. It was made possible to resolve small-scale turbulent motions of temperature and wind in the sub-meter range through this measures. Important improvements could also be accomplished in the field of water vapour measurement. With the help of a dynamic model of a capacitive humidity sensor, it was possible to reconstruct fast changes in humidity from the originally slow sensor readings.Die vorliegende Arbeit behandelt die experimentelle Untersuchung physikalischer Vorgänge in der sogenannten atmosphärischen Grenzschicht. Die atmosphärische Grenzschicht ist die unterste Schicht der Atmosphäre, welche sich in direktem Kontakt zur Erdoberfläche befindet. Eine genaue Kenntnis der hier vorherrschenden physikalischen Prozesse ist von entscheidender Bedeutung für das Verständnis von Wetter und Klima. Zwei unterschiedliche wissenschaftliche Fragestellungen werden in dieser Arbeit thematisiert. Eine experimentelle Untersuchung der morgendlichen Transition der atmosphärischen Grenzschicht wurde durchgeführt, um die Anwendbarkeit eines theoretischen Modells der konvektiven Grenzschicht auf jeden Zeitpunkt während der Transition, zu überprüfen. Es wurden eingeschränkt Hinweise gefunden, dass eine solche einheitliche Beschreibung, basierend auf den zur Hilfe genommenen Parametern, möglich ist. Es konnte gezeigte werden, dass die Entrainment-Zone starke horizontale Unebenheiten aufweist, und einzelne Entrainment- und Konvektionsereignisse starken Einfluss auf die lokale thermische Schichtung der Grenzschicht haben. Ein weiteres Experiment fand in unmittelbarer Nähe von Windenergieanlagen statt. Meteorologische In-situ-Messungen in den Wirbelschleppen der Anlagen wurden durchgeführt um deren Ausdehnung und Intensität zu quantifizieren. Das Messinstrument, welches zur Gewinnung der Daten in dieser Arbeit genutzt wird, ist ein unbemanntes Kleinflugzeug. Solche Flugzeuge halten zunehmend Einzug in zivile Anwendungen und sind ein großer Gewinn für die fluggestützte Meteorologie. Weite Teile dieser Arbeit beschreiben die Entwicklung von Messinstrumenten für einen solchen Sensorträger, deren Erprobung und erste Messergebnisse. Zwei verschiedene, schnelle und leichte Temperatursensoren wurden entwickelt und gegen bewährte Instrumente validiert. Die verbreitete Methode zur Messung des Strömungsvektors mit Mehrlochsonden, wurde für die Anwendung zur Turbulenzmessung in Flugzeugen kritisch hinterfragt und optimiert. Mit Hilfe dieser Maßnahmen konnte erreicht werden, dass kleinskalige turbulente Schwankungen von Temperatur und Wind im Submeterbereich, im Flug aufgelöst werden können. Entscheidende Verbesserungen konnten auch im Bereich der Luftfeuchtemessung erreicht werden. Durch Modellierung des verwendeten kapazitiven Sensors, wurde die Rekonstruktion schneller Änderungen der Luftfeuchte aus den ursprünglich langsamen Messungen des Sensors ermöglicht

KaSI: a Ka-band and S-band Cross-track Interferometer

A dual-frequency system is needed to better understand natural processes that constitute the environment and seasonal cycles of the Earth. A system working at two different wavelengths acquiring data simultaneously will give a valuable dataset since the conditions on the ground will be exactly the same. Hence, elements such as wind, soil moisture or any other changes on the ground will not interfere in the mea- surements. This thesis explains how an S-band radar was built and tested. Moreover, the experiments done with a Ka-band radar used as a scatterometer are explained as well as the data processing and analysis. Finally, the two systems are used to get dual-frequency measurements from an airborne platform. The dual-frequency data is explored, showing the differences in normalized radar cross-section between frequencies and discussing the interferometric measurements

Index to 1985 NASA Tech Briefs, volume 10, numbers 1-4

Short announcements of new technology derived from the R&D activities of NASA are presented. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This index for 1985 Tech Briefs contains abstracts and four indexes: subject, personal author, originating center, and Tech Brief Number. The following areas are covered: electronic components and circuits, electronic systems, physical sciences, materials, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences

NASA thesaurus. Volume 2: Access vocabulary

The Access Vocabulary, which is essentially a permuted index, provides access to any word or number in authorized postable and nonpostable terms. Additional entries include postable and nonpostable terms, other word entries, and pseudo-multiword terms that are permutations of words that contain words within words. The Access Vocabulary contains 40,738 entries that give increased access to the hierarchies in Volume 1 - Hierarchical Listing

NASA thesaurus. Volume 2: Access vocabulary

The access vocabulary, which is essentially a permuted index, provides access to any word or number in authorized postable and nonpostable terms. Additional entries include postable and nonpostable terms, other word entries and pseudo-multiword terms that are permutations of words that contain words within words. The access vocabulary contains almost 42,000 entries that give increased access to the hierarchies in Volume 1 - Hierarchical Listing

Aeronautical Engineering: A continuing bibliography with indexes (supplement 159)

This bibliography lists 347 reports, articles and other documents introduced into the NASA scientific and technical information system in February 1983

NASA Thesaurus. Volume 2: Access vocabulary

The NASA Thesaurus -- Volume 2, Access Vocabulary -- contains an alphabetical listing of all Thesaurus terms (postable and nonpostable) and permutations of all multiword and pseudo-multiword terms. Also included are Other Words (non-Thesaurus terms) consisting of abbreviations, chemical symbols, etc. The permutations and Other Words provide 'access' to the appropriate postable entries in the Thesaurus