Der Wasserdampfgehalt der Atmosphäre gehört zu den Hauptkontrolleuren des Treibhauseffektes und spielt eine Schlüsselrolle im globalen Energiekreislauf, wobei den Polargebieten als globale Wärmesenken eine besondere Bedeutung zukommt. Im Rahmen dieser Arbeit wurde aus Messungen des Global Positioning System (GPS) der integrierte Wasserdampfgehalt innerhalb der letzten Dekade bestimmt und analysiert. Die Untersuchungen stützen sich auf die Reprozessierung eines aus 195 Stationen bestehenden globalen GPS-Netzes. Die aus den geschätzten GPS-Troposphärenparameter bestimmten Wasserdampf- zeitreihen wurden hinsichtlich Genauigkeit und Homogenität untersucht. Nach Korrektion der Inhomogenit äten ist es möglich, mit GPS mehrjährige Schwankungen im potenziellen Niederschlagswasser mit einer Genauigkeit besser als 0,3 mm Höhe der Wassersäule zu erfassen. Als Ergebnis der Untersuchungen zeigen sich in Europa und großen Teilen Nordamerikas Anomalien des Wasserdampfgehaltes im Bereich eines Millimeters, welche sich vor allem auf thermodynamische Effekte zurückführen lassen. In den Tropen und im Südosten der USA können die Wasserdampfanomalien 3 bis 5 mm betragen. Sie sind durch dynamische Prozesse bedingt, die mit der Südlichen Oszillation im Zusammenhang stehen. Eine Anwendung der aus GPS-Beobachtungen bestimmten Wasserdampfzeitreihen ist die Validierung des Wasserdampfes im globalen Wettervorhersagemodell des National Center for Environmental Predicton (NCEP). Über Europa und großen Teilen Nordamerikas reproduziert NCEP die Schwankungen des Wasserdampfgehaltes sehr gut und stellt damit eine gute Datengrundlage für ?ächendeckende Untersuchungen langfristiger Veränderungen im Wasserdampfgehalt dar. In der Antarktis und den Tropen wird jedoch das saisonale und mehrjährige Signal des Wasserdampfes von NCEP um 25% bis 40% unterschätzt. Als zweite Anwendung der GPS-Wasserdampfzeitreihen erfolgt die Validierung satellitenbasierter Radiometermessungen über der Antarktis. Sie zeigt eine gute Übereinstimmung der Wasserdampfwerte aus GPSund Radiometermessungen. Die im Rahmen dieser Arbeit aus GPS-Beobachtungen bestimmten Wasserdampfzeitreihen bilden eine sehr gute Datengrundlage für weitergehende Untersuchungen der Wetter- und Klimaforschung. / The atmospheric water vapour is one of the main variables controlling the greenhouse effect and it plays a crucial role in the global energy cycle. In this context the polar regions which act as global heat sinks are especially important. This study uses observations from the Global Positioning System (GPS) to investigate changes of the integrated atmospheric water vapour. It is based on a reprocessing of a global GPS network consisting of 195 stations. A strong emphasis was placed on the investigation of the accuracy and the homogeneity of the GPS derived water vapour time series. After correcting the inhomogeneities interannual ?uctuations in the precipitable water can be determined from GPS data with an accuracy of 0.3 mm in water column height. As a result, the interannual variations in the water vapour content are in the order of one millimetre over Europe and over large areas of North America. They are mainly related to thermodynamic effects. In the tropics and in the south east of the USA water vapour anomalies can reach 3 to 5 mm caused by dynamic processes connected to the Southern Oscillation. As one application of the estimated GPS water vapour time series a validation of water vapour from the global numerical weather prediction model of the National Center for Environmental Prediction (NCEP) was carried out. Over Europe and large parts of North America the seasonal signal and the interannual variations of the water vapour are very well reproduced by NCEP. Hence, in these regions NCEP presents a good database for area-wide investigations of long-term changes in the water vapour content. However, in Antarctica and in the Tropics the seasonal and also the interannual signals of the NCEP water vapour are strongly underestimated by 25% to 40%. A second application of the estimated GPS water vapour time series is the validation of satellite-based radiometer measurements over Antarctica. A good agreement was found between the water vapour derived from GPS and radiometer data. The water vapour time series estimated in this study provide a good basis for further weather and climate related investigations.

It is the future of the stratospheric ozone layer, which protects life at Earth’s surface from harmful ultraviolet (UV) radiation, that is the focus of the present work. Fundamental changes in the composition and structure of the stratosphere in response to anthropogenic climate forcing may lead to catastrophic ozone loss under current, and even reduced, stratospheric halogen loading. In particular, the evolution toward a colder, wetter stratosphere, threatens to enhance the heterogeneous conversion of inorganic halogen from its reservoir species to its catalytically active forms, and thus promote in situ ozone loss. Water vapor concentrations control the availability of reactive surface area, which facilitates heterogeneous chemistry. Furthermore, the rates of the key heterogeneous processes are tightly controlled by the ambient humidity. Thus, credible predictions of UV dosage require a quantitative understanding of both the sensitivity of these chemical mechanisms to water vapor concentrations, and an elucidation of the processes controlling stratospheric water vapor concentrations. Toward this end, we present a set of four case studies utilizing high resolution in situ data acquired aboard NASA aircraft during upper atmospheric research missions over the past two decades. 1) We examine the broad scale humidity structure of the upper troposphere and lower stratosphere from the midlatitudes to the tropics, focusing on cirrus formation and dehydration at the cold-point tropical tropopause. The data show evidence for frequent supersaturation in clear air, and sustained supersaturation in the presence of cirrus. These results challenge the strict thermal control of the tropical tropopause. 2) We investigate the likelihood of cirrus-initiated activation of chlorine in the midlatitude lower stratosphere. At midlatitudes the transition from conditions near saturation below the local tropopause to undersaturated air above greatly reduces the probability of heterogeneous activation and in situ ozone loss in this region. 3) We probe the details of heterogeneous processing in the wintertime Arctic vortex, and find that in situ measurements of OH provide incontrovertible evidence for the heterogeneous reaction of HOCl with HCl. This reaction is critical to sustaining catalytically active chlorine and prolonging ozone loss in the springtime vortex. 4) We revisit the topic of midlatitude ozone loss with an emphasis upon the response of ozone in this region to changes in the chemical composition and thermal structure of the lower stratosphere induced by anthropogenic climate change. Specifically, we show evidence for episodic moisture plumes in the overworld stratosphere generated by the rapid evaporation of ice injected into this region by deep convection, and find that these high water vapor plumes have the potential to alter the humidity of the lower stratosphere, and drastically increase the rate of heterogeneous chemistry and in situ ozone loss, given sufficient reactive surface. / Earth and Planetary Sciences

Stratospheric water vapor plays an important role in the Earth system, both through its role in stratospheric ozone destruction and as a greenhouse gas contributing to radiative forcing of the climate. Highly accurate water vapor measurements are critical to understanding how stratospheric water vapor concentrations will respond to a changing climate. However, the past disagreement among water vapor instruments on the order of 1 – 2 ppmv hinders understanding of the mechanisms which control stratospheric humidity, and the reliable detection of water vapor trends. In response to these issues, we present a new dual axis water vapor instrument that combines the heritage Harvard Lyman-\(\alpha\) hygrometer with the newly developed Harvard Herriott Hygrometer (HHH). The Lyman-\(\alpha\) instrument utilizes ultraviolet photo-fragment fluorescence detection, and its accuracy has been demonstrated though rigorous laboratory calibrations and in situ diagnostic procedures. HHH employs a tunable diode near-IR laser to measure water vapor via direct absorption in a Herriott cell; it demonstrated in-flight precision of 0.1 ppmv (1-sec) with accuracy of 5%±0.5 ppmv. We describe these two measurement techniques in detail along with our methodology for calibration and details of the measurement uncertainties. We also examine the recent flight comparison of the two instruments with several other in situ hygrometers during the 2011 MACPEX campaign, in which five independent instruments agreed to within 0.7 ppmv, a significant improvement over past comparisons. Water vapor measurements in combination with simultaneous in situ measurements of \(O_3\), CO, \(CO_2\), HDO, and HCl are also used to investigate transport in the Tropical Tropopause Layer (TTL). Data from the winter 2006 CR-AVE campaign and the summer 2007 TC4 campaign are analyzed in a one-dimensional mixing model to explore the seasonal importance of transport within the TTL via slow upward ascent, convective injection, and isentropic transport from the midlatitude stratosphere. The model shows transport from midlatitudes to be significant in summer and winter, affecting ozone concentrations and therefore the radiative balance of the TTL. It also shows significant convective influence up to 420 K potential temperature in both seasons, which appreciably increases the amount of water vapor above the tropopause. / Engineering and Applied Sciences

Existing tunable diode laser absorption spectroscopy (TDLAS) sensors for potassium (K) and for water vapor (H2O) and temperature were combined to enable simultaneous measurements in combustion and gasification processes. In-situ real-time detection of the above mentioned combustion parameters will improve the understanding of ash-formation during thermochemical conversion of biomass. Simultaneous measurements facilitate the experimental procedure and decrease the methodological uncertainty introduced by the heterogeneous nature of the pellets. The K sensor is based on direct absorption spectroscopy (DAS), whereas the H2O system employs wavelength modulation spectroscopy (WMS) together with two-line thermometry for temperature assessment. Two methods for combining the laser beams were evaluated, the first involving dichroic elements, the second using available fiber optic combiners. The latter method was considered advantageous. An existing LabVIEW program was modified to allow for simultaneous signal generation and data acquisition for both sensors. The sensors were then tested separately in a low pressure K cell and in ambient air. The combined sensor was applied to simultaneous measurements above various pelletized biofuels during combustion in a single pellet reactor (SPR). Significant difference in absolute concentration and time histories were observed between fuels, in particular for K and temperature. Significant K concentrations were only observed during the devolatilization phase. The combined sensor will be useful in fundamental combustion research.

The performance of astronomical interferometer arrays operating at (sub) millimeter wave-lengths is seriously compromised by rapid variations of atmospheric water vapour content that distort the phase coherence of incoming celestial signals. Unless corrected, these phase distortions, which vary rapidly with time and from antenna to antenna, seriously compromise the sensitivity and image quality of these arrays. Building on the success of a prototype infrared radiometer for millimeter astronomy (IRMA I), which was ued to measure atmospheric water vapour column abundance, this thesis presents results from a second generation radiometer (IRMA II) operating at the James Clerk Maxwell Telescope (JCMT) on Mauna Kea, Hawaii from December, 2000 to March, 2001. These results include comparisons with other measures of water vapour abundance available on the summit of Mauna Kea and a comparison with a theorteical curve-of-growth calculated from a new radiative transfer model, ULTRAM, developed specifically for the purpose. Plans for a third generation radiometer (IRMA III) are also be discussed. / xii, 143 leaves : ill. ; 28 cm.

Biodegradable edible films are both economically and environmentally important to the food industry as packaging and coating materials, as the industry seeks to find a replacement to traditional petroleum-derived synthetic polymers. The overall goal of this thesis was to design a canola protein isolate (CPI)-based biodegradable and edible film that provides excellent mechanical, optical and water vapor barrier properties. A better understanding of the potential of CPI for use as a film-forming ingredient could lead to enhanced utilization and value of the protein for food and non-food applications. In study one, the mechanical, optical and water vapor barrier properties of CPI-based films were investigated as a function of protein (5.0% and 7.5% w/w) and glycerol (30%, 35%, 40%, 45%, and 50% w/w of CPI) concentrations. Overall, as the glycerol concentration increased for the 5.0% and 7.5% CPI-based films, mechanical strength and flexibility decreased and increased, respectively. Film strength was also found to increase at the higher protein concentration; however corresponding changes to film flexibility differed depending on the testing method used. For instance, puncture deformation testing indicated that film flexibility was reduced as the CPI concentration was raised, whereas tensile elongation testing indicated no change in extensibility between the two CPI concentrations. Film transparency was found to increase with increasing levels of glycerol and decreasing levels of CPI, whereas water vapor permeability was found to increase with increasing levels of both glycerol and protein. In study two, mechanical, optical and vapor barrier properties of CPI-based films were evaluated as a function of plasticizer-type (50% (w/w of CPI), glycerol, sorbitol, polyethylene glycol 400 (PEG-400)) and fixative condition (0% and 1% (w/w of CPI), genipin). CPI films prepared with sorbitol were significantly stronger than films with PEG-400, followed by films with glycerol, whereas the flexibility of CPI-based films with glycerol was higher than films with PEG-400, followed by films with sorbitol. In all cases, films prepared with genipin were stronger and less malleable than un-cross linked films. CPI films with glycerol were more transparent than films with sorbitol, followed by films with PEG-400, and the addition of genipin significantly increased the opacity of CPI films. CPI films prepared with glycerol also showed poorer water vapor barrier property than films with PEG-400, followed by films with sorbitol, however, no differences were observed in the presence and absence of genipin. In summary, as the plasticizer concentration increased or protein concentration decreased, CPI films became weaker, more flexible and clearer; however their water vapor barrier properties became poorer as both plasticizer and protein concentration increased. Moreover, CPI films with sorbitol and genipin were found to be stronger, less malleable and permeable to moisture than CPI films with or without genipin, and in the presence of glycerol or PEG-400. Overall, CPI could be considered as a potential material for the development of biodegradable edible packaging in the future.

This thesis examines the link between airborne flux estimates of CO$ sb2$, sensible heat, and water vapor, and surface parameters retrieved by remote sensing. Chapter 1 analyses the relationship between surface temperature and vegetation indices, obtained from the Advanced Very High Resolution Radiometer on board of NOAA-9 and -10 satellites, and fluxes of sensible heat, latent heat, and CO$ sb2$, estimated from aircraft. Linear relationships between CO$ sb2$ and the Normalized Difference Vegetation Index (NDVI) or the Simple Ratio vegetation index (SR) are found on a daily basis, but a highly nonlinear relationship appears for the seasonal variation. Latent Heat fluxes showed the poorest correlations with surface parameters. A seasonal linear relationship appeared between sensible heat and NDVI. Local extreme flux values due to the intermittency of boundary layer dynamics largely contribute to lower the correlations; such variations are the reason for the difficulties in relating fluxes obtained from single overpasses and over short distances to fixed points at the surface. This problem is further examined in Chapter 2, in which conditional sampling of airborne flux estimates is used to characterize the turbulent structures that are carrying flux, and their link to the surface. The analysis confirms that few extreme events may carry a significant fraction of the flux. Missing or hitting one of these structures may translate into very large oscillations on the flux estimate that are often not directly coupled to surface characteristics. A much clearer surface 'signature' emerges when measurements are taken within the surface layer, since the reorganization of turbulent structures that takes place with increasing height will result in a merging of the signature that came from different sources at the surface. This helps to explain some of the poor correlations obtained in Chapter 1 and reinforces the need for a better understanding of the distributions of these tu

Three studies of precipitable water using the Global Positioning System are presented. The first study finds that precipitable water in Hawaiʻi is best described by a lognormal distribution. The long-term average value of precipitable water declines exponentially with height, but the dispersion of precipitable water declines more linearly. The change in skewness of the distributions is also linear, although in this case it increases with elevation. The second and third studies use GPS meteorology to investigate a climatological and a meteorological event respectively. First, the effect of the 1997-1998 El Nino on precipitable water in the western tropical Pacific is studied and found to be consistent with a model relating the formation of an anomalous high-pressure ridge to the El Nino episode. Finally, the details of the precipitable water field for the Kaʻu Storm, November 2000 are examined. The results highlight the role of topography in controlling the location of convection, The observed correlation between the precipitable water and rainfall is used to generate estimates of rainfall based on GPS data, Comparing the GPS precipitable water estimates with those from a weather model indicates that the underestimates of rainfall produced by the weather model are probably due to correlated underestimates of precipitable water. / Thesis (Ph. D.)--University of Hawaii at Manoa, 2002. / Mode of access: World Wide Web. / Includes bibliographical references (leaves 62-66). / Electronic reproduction. / Also available by subscription via World Wide Web / ix, 66 leaves, bound ill. 29 cm

Thesis (Ph.D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Dr. Paul G. Steffes; Committee Member: Dr. Gregory D. Durgin; Committee Member: Dr. Robert D. Braun; Committee Member: Dr. Thomas K. Gaylord; Committee Member: Dr. Waymond R. Scott

Thesis (Ph. D.)--University of California, San Diego, 2000. / Vita. Includes bibliographical references.