Doppler sodar observations of the winds and structure in the lower atmosphere over Fairbanks, Alaska

Thesis (M.S.) University of Alaska Fairbanks, 2007Fairbanks, Alaska (64°49ʹ N, 147°52ʹ W) experiences strong temperature inversions which when combined with the low wind speeds prevailing during the winter cause serious air pollution problems. The SODAR (Sound Detection And Ranging) or acoustic sounder is a very useful instrument for studying the lower atmosphere as it can continuously and reliably measure the vertical profiles of wind speed and direction,vertical motions, turbulence and the thermal structure in the lower part of the troposphere. A Doppler sodar was operated from December 2005 to April 2006 at the National Weather Service site in Fairbanks. The wind observations from the sodar indicate that the majority of the winds during the winter months were from the North, Northeast or the East, which is in good agreement with the radiosonde measurements and the long term trends in the wind patterns over Fairbanks area. Case studies were carried out using the sodar data depicting drainage winds, low-level jets, formation and breakup of inversions and estimation of the mixing layer height.1. Introduction -- 1.1. Climatic features in Fairbanks during winter -- 1.1.1. Temperature inversions -- 1.1.2. Valley winds and drainage winds -- 1.1.3. Urban heat island -- 1.1.4. Air pollution and ice fog -- 1.2. SODAR and its applications -- 1.2.1 Acoustic sounder observations at Fairbanks in the past -- 2. Theory and instrumentation 2.1. Estimation of Ct² -- 2.1.1. Scattering theory -- 2.1.2. Sodar equation -- 2.2. Wind speed and direction -- 2.3. Sodar installation and data acquisition -- 2..4. Sodar dataset and additional sources of data -- 2.5. Algorithm to detect strong layers of temperature inversion -- 3. Results and discussion -- 3.1. Results from the inversion detection algorithm -- 3.1.1. Diurnal variations in inversion characteristics -- 3.1.2. Effect of cloud cover on inversion characteristics -- 3.2. Wind observations from sodar data -- 3.3. Case studies from sodar observations -- 3.3.1. Drainage winds overflowing the stable layer of air beneath -- 3.3.2. Nocturnal jet associated with a temperature inversion -- 3.3.3. Destruction of an inversion due to forced mixing and increasing cloud cover -- 3.3.4. Estimation of the mixing layer height from the backscatter intensity -- 4. Conclusions and future work -- References

A Note on Gauss-Bonnet Black Holes at Criticality

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Hence it is planned to develop procedures to grow microstructures that can be used in several applications. In the current work, PPy microstructures with high coverage densities are synthesized on various electrode substrates by soft template based electrochemical techniques. Hollow, hemispherical and spherical PPy microstructures are developed by a two step method using electro generated hydrogen bubble templates on SS 304 electrodes. In the first step, Hydrogen bubbles are electro generated and stabilized on the electrode in the presence of β- naphthalene sulfonic acid (β-NSA). In the second step, Pyrrole is oxidised over the bubble template to form PPy microstructures. Microstructures (open and closed cups) of average size 15 μm are uniformly spread on the surface with a coverage density of 2.5×105 units /cm2. 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Similarly microhorn/celia structures are observed with length 10-15 µm. Microcelia are uniformly distributed over the surface with each structure having a diameter of 2 µm at the base to 150 nm at the tip. Growth mechanism based on contact angle of the reactant solution droplets on the substrate is proposed. PPy microstructures are characterized by scanning electron microscopy, X-Ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Raman Spectroscopy and UV-Visible spectroscopy to study morphology, ‘chemical bonding and structure’ , ‘defects and charge carriers’. Applicability of the electrodes with PPy microstructures in supercapacitors is investigated by cyclic voltammetry, chronopotentiometry and electrical impedance spectroscopy. Electrodes developed by all the above methods demonstrated very good supercapacitance properties. Supercapacitor studies revealed very high specific capacitances (580, 915, 728 and 922 F/g,) and specific powers (20, 25, 13.89 and 15.91 kW/kg) for electrodes with PPy microstructures (H2 bubble based two step method, O2 bubble based single step method, HEPES stabilized H2 bubbble method and HEPES based microhorn/celia structures respectively). Supercapacitive behavior of all the electrodes is retained even after an extended charge-discharge cycling in excess of 1500 cycles. Horseradish peroxidase entrapped, bowl shaped PPy microstructures are developed for H2O2 biosensing. Amperometric biosensor has a performance comparable to the sensors reported in the literature with high sensitivity value of 12.8 μA/(cm2.mM) in the range 1.0 mM to 10 mM. Glucose oxidase entrapped PPy amperometric biosensor is developed for Glucose sensing. Sensitivity of 1.29 mA/(cm2.mM) is observed for β-D-Glucose sensing in the 0.1 mM to 5.0 mM range while 58 μA/(cm2.mM) is observed in the 5.0 to 40 mM range. Potentiometric urea sensor with urease entrapped PPy microstructures on SS electrode is developed. It is able to sense urea in the micromolar ranges down to 0.1 μM. It represented an excellent performance with sensitivity of 27 mV/decade. Sensitivity in the micromolar range is 4.9 mV/(μM.cm2). Drug encapsulation and delivery is successfully demonstrated by two actuation means (i) by electrochemical actuation, (ii) by actuation based on pH changes. Concepts are proved by delivering a fluorescent dye into neutral and acidic solutions. Drug delivery is confirmed by UV-Visible spectroscopy and Fluorescence microscopy. Finally, Micro/nanostructures with Tangerine, Hollow globular (Pani Poori), Chip, Flake, Rose, Worm, Horn and Celia shapes are synthesized electrochemically and scanning electron microscopic studies are presented. 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