Browsing by Subject "water vapor"
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Item Measurement of Water Vapor Concentration using Tunable Diode Laser Absorption Spectroscopy(2010-07-14) Barrett, Alexander B.Tunable diode laser spectroscopy and the Beer-Lambert relation has been used to measure the absorption of water vapor both in an absorption cell and in a shock tube. The purpose of this thesis is to develop a laser diagnostic capable of determining species concentration. The correlation between species concentration and absorption is known, and if one is known the other can be calculated. A diode laser was obtained which has a tunable range of 1325.7 - 1400.8 nm and is centered at 1384 nm. An experimental setup was created in which the laser was used to obtain absorption spectroscopy data for water vapor within two separate scenarios- in an absorption cell and in a shock tube. A model was constructed which enabled the calculation of the Voigt profile which in turn was used to determine the absorption coefficient and ultimately enable the utilization of absorption spectroscopy principles to determine species concentration and/or absorption percentage. The experiments for the absorption cell were performed at room temperature. Twenty runs were performed and the average error for all runs was less than one percent. Three runs were performed for the shock-tube experiments. The absorption was calculated at three times- prior to the arrival of the shock, after the incident shock passed, and after the reflected shock passed. The temperatures for these conditions were 296K, 1060K, and 2000K respectively. These experiments showed reasonable agreement with theoretical calculations.Item Trajectory Simulations of H2O, O3, and CO in the Upper Troposphere and Lower Stratosphere (UTLS)(2014-05-05) Wang, TaoThe purpose of this work is to simulate water vapor (H2O), ozone (O3), and carbon monoxide (CO) in the upper troposphere and lower stratosphere (UTLS) using a domain-filling, forward trajectory model. The influx of H2O to the UTLS is largely determined by the large-scale troposphere-to-stratosphere transport in the tropics, during which air is dehydrated across the cold tropical tropopause. In the domain-filling, forward trajectory model, trajectories are initialized in the upper troposphere, and the circulation is based on reanalysis wind fields. Along the trajectories, winds determine the pathways of parcels and temperature determines the H2O content through an idealized saturation calculation. Compared with the Aura Microwave Limb Sounder (MLS) measurements, this simple advection-condensation strategy yields reasonable results for H2O in the stratosphere in terms of both seasonal variability and vertical structures. The detailed global dehydration patterns are also revealed from this model and it improves our understanding of the H2O and its transport within the UTLS. Besides H2O, ozone (O3) and carbon monoxide (CO) are also important trace gases in the UTLS linked to circulation, transport and climate forcing (for O3). Combined with simple parameterization of chemical production and loss rates from the Whole Atmosphere Community Climate Model (WACCM), we also managed to simulate O3 and CO transport in the UTLS via this trajectory model. The trajectory modeled O3 and CO show good overall agreement with satellite observations from the MLS and the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) in terms of spatial structure and seasonal variability. The trajectory model results also agree well with the Eulerian WACCM simulations. Analysis of the simulated tracers shows that seasonal variations in tropical upwelling exerts strong influence on O3 and CO in the tropical lower stratosphere, and the coupled seasonal cycles provide a useful test of the transport simulations. Interannual variations in the tracers are also closely coupled to changes in upwelling, and the trajectory model can accurately capture and explain observed changes. This demonstrates the importance of variability in tropical upwelling in forcing chemical changes in the tropical UTLS. Trajectory modeling of O3 and CO can provide useful tests for simplified understanding of transport and chemical processes in the UTLS, and provide complementary information to the H2O simulations, which are primarily constrained by tropopause temperatures. This model is easy to use, easy to diagnose, and the Lagrangian perspective makes it exceptionally useful in studying transport processes within the UTLS.